Sibling conflict and theory of mind

45

https://www.wendangku.net/doc/bc19068827.html,

Sibling conflict and theory of mind

Rachel C.Foote1and Heather A.Holmes-Lonergan2*

1Hammond Developmental Center,USA

2The Metropolitan State College of Denver,USA

This study examined conflicts between siblings in an attempt to identify variables that

are related to false-belief understanding.The variables investigated were children’s use

of mental state terms and specific types of arguments(Slomkowski&Dunn,1992)that

occurred during conflict episodes.Twenty-two children between3and5years of age

were administered eight false-belief tasks and were also videotaped while playing with

an older https://www.wendangku.net/doc/bc19068827.html,e of other-oriented arguments by the target child was significantly

associated with success on false-belief tasks after controlling for age and general

language ability.No use of argument was negatively related to performance on the

false-belief tasks after controlling for age and general language ability.Neither the use

of self-oriented arguments nor use of mental state terms was found to be associated

with false-belief performance.The findings indicate that specific features of sibling

conflicts are related to children’s developing false-belief understanding.

Since its inception,theory of mind research has been concerned with delineating the progress of children’s understanding of the mind and with possible theoretical explanations for their developing folk psychology.Much of this research and theory-building has taken a rather Piagetian approach by focusing on the child’s role in acquiring knowledge about the mind.Less attention has been paid to the kinds of social experiences that might help mould the child’s theory of mind.Recently,however, Nelson,Plesa,and Henseler(1998)have proposed an experiential approach to theory of mind development.The experiential view states that the child’s theory of mind develops as a result of the interaction between the internal processes of the child and environmental influences acting upon the child.Children construct their knowledge about the mind based on events that take place in their environments and also based on their reasoning about those events.Although the relationships between social interactions and theory of mind development have only recently been examined, researchers have explored various aspects of the child’s cultural background(Vinden, *Requests for reprints should be addressed to Dr Heather A.Holmes-Lonergan,Department of Psychology,The Metropolitan

State College of Denver,Campus Box54,PO Box173362,Denver,CO80217–3362,USA(e-mail:holmeslo@https://www.wendangku.net/doc/bc19068827.html,).

46Rachel C.Foote and Heather A.Holmes-Lonergan

1997;Wahi&Johri,1994),family background(Cole&Mitchell,1998;Cutting&Dunn, 1999),and peer relationships(Dunn&Cutting,1999;Slomkowski&Dunn,1996).

The present research focuses on sibling relationships and their connection to the development of a theory of mind.In this area,two kinds of research have been conducted—studies that examine the number of siblings a child has,and studies that examine characteristics of the sibling relationship itself.Several studies have shown that false-belief performance is related to both the number of siblings that children have and to the ages of those siblings.Research has indicated that children with more siblings perform better on false-belief tasks than children with fewer siblings(Jenkins& Astington,1996;Perner,Ruffman,&Leekam,1994),and that the number of older(but not younger)siblings is correlated with children’s false-belief performance(Lewis, Freeman,Kyriakidou,Maridaki-Kassotaki,&Berridge,1996;Ruffman,Perner,Naito, Parkin,&Clements,1998).

It has been argued that it is within the context of sibling relationships that children have their most intense social experiences(Dunn,1985;Perner et al.,1994).In particular,siblings are potential sources of influence on sociocognitive abilities such as perspective taking,reflection about internal states,and developing an understanding of how the mind works and how it influences behaviour(Boer&Dunn,1992).Research using naturalistic observation has revealed particular features of sibling interactions that are related to sociocognitive development.Dunn,Brown,Slomkowski,Tesla,and Youngblade(1991)found that the degree of children’s cooperative interaction with their siblings was related to their performance on various sociocognitive tasks7months later.Brown,Donelan-McCall,and Dunn(1996)examined children’s use of mental state terms during unstructured interactions at home with friends,siblings,and mothers. Children made significantly more references to mental states during conversations with siblings or friends than during conversations with mothers.Further,children’s use of mental state terms in conversations with siblings and friends was correlated with their performance on measures of false belief.

The two studies just discussed focused on cooperative sibling interactions.The present research differed from previous research by investigating sibling conflicts and their relationship to false-belief understanding.Dunn and Slomkowski(1992)have stated that sibling conflicts may represent an especially powerful stimulus for the growth of children’s social knowledge.They argue that sibling conflicts involve a combination of self-interest,emotional arousal,and a close relationship that has particular significance.Children are therefore strongly motivated to pay attention to the reactions,perspectives,feelings,and beliefs of their siblings when conflicts occur (Dunn&Slomkowski,1992).Through conflict,children learn to negotiate, compromise,persuade,and take turns(Katz,Kramer,&Gottman,1992).Children learn that others may have opinions,feelings,and intentions that differ from their own, and with which they may choose to agree or disagree.In addition,siblings who engage in constructive conflicts,in which children attempt to reconcile their differing points of view,are more likely to display cooperative and conciliative behaviour,while siblings who engage in destructive conflicts are more likely to be hostile and aggressive(Vandell &Bailey,1992).

Although certain kinds of sibling conflict may relate to the development of children’s knowledge about the mind,little is known about the particular variables within sibling disputes that might facilitate such development.In this study,two variables were measured.The first was children’s use of mental state terms.As discussed,it has been demonstrated that children’s overall use of mental state terms during sibling

interactions is related to their understanding of false belief (Brown et al.,1996).The present research differed from past research by first isolating conflict episodes,and then measuring children’s use of mental state terms within those episodes.It was hypothesized that the use of mental state terms by a child during conflict episodes with a sibling would be correlated with his or her false-belief performance.

It has been argued that the frequency of mental state term use simply reflects individual differences in children’s language ability (Bloom,Rispoli,Gartner,&Hafitz,1989).In addition,children’s performance on false-belief tasks has been shown to be highly related to language development (see Astington &Jenkins,1999,for a discussion of this issue).Further,Jenkins and Astington (1996)found that the relationship between number of siblings and false-belief understanding was dependent upon children’s language ability.Because the present study examined mental state term use during verbal conflict episodes between siblings,general language ability was controlled.

The second variable studied was children’s use of arguments that occurred during sibling conflicts.Slomkowski and Dunn (1992),as well as Dunn,Slomkowski,Donelan,and Herrera (1995),reported that children’s use of arguments with siblings was predictive of their performance on an affective perspective-taking task 7months later.Slomkowski and Dunn examined three types of arguments:other-oriented,self-oriented,and no argument.Other-oriented arguments involve negotiation or reasoning that incorporates either the partner’s interests or the interests of both children.Self-oriented arguments are excuses or reasons that are geared toward the speaker’s interests alone.No argument is a conversational turn in which the child does not offer any sort of justification,reasoning,excuse,or conciliation.

In the present research,these three types of arguments were measured in relation to false-belief understanding,rather than to affective perspective taking.In addition,the siblings in the present study interacted alone,without the presence of the mother (mothers were often present during sibling interactions in Slomkowski and Dunn’s,1992,research,and the presence of the mother was not controlled).It was hypothesized that children’s use of other-oriented and self-oriented arguments during conflicts with siblings would be positively related to their performance on false-belief tasks.Children’s lack of arguments was hypothesized to be negatively correlated with false-belief https://www.wendangku.net/doc/bc19068827.html,nguage ability was controlled for these variables as well.This study also differed from past research on sibling interactions and sociocognitive development by using a more structured and controlled observational procedure.In previous research (e.g.Brown et al.,1996;Slomkowski &Dunn,1992),naturalistic observations were conducted in each child’s home.In the present study,the target child and his/her sibling were observed in a laboratory room designed as a playroom.All interaction sessions therefore took place at the same location and all children were observed for the same length of time.In addition,this study isolated the interaction between the child and his or her sibling;the two children played alone,without the caregiver present.

Each target child in this study was the younger child of the sibling pair.As stated,the presence of older siblings seems to be more highly related to the child’s understanding of false belief than the presence of younger siblings (Lewis et al.,1996;Ruffman et al.,1998).It has also been argued that interactions with older,more linguistically advanced siblings are more likely to facilitate more sophisticated expression of language (such as mental states)than are interactions with younger,less linguistically developed siblings (Ruffman et al.,1998).

47

Sibling conflict and theory of mind

48Rachel C.Foote and Heather A.Holmes-Lonergan

False-belief tasks involving both prediction and explanation of another’s belief were used in this study.Bartsch and Wellman(1989)have suggested that many young children(3-year-olds in particular)tend to weight desire more heavily than belief in predicting a story character’s actions on a false-belief task.When explanation tasks are used,the tendency to reason based on desire satisfaction is reduced,and children are more likely to reason about the character’s actions in terms of beliefs.Other studies involving children’s interactions with siblings have also adopted Bartsch and Wellman’s procedure(Dunn et al.,1991;Slomkowski&Dunn,1996;Youngblade&Dunn,1995). It was anticipated that children would perform better on the explanation tasks than on the prediction tasks.

Method

Participants

Twenty-two children between the ages of3years0months and5years8months(M= 51.8,SD=9.9)participated.Most of the children(N=18)were recruited from several day-care centres in south-eastern Louisiana on the basis of parent permission letters. The remaining children(N=4)were acquaintances of the first author.Thirteen children were male,and nine were female.All of the children were Caucasian and were from primarily working-and middle-class families.Ten children participated with an older brother,and12participated with an older sister.Nine of the sibling pairs were girl–girl,six were boy–boy,and seven were boy–girl.All families received a gift certificate to a local discount retailer as compensation for their participation. Procedure

Each child was given the Test of Early Language Development-3(TELD-3;Hresko,Reid, &Hammill,1999)as a control for general language ability.In a separate session,each child was administered eight false-belief tasks.The order of these two sessions was counterbalanced.

The target child and his or her sibling were also brought to a laboratory room set up as a playroom.The room was equipped with three sets of toys:a Winnie the Pooh Safari game,a Fisher-Price farm,and building blocks.The children were asked to choose one of these toys,and were told they should play together while the tester met with the caregiver in an adjoining room.Each dyad was videotaped for15minutes using a camera mounted near the ceiling.After15minutes had passed,the tester and caregiver returned to the room and the play session was ended.For those children recruited from the child-care centres,all testing sessions preceded the play sessions.Children recruited through personal contact participated in the testing and the play sessions in one visit to the laboratory The order of their participation was as follows:(1)general language test or the false-belief tasks,(2)play session,(3)remaining test or tasks.

Measures

Test of Early Language Development-3(1999)

The TELD-3was used to assess the children’s general language development.Both expressive and receptive forms of syntactic and semantic abilities are assessed through

responses to questions and pictures.This test has been standardized on children between the ages of 3and 7years (Hresko et al.,1999).Raw scores from the TELD-3were used in all analyses.

False-belief tasks

Eight different false-belief tasks were administered.The tasks required the children to predict how one of two figures would behave,given a false belief,or to give an explanation of the figure’s behaviour,given a false belief (Youngblade &Dunn,1995).The procedures were similar to those used by Bartsch and Wellman (1989).Each child was shown two closed boxes for each task.One was marked with a familiar picture,and the other was a plain unmarked box of the same size.Four types of marked boxes were used:a Band-Aid box,a crayon box,a Play-Doh box,and a raisin box.Each unmarked box was of the same dimensions as the marked box with which it was paired.Each pair of boxes was introduced immediately prior to its use,and the order of presentation of the four pairs of boxes was counterbalanced.For each pair,the child was asked to choose the box that contained the expected items.Next,the child was asked to look inside the container in order to see that it was empty.The child was then asked to look inside the unmarked box,which did contain the expected items.

The child was then introduced to the first toy figure (either Tigger or Winnie the Pooh)and given either a prediction or an explanation task question.After the child answered that question,the second toy figure was then introduced and the alternative question was asked.Prediction and explanation questions were counterbalanced for order of presentation,with half of the children receiving a prediction task first for each pair of boxes,and the other half receiving an explanation task first.The two tasks were administered consecutively for each pair of boxes.In the prediction tasks,the child was asked where the toy figure would look for the expected items.The toy figure was then made to move in the predicted direction and the child was asked if the figure would find the expected items.In the explanation tasks,the examiner moved the toy figure toward the marked but empty container.The child was then asked to explain the figure’s action.If a false belief was mentioned,the child was asked if the items were really in the box (as a memory check).If no response was made or no belief explanation was mentioned,then the examiner prompted the child by asking what the toy figure thought.

Scoring

False-belief tasks

For each of the eight tasks,the child was given a score of 0(fail)or 1(pass)for a total of 8possible points.On each of the four prediction tasks,children’s responses predicting that the figure would search in the marked but empty box were scored as passing and responses predicting that the figure would search in the unmarked but full box were scored as failing.On the four explanation tasks,children who gave one or more explanations of the toy figure’s action in terms of the figure’s false belief (prompted or unprompted)were scored as passing.Children who gave no explanation for the figure’s action were scored as failing.

Conflict coding

Slomkowski and Dunn’s (1992)procedure for defining and scoring conflict was 49

Sibling conflict and theory of mind

50Rachel C.Foote and Heather A.Holmes-Lonergan

followed.Conflict was defined as an interaction which follows an opposition to an action,a request for action,or an assertion.A request for action may be one child asking his or her sibling for a toy by saying,‘Would you gimme that doll?’The sibling’s verbal refusal to give the child the toy would be an opposition;e.g.,‘No,I don’t wanna.’A conflict episode was scored if it included at least one verbal exchange.An exchange was defined as one utterance spoken by each participant.All interaction following the initial opposition was recorded until:(1)an obvious settlement was reached;(2)one child left the scene of the interaction and was not pursued;or(3)the discourse topic was altered and not resumed for a period of1minute.

Mental state talk

The conversations of the children with their siblings during conflict were analyzed for the use of mental state terms by the target child.A mental state term was defined as a term that referred to the thoughts,memories,or knowledge of the speaker,listener,or a third person.The terms coded included those reported in earlier studies of children’s mental state discourse(Brown et al.,1996;Shatz,Wellman,&Silber,1983)and appear in Appendix A.Expressions of desire such as‘hope’or‘wish’or emotion terms such as ‘happy’or‘sad’were not included in the coding.For the purpose of analysis,the frequency of mental state terms used in conflict was represented as a proportion of the target child’s total speaking turns.This transformation reflected the relative use of mental state terms,and also controlled for differences in the amount of talk across dyads.

Type of argument

Each speaker turn by the target child contributing to a conflict episode was scored as one of three mutually exclusive categories:other-oriented argument,self-oriented argument,and no use of argument.Other-oriented arguments were defined as conversational turns that take into account the partner’s interests and may include compromise,conciliation,bargaining or agreement.Self-oriented arguments were defined as conversational turns that involve giving a reason or justification for the disagreement solely in defence of one’s own position or interest.No use of argument was defined as conversational turns in a conflict in which the speaker fails to argue, justify,or provide an excuse.Appendix B presents examples of each category.In the unlikely event that more than one type of argument was used in a turn,only one type of argument was coded using the following procedure:other-oriented arguments were given first priority,and self-oriented arguments were given second priority(Slomkowski &Dunn,1992).In the analyses,each category of argument turns was,like mental state term use,represented as a proportion of the target child’s total speaking turns.

Inter-rater reliability

Correlations were computed to assess inter-rater reliability for mental state terms and argument type.Twelve of the22pairs of siblings were coded by two independent raters.All correlations were of an acceptable level:mental state term use(r=.96,p= .0001),no use of arguments(r=.85,p=.001),self-oriented arguments(r=.61,p= .03),and other-oriented arguments(r=.87,p=.0001).

Results

Descriptive statistics

Descriptive statistics are presented in Table 1.Descriptive data summarizing children’s performance on the false-belief tasks were also computed.The results revealed that 27%of the total sample passed all eight false-belief tasks,4%passed seven tasks,14%passed six tasks,9%passed five tasks,14%passed four tasks,14%passed two tasks,4%passed one task,and 14%did not pass any tasks.Before submitting the data to hypothesis testing,a correlation matrix was computed for all variables analysed and is presented in Table 2.

Hypothesis 1

The data were submitted to a multiple regression analysis to determine whether children’s use of mental state terms during conflict predicted false-belief understanding.False-belief understanding was regressed onto:(a)age in months,(b)general

language Table 1.Means and standard deviations for age in months,age difference between siblings in months TELD-3scores,false-belief scores,proportion of mental state terms,proportion of no arguments,proportion of self-oriented arguments,proportion of other-oriented arguments,proportion of conflict turns in total speaker turns and total speaker turns (N =22)

Table 2.Correlation matrix for age in months.TELD-3scores,mental state terms,no arguments,self-oriented arguments,other-oriented arguments,and false-belief scores (N =22).45*.09.43.12.23.48*.67***p <.05;**p <.01.

51

Sibling conflict and theory of mind

ability,and (c)proportion of mental state terms used in conflict per total speaking turns during the conflict.The overall model was statistically significant,F (3,18)=7.93,r =.569,p =.001,as was the main effect for language ability (see Table 3).The analysis revealed no significant main effect for the use of mental state terms.Because this finding failed to support predictions,the data were examined further to try to determine the reason for the nonsignificant results.Examination of the data revealed that the use of mental state terms during conflict episodes occurred infrequently and was skewed in nature.A stem and leaf plot for the use of mental state terms and additional descriptive statistics are presented in Appendix C.

Hypothesis 2

The next analyses were conducted to investigate the relationships between the three types of arguments and false-belief scores.The data were submitted to three separate multiple regression analyses to determine whether children’s use of particular types of arguments during conflicts were related to their false-belief understanding.In the first analysis,false-belief scores were regressed onto:(a)age in months,(b)general language ability,and (c)proportion of total speaking turns where no arguments were used.Results are presented in Table 4.The overall model was statistically significant,F (3,18)=12.34,r =.673,p =.0001.As predicted,there was also a significant main effect for no use of arguments (see Table 4).

The second and third analyses repeated the same procedure for self-oriented and other-oriented arguments.For self-oriented arguments,the overall model was significant,F (3,18)=8.061,r =.573,p =.001,as was the main effect for language ability (see Table 5).However,the hypothesized main effect for use of self-oriented arguments was not significant.For other-oriented arguments,the overall model was also significant,F (3,18)=11.44,r =.656,p =.0001.As predicted,there was also a significant main effect for use of other-oriented arguments (see Table 6).These results indicate that,as predicted,there is a positive relationship between the use of other-oriented arguments and false-belief understanding and a negative relationship between no use of arguments and false-belief understanding.

Hypothesis 3

A two-sample dependent t test was conducted to examine whether children performed differently on prediction versus explanation versions of the false-belief tasks as expected.No significant difference was found between children’s performance on the two versions of the

tasks.

Table 3.Results of the regression analysis for mental state term use and false-belief scores (N =22)*p <.05.a Values represent F (3,18).52Rachel C.Foote and Heather A.Holmes-Lonergan

Discussion

The goal of the present research was to identify variables within the context of sibling disputes that are associated with false-belief understanding.It was hypothesized that children’s use of mental state terms and arguments that occurred during sibling conflicts would relate to their performance on false-belief tasks.The first hypothesis,that children’s use of mental state terms during sibling conflict episodes would be correlated with their false-belief scores,was not supported.Although previous research has demonstrated such a relationship (Brown et al.,1996),the extremely infrequent occurrence of mental state terms in this study prevents any meaningful interpretation of the results.Brown et al.(1996)reported a mean of only 5.1mental state turns per hour of conversation with sibling.Children in this study were only observed for 15minutes and the coding was restricted to conflict episodes,limiting the possibility that relations between mental state terms and false-belief performance would be found.Given the constraints of this study,it would be important in future research to lengthen the time that children are observed to allow for the development of more conflict.It might also Table 4.Results of the regression analysis for no use of arguments and false-belief scores (N =22)

.43*p <.05.a Values represent F (3,18).Table 5.Results of the regression analysis for self-oriented arguments and false-belief scores (N =22)

*p <.05.a Values represent F (3,18).Table 6.Results of the regression analysis for other-oriented arguments and false-belief scores (N =22)

*p <.05.a Values represent F (3,18).53

Sibling conflict and theory of mind

54Rachel C.Foote and Heather A.Holmes-Lonergan

be useful to observe children in various contexts(naturalistic as well as laboratory), and/or to use alternative measurements,such as parent or teacher reports of mental state term use.

The second hypothesis involved the relationships between children’s use of arguments during sibling conflict and their false-belief understanding.As predicted, participants who used a higher proportion of other-oriented arguments scored higher on the false-belief tasks.Also as hypothesized,participants who used a higher proportion of no arguments during conflict scored lower on the false-belief tasks.These results are consistent with Slomkowski and Dunn’s(1992)findings that children’s use of arguments with siblings is related to their sociocognitive performance.This study also provides new support for the relationship between arguments that occur during sibling conflicts and children’s false-belief understanding.

Specifically,this study demonstrated that when a child fails to use arguments,he or she is also failing to demonstrate examples of more advanced sociocognitive development such as negotiating,compromising,persuading or taking turns.No use of arguments was related to less successful performance on false-belief tasks. Conversely,a child who uses an argument that takes into account the interests of his or her sibling is demonstrating an understanding of the sibling’s perspective.These other-oriented arguments were related to better performance on false-belief tasks.The results of this study indicate that there are specific features of sibling conflicts that are associated with children’s performance on false-belief tasks,which assess the ability to understand another person’s mental states and their relationships to behaviour.Nelson et al.(1998)proposed that children’s social relationships influence(and are influenced by)their understanding of other minds.The present findings appear to support this theoretical view.

Contrary to hypotheses,use of self-oriented arguments was not related to false-belief understanding.This study failed to replicate Slomkowski and Dunn’s(1992)finding that use of self-oriented arguments influences sociocognitive performance.One possible explanation is that the acquisition of theory of mind knowledge is a gradual process and the use of self-oriented arguments may be part of an intermediate phase of its development.As Dunn and Munn(1987)point out,arguments between children who are of approximately equal status and who share close interests may play a role in children’s moves from egocentrism to recognition of the perspectives of others.The three argument types appear to mirror this transition in perspectives.No arguments is the most egocentric type of argument because it consists of simple assertions and expressions of desire by the child.Self-oriented arguments are less egocentric,as the child now recognizes the need to express his or her perspective to a second party. Other-oriented arguments are the most advanced of the argument types,as they indicate a recognition of others’perspectives.Of the seven children who passed between0and2of the false-belief tasks,five used no arguments more often than self-oriented or other-oriented arguments.Three of the five children who passed between3 and5tasks used self-oriented arguments more often than no or other-oriented arguments.Six of the10children who passed between6and8tasks used other-oriented arguments more often than no or self-oriented arguments.The negative correlation between no use of arguments and use of other-oriented arguments also supports the idea that these two types of arguments are perhaps opposite ends of a continuum.Finally,there was no significant difference between children’s performance on the explanation and prediction versions of the false-belief tasks,indicating that one type of task was not more difficult than the other.Yet60%of the children neither

passed all of the tasks nor failed all of them.It appears that as children begin to develop a theory of mind,they are variable in their performance instead of uniformly successful.Several cautions should be noted here.First,the small sample size of this study limits conclusive interpretations of the data.Replication with larger sample sizes is necessary.In addition,this study did not include other variables that might mediate the relationships discussed here.For example,the arguments received by the target child from the sibling would be important to measure in addition to the arguments used by the target child.Interactions between the target child and more than one sibling at a time might also yield different patterns of data than those reported here.Interactions with the target child and an older versus a younger sibling might also be compared.Finally,the correlational nature of the data should be emphasized.Obviously,it may not be that experiences in conflict with a sibling lead to more or less successful performance on false-belief tasks.It could well be that those individuals who performed poorly on the false-belief measures were more likely to use unreasoned argument in conflict because of their more limited sociocognitive abilities.Likewise,it could be that those individuals who performed well on the false-belief measures were more likely to use other-oriented arguments in conflict because of their more advanced sociocognitive abilities.However,Slomkowski and Dunn (1992)examined both child–sibling and child–mother interactions and found significant correlations only for child’s arguments with a sibling,and not with mother.Future research on the relationship between children’s arguments with siblings and false-belief understanding might consider including a child–mother observation in an attempt to replicate these findings.Also,longitudinal research that examines both sociocognitive abilities and social interactions would help clarify the connections between the two in the course of development.Future research may also include tasks that measure children’s emotional or affective knowledge in addition to tasks that measure knowledge about false beliefs (e.g.Dunn et al.,1995;Slomkowski &Dunn,1992).

In summary,this research has identified for the first time specific variables within the context of sibling disputes that were related to children’s false-belief understanding.This research supports and extends the findings of Slomkowski and Dunn (1992)and indicates that the use of no arguments and other-oriented arguments during conflicts with siblings is correlated with false-belief understanding,in addition to affective perspective taking.In this study,there were relationships between the degree of false-belief understanding displayed by the children and the kinds of arguments they used during sibling disputes.Although very limited,the present findings may suggest that children’s developing false-belief knowledge may be linked along a continuum with their ability to use certain kinds of arguments during disputes with siblings.This is consistent with the view that siblings who engage in constructive conflicts,which involve attempts to take the other’s perspective and to cooperate,are more likely to display advances in their sociocognitive understanding (Vandell &Bailey,1992).More generally,this research also reinforces the experiential viewpoint which contends that the social interactions in which a child engages are an important source of theory of mind knowledge;knowledge that may then be used to develop mental concepts (Nelson et al.,1998).According to this viewpoint,advances in the development of a theory of mind might then in turn be related to children’s social relationships,so that progress in one aspect of development might facilitate change in the other.Future research should continue to focus on the interaction between the child and the child’s environment in exploring the development of theory of mind knowledge.

55

Sibling conflict and theory of mind

56Rachel C.Foote and Heather A.Holmes-Lonergan

Acknowledgements

These data were collected while both authors were at Southeastern Louisiana University.This research was submitted in partial fulfilment of the requirements for the Master’s degree in psychology at Southeastern Louisiana University for Rachel C.Foote.Portions of this research were presented at the biennial conference on Human Development,April,2000,Memphis,USA. The authors would very much like to thank Victor L.Bissonnette,Scott https://www.wendangku.net/doc/bc19068827.html,ler,Matthew J. Rossano,and two anonymous reviewers for their very helpful comments on earlier versions of this manuscript.The authors would also like to thank the staff,parents,and especially the children from the following preschools and day-care centres:First United Methodist Church, Harvest Christian Academy,Little Oaks,Loranger Elementary,Southeastern Louisiana University Laboratory School,and University Montessori School.

References

Astington,J.W.,&Jenkins,J.M.(1999).A longitudinal study of the relation between language and theory-of-mind development.Developmental Psychology,35,1311–1320.

Bartsch,K.,&Wellman,H.(1989).Young children’s attribution of action to beliefs and desires.

Child Development,60,946–964.

Bloom,L.,Rispoli,M.,Gartner,B.,&Hafitz,J.(1989).Acquisition of complementation.Journal of Child Language,16,101–120.

Boer,F.,&Dunn,J.(1992).Children’s sibling relationships:Developmental and clinical issues.

Hillsdale,NJ:Erlbaum.

Brown,J.R.,Donelan-McCall,N.,&Dunn,J.(1996).Why talk about mental states?The significance of children’s conversations with friends,siblings,and mothers.Child Develop-ment,67,836–849.

Cole,K.,&Mitchell,P.(1998).Family background in relation to deceptive ability and understanding of the mind.Social Development,7,181–195.

Cutting,A.L.,&Dunn,J.(1999).Theory of mind,emotion understanding,and family background: Individual differences and interrelations.Child Development,70,853–865.

Dunn,J.(1985).Sisters and brothers.Cambridge,MA:Harvard University Press.

Dunn,J.,Brown,J.,Slomkowski, C.,Tesla, C.,&Younglade,L.(1991).Young children’s understanding of other people’s feelings and beliefs:Individual differences and their antecedents.Child Development,62,1352–1366.

Dunn,J.,&Cutting,A.L.(1999).Understanding others,and individual differences in friendship interactions in young children.Social Development,7,201–219.

Dunn,J.,&Munn,P.(1987).Development of justification in disputes with mother and sibling.

Developmental Psychology,23,791–798.

Dunn,J.,&Slomkowski,C.(1992).Conflict and the development of social understanding.In C.U.

Shantz&W.W.Hartup(Eds.),Conflict in child and adolescent development(pp.70–92).

Cambridge:Cambridge University Press.

Dunn,J.,Slomkowski, C.,Donelan,N.,&Herrera, C.(1995).Conflict,understanding,and relationships:Developments and differences in the preschool years.Early Education and Development,6,303–316.

Hresko,W.P.,Reid,D.K.,&Hammill,D.D.(1999).The Test of Early Language Development-3 (TELD-3).Austin,TX:Pro-Ed.

Jenkins,J.M.,&Astington,J.W.(1996).Cognitive factors and family structure associated with theory of mind development in young children.Developmental Psychology,32,70–78. Katz,L.F.,Kramer,L.,&Gottman,J.M.(1992).Conflict and emotions in marital,sibling,and peer relationships.In C.U.Shantz&W.W.Hartup(Eds.),Conflict in child and adolescent development(pp.122–149).Cambridge:Cambridge University Press.

Lewis,C.,Freeman,N.,Kyriakidou,C.,Maridaki-Kassotaki,K.,&Berridge,D.(1996).Social influences on false belief access:Specific sibling influences or general apprenticeship?Child Development,67,2930–2947.

Nelson,K.,Plesa, D.,&Henseler,S.(1998).Children’s theory of mind:An experiential interpretation.Human Development,41,7–29.

Perner,J.(1991).Understanding the representational mind .Cambridge,MA:MIT Press.

Perner,J.,Ruffman,T.,&Leekam,S.R.(1994).Theory of mind is contagious:You catch it from your sibs.Child Development,65,1228–1238.

Ruffman,T.,Perner,J.,Naito,M.,Parkin,L.,&Clements,W.A.(1998).Older (but not younger)siblings facilitate false belief understanding.Developmental Psychology,34,161–174.

Shatz,M.,Wellman,H.M.,&Silber,S.(1983).The acquisition of mental verbs:A systematic investigation of first references to mental state.Cognition,14,301–321.

Slomkowski,C.L.,&Dunn,J.(1992).Arguments and relationships within the family:Differences in young children’s disputes with mother and sibling.Developmental Psychology,28,919–924.

Slomkowski,C.,&Dunn,J.(1996).Young children’s understanding of other people’s beliefs and feelings and their connected communication with friends.Developmental Psychology,32,442–447.

Vandell,D.L.,&Bailey,M.D.(1992).Conflicts between siblings.In C.U.Shantz &W.W.Hartup (Eds.),Conflict in child and adolescent development (pp.242–269).Cambridge:Cambridge University Press.

Vinden,P.(1997,April).The effects of parenting style on theory of mind understanding .Paper presented at the biennial meeting of the Society for Research in Child Development,Washington,DC.

Wahi,S.,&Johri,R.(1994).Questioning a universal theory of mind:Mental-real distinctions made by Indian children.Journal of Genetic Psychology,155,503–510.

Youngblade,L.M.,&Dunn,J.(1995).Individual differences in young children’s pretend play with mother and sibling:Links to relationships and understanding of other people’s feelings and beliefs.Child Development,66,1472–1492.

Received 26June 2000;revised version received 21June 2002

Appendix A:Mental state terms

Verbs:know,think,mean,forget,remember,guess,pretend,dream,bet,trick,

wonder,figure,believe,understand,suppose,learn,doubt,lie,confuse,

have in mind,surprise,realize

Nouns:idea,dream,trick,secret

Adjectives:

pretend,curious,real Appendix B:Examples of argument coding

No argument

1.

‘Give it to me.’2.‘I want that.’

Self-oriented argument

1.

‘I need the blue block for my laser.’2.‘I chose the horse first.’

57

Sibling conflict and theory of mind

58Rachel C.Foote and Heather A.Holmes-Lonergan

Other-oriented argument

1.‘I’ll give you all these(building blocks)if you give me that one(a block with

wheels on it.’

2.‘She said we have to play together.Let’s finish the building,then we’ll play with

that.’

Appendix C:Stem and leaf plot for proportional use of mental state terms

Mean:0.014

Standard deviation:0.037

Skewness: 2.617

Kurtosis: 5.816

Stem Leaves

木聚糖酶及其应用

木聚糖酶及其应用 姓名：程婷婷学号：20083768 班级：食品科学与工程专业08级本科2班摘要：木聚糖是一种多聚五碳糖，是植物半纤维素的主要成分，是仅次于纤维素的第二丰富的可再生资源。木聚糖木聚糖结构复杂，完全降解需要多种酶的参与，其中β-1，4-内切木聚糖酶能够以内切方式作用于木聚糖主链产生不同长度的木寡糖和少量的木糖，是木聚糖降解酶系中最关键的酶。木聚糖酶是可将木聚糖降解成低聚木糖和木糖的水解酶,在食品、制浆造纸、饲料等行业上有着广阔的应用前景.本文主要从木聚糖酶的分类、特性及其应用等方面进行阐述。 关键词：木聚糖酶；分类；特性；应用 木聚糖是以木吡喃糖为单位的由β-1， 4键连接的半纤维素，富含于阔叶树和大多数一年生植物体内，是一种重要的可再生资源，仅次于纤维素。它多为异聚多糖，结构变化范围很大，从β-1，4糖苷键相连接的多聚木糖线性分子到高度分枝的异质多糖。目前，木聚糖酶主要由微生物生产，已报道能生产木聚糖酶的微生物有丝状真菌、细菌和链霉菌等。微生物产生的木聚糖酶具有多样性，即常常产生不止一种类型的木聚糖酶，而且这些木聚糖酶的特性也存在差异。木聚糖酶可广泛应用于食品、制浆造纸、饲料等行业。 1木聚糖酶的分类 1.1木聚糖酶 木聚糖酶是指能够降解半纤维素木聚糖的一组酶的总称，主要包括三类:内切-β-1,4一木聚糖酶，作用于木聚糖和长链木寡糖，从β-1,4一木聚糖主链的内部切割木糖苷链，从而使木聚糖降解为木寡糖，其水解产物主要为木二糖与木二糖以上的寡聚木糖，也有少量的木糖和阿拉伯糖;外切-β-1,4一木聚糖酶，作用于木聚糖和木寡糖的非还原端，产物为木糖; β-木糖苷酶,该酶通过切割木寡糖末端而释放木糖残基[1]。 1.2根据所水解的木聚糖苷键类型 木聚糖酶可分为β-1,4糖苷键木聚糖酶和β-1,3糖苷键木聚糖酶两类。陆上植物的木聚糖酶均属β-1,4糖苷键木聚糖酶，而β-1,3糖苷键木聚糖酶大都

第九章_细胞骨架习题及答案

第九章细胞骨架 本章要点：本章阐述了细胞骨架的基本涵义、细胞中存在的几种骨架体系的结构、功能及生物学意义。要求重点掌握细胞质骨架的结构及功能。 一、名词解释 1、细胞骨架：细胞骨架(Cytoskeleton)是指存在于真核细胞质内的中的蛋白纤维网架体系。包括狭义和广义的细胞骨架两种概念。广义的细胞骨架包括：细胞核骨架、细胞质骨架、细胞膜骨架和细胞外基质。狭义的细胞骨架指细胞质骨架，包括微丝、微管和中间纤维。 2、应力纤维：应力纤维是真核细胞中广泛存在的微丝束结构，由大量平行排列的微丝组成，与细胞间或细胞与基质表面的粘着有密切关系，可能在细胞形态发生、细胞分化和组织的形成等方面具有重要作用。 3、微管：在真核细胞质中，由微管蛋白构成的，可形成纺锤体、中心体及细胞特化结构鞭毛和纤毛的结构。 4、微丝：在真核细胞的细胞质中，由肌动蛋白和肌球蛋白构成的，可在细胞形态的支持及细胞肌性收缩和非肌性运动等方面起重要作用的结构。 5、中间纤维：存在于真核细胞质中的，由蛋白质构成的，其直径介于微管和微丝之间，在支持细胞形态、参与物质运输等方面起重要作用的纤维状结构。 6、踏车现象：在一定条件下，细胞骨架在装配过程中，一端发生装配使微管或微丝延长，而另一端发生去装配而使微管或微丝缩短，实际上是正极的装配速度快于负极的装配速度，这种现象称为踏车现象。 7、微管组织中心（MTOC）：微管在生理状态及实验处理解聚后重新装配的发生处称为微管组织中心。动物细胞的MTOC为中心体。MTOC决定了细胞中微管的极性，微管的（-）极指向MTOC，（+）极背向MTOC。 8、胞质分裂环：在有丝分裂末期，两个即将分裂的子细胞之间产生一个收缩环。收缩环是由大量平行排列的微丝组成，由分裂末期胞质中的肌动蛋白装配而成，随着收缩环的收缩，两个子细胞被分开。胞质分裂后，收缩环即消失。 二、填空题 1细胞质骨架__是一种复杂的蛋白质纤维网络状结构，能使真核细胞适应多种形状和协调的运动。 2、肌动蛋白丝具有两个结构上明显不同的末端，即__正极___极和__负极___极。 3、在动物细胞分裂过程中，两个子细胞的最终分离依赖于质膜下带状肌动纤维束和肌球蛋白分子的活动，这种特殊的结构是___收缩环__。 4、小肠上皮细胞表面的指状突起是_微绒毛____，其中含有__微丝___细胞质骨架成分。 5、微管由__微管蛋白___分子组成的，微管的单体形式是___α微管蛋白和β微管蛋白__组成的异二聚体。 6、基体类似于__中心粒___，是由9个三联微管组成的小型圆柱形细胞器。 7、驱动囊泡沿着轴突微管从细胞体向轴突末端单向移动的蛋白质复合物是__驱动蛋白___。 8、细胞骨架普遍存在于真核细胞中，是细胞的支撑结构，由细胞内的蛋白质成分组成。包括微管、微丝和中间纤维三种结构。 9、中心体由 2 个相互垂直蛋白排列的圆筒状结构组成。结构式为 9×3+0 。主要功能是与细胞的分裂和运动有关。 10、在癌细胞中，微管数量减少，不能形成束状。在早老性痴呆患者脑组织细胞中微管大量变形。 三、选择题1、D；2、D；3、E；4、C；5、A；6、B；7、C；8、B；9、A； 1、细胞骨架是由哪几种物质构成的（）。 A、糖类 B、脂类 C、核酸 D、蛋白质 E.以上物质都包括 2.下列哪种结构不是由细胞中的微管组成（）。 A、鞭毛 B、纤毛 C、中心粒 D、内质网 E、以上都不是 3.关于微管的组装，哪种说法是错误的（）。 A、微管可随细胞的生命活动不断的组装与去组装 B、微管的组装分步进行 C、微管的极性对微管的增长有重要意义

木聚糖酶研究进展

木聚糖酶研究进展 刘亮伟 河南农业大学生命科学学院 郑州 450002 文化路 95 号llw321@https://www.wendangku.net/doc/bc19068827.html, 科学技术的进步给21世纪的人类带来了便利,也给人类带来了前所未有的压力：人口膨胀、能源危机、环境污染、资源匮乏，所有这些问题的本源是能源危机。与能源匮乏相矛盾，自然界通过光合作用赋予人类大量可再生资源：如纤维素和半纤维素，作为继纤维素后第一大生物资源的半纤维素在农业和木材工业中是常见的废弃物，它作为可再生资源的一个有利条件是它比纤维素更易于提取和水解。秸秆中半纤维素含量占其总干重的25～50%，其化学结构较纤维素复杂得多，由D-木糖通过β-1,4-糖苷键相连成的主链和少量L-阿拉伯糖侧链所组成[1]，这种D-木糖单元在硬木和软木中平均聚合度分别是150－200和70－130，要得到能够利用的单糖必须通过以木聚糖酶为主的半纤维素酶系协同作用进行水解而完成[2]。 内切-1,4-β-木聚糖酶（E.C 3.2.1.8）是一种内切糖苷酶，能够水解木聚糖这类自然界中最丰富的半纤维素，同自然界中五碳糖的循环相联系，在能量循环中占有重要地位。在古代人们就已经在生产过程中间接地利用各种酶进行生产：如酿酒、制作奶酪、烘焙面包、修饰淀粉等。1986年，Viikarri发现了木聚糖酶在纸浆漂白和造纸工业中能够降低环境污染物品的用量[3]，伴随着人类对于可持续性发展和环境的重视，木聚糖酶在工业上的应用明显增加，在1997-2002年间的5年中，纸浆造纸业用酶由1.0亿美元增加到1.92亿元，增长率为16.2%，是所有酶制品行业中增长率最快的。 1木聚糖酶的应用 1.1在纸浆造纸工业中应用 木聚糖酶最重要的用途是在纸浆造纸工业中对于纸浆的漂白。因为环境污染最大的来源是纸浆造纸工业中的废水。根据资料显示仅仅美国每年用于纸浆漂白的氯化物或次生氯化物用量就有200多万吨[4]。因为纸浆漂白污水中含有有毒物质，并且这些物质能在生态系统的生物和非生物组成中积累，如氯苯、氯二苯和其它氯化木质素次生物[5; 6]。这些化学物质对环境危害很大，据有关研究显示既便是远离造纸厂10公里以外的鱼群都会受到纸浆漂白污水中有害物质的负面影响[7]，这种受到污染的鱼可以直接或间接地影响人类的身体健康。木聚糖酶的作用就是对木聚糖进行水解从而加快了纸浆中木质素的释放，色素物质所以能够比较容易地从纤维素中释放出来。经实验证实，木聚糖酶的漂白效果比木质素降解酶好得多，这是因为木质素大部分交联在半纤维素上，而半纤维素比木质素更容易解聚[8]。利用木聚糖酶相应地比其它酶进行多聚物降解时，碳水化合物水解速度要快2-3倍[9]。经木聚糖酶处理后的纸浆漂白可以降低20%-40%漂白剂用量 [10]。

木聚糖酶是一种最主要的木聚糖降解酶类

木聚糖酶是一种最主要的木聚糖降解酶类。它主要通过内切方式降解木聚糖中β-1,4木糖苷键，水解产物以木寡糖为主，并伴有少量的木糖和阿拉伯糖。 产品规格 型号酶活剂型包装规格 FE504A10000 IU/g粉状20 kg/袋或桶 FE504B20000 IU/g粉状20 kg/袋或桶 FE504C30000 IU/g粉状20 kg/袋或桶 FE504D50000 IU/g粉状20 kg/袋或桶 FE504AL10000 IU/ml液体30 kg/桶或200 kg/桶FE504BL20000 IU/ml液体30 kg/桶或200 kg/桶FE504CL30000 IU/ml液体30 kg/桶或200 kg/桶 产品特点 ●采用新型国际专利菌种生产，产品性能优良，使用效果得以保证； ●先进的全自动液体深层发酵技术，领先的后处理加工工艺，保障了产品的 高纯度、高稳定性和良好的均匀度； ●采用基因工程技术改良发酵菌种，使内切酶活性大幅度提高，是普通木聚 糖酶的2.5～3.5倍； ●对不溶性木聚糖的降解能力显著提高，是普通木聚糖酶的3～6倍； ●有良好的对高温高湿的耐受能力，在饲料制粒条件下，制粒后的酶活可以 保持80％以上，保证了其在颗粒饲料中的使用效果； ●有良好的对动物胃酸、胃蛋白酶、胰蛋白酶和高浓度金属离子的耐受能力， 保证了其在动物生产中的使用效果； ●对饲料原料中木聚糖酶抑制因子有很好的耐受能力，保证了其对饲料中木 聚糖的良好降解效果。 产品功能 ●有效降解植物饲料中的抗营养因子——木聚糖，消除其抗营养作用，降低 食糜粘度，提高饲料养分的消化率和吸收利用率； ●与纤维素酶一起作用，有效摧毁植物细胞壁结构，促进植物细胞内其它营 养物质释放，提高原料中营养物质的利用率；

细胞骨架

微管组成的细胞器及研究动态 在细胞内，由微管所组成的细胞器几种： 一、中心体 (一)中心体的结构 中心体（centrosome）由中心粒（centrioles）和中心粒周围物质（pericentriolar material, PCM）共同组成。中心粒在细胞内一般有两个，成对存在于核的附近。每个中心粒是由9排微管（每排3条）围成的短圆筒状结构，两个中心粒在一端大致成垂直对应。 中心粒的直径为0.16～0.23μm，长度一般为0.16～5.6μm，差别较大。三联体包括3条微管，由内向外分别被编号为A、B、C亚丝，3条微管平行排列成片状三联体结构，只有A管是完全的微管且与中心粒的轴心向外伸出的辐射状的细丝相连。9组三联体按照一定的角度规则排列，形成了风车状。三联体之间有细丝相连，且在每一三联体的外侧均有被称为随体的致密物质存在。 （二）中心粒的发生 在中心粒周围物质中含有数百个由13个γ微管蛋白和其他蛋白质构成的γ微管蛋白环状复合体γTuRC是一条微管形成的起点，αβ微管蛋白二聚体以一定的方向添加到γ微管蛋白上。每条微管的起始端埋藏在中心粒周围物质中，以正端向外生长。γTuRC是微管生成的真正的诱导起点，起“晶种”的作用。实验证明，只要有γTuRC存在即可引导微管生长，而且所需要的微管蛋白的浓度要比在体外低得多。 中心粒在细胞中具有自我装配的能力。装配时，首先形成由9条单丝微管围成的环，9条单丝即成为将来的A亚丝，然后B亚丝再以“C”字形（横切面）装配到A亚丝上，最后“C”字形的C亚丝再装配到B亚丝上，此时三联体装配完成，形成前中心粒。在前中心粒的基础上进一步延长，直至形成成熟的中心粒。 二、纤毛和鞭毛

蛋白类木聚糖酶研究进展

蛋白类木聚糖酶抑制剂研究进展 专业：09生物工程班级：09级1班作者:许斌指导老师：龚妍春 摘要：木聚糖酶已广泛应用于饲料、食品加工、纸浆漂白等领域, 然而近年研究小麦等谷物中存在一种能抑制木聚糖酶活性的蛋白质性质的成分, 称为木聚糖酶抑制蛋白。木聚糖酶抑制蛋白具有多型性, 但不同类型抑制蛋白都只作用于外源木聚糖酶,而对谷物内源性木聚糖酶没有抑制作用。这就对木聚糖酶应用领域中酶功效的发挥提出了挑战: 抑制蛋白的存在是否影响外加木聚糖酶的作用? 本文综述了三类木聚糖酶抑制蛋白的分子结构抑制特性，阐明蛋白类抑制剂与木聚糖酶之间的互作机理, 为最大限度的发挥木聚糖酶功效奠定理论基础。简要介绍了木聚糖酶抑制蛋白对谷物的影响作用。 关键词:木聚糖酶;木聚糖酶抑制蛋白;抑制特性 1.引言 木聚糖作为植物中的一种主要的非淀粉多糖，含量仅次于纤维素，是自然界中第二大丰富的多聚糖。木聚糖是植物细胞壁多糖中半纤维素的主要成分，主链由D- 吡喃型木糖残基通过B-1, 4-糖苷键连接而成，主链上一般还带有少量的乙酰基、葡萄糖醛酸基、阿拉伯糖基等侧链取代基[1]。内切B-1-4木聚糖酶(EC3.2.1.2，简称木聚糖酶) 是专一性水解木聚糖主链的酶，将大分子木聚糖降解成低聚木糖、木二糖及少量的木糖，木聚糖酶主要由微生物产生，但一些藻类、原生动物、甲壳类动物和植物等也能产生木聚糖酶。根据催化结构域氨基酸的同源性和疏水簇分析法，木聚糖酶可分为GH10家族（包括植物酶类、真菌酶类和细菌酶类等）和GH11家族（包括真菌酶类和细菌酶类）2个家族。已知的禾谷类所产的木聚糖酶都属于GH10 家族，而微生物产生的木聚糖酶则属于F10 或G11 两个家族[2]。木聚糖除了在饲料工业中应用之外，在造纸制浆、食品加工等领域均有涉及。然而, 近年的研究发现微生物木聚糖酶的活性在体外试验中会被来自小麦等谷物的一种蛋白质性质的成分所抑制, 这种成分即木聚糖酶抑制蛋白。由于实验室应用试验所加木聚糖酶的量总是大于实际应用过程中的酶用量, 因此可以推测实际应用中外加的木聚糖酶也会受到基质中抑制蛋白的抑制作用, 从而影响用酶工艺过程[3]。许多有益微生物产生的木聚糖酶已经广泛应用于饲料面包焙制淀粉加工纸浆生物漂白等领域，而植物病原菌的木聚糖酶有方面作用:

木聚糖酶

木聚糖酶 本品精选优良菌株，经液体深层发酵精制而成的高效浓缩酶制剂。适用于饲料、食品、酿造、果蔬汁加工、纺织等行业。 作用原理 木聚糖是一种多聚五碳糖，为半纤维素的主要成分之一。木聚糖酶是一类降解木聚糖分子中β-1，4-木糖苷键的酶系，主要包括内切β- 1,4-木聚糖酶和β-木糖苷酶。内切β-1,4-木聚糖酶以内切方式作用于木聚糖主链内部的β-1,4-木糖苷键，其主要水解产物为低聚木糖和少量木糖。β-木糖苷酶通过水解低聚木糖的末端来催化释放木糖残基。木聚糖彻底降解为木糖需要这两种酶的共同参与。 理化性质 外观：黄色或白色粉剂及黄色液体. 作用pH范围：pH3.0-7.0，最适pH为5.0 作用温度范围：30-75℃，最适温度为50℃。 产品酶活 木聚糖酶酶活：1~30万u/g 酶活单位(U)定义：在50℃、pH5.0条件下，每分钟水解木聚糖产生1μg还原糖所需要的酶量定义为1个酶活力单位。 使用方法 本品可应用于饲料、食品、酿造、果蔬汁加工，植物提取、纺织等行业。因应用领域和生产条件等不同用量与用法而有所改变。用户也可以结合自己的工艺条件通过试验确定最佳使用方案。 5.包装规格

25kg/桶。 6.运输与贮存 运输时应避免日晒，贮存于阴凉干燥环境中（25℃以下可保存18个月）。 中性蛋白酶 中性蛋白酶采用枯草芽孢杆菌经深层发酵提炼而成。广泛应用于酒精、啤酒、味精、淀粉糖、发酵工业的液化以及纺织、印染退浆等. 一、产品性状: 1 、产品规格： 固体型分为 50000--100000u/g 。. 2、 1g固体酶粉在30℃，pH7.5条件下，1min水解酪素产生1ug酪氨酸所需的酶 量为1个酶活力单位，以u/g表示。 二、产品特性: 1 、热稳定性：最适作用温度40℃～50℃ 。 2 、 PH 稳定性：最适作用pH6.5～7.5，PH5.0 以下失活严重。 三、应用工艺（根据试验情况进行调整） 1、饲料用酶：该酶与a-淀粉酶、酸性蛋白酶、纤维素酶、糖化酶等复合使用。可以广泛应用于仔猪、育成猪、禽类、鱼类饲喂。参考用量为3-10u/g。 2、用于皮革脱毛：酶脱毛（35-42℃，pH7.5，20-25u/ml）→水洗→浸酸→揉制。 3、用于胶片回收：45℃，pH7.0-7.5，用20-23u/ml进行回收。 4、用于丝绸脱胶：预处理→脱水→酸处理（蛋白酶18-24u/ml，肥皂0.75%， 48-50℃，30-60分钟，pH 7-8）→脱水→扯皮→冲洗→脱水→抖松→烘干→抖松。 5、医药工业：含中性蛋白酶的药物，可起到消炎、利胆、止痛、助消化的功效。 6、焙烤行业的应用：改善成品的光泽，结构均匀一致，口感松爽酥脆。 四、注意事项 1、此产品可完全溶于水，使用安全可靠。操作时请勿直接与酶制剂接触，若有

知识点汇总-细胞骨架

细胞生物学知识点汇总 I说明： 本文档是王飞老师细胞生物学课上内容的精炼和总结，也是考试出题的主要依据。内容过于精炼则必有若干舍弃之处，希望同学不要为了考试而学习，将这份文字资料为你节省的复习时间用于阅读中英文教材和查找感兴趣的细胞生物学领域的前沿资料，这样才能对这门课程有一个更加全面的了解。 本文档中出现的英文不要求掌握（名词解释部分除外），只是对复杂中文名词或重点内容的一个辅助的英文注解。由于某些中文名称的翻译过于繁琐且不合理，不如英文名称容易记忆，因此中英文只要掌握一种即可，在考试过程中无论是中文、英文还是英文缩写，只要写对任何一种即可得分。 内容编写过程中缺乏足够的审核步骤，如发现错别字或内容明显错误之处请及时联系老师确认内容的正确性。 II 细胞骨架知识点汇总: 核心知识点（约占考试总分值的60%）：1 7 20 25 29 32 41 44 45 49 51 普通知识点（约占考试总分值的30%）：3 9 11 12 14 16 17 18 19 23 26 28 30 31 35 37 38 39 43 47 48 50 54 扩展知识点（约占考试总分值的10%）：2 4 5 6 8 10 13 15 21 22 24 27 33 34 36 40 42 46 52 53 55 1 细胞骨架（cytoskeleton）的定义与种类： 定义：细胞骨架是贯穿整个细胞的复杂的纤维状蛋白网络结构

细胞内有三种类型的细胞骨架，分别是微丝（microfilament,MF），微管（microtubule,MT）和中间丝（intermediate filament，IF）。 2 肌动蛋白（actin）的种类及分布 真核细胞内的肌动蛋白主要分为三大类，名称及分布情况如下： α肌动蛋白 主要存在于肌肉细胞的收缩性结构中，目前已发现的四种α肌动蛋白分别属于横纹肌、心肌、血管平滑肌和肠道平滑肌。 β肌动蛋白 存在于所有种类的细胞内，是细胞内绝大部分微丝骨架的基本组分。 γ肌动蛋白 在所有细胞内都有分布，主要存在于与应力纤维相关的结构中。 3微丝的组成与极性 A微丝由肌动蛋白单体聚合而成。 B肌动蛋白是一种球状蛋白，其三维构象具有一道很深的裂缝，在裂缝内部有一个核苷酸结合位点（可与ATP或ADP结合）和一个二价阳离子结合位点（可与Mg2+或Ca2+结合）。 C 肌动蛋白单体聚合形成螺距为36nm（7个单体分子）的双股螺旋状微丝纤维。每个肌动蛋白单体都与四个其他肌动蛋白单体紧密相邻。 D 微丝中的所有肌动蛋白单体分子的缝隙开口端或缝隙底部都朝着同一方向排列，因此整个微丝纤维具有极性。缝隙开口端指向的是微丝的负极（minus end），缝隙底部指向的是微丝的正极（plus end）。

木聚糖酶活力特性研究

木聚糖酶活力特性研究 郑翔鹏 （福建省燕京惠泉啤酒股份有限公司） 概况 木聚糖酶分子只含一个亚基，分子量在8～30kD间的为碱性蛋白，分子量在30～145kD 间的为酸性蛋白。PI值为3～10.5，稳定pH值为3～10，反应最适pH值在4～7之间，最适温度为40～60℃。离子通过改变酶的构象影响木聚糖酶的稳定性，一般情况下,Ag+ (离子浓度1 mmol·L - 1 ,抑制酶活达100% ) 、Hg2 + (离子浓度1 mmol · L - 1 , 抑制酶活达7013% ) 、Cu2 + (离子浓度2. 00 mg·ml- 1 ,抑制酶活达25. 42% )等离子抑制木聚糖酶的活性,Mg2 + (离子浓度2. 00 mg·ml- 1 ,提高酶活达6% ) 、Mn2+ (离子浓度1 mmol·L - 1 ,提高酶活达24% )等离子则能提高木聚糖酶的活性。Ag+ 、Hg2 + 、Cu2 +等离子主要通过改变酶分子中2SH基团的还原态或直接攻击酶分子中的某些氨基酸残基,改变酶的构象来抑制木聚糖酶的活性， Mg2 + 、Zn2 +等则通过影响酶与底物的结合及解离状态,提高酶的活性,其具体机制还有待进一步研究。 木聚糖酶的分子结构由功能结构域和连接区构成。其中，功能结构域由催化结构域和纤维素结合结构域构成，纤维素结合结构域可改变酶对可溶或不溶底物的活力。根据结构域的相似性，木聚糖酶可通过结构域的改组和随后结构域的修饰而进，许多木聚糖酶具有纤维素酶的活性。木聚糖酶与木聚糖的结合利用离子间的静电作用。木聚糖含有的4-O-甲基葡糖醛酸带负电，木聚糖酶在pH低于PI时带正电荷，易于结合，而在pH值高于PI时，则不易结合。其反应为典型的酸碱亲核水解反应。 木聚糖酶特性分析 在对木聚糖酶的特性分析中，着重分析酶活力与温度、PH值、钙离子对酶活力的影响。 1.1木聚糖酶活力分析 对于木聚糖酶活力的分析，国标中没有相应的推荐方法。目前，主要采用分光比色测定反应液颜色的强度来定量分析酶的活力。木聚糖酶活力单位是指在50℃、pH值为5.3的条件下，每分钟从浓度为10mg/ml的木聚糖溶液中降解释放1μmol还原糖所需要的酶量为一个酶活力单位U。 木聚糖酶能将木聚糖降解成寡糖和单糖。具有还原性末端的寡糖和有还原基团的单糖在沸水浴条件下可以与DNS试剂发生显色反应。反应液颜色的强度与酶解产生的还原糖量成正比，而还原糖的生成量又与反应液中木聚糖酶的活力成正比。 吸取水1.0ml，加入DNS试剂3.0ml，沸水浴加热5min。用自来水冷却至室温，制成标准空白样。分别吸取木糖溶液1.00、2.00、3.00、4.00、5.00ml，分别用水定容至100ml，配制成浓度为0.10～0.50mg/ml木糖标准溶液。分别吸取上述浓度系列的木糖标准溶液各1.00ml （做二个平行），分别加入到刻度试管中，再分别加入3mlDNS试剂。电磁振荡3s，沸水浴加热5min。然后用自来水冷却到室温，以标准空白样为对照调零，在540nm处测定吸光度OD值。以木糖浓度为Y轴、吸光度OD值为X轴，绘制标准曲线。每次新配制DNS试剂均需要重新绘制标准曲线。 固体试样应粉碎或充分碾碎，然后过60目筛（孔径为0.25mm）。液体试样可直接称取。称取试样，精确至0.001g。加入250ml乙酸-乙酸钠缓冲溶液。磁力搅拌30min，再用缓冲溶液定容至500ml，在4℃条件下避光保存12h，过滤。再用缓冲溶液做二次稀释（稀释后的待测酶液中木聚糖酶的活力最好能控制在0.04～0.08U/ml之间）。

1知识点汇总细胞骨架

细胞生物学知识点汇总 I说明: 本文档是王飞老师细胞生物学课上内容的精炼和总结,也是考试出题的主要依据。内容过于精炼则必有若干舍弃之处，希望同学不要为了考试而学习，将这份文字资料为你节省的复习时间用于阅读中英文教材和查找感兴趣的细胞生物学领域的前沿资料,这样才能对这门课程有一个更加全面的了解。 本文档中出现的英文不要求掌握（名词解释部分除外)，只是对复杂中文名词或重点内容的一个辅助的英文注解。由于某些中文名称的翻译过于繁琐且不合理,不如英文名称容易记忆，因此中英文只要掌握一种即可，在考试过程中无论是中文、英文还是英文缩写，只要写对任何一种即可得分。 内容编写过程中缺乏足够的审核步骤,如发现错别字或内容明显错误之处请及时联系老师确认内容的正确性。 II 细胞骨架知识点汇总: 核心知识点(约占考试总分值的60%）：１７2０25 ２9 ３2 41 ４4 45 4９51 普通知识点(约占考试总分值的30%）：３9 １1 12 1416 １718 19 2３2６２8 30 31３5 37 38 39 ４347 48 50 5４ 扩展知识点（约占考试总分值的1０%):２ 4 5 6 8 10131５2１22 2４27 ３334 3640 ４2 ４６525３55 1 细胞骨架（cyｔosｋeleton）的定义与种类： 定义：细胞骨架是贯穿整个细胞的复杂的纤维状蛋白网络结构 细胞内有三种类型的细胞骨架,分别是微丝(micｒofilamｅnｔ,ＭF),微管（micｒo ｔｕｂule,MT)和中间丝（inｔerｍedｉａte ｆiｌａｍｅnｔ,ＩF）。 2肌动蛋白(aｃｔｉn）的种类及分布 真核细胞内的肌动蛋白主要分为三大类,名称及分布情况如下: α肌动蛋白 主要存在于肌肉细胞的收缩性结构中，目前已发现的四种α肌动蛋白分别属于横纹肌、心肌、血管平滑肌和肠道平滑肌。 β肌动蛋白 存在于所有种类的细胞内,是细胞内绝大部分微丝骨架的基本组分。 γ肌动蛋白 在所有细胞内都有分布,主要存在于与应力纤维相关的结构中。 3微丝的组成与极性 A微丝由肌动蛋白单体聚合而成。

木聚糖酶

木聚糖及木聚糖酶介绍及实际生产中存在的问题 来源：中国猪e网作者：董亚维时间：2006-08-18 点击： 999 目前，饲料资源的短缺制约着我国畜牧业的发展，尤其是主要能量饲料玉米短缺所导致的一系列问题不容忽视。因此，开发其它非常规饲料资源作为能量饲料对于我国饲料工业发展，尤其是饲料企业的生存具有积极的意义。我国是小麦、大麦等麦类作物的盛产国。在某些季节里，麦类作物的价格低于玉米，其常规营养成分含量相对于玉米也有一定的优势。所以，开发麦类作物取代部分玉米作为能量饲料是非常必要的。然而大量试验报道，麦类作物中含有的非淀粉多糖（NSP）具有影响动物消化吸收、阻滞养分消化代谢的作用，成为麦类作物作为能量饲料利用的瓶颈。 常见的非淀粉多糖包括以下几种：纤维素和半纤维素聚合物（如木聚糖、β－葡聚糖、苷露糖等）和果胶多糖。目前，消除非淀粉多糖抗营养作用的主要方法是，在麦类作物中添加非淀粉多糖酶（NSP酶）。本文就木聚糖的抗营养机理和木聚糖酶的添加效果做一简要概述。 1.木聚糖 1.1 木聚糖的分布和物理结构 木聚糖是半纤维素的一种，是饲料作物中含有的一类粘性非淀粉多糖，主要存在于小麦、黑麦和黑小麦中，以黑麦中含量最高。非淀粉多糖可分为可溶性和不溶性两种。小麦、大麦等作物中的木聚糖主要是水溶性的，而玉米、高梁中的木聚糖大部分是不溶于水的。 木聚糖是由D－木糖主链（以β－1,4键相连）和L－阿拉伯糖分枝（α－1,2和α－1,3相连）所组成的聚合物，由于它是由阿拉伯糖和木糖两种单糖聚合而成，因此也称阿拉伯木聚糖或戊聚糖。 1.2麦类作物中木聚糖的含量 从总木聚糖含量来看，黑麦中含量最高，其次是燕麦、小黑麦、小麦和大麦；而从水溶性木聚糖含量来看，黑麦、小黑麦和小麦中的含量高于大麦和燕麦。作物中木聚糖的含量除了受作物品种差异的因素影响以外，相同品种中品系的不同也会影响木聚糖的含量。M.D.Fleurg试验测定，无壳大麦、六棱大麦和二棱大麦中的总木聚糖含量分别为4.07%、6.12%和5.61%，而水溶性木聚糖含量分别为0.58%、0.63%和0.52%。当然，环境温湿度的变化也会影响麦类作物中木聚糖的含量，有学者发现，干燥地区生长的大麦和燕麦比潮湿地区的木聚糖含量高。 1.3木聚糖抗营养机理 水溶性木聚糖具有营养稀释作用，有抗营养特性。对动物健康有多方面影响。Fengler（1988）指出，水溶性NSP可以在动物肠道形成高粘性物质，延缓营养物质与消化液的混和速度。阻滞营养物质向肠道粘膜表面绒毛的扩散(Ikegami，1990)。使食糜内各组分混合不均，从而减慢食糜通过消化道的速度和养分的扩散速度，以至于造成肠粘膜不动水层加厚，导致营养物质在肠道内的积累，并且代偿性地增加内源性蛋白质、水分、矿物质的分泌，降低营养物质在动物体内的蓄积，影响动物的生产性能。木聚糖由于阻碍养分的吸收，造成营养物质在胃中的大量蓄积，食糜通过消化道的速度降低，从而减小菌群的移动速度，使细菌得以在小肠上段大量定居下来。富含养分的食糜是细菌尤其是致病菌处于温暖湿润肠道环境中的良好培养基。细菌的大量增殖会导致许多酸性物质产生，还会改变肠道PH值环境，从而影响消化酶发挥最佳效应。细菌数量增多会竞争性地吸收大量营养物质，降低物质的利用率，同时也使动物腹泻的频率增加（冯涛，2003）。此外，木聚糖可直接与肠道胰蛋白酶、脂肪酶结合，从而降低内源性消化酶在动物肠道内的活性。 2木聚糖酶 2.1木聚糖酶的结构及理化性质

木聚糖酶在工业上的应用

真菌中的木聚糖酶:性能及其在工业上的应用 摘要：木聚糖是半纤维素的主要类型。这是一个由木二糖通过1,4位糖苷键连接的线性聚合物。在自然界中，多糖的分子骨干可以被4-O-甲基-α-D-吡喃葡糖醛酸、乙酰基、α-L-阿拉伯呋喃糖基等比例添加。木聚糖的水解主要是酶的复合物承担，但主要参与的酶是内切β-1，4-D-木聚糖酶和β-D-木糖苷。这些酶可由真菌、细菌、酵母、海洋藻类、原生动物、蜗牛、甲壳类动物、昆虫、种子等产生,但是主要商业来源是丝状真菌。最近,有很多工业对木聚糖及其其水解酶感兴趣,主要是其可用于补充动物饲料、生产面包、食物和饮料、纺织品、纤维素纸浆的漂白、乙醇和木糖醇的生产。本文描述了一些木聚糖的特性和它的新陈代谢,木聚糖酶的生化特性以及其商业应用。

一、木聚糖结构 阿拉伯木聚糖已确定在小麦、黑麦、大麦、燕麦、大米、高粱、以及其他一些植物中发现，如：盘固草、竹笋和黑麦草。尽管这些多糖是次要部分对于的整体的谷物,但它们是构成植物细胞壁的重要组成部分(Izydorczyk和Biliaderis 1995)。葡糖醛酸和葡糖苷酸阿拉伯木聚糖主要位于二层膜结构中，他是一种粘合剂，使非共价键结构与木质素、纤维素和其他聚合物形成一种共价键而粘合，对细胞壁的完整性起到至关重要作用。木聚糖在被子植物中是半纤维素的主要类贡献者，占总干重的15-30%,但在裸子植物中木聚糖的含量会少点，含有7- 12%(Haltrich 1996年)。 图1 O-乙酰基-4-O-甲基葡糖醛酸(a),硬木和阿拉伯-4-O-甲基葡糖醛酸(b),柔软木头的结构。木聚糖酶参与分解木聚糖的有:乙酰酯酶、α-葡萄糖醛酸酶、切木聚糖酶和α-L-阿拉伯呋喃。β-木糖苷酶(c)实现了水解；数据显示碳原子被Ac乙酰基群替换

细胞骨架与遗传性疾病概述

细胞骨架与遗传性疾病概述 雷宇华　廖峥嵘　赵俊霞　王忠海倡　（河北医科大学基础医学学院　石家庄　０５００１７） 摘　要　细胞骨架包括微管、微丝和中间纤维三种类型，是细胞生命活动中不可缺少的重要细胞器，对细胞形态的改变和维持、细胞内物质运输、细胞的分裂和分化、信息传递等具有重要的作用。许多疾病的发生与细胞骨架结构和功能异常密切相关。本文对与细胞骨架相关的遗传性疾病进行概述。 关键词　细胞骨架　细胞器　遗传性疾病 细胞骨架（ｃｙｔｏｓｋｅｌｅｔｏｎ）普遍存在于真核细胞中，但直到１９６３年采用戊二醛室温固定细胞后，才广泛地观察到各类骨架纤维，并正式命名为细胞骨架。在这之前的电镜制样多采用锇酸或高锰酸钾低温固定细胞，破坏了骨架系统的大部分结构，大大妨碍了细胞骨架的研究。细胞骨架是指真核细胞质中纤维状蛋白组成的网架体系，是细胞的重要组成部分，属于一类细胞器。细胞骨架异常可引起很多疾病的发生，一些遗传性疾病与细胞骨架的异常或基因突变密切相关。 １　细胞骨架的组成及功能 细胞骨架是一种高度动态的结构，主要包括微管、微丝和中间纤维三种类型。微管的成分是微管蛋白，微管还能与少量的微管结合蛋白共同装配成纤毛、鞭毛、基体、中心体和纺锤体等细胞的特定结构。微丝又称肌动蛋白纤维，是直径为５～８ｎｍ的实心细丝状结构，主要成分为肌动蛋白，它与微丝结合蛋白共同参与了微丝的装配及功能的实现。中间纤维是一种直径约１０ｎｍ的纤维状蛋白，因其直径介于微管和微丝之间而得名。中间纤维是三类细胞骨架中结构相对稳定的，但成分最为复杂的一种。根据氨基酸序列的同源性，微管蛋白被分为Ⅰ型酸性角蛋白、Ⅱ型中／碱性角蛋白、Ⅲ型中等纤维蛋白（包括波形蛋白、结蛋白和外周蛋白等）、Ⅳ神经丝蛋白、Ⅴ核纤层蛋白和Ⅵ巢蛋白六类，这些蛋白分布具有严格的组织特异性。 细胞骨架蛋白的含量在真核细胞中十分丰富，约占细胞总蛋白的１０％～３０％，且在进化上高度保守。细胞骨架对于维持细胞的形态、细胞的运动、细胞内物质运输、染色体分离、细胞分裂与分化、能量转换和信息传递等起着重要的作用，是生命活动不可或缺的细胞结构。 ２　与细胞骨架异常相关的遗传性疾病 ２．１　单纯型大疱性表皮松解症　单纯型大疱性表皮松解症（ｅｐｉｄｅｒｍｏｌｙｓｉｓｂｕｌｌｏｓａｓｉｍｐｌｅｘ，ＥＢＳ）属于常染色体显性遗传。临床症状主要是表皮对机械损伤的反应加剧，故当多次摩擦后，暴露部位关节面如手足、膝肘、颈及其他部位会发生水疱及大疱，温暖、摩擦往往加重病情。患者的毛发、牙齿、黏膜及指甲却很少波及。该病多于２岁以内发病，随病程的延长，可逐渐消退。ＥＢＳ对人体的损害较小，与其他型大疱性表皮松解症的区别是预后较好，病变部位一般不结瘢，也不致发生皮肤严重萎缩［１，２］。发病原因是编码角蛋白Ｋ５及Ｋ１４的基因点突变引起，这两个基因分别定位于染色体１２ｑ１１～ｑ１３和１７ｑ１２～ｑ２１位点，突变引起基底细胞内角蛋白的组成和结构异常［３］。该病目前尚无特效疗法，应保护皮肤，避免外伤及摩擦，防止皮肤损伤感染。 ２．２　原发性纤毛运动障碍　原发性纤毛运动障碍（ｐｒｉｍａｒｙｃｉｌｉａｒｙｄｙｓｋｉｎｅｓｉａ，ＰＣＤ）属常染色体隐性遗传性疾病，包括纤毛不动综合征、Ｋａｒｔａｇｅｎｅｒ综合征、纤毛运动不良和原发性纤毛定向障碍等几种类型。临床主上有５０％的患者有Ｋａｒｔａｇｅｎｅｒ综合征，表现为内脏反位、慢性鼻窦炎和中耳炎以及支气管扩张症。由于精子尾部是一种纤毛的变型，当其结构异常时，精子摆动能力缺乏，所以男性患者还可以引起不育［４］。发病原因主要为编码动力蛋白的重链ＤＮＡＨ５基因突变，导致外部和内部动力蛋白臂的缺陷，从而使纤毛运动异常，黏膜上纤毛清除功能障碍，产生慢性或反复呼吸道感染，该基因定位于染色体５ｐ１５．２［５］。现已证实纤毛轴丝含有１００余种多肽，任何一种多肽有缺陷，均可造成同样的病理结果［６］。该病的应对以增强体质、预防发病为主。针对呼吸道反复感染，主要是对症治疗，可用抗感染及促进痰液排除的药物，保护肺功能，同时应预防其他感染。 ２．３　遗传性心脏病 ２．３．１　扩张型心肌病　扩张型心肌病（ｄｉｌａｔｅｄｃａｒｄｉｏ－ｍｙｏｐａｔｈｙ，ＤＣＭ）是一种以左心室或双心室扩张，同时伴有心肌收缩功能减退为主要特征的心肌疾病。其临床表现主要为进行性心衰、心律失常、血栓栓塞，病死率较高。研究表明，约有３０％的ＤＣＭ与遗传因素有关，主要的遗传方式为常染色体显性遗传，少数为常染色体隐性遗传、性连锁遗传和线粒体遗传。研究表明，编码心脏骨架蛋白的基因突变与ＤＣＭ发病密切相关。这些基因突变会影响心肌细胞的收缩力、心肌细胞力量传导及心肌细胞的发育成熟，导致心肌细胞慢性机械损伤，进而间质纤维化，心脏扩大。与之相关的细胞

食品生物化学 木聚糖酶及其应用

附件一: 新疆农业大学 专业文献综述 题目: 木聚糖酶及其应用 姓名: 全莉 学院: 食品科学与药学学院 专业: 食品科学与工程 班级: 食科112班 学号: 114031226 指导教师: 蓬焕明职称: 副教授 20012 年12 月20 日 新疆农业大学教务处制

木聚糖酶及其应用 姓名：全莉指导老师：蓬焕明 摘要：木聚糖是一种多聚五碳糖，是植物半纤维素的主要成分，是仅次于纤维素的第二β-1，4-内切木聚糖酶能够以内切方式作用于木聚糖主链产生不同长度的木寡糖和少量的木糖，是木聚糖降解酶系中最关键的酶。木聚糖酶是可将木聚糖降解成低聚木糖和木糖的水解酶,在食品、制浆造纸、饲料等行业上有着广阔的应用前景.本文主要从木聚糖酶的分类、特性及其应用等方面进行阐述。 关键词：木聚糖酶；分类；特性；应用 引言：丰富的可再生资源。木聚糖木聚糖结构复杂，完全降解需要多种酶的参与，其中木聚糖是以木吡喃糖为单位的由β-1， 4键连接的半纤维素，富含于阔叶树和大多数一年生植物体内，是一种重要的可再生资源，仅次于纤维素。它多为异聚多糖，结构变化范围很大，从β-1，4糖苷键相连接的多聚木糖线性分子到高度分枝的异质多糖。目前，木聚糖酶主要由微生物生产，已报道能生产木聚糖酶的微生物有丝状真菌、细菌和链霉菌等。微生物产生的木聚糖酶具有多样性，即常常产生不止一种类型的木聚糖酶，而且这些木聚糖酶的特性也存在差异。木聚糖酶可广泛应用于食品、制浆造纸、饲料等行业。 正文： 1 木聚糖酶的分类 1.1木聚糖酶 木聚糖酶是指能够降解半纤维素木聚糖的一组酶的总称，主要包括三类:内切-β-1,4一木聚糖酶，作用于木聚糖和长链木寡糖，从β-1,4一木聚糖主链的内部切割木糖苷链，从而使木聚糖降解为木寡糖，其水解产物主要为木二糖与木二糖以上的寡聚木糖，也有少量的木糖和阿拉伯糖;外切-β-1,4一木聚糖酶，作用于木聚糖和木寡糖的非还原端，产物为木糖; β-木糖苷酶,该酶通过切割木寡糖末端而释放木糖残基[1]。 1.2 根据所水解的木聚糖苷键类型 木聚糖酶可分为β-1,4糖苷键木聚糖酶和β-1,3糖苷键木聚糖酶两类。陆上植物的木聚糖酶均属β-1,4糖苷键木聚糖酶，而β-1,3糖苷键木聚糖酶大都存在于海藻及海洋生物中。按木聚糖酶的序列同源性和疏水族，木聚糖酶分别属于糖苷水解酶的两个家族，即F家族(10家族)和G家族(11家族),属于同一家族的木聚糖酶催化区域具有同源性，可以根据已知家族的酶来推测未知酶的催化特性[2]。F家族的木聚糖酶分子量高，结构复杂，通常生成较小的低聚糖，该家族的木聚糖酶可以作用于对硝基苯和对硝基苯纤维二糖，与底物结合需要较少数量的点;G家族的木聚糖酶则对木聚糖有很高的特异性。 1.3 依据木聚糖酶对底物的特异性 木聚糖酶可分为特异性木聚糖酶和非特异性木聚糖酶。特异性木聚糖酶特异作用于木聚糖底物，非特异性酶除作用于木聚糖外，还能作用于纤维素及人工底物，称双功能酶。

细胞骨架总结

第九章：细胞骨架 概述： 1. 细胞骨架：细胞内以蛋白质纤维为主要成分的网络结构，主要包括微丝（MF），微管（MT），中间纤维（IF） 2. 微丝：分布在细胞质膜的内侧，确定细胞表面特征，使细胞能够运动和收缩； 微管：主要分布在核周围，并呈放射状向胞质四周扩散，确定膜性细胞器的位置和作为膜泡运输的轨道； 中间纤维：分布在整个细胞，使细胞具有张力和抗剪切力 3. 广义的细胞骨架还包括：核骨架，核纤层，细胞外基质。形成贯穿细胞核，细胞质，细胞外的一体化网络结构 第一节：微丝 微丝：由肌动蛋白组成的直径约为7nm的骨架纤维，又称肌动蛋白纤维 微丝和结合蛋白，肌球蛋白构成化学机械系统，利用化学能产生机械运动 一. 微丝的组成及其组装 1. 肌动蛋白分类（根据等电点）：α：分布于各种肌肉细胞 β、γ：分布于肌细胞和非肌细胞 2. 肌动蛋白存在形式：单体：球状肌动蛋白（G-actin） 多聚体：纤维状肌动蛋白（F-actin） 3. 形态结构： actin单体外观呈哑铃形，其上有3个结合位点：1个为ATP结合位点，2个为结合蛋白结合位点 F-actin是由两条线形排列的肌动蛋白链形成的螺旋，有极性 4. 组装与去组装： （1）通常只有结合ATP的肌动蛋白单体才能参与微丝的组装 （2）Ca2+浓度适当，Na+、K+浓度低时：微丝趋于解聚 含有ATP、Mg2+以及高浓度Na+、K+时：微丝趋于组装 （3）微丝正极组装速率快于复极 （4）细胞松弛素：与微丝结合后切段微丝，并结合在末端，抑制聚合，但不影响解聚鬼笔环肽：抑制解聚 二. 肌球蛋白 1. 分子马达：指依赖于微管的驱动蛋白、动力蛋白和依赖于微丝的肌动蛋白这三类蛋白质家族成员。他们既能与微丝或微管结合，又能与一些细胞器或膜状小泡特异性结合，并利用水解ATP所产生的能量有规律地沿微管或微丝等细胞骨架纤维运输“货物” 2. 肌动蛋白的马达结合域包括：1个微丝结合位点；1个具有ATP酶活性的ATP结合位点 3. 由1个重链和几个轻链组成，有三个结构域： ①头部结构域：最为保守，为马达结构域，负责产生力 ②颈部结构域：为α-螺旋，通过同钙调素或类似钙调素来调节轻链亚基结合，来调节头部的活性 ③尾部结合域：决定同膜结合还是同其他尾部结合 4. 分类：肌球蛋白Ⅱ：为肌肉收缩和胞质分裂提供力 肌球蛋白Ⅰ、Ⅴ：涉及细胞骨架和膜之间的相互作用

酸性木聚糖酶

酸性木聚糖酶 木聚糖酶产生介绍 木聚糖酶的生产5.1菌种5.1.1 菌种选育 木聚糖酶广泛存在于细菌、放线菌、真菌和酵母菌中[9~12]。目前,已从20余种细菌菌株、16种真菌、3种酵母以及8种放线菌中分离出相应的木聚糖酶[13]。通常生产条件下的极端温度和pH等环境因素对酶的稳定性有影响,使酶容易失活,这就限定了许多酶的应用,故从嗜极性的微生物中分离出木聚糖酶已经得到广泛的关注。目前已经发现了不少嗜碱性的微生物中含木聚糖酶,其中大多数为细菌,只有一种嗜碱性嗜碱性头孢霉属(Cephalosporium)真菌的木聚糖酶被报道。酸性木聚糖酶是一种pH在酸和中性条件下的木聚糖酶制剂，用于降解木聚糖成为木糖。酸性木聚糖酶的主要活性成分是能够降解植物木聚糖的木聚糖酶（内切-1,4-β-木聚糖酶，EC3.2.1.8）。酸性木聚糖酶是由木聚糖酶高产菌株发酵而成，特别适合应用于食品、饲料、乙醇和废水处理工业。 纤维素和木聚糖是两种重要的多糖组分，其水解产物葡萄糖和木糖能够应用在大量的工业生产中。木聚糖是一种由b-1,4 糖苷键连接的木聚糖单位构成的半纤维素同聚物。木聚糖是木质素和保护纤维素基质的果胶连接而成的。 谷物例如小麦、大麦和黑麦与动物饲料相结合以产出较大的能量。为了能够最大限度的提高纤维素酶的活力，需要木聚糖酶的协同作用。 工作机理 酸性木聚糖酶的主要水解酶是木聚糖酶（内切-1,4-β-D-木聚糖酶，EC3.2.1.8）和b-木糖苷酶（1,4-b-D-木糖苷酶, EC 3.2.1.37）。木聚糖酶（1，4-D-木聚糖酶）任意水解木聚糖内部的1,4- a-D-木聚糖苷链，从而释放木-低聚糖和木聚糖苷键。b-木糖苷酶水解木聚糖和小的木低聚糖成为木糖（5碳糖）。 特性 酸性木聚糖酶木聚糖酶适用的pH范围是4.0-5.5，温度范围是30-60℃。最高规格固体酸性木聚糖酶 200000u/g；液体酸性木聚糖酶 100000u/g; 酶活力单位定义：具体条件下，1min内从木聚糖产生1ug木糖所需要的酶量。使用说明添加量根据技术人员的建议进行。 包装 酸性木聚糖酶的包装规格为25kg/塑料桶。可根据需要的体积大小提供可替换的包装袋。 木聚糖酶酶学性质

细胞骨架蛋白

细胞骨架蛋白 肌动蛋白与微管蛋白都是细胞骨架的主要成份,它们在真核细胞的细胞质中广泛分布。这些蛋白在原核生物细胞中并不存在，但在它们细胞中存在微管蛋白的类似物FtsZ与肌动蛋白的类似物MreB。这两种蛋白在原核生物细胞中起到类似于肌动蛋白与微管蛋白在真核细胞中的作用。FtsZ蛋白在微生物细胞以及一些真核生物的细胞器的分裂中起到关键的作用。MreB蛋白在维持微生物细胞形状以及在细胞分裂中质粒的分配起到核心作用。本文献是一篇综述，通过查阅文献对微生物中的细胞骨架蛋白的生化性能作了系统的阐述。 FtsZ蛋白是微管蛋白的先祖，对微生物细胞分裂起到重要作用。原核生物细胞的分裂与其它高等细胞的分裂有所不同，由于其细胞外面包裹着坚硬的细胞壁，使其细胞分裂要复杂一些。在原核生物细胞分裂时，FtsZ蛋白会率先到达细胞要分裂的位置，然后自我组装形成Z环。Z环会结合GTP，GTP水解形成GDP并释放能量，此时Z环利用能量捕获细胞质中所需蛋白质进而形成细胞壁，从而完成细胞分裂。最近Stricker等人采用电镀刺激分裂时的微生物细胞，并用荧光实验定位FtsZ蛋白，发现Z环的活性处于一个动态平衡状态中，大约只有30%的FtsZ蛋白存在于Z环中，其余的FtsZ蛋白都游离于细胞质中，Z环中的FtsZ蛋白与游离的FtsZ蛋白两者之间不停地进行快速地蛋白交换。其交换时间只有1分钟。到目前为止关于FtsZ蛋白还有两方面的关键问题有待解决，分别是①是什么信号分别启动了Z环的形成与决定了细胞分裂的位置。②纵组装到压缩的分子机制是什么？Z环是一种动态平衡的结构，它停地进行FtsZ蛋白的组装以维持其活性，但其在捕获形成细胞壁的蛋白时会隨这些蛋白进行压缩，这个现象的分子机制还未弄清。 MreB蛋白起到维持细胞形状的作用，第一个MreB蛋白的基因是在大肠杆菌中发现的。与它同时发现的还有MreC与MreD蛋白基因，它们三者之间是相邻的。这三种基因突变会导致大肠杆菌形状的改变，由棒状变成球状。一般而言，在有MreB蛋白的细胞中都有MreC与MreD蛋白，它们三者共同起到维持细胞形状的作用。但目前又发现了一种与MreB蛋白相似功能的蛋白MreI，这种蛋白也起到了维持细胞形状的作用。微生物细胞的螺旋形状就是由MreB蛋白与MreI蛋白共同作用形成的，这两种蛋白形成的纤维状结构会沿着细胞膜进行分布。这两种蛋白在细胞形状的维持过程中分工不同，MreB蛋白调控细胞的宽度，而MreI蛋白对细胞的长度，线状形成有关。但哪一种蛋白在维持细胞螺旋形状时起到关键作用还未曾得知。 工作进度报告 目前我主要的工作就是张老师的申报课题：在极端环境的土样中筛选能产生新抗生素的菌株。由于能产生抗生素的微生物主要是链霉菌，所以我们主要从土样中筛选链霉菌，到目前为止，已经筛到链霉菌株接近400株，而有明显抑菌圈的菌株也筛到了70多株，其中具有明显抑菌圈的链霉菌也有10株。这些菌株已经冻存。接下来，我还会进行土样菌种筛选工作，等把11种土样都筛选完就会进行抑菌实验。