养殖条件下3种锦蛇甲状腺相关激素和生长的比较研究

为深入了解人工饲养条件下棕黑锦蛇(Elaphe schrenckii)、赤峰锦蛇(E.anomala)和王锦蛇(E.carinata)生长情况及与甲状腺相关激素的关系,本研究在蛇类非冬眠时期的5月、7月和9月,以尾静脉采血获得3种锦蛇的血清,检测其血清中促甲状腺激素释放激素(TRH)、促甲状腺激素(TSH)和甲状腺素(T4)含量,并记录观察期间3种蛇的体重和体长的增长以及进食量。检测结果,王锦蛇的促甲状腺激素释放激素(TRH)、促甲状腺激素(TSH)和甲状腺素(T4)含量均低于其他2种锦蛇,3种锦蛇促甲状腺激素释放激素(TRH)、促甲状腺激素(TSH)含量最高值均出现在7月份;除了赤峰锦蛇外,棕黑锦蛇和王锦蛇的甲状腺素(T4)含量最高值也出现在7月份,与蛇类快速生长的时间相一致。另外,棕黑锦蛇甲状腺素(T4)含量与进食量的相关系数高于赤峰锦蛇和王锦蛇,而其饲料的转化率也高于后两者,其间存在的关系还需要深入研究。由上述结果可以看出,3种锦蛇促甲状腺激素释放激素(TRH)、促甲状腺激素(TSH)和甲状腺素(T4)含量和变化趋势有着明显的差别,且血清甲状腺素(T4)含量与蛇的进食量、生长和饲料转化率之间有密切的关系。     

养殖条件下3种锦蛇血细胞比较研究

为了掌握蛇在养殖状态下的血液学参数,对人工孵化繁育的棕黑锦蛇Elaphe schrenckii、赤峰锦蛇E.anomala和王锦蛇E.carinata进行了比较研究。观测的参数包括血细胞形态和大小、红细胞计数、白细胞计数和白细胞分类计数,以及血栓细胞计数。结果表明:3种蛇血细胞的形态、大小和数量各有不同,种间差异有统计学意义;其中王锦蛇的红细胞表面积和体积最大,数量最多;白细胞中淋巴细胞所占比例均为最高;除王锦蛇为嗜酸性粒细胞数量仅次于淋巴细胞外,其余2种蛇嗜中性粒细胞的数量在白细胞总数中所占比例仅次于淋巴细胞。特别的是王锦蛇的嗜酸性颗粒细胞和血栓细胞均高于其他2种锦蛇的2倍以上,而嗜中性颗粒细胞却只有其他2种锦蛇的一半。     

腹泻柴达木马亚成体粪便微生物多样性分析及其生物标记物的筛选

为比较青藏高原柴达木马亚成体腹泻与健康个体粪便微生物群落多样性和结构组成的差异, 我们利用16S rRNA测序技术对采集的腹泻 (n = 3) 和健康 (n = 13) 个体粪便样本细菌的组成与分布进行分析比较,并利用实时荧光定量PCR测定相关菌属的含量。结果显示,无论健康还是腹泻,厚壁菌门、拟杆菌门、疣微菌门、变形杆菌门和螺旋体门是柴达木马亚成体粪便中的优势菌门。相比健康组,腹泻组粪便微生物的Alpha多样性显著下降 (P < 0.05),厚壁菌门相对丰度下降而变形杆菌门的相对丰度显著增加 (P < 0.05),推断这两个门中的梭菌属、普雷沃菌属、纤杆菌属等丰度的失衡可能是导致柴达木马腹泻的原因之一。此外,通过机器学习的随机森林算法筛选出12个对健康和腹泻柴达木马亚成体粪便微生物差异具有较大影响的特征菌属,包括甲烷短杆菌属、纤杆菌属、Paludibacter、肉食杆菌属和迷踪菌属等。研究揭示了健康和腹泻柴达木马亚成体粪便微生物组的变化,为进一步研究青藏高原地区家畜腹泻提供一定的数据支持。     

脑卒中后抑郁症患者粪便微生物种群多样性和均衡性分析CSCD

目的分析脑卒中后抑郁症患者粪便中的微生物种群多样性和均衡性。方法选择我院2018年10月至2020年10月神经内科住院部收治的68例脑卒中后抑郁症患者为试验组。在同一时期选择我院体检中心的68例健康体检者作为对照组。采用第二代高通量测序技术对其粪便中的微生物种群多样性和均衡性进行分析。结果(1)两组对象粪便样本微生物种群Good′s Coverage指数差异无统计学意义(P>0.05),而试验组OTU种类、Chao 1指数和Ace指数高于对照组(均P<0.05)。(2)两组对象粪便样本微生物种群Shannon指数、Simpson指数和Evenness指数差异均无统计学意义(均P>0.05)。(3)两组对象粪便样本微生物种群均包括变形菌门、拟杆菌门、梭杆菌门以及厚壁菌门,其中试验组厚壁菌门相对丰度显著低于对照组,而其他3种菌门则高于对照组(均P<0.05)。(4)试验组患者粪便样本微生物种群理研菌科、氨基球菌科、梭杆菌科、Erigeronaceae、肠杆菌科和紫单胞菌科的相对丰度较高,而瘤胃菌科、普雷沃菌科、毛螺菌科以及单毒丝菌科的相对丰度较低(均P<0.05)。(5)在属水平上,试验组对象粪便样本微生物种群有11种菌属的相对丰度高于对照组,有3种菌属的相对丰度低于对照组(均P<0.05)。结论脑卒中后抑郁症患者粪便中微生物种群与健康人群存在较大差异。     

胃癌患者化疗前后口腔菌群与肠道菌群变化特征

目的研究胃癌患者化疗前后口腔菌群与肠道菌群的变化特征,为该类患者的治疗提供参考。方法选取2017年2月至2020年2月于我院接受治疗的96例胃癌患者为观察组,另外选取同期我院健康体检者90例为对照组,收集两组对象唾液样本和粪便样本,其中观察组患者需收集化疗前及化疗后两个时间点的样本。采用16S rRNA基因高通量测序法检测菌群构成,分析两组对象组间及观察组患者化疗前后口腔菌群与肠道菌群变化特征。结果化疗前,观察组患者唾液样本、粪便样本菌群Simpson指数、Shannon指数、厚壁菌门、拟杆菌门丰富度与对照组比较差异均无统计学意义(均P>0.05)。化疗前,观察组患者唾液样本及粪便样本中放线菌门丰富度显著高于对照组,变形菌门丰富度显著低于对照组(均P<0.05)。化疗后,观察组患者唾液样本中厚壁菌门、放线菌门、变形菌门丰富度较化疗前显著下降,拟杆菌门丰富度显著上升(均P<0.05);同时粪便样本中厚壁菌门、变形菌门丰富度较化疗前显著上升,拟杆菌门、放线菌门丰富度显著下降(均P<0.05)。化疗后,观察组患者唾液样本中韦荣球菌属、罗氏菌属、普氏菌属丰富度较化疗前显著增加,放线菌属、链球菌属、奈瑟菌属、粪梭杆菌属丰度显著下降(均P<0.05);同时粪便样本中链球菌属、肠志贺菌属、乳杆菌属丰富度较化疗前显著增加,粪梭杆菌属、双歧杆菌属、拟杆菌属丰富度显著下降(均P<0.05)。结论化疗对胃癌患者口腔菌群及肠道菌群构成有一定程度影响,患者口腔菌群中韦荣球菌属丰度上升,而肠道中正常菌群的生长受抑制。     

基于16S rRNA基因高通量测序的 太原地区健康成年人肠道菌群结构分析

目的探讨太原地区健康成年人的肠道菌群结构及多样性。方法采集太原地区20份健康成年人的粪便样本,提取DNA、构建菌群16S rRNA基因克隆文库、高通量测序并进行生物信息学分析。结果测序获得优质序列1 383 680条,平均序列为69 184条±551条,归类于455个OTUs;所有样本共含有10个菌门,101个菌属,141种菌;其中核心菌门3个,依次为拟杆菌门(63.13%)、厚壁菌门(31.14%)和变形菌门(5.10%),占所有样本微生物总量的99.37%;丰度最高的前10个菌属依次为拟杆菌属(43.34%)、普氏菌属(15.51%)、栖粪杆菌属(4.92%)、罗氏菌属(4.73%)、毛螺菌属(3.27%)、萨特菌属(2.50%)、粪球菌属(2.38%)、布劳特菌属(2.31%)、瘤胃球菌属(2.18%)和副杆状菌属(1.61%),占样本微生物总量的82.75%,未分类的菌属占6.84%。结论健康成年人肠道微生物群落复杂,但主要菌群相对稳定,为进一步研究人体肠道菌群结构与功能提供了参考依据。     

湿疹患儿肠道菌群高通量测序初步探索

目的为了解湿疹患儿肠道菌群的结构与湿疹之间的关系,通过对湿疹患儿和健康儿童粪便样本细菌总DNA提取,利用高通量测序技术,比较健康儿童和湿疹患儿肠道菌群的异同。方法 10例年龄在2个月~2岁婴幼儿由皮肤科门诊确诊为湿疹伴有过敏性疾病家族史作为研究对象,年龄和性别相当健康儿童10例作为对照,分别收集其粪便标本并提取所有样本中细菌的总DNA,对16SrRNA基因进行高通量测序,获得两组的肠道菌群结构数据并进行菌群差异性分析。结果通过Roche 454高通量测序,两组肠道微生物菌群多样性指数比较差异无统计学意义。两组主要由Firmicutes(厚壁菌门)、Bacteroidetes(拟杆菌门)、Proteobacteria(变形菌门)和Actinobacteria(放线菌门)4个门组成;两组在门水平上进行菌群结构比较,差异无统计学意义。两组样本在属水平上共获得200个不同属的细菌,其中Bacillus(芽孢杆菌属)、Bilophila(噬胆菌属)、Christensenella(纺锤状细菌属)、Coprobacillus、Eikenella(艾肯菌属)、Enterobacter(肠杆菌属)、Eubacterium(真杆菌属)、Lactococcus(乳球菌属)、Megamonas(巨单胞菌属)、Leuconostoc(明串珠菌属)、Morganella(摩根菌属)、Rhizobacter(根杆菌属)、Proteus(变形菌属)、Sutterella(萨特菌属)、Veillonella(韦荣球菌属)、Akkermansia、Anaeroglobus、Anaerotruncus、Butyricicoccus、Epulopiscium、Gordonibacter、Lachnospiraceae uncultured、Robinsoniella和Varibaculum共24个属在两组间差异具有统计学意义。结论湿疹患儿肠道菌群与健康儿童相比,菌群多样性指数(Shannon指数和Simpson指数)未见明显差异,但在菌群结构上发生了一些变化,某些特别的细菌菌属存在显著性差异。     

山西省东南部地区胃癌患者肠道菌群分布的配对病例对照研究

目的观察胃癌患者肠道菌群的变化,为研究其发病机制和治疗措施提供依据。方法按照1∶1配对原则(年龄、性别、民族、居住地等)在长治某医院根据胃镜检查结果分别选取尚未进行过治疗的10例胃癌患者(胃癌组)和10例健康人群(对照组),面对面调查填写基本信息表,留取粪便样本,采用微生物16S rDNA扩增子测定技术检测粪便菌群,使用QIIME2(2019.4)、R脚本等软件分析人群肠道菌群结构。结果胃癌组与对照组之间,肠道菌群多样性Chao1指数、Shannon指数、Simpson指数、Faith′s PD指数、Pielou′s evenness指数、Observed_species指数和Good′s coverage指数差异均无统计学意义(均P0.05),但距离矩阵与PCoA分析显示2组菌群分布差异存在统计学意义(P0.05)。在门水平上,2组粪便菌群都集中在厚壁菌门、拟杆菌门、放线菌门和变形菌门四类菌门上,胃癌组的变形菌门、梭杆菌门、互养菌门的丰度较对照组明显增加,差异有统计学意义(均P0.05)。在属水平上,胃癌组的乳杆菌属、克雷伯菌属、脱硫弧菌属、瘤胃球菌属的丰度较对照组明显增加,差异有统计学意义(均P0.05)。胃癌组瘤胃球菌科、Gemmiger和毛螺菌属的丰度较对照组明显减少,差异有统计学意义(均P0.05)。结论胃癌患者肠道菌群物种多样性和属的丰度发生了改变。     

老年阿尔茨海默病患者肠道微生态改变及其与认知功能的关系探讨

目的探讨老年阿尔茨海默症患者肠道微生态结构与认知功能的关系。方法将2016年7月-2019年5月医院收治的86例老年阿尔茨海默病患者和73例健康志愿者,分别记为研究组和对照组。采用简易精神状态评价量表(MMSE)进行评分评价两组认知功能,采用高通量测序检测两组肠道微生物多样性。比较两组肠道微生物多样性与MMSE评分,并比较研究组中认知功能正常者与障碍者肠道微生物结构;采用Pearson相关性分析法探讨肠道微生物结构与认知功能障碍者的相关性。结果研究组肠道菌群Chao1指数、Shannon指数、放线菌门、拟杆菌门、放线菌科、乳杆菌科、拟杆菌科、双歧杆菌属、乳杆菌属、拟杆菌属、MMSE评分均低于对照组(均P0.05);研究组厚壁菌门、变形菌门、子囊菌门、梭菌科、假单胞菌科、葡萄球菌科、肠杆菌科、隐球酵母科、梭状芽孢杆菌属、假单胞菌属、葡萄球菌属、变形杆菌属、假丝酵母菌属相对丰度均高于对照组(均P0.05);研究组中认知功能障碍发生率为70.93%,且认知功能障碍者肠道菌群Chao1指数、Shannon指数,门、科、属水平相对丰度与认知功能正常者对比和上述结果一致;研究组与对照组肠道拟杆菌门、子囊菌门、拟杆菌科、梭状芽胞杆菌属、假丝酵母菌属、放线菌门、乳杆菌属、拟杆菌属相对丰度差异具有统计学意义(均P0.05);研究组认知功能障碍与认知功能正常者肠道未分类拟杆菌门、子囊菌门、假单胞菌属、拟杆菌属、变形杆菌属、梭状芽孢杆菌属、拟杆菌门、拟杆菌科、假丝酵母菌属相对丰度差异具有统计学意义(均P0.05);研究组中肠道菌群Chao1指数、Shannon指数,放线菌门、拟杆菌门、放线菌科、乳杆菌科、拟杆菌科、双歧杆菌属、乳杆菌属、拟杆菌属相对丰度与MMSE评分均呈正相关,厚壁菌门、变形菌门、子囊菌门、梭菌科、假单胞菌科、葡萄球菌科、肠杆菌科、隐球酵母科、梭状芽孢杆菌属、假单胞菌属、葡萄球菌属、变形杆菌属、假丝酵母菌属相对丰度与MMSE评分均呈负相关。结论老年阿尔茨海默病患者肠道微生物结构存在异常,且认知功能障碍者更加严重,认知功能与肠道微生物相关。     

强直性脊柱炎患者咽部菌群变化

目的探讨强直性脊柱炎患者的咽部菌群变化。方法筛选入组7例强直性脊柱炎患者和7例健康者咽拭子样本,提取咽部DNA,扩增16SrRNA基因,在Illumina平台测序,对测序结果进行生物信息学分析。结果从ACE指数、Chao1指数、Shannon指数和Simpson指数综合来看强直性脊柱炎患者的咽部菌群Alpha多样性差异不大。Beta多样性分析显示两组研究对象咽部菌群样本可被区分。强直性脊柱炎患者咽部菌群组成和含量发生显著改变,主要变化包括:拟杆菌门(Bacteroidetes)和放线菌门(Actinobacteria)显著降低。拟杆菌门中普雷沃杆菌属(Prevotella)相关的纲目科属水平都显著降低。放线菌门变化落实到属水平,放线菌属(Actinomyces)显著降低,丙酸杆菌属(Propionibacterium)和棒状杆菌属(Corynebacterium)显著增高。厚壁菌门(Firmicutes)中,芽胞杆菌纲(Bacilli)所属的与链球菌属(Streptococcus)相关的纲目科属水平显著增加,而梭状芽胞杆菌纲(Clostridia)包含的韦荣球菌属(Veillonella)、消化球菌属(Peptococcus)显著下降。此外,变形菌门中出现弧菌属(Vibrio)的增加和弯曲菌属(Campylobacter)的降低等变化。结论强直性脊柱炎患者(本次研究样本)的咽部菌群出现紊乱,以普雷沃杆菌属、放线菌属、韦荣球菌属、消化球菌属和弯曲菌属等显著降低,丙酸杆菌属、棒状杆菌属、链球菌属和弧菌属等显著增加为主要特征。     

六种藓类植物茎的比较解剖学研究

通过对6种藓类植物,即褶叶青藓(Brachythecium salebrosum(Web.et Mohr.)B.S.G.)、湿地匐灯藓(Plagiomnium acutum(Lindb.)Kop.)、侧枝匐灯藓(Plagiomnium maximoviczii(Lindb.)Kop.)、大凤尾藓(Fissidensnobilis Griff.)、大羽藓(Thuidium cymbifolium(Doz.et Molk.)B.S.G.)和大灰藓(Hypnum plumaeforme Wils.)嫩茎和老茎的石蜡切片和显微观察发现,同一藓类植株的嫩茎和老茎,茎结构稳定,不同种藓类植物茎横切面具有不同特征.植物体茎横切面形状、表层细胞的层数、细胞大小和细胞壁厚薄、皮层细胞大小和形状、中轴的有无以及比例等特征可以作为藓类植物的分科分类依据之一.     

Photoregulation of seed germination of wild-type and of an aurea-mutant of tomato

Seed germination of an aurea mutant of tomato ( Lycopersicon esculentum Mill.) is promoted by continuous irradiation with red, far-red or long-wavelength far-red (758 nm) light as well as by cyclic irradiations (5 min red or 5 min far-red/25 min darkness). Far-red light applied immediately after each red does not change the germination behaviour. Seed germination of the isogenic wild-type, cv. UC-105, is promoted by continuous and cyclic red light while it is inhibited by continuous and cyclic far-red light and by continious 758 nm irradiation. Far-red irradiation reverses almost completely the promoting effect of red light. The promoting effect (in the aurea mutant) and the inhibitory effect (in the wild-type) of continuous far-red light do not show photon fluence rate dependency above 20 nmol m⁻² s⁻¹. It is concluded that phytochrome controls tomato seed germination throgh low energy responses in both the wild type and the au mutant. The promoting effect of continuous and cyclic far-red light in the au mutant can be attributed to a greater sensitivity to P_fr.     

Cause of Senescence of Nine Sorts of Flowers

The levels of endogenous phytohormones and respiratory rate in nine sorts of flowers such as Cymbidium faberi Rolfe, Nopalxochia ackermannii Kunth and others were investigated both at full bloom and senescence and meanwhile the effect of exogenous phytohormones on prolonging the blossoms and promoting ethylene production were tested. There is a high content of endogenous ethylene in all the long-lived flowere, about 3–16 folds higer than the short-lived ones. There is a high level of ABA at full blooming flowers of short-lived flowers, in which there is no or only some cytokinins in it, but the ratio of CTK (6BA+zeatin)/ABA is smaller(l.7). The endogenous ABA reached a much higher level at senescence in all nine sorts of flowers, so it is reasonable to consider that it is ABA which plays an important role of regulation in controlling flower's senescence. There is a much higher level of GA3 and zeatin in the long-lived flowers which is not demonstrated in the shortlived ones. The respiratory rate is one of the factors controtling the longevity of flowers, but it does not play a decided role. Application of 6BA and zeatin prolongs distinctly orchid’s longevity, however exogenous IAA through the promotive action on ethylene production, evidently extends the longevity of the flowers of the Nopalxochia ackermannii Kunth.     

龙胆科药用植物化学成分的研究现状

龙胆科植物在我国的分布范围很广,且多数为药用植物,其多数种属的药用植物,至今其化学成分尚未被系统研究。综述了目前龙胆科药用植物的化学成分的研究现状及一般提取方法,对近年来发现的环烯醚萜及裂环烯醚萜类化合物进行了总结,为本科药用植物的更深入研究提供了参考。     

Interconnection of parameters of regulation system of lipid peroxidation and of morphophysiological parameters of mouse liver

A complex analysis of seasonal fluctuations of the mean group parameters of the system of regulation of lipid peroxidation has been performed in liver of Balb/c mice. Association of lipid characteristics and morphophysiological parameters is studied in the Balb/c mouse liver. An inter-connection is revealed between the liver index and the amount of lysoforms of phospholipids, the scale and character of the interconnection differing essentially depending on proportion of phos-phatidylcholine in mouse liver phospholipids.     

The effects of glutamine of the maintenance of embryogenic cultures of Cryptomeria japonica

Summary Embryogenic tissues of sugi (Cryptomeria japonica) were induced on a modified Campbell and Durzan (CD) medium containing 1 μM 2,4-dichlorophenoxyacetic acid (2,4-D) and 600 mg l⁻¹ glutamine, and subcultured in the medium of the same composition for over 1 yr. This resulted in a mixed culture of embryogenic and non-embryogenic cells. When embryogenic cells were isolated and cultured independently, their capacity to form embryogenic aggregates was lost. Thus, the non-embryogenic cells present within a mixed culture system were essential to the formation of embryogenic aggregates. When embryogenic tissues were isolated and cultured independently on a high glutamine-containing (2400 mg l⁻¹) medium, dry weights and endogenous levels of glutamine increased, and the tissue could generate a large number of embryogenic aggregates. Amino acid analysis of embryogenic and non-embryogenic cells from the maintenance culture indicated a higher level of glutamine was present in the latter. The high endogenous level of glutamine in the non-embryogenic portion of mixed cell masses may be the supplier of glutamine for maintaining the embryogenic property of the tissues.     

Specificity of action of piperidylcholine derivatives as substrates of cholinesterases of various origin

The review deals with study of enzymologic properties of a novel highly specific acetylcholinesterase substrate, N-(β-acetoxyethyl) piperidinium iodomethylate (“piperidylcholine”), and its 30 derivatives that were tested as effectors of cholinesterases of mammals and various species of Pacific squids. It was proven for the first time that responsible for specificity of action was structure of cyclic ammonium grouping of the alcohol part of molecule of the ester substrate. Analysis of specificity is performed based on enzymatic hydrolysis parameters—activity of catalytic center of cholinesterases and bimolecular constant of the reaction rate that are determined at optimal and low substrate concentrations. Among the specially synthesized group of thioester compounds there is revealed one more highly specific acetylcholinesterase substrate—N-(β-acetoxyethyl) piperidinium.     

Physiological characteristics of various species of strains of carboxydobacteria

Seven strains of aerobic carbon monoxide-oxidizing bacteria (carboxydebacteria) when growing on CO as sole source of carbon and energy had doubling times which ranged from 12–42 h. The activity profiles obtained after discontinuous sucrose density gradient centrifugation indicated that the CO-oxidizing enzymes are soluble and the hydrogenases are membrane-bound in all strains examined. The CO-oxidizing enzymes of Pseudomonas carboxydohydrogena, Pseudomonas carboxydoflava, Comamonas compransoris, and the so far unidentified strains OM2, OM3, and OM4 had a molecular weight of 230,000; that of Achromobacter carboxydus amounted to 170,000. The molecular weights of the CO-oxidizing and H₂-oxidizing enzymes turned out to be identical. The cell sonicates were shown to catalyze the oxidation of both CO and H₂ with methylene blue, thionine, phenazine methosulfate, toluylene blue, dichlorophenolindophenol, cytochrome c or ferricyanide as electron acceptors. Methyl viologen, benzyl viologen, FAD⁺, FMN⁺, and NAD(P)⁺ were not reduced. The spectrum of electron acceptors was identical for all strains tested. Neither free formate, hydrogen nor oxygen gas were involved in the CO-oxidation reaction. Methylene blue was reduced by CO at a 1:1 molar ratio. The results indicate that CO-oxidation by carboxydobacteria is catalyzed by identical or similar enzymes and that the reaction obeys the equation CO+H₂OCO₂+2H⁺+2e^- as previously shown for Pseudomonas carboxydovorans.Dedicated to Otto Kandler remembering almost three decades of enjoyable cooperation     

Modulation of allostery of pyruvate kinase by shifting of an ensemble of microstates

Since the introduction of the concepts of allostery about four decades ago, much advancement has been made in elucidating the structure-function correlation in allostery. However, there are still a number of issues that remain unresolved. In this review we used mammalian pyruvate kinase (PK) as a model system to understand the role of protein dynamics in modulating cooperativity. PK has a triosephosphate isomerase (TIM)(α/β)₈ barrel structural motif. PK is an ideal system to address basic questions regarding regulatory mechanisms about this common (α/β)₈ structural motif. The simplest model accounting for all of the solution thermodynamic and kinetic data on ligand-enzyme interactions involves two conformational states, inactive E^T and active E^R. These conformational states are represented by domain movements. Further studies provide the first evidence for a differential effect of ligand binding on the dynamics of the structural elements, not major secondary structural changes. These data are consistent with our model that allosteric regulation of PK is the consequence of perturbation of the distribution of an ensemble of states in which the inactive E^T and active E^R represent the two extreme end states. Sequence differences and ligands can modulate the distribution of states leading to alterations of functions. The future work includes: defining the network of functionally connected residues; elucidating the chemical principles governing the sequence differences which affect functions; and probing the nature of mutations on the stability of the secondary structural elements, which in turn modulate allostery.