血清PCT、CRP及内毒素在细菌性血流感染所致脓毒症患者中的早期诊断价值

目的:探究血清降钙素原(PCT)、C反应蛋白(CRP)及内毒素在革兰阳性(G+)杆菌与革兰阴性(G-)球菌血流感染所致脓毒症患者中的早期诊断价值。方法:回顾性分析2010年5月~2015年5月期间我院收治确诊的细菌性血流感染所致脓毒症患者123例,测定其血清PCT、CRP及内毒素水平,通过受试者工作特征曲线(ROC)曲线探究三者对细菌性血流感染所致脓毒症的评估价值。结果:血样培养结果显示,35例患者感染G+菌,88例患者感染G-菌;G-菌组患者血清PCT、CRP及内毒素水平均显著高于G+菌组(P0.05);且G+菌组、G-菌组及所有细菌组患者血清PCT、CRP、内毒素间均呈正相关关系(P0.05);ROC曲线显示,血清PCT、CRP和内毒素诊断G+菌血流感染所致脓毒症患者的截断值分别为1.58μg/L、95.25 mg/L与16.71ng/L,其灵敏度和特异度别为(65.92%,88.37%)、(67.39%,84.38%)与(56.34%,78.93%),诊断G-菌血流感染所致脓毒症患者的截断值分别为2.45μg/L、79.45 mg/L与15.54 ng/L,其灵敏度和特异度别为(78.73%,97.13%)、(68.89%,92.38%)与(65.39%,95.33%)。结论:检测血清PCT、CRP、内毒素水平有利于鉴别G-菌和G+菌血流感染所致脓毒症患者,且敏感度、特异度均较高,可用于早期诊断细菌性血流感染所致脓毒症。     

血清PCT、CRP及内毒素在细菌性血流感染所致脓毒症患者中的早期诊断价值

目的:探究血清降钙素原(PCT)、C反应蛋白(CRP)及内毒素在细菌性血流感染所致脓毒症患者中的早期诊断价值。方法:回顾性分析2010年5月~2015年5月期间我院收治确诊的细菌性血流感染所致脓毒症患者123例,测定其血清PCT、CRP及内毒素水平,通过受试者工作特征曲线(ROC)曲线探究三者对细菌性血流感染所致脓毒症的诊断价值。结果:血样培养结果显示,123例细菌性血流感染所致脓毒症患者中存在感染G+菌35例,感染G-菌88例;G+菌组的血清PCT、CRP及内毒素水平明显低于G-菌组(P0.05);且G+菌组、G-菌组及所有细菌组患者三指标两两间均呈正相关关系(P0.05);ROC曲线显示,血清PCT、CRP和内毒素预测G+菌血流感染所致脓毒症患者的临界值分别为1.58μg/L、95.25 mg/L与16.71 ng/L,其灵敏度和特异度别为(65.92%,88.37%)、(67.39%,84.38%)与(56.34%,78.93%),预测G-菌血流感染所致脓毒症患者的临界值分别为2.45μg/L、79.45mg/L与15.54 ng/L,其灵敏度和特异度别为(78.73%,97.13%)、(68.89%,92.38%)与(65.39%,95.33%)。结论:检测血清PCT、CRP、内毒素水平有利于鉴别G-菌和G+菌血流感染所致脓毒症患者,且敏感度、特异度均较高,可用于早期诊断细菌性血流感染所致脓毒症。     

降钙素原在鉴别诊断新生儿凝固酶阴性葡萄球菌血流感染与污染的应用价值

目的探讨血清降钙素原(PCT)对新生儿凝固酶阴性葡萄球菌(CoNS)血流感染与污染的临床鉴别诊断价值。方法回顾性分析东南大学附属中大医院2012年2月至2015年2月血培养CoNS阳性新生儿的临床资料,比较血流感染组和污染组患儿病例的一般人口学特征、PCT、C-反应蛋白(CRP)和血培养阳性报警时间(TTP)等结果,并根据ROC曲线分析PCT和CRP对两者的鉴别诊断价值。结果共112例CoNS阳性患儿纳入研究,其中血流感染组52例和污染组60例,两组患儿胎龄和性别差异均无统计学意义(P0.05);血流感染组患儿PCT和CRP水平明显高于污染组(Z=-7.135,P=0.000和Z=-3.065,P=0.002),血流感染组TTP平均值低于污染组(Z=-6.899,P=0.000);早发型败血症患儿人数明显多于晚发型败血症患儿(P=0.04);CoNS阳性血流感染组和污染组各菌种分布之间无统计学差异(P0.05);以PCT0.52ng/mL作为鉴别新生儿CoNS阳性血流感染及污染的最佳截断值时,其敏感性、特异度、阳性预期值和阴性预期值分别为84.9%、88.5%、86.5%和90.0%,ROC曲线下面积(AUC)为0.893[95%CI(0.82,0.95)];以CRP8.0mg/mL作为鉴别诊断新生儿CoNS阳性血流感染与污染的临界值时,其准确度较低。结论 PCT不失为一项值得推荐的鉴别诊断新生儿CoNS血流感染与污染的指标。综合分析新生儿PCT和其他临床特征,将有助于更好地指导临床医生合理使用抗菌药物。     

糖尿病合并尿路感染患者尿液降钙素原水平及其临床意义

目的:探讨糖尿病合并尿路感染患者尿液降钙素原(PCT)水平及其临床意义。方法:选取2017年8月至2018年12月中山大学附属第五医院内分泌与代谢病科收治的糖尿病患者78例,以其中合并真性细菌尿者39例作为观察组,未合并尿路感染39例作为对照组,比较两组患者的临床资料以及相关实验室检查结果,同时留取尿液标本,观察组分别留取使用抗生素治疗前、后的尿液标本。采用酶联免疫吸附测定(ELISA)法检测尿液PCT浓度。分别比较观察组与对照组以及观察组治疗前后的尿液PCT水平,分析尿液PCT水平对于诊断糖尿病合并尿路感染的临床价值。结果:观察组尿液PCT水平为0.030 (0.025,0.039) ng/m L,明显高于对照组0.017 (0.011,0.021) ng/m L(P0.05);观察组有症状尿路感染与无症状细菌尿(ABU)的尿液PCT水平比较差异无统计学意义(P0.05),但其均显著高于对照组(P0.05);观察组使用抗生素治疗后的尿液PCT水平为0.031 (0.025,0.040) ng/mL,与治疗前相比较差异无统计学意义(P0.05)。尿液PCT对糖尿病合并尿路感染诊断的敏感度为82.05%,特异度为79.49%,阳性预测值为80.00%,阴性预测值81.58%,ROC曲线下面积为0.81 (95%CI为0.71-0.89, P0.0001)。结论:尿液PCT水平对糖尿病合并尿路感染有一定的诊断参考价值,但对于抗生素疗效的评估价值还需进一步深入研究。     

血清降钙素原水平对血流感染患者病原菌的诊断价值

探讨血清降钙素原(PCT)水平对不同病原菌血流感染的诊断价值。选取2015年7月~2016年7月我院收治的血培养阳性的血流感染患者77例,其中革兰氏阳性菌感染41例(53.25%),革兰氏阴性菌感染36例(46.75%)。检测患者的PCT水平,绘制ROC曲线,计算曲线下面积(AUC)。革兰氏阳性菌组的血清PCT水平明显低于革兰氏阴性菌组,(0.62±0.17)ng/m L vs(12.87±3.43)ng/m L,差异具有统计学意义(t=2.193,p0.05);血清PCT区分革兰氏阳性和阴性菌的诊断价值较高(ACU=0.759),最佳阈值为4.45 ng/L。当血清PCT水平4.45 ng/L时诊断革兰氏阴性菌感染的敏感度、特异度和准确度分别为80.34%、86.91%、88.14%,阳性预测值92.1%,阴性预测值84.9%。在革兰氏阴性菌中,大肠埃希菌组的血清PCT水平明显高于鲍氏不动杆菌组,鲍氏不动杆菌组明显高于肺炎克雷伯菌组,差异具有统计学意义(p0.05);在革兰氏阳性菌中,金黄色葡萄球菌组的血清PCT水平明显高于肠球菌属组,肠球菌属组明显高于酿脓链球菌组,差异具有统计学意义(p0.05)。不同病原菌血流感染患者的血清PCT水平存在差异,血清PCT水平对早期区分革兰氏阳性菌和阴性菌感染具有较高的诊断价值。     

血清SAA、YKL-40及SP-A的联合检测对小儿难治性肺炎支原体肺炎的预测价值分析

摘要 目的：探究血清淀粉样蛋白A（SAA）、几丁质酶样蛋白YKL-40和肺表面活性物质相关蛋白-A（SP-A）表达水平对的联合检测对小儿难治性肺炎支原体肺炎（RMPP）的预测价值。方法：纳入2019年11月至2021年12月期间我院收治的60例MPP患儿作为研究对象,依据病情最终转归将其分为RMPP组和普通肺炎支原体肺炎（GMPP）组,另纳入同期于我院行体格检查的60例健康儿童作为对照组。收集所有受试儿童的临床资料、实验室指标及影像学结果,采用酶联免疫吸附法（ELISA）检测血清SAA、YKL-40和SP-A的表达水平,应用受试者工作特征曲线（ROC）判定各指标单项检测和联合检测的预测效能。结果：MPP组患儿和对照组儿童一般资料相比无统计学差异（P＞0.05）。依据病情最终转归,60例MPP患儿中共有23例（38.33 %）进展为RMPP,RMPP组与GMPP组患儿在白介素-6（IL-6）、C-反应蛋白（CRP）、降钙素原（PCT）、D-二聚体（D-D）等实验室指标以及肺不张、胸腔积液等影像学特征方面相比有统计学差异（P＜0.05）。RMPP组和GMPP组血清SAA、YKL-40和SP-A的表达水平显著高于对照组（P＜0.05）,同时RMPP组血清SAA、YKL-40和SP-A的表达水平显著高于GMPP组（P＜0.05）。血清SAA的最佳截断值为39.75 mg/L,预测RMPP发生的ROC曲线下面积为0.894（95%CI：0.861-0.925）,敏感度为78.26 %,特异度为86.67 %;血清YKL-40的最佳截断值为31.85 ng/mL,预测RMPP发生的ROC曲线下面积为0.754（95%CI：0.634-0.873）,敏感度为73.91 %,特异度为67.21 %;血清SP-A的最佳截断值为35.59 ng/mL,预测RMPP发生的ROC曲线下面积为0.761（95%CI：0.640-0.891）,敏感度为73.91 %,特异度为75.00 %;SAA+YKL-40-1+SP-A三者联合检测预测RMPP的AUC为0.914（95%CI：0.871-0.957）,敏感度为91.30 %,特异度为91.66 %。结论：血清SAA、YKL-40和SP-A表达水平的检测可作为预测RMPP发生的重要生物学指标,且三者联合检测的预测效能较高,可为临床尽早诊断RMPP、尽早干预、改善患儿预后提供一定的帮助。     

两种血清隐球菌荚膜多糖抗原检测方法在肺隐球菌病中的应用研究

目的探讨并比较血清酶联免疫分析法(ELISA)和侧流免疫层析法(LFA)检测血清隐球菌荚膜多糖抗原(CrAg)在肺隐球菌病(PC)中的应用价值。方法采集2016年1月～2018年6月福建省福州肺科医院109例疑似PC患者的血液,采用ELISA和LFA两种方法对血清CrAg进行检测,对比分析两种方法对PC的诊断效率,同时监测治疗过程中血清CrAg的浓度变化。结果 109例患者中,经肺活检或肺穿刺液隐球菌检测确诊为PC53例,非PC56例,检验结果如下:(1)应用ELISA方法,PC组血清CrAg浓度为[11.43(5.92,47.96)]μg/L,其中CrAg≤3.2μg/L的例数明显低于非PC组,而CrAg≥5.0μg/L的例数则明显高于非PC组,两者比较差异均有统计学意义(均P0.05)。应用LFA方法,PC组血清CrAg检测阳性率明显高于非PC组,两者比较差异有统计学意义(P0.05)。(2)应用ROC曲线分析显示,ELISA检测血清CrAg的曲线下面积为0.939(95%可信区间为0.892～0.985)。其中截断值取3.54μg/L时约登指数最高,视为最佳截断值,对应的敏感度、特异度、阳性预测值及阴性预测值分别为94.3%、80.4%、82.0%和93.8%。(3)当血清CrAg取4.0μg/L为截断值时,ELISA和LFA的诊断敏感度(88.7%和83.0%)两者比较差异无统计学差异(P0.05),但ELISA特异度(82.1%)明显低于LFA(98.2%),两者比较差异有统计学意义(P0.05)。当截断值分别取5.0μg/L、6.0μg/L和7.0μg/L时,ELISA和LFA的诊断敏感度及特异度相当(均P0.05)。当取8.0μg/L为截断值时,ELISA的诊断敏感度(62.3%)明显低于LFA(83.0%),两者比较差异有统计学意义(P0.05),但特异度(100%和98.2%)两者大致相仿(P0.05)。(4)14例患者在抗真菌治疗过程中监测血清CrAg的浓度变化,治疗前荚膜抗原浓度为[19.33(7.11,43.46)]μg/L,治疗后6个月荚膜抗原浓度为[8.09(5.39,11.90)]μg/L,较前明显下降,两者比较差异有统计学意义(P0.05)。结论血清CrAg浓度为3.54μg/L时视为ELISA的最佳截断值,但当取5.0μg/L为截断值时,ELISA同时有较好的诊断敏感度和特异度,且和LFA的诊断效率相当,两种方法均有助于对PC的快速诊断,值得临床推广。与LFA定性检测相比,ELISA可动态监测血清CrAg的浓度变化,有助于PC的疗效判断和预后评估。     

白细胞介素-39联合降钙素原评估脓毒症严重程度的临床价值

摘要 目的：探讨白细胞介素-39（Interleukin-39, IL-39）联合降钙素原 （Procalcitonin, PCT）对脓毒症严重程度的评估价值。方法：随机选取2019年12月至2020年12月上海交通大学医学院附属新华医院及瑞金医院因感染入院患者100例,分为非脓毒症组、脓毒症组和脓毒症休克组,根据28天内脓毒症患者是否死亡,分为死亡组和存活组,另纳入40例健康人为对照组。测量患者入院24小时内的IL-39及PCT水平,绘制受试者工作特征曲线（Receiver operating characteristic curve, ROC）分析IL-39、PCT 及二者联合对脓毒症患者病情严重程度的评估价值。结果：所有感染组IL-39、PCT水平均高于健康对照组,且随着病情严重程度的增加而升高,从低到高的顺序为健康对照组<非脓毒症组<脓毒症组<脓毒症休克组,死亡组患者IL-39、PCT水平高于存活组;ROC曲线分析IL-39和PCT以及二者联合对预测脓毒症休克的曲线下面积（Area under curve, AUC）为0.776,0.794,0.866,灵敏度为81.0 %,61.9 %,90.5 %,特异度为74.4 %,84.6 %,66.7 %,约登（Youden）指数分别为0.5531,0.4652,0.5714,截断值分别为115.05 pg/mL,33.18 ng/mL;ROC曲线分析IL-39和PCT以及二者联合预测患者死亡的价值,AUC为0.798,0.774,0.868,灵敏度为90.9 %,54.6 %,90.9 %,特异度为65.3 %,87.8 %,79.6 %,Youden指数分别为0.5622,0.4230,0.7050,截断值分别为115.05 pg/mL,46.59 ng/mL。结论：IL-39联合PCT评估脓毒症严重程度的临床价值,优于PCT单项预测,检测IL-39水平有助于脓毒症病情的早期评判。     

PCT与IL-6联合检测鉴别诊断脓毒性和非脓毒性全身炎症反应综合征的临床价值

目的:探讨降钙素原(PCT)与白细胞介素-6(IL-6)联合检测鉴别诊断ICU患者脓毒性和非脓毒性全身炎症反应综合征(SIRS)的临床价值。方法:选择2013年~2016年入住我院ICU的100例患者,包括61例非脓毒性SIRS患者与39例脓毒症患者,同时选择同期50例健康者作对照,分别设为非脓毒性组、脓毒血症组及对照组,采用电化学发光分析法检测三组血清PCT与IL-6水平,并以PCT为2μg/L和IL-6为50 ng/L为临界值来鉴别非感染性SIRS和脓毒血症,评价联合检测的临床诊断价值。结果:非脓毒性组PCT与IL-6最大值分别为0.91±0.54μg/L、62.77±11.75 ng/L,脓毒血症组为24.49±5.00μg/L、1542.69±361.66 ng/L,对照组为0.08±0.06μg/L、3.68±1.11 ng/L,非脓毒性组与脓毒血症组PCT与IL-6最大值均显著高于对照组(P0.05);与非脓毒性组比较,脓毒血症组PCT与IL-6均显著升高(P0.05)。非脓毒性组PCT2μg/L、IL-650 ng/L的占比分别为21.31%、65.57%,脓毒血症组为92.31%、87.18%,脓毒血症组PCT2μg/L、IL-650 ng/L的占比均显著提高于非脓毒性组(P0.05)。PCT的阳性预期值、灵敏度、特异度均显著高于IL-6,而联合检测的阳性预期值、特异度显著高于IL-6及PCT,联合检测的灵敏度显著高于IL-6,P均0.05。结论:PCT与IL-6联合检测有助于脓毒性和非脓毒性SIRS的鉴别诊断。     

负压封闭引流技术联合前列地尔注射液对重度烧伤患者的疗效观察

目的:研究负压封闭引流技术联合前列地尔注射液对重度烧伤患者的疗效观察。方法:选取2017年2月至2018年2月的67例患者。按照随机数表法分为观察组(n=36)和对照组(n=31),对照组采用负压封闭引流技术治疗,观察组采用负压封闭引流技术联合前列地尔注射液治疗。观察两组治疗疗效情况,临床治疗指标(创面愈合时间、创面愈合率、VAS评分、住院时间),C反应蛋白(CRP)、降钙素原(PCT)水平,不良反应发生率。结果:治疗后,观察组总有效率显著高于对照组[86.11%(31/36)vs 61.29%(19/31)](P0.05);创面愈合时间、创面愈合率、VAS评分、住院时间均显著低于对照组[(16.93±4.19)天vs(24.27±6.01)天,(92.72±5.03)%vs(81.34±2.48)%,(2.93±0.52)分vs(6.70±1.30)分,(24.09±7.43)天vs(46.98±10.72)天](P0.05);CRP、PCT水平均显著低于对照组[(27.93±3.81)mg/L vs(83.86±7.43)mg/L,(0.10±0.02)ng/L vs(0.43±0.06)ng/L](P0.05);不良反应总发生率显著低于对照组[8.33%(3/36)vs 38.70%(12/31)](P0.05)。结论:负压封闭引流技术联合前列地尔注射液对重度烧伤患者的疗效显著,可促进创面恢复,避免感染,并发症少,安全可靠。     

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.     

真菌类遗传学分析的知识结构教学

本文以认知结构理论为指导,讨论了真菌类遗传分析与高等动植物遗传分析的内在联系,认为利用这种内在联系进行教学可收到好的效果并说明了作者的具体教学过程。 Abstract:In the paper, the relationship between genetic analysis of Fungi and genetic analysis of high animal and plant was discussed.A good results were obtained when we adopted this method in the teaching.     

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.     

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.     

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。     

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.