葡萄糖代神经氨酸体外抑制钙调蛋白活性

三种唾液酸亚型５－乙酰神经氨酸、５，９－二乙酰神经氨酸和葡萄糖代神经氨酸皆从小鼠肿瘤腹水中通过阴离子交换树脂法获得，葡萄糖代神经氨酸体外显示抗钙调蛋白活性，另两种亚型在１０μｇ／ｍｌ浓度下仍不显示该生物活性。     

生物体中的乙酰羟酸还原异构酶

乙酰羟酸还原异构酶是植物、微生物中的支链氨基酸生物合成过程中的一种重要酶，该酶是由两个相同单体组成的同源二聚体，催化乙酰羟酸到α、β-二羟酶的反应，反应中需要NADPH和二价金属离子作辅助因子，酶的活性受到支链氨基酸合成途径中间产物类似物的抑制。     

多聚唾液酸转移酶ST8SiaⅡ的结构和功能域

ST8SiaⅡ(STX)和ST8SiaⅣ(PST)是两个来源于哺乳动物细胞的、具有高度同源性的多聚唾液酸酶,它们已经被克隆,基因序列也已被测定。这两个酶能催化神经细胞黏附分子(NCAM)的多聚唾液酸化。NCAM是多聚唾液酸(polySlA)的主要载体。在NCAM多聚唾液酸化过程中,STX和PST能将活化的胞苷-磷酸-乙酰神经氨酸(CMP-Neu5Ac)传送到NCAM糖蛋白受体的N-和O-型寡聚糖链上,从而合成α-2,8-多唾液酸聚糖(polySA)。近来我们使用Phyre 2软件构建了多聚唾液酸ST8SiaⅡ酶的三维结构模型,给出了该酶中多聚唾液酸转移酶结构域(PSTD)和多聚碱性氨基酸区域(PBR)两个功能域的结构特征,认为在这两个区域中有几个氨基酸残基在引起多聚唾液酸化过程中起到了关键作用。我们的研究结果为研究ST8SiaⅡ酶催化NCAM多聚唾液酸化的分子机制提供了新的结构信息,也为和该酶所联系的肿瘤细胞转移的抑制机制和抑制物/药物的研究和设计,提供更有价值的理论依据。     

南美白对虾血蓝蛋白血细胞凝集活性初探

以采自汕头的南美白对虾为研究对象,采用亲和层析、PAGE、SDS-PAGE、Western-blotting、血细胞凝集实验和糖抑制实验等方法探索南美白对虾血蓝蛋白的血细胞凝集活性.结果发现,血蓝蛋白对实验所选用的鱼、鸡、鼠和人等4种红细胞均具有显著的血细胞凝集活性,凝集活性大小为5~10mg/L,而且其凝集反应可被α-半乳糖、-αD葡萄糖、甘露醇和N-乙酰神经氨酸等4种糖所显著抑制.由此推测,血蓝蛋白确实具有血细胞凝集活性,这对进一步研究血蓝蛋白的免疫学功能具有重要意义.     

甜菊钙调蛋白基因的克隆及结构分析

钙调蛋白（Calmodulin）是生物细胞内一种重要的调控蛋白，通过其与靶酶的相互作用控制细胞正常的生长发育及细胞对外界环境变化的反应，我们从甜菊顶芽和花芽中提取总RNA，逆转录合成cDNA第一链，以此为模板，参考GenBank上已发表植物的钙调蛋白基因序列合成5′端和3′端引物，利用多聚酶链式反应（PCR）扩增并克隆得到了甜菊钙调蛋白基因的两个异型基因，序列分析表明，它们均由450个核苷酸组成，编码148个氨基酸，在核苷酸序列上与迄今已知的多种植物钙调蛋白均有很高的同源性，同源率在83％以上，编码的氨基酸序列同源性更同，同源率高达95％以上，这两个基因之间存在差异，其核苷酸序列同源率为85％，编码区的氨基酸序列的同源率为99％，仅在第122个氨基酸由ALA代替了VAL。     

维生素D及其研究进展

维生素Ｄ（ＶＤ）广泛存在于动植物中。内源性及外源性的ＶＤ经血液循环至肝，在肝细胞微粒体内２５－羟化酶作用下形成２５－羟骨化醇［２５（ＯＨ）Ｄ］，再经血转运至肾，在肾１α－羟化酶作用下，最终形成１，２５－二羟骨化醇［１，２５（ＯＨ）２Ｄ］，成为具有最大生物活性的ＶＤ代谢产物，ＶＤ作为一种内分泌激素，有着广泛的生物效应，主要参与钙、磷代谢的调节作用。２５（ＯＨ）Ｄ是ＶＤ在体内的主要循环形式，它反映体内ＶＤ的代谢状态，一般儿童正常值为２５（ＯＨ）Ｄ１５～３５ｎｇ／ｍｌ，１，２５（ＯＨ）２Ｄ３０～６０ｐ…     

黄芪多糖对P_（388）小鼠红细胞免疫促进作用的机制研究

研究了黄芪多糖（ＡＰＳ）对淋巴白血病Ｐ＿（３８８）小鼠红细胞膜功能的影响。研究结果表明，ＡＰＳ（１０～４０ｍｇ／ｋｇ）可显著增加Ｐ３８８小鼠红细胞免疫功能，显著升高红细胞Ｃ３ｂ受体花环率（ＲＢＣ—Ｃ３ｂＲＲ）、红细胞Ｃ３ｂ受体花环促进率（ＲＦＥＲ），同时可降低红细胞免疫复合物花环率（ＲＢ—ＩＣＲＲ）、红细胞Ｃ３ｂ。受体花环抑制率（ＲＦＩＲ）。研究结果还表明，ＡＰＳ增强淋巴白血病Ｐ３８８。小鼠红细胞免疫功能的机制与ＡＰＳ降低Ｐ３８８小鼠红细胞膜过氧化脂质（工ＰＯ）含量、抑制红细胞膜蛋白与收缩蛋白交联高聚物（ＨＭＰ）的形成、增加红细胞膜封闭度、唾液酸含量、增强红细胞膜超氧化物歧化酶（ＳＯＤ）、过氧化氢酶（ＣＡＴ）、钠，钾—三磷酸腺苷酶（Ｎａ＋，Ｋ＋－ＡＴＰａｓｅ）活性有关。     

UV照射下药物对红细胞和脂过氧化的影响

5,3′,5′-三羟基-7甲氧基二氢黄酮(TDF)及谷氨酸钠均能抑制UV 引起的黄鳝离体红细胞血红蛋白的释出,UV 照射引起黄鳝肝脏匀浆脂质过氧化物的增高,并随着照射时间的延长而有所上升,TDF一定的浓度能抑制UY 照射所引起的黄鳝肝脏匀浆脂质过氧化物的增高,谷氨酸钠在本实验中对脂过氧化未显示其抑制作用.     

C—反应蛋白在脂单层膜上二维晶体组装及结构…

本文通过特异性结合和非特异性静电吸附两种途径在脂单层膜表面获得了兔Ｃ－反应蛋白的二维晶体。通过对负染样品的电镜观察和图象处理得到蛋白的二维投影密度图，分辨率达到２．２ｎｍ。分析表明，只有Ｃ－反应蛋白的亚单位在膜表面形成了二维晶体，且由于形成二维晶体的原理不同，两种二维晶体中的亚单位的在膜表面的取向是不同的。通过比较我们不仅得到了Ｃ－反应蛋白的亚单位的形状，而且建立了５个亚单位的可能的聚合模型。     

番茄碱对人细胞膜Ca^2＋—Mg^2＋ATPase活性影响的初步研究

本研究了番茄碱对人红细胞膜Ｃａ＾２＋－Ｍｇ＾２＋ＡＴＰａｓｅ活性的影响。实验结果表明，反应体系中ｔｏｍａｔｉｎｅ的浓度低于ｌｍｍｏｌ／Ｌ时，对不依赖钙调蛋白激活的Ｃａ＾２＋－Ｍｇ＾２＋ＡＴＰａｓｅ影响不大，浓度达ｌｍｍｏｌ／Ｌ时，该酶活性仍保持在９６％左右；而在此浓度范围内，ｔｏｍａｔｉｎｅ对依赖于ＣａＭ激活的Ｃａ＾２＋Ｍｇ＾２＋ＡＴＰａｓｅｅ有明显的抑制作用；其ＩＣ５０值为０．１４ｍｍｏｌ／Ｌ     

唾液酸与唾液酸识别蛋白研究进展

唾液酸（sialic acid）是广泛存在于生命系统中的一类蛋白类物质,近年来因其在生物学研究及生物制药领域的重要价值成为了研究热点。文章综述了唾液酸的特性、唾液酸识别蛋白的种类、唾液酸与唾液酸识别蛋白结合所产生的生物学效应等方面的最新研究进展。     

Avian flu: influenza virus receptors in the human airway

Although more than 100 people have been infected by H5N1 influenza A viruses, human-to-human transmission is rare. What are the molecular barriers limiting human-to-human transmission? Here we demonstrate an anatomical difference in the distribution in the human airway of the different binding molecules preferred by the avian and human influenza viruses. The respective molecules are sialic acid linked to galactose by an alpha-2,3 linkage (SAalpha2,3Gal) and by an alpha-2,6 linkage (SAalpha2,6Gal). Our findings may provide a rational explanation for why H5N1 viruses at present rarely infect and spread between humans although they can replicate efficiently in the lungs.     

Antigenic epitope peptides of influenza H3N2 virus neuraminidase gene based on experiments

The neuraminidase (NA) in viral surface is one of the main subtype-specific antigen of influenza type A viruses.Neuraminidase is an enzyme to break the bonds between hemagglutinin (HA) and sialic acid to release newly formed viruses from infected cells.In this study,the H3N2 subtype virus NA genes were sequenced and NA proteins were screened for B-cell epitopes and assessed based on immunoinformatics.Based on this results,four peptides DR6,EY7,VG8 and RE8 (covering amino acid residues 151-156,368-374,398-405 and 428-435,respectively) of the NA protein were synthesized artificially.These peptides were used to immunize New Zealand rabbits subcutaneously to raise antisera.Experimental results showed that these four peptides were capable of eliciting antibodies against H3N2 viruses in a specific and sensitive feature,detected in vitro by enzyme-linked immunosorbent assay.Moreover,hemadsorption anti-releasing effects took place in three three-antisera-mixtures at a dilution of 1:40.Alignment using NA gene database showed that amino acid residues in these four epitope peptides were substituted at specific sites in all the NAs sequenced in this study.It was suggested that these NA epitope peptides might be used in combination with HA proteins as vaccine antigens.     

红细胞表面电荷的研究 Ⅲ.红细胞年龄对电泳率的影响

本文采用Murphy法分离老、中、青不同年龄的红细胞.经细胞电泳测定,人红细胞电泳率随细胞年龄增大而下降(P<0.01).并进一步证实,人红细胞在体内衰老过程中,其电泳率的下降和唾液酸含量减少有关.     

血清唾液酸测定鉴别肝癌与肝硬变的临床应用价值

本文报告72例原发性癌(PHC)、27例转移性肝癌(MHC),以及50例肝硬变患者血清唾液酸(SA)的含量变化,测定结果:PHC、MHC 唾液酸含量分别为7.5±1.6mg/dm~3,8.29±0.89mg/dm~3,明显高于肝硬变组(4.73±0.92mg/dm~3)。前者阳性率分别为75.0%和92.6%,与肝硬变组相比,呈非常显著性差异 P<0.001),故血清唾液酸测定不仅在诊断肝癌上有一定意义,而且对肝癌与肝硬变的鉴别也有较好的辅助诊断价值。     

The structure of H5N1 avian influenza neuraminidase suggests new opportunities for drug design

The worldwide spread of H5N1 avian influenza has raised concerns that this virus might acquire the ability to pass readily among humans and cause a pandemic. Two anti-influenza drugs currently being used to treat infected patients are oseltamivir (Tamiflu) and zanamivir (Relenza), both of which target the neuraminidase enzyme of the virus. Reports of the emergence of drug resistance make the development of new anti-influenza molecules a priority. Neuraminidases from influenza type A viruses form two genetically distinct groups: group-1 contains the N1 neuraminidase of the H5N1 avian virus and group-2 contains the N2 and N9 enzymes used for the structure-based design of current drugs. Here we show by X-ray crystallography that these two groups are structurally distinct. Group-1 neuraminidases contain a cavity adjacent to their active sites that closes on ligand binding. Our analysis suggests that it may be possible to exploit the size and location of the group-1 cavity to develop new anti-influenza drugs.     

红细胞表面电荷的研究——III.红细胞年龄对电泳率的影响

本文采用Murphy法分离老、中、青不同年龄的红细胞。经细胞电泳测定,人红细胞电泳率随细胞年龄增大而下降(P<0.01)。并进一步证实,人红细胞在体内衰老过程中,其电泳率的下降和唾液酸含量减少有关。     

家鸽、小白鼠和家兔的血象及血清蛋白醋纤膜电泳的初步观察

本文报告了健康家鸽(100例)、小白鼠(229例)和家兔(116例)的血象和血清蛋白醋纤膜电泳的结果:家鸽、小白鼠的红细胞、白细胞和血小板总数以及血红蛋白浓度均有随体重的增加而增加的趋势;而家兔红细胞、血小板总数以及血红蛋白浓度则出现随体重的增加而减少的现象。家鸽、小白鼠的淋巴细胞的百分率大于粒细胞,而家兔则相反。     

Special features of the 2009 pandemic swine-origin influenza A H1N1 hemagglutinin and neuraminidase

Since the 2009 pandemic H1N1 swine-origin influenza A virus (09 S-OIV) has reminded the world about the global threat of the ever changing influenza virus,many questions regarding the detailed re-assortment of influenza viruses yet remain unanswered.Influenza A virus is the causative agent of the pandemic flu and contains 2 major antigenic glycoproteins on its surface:(i) hemagglutinin (HA);and (ii) neuraminidase (NA).The structures of the 09 S-OIV HA and NA proteins (09H1 and 09N1) have recently been resolved in our laboratory and provide some clues as to why the 09 S-OIV re-assortment virus is highly infectious with severe consequences in humans.For example,the 09H1 is highly similar to the HA of the 1918 influenza A pandemic virus in overall structure and especially in regards to its 5 defined antibody binding epitopes.For 09N1,its most distinctive feature is the lack of a 150-loop active site cavity,which was previously predicted to be present in all N1 NAs,and we hypothesize that the 150-loop may play a important role in the substrate specificity (α2,3 or α2,6 linked sialic acid receptors) and enzymatic mechanism of influenza NA.Combination of the HA and NA with special characteristics for the 09 S-OIV might contribute to its high increased transmissibility in humans.     

日本沼虾胚胎发育时期消化酶活力和氨基酸含量

采用生物化学方法测定了日本沼虾胚胎发育过程中四种消化酶的比活力和氨基酸的含量.结果显示：卵内可溶性蛋白的含量随着胚胎的发育逐渐下降,但在原肠期的可溶性蛋白含量略高于囊胚期.四种消化酶中类胰蛋白酶、胃蛋白酶和淀粉酶活力在胚胎发育早期和后期较高,中期较低.纤维素酶活力较低且在胚胎发育过程中变化规律不明显.总氨基酸含量在胚胎发育早期下降较快,胚胎发育至后无节幼体期氨基酸含量下降幅度变缓.必需氨基酸中亮氨酸的含量高,非必需氨基酸中谷氨酸的含量最高.单个必需氨基酸含量与必需氨基酸总量的比值（A/E）在整个胚胎发育过程中的变化基本趋于一致.