Transport of 3-O-methyl d-glucose and β-methyl d-glucoside by rabbit ileum

The intestinal transport of three actively transported sugars has been studied in order to determine mechanistic features that, (a) can be attributed to stereospecific affinity and (b) are common.The apparent affinity constants at the brush-border indicate that sugars are selected in the order, $\text{β-methyl glucose >}\text{d}\text{-galactose}\text{> 3-O-}\text{methyl}$ glucose, (the K_m values are 1.23, 5.0 and 18.1 mM, respectively.) At low substrate concentrations the K_t values for Na⁺ activation of sugar entry across the brush-border are: 27.25, and 140 mequiv. for β-methyl glucose, galactose and 3-O-methyl glucose, respectively. These kinetic parameters suggest that Na⁺, water, sugar and membrane-binding groups are all factors which determine selective affinity.In spite of these differences in operational affinity, all three sugars show a reciprocal change in brush-border entry and exit permeability as Ringer [Na] or [sugar] is increased. Estimates of the changes in convective velocity and in the diffusive velocity when the sugar concentration in the Ringer is raised reveal that with all three sugars, the fractional reduction in convective velocity is approximately equal to the (reduction of diffusive velocity)². This is consistent with the view that the sugars move via pores in the brush-border by convective diffusion.Theophylline reduces the serosal border permeability to β-methyl glucose and to 3-O-methyl glucose relatively by the same extent and consequently, increases the intracellular accumulation of these sugars.The permeability of the serosal border to β-methyl glucose entry is lower than permeability of the serosal border to β-methyl glucose exit, which suggests that β-methyl glucose may be convected out of the cell across the lateral serosal border.     

Le genre LeptophloeumDawson, 1862 du Dévonien

The study of numerous prints referred to the devonian genus Leptophloeum, more particularly from Kazakhstan and South Africa, has permitted to specify the morphology of the leaves and to explain the prints of the leaf cushions. The different species are revised. A comparison of the devonian genus Leptophloeum with the permian genus Lycopodiopsis leads us to consider the distinction of a new order: the Leptophloeodendrales regrouping these two genus.     

Nouvelle synthèse de spiro-orthoesters d-glucosidiques par photocyclisation stéréoselective d'hydroxyalkyl-d-glucosides

Irradiation of hydroxyalkyl glucosides in the presence of mercury(II) oxide and iodine gave glucosidic C-1-spiroorthoesters. Where the starting glycoside had CH₂OH, the cyclization was regio- and stereo-specific by α-attack. The C-1-spiroorthoesters were readily available in a “one-pot synthesis” starting from glucosyl halides.     

Synthèse des 2-amino-2-désoxy-d-arabinono- et -d-xylono-lactones par condensation d'acides aminés avec le d-glycéraldéhyde. Analyse structurale par rayons X de deux dérivés

Synthesis of 2-amino-2-deoxy-d-pentonolactones was performed by diastereoselective hydroxyalkylation of 2,3-O-isopropylidene-d-glyceraldehyde with ethyl isocyanoacetate, to give two oxazolines in a ratio of 7:3. Hydrolysis gave first the corresponding amides, and then the 2-amino-2-deoxypentonolactones. The structure of the 2-amino-2-deoxy-d-arabinono-1,4-lactone was established by X-ray diffraction, indicating exclusive formation of trans-oxazolines and of an “erythro” configuration at C-3C-4 of the major compound.     

猪流感病毒概述

猪流感(Swine influenza,SI)是由甲型流感病毒引起的猪急性呼吸道传染病,不仅给养猪业带来了极大的危害,还严重危害人类健康,因此引起全球公共卫生的关注。猪对哺乳动物流感病毒和禽流感病毒都易感,被认为是二者之间进行基因重配和跨种传播的重要中间宿主,也是产生引起人类流感大流行毒株的重要来源。目前全球猪群中流行的流感病毒以H1N1、H3N2以及H1N2亚型为主,但各地流行的猪流感病毒(Swine influenza viruses,SIVs)谱系或基因节段的来源均有差异。北美地区近期暴发的猪流感三源重配H3N2/H1N2亚型变异株感染人的事件再次提醒我们要密切关注SIV对公共卫生的威胁。因此,监测和研究甲型流感病毒在全球猪群中的流行动态对于大流行应对是非常重要的。     

Derivatives of β-D-fructofuranosyl α-D-galactopyranoside

De-etherification of 6,6′-di-O-tritylsucrose hexa-acetate (2) with boiling, aqueous acetic acid caused 4→6 acetyl migration and gave a syrupy hexa-acetate 14, characterised as the 4,6′-dimethanesulphonate 15. Reaction of 2,3,3′4′,6-penta-O-acetylsucrose (5) with trityl chloride in pyridine gave a mixture containing the 1′,6′-diether 6 the 6′-ether 9, confirming the lower reactivity of HO-1′ to tritylation. Subsequent mesylation, detritylation, acetylation afforded the corresponding 4-methanesulphonate 8 1′,4-dimethanesulphonate 11. Reaction of these sulphonates with benzoate, azide, bromide, and chloride anions afforded derivatives of β-D-fructofuranosyl α-D-galactopyranoside (29) by inversion of configuration at C-4. Treatment of the 4,6′-diol 14 the 1,′4,6′-triol 5, the 4-hydroxy 1′,6′-diether 6 with sulphuryl chloride effected replacement of the free hydroxyl groups and gave the corresponding, crystalline chlorodeoxy derivatives. The same 4-chloro-4-deoxy derivative was isolated when the 4-hydroxy-1′,6′-diether 6 was treated with mesyl chloride in N,N-dimethylformamide.     

Synthesis of 4-O-β-D-mannopyranosyl-L-rhamnopyranose

The title disaccharide (16) has been synthesized in 50% overall yield by way of condensation of 4,6-di-O-acetyl-2,3-O-carbonyl-α-D-mannopyranosyl bromide 5 with methyl 2,3-O-isopropylidene-α-L-rhamnopyranoside (1) in chloroform solution, in the presence of silver oxide. The disaccharide was characterized as the crystalline isopropyl alcoholate of methyl 4-O-β-D-mannopyranosyl-α-L-rhamnopyranoside (11) and as 1,2,3-tri-O acetyl-4-O- (2,3,4,6-tetra-O-acetyl-β-D-mannopyranosyl)-α-L-rhamnopyranose (15). Methyl β-D-mannopyranoside isopropyl alcoholate 7 was readily obtained in 85% yield via the reaction of bromide 5 with methanol.Reduction of 2,3-di-O-methyl-L-rhamnose with sodium borohydride, followed by acetylation, may result in the formation of an appreciable proportion of a boric ester, namely 1,5-di-O-acetyl-4-deoxy-2,3-di-O-methyl-L-rhamnitol-4-yl dimethyl borate, depending on the procedure used.     

Synthesis of 5-O-β-D-galactofuranosyl-D-galactofuranose

Conversion of benzyl αβ-D-galactofuranoside into the 5,6-O-[α-(dimethyl-amino)benzylidene] derivative, followed by acetylation of HO-2 and HO-3, and selective ring opening or the acetal, gave benzyl 2,3-di-O-acetyl-6-O-benzoyl-αβ-D-galactofuranoside(4). The title disaccharide was synthesised from4 by reaction with 3,4,6-tri-O-acetyl-α-D-galactofuranose 1,2-(methyl orthoacetate) followed by removal of protecting groups     

d-Xylose,an anomer-specific inhibitor of α-galactosidase

d-xylose is a highly anomer-specific, powerful and competitive inhibitor of plant α-galactosidases. The apparent inhibition constant (K_i) for the interaction of d-xylose with chick pea (Cicer arietinum) α-galactosidase and the apparent number of inhibitor molecules (n) bound per enzyme molecule, using p-nitrophenyl-α-d-galactopyranoside as substrate, were found to be 0.4 × 10^?2M and 0.8, respectively.     

腺病毒新型别的研究进展

腺病毒是DNA双链病毒,与人类的多种疾病相关。迄今为止,文献报道的人腺病毒已有60多个型别。52～67型腺病毒是基于全基因组测序和生物信息学分析被发现和划分的。与以往传统血清学方法确定的51个血清型在组成方式,致病性等方面都有所不同,这些新型腺病毒大部分是由同亚属的某两个或几个血清型同源重组而成,某些病毒重组后疾病谱发生了改变。虽然重组是病毒进化的一种方式,重组现象普遍存在于新型腺病毒中,但是重组发生的机制尚不清楚,是否对人类具有潜在的危险有待进一步的研究。总之,目前新型腺病毒正逐渐受到关注,本文就新型腺病毒研究的进展展开综述,了解人腺病毒属新型别的研究现状。     

病毒性出血热实验室检测

病毒性出血热是一组临床症状主要表现为发热和出血的急性传染病,病死率高,主要由四个科的RNA病毒引起,包括布尼亚病毒科、黄病毒科、丝状病毒科和沙粒病毒科病毒。该类疾病发病初期的临床症状相似,因此,建立快速、简易的实验室检测方法对及时进行临床诊断救治、开展流行病学调查并最终控制其传播流行具有重要意义。本综述对病毒性出血热的实验室检测方面进行描述,主要内容包括病原学分类及病毒分离、核酸、抗原和抗体检测的相关技术,并结合新型检测方法提出展望。     

白蛉病毒属研究进展

白蛉病毒属病毒是单股负链RNA病毒,隶属布尼亚病毒科,基因组分为L、M和S三个片段,分别编码RNA依赖的RNA聚合酶、包膜糖蛋白和核蛋白。白蛉病毒是虫媒病毒,主要通过节肢动物传播,迄今为止,文献报道的白蛉病毒已有70多种,68个已知病毒种被分为白蛉热病毒组和乌库病毒组,其中某些白蛉热病毒组成员与人类疾病密切相关,而且最近又有新型白蛉病毒出现,本文就白蛉病毒属的分子特征、流行病学、诊断、治疗及新发现的白蛉病毒的概况展开综述。     

Synthesis of 5-O-α-and-β-d-glucopyranosyl-d-glucofuranose and 5-O-α-d-glucopyranosyl-d-fructopyranose (leucrose)

Reaction of 1,2-O-cyclopentylidene-α-d-glucofuranurono-6,3-lactone (2) with 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl bromide (1) gave 1,2-O-cyclopentylidene- 5-O-(2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl)-α-d-glucofuranurono-6,3-lactone (3, 45%) and 1,2-O-cyclopentylidene-5-O-(2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl)-α-d-glucofuranurono-6,3-lactone (4, 38%). Reduction of 3 and 4 with lithium aluminium hydride, followed by removal of the cyclopentylidene group, afforded 5-O-α-(9) and -β-d-glucopyranosyl-d-glucofuranose (12), respectively. Base-catalysed isomerization of 9 yielded crystalline 5-O-α-d-glucopyranosyl-d-fructopyranose (leucrose, 53%).     

α-D-Mannosidase-catalyzed hydrolysis of substituted phenyl α-D-mannopyranosides

The influence substituents on the hydrolysis of substituted phenyl α-D-mannopyranosides by α-D-mannosidase from Medicago sativa L. has been investigated. As indicated by structure-activity relations, the electronic effect of the substituent has an influence on the rate of formation of the intermediate mannosyl-enzyme complex. This effect depends not only on the nature of the substituent, but also on its position (meta or para) and on the temperature of the experiment. Hammett-type linear free energy relationships show that the reaction constant p changes its sign at ～27°. Substrates with strong electron-withdrawing groups show values of log V that are linearly related to 1/T, whereas the Arrhenius plots for other substrates are severely curved. This complex behaviour is tentatively explained by assuming that some meta-substituents have an unusual, temperature- and substituent-dependent influence on the formation of the Michaelis—Menten complex.     

Chemical Syntheses of 4-O-α and -β-D-galactopyranosyl-D-galactose and 3-O-α- and -β-D-galactopyranosyl-D-galactose

Reaction of 2,3-di-O-acetyl-1,6-anhydro-β-D-galactopyranose (2) with 2,3,4,6-tetra- O-acetyl-α-D-galactopyranosyl bromide in the presence of mercuric cyanide and subsequent acetolysis gave 1,2,3,6-tetra-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-α-D-galactopyranosyl)-α-D-galactopyranose (4, 40%) and 1,2,3,6-tetra-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl)-α-D-galactopyranose (5, 30%). Similarly, reaction of 2,4-di-O-acetyl-1,6-anhydro-β-D-galactopyranose (3) gave 1,2,4,6-tetra-O-acetyl-3-O-(2,3,4,6-tetra-O-acetyl-α-D-galactopyranosyl)-α-D-galactopyranose (6, 46%) and 1,2,4,6-tetra-O-acetyl-3-O-(2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl)-α-D-galactopyranose (7, 14%). The anomeric configurations of 4-7 were assigned by n.m.r. spectroscopy. Deacetylation of 4-7 afforded 4-O-α-D-galactopyranosyl-D-galactose (8), 4-O-β-D-galactopyranosyl-D-galactose (9), 3-O-α-D-galactopyranosyl-D-galactose (10), and 3-O-β-D-galactopyranosyl-D-galactose (11), respectively.     

新型人类肠道病毒的研究进展

随着人类肠道病毒(Human enteroviruses,HEVs)分子定型方法的广泛应用,越来越多的新型HEVs被发现。自1969年肠道病毒71型(EV71)首次报道后,新型HEVs已在世界范围内引起多次暴发流行,带来了严重的公共卫生问题,特别是自2007年以来在中国大陆发生的EV71所致手足口病的广泛流行,引起国内外学者的高度关注。本文对近些年有关新型HEVs分子分型、进化、流行病学特征、致病性等方面的研究进展进行了综述。     

埃博拉病毒包膜糖蛋白研究进展

埃博拉病毒可引起人类高致命性流行性出血热暴发,至今没有预防和治疗的疫苗和药物。作为埃博拉病毒包膜唯一的表面蛋白,包膜糖蛋白是一种多功能蛋白质,在病毒的吸附和穿入宿主细胞、致病性、下调宿主细胞表面蛋白质表达和增加病毒装配和出芽过程中起着至关重要的作用;同时包膜糖蛋白是保护性免疫的主要目标,是诱导产生中和抗体的最理想抗原。本文就近五年埃博拉病毒包膜糖蛋白的基因结构、致病机制和免疫原性方面的研究进展做简要回顾。     

The synthesis of 1,6-anhydro-β-d-glucopyranose and d-glucosyl oligosaccharides from maltose by a fungal glucosyltransferase

The formation of 1,6-anhydro-β-d-glucopyranose and several d-glucosyl oligosaccharides has been observed during the action of a purified, fungal glucosyltransferase (EC 2.4.1.24) on maltose. Such products are synthesized by a transglucosylation mechanism involving the formation of a d-glucosyl-enzyme complex and the displacement of the d-glucosyl group by appropriate acceptor-substrates. The formation of the 1,6-anhydro bond is a novel type of transfer reaction and occurs by displacement of the enzyme from the d-glucosyl-enzyme complex by the proton of the primary hydroxyl group of the same glucosyl group. This reaction is characterized by inversion of configuration at the position of glucosidic bond-cleavage of the substrate. Synthesis of the d-glucosyl oligosaccharides occurs by displacement of the d-glucosyl groups from the enzyme by suitable acceptor-substrates. In these cases, the reactions are characterized by retention of configuration of the d-glucosidic bonds of the substrate. The list of oligosaccharides produced from maltose includes nigerose, kojibiose, isomaltose, maltotriose, panose, isomaltotriose, and 6-O-d-glucosyl-panose. The identity of these compounds has been established by methylation analysis and enzymic hydrolysis. d-Glucose is also a product of the reaction and arises from both the reducing and the non-reducing groups of maltose.     

禽流感病毒样颗粒研究进展

病毒样颗粒(Virus-like particles,VLPs)是指由病毒一个或几个结构蛋白自行组装成不含病毒基因组且不能复制、不具有感染能力的病毒样蛋白颗粒。VLPs因能够模拟天然病毒的构象表位而保持了完整病毒颗粒所具有的免疫原性,可诱导机体产生广泛强大的抗病毒免疫反应,阻止病毒侵入机体,在抗病毒性疾病的预防或治疗性疫苗及诊断试剂的研究开发方面具有巨大的应用前景。本文就禽流感病毒样颗粒相关研究进展进行综述,以期为我国禽流感VLPs的研究提供参考。