X-射线纤维衍射在多糖构型分析中应用的研究进展

本文从Ｘ射线纤维衍射法的原理,实验方法及应用实例三个方面对该方法在多糖构型分析中的应用状况进行综述,引用文献２０篇。     

Comparative conformational analysis of nucleosides by NMR, X-ray, and semi-empirical (PM3 VS. AM1) methods

The 2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl ortho-aza-purine and -pyrimidine nucleosides manifest an unusually rigid sugar N conformation in solution.     

SYNTHESIS AND BIOLOGICAL ACTIVITY OF CYCLIC ADP-CARBOCYCLIC-RIBOSE ANALOGS: STRUCTURE-ACTIVITY RELATIONSHIP AND CONFORMATIONAL ANALYSIS OF N-1-CARBOCYCLIC-RIBOSE MOIETY

Several cyclic ADP-carbocyclic-ribose analogs 3–10 modified in the N-1-carbocyclic-ribose moiety were synthesized. Their Ca²⁺-releasing activity was estimated in sea urchin eggs to show that the 3″-deoxy analog 6 shows 5 times more potent activity than cADPcR, but the 2″,3″-didieoxy-2″,3″-unsunsaturated analog 3 has very weak activity. We also calculated their stable conformation and found that 3 and 6 were significantly different in their stable conformation.     

HALOGENATED NUCLEIC ACIDS: STRUCTURE AND CONFORMATIONAL STUDIES OF 5-FLUOROCYTIDINE BY X-RAY CRYSTALLOGRAPHY AND NMR SPECTROSCOPY

Abstract

The stereochemistry and the conformational equilibria of 5-fluorocytidine (5FCyd) have been determined by X-ray crystallography and correlated with NMR spectroscopy in the solution state. Crystals of 5FCyd have unit cell dimensions a=9.854(1), b=l5.012(2), c=15.290(2)Å, α=β=γ=90° with two molecules in the asymmetric unit. Both molecules are in the anti-conformation, C3′-endo sugar pucker and a ? (C4′-C5′) of g⁺. The two molecules in the asymmetric unit show slight variation in their bond distances and bond angles but their overall solid state conformation is similar. The NMR results indicate the 5FCyd has an anti-conformation, a mixed sugar pucker of 36% C2′- endo and 64% C3′-endo and an exocyclic furanose conformation (?) of 74%(g⁺), 19%(t) and 7%(g^?).

Certain purine and pyrimidine analogues readily replace the natural bases in nucleic acid if they are present during replication. Halogenated nucleic acids have been known for the past thirty years when for the first time it was found that 5-iodouracil could be incorporated into the nucleic acid of E coli ¹. This provided the basis for the synthesis of 5-fluoro-nucleic acid bases and their use as a chemotherapeutic agent.

The biological properties of 5-halogenated uracil derivatives have been examined in detail. The incorporation of the halogenated base into mRNA could lead to errors in the reading frame which would alter the phenotype without permanent change in DNA genotype^2-4, also, it can substitute for uracil into mRNA and may exert a mutagenic effect⁵ or can occasionally lead to the production of altered protein^6-7. A substitution of uracil by fluorouracil in the mRNA and a preferential pairing of the 5FUra with a guanosine in the tRNA anti-codons can account for the first substitution. This is because 5FU assumes properties similar to cytosine when the base ionizes. This occurs readily for 5FU (pKa = 7.8) due to the electronegative fluorine atom at C5 instead of hydrogen. 5FCyd shows antifungal activity against Saccharomyces cerevisiae and Candida species. It is the drug of choice for systemic infections. In order to obtain a more basic understanding of the potential of such processes, the present study was undertaken as the first step using solid phase study by X-ray crystallography and its structure in solution by NMR spectroscopy⁸.     

利用~1H-NMR模拟谱研究二核苷酸A3′P(CH_3)5′A的构象性质

本文根据Altona等人的方法,在利用~1H-NMR模拟谱确定18℃、40℃、70℃三种温度下有关质子化学位移及偶合常数的基础上,分析了A3′P(CH_3)5′A的两种非对映异构体a和b的构象状态。它们与A3′P(OH)5′A相比发现:(1)在18℃时两个核糖环是S型构象占主要成分,并随温度升高S型构象成分增多;(2)磷酸骨架的扭角ε′和β′分别改变±15°及±4°;(3)在优势构象情况下,两个核糖环都部分重叠,而且A3′P(CH_3)5′A(a)的重叠程度比A3P′(CH_3)5′A(b)小;(4)腺嘌呤碱基都更倾向去堆积状态,而且随温度升高A3′P(CH_3)5′A(a)比A3′P(CH_3)5′A(b)有着更强的去堆积效应。     

鬼灯擎中丹宁类化合物的分离及结构的核磁共振分析（Ⅱ）

利用Toyopearl HW-40(C)凝胶反复柱层析,从鬼灯擎(Rodsersia aesculifolia Ba-tal.)根茎的70％Me_2CO提取物中分离得到六种丹宁类化合物,其中四种经化学及核磁共振分析分别确定其结构为3-0-没食子酰基-(-)-表儿茶素[3-0-galloyl-(-)-epicatechin]RA-11,1,3-0-没食子酰基-表儿茶素-(4β-8)-(3-0-没食子酰基)-表儿茶素[(3-0-galloyl)-epieatechin-(4β-8)-(3-0-Salloyl)-epicatechin]RA-13,2;1,2,4,6-四-0-没食子酰基-β-D-葡萄糖[1,2,4,6-tetra-0-galloyl-β-D-glucose]RA-14,3和没食子酸甲酯(methyl gallate)RA-16,4。RA-14为首次获得的结晶性没食子丹宁,这些成分均为首次从该植物中得到。     

A COMPARATIVE ANALYSIS OF THE VOLVOCACEAE (CHLOROPHYTA)1

This review covers essentially all aspects of the organisms in the green algal family Volvocaceae and suggests the genetic history of the various steps in their evolution from their unicellular ancestors.     

用聚类分析方法对土家族和瑶族人发中7种元素综合指标的比较研究

对我国土家族、瑶族青年人体头发中钙、镁、铁、锰、铜、锌、铬等7种金属元素进行了测定。用聚类方法对元素含量的综合指标进行了考查、比较研究。结果表明,土家族与瑶族青年人体头发中这7种元素的综合指标存在明显的差别,民族之间区别较大。     

(D)- AND (L)-CYCLOHEXENYL-G,A NEW CLASS OF ANTIVIRAL AGENTS: SYNTHESIS,CONFORMATIONAL ANALYSIS,MOLECULAR MODELING,AND BIOLOGICAL ACTIVITY

(D)- and (L)-cyclohexeneyl-G were synthesized enantioselectively starting from (R)-carvone. Both show potent and selective anti-herpesvirus activity (HSV-1, HSV-2, VZV, CMV). Molecular modeling demonstrates that both isomers are bound in the active site of HSV-1 thymidine kinase in a high-energy conformation with the base moiety orienting in an equatorial position. It is believed that the flexibility of the cyclohexene ring is essential for their antivirial activity.     

COMPARATIVE MORPHOLOGY AND TAXONOMIC STATUS OF GRACILARIOPSIS (GRACILARIALES,RHODOPHYTA)1

The vegetative organization and reproductive development of Gracilariopsis lemaneiformis (Bory) Dawson, Acleto et Foldvik [including Gracilaria sjoestedtii Kylin] were investigated. Our observations on spermatangial development and post-fertilization features establish that Gracilariopsis Dawson is distinct at the generic level from Gracilaria Greville, and ice propose the resurrection of Gracilariopsis Dawson as a result. Spermatangial parent cells of Gracilariopsis are superficial, initiated in pairs or groups of three by concavo-convex longitudinal and transverse divisions. Each spermatangial parent cell cuts off a single, colorless spermatangium distally by a transverse division. The female reproductive apparatus consists of a supporting cell that bears a two-celled carpogonial branch flanked by two sterile branches, as in Gracilaria. Likewise, up to six sterile cells fuse with the carpogonium after fertilization to produce a primary fusion cell that generates the gonimoblasts; however, a secondary fusion cell is absent. Inner gonimoblast cells unite with cytologically modified cells of the inner pericarp by means of secondary pit-connections. Tubular nutritive cells are absent. The gonimoblast consists of a central sterile tissue interconnected throughout by secondary pit-connections surmounted by a fertile layer composed of carposporangia aligned in straight chains. The distribution of Gracilariopsis is extended to Western Europe.     

人卵泡促性腺激素释放肽（hF－GRP）的STM研究

人卵泡促性腺激素释放肽（ｈＦ－ＧＲＰ）为一只含１４个氨基酸的多肽类激素,我们已经用２Ｄ—ＮＭＲ技术测定了它的溶液构象,本文又用ＳＴＭ技术观察了ｈＦ—ＧＲＰ单层铺展时的分子图象,测得其分子大小的为２．４ｎｍ并用２Ｄ—ＮＭＲ结果较好地解释了所得的图象。     

人卵泡促性腺激素释放肽（hF－GRP）的STM研究

人卵泡促性腺激素释放肽（ｈＦ－ＧＲＰ）为一只含１４个氨基酸的多肽类激素,我们已经用２Ｄ－ＮＭＲ技术测定了它的溶液构象,本文又用ＳＴＭ技术观察了ｈＦ－ＧＲＰ单层铺展时的分子图象,测得其分子大小约为２．４ｎｍ,并用２Ｄ－ＮＭＲ结果较好地解释了所得的图象。     

QUANTITATIVE ULTRASTRUCTURE AND PROTEIN COMPOSITION OF DATE PALM (PHOENIX DACTYLIFERA) SEEDS: A COMPARATIVE STUDY OF ENDOSPERM VS. EMBRYO

Comparative studies on the ultrastructure and protein composition of the embryo and endosperm of date palm (Phoenix dactylifera L.) were conducted. Cells of the embryo cotyledon and endosperm function in reserve storage and contained cell walls, nuclei, and cytoplasm rich in lipid and protein bodies. Morphometric analysis from light and electron micrographs showed that the cell walls of the endosperm occupied 65% of the total cell volume, but only 6% in the embryo. The protein bodies of the endosperm accounted for 11%, whereas those of the embryo occupied more than half of the total cell volume. The volume of organelles and organelle-free cytoplasm in the endosperm was negligible, suggesting that most of the extractable endosperm proteins are localized in the protein bodies. Extractable proteins in the embryo may come from cytoplasm, protein bodies, and other organelles. The endosperm contains relatively lower amounts of proteins than does the embryo. Proteins extracted from both tissues were compared using SDS-polyacrylamide gel electrophoresis, tube gel isoelectric focusing, and two-dimensional electrophoresis. Proteins of both the tissues were heterogeneous in molecular mass and charge. The majority of the proteins were similar in molecular mass and charge in the two tissues, suggesting that most of the storage proteins are probably the same. However, there were also several embryo- and endosperm-specific proteins apparent in both the first- and second-dimension gels. The endosperm-specific proteins may play an important role in germination and seedling development.     

利用单克隆抗体对乙型脑炎病毒不同毒株抗原分析的研究

实验发现,应用动物免疫血清(多克隆抗体,PcAb)进行抗原分析时,我国分离到的乙型脑炎病毒SA14、P3、A2和高株的抗原性无明显差别,与从日本分离到的中山株有些差别,但仍被PcAb所中和;而用单克隆抗体(McAb)进行分析,情况就明显不同:SA14和P3株抗原性相似,高株和中山株不能被51-8McAb所中和,A2株则介于两者之间。A2和高顺生株的寡核苷酸指纹图谱分析表明,高株比A2株多两个斑点,但大多数斑点是一样的,证实了上述结果。实验还发现不同毒株的保护效果不同,A2株的免疫效果明显优于高株。     

酵母还原乙酰乙酸乙酯制备(S)-3-羟基丁酸乙酯的研究

研究了五种酵母催化乙酰乙酸乙酯生成(S)-3-羟基丁酸乙酯的能力,筛选出催化性能较好的菌株酿酒酵母,并以该酵母为出发菌株进行紫外诱变筛选出催化性能更优良的菌株LY7;另外还对菌株LY7催化乙酰乙酸乙酯生成(S)-3-羟基丁酸乙酯的反应特性进行了研究。研究表明:采用200g/L蔗糖作为碳源,初始乙酰乙酸乙酯浓度为0.25mol/L,初始细胞浓度为150g/L,反应温度为36℃时所得产物得率和对映体过剩值最高。     

COMPARATIVE ANALYSIS OF SWIMBLADDER (DRUMMING) AND PECTORAL (STRIDULATION) SOUNDS IN THREE FAMILIES OF CATFISHES

ABSTRACT

Among teleosts, only representatives of several tropical catfish families have evolved two sonic organs: pectoral spines for stridulation and swimbladder drumming muscles. Pectoral mechanisms differ in relative size between pimelodids, mochokids and doradids, whereas swimbladder mechanisms exhibit differences in origin and insertion of extrinsic muscles. Differences in vocalization among families were investigated by comparing distress calls in air and underwater. High frequency broad-band pulsed sounds of similar duration were emitted during abduction of pectoral spines in all three families. Adduction sounds were similar to abduction signals in doradids, shorter and of lower sound pressure in mochokids, and totally lacking in pimelodids. Simultaneously or successively with pectoral sounds, low frequency harmonic drumming sounds were produced by representatives of two families. Drumming sounds were of similar intensity as stridulatory sounds in pimelodids, fainter in doradids, and not present in mochokids. Swimbladder sounds were frequency modulated and the fundamental frequency was similar in pimelodids and doradids. The ratio of stridulatory to drumming sound amplitude was higher in air than underwater in both doradids and one of the pimelodids. Also, overall duration of pectoral sounds, compared to swimbladder sounds, was longer in air than underwater in one doradid and pimelodid species. This first comparison of vocalization within one major teleost order demonstrates a wide variation in occurrence, duration, intensity and spectral content of sounds and indicates family- and species-specific as well as context- (receiver-) dependent patterns of vocalization.     

AN ANALYSIS OF DESMOSOME SHAPE, SIZE, AND ORIENTATION BY THE USE OF HISTOMETRIC AND DENSITOMETRIC METHODS WITH ELECTRON MICROSCOPY

The probable shape, size, and orientation of desmosomes of the cells comprising the secretory tubules in rat submaxillary gland was determined by statistical and algebraic methods applied to electron micrographs. It was concluded that these desmosomes are discrete ellipsoidal discs whose principal axes are in the order of 4100 and 2500 angstrom units, and that they are preferentially oriented with their long axis more or less parallel to the base-apex axis of the cell. Densitometric interpretation agrees with the statistically based reconstruction of desmosomal shape. By densitometric analysis it was also determined that the peak to peak distances between layers within these desmosomes are in essential agreement with other reported findings. The approach described may have general applications to problems in the analysis of submicroscopic morphology.     

HIGH‐RESOLUTION MAGIC ANGLE SPINNING NMR ANALYSIS OF WHOLE CELLS OF CHAETOCEROS MUELLERI (BACILLARIOPHYCEAE) AND COMPARISON WITH 13C‐NMR AND DISTORTIONLESS ENHANCEMENT BY POLARIZATION TRANSFER 13C‐NMR ANALYSIS OF LIPOPHILIC EXTRACTS1

Lipid composition in extracted samples of Chaetoceros muelleri Lemmermann was studied with ¹³C‐NMR and distortionless enhancement by polarization transfer (DEPT) ¹³C‐NMR, resulting in well‐resolved ¹³C‐NMR spectra with characteristic resonance signals from carboxylic, olefinic, glyceryl, methylene, and methyl groups. The application of a DEPT pulse sequence aided in the assignment of methylene and methine groups. Resonance signals were compared with literature references, and signal assignment included important unsaturated fatty acids such as eicosapentaenoic and docosahexaenoic and also phospholipids and glycerols. Results from the extracted samples were used to assign resonance signals in a high‐resolution magic angle spinning (HR MAS) DEPT ¹³C spectrum from whole cells of C. muelleri. The NMR analysis on whole cells yielded equally good information on fatty acids and also revealed signals from carbohydrates and amino acids. Broad resonance signals and peak overlapping can be a problem in whole cell analysis, but we found that application of HR MAS gave a well‐resolved spectrum. The chemical shift of metabolites in an NMR spectrum depends on the actual environment of nuclei during analysis, and some differences could therefore be expected between extracted and whole cell samples. The shift differences were small, and assignment from analysis of lipophilic extract could be used to identify peaks in the whole cell spectrum. HR MAS ¹³C‐NMR therefore offers a possibility for broad‐range metabolic profiling directly on whole cells, simultaneously detecting metabolites that are otherwise not detected in the same analytical set up and avoiding tedious extraction procedures.     

真空负压和常规ABC法显示HPV—1抗原的应用比较

应用真空负压 ABC 法显示 HPV-1抗原比常规 ABC 法效果好,敏感性高,时间短,整个过程只需一个多小时,阳性物明显突出,颗粒均匀,色泽鲜艳,呈黄棕色,背景清晰等优点。还可提高抗体的稀释度,降低成本。与微波技术相比,具有设备简单,易于操作,安全可靠,不受条件限制,经对26例尖锐湿疣的病例进行多层次稀释度的研究,取得了满意的结果,认为该法值得推广应用。     

3-磷酸甘油醛脱氢酶胍变性时的活力及构象变化

酵母3-磷酸甘油醛脱氢酶在盐酸胍溶液中的内源荧光及剩余活力的变化结果提示:apo酶及holo酶的活力在胍浓度为0.5M左右可完全丧失.同时伴有内源荧光强度的下降,光谱宽度的增加和335nm最大发射峰的红移(提示了色氨酸残基的暴露).与已经报导的肌肉酶(内源荧光强度在胍浓度为0.4—1.2M范围相对稳定)不同,酵母酶内源荧光在此浓度范围内表现为逐渐降低.在0.7M胍溶液中,内源荧光变化动力学过程只能测出一相,而酶失活动力学过程为快慢两相,快相动力学速度常数至少大于内源荧光降低速度常数三个数量级以上.以上结果提示:低浓度胍可引起该酶的完全失活,活性部位的空间构象比酶分子的构象更易受到变性剂的扰乱;有一个色氨酸残基位于或靠近酶的活性部位.