安络小皮伞中水溶性多糖的研究——Ⅰ.甘露聚糖 FP_1 的纯化与结构研究

从安络小皮伞水溶性多糖中分离纯化得一甘露聚糖 FP_1。分子量约为24万。经红外光谱、~+H-NMR 谱和亲和层析指明为β-甘露聚糖。结构分析采用高碘酸氧化、Smith 降解、完全甲基化 GC、GC-MS 与~(13)C-NMR 分析,分子的主链是β-D-(1→6)连接的甘露糖,支链为β-(1→3),β(1→2)甘露糖,分别连接在主链的 O-3和 O-2上。     

龙柏茎叶中抑菌活性成分的分离与鉴定

采用活性追踪和柱层析法,以苹果腐烂病菌、葡萄白腐病菌等为靶标菌,提取、分离、鉴定了龙柏茎叶中抑菌活性成分.结果表明,对龙柏茎叶乙醇提取物的石油醚、乙酸乙酯和正丁醇萃取物活性测定中,石油醚萃取物的活性最高.对石油醚萃取物进行硅胶柱层析,得到一种活性较高的化合物A,对苹果腐烂病菌的EC_(50)为0.862 4 mg/mL.经氢谱(1H-NMR)、碳谱(~(13)C-NMR)和红外等确定了化合物A的结构为4-松香酸.     

华贝亭的结构

从家种川产华西贝母(Fritillaria siechuanica)鳞茎中分出一新的甾体生物碱华贝亭(Siechuantine)。其结构由光谱(IR、MS、~1H-、~(13)C-NMR、~1H—~1H Cosy、~(13)C—~1H Cosy和noeds)法推定为1。     

天然C_(19)-二萜生物碱的核磁共振谱(Ⅰ)

本文将迄今为止已发表的230余个天然C_(19)-二萜生物碱按其结构和核磁共振波谱特征分为8个类型,着重叙述了每个类型的结构和核磁共振波谱,并对某些立体构型与~(13)C-NMR化学位移的关系进行了讨论。最后以表格的形式报导了每个天然C_(19)-二萜生物碱的结构及其主要的植物来源,并将其中170余个生物碱的~(13)C-NMR化学位移数据分门别类,整理成表,以便于对相似化合物的~(13)C-NMR进行比较,这样对于分析鉴定C_(19)-二萜生物碱将大有帮助。第一部分包含两个主要的类型——乌头碱型和牛扁碱型,其它类型待第二部分进行讨论。     

金顶侧耳多糖PC-4的结构确定与抗肿瘤活性的研究

从3％三氯乙酸浸提过的金顶侧耳(Pleurotus citrinopileatus)子实体中分离纯化另一水溶性多糖PC-4。该多糖分子量约为189Kd。纸层析与气相层析分析表明其为单一葡聚糖。经高碘酸氧化,Smith降解,甲基化,气相层析,气质联机分析,核磁共振(~1H-NMR,~(13)C-NMR)谱及红外光谱测定等,可确定PC-4的主链结构由β(1→3)糖苷键相连的葡萄糖构成,部份残基C_6上带有分支。约每5个糖残基有两个侧链,侧链仅为1个葡萄糖残基。 给ICR小鼠腹腔注射PC-4,对移植性肿瘤S-180有一定的抑制作用,抑瘤率为67％。离体条件下,PC-4与肿瘤细胞S-180共同培养,则未显示抑瘤作用。     

改性酵母葡聚糖—CMG的结构特征

本文采用凝胶过滤色谱法,对两种不同工艺方法制备的羧甲基酵母葡聚糖(MA和MW)的分子量进行了测定。采用~(13)C-NMR光谱,研究了酵母葡聚糖和羧甲基葡聚糖的主链的连接方式和羧甲基在葡聚糖分子中的分布。研究结果发现,MA的分子量略大于MW,它们的分子量均在10~5数量级。酵母葡聚糖是以β-(1-3)连接为主的。羧甲基化取代主要发生在C_5位的羟基上。     

药用异喹啉生物碱的研究：Ⅱ.地不容生物碱的研究

从地不容块根中分得四种生物碱A、B、C、D,经UV,IR,~1H-NMR,~(13)C-NMR,HRMS等方法鉴定了它们的结构,分别是cepharanthine (A),1-curine (B),isochondodendrine (C),ushinsunine (D)。C,D系首次从该植物中获得。     

13C核磁共振谱在三萜和三萜甙化学中的应用

本文简略地叙述了三萜和三萜甙的~(13)C NMR谱及其在研究生物合成、立体化学和阐明结构等方面的应用。     

硒化黄芪多糖制备条件及其结构的研究

硒化具有生物活性的黄芪多糖Ⅰ,预期将产生更强的药疗营养效果。本文为得到高含硒量的黄芪多糖Ⅰ进行了较详尽的探索,找出了最佳反应条件。经硒分析、紫外光谱、红外光谱和~(13)C-NMR分析,基本确证硒化多糖的结构为硒化试剂与单糖上两个顺式相邻羟基形成五员环的亚硒酸酯(1.2和6.6位)。     

条斑紫菜中一种琼胶多糖的分离纯化及鉴定

条斑紫菜(Porphyra yezoensis)的热水提取物,经DE-23和Sephadex G-200柱层析纯化,得到一种含微量硫酸基的琼胶精品(PY1)。此多糖经Sepharose 6B柱层析鉴定为单一组分,分子量为220 kD。紫外光谱显示它不含蛋白质、多肽及核酸。红外光谱揭示它含3,6_内醚_半乳糖的特征吸收以及微量的硫酸基。该多糖的水解产物经气相色谱分析,主要由半乳糖及其衍生物组成,有少量岩藻糖存在。通过高磺酸氧化和Smith除解以及１３C-NMR谱的分析,该多糖主要由琼胶二糖结构单元和它的生物前体组成,以琼胶二糖为主。     

Assignment of the 13C nuclear magnetic resonance spectrum of a short DNA-duplex with 1H-detected two-dimensional heteronuclear correlation spectroscopy.

Proton-detected 1H-13C heteronuclear correlated spectroscopy [( 1H,13C]-COSY) was used to establish relations between the carbon-13 and proton nuclear magnetic resonance chemical shifts in the hexadeoxynucleoside pentaphosphate d-(GCATGC)2. Using the previously established sequence-specific proton NMR assignments, sequence-specific assignments were thus obtained for nearly all proton-bearing carbons. This approach offers a new criterion for distinguishing between the proton NMR lines of purines and pyrimidines, based on the different proton-carbon-13 coupling constants. Furthermore, the adenine ring carbon 2 has a unique carbon-13 chemical shift, which enables a straightforward identification of the adenine C2H resonances by [1H,13C]-COSY.     

High-resolution proton and carbon-13 NMR of membranes: why sonicate?

We have obtained high-field (11.7-T) proton and carbon-13 Fourier transform (FT) nuclear magnetic resonance (NMR) spectra of egg lecithin and egg lecithin-cholesterol (1:1) multibilayers, using "magic-angle" sample spinning (MASS) techniques, and sonicated egg lecithin and egg lecithin-cholesterol (1:1) vesicles, using conventional FT NMR methods. Resolution of the proton and carbon-13 MASS NMR spectra of the pure egg lecithin samples is essentially identical with that of sonicated samples, but spectra of the unsonicated lipid, using MASS, can be obtained very much faster than with the more dilute, sonicated systems. With the 1:1 lecithin-cholesterol systems, proton MASS NMR spectra are virtually identical with conventional FT spectra of sonicated samples, while with 13C NMR, we demonstrate that most 13C nuclei in the cholesterol moiety can be monitored, even though these same nuclei are essentially invisible, i.e., are severely broadened, in the corresponding sonicated systems. In addition, 13C MASS NMR, spectra can again be recorded much faster than with sonicated samples, due to concentration effects. Taken together, these results strongly suggest there will seldom be need in the future to resort to ultrasonic disruption of lipid bilayer membranes in order to obtain high-resolution proton or carbon-13 NMR spectra.     

The production of lipids alternately labelled with carbon-13

Chlorella cells were shown to have similar fatty acid profiles when grown photoautotrophically or if grown photoheterotrophically with ethanoate (acetate) as carbon source. When supplied with ethanoate labelled with carbon-13 in the methyl group, the alga incorporated it into fatty acids with retention of the sequence of labelling on alternate carbon atoms, thus providing a convenient method for synthesising lipids in a form useful for nuclear magnetic resonance (NMR) studies of lipids in situ in membranes. Marine algae used in fish farming may have higher levels of very highly unsaturated fatty acids; proposals for producing these compounds labelled with carbon-13 are, therefore, presented, based on using centrally labelled glycerol. The scope for producing other substances labelled in a form suitable for NMR studies, such as carotenoids, is discussed.     

Utilization of an Escherichia coli mutant for carbon-13 enrichment of tRNA for NMR studies.

The enrichment of tRNA at specific sites with carbon-13 has been accomplished in vivo using a mutant of Escherichia coli. A relaxed strain of E. coli auxotrophic for methionine was grown in a specifically defined medium supplemented with either [14C] or [13C]-methyl labeled methionine. Cells were collected at the end of the log-phase of growth and tRNA was extracted. Analysis of the radioactivity of the [14C]-labeled tRNA established an incorporation ratio of three labeled carbons per tRNA molecule. Incorporation of the [14C]-label in vivo was confined to the methylation of nucleotides as determined by thin layer chromatography of nucleotides resulting from a ribonuclease digestion of [14C]-labeled tRNA. The carbon-13 NMR spectrum of [13C]-enriched tRNA indicated a similar degree of incorporation into the methylated nucleotides by the substantial enhancement of [13C]-methyl NMR signals only. Assignment of signals has been made for the methyl groups of ribothymidine and N7-methylguanosine in E. coli tRNA.     

Two novel oligosaccharides isolated from a beverage produced by fermentation of a plant extract

An extract from 50 kinds of fruits and vegetables was fermented to produce a new beverage. Natural fermentation of the extract was carried out mainly by lactic acid bacteria (Leuconostoc spp.) and yeast (Zygosaccharomyces spp. and Pichia spp.). Two new saccharides were found in this fermented beverage. The saccharides were isolated using carbon-Celite column chromatography and preparative high performance liquid chromatography. Gas liquid chromatography analysis of methylated derivatives as well as MALDI-TOF MS and NMR measurements were used for structural confirmation. The (1)H and (13)C NMR signals of each saccharide were assigned using 2D-NMR including COSY, HSQC, HSQC-TOCSY, CH(2)-HSQC-TOCSY, and CT-HMBC experiments. The saccharides were identified as beta-D-fructopyranosyl-(2-->6)-beta-D-glucopyranosyl-(1-->3)-D-glucopyranose and beta-D-fructopyranosyl-(2-->6)-[beta-D-glucopyranosyl-(1-->3)]-D-glucopyranose.     

Binding of mercury(II) to protein thiol groups: a study of proteinase K and carboxypeptidase Y.

Chemically modified enzymes have been prepared by incorporating an -Hg-L group into proteinase K and carboxypeptidase Y at the thiol groups of Cys-73 and Cys-341, respectively (L = CN- or I-). The -S-Hg-13CN group has been applied as a spectroscopic label for carbon-13 NMR spectroscopy.     

Evidence of land plant affinity for the Devonian fossil Protosalvinia (Foerstia)

The Devonian plant fossil Protosalvinia (Foerstia) has been examined by solid-state ¹³C nuclear magnetic resonance spectroscopy (NMR) and pyrolysis-gas chromatography-mass spectrometry (PY-GC-MS). Results of these studies reveal that the chemical structure of Protosalvinia is remarkably similar to that of coalified wood. A well-defined phenolic carbon peak in the NMR spectra and the appearance of phenol and alkylated phenols in pyrolysis products are clearly indicative of lignin-like compounds. These data represent significant new information on the chemical nature of Protosalvinia and provide the first substantial organic geochemical evidence for land plant affinity. ▭ Protosalvinia, Foerstia, Upper Devonian, biostratigraphy, carbon-13 NMR, PY-GC-MS, lignin.     

Production, extraction and purificationof violacein: an antibiotic pigment producedby Chromobacterium violaceum

A procedure for the production, extraction, and purification of violacein was developed using Chromobacterium violaceum (CCT 3496) cultivated on cotton, in modified 1 litre Roux bottles. A surface tray bioreactor was built to perform these experiments. Violacein was extracted with commercial ethanol, and purified by filtration, Soxhlet extraction, crystallization and high performance liquid chromatography. The violacein was analysed and identified by proton and carbon-13 NMR spectroscopies, thermogravimetric analysis, mass spectrometry, UV-VIS spectroscopy and infrared spectroscopy. It was concluded that the product was highly purified violacein.     

Analysis of the carbon-13 and proton NMR spectra of bovine chromaffin granules

Natural abundance carbon-13 and proton NMR spectra of bovine chromaffin granules have been obtained and analyzed using computer simulation techniques. High resolution spectra show the presence of a fluid aqueous phase containing epinephrine, ATP and a random coil protein. The protein spectrum contains unusually intense resonances due to glutamic acid and proline and has been simulated satisfactorily using the known amino acid composition of chromogranin A.The lipid phase of chromaffin granules gives rise to intense, but very broad, resonances in the carbon-13 spectrum. Protons in the liquid phase are also observable as a very rapid component of the proton-free induction decay ($\text{T}{}_2\text{? 15 μ}\text{s}$).Linewidths of the carbon-13 spectra have been used to set upper limits on rotational correlation times and on the motional anisotropy in the aqueous phase. These limits show that the aqueous phase is a simple solution (not a gel) that is isotropic over regions much larger than solute dimensions. No gel transition is observed between ?3 and 25°C. The carbon-13 spectra are definitely inconsistent with a lipoprotein matrix model and chromaffin granules previously proposed by Helle and Serck-Hanssen ((1975) Mol. Cell. Biochem. 6, 127–146). Relative carbon-13 intensities of ATP and epinephrine are not consistent with the known 1:4 mol ration of these components. This fact suggests that epinephrine and ATP are not directly complexed in intact chromaffin granules.