苦楝果多糖的分离纯化及组成分析

利用水提醇沉法提取苦楝果实中的多糖,经DEAE-52柱层析分离,得到MP1、MP2和MP3三个多糖组分,用Sephadex G-100凝胶色谱柱对MP1进行纯化鉴定,结果显示为单一峰。借助气质联用仪,对苦楝粗多糖和组分MP1进行了成分分析。红外光谱分析表明苦楝多糖的单糖残基以吡喃环和呋喃环的形式存在。     

拉曼光谱检测胃癌变信号的研究

利用激光拉曼光谱对胃癌患者血清及非胃癌患者血清进行对比检测,并结合对体外培养胃癌细胞分泌物的检测,对胃癌特征拉曼峰作初步探讨。得出一种有重要临床应用价值的癌症辅助快速诊断方法。     

抗重金属细菌与针铁矿体系吸附Cu~(2 )和Cd~(2 )的红外光谱研究

采用红外光谱技术探讨了抗重金属细菌NTG-01对针铁矿吸附Cu2 、Cd2 的影响。结果表明:①细菌细胞表面的游离羟基可以吸附Cu2 ;②加入细菌以后促进了Cu2 与针铁矿表面游离羟基(-OH)反应,使Cd2 与其表面的水合羟基(-OH2)的反应加强。     

稻麦叶片氮含量与冠层反射光谱的定量关系

作物氮素含量是评价作物长势、估测产量与品质的重要参考指标,叶片氮素含量的无损快速监测对于指导作物氮素营养的精确管理及生产力的预测预报具有重要意义.以5个小麦品种和3个水稻品种在不同施氮水平下的3a田间试验为基础,综合研究了稻麦叶片氮含量与冠层反射光谱的定量关系.结果显示：（1）不同试验中拔节后稻麦叶片氮含量均随施氮水平呈上升趋势;（2）稻麦冠层光谱反射率在不同施氮水平下存在明显差异,在可见光区（460～710 nm）的反射率一般随施氮水平的增加逐渐降低,而在近红外波段（760～1100 nm）却随施氮水平的增加逐渐升高;（3）就单波段光谱而言,610、660 nm和680 nm处的冠层反射率均与稻麦叶片氮含量具有较好的相关性;（4）在光谱指数中,归一化差值植被指数NDVI（1220,610）与水稻和小麦叶片氮含量均具有较好的相关性,且相关性好于单波段反射率;（5）对于小麦和水稻,可以利用共同的波段和光谱指数来监测其叶片氮含量,采用统一的回归方程来描述其叶片氮含量随单波段反射率和冠层反射光谱参数的变化模式,但若采用单独的回归系数则可以提高稻麦叶片氮含量估测的准确性.     

A facile synthesis of C-24 and C-25 oxysterols by in situ generated ethyl(trifluoromethyl)dioxirane

Experiments were performed to compare the regioselective hydroxylation of the isopropyl C-H bond at C-25 in 5α-cholestan-3β-yl acetate by in situ generated dimethyldioxirane, methyl(trifluoromethyl)dioxirane, hexafluoro(dimethyl)dioxirane or ethyl(trifluoromethyl)dioxirane (ETDO). The dioxiranes were generated from the corresponding ketones and potassium peroxymonosulfate in aq. NaHCO₃, pH 7.5-8.0. Of the four dioxiranes examined, partially fluorinated, sterically bulky ETDO displayed the highest reactivity and regioselectivity. Using in situ generated ETDO, a facile, synthesis was developed for two naturally occurring oxysterols, i.e., 25-hydroxycholesterol, as well as its 3-sulfate (overall yield of the sulfate, 24%) and 24-oxocholesterol (16%), starting from cholesterol.     

Immersion in CO<Subscript>2</Subscript>-rich water containing NaCl diminishes blood pressure fluctuation in anesthetized rats

Remarkably, bathing in hot springs containing high concentrations of carbon dioxide (CO₂) influences cardiovascular function more than bathing in fresh water. The CO₂-enriched water in hot springs generally contains many salts, whose interactions remain unknown. We separately evaluated the actions of individual factors in CO₂-enriched water and confirmed that CO₂ and NaCl have combined effects on blood pressure fluctuations in anesthetized rats. Animals equipped with sensor probes to monitor body temperature, skin blood flow and arterial blood pressure were immersed in bathwater (35°C) containing CO₂ with NaCl, KCl or sucrose. The effects of these factors on cardiovascular function were evaluated using power-spectral analysis of fluctuations in blood pressure and heart rate. Compared with immersion in tap water, heart rate and skin vascular resistance were reduced during immersion in CO₂-enriched water irrespective of the presence of other components. In terms of the very low frequency range (0.02–0.195 Hz), the power of blood pressure fluctuation during immersion was significantly reduced when the CO₂-enriched water contained more than 1.5% NaCl but was not influenced by other components of similar osmotic pressure and the same specific gravity. The results indicated that the coexistence of CO₂ and sodium ions in bathwater reduce blood pressure fluctuations, and suggested that this combination effect of CO₂ and salt contributes to the sedative effect on human cardiovascular functions while bathing in CO₂-hot springs.     

Caspase-3-mediated cleavage of Akt: involvement of non-consensus sites and influence of phosphorylation

Here, we show for the first time that Akt1 is cleaved in vitro at the caspase-3 consensus site DQDD(456) downward arrow SM. Our data suggest QEEE(116) downward arrow E(117) downward arrow MD, EEMD(119) downward arrow, TPPD(453) downward arrow QD and DAKE(398) downward arrow IM as novel non-consensus caspase-3 cleavage sites. More importantly, we demonstrate that phosphorylation of Akt1 modulates its cleavage in a site-specific manner: Resistance to cleavage at site DAKE(398) (within the kinase domain) in response to phosphorylation suggests a possible mechanism by which the anti-apoptotic role of Akt1 is regulated. Our result is important in biological models which rely on Akt1 for cell survival.     

The electronic structure of the C2H4O···2HF tri-molecular heterocyclic hydrogen-bonded complex: a theoretical study

The geometries of three isomers of the C₂H₄O···2HF tri-molecular heterocyclic hydrogen-bonded complex were examined through B3LYP/aug-cc-pVDZ calculations. Analysis of structural parameters, determination of CHELPG (charge electrostatic potential grid) intermolecular charge transfer, interpretation of infrared stretching modes, and Bader’s atoms in molecules (AIM) theory calculations was carried out in order to characterize the hydrogen bonds in each isomer of the C₂H₄O···2HF complex. The most stable structure was determined through the identification of hydrogen bonds between C₂H₄O and HF, (O···H), as well as in the hydrofluoric acid dimer, (HF^D–R···HF^D). However, the existence of a tertiary interaction (F^λ···H^α) between the fluoride of the second hydrofluoric acid and the axial hydrogen atoms of C₂H₄O was decisive in the identification of the preferred configuration of the C₂H₄O···2HF system. Figure Geometries of three isomers of the C₂H₄O···2HF tri-molecular heterocyclic hydrogen-bonded complex     

Localization of Pcb antenna complexes in the photosynthetic prokaryote Prochlorothrix hollandica

The freshwater filamentous green oxyphotobacterium Prochlorothrix hollandica is an unusual oxygenic photoautotrophic cyanobacterium differing from most of the others by the presence of light-harvesting Pcb antenna binding both chlorophylls a and b and by the absence of phycobilins. The pigment-protein complexes of P. hollandica SAG 10.89 (CCAP 1490/1) were isolated from dodecylmaltoside solubilized thylakoid membranes on sucrose density gradient and characterized by biochemical, spectroscopic and immunoblotting methods. The Pcb antennae production is suppressed by high light conditions (> 200 μmol photons m⁻² s⁻¹) in P. hollandica. PcbC protein was found either in higher oligomeric states or coupled to PS I (forming antenna rings around PS I). PcbA and PcbB are most probably only very loosely bound to photosystems; we assume that these pigment-protein complexes function as low light-induced mobile antennae. Further, we have detected α-carotene in substantial quantities in P. hollandica thylakoid membranes, indicating the presence of chloroplast-like carotenoid synthetic pathway which is not present in common cyanobacteria.     

Tracking single quantum dot and its spectrum in free solution with controllable thermal diffusion suppression

Thermal motions of semiconductor quantum dots (QDs) are suppressed on a dehydrated agarose-modified surface. The diffusion coefficients (D) of particles can be controlled by modifying the surface with an appropriate agarose concentration. The value of D is more than 100 times lower than the theoretical value when the dried agarose surface is made with an 8% agarose solution. This makes it possible to real-time record the diffusion process of single particles and single molecules in low-viscosity solution. A transmission grating installed in front of the charge-coupled device separates the QD fluorescence into the zeroth-order and first-order spectrum. Therefore, the spectrum of dynamic QDs is tracked on the modified surface. Tracking the dynamic QD spectral image is a promising method to explore the process of the molecular interactions in the physiological buffer.