Crystal structure of quinone‐dependent alcohol dehydrogenase from Pseudogluconobacter saccharoketogenes. A versatile dehydrogenase oxidizing alcohols and carbohydrates

The quinone‐dependent alcohol dehydrogenase (PQQ‐ADH, E.C. 1.1.5.2) from the Gram‐negative bacterium Pseudogluconobacter saccharoketogenes IFO 14464 oxidizes primary alcohols (e.g. ethanol, butanol), secondary alcohols (monosaccharides), as well as aldehydes, polysaccharides, and cyclodextrins. The recombinant protein, expressed in Pichia pastoris, was crystallized, and three‐dimensional (3D) structures of the native form, with PQQ and a Ca²⁺ ion, and of the enzyme in complex with a Zn²⁺ ion and a bound substrate mimic were determined at 1.72 Å and 1.84 Å resolution, respectively. PQQ‐ADH displays an eight‐bladed β‐propeller fold, characteristic of Type I quinone‐dependent methanol dehydrogenases. However, three of the four ligands of the Ca²⁺ ion differ from those of related dehydrogenases and they come from different parts of the polypeptide chain. These differences result in a more open, easily accessible active site, which explains why PQQ‐ADH can oxidize a broad range of substrates. The bound substrate mimic suggests Asp333 as the catalytic base. Remarkably, no vicinal disulfide bridge is present near the PQQ, which in other PQQ‐dependent alcohol dehydrogenases has been proposed to be necessary for electron transfer. Instead an associated cytochrome c can approach the PQQ for direct electron transfer.     

Comparisons of cerebral circulation parameters in schoolchildren living in the Far East and European North

Transcranial Doppler sonography and impedansometry was used to study cerebral circulation in students aged from 7 to 17 living in the North in the "absolute discomfort" area (Magadan region. 62 degrees North, 158 degrees East, n = 167) and "discomfort" area (Arkhangelsk region, 61 degrees North, 41 degrees East, n = 52). New data were obtained about both blood flow parameters in main cerebral arteries, vessels tone and vasomotor reactivity as well as differences between these indices in children from the two northern areas. The results reveal that arterial blood flow velocity (BFV) in cerebral arteries is faster in Koryaks and Evens who are the children of the native population compared to BFV in the children born in the North whose parents represent newcomers. A tendency exists in the form of vascular tone rising in the living in the North students. This tendency is more expressed in children and adolescents from Magadan region which is distinguished from Arkhangelsk region by more severe climate. The indices that characterize individual alterations of cerebral circulation under hypoxic-cold factors as well as population peculiarities related to "polar adaptive type of metabolism" forming are discussed.     

新疆蓝刺头化学成分研究

以新疆蓝刺头(Echinops ritro L.)全草为研究材料,通过硅胶柱色谱,Sephadex LH-20柱色谱,重结晶等技术对新疆蓝刺头化学成分进行分离纯化,通过理化性质分析及1H-NMR,13C-NMR等技术对化合物结构进行鉴定.结果表明,共分离出5个化合物,分别是三萜类化合物蒲公英甾醇乙酰酯(化合物1)、蒲公英甾醇(化合物2)、黄酮苷类化合物金丝桃苷(化合物3)、胡萝卜苷(化合物4)与β-豆甾醇葡萄糖苷(化合物5).其中化合物1,2,5首次从该种植物中分离,化合物3为首次从该属植物中分离.     

宽窄行栽植模式下三倍体毛白杨根系分布特征及其与根系吸水的关系

采用剖面法对宽窄行栽植模式下三倍体毛白杨(triploid Populus tomentosa)的根系分布特征进行了研究;采用管式TDR系统对土壤剖面含水率变化动态进行了连续观测,并据此计算林木根系吸水速率,以探讨土壤含水率、根系分布和根系吸水分布之间的相关关系。研究结果表明:毛白杨的总平均根长密度在林带两侧和不同径向距离处非常接近(P>0.05);但在不同土层间变化很大(P<0.01),其中0-20和60-150 cm土层为根系主要分布区域,其根系所占比例共达86%;不同径阶间的根长密度差异显著(P<0.01),且其比例关系会随空间位置的改变而发生变化。不同栽植方位下,林带东侧毛白杨根系分布的浅层化程度高于西侧,且在径向240-280 cm内其0-0.5 mm的极细根显著多于西侧(P<0.05)。因此,宽窄行栽植模式下,深度和径阶是毛白杨根系分布的主要影响因子,而栽植方位会对其形态构型产生影响。毛白杨根系吸水模式受细根分布的影响,但会随土壤剖面水分有效性分布的变化而变化:当表土层水分有效性增加时,根系吸水主要集中在表土层;当表土层水分有效性降低时,深层土壤根系的吸水贡献率会逐渐增加;当土壤剖面水分条件异质性较高时,根系吸水主要集中在根系密度与水分有效性均较高的区域;当土壤剖面水分分布均匀且不存在水分胁迫时,根系吸水分布与细根分布最为一致。     

荔枝皮黄酮抑菌性能及其作用机理研究

采用荧光分析法测定荔枝皮中总黄酮含量,并研究了荔枝皮黄酮对常见4种微生物的抑菌活性及机理。结果表明,其黄酮纯度与得率分别为48%和13.61%;同时,采用牛津杯法测得荔枝皮黄酮对金黄色葡萄球菌、大肠杆菌和酵母菌的抑菌圈直径分别为15.1、14.0和13.8 mm;采用菌饼法测得对黑曲霉的抑菌率为28.75%。采用平板稀释法测得金黄色葡萄球菌和大肠杆菌的最低抑菌浓度MIC为2.5 mg/mL,最低杀菌浓度MBC为5mg/mL,而酵母菌和黑曲霉的MIC为5 mg/mL,没有杀菌能力。扫描电镜实验结果表明,荔枝黄酮的抑菌性和杀菌功能与其对金黄色葡萄球菌细胞和细胞壁结构的破坏直接相关。     

HPLC法测定银州柴胡中五种皂苷的含量

首次建立HPLC法同时测定银州柴胡中柴胡皂苷a、c、d、e和f五种皂苷含量的方法。流动相为乙腈-水梯度洗脱,柱子为HibarRT RP-18(4.6 mm×250 mm,5μm),流速1.0 mL/min,柱温30℃,检测波长210 nm。柴胡皂苷a、c、d、e和f的线性范围及相关系数分别为:21.78～43.56μg(r=0.9993),3.94～9.85μg(r=0.9994),20.68～51.70μg(r=0.9998),1.67～5.57μg(r=0.9997),1.91～6.70μg(r=0.9992);柴胡皂苷a、d的加样回收率分别为101.5%和98.5%。该方法操作简便,结果准确,重现性好,为柴胡药材多指标质量分析方法的建立和银州柴胡药用提供了参考依据。     

反相高效液相色谱法测定升麻药材中升麻苷H-1的含量

建立升麻药材中升麻苷H-1含量测定的反相高效液相色谱分析方法。使用H&E XP ODS-A色谱柱(4.6 mm×250 mm5,μm),流动相为乙腈-水-磷酸(35∶65∶0.4),流速为1 mL/min,柱温为26℃,检测波长203nm。测得升麻苷H-1线性范围为0.95～28.5μg/mL(r=0.9999),平均回收率(n=6)为99.35%(RSD=2.79%),不同来源批次升麻药材含量测定结果表明,升麻药材中升麻苷H-1含量为0.53%～1.09%,综合分析批样品含量测定结果,建议升麻药材中含升麻苷H-1应不低于0.4%。本方法简便、准确、重复性好、专属性强,可作为升麻药材质量控制方法。     

Exogenous proteins in exhaled human breath condensate

In the course of analysis of protein composition of exhaled breath to diagnose diseases of the respiratory system the problem is raised to distinguish between proteins, expressed in lung tissues and in respiratory tract (endogenous) and those that got into the respiratory system from the ambient air in the process of respiration (exogenous). In this work, an attempt is made to estimate the constitution of exogenous proteins in exhaled air with mass spectrometry and nanoflow high performance liquid chromatography (nano-HPLC). Six months’ indoors isolation of healthy donors with air being cleaned of dust leads to the removal from the spectrum of exhaled proteins of some keratins that are therefore considered to be exogenous. Nonkeratin proteins may also circulate between ambient air and human airways, but their concentration appears to be significantly lower than keratin concentrations (especially than the epidermis keratin). Among nonkeratins, dermicidin seems to be the most significant exogenous protein of the exhaled air. Conclusions concerning the diagnostic value of exhaled proteins can be made only after careful comparison of results of quantitative and qualitative analyses of their normal and pathological composition for a statistically significant sample of donors.     

GABA_A受体在酒精依赖中作用的研究进展

酒精依赖的产生机制是由特定的GABAA受体亚单位介导的,并且能够影响其它GABAA受体亚单位,使其对一定剂量的酒精敏感。此外酒精还可以通过细胞内信号转导途径影响GABA在大脑不同区域及核团单元的表达。焦虑、抗惊厥、镇静催眠、认知功能障碍等由酒精依赖产生的现象或者机制,均与GABA受体的介导有关。这些机制包括酒精对GABAA受体的直接或间接的作用,以及GABA的合成和释放。因此对GABAA受体功能的研究,将有助于人们关注酒精依赖现象及其治疗手段,为寻找酒精依赖治疗药物和治疗酒精中毒的机制的提供新线索。