Enantioselective determination of isradipine in human serum using chiral stationary phase liquid chromatography and gas chromatography with nitrogen selective detection

rac-Isradipine is a dihydropyridine type calcium antagonist. Its calcium entry blocking effect is due primarily to the (+)-(S)-enantiomer. This study describes a sensitive enantioselective method for the determination of isradipine in human serum. Following alkaline extraction into hexane, the enantiomers of isradipine are separated quantitatively by high-performance liquid chromatography on a Chiralcel OJ column at 39°C. The collected fractions were evaporated and assayed using capillary gas chromatography on a HP 50+ column with nitrogen selective detection. Using 2.0 ml of serum, 0.7 nmol/1 (0.26 ng/ml) of each enantiomer could be determined with acceptable precision. The method has successfully been used to measure (+)-(S)- and (−)-(R)-isradipine concentrations in samples from volunteers after intravenous and oral administration of isradipine. Chirality 10:808–812, 1998. © 1998 Wiley-Liss, Inc.     

Determination of drug levels in human serum by circular dichroism

A study of the applicability of circular dichroism (CD) for the determination of drug levels in human serum is described and a new method for the quantitative determination of optically active absorbing drugs having Cotton effects at wavelengths above 250 nm in human serum and/or plasma is proposed. The principal advantages of this method are speed, economy, and simplicity, no derivatization or chromatographic separation steps being needed. The validity of the CD determination was confirmed by analysis of variance, β-lactam antibiotics being chosen as model drugs. In addition, the validation studies performed confirm the accuracy and precision of the proposed method. For β-lactam antibiotics lacking Cotton effects above 250 nm, an alternative method based on the extraction of the drug from serum is considered. Chirality 10:507–512, 1998. © 1998 Wiley-Liss, Inc.     

popharvest: An R package to assess the sustainability of harvesting regimes of bird populations

Bird harvest for recreational purposes or as a source for food is an important activity worldwide. Assessing or mitigating the impact of these additional sources of mortality on bird populations is therefore crucial issue. The sustainability of harvest levels is however rarely documented, because knowledge of their population dynamics remains rudimentary for many bird species. Some helpful approaches using limited demographic data can be used to provide initial assessment of the sustainable use of harvested bird populations, and help adjusting harvest levels accordingly. The Demographic Invariant Method (DIM) is used to detect overharvesting. In complement, the Potential Take Level (PTL) approach may allow setting a level of take with regard to management objectives and/or to assess whether current harvest levels meet these objectives. Here, we present the R package popharvest that implements these two approaches in a simple and straightforward way. The package provides users with a set of flexible functions whose arguments can be adapted to existing knowledge about population dynamics. Also, popharvest enables users to test scenarios or propagate uncertainty in demographic parameters to the assessment of sustainability through easily programming Monte Carlo simulations. The simplicity of the package makes it a useful toolbox for wildlife managers or policymakers. This paper provides them with backgrounds about the DIM and PTL approaches and illustrates the use of popharvest''s functionalities in this context.     

A new method for modeling large-scale rearrangements of protein domains

A method for modeling large-scale rearrangements of protein domains connected by a single- or a double-stranded linker is proposed. Multidomain proteins may undergo substantial domain displacements, while their intradomain structure remains essentially unchanged. The method allows automatic identification of an interdomain linker and builds an all-atom model of a protein structure in internal coordinates. Torsion angles belonging to the interdomain linkers and side chains potentially able to form domain interfaces are set free while all remaining torsions, bond lengths, and bond angles are fixed. Large-scale sampling of the reduced torsion conformational subspace is effected with the “biased probability Monte Carlo-minimization” method [Abagyan, R.A., Totrov, M.M. (1994): J. Mol. Biol. 235, 983–1002]. Solvation and side-chain entropic contributions are added to the energy function. A special procedure has been developed to generate concerted deformations of a double-stranded interdomain linker in such a way that the polypeptide chain continuity is preserved. The method was tested on Bence-Jones protein with a single-stranded linker and lysine/arginine/ornithine-binding (LAO) protein with a double-stranded linker. For each protein, structurally diverse low-energy conformations with ideal covalent geometry were generated, and an overlap between two sets of conformations generated starting from the crystallographically determined “closed” and “open” forms was found. One of the low-energy conformations generated in a run starting from the LAO “closed” form was only 2.2 Å away from the structure of the “open” form. The method can be useful in predicting the scope of possible domain rearrangements of a multidomain protein. Proteins 27:410–424, 1997. © 1997 Wiley-Liss, Inc.     

Reversible binding interactions between the tryptophan enantiomers and albumins of different animal species as determined by novel high performance liquid chromatographic methods: an attempt to localize the D- and L-tryptophan binding sites on the human serum albumin polypeptide chain by using protein fragments

The stereoselectivity of the reversible binding interactions between the D- and L-tryptophan enantiomers and serum albumins of different animal species and fragments of human serum albumin (HSA) was investigated by applying three novel high performance liquid chromatographic (HPLC) arrangements. The separations were performed by means of (1) an achiral (diol-bond), (2) a chiral (bovine serum albumin-bond) silica gel sorbent, and (3) a column switching technique which uses both the diol- and HSA-bond HPLC stationary phases. A polarimetric detector and/or an ultraviolet (UV) spectrophotometer were used to monitor the separation process. HPLC arrangement 3 allowed the evaluation of enantioselective binding for D- and L-tryptophan to different albumins and albumin fragments. At present, column switching can be considered the technique of the broadest applicability for investigating the reversible binding interactions between a protein and drug enantiomers. Chirality 9:373–379, 1997. © 1997 Wiley-Liss, Inc.     

粪便学在有蹄类动物数量调查研究中的应用与展望

随着与分子生物学的结合,传统的粪便学不仅拓宽了在种群生态学、行为生态学及保护遗传学等研究时取样的范围,而且能提供更多的有效信息,使得传统的粪便计数方法得以在新的领域里发展。本文对传统粪便学在有蹄类动物数量研究中的应用加以总结,并结合国内外研究现状对分子粪便学在这一领域内的可靠性、局限性及应用前景做了概述。     

中国香菇种质资源中两种主要病毒的携带情况检测

香菇病毒病通常具有潜隐性特征,携带病毒的香菇菌株往往并不表现出明显症状,但一旦爆发常造成较大经济损失。本文采用RT-PCR检测技术,系统分析了中国香菇野生种质及栽培种质中两种主要病毒Lentinula edodes mycovirus HKB（LeV-HKB）和L. edodes partitivirus 1（LePV1）的携带情况。对来源于中国主要栽培省（市）的90个香菇栽培菌株的检测结果表明,有67.8%（61/90）的供试菌株单独或复合感染有LeV-HKB和LePV1中的1种或2种,LeV-HKB病毒携带率56.7%（51/90）,明显高于LePV1 35.6%（32/90）;栽培菌株两种病毒的复合感染率为24.4%（22/90）。对地理来源几乎覆盖整个中国的125个野生菌株的检测结果表明,有75.2%（94/125）的供试菌株至少感染了LeV-HKB和LePV1中的1种,8.8%（11/125）野生菌株同时感染了两种病毒,且野生菌株中LePV1病毒携带率70.4%（88/125）明显高于LeV-HKB 13.6%（17/125）。栽培菌株和野生菌株中LeV-HKB和LePV1病毒的存在与否与菌株地理来源没有明显相关性,显示香菇病毒极可能通过担孢子在自然界广泛传播。本研究为开展香菇菌种病毒病快速检测,从源头控制香菇病毒病传播,追踪病毒病的发生流行规律奠定了基础。     

Aspergillus sp. EA-LJS80的分离及其发酵液提取物七叶皂苷C的生物活性

本研究从陕西留坝紫柏山采集的七叶树Aesculus chinensis根和茎中分离出一株具有高产七叶皂苷C的内生真菌,将其编号为EA-LJS80。利用ITS序列分析鉴定其种属并对其形态进行观察;采用紫外-可见分光光度计进行全波长扫描,确定其最大紫外吸收峰;采用HPLC测定七叶皂苷C的产量;采用滤纸片扩散法研究其发酵液提取物的抑菌活性;采用CCK-8法测定提纯后七叶皂苷对肺腺癌A₅₄₉细胞的增殖抑制率,探究其生物活性。结果显示,该菌株EA-LJS80为曲霉菌属Aspergillus真菌,最大紫外吸收波长为230nm,测得提纯后七叶皂苷C的产量为9.23mg/mL。生物活性实验表明：菌株EA-LJS80的发酵液提取物对大肠杆菌Escherichia coli等4种致病菌有明显的抑菌效果;经CCK-8法测定,提纯后的七叶皂苷对肺腺癌A₅₄₉细胞的增殖有明显的抑制作用。综上所述,菌株EA-LJS80具有产七叶皂苷活性,尤其是七叶皂苷C的产量较高,且其产生的七叶皂苷具有较高的生物活性,这对于改进七叶皂苷生产模式,提高生产效率具有重要意义,同时对于七叶皂苷C的进一步研究有一定的促进作用。     

向日葵茎芯多糖的提取工艺优化及其体外抗肿瘤活性研究

研究了向日葵茎芯中主要活性物质多糖的提取工艺,并对此工艺进行了优化,选取的提取方法为水提醇沉法,以多糖含量作为指标,采用单因素试验研究了提取次数、原料颗粒的大小（目数）、料液比、提取时间、提取温度对向日葵茎芯多糖含量的影响。用苯酚-硫酸法测定提取液中多糖的含量,得出向日葵茎芯中多糖的最佳提取工艺条件为：提取次数2次,原料颗粒的大小（目数）60~80目,料液比（g·mL^-1）1：50,提取时间3.0 h,提取温度90℃,在最优提取条件下,多糖的提取得率为6.56%,多糖的含量为266.03 mg·g^-1。本文也对多糖的体外抗肿瘤活性进行了研究,结果表明向日葵茎芯多糖的体外抗肿瘤活性较弱。这些条件的确定为向日葵茎芯的深入研究奠定了基础。