Microhydrodynamics simulation of protein crystallization. I. Static calculations.

A computer simulation method is proposed to study the effects of hydrodynamic interactions on protein crystallization. It is a combination of Stokesian dynamics and continuum hydrodynamics and is referred to as "microhydrodynamics." The method is checked against analytical expressions for Stokes drag and diffusion coefficients for unit spheres. For a number of protein molecules the diffusion coefficients have been calculated and compared with experimental values. It is shown that the method works well for stationary calculations. Using dynamical calculations interacting protein molecules will be simulated to study the events in the early stages of protein crystallization.     

Purification of cardiac myosin. Application to hypertrophied myocardium.

A method is described for the preparation of high purity myosin from small amounts of cardiac muscle. The method employs homogenization and prolonged extraction of the cardiac tissue. Purification is achieved through three successive precipitation-dissolution cycles and without the use of column chromatographic techniques. Purity of the myosin preparation is assessed at various stages of the purification procedure by sodium dodecylsulfate-acrylamide gel electrophoresis and by measurement of RNA and nucleoprotein content. With 1.5-2.0 g of rabbit right ventricle as the starting tissue, this method yields 4-6 mg myosin per g wet tissue. The method is also shown to give similar results with rabbit right ventricles hypertrophied by pulmonary stenosis.     

Estimation of polyhydroxy alcohols in fermentation broths. 2. Quantitative analysis based on t.l.c/f.i.d

A simple and rapid method for the quantitative analysis of polyhydroxy alcohols in fermentation broths has been developed. The method is based on thin layer chromatography (t.l.c.) coupled with a flame ionization detector (f.i.d.) and has been found to be useful in the screening of cultures for fermentative glycerol production.     

Results of phalloplasty.

We present our experience with a method of phalloplasty which can be applied by reconstructive surgeons to cases of penile loss from diverse etiologies. The complications with this method have been frequent, but not life-threatening. Achievement of the stated objectives is obtained in a sufficiently high proportion of cases to make this a method whorthwhile to use until a clearly superior method can be demonstrated.     

Indices of oxidative stress. 2. Lipid peroxides

Two methods of the determination of lipid peroxidation products have been compared which are based on Fe(II) oxidation by them at acid pH values in the presence of xylenol orange which binds Fe(III) have been compared. The first method uses cumene hydropeoxide as an internal standard. In the second one, lipid peroxides are previously reduced by triphenylphosphine and these substances content is measured as a difference of the production of complexes with xylenol orange and iron ions in the control (with reduction) and experimental sample (without reduction). The optimization of measurement conditions is described. The levels of lipid peroxides in goldfish tissues assayed simultaneously by two methods were similar. The method with cumene hydroperoxide needs less amounts of biological material; moreover, there is no necessity in a calibration curve. Effects of hyperoxia on lipid peroxide levels in goldfish tissues were studied with the cumene method. Within the first hours of hyperoxia this index increased 13-times in the liver and 2-times in the brain and muscle. The further exposure rebounded this parameter to the initial level. Levels of lipid peroxides positively correlated with levels of end products of lipid peroxidation (thiobarbiturate acid reactive substances) in the goldfish tissues. The method of quantification of lipid peroxides with cumene is recommended for wide using in biological investigations.     

Enzymatic determination of biotin.

An enzymatic method for the quantitative determination of biotin has been developed. The method involves the enzymatic binding of biotin in situ to the pyruvate carboxylase apoprotein of biotin-deficient bakers' yeast and the subsequent estimation of the pyruvate carboxylase activity by a ¹⁴CO₂-fixation method. The method is specific for biotin. Several biotin analogs and precursors were tested, and only biocytin was found to interfere, Biotin amounts of less than 5 pg can be estimated.     

Comparison of cold enrichment and U.S. Department of Agriculture methods for isolating Listeria monocytogenes from naturally contaminated foods. The Listeria Study Group.

We compared the cold enrichment (CE) and U.S. Department of Agriculture (USDA) methods for isolating Listeria monocytogenes by examining 402 food samples. The food samples were collected from refrigerators of listeriosis patients as part of a multistate active surveillance project to determine the role of foods in sporadic listeriosis in the United States. L. monocytogenes was isolated from 51 food samples (13%). The USDA method was significantly better (P less than 0.001) than the CE method. The isolation efficiencies of the USDA and CE methods were 96 and 59%, respectively. Quantitation of L. monocytogenes in the food samples revealed that many food samples containing less than 0.3 CFU/g were negative as determined by the CE method but positive as determined by the USDA method.     

Identification of F. o. cucumerinum and F. o. luffae by RAPD-generated DNA probes

AIMS: To create a fast, sensitive and specific method for identifying Fusarium oxysporum f. sp. cucumerinum and F. o. luffae. METHODS AND RESULTS: Specific DNA bands were selected as probes from RAPD profiles of 13 formae speciales of F. oxysporum. The forma specialis-specific probe OPC18300c and OPC18520f could be used to identify F. o. cucumerinum and F. o. luffae by RAPD-PCR followed dot blot hybridization, respectively. CONCLUSIONS: A specific method for identifying F. o. cucumerinum and F. o. luffae was achieved. SIGNIFICANCE AND IMPACT OF THE STUDY: F. oxysporum formae speciales identification with a DNA probe can be relatively rapid and provides a method to identify the pathogen without host inoculation tests.     

Comparison of cold enrichment and U.S. Department of Agriculture methods for isolating Listeria monocytogenes from naturally contaminated foods. The Listeria Study Group.

We compared the cold enrichment (CE) and U.S. Department of Agriculture (USDA) methods for isolating Listeria monocytogenes by examining 402 food samples. The food samples were collected from refrigerators of listeriosis patients as part of a multistate active surveillance project to determine the role of foods in sporadic listeriosis in the United States. L. monocytogenes was isolated from 51 food samples (13%). The USDA method was significantly better (P less than 0.001) than the CE method. The isolation efficiencies of the USDA and CE methods were 96 and 59%, respectively. Quantitation of L. monocytogenes in the food samples revealed that many food samples containing less than 0.3 CFU/g were negative as determined by the CE method but positive as determined by the USDA method.     

A p.m.r. isotope-exchange method for studying the kinetic properties of dehydrogenases in intact cells.

A method to determine the activity of dehydrogenases in an intact-cell system is described. The method involves the use of n.m.r. to monitor bulk isotope exchange. The approach is illustrated by application to the isotope equilibration of pyruvate and lactate as catalyzed by lactate dehydrogenase in intact erythrocytes. Particular problems peculiar to bulk isotope exchange and its observation by n.m.r. are considered.     

Capillary electrophoresis analysis of mangiferin extracted from Mangifera indica L. bark and Mangifera persiciformis C.Y. Wu et T.L. Ming leaves

The flavonoid compound mangiferin is found in the leaves, stem bark, fruit peels and root of Mangifera indica L. and in many other herbal species with many potential pharmacological properties. We have established an analytical method of mangiferin extracted from M. indica L. bark and Mangifera persiciformis C.Y. Wu et T.L. Ming leaves utilizing CZE. An electrolytic buffer containing 0.05 M borate buffer, pH 7.4 with methanol (1:0.3, v/v) was deemed suitable for mangiferin analysis. An ideal mangiferin electropherogram with a migration time at approximately 10.50 min was obtained. Repeatability tests showed that the R.S.D.s for both intra- and inter-day migration time and peak area for all manigferin sources tested were less than 4%. The linearity range of this method was 5-1000 microg/ml. The detection limit of this method was 1.5 microg/ml. Quantitative analysis of mangiferin was also performed with this method. The accuracy of quantitation at 10, 500 and 1000 microg/ml of control mangiferin were 99.00, 99.38 and 99.14%, respectively (n=10). The repeatability of quantitation (R.S.D.) was below 3%. Our results demonstrated that CZE is a simple and reliable method in mangiferin analysis and more studies are needed to detect other mangiferin resources, such as clinical biological samples, in pharmacology and pharmacokinetic studies.     

Neutron off-plane scattering of aligned membranes. I. Method Of measurement.

We describe a method of measuring neutron scattering of aligned membranes with the momentum transfer oriented parallel or partly perpendicular to the plane of the membranes. The method obtains the complete information for the structures within fluid membranes obtainable by scattering. Data from alamethicin- and magainin-induced pores are presented. Although the in-plane scattering curves of these two peptides are similar to each other, their off-plane scattering patterns are strikingly distinct. Magainin pores exhibit intermembrane correlations.     

A new spectrophotometric assay for enzymes of purine metabolism. II. Determination of guanase activity.

A new method for the determination of guanase is described. Xanthine, the product of the guanase reaction, is oxidized by xanthine oxidase, forming uric acid and hydrogen peroxide. Hydrogen peroxide is further reduced to water by catalase in the presence of ethanol. The acetaldehyde formed in this reaction step is dehydrogenated NAD or NADP dependent by aldehyde dehydrogenase. The NADH or NADPH production is measured and utilized for the calculation of the guanase activity. The sensitivity of the method can be doubled by the addition of uricase, which oxidizes uric acid to permit the formation of another mole of hydrogen peroxide.     

红果人参叶片RNA的提取

提取高质量的RNA是进行人参植物分子生物学研究的必要前提.利用CTAB法、Trizol法、Bizol法和SDS法,从红果人参叶片中提取了总RNA,通过紫外分光光度法和凝胶电泳检测,结果显示:四种方法得到的纯度都比较高,OD260/OD280值都在1.7～2.0之间;SDS法提取的RNA,凝胶电泳显示28S条带是18S条带亮度两倍,而且无污染,好于其他三种方法.通过KT-PCK,ds cDNA片段条带弥散分布大小在0.2～3.0kb,从而进一步验证了SDS法提取的RNA质量,完全可以进行下一步的分子生物学研究     

13C-n.m.r. study of C hordein.

Insoluble xylan was prepared from ground birch (Betula pubescens) pulp by alkali extraction and precipitation with ethanol. The only sugar detected after acid hydrolysis of the preparation was xylose. The insoluble xylan was used as substrate in a nephelometric assay to determine the xylanase (EC 3.2.1.8, 1,4-beta-D-xylan xylanohydrolase and EC 3.2.1.37, 1,4-beta-D-xylan xylohydrolase) activities of Aspergillus and Trichoderma enzymes. The nephelometric method is reliable in evaluating xylanase hydrolysis of insoluble xylan.     

Application of spin-echo nuclear magnetic resonance to whole-cell systems. Membrane transport.

A new method for studying membrane transport is presented. High resolution n.m.r. is used to measure the distribution of small molecules between the intracellular and extracellular compartments. The method uses spin-echo techniques and relies on a difference in the magnetic susceptibility of the media inside and outside of cells. It also provides simultaneous information on the metabolic status of the cell. The method is illustrated by a study of alanine and lactate transport in the human erythrocyte.     

A new spectrophotometric assay for enzymes of purine metabolism. I. Determination of xanthine oxidase activity.

A new method for the determination of xanthine oxidase activity with xanthine or hypoxanthine is described. The hydrogen peroxide produced by the oxidation of the substrates is reduced by catalase in the presence of high concentrations of ethanol. The acetaldehyde formed is further oxidized by aldehyde dehydrogenase NAD or NADP-dependent. The reduction rate of the coenzymes were measured at 334 nm and utilized as indicators for the xanthine oxidase. The sensitivity of the method with xanthine as substrate can be doubled by the addition of uricase, which oxidizes uric acid to allantoin.     

Enzymatic microdetermination of glycogen.

A method for the determination of isolated glycogen was developed. Glucose was released from glycogen with an amyloglucosidase from Rhizopus. The released glucose was determined with glucose oxidase and peroxidase utilizing diammonium 2,2′-azino-di-[3-ethyl-benzthiazoline sulfonate (6)] (ABTS) as a chromogenic substrate. The ABTS method was found to be three times as sensitive as the older o-dianisidine method. For rabbit liver glycogen, the results obtained with amyloglucosidase correlated highly with those obtained by acid hydrolysis.     

Standardisation of Gymnema sylvestre R.Br. by high-performance thin-layer chromatography: an improved method

An improved high-performance thin-layer chromatographic (HPTLC) method for the standardisation of Gymnema sylvestre is reported. The method involves the initial hydrolysis of gymnemic acids, the active ingredients, to a common aglycone followed by the quantitative estimation of gymnemagenin. The present method rectifies an error found in an HPTLC method reported recently.     

Solid-phase synthesis of polynucleotides. II. Synthesis of polythymidylic acids by the block coupling phosphotriester method.

Synthesis of two oligothymidylic acids, tridecamer and nonadecamer, is described by a rapid and simple solid-phase method on two kinds of polyacrylamide supports derivatized from commercially available Enzacryl Gel K-2. The syntheses were performed by the phosphotriester method using di- and tri-thymidylic acid blocks as the incoming 3'-phosphodiester component. High coupling yields were consistently obtained and the final product was isolated very easily by high performance liquid chromatography on Permaphase AAX.