A study of the conformational states of cyclopeptide systems

Summary 1. An empirical method for the quantitative determination of the number of NH groups of different types in peptides based on measurements of the integral intensity of the amide A bands in the IR spectra has been developed.2. The IR spectra of the diastereomeric cyclohexaalanyls in CHCl₃ solutions have been studied; they indicate the participation of an average of four NH groups in IMBHs.3. On the basis of a theoretical conformational analysis and of dipole-moment measurements, the system of IMHBs and the type of dominant conformation of the cyclohexapeptides in nonpolar solvents have been established.M. M. Shemyakin Institute of the Chemistry of Natural Compounds of the Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 347–357, May–June, 1971.     

Lipids of the oils of the fruit and leaves ofHoppopha? rhamnoides

The analysis of some lipids of four forms of the common sea buckthorn has shown that they all differ with respect to the composition of the fatty acids of the triacylglycerols of the leaves. One of the forms is characterized by an infringement of the specificity of the composition of the fatty acids in positions 2 of the triacylglycerols of the oils of the seeds and the leaves.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. V. L. Komarov Institute of Botany, Academy of Sciences of the Azerbaidzhan SSR, Baku. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 710–715, November–December, 1981.     

Spectral moments of phenylenes

In a series of publications Estrada (Estrada, E. J. Chem. Inf. Comput. Sci. 1996, 36, 844-849; 1997 37, 320-328; 1998, 38, 23-27) employed spectral moments of line graphs in QSPR and QSAR relationship studies of various classes of compounds. A recent paper (Markovi?, S.; Gutman, I. J. Chem. Inf Comput. Sci. 1999, 39, 289-293) reported that in QSPR and QSAR investigations of benzenoid hydrocarbons based on linear combination of spectral moments, it made no difference whether one used spectral moments of the molecular graph or those of the line graph. In the present work spectral moments of molecular graphs (Mk) and line graphs (muk) of phenylenes are considered. The first few Mk's and muk'S of phenylenes are dependent on identical structural parameters. It is proved that the two sets of moments of phenylenes are linearly dependent. It is also shown that in the case of the heat of formation of phenylenes there is no advantage in using lower spectral moments of line graphs instead of lower spectral moments of molecular graphs. In this way the redundancy observed in the case of benzenoid hydrocarbons is also shown to exist in the class of phenylenes.     

USE OF A pH-STAT DILUTION TO DETERMINE CRITICAL MICELLE CONCENTRATIONS AND COUNTERION CONCENTRATIONS OF IONIC MICELLES1

The use of a pH-stat to determine the critical micelle concentration (c.m.c.) of ionic micellar solutions is described. Counterion is released with the dilution of an ionic micellar solution at all concentrations above the c.m.c. The titration of the released counterion permits the evaluation of the c.m.c. and the associated amount of counterion for any concentration above the c.m.c. The diluent is the same medium in which the micelle is dissolved. Thus any ionic strength, ion composition, or pH may be used. Examples of the method to determine the c.m.c. of promethazine hydrochloride in water and of tetracaine hydrochloride in 0.128 N NaCl as a function of pH are given. Also the c.m.c of promethazine hydrochloride - Tween 80 mixtures was examined as a function of mole fraction.     

Äquidensitometrie: Eine Methode zur Beurteilung der Struktur von Plasmen—Qualitative Beurteilung des Lanthan-Gleichstrombogens durch Äquidensitometrie von monochromatischen Bogenphotographien

A new method has been developed for the experimental characterization of d.c. arc plasmas. The method consists of the combination of the spectral photography of d.c. arc plasmas with a slitless, stigmatic plane-grating spectrograph and the characterization of the photographs with the aid of photographic equidensitometry. The principles of the method are described. The method is used for the investigation of a lanthanum d.c. arc plasma. The qualitative results of the measurements of the axial distributions of the light emission and lanthanum and calcium particle concentrations in the arc are discussed. The limitations and shortcomings of the method are pointed out.     

Theoretical conformational analysis of the methylamide of N-acetyl-L-alanyl-L-prolyl-L-alanine. II

Summary 1. Spatial forms of Ac-L-Ala-L-Pro-L-Ala-NHMe with trans peptide bonds are the most preferred. Elongation of the peptide chain promotes the stabilization of the trans configuration of the tertiary amide group.2. In the structure of the compound investigated, the dominating role is played by the interaction of the neighboring residues.3. Of the six types of conformations of X-Pro-Y observed in proteins, the first four belong to the preferred forms of the Ac-L-Ala-L-Pro-L-Ala-NHMe molecule.M. M. Shemyakin Institute of Bioorganic Chemistry, Academy of Science of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 626–630, September–October, 1975.     

An investigation of the structure of the phospholipids of the cotton plant of variety Tashkent-2

Summary 1. The fatty-acid compositions of the total phospholipids of the seed kernels of the cotton plant of variety Tashkent-2, after the elimination of carbohydrates, and of their main components have been studied.2. It has been found that at 37–38°C the time of enzymatic hydrolysis is considerably shortened.3. A study of the products of acid and enzymatic hydrolysis has shown the structure of the individual phospholipids.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 145–148, March–April, 1976.     

Reaction of xylan with aqueous solutions of alkali

Conclusions 1. The action of an aqueous solution of caustic soda on xylan leads to the formation of both a molecular and an alkoxide form of this polysaccharide. The composition and amount of the alkoxide formed depend on the conditions of treating the xylan with alkali.2. In the reaction of an aqueous solution of caustic soda with xylan, the hydrogen of the alcohol grouping on the second carbon atom exhibits the greatest reactivity.3. The result of IR spectroscopy confirm the existence of a chemical interaction of the xylan with caustic soda.4. According to X-ray analysis, the action of a solution of caustic soda on xylan leads to a decrease in intermolecular interaction, to a more ordered supermolecular structure, and to the appearance of crystallinity.Khimiya Prirodnykh Soedinenii, Vol. 5, No. 4, pp. 206–210, 1969     

Micellization of Cetylpyridinium Chloride Using Conductometric Technique

Abstract

Conductometric technique has been used to investigate the equilibrium properties of cetylpyridinium chloride (CPC) in the presence of a series of aliphatic alcohols. The dependence of conductivity of surfactant solution in the presence of particular amount of alcohol has been studied. According to the experimental results, ethanol cause to decrease the dielectric constant and conductivity of micellar solution. Alcohols with longer chain may change the conductivity of solution depend on concentration of surfactant. At low concentration of CPC near critical micelle concentration (cmc) region, the minimum value of conductivity can be observed. This minimum value can be controiled by decreasing of free monomer concentration and also increasing degree of dissociation of micelle because of penetration of alcohols in micellar core. Using Conductometric technique cmc and α (degree of dissociation of counterion) of CPC were evaluated. The micelle formation of CPC has been considered in ethylene glycol (E.G)/ water and glycerol/water mixtures. It has been shown, the logarithm of cmc is directly depended on the ratio of E.G/water or glycerol/water.     

Interaction of carbamazepine and promethazine in rabbits

The interaction of carbamazepine and promethazine in rabbits has been investigated. The influence of this interaction on the processes of biotransformation in the liver was revealed. The drugs were administered as single oral doses (100 mg of each drug) as well as simultaneously with an interval of 15 min. The sequence of administration of the drugs was varied. The influence of promethazine on the pharmacokinetics of carbamazepine is expressed by: (a) strong suppression of carbamazepine's level in plasma and appearance of multiple peaks of carbamazepine; (b) suppression of biotransformation of carbamazepine into carbamazepine-10,11-epoxide at the initial stages and its increase in the intermediate stages. These data are explained by the active capture of carbamazepine by liver at its primary transferal through the liver and sufficient presystem elimination of carbamazepine in the presence of promethazine. The character of kinetic curves of promethazine varies substantially under the influence of carbamazepine. However, this change is not as strong as in case of carbamazepine. The concentration of promethazine in plasma varies slightly and multiple peaks are not observed. The rate of terminal elimination of promethazine varies and abrupt prolonged segments of elimination appear at the initial and terminal stages of the process in return. These data perhaps indicate the induction of biotransformation of promethazine in the presence of carbamazepine-an inductor of microsomal liver enzymes. The changes of kinetics of promethazine and carbamazepine by simultaneous administration as compared with their administration separately, as well as a comparative consideration of pharmacokinetics of promethazine and carbamazepine by simultaneous administration show the existence of competition in the elimination between these drugs and the periodic saturation of liver for their biotransformation.     

Photochemistry of tobacco mosaic virus RNA. Effect of HCN

Abstract— In attempting to sort out possible mechanisms of photoreactivation of tobacco mosaic virus RNA (TMV-RNA) inactivated by ultraviolet radiation (u.v.) in buffer of ionic strength 0.25, we have investigated the effect of HCN on the quantum yield for u.v. inactivation of TMV-RNA and on the percent photoreactivation of inactivated TMV-RNA. Some photo-products produced by irradiation of model substances, polyuridylic acid (poly U) and polycytidylic acid (poly C), in the presence of HCN have also been studied. The ratio of the quantum yield for inactivation of TMV-RNA in the presence of HCN to that in the absence of HCN is 1.5, under non-photoreactivating conditions. By comparison, the ratio of the initial rates of loss of uracil residues in poly U under comparable conditions is 1.6; by contrast, the rate of loss of cytosine residues in poly C is unaffected by HCN. This similarity of ratios between poly U and TMV-RNA suggests that two of the mechanisms of u.v. inactivation of TMV-RNA at high ionic strength are akin to known reactions of uracil residues in poly U, i.e. hydrate and dimer formation. The photohydration reaction in poly U, as measured by the heat reversal of hydrated residues to uracil residues, is almost abolished by HCN, and the rate of dimerization, as measured by the appearance of dimer containing oligonucleotides following enzymatic hydrolysis of irradiated poly U, is reduced to half by HCN. HCN does not affect the rate of hydration of cytosine residues in poly C. Since photoreactivation of RNA inactivated in presence of HCN is only 60 per cent of that in absence of HCN it is suggested that uracil dimers are somehow involved in photoreactivation of TMV-RNA inactivated at high ionic strength.     

聚乙烯醇对丙烯酰胺聚合行为的影响

<正> 聚乙烯醇(PVA)在烯类单体自由基聚合反应中作为分散剂使用已有很长历史,对于PVA在不同催化体系中与烯类单体接枝聚合的研究报道也不少,其中有人报道PVA对过硫酸盐的分解具有促进作用,并可导致甲基丙烯酸甲酯在PVA大分子上接枝;也有人报道了PVA与过硫酸铵在水溶液中的相互作用,本文研究了在低浓度过     

聚乙烯醇对N-取代丙烯酰胺聚合反应的影响以及它们间相互作用的研究

在前文研究聚乙烯醇(PVA)对丙烯酰胺聚合反应效应的基础上,本文进一步研究了PVA对N-取代丙烯酰胺衍生物聚合反应的影响。发现PVA对N-甲基丙烯酰胺的聚合反应亦有减速作用,且减速程度与添加的PVA量间有一定量关系。而PVA对N,N-二甲基丙烯酰胺的聚合反应就无此效应。为考察PVA同丙烯酰胺AM类单体间的相互作用,进行了粘度测定,并采用(化学电离)质谱的方法证实了AM及N-甲基丙烯酰胺同1,3-丙二醇间所存在的分子缔合作用。对缔合物的形或模式进行了探讨。     

微电极研究 III: Hg^2^+的电沉积过程的研究

研究了不同浓度的Hg^2^+在碳纤维微电极电沉积Hg的形态, 沉积机制和实验参数对汞膜性质及溶出电流的影响; 剖析了Hg的成核过程, 验证了成核理论; 借扫描电镜观察了汞晶体图象。约在6×10^-^5mol·L^-^1Hg^2^+时镀汞, 可形成密布型微汞滴构成的类汞膜, 微滴直径在0.03-0.2μm, 汞微滴密度约为5.7×10^6个/cm^2, 提出了优化汞膜的实验条件和依据。     

Internal sequence analysis of proteins separated on polyacrylamide gels at the submicrogram level: improved methods, applications and gene cloning strategies

The fields of protein chemistry and molecular biology are currently merging for study of biologically relevant events and conditions. To obtain partial sequences of microamounts of protein, efficient integration of high resolution separation and sequencing technologies is required. We report here on improved methods that allow extensive internal sequencing of 10 to 20 picomoles protein recovered from one- or two-dimensional gels. Each step of the standard protocol of Aebersold et al. (Proc. Natl. Acad. Sci. USA 1987, 84, 6970-6974) and the required instrumentation were examined and specifically adapted for use with submicrogram amounts of protein. Optimizations of in situ microdigests and liquid chromatography were needed for improved peptide recovery. Subsequent automated sequencing required subpicomole analysis. New methods for S-alkylation of gel-separated proteins and accurate identification of tryptophan-containing peptides were introduced to insure overall higher efficiencies. The acquired internal sequences facilitated cloning of the genes and several strategies are discussed. Applying our method, several proteins of unknown structure were sequenced and successfully identified or cloned. Internal sequences of submicrogram protein amounts, recovered from a single two-dimensional gel of Escherichia coli total protein (120 micrograms), allowed unambiguous identification of the spots but pre-gel enrichment will be required for analysis of most (90-95%) other spots. Integration of comprehensive two-dimensional gel protein databases with methods and strategies outlined here could potentially be an abundant source of DNA probes and markers useful for guidance of the human genome sequencing project and for analysis of the emerging vast amounts of data.     

Synthesis of new analogs of valinomycin and their properties. I

Conclusions 1. The synthesis of five valinomycin analogs differing by the configurations of the amino-acid and hydroxy-acid residues and also by the volumes of the radicals of the hydroxy-acid residues has been effected.2. The stability constants of the complexes of these analogs with potassium ions in ethanol solution have been determined.3. The antimicrobial activities of the compounds obtained have been studied and a correlation has been found between the degree of activity and stability of the complexes with K⁺.M. M. Shemyakin Institute of the Chemistry of Natural Compounds, Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 233–240, March–April, 1974.     

High-performance liquid chromatography of alkaloids

Literature information on the HPLC of alkaloids, including adsorption, reversed-phase, ion-exchange, ion-pair, and other variants is generalized. Results are given of the chromatographic analysis of various classes of alkaloids with an indication of the conditions of separation, and the columns used, and also of the methods of detection. The advantages and disadvantages of the HPLC variants are discussed. The review includes the literature over the last 14 years. Scientific Center for Chromatography, Institute of Chemistry and Physics of Polymers, Uzbek Academy of Sciences, Tashkent. Institute of the Chemistry of Plant Substances, Uzbek Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 595–613, September–October, 1991.     

Probing protein hydration and aging of food materials by the magnetic field dependence of proton spin-lattice relaxation times

Most cheeses can be considered as solid emulsions of milk fat in a matrix of water and proteins. Regions of each of the phases can be liquid during processing and maturation. Identifying these regions and monitoring changes in them is important as a prelude to controlling the structure of the final cheese. We concentrate on the behavior of water in the vicinity of proteins as a function of cheese aging. Our method utilizes nuclear magnetic relaxation dispersion (NMRD) associated with the frequency dependence of water spin-lattice relaxation rates using the field cycling NMR technique. This method provides insight into the dynamical behavior of water molecules on a very large time scale. Moreover, we can distinguish between molecular motion in bulk and motion in the vicinity of a source of relaxation, such as proteins. A fit of our dispersion data using a theory developed by J.-P. Korb and R.G. Bryant (J. Chem. Phys. 115 (2001) 23) allowed us to determine the degree of hydration of proteins as a function of aging. In particular, we find that protein hydration increases with ripening.     

Menthatrienes and the Oxidation of Limonene

The oxidation of limonene with mercuric acetate gives a mixture containing mentha-1. 3. 8-triene, the hydrocarbon of parsley, and its isomer, mentha-1. 4. 8-triene. Selenium dioxide oxidation of limonene in alcohol gives as the main product mentha-1. 8-dien-4-ol, and pyrolysis of the acetate of the latter, or of mentha-1. 8-dien-10-yl acetate (the main product of the oxidation of limonene with selenium dioxide in acetic anhydride), also gives a mixture of menthatrienes. A discussion of the selenium dioxide oxidation of limonene is presented.     

Complex conductivity of water-saturated packs of glass beads

The low-frequency conductivity response of water-saturated packs of glass beads reflects a combination of two processes. One process corresponds to the polarization of the mineral/water interface coating the surface of the grains. The other process corresponds to the Maxwell-Wagner polarization associated with accumulation of the electrical charges in the pore space of the composite medium. A model of low-frequency conductivity dispersion is proposed. This model is connected to a triple-layer model of electrochemical processes occurring at the surface of silica. This model accounts for the partition of the counterions between the Stern and the diffuse layers. The polarization of the mineral/water interface is modeled by the electrochemical polarization model of Schurr for a spherical grain. We take into account also the DC surface conductivity contribution of protons of the sorbed water and the contribution of the diffuse layer. At the scale of a macroscopic representative elementary volume of the porous material, the electrochemical polarization of a single grain is convoluted with the grain size distribution of the porous material. Finally, the Maxwell-Wagner polarization is modeled using the complex conductivity of a granular porous medium obtained from the differential effective medium theory. The predictions of this model agree well with experimental data of spectral induced polarization. Two peaks are observed at low frequencies in the spectrum of the phase. The first peak corresponds to the distribution of the size of the beads and the second peak is due to the roughness of the grains.