排序方式: 共有32条查询结果,搜索用时 15 毫秒
1.
In general, peptides do not exhibit a well-defined conformational profile in solution. However, despite the experimental blurred picture associated with their structure, compelling spectroscopic evidence shows that peptides exhibit local order. The conformational profile of a peptide is the result of a balance between intramolecular interactions between different atoms of the molecule and intermolecular interactions between atoms of the molecule and the solvent. Accordingly, the conformational profile of a peptide will change upon the properties of the solvent it is soaked. To get insight into the balance between intra- and intermolecular interactions on the conformational preferences of the peptide backbone we have studied the conformational profile of the alanine dipeptide in diverse solvents using molecular dynamics as sampling technique. Solvents studied include chloroform, methanol, dimethyl sulfoxide, water and N-methylacetamide. Different treatments of the solvent have been studied in the present work including explicit solvent molecules, a generalized Born model and using the bulk dielectric constant of the solvent. The diverse calculations identify four major conformations with different populations in the diverse solvents: the C7eq only sampled in chloroform; the C5 or extended conformation; the polyproline (PII) conformation and the right-handed α-helix conformation (αR). The results of present calculations permit to analyze how the balance between intra- and intermolecular interactions explains the populations of the diverse conformations observed. 相似文献
2.
The complex of lanthanum chloride with Glycine and Alanine,La(Gly)2(Ala)3Cl3·2H2O,was synthesized and characterized by IR,elementary analysis,thermogravimetric analysis,and chemical analysis.The dissolution enthalpies of LaCl3 ·7H2O(s),2Gly(s) 3Ala(s)and La(Gly)2(Ala)3Cl3 ·2H2O(s)were determined in 2 mol·L-1 HCl by a solution-reaction isoperibol calorimeter.By designing a thermochemical cycle in terms of Hess' Law and through calculation,the reaction enthalpy of lanthanum chloride seven-hydrate with Glycine and Alanine was obtained:ΔrHθm(298.15 K)=(29.652±0.504)kJ·mol-1,and the standard enthalpy of formation of La(Gly)2(Ala)3Cl3·2H2O(s)ΔfHθm [La(Gly)2(Ala)3Cl3·2H2O,s,298.15 K]=-4467.6±8.3 kJ·mol-1. 相似文献
3.
4.
用标准丙氨酸剂量计对ER-200D型电子顺磁共振仪进行标定,并利用这一标定结果对合肥国家同步辐射实验室的200MeV直线加速器周围的辐射场进行了测量,获得了满意的结果。 相似文献
5.
In this report, the results of preliminary research on L-alanine/ESR electron dosimeters are described. They include the designs of modelling tools and experimental capsules, the preparation and irradiation of very thin dosimeters, the measurement of ESR signal spectrum and the calibration method. The physical, chemical and dosimetric properties of the alanine free radical dosimeters, such as the smallest thickness, average density, lowest detectable limit, repeatability of the method, reproducibility resulted in directivity and location in resonance cavity, linearity regions as well as relative scattering of the response to identical doses, are summarized. 相似文献
6.
3,4-Dihydroxyphenylalanine (DOPA) was covalently grafted onto a glassy carbon electrode (GCE) by the formation of an amine cation radical in the electro-oxidation of the amino-containing compound. Cyclic voltammetric experiments proved that the DOPA was formed on the GCE as a monolayer. Its electron transfer over the GCE surface at different pH values was studied by cyclic voltammetry. Changes in solution pH resulted in the variation of the charge state of the terminal group and the surface pKa was estimated on the basis of these results. Because of electrostatic interactions between the negatively charged groups on the electrode surface and the alanine (Ala) in solution, the modified electrode was used as an enantioselective sensor. The peak current for d(+) or l(−)DOPA over the modified electrode decreased as a result of the chiral recognition across the blocking interaction with the respective enantiomer of l(−) or d(+)Ala. The recognition was verified with the protection of l(−)DOPA with a Fmoc group. 相似文献
7.
D-丙氨酸的用途及制备方法 总被引:9,自引:0,他引:9
介绍了D-丙氨酸在生理医学,食品工业等方面的应用,及目前它的各种生产方法。并对建立D-丙氨酸的工业生产方法提出了建议。 相似文献
8.
The complex of lanthanum chloride with Glycine and Alanine, La(Gly)2(Ala)3Cl3·2H2O, was synthesized and characterized by IR, elementary analysis, thermogravimetric analysis, and chemical analysis. The dissolution enthalpies of LaCl3 ·7H2O(s), 2Gly(s) + 3Ala(s) and La(Gly)2(Ala)3Cl3 ·2H2O(s) were determined in 2 mol·L-1 HCl by a solution-reaction isoperibol calorimeter. By designing a thermochemical cycle in terms of Hess′ Law and through calculation, the reaction enthalpy of lanthanum chloride seven-hydrate with Glycine and Alanine was obtained: ΔrHθm (298.15 K)=(29.652±0.504) kJ·mol-1, and the standard enthalpy of formation of La(Gly)2(Ala)3Cl3·2H2O(s) ΔfHθm [La(Gly)2(Ala)3Cl3·2H2O, s, 298.15 K]=-4467.6±8.3 kJ·mol-1. 相似文献
9.
The effects of dietary deficiencies of zinc and essential fatty acids (EFAs) or both on aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were investigated in young growing rats. Four groups of albino rats were fed diets deficient in either EFA (4% hydrogenated coconut oil) or zinc (6 ppm) or both. The control diet was adequate in EFA (4% soybean oil) and zinc (100 ppm). The feeding trial lasted eight weeks and the activities of AST and ALT were determined in the liver and serum. EFA deficiency had no significant (p > 0.05) effect on liver AST. However, zinc and the double deficiencies depressed AST activity in the organ. Deficiencies of EFA, zinc and their combination depressed ALT activity in the liver significantly (p < 0.05) with a concomitant increase recorded in the serum. The data suggested alteration in endothelial permeability of the plasma membrane and thus leakage of membrane constituents in the tissue studied. It is therefore considered that these deficient diets may affect liver tissue negatively in view of the role of these enzymes in amino acid metabolism. 相似文献
10.