Investigations of peptide hydration using NMR and molecular dynamics simulations: A study of effects of water on the conformation and dynamics of antamanide

Summary The influence of water binding on the conformational dynamics of the cyclic decapeptide antamanide dissolved in the model lipophilic environment chloroform is investigated by NMR relaxation measurements. The water-peptide complex has a lifetime of 35 s at 250 K, which is longer than typical lifetimes of water-peptide complexes reported in aqueous solution. In addition, there is a rapid intracomplex mobility that probably involves librational motions of the bound water or water molecules hopping between different binding sites. Water binding restricts the flexibility of antamanide. The experimental findings are compared with GROMOS molecular dynamics simulations of antamanide with up to eight bound water molecules. Within the simulation time of 600 ps, no water molecule leaves the complex. Additionally, the simulations show a reduced flexibility for the complex in comparison with uncomplexed antamanide. Thus, there is a qualitative agreement between the experimental NMR results and the computer simulations.     

DNA immunization: Effects of vehicle and route of administration on the induction of protective antiviral immunity

Abstract The effectiveness of DNA immunization has been demonstrated in several model systems, usually following intramuscular injection of DNA in saline, or topical administration to the skin. In this study we have compared DNA delivered by three routes (intramuscular, intravenous, and intraperitoneal) and, for each route, in two vehicles (cationic liposome complex and pH sensitive liposome). These two lipid vehicles were evaluated because they are frequently used in gene therapy studies, but their immunogenicity has not been extensively studied. Each of these six combinations has been evaluated not only by assay of marker gene expression in a variety of tissues, but also by measurement of biologically-relevant parameters of immunity induction of antibodies, cytotoxic T lymphocytes, and protection against viral challenge. By both criteria (marker gene expression and induced immunity), the outcomes vary markedly among the six combinations. The combination leading to maximal marker gene expression (DNA with cationic lipid, administered i.v.) also induces detectable antibodies and CTL, and is the only one of the six combinations to induce immune responses comparable to those seen following i.m. injection of DNA in saline. However, marker gene expression can be detected in other combinations in the absence of induced immunity thus the value of marker gene expression in predicting the protection induced by a microbial antigen is questionable suggesting that, when evaluating various promoter constructs, marker gene expression may not adequately replace the direct measurement of biological outcomes.     

New polymorphic markers in the vicinity of the pearl locus on mouse Chromosome 13

We have used a Mus domesticus/-Mus spretus congenic animal that was selected for retention of Mus spretus DNA around the pearl locus to create a highly polymorphic region suitable for screening new markers. Representation difference analysis (RDA) was performed with either DNA from the congenic animal or C57BL/6J as the driver for subtraction. Four clones were identified, characterized, and converted to PCR-based polymorphic markers. Three of the four markers equally subdivide a 10-cM interval containing the pearl locus, with the fourth located centromeric to it. These markers have been placed on the mouse genetic map by use of an interspecific backcross panel between Mus domesticus (C57BL/6J) and Mus spretus generated by The Jackson Laboratory. Received: 12 June 1995 / Accepted: 17 August 1995     

Chloride secretion in the submandibular gland of adult and early postnatal rats studied by X-ray microanalysis

Submandibular acinar cells of 1-day-old, 7-day-old, and adult rats were analyzed with X-ray microanalysis after stimulation with carbachol for different time periods (2–7 min). In unstimulated animals, marked differences in elemental content between compartments could be observed: secretory granules had a higher Ca and lower P and K content than other cell compartments. Comparison between different age groups showed significant differences for Ca, which increased with age in all compartments; Mg increased with age in the secretory granules and the apical cytoplasm. Only the glands from adult animals showed a significant effect of cholinergic stimulation: a transient decrease in Cl and K. The Cl concentration in the secretory granules decreased to 60% of the control value, which suggests that the granules release Cl upon stimulation. In young animals, no or little change in elemental distribution was observed after stimulation. This may indicate that Cl-secretion mechanisms are much less prominent in young animals. The ultrastructure of submandibular secretory granules depends on the preparation method: condensed and electrondense in freeze-substituted unfixed tissue, decondensed and more translucent in aldehyde-fixed tissue. This may indicate that the granules can transport water, and swell during the process of aldehyde fixation.     

DNA水平上的植物系统学研究方法

本文简要总结了近年来在ＤＮＡ水平上的植物系统学研究方法,着重介绍了限制性长度多态性分析,ＰＣＲ技术在植物系统学上的应用等这一领域最新的进展,并对分子数据的分析方法及系统树的构建进行了详细讨论。     

三个矮杆小麦的矮生性遗传研究

通过与事国春杂交,利用杂交后代Ｆ２和回交后代ＢＣ１Ｐ１及ＢＣ２Ｐ２,研究了三个小麦新矮杆品系和矮生性遗传特性。结果表明,０００４的矮生性受一对部分显性矮杆基因控制,５７４６和７５３９－各受两对部分显性矮杆基因控制。     

桂平市竹笋资源及其开发利用

桂平市食用竹笋资源丰富,有大头竹笋、吊丝竹笋、浦竹笋、毛竹笋等十余种,年产鲜笋８５００ｔ以上。原有的加工方法比较落后,现已注意引进新技术,今后还需进一步开发利用。     

环化二磷酸腺苷核糖及其钙动员的功能

环化二磷酸腺苷核糖（cyclic ADP-ribose,cADPR）是烟酰胺腺嘌呤二核苷酸(NAD⁺)的代谢产物,是新近发现的一种细胞内第二信使．在许多哺乳类和无脊椎动物细胞中,cADPR能引起胞内钙库释放钙离子,其可能机制是：cADPR受体结合cADPR,通过Ryanodine受体或类Ryanodine受体介导的钙通道使cADPR敏感的钙库释放钙离子,此外,一条由一氧化氮（NO）、环化鸟苷酸（cGMP）和cADPR组成的细胞内信号转导途径可能存在于许多细胞中．