排序方式: 共有68条查询结果,搜索用时 122 毫秒
41.
Yamuna Devi Paila 《生物化学与生物物理学报:生物膜》2009,1788(2):295-19
The G-protein coupled receptors (GPCRs) are the largest class of molecules involved in signal transduction across membranes, and represent major drug targets in all clinical areas. Membrane cholesterol has been reported to have a modulatory role in the function of a number of GPCRs. Interestingly, recently reported crystal structures of GPCRs have shown structural evidence of cholesterol binding sites. Two possible mechanisms have been previously suggested by which membrane cholesterol could influence the structure and function of GPCRs (i) through a direct/specific interaction with GPCRs, which could induce a conformational change in the receptor, or (ii) through an indirect way by altering the membrane physical properties in which the receptor is embedded or due to a combination of both. We discuss here a novel mechanism by which membrane cholesterol could affect structure and function of GPCRs and propose that cholesterol binding sites in GPCRs could represent ‘nonannular’ binding sites. Interestingly, previous work from our laboratory has demonstrated that membrane cholesterol is required for the function of the serotonin1A receptor, which could be due to specific interaction of the receptor with cholesterol. Based on these results, we envisage that there could be specific/nonannular cholesterol binding site(s) in the serotonin1A receptor. We have analyzed putative cholesterol binding sites from protein databases in the serotonin1A receptor, a representative GPCR, for which we have previously demonstrated specific requirement of membrane cholesterol for receptor function. Our analysis shows that cholesterol binding sites are inherent characteristic features of serotonin1A receptors and are conserved over evolution. Progress in deciphering molecular details of the nature of GPCR-cholesterol interaction in the membrane would lead to better insight into our overall understanding of GPCR function in health and disease, thereby enhancing our ability to design better therapeutic strategies to combat diseases related to malfunctioning of GPCRs. 相似文献
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Saikat Chakraborty Suruchi Sharma Prabal K. Maiti Yamuna Krishnan 《Nucleic acids research》2009,37(9):2810-2817
We report a pH-dependent conformational transition in short, defined homopolymeric deoxyadenosines (dA15) from a single helical structure with stacked nucleobases at neutral pH to a double-helical, parallel-stranded duplex held together by AH+-H+A base pairs at acidic pH. Using native PAGE, 2D NMR, circular dichroism (CD) and fluorescence spectroscopy, we have characterized the two different pH dependent forms of dA15. The pH-triggered transition between the two defined helical forms of dA15 is characterized by CD and fluorescence. The kinetics of this conformational switch is found to occur on a millisecond time scale. This robust, highly reversible, pH-induced transition between the two well-defined structured states of dA15 represents a new molecular building block for the construction of quick-response, pH-switchable architectures in structural DNA nanotechnology. 相似文献
43.
Yamuna Kunhi Mouvenchery Ji?í Ku?erík Doerte Diehl Gabriele E. Schaumann 《Reviews in Environmental Science and Biotechnology》2012,11(1):41-54
Interactions between cations and natural organic matter (NOM) are central for the stability of organic matter, formation of
supramolecular NOM structure, formation of organo-mineral associations, soil aggregation and binding of organic contaminants.
The effect of multivalent cations on environmental functionalities of NOM strongly depends on the relative importance between
intramolecular complexation and intermolecular cross-linking, the degree of which will be determined by the spatial arrangement
of the hydrophilic functional groups in NOM. This literature review seeks to evaluate the current state of the art regarding
the relevance of intermolecular cross-links via bridges of multivalent cations. Cross-linking has been suggested to explain
among others aggregate stability, retarded dissolved organic matter release, reduced organic matter (OM) solubility as well
as increase in degree and nonlinearity of sorption or organic chemicals to NOM. Although the cross-linking mechanism has been
suggested in numerous studies, it has not yet been verified directly. The dynamics of the intermolecular cross-links, their
persistence as well as their interplay with OM and their influence on stability and bioavailability of organic chemicals is
up to now unknown. The major challenge in this context is the development of a suitable combination of experimental and instrumental
techniques and relating the results to molecular and physicochemical models on the basis of targeted combination of spectroscopic,
molecular modelling and thermoanalytical methods. 相似文献
44.
Nipon Sarmah D. Revathi G. Sheelu K. Yamuna Rani S. Sridhar V. Mehtab C. Sumana 《Biotechnology progress》2018,34(1):5-28
Lipases are the industrially important biocatalysts, which are envisioned to have tremendous applications in the manufacture of a wide range of products. Their unique properties such as better stability, selectivity and substrate specificity position them as the most expansively used industrial enzymes. The research on production and applications of lipases is ever growing and there exists a need to have a latest review on the research findings of lipases. The present review aims at giving the latest and broadest overall picture of research and development on lipases by including the current studies and progressions not only in the diverse industrial application fields of lipases, but also with regard to its structure, classification and sources. Also, a special emphasis has been made on the aspects such as process optimization, modeling, and design that are very critical for further scale‐up and industrial implementation. The detailed tabulations provided in each section, which are prepared by the exhaustive review of current literature covering the various aspects of lipase including its production and applications along with example case studies, will serve as the comprehensive source of current advancements in lipase research. This review will be very useful for the researchers from both industry as well as academia in promoting lipolysis as the most promising approaches to intensified, greener and sustainable processes. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 34:5–28, 2018 相似文献
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The biosynthesis and metabolism of cholesterol in the brain is spatiotemporally and developmentally regulated. Brain cholesterol plays an important role in maintaining the function of neuronal receptors, which are key components in neural signal transduction. This is illustrated by the requirement of membrane cholesterol for the function of the serotonin(1A) receptor, a transmembrane neurotransmitter receptor. A crucial determinant for the function of neuronal receptors could be the availability of brain cholesterol. The Smith-Lemli-Optiz Syndrome, a metabolic disorder characterized by severe neurodegeneration leading to mental retardation, represents a condition in which the availability of brain cholesterol is limited. A comprehensive molecular analysis of lipid-protein interactions in healthy and diseased states could be crucial for a better understanding of the pathogenesis of psychiatric disorders. 相似文献
47.
下游工艺开拓中如何系统地筛选离子交换层析介质 总被引:1,自引:0,他引:1
下游层析工艺开拓中,选择层析介质最重要的因素包括纯度、动力载量和凝胶的使用寿命。本文作者示范了介质的动力载量及其回收率的重要区别。 相似文献
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Yamuna Kunhi Mouvenchery Alexander Jaeger Adelia J. A. Aquino Daniel Tunega D?rte Diehl Marko Bertmer Gabriele Ellen Schaumann 《PloS one》2013,8(6)
It is assumed to be common knowledge that multivalent cations cross-link soil organic matter (SOM) molecules via cation bridges (CaB). The concept has not been explicitly demonstrated in solid SOM by targeted experiments, yet. Therefore, the requirements for and characteristics of CaB remain unidentified. In this study, a combined experimental and molecular modeling approach was adopted to investigate the interaction of cations on a peat OM from physicochemical perspective. Before treatment with salt solutions of Al3+, Ca2+ or Na+, respectively, the original exchangeable cations were removed using cation exchange resin. Cation treatment was conducted at two different values of pH prior to adjusting pH to 4.1. Cation sorption is slower (>>2 h) than deprotonation of functional groups (<2 h) and was described by a Langmuir model. The maximum uptake increased with pH of cation addition and decreased with increasing cation valency. Sorption coefficients were similar for all cations and at both pH. This contradicts the general expectations for electrostatic interactions, suggesting that not only the interaction chemistry but also spatial distribution of functional groups in OM determines binding of cations in this peat. The reaction of contact angle, matrix rigidity due to water molecule bridges (WaMB) and molecular mobility of water (NMR analysis) suggested that cross-linking via CaB has low relevance in this peat. This unexpected finding is probably due to the low cation exchange capacity, resulting in low abundance of charged functionalities. Molecular modeling demonstrates that large average distances between functionalities (∼3 nm in this peat) cannot be bridged by CaB-WaMB associations. However, aging strongly increased matrix rigidity, suggesting successive increase of WaMB size to connect functionalities and thus increasing degree of cross-linking by CaB-WaMB associations. Results thus demonstrated that the physicochemical structure of OM is decisive for CaB and aging-induced structural reorganisation can enhance cross-link formation. 相似文献
50.
Summary A diffusible self-inhibitor of germination of conidia of Glomerella cingulata appears to act as a regulator of protein synthesis. Both uptake of labeled amino acids and their incorporation into protein are reduced by the inhibitor or by crowding. Compared to conidia incubated without self-inhibitor, conidia incubated with self-inhibitor incorporated no labeled amino acids into protein in the first hour and 80% less in 6h. Thoroughly washed conidia were more permeable to amino acids and incorporated 6 times more precursor into proteins than unwashed conidia. At high density in nutrient medium, conidia of G. cingulata preferentially form secondary conidia instead of germ tubes and a mycelium. This inhibition of germination of conidia and regulation of development is mimicked by exposing them to an auto-inhibitor extracted from used culture medium and conidial washings. Germination of conidia of G. cingulata involves two steps, an initial step of 5 h duration which continues unaffected by crowing (1.7×108/ml) and a subsequent 2 h step which conidia do not take unless they are sufficiently diluted. It is this step for which protein synthesis may be required.Non-Standard Abbreviations CHM
cyloheximide
- NM
Neurospora minimal medium
- psi
pound per square inch
- RPH
reconstituted algal protein hydrolysate
- TCA
trichloroacetic acid 相似文献