Chemical properties of alcohols and their protein binding sites

Alcohols affect a wide array of biological processes including protein folding, neurotransmission and immune responses. It is becoming clear that many of these effects are mediated by direct binding to proteins such as neurotransmitter receptors and signaling molecules. This review summarizes the unique chemical properties of alcohols which contribute to their biological effects. It is concluded that alcohols act mainly as hydrogen bond donors whose binding to the polypeptide chain is stabilized by hydrophobic interactions. The electronegativity of the O atom may also play a role in stabilizing contacts with the protein. Properties of alcohol binding sites have been derived from X-ray crystal structures of alcohol-protein complexes and from mutagenesis studies of ion channels and enzymes that bind alcohols. Common amino acid sequences and structural features are shared among the protein segments that are involved in alcohol binding. The alcohol binding site is thought to consist of a hydrogen bond acceptor in a turn or loop region that is often situated at the N-terminal end of an alpha-helix. The methylene chain of the alcohol molecule appears to be accommodated by a hydrophobic groove formed by two or more structural elements, frequently a turn and an alpha-helix. Binding at these sites may alter the local protein structure or displace bound solvent molecules and perturb the function of key proteins.     

The perspectives of studying multi-domain protein folding

Most of fundamental studies on protein folding have been performed with small globular proteins consisting of a single domain. In vitro many of these proteins are well characterized by a reversible two-state folding scheme. However, the majority of proteins in the cell belong to the class of larger multi-domain proteins that often unfold irreversibly under in vitro conditions. This makes folding studies difficult or even impossible. In spite of these problems for many multi-domain proteins, folding has been investigated by classical refolding. Co-translational folding of nascent polypeptide chains when synthesized by ribosomes has also been studied. Single molecule techniques represent a promising approach for future studies on the folding of multi-domain proteins, and tremendous advances have been made in these techniques in recent years. In particular, fluorescence-based methods can contribute significantly to an understanding of the fundamental principles of multi-domain protein folding. Received 3 December 2008; accepted 23 December 2008     

简评储氢与制氢研究中的问题与进展

储氢与再生氢的制备是到达氢经济时代必须解决的2个关键技术问题。通过阐述超临界温度下气体的吸附机理,指出基于吸附原理的储氢材料不可能具有工业应用前景,其它已知的储氢方法亦然,因此储氢研究必须从原理方面探索具有工业应用前景的储氢方法。虽然大多数制氢研究仍以化石燃料为制氢原料,但只有从水制得的氢才是再生氢,才具有可持续性、洁净性和能源安全性。简评了再生氢制备方法,并报告一种通过不同价态的铁氧化物之间的转换实现水不完全分解制取纯氢的实验室研究结果。     

Effects of Si and Ce on the microstructure and hydrogen storage property of Ti_(26.5)Cr_(20)V_(45)Fe_(8.5)Ce_(0.5) alloy

In this paper,the effects of Si and Ce on the microstructure and hydrogen storage property of Ti26.5 Cr20V45Fe8.5Ce0.5 alloy were studied,respectively.First of all,effects of Si on the microstructure and hydrogen storage properties of Ti26.5Cr20(V45Fe8.5)1-xSixCe0.5(x=0,0.5,1.0,1.5 and 2.0 at%)alloys were studied by X-ray diffraction,scanning electron microscopy and P-C isotherm measurements.As the Si addition increases,the hydrogen absorption capacities of alloys decrease but the equilibrium pressure incre...     

The glutathione peroxidases

There are several proteins in mammalian cells that can metabolize hydrogen peroxide and lipid hydroperoxides. These proteins include four selenium-containing glutathione peroxidases that are found in different cell fractions and tissues of the body. This review considers the structure and distribution of the selenoperoxidases and how this relates to their biological function. The functions of the selenoperoxidases were originally studied in systems where their activity was manipulated by changing dietary selenium levels. More recently, molecular techniques have allowed overexpression of selenoperoxidases in cell lines and animals. Additionally, cellular glutathione peroxidase knockout mice have been used to investigate the functions of this protein. From this work it is clear that the selenoperoxidases are involved in cell antioxidant systems. However, they also have more subtle functions in ensuring the regulation and formation of arachadonic acid metabolites that are derived from hydroperoxide intermediates. The range of biological processes, which are potentially dependent on optimal selenoperoxidase activity in mammals, emphasises the importance of achieving adequate selenium intake in the diet.     

Compatible solutes of halophilic eubacteria: molecular principles,water-solute interaction,stress protection

Compatible solutes are best described as organic osmolytes responsible for osmotic balance and at the same time compatible with the cells' metabolism. A comprehensive survey (using HPLC and NMR methods) on halophilic/halotolerant eubacteria has revealed the full diversity of compatible solutes employed in nature. Molecular principles derived from the spectrum of compounds found in the bacterial world may be summarized as follows. Compatible solutes are polar, highly soluble molecules and uncharged at physiological pH. With the exception of proline (a proteinogenic amino acid) they are characterized as amino acid derivatives of the following types: betaines, ectoines, N-acetylated diamino acids and N-derivatized carboxamides of glutamine. Using nearinfrared spectroscopy we have also been able to demonstrate that compatible solutes are strong water-structure formers and as such probably excluded from the hydration shell of proteins. This preferential exclusion probably explains their function as effective stabilizers of the hydration shell of native proteins (protection against heating freezing and drying). Hence these typical products of halophilic eubacteria have a considerable potential as stabilizing/protecting agents on both molecular and whole-cell level. Thorough understanding of common structural principles and fundamental water-solute interactions will ultimately enable us to design novel highly efficient stress protectants and stabilizers of biomolecules.     

The dynamic nature of the bacterial cytoskeleton

Three of the four well-established bacterial cytoskeletal systems—the MreB, MinCDE, and FtsZ systems—undergo a variety of short-range and long-range dynamic behaviors. These include the cellular reorganization of the cytoskeletal elements, in which the proteins redistribute from a predominantly helical pole-to-pole pattern into annular structures near midcell. Despite their apparent similarity, these dramatic redistributional events in the three systems are in large part independent of each other. In addition, some of the cytoskeletal structures undergo oscillatory behavior in which the helical elements move repetitively back-and-forth between the two ends of the cell. The details and mechanisms underlying these dynamic cellular events are just now being revealed by fluorescence microscopy of intact cells, fluorescence photobleaching recovery studies, single molecule tracking techniques, and in vitro studies of the purified proteins.     

Structure, function and evolution of antifreeze proteins

Antifreeze proteins bind to ice crystals and modify their growth. These proteins show great diversity in structure, and they have been found in a variety of organisms. The ice-binding mechanisms of antifreeze proteins are not completely understood. Recent findings on the evolution of antifreeze proteins and on their structures and mechanisms of action have provided new understanding of these proteins in different contexts. The purpose of this review is to present the developments in contrasting research areas and unite them in order to gain further insight into the structure and function of the antifreeze proteins. Received 2 September 1998; received after revision 21 October 1998; accepted 2 November 1998     

The muscle ultrastructure: a structural perspective of the sarcomere

Muscle ultrastructure is characterised by a complex arrangement of many protein-protein interactions. The sarcomere is the basic repeating unit of muscle, formed by two transverse filament systems: the thick and thin filaments. While actin and myosin are the main contractile elements of the sarcomere, other proteins act as scaffolds, control ultrastructure composition, regulate muscle contraction, and transmit tension between sarcomeres and hence to the whole myofibril. Elucidation of the structures of muscle proteins by X-ray crystallography and nuclear magnetic resonance spectroscopy has been essential in understanding muscle contraction, enabling us to relate biological to structural information. These structures reveal how components of the muscle interact, how different factors influence conformational changes within these proteins, and how mutant muscle proteins may interfere with the regulatory fine-tuning of the contractile machinery, hence leading to disease in some cases. Here, structures solved within the sarcomere have been reviewed in order to put the numerous components into context.Received 28 June 2004; received after revision 25 July 2004; accepted 28 July 2004     

Systematic study of the variations in mineral composition of different bones from various animals according to their localization]

X-ray diffraction techniques allow us to show that, in calcified tissues, phosphates resulting from a given formation process have the same ratio Ca/P for the bones at different subjects, providing these subjects are of the same kind and the same age. This ratio Ca/P depends on the bone formation process.     

硼氢化钠作为能量载体的新型能量转换技术(英文)

硼氢化钠作为能量载体的新型能量转换技术,它由直接硼氢化钠燃料电池、硼氯化钠水解制氢和硼氢化钠再生技术构成。通过总结了近年来在直接硼氢化钠燃料电池、硼氢化钠水解制氢和硼氢化钠再生技术上的进展,发现硼氢化钠作为能量载体的新型能量转换技术的雏形已日渐形成,本文总结和讨论了该项技术的优点和面临的挑战。     

Marked by association: techniques for proximity-dependent labeling of proteins in eukaryotic cells

Various methods have been established for the purpose of identifying and characterizing protein–protein interactions (PPIs). This diverse toolbox provides researchers with options to overcome challenges specific to the nature of the proteins under investigation. Among these techniques is a category based on proximity-dependent labeling of proteins in living cells. These can be further partitioned into either hypothesis-based or unbiased screening methods, each with its own advantages and limitations. Approaches in which proteins of interest are fused to either modifying enzymes or receptor sequences allow for hypothesis-based testing of protein proximity. Protein crosslinking and BioID (proximity-dependent biotin identification) permit unbiased screening of protein proximity for a protein of interest. Here, we evaluate these approaches and their applications in living eukaryotic cells.     

Methods of probing the interactions between small molecules and disordered proteins

It is generally recognized that a large fraction of the human proteome is made up of proteins that remain disordered in their native states. Despite the fact that such proteins play key biological roles and are involved in many major human diseases, they still represent challenging targets for drug discovery. A major bottleneck for the identification of compounds capable of interacting with these proteins and modulating their disease-promoting behaviour is the development of effective techniques to probe such interactions. The difficulties in carrying out binding measurements have resulted in a poor understanding of the mechanisms underlying these interactions. In order to facilitate further methodological advances, here we review the most commonly used techniques to probe three types of interactions involving small molecules: (1) those that disrupt functional interactions between disordered proteins; (2) those that inhibit the aberrant aggregation of disordered proteins, and (3) those that lead to binding disordered proteins in their monomeric states. In discussing these techniques, we also point out directions for future developments.     

Common structural traits for cystine knot domain of the TGFβ superfamily of proteins and three-fingered ectodomain of their cellular receptors

The transforming growth factor-β (TGFβ) superfamily of proteins and their receptors are crucial developmental factors for all metazoan organisms. Cystine-knot (CK) motif is a spatial feature of the TGFβ superfamily of proteins whereas the extra-cellular domains (ectodomains) of their respective receptors form three-fingered protein domain (TFPD), both stabilized by tight cystine networks. Analyses of multiple sequence alignments of these two domains encoded in various genomes revealed that the cystines forming the CK and TFPD folds are conserved, whereas the remaining polypeptide patches are diversified. Orthologues of the human TGFβs and their respective receptors expressed in diverse vertebrates retain high sequence conservation. Examination of 3D structures of various TGFβ factors bound to their receptors have revealed that the CK and TFPD domains display several similar spatial traits suggesting that these two different protein folds might have been acquired from a common ancestor.     

Röntgenstrahlen und Aufbau der Materie

Summary X-rays have proved exceptionally useful in the investigation of the structure of matter, especially since the discovery of X-ray diffraction in crystals. A survey is given of the development of research into crystal structures and stress is laid on the value of the international co-operation achieved in this field. The use of X-ray diffraction, at first restricted to the determination of crystal structures, has in the course of time been extended far beyond the limits of crystallography. Today diffraction methods offer a widely applicable means of scientific research and one particularly adapted to the technical testing of materials. Further important applications of X-rays in science and technology are provided by radiography and X-ray spectroscopy.