Quarterly Reviews of Biophysics
0033-5835
1469-8994
Anh Quốc
Cơ quản chủ quản: CAMBRIDGE UNIV PRESS , Cambridge University Press
Lĩnh vực:
Biophysics
Các bài báo tiêu biểu
The molecular theory of polyelectrolyte solutions with applications to the electrostatic properties of polynucleotides Although the importance of the polyelectrolyte character of DNA has been recognized for some time (Felsenfeld & Miles 1967), few of the implications have been explored, primarily because of a lag in translating the breakthroughs in polyelectrolyte theory of the last decade into a form that is well adapted to the analysis of the specialized problems of biophysical chemistry. Perhaps an analogous situation existed in the field of protein chemistry during the period after the formulation and confirmation of the Debye—Hückel theory of ionic solutions but before Scatchard's incorporation of the theory into his analysis of the binding properties of proteins. An achievement for polynucleotide solutions parallel to Scatchard's was recently presented by Record, Lohman, & de Haseth (1976) and further developed and reviewed by Record, Anderson & Lohman (1978).
Tập 11 Số 2 - Trang 179-246 - 1978
The Hofmeister effect and the behaviour of water at interfaces SUMMARY Starting from known properties of non-specific salt effects on the surface tension at an air–water interface, we propose the first general, detailed qualitative molecular mechanism for the origins of ion-specific (Hofmeister) effects on the surfacepotential difference at an air–water interface; this mechanism suggests a simple model for the behaviour of water at all interfaces (including water–solute interfaces), regardless of whether the non-aqueous component is neutral or charged, polar or non-polar. Specifically, water near an isolated interface is conceptually divided into three layers, each layer being 1 water-molecule thick. We propose that the solute determines the behaviour of the adjacent first interfacial water layer (I 1 ); that the bulk solution determines the behaviour of the third interfacial water layer (I 3 ), and that bothI 1 andI 3 compete for hydrogen-bonding interactions with the intervening water layer (I 2 ), which can be thought of as a transition layer. The model requires that a polar kosmotrope (polar water-structure maker) interact withI 1 more strongly than would bulk water in its place; that a chaotrope (water-structure breaker) interact withI 1 somewhat less strongly than would bulk water in its place; and that a non-polar kosmotrope (non-polar water-structure maker) interact withI 1 much less strongly than would bulk water in its place. We introduce two simple new postulates to describe the behaviour ofI 1 water molecules in aqueous solution. The first, the ‘relative competition’ postulate, states that anI 1 water molecule, in maximizing its free energy (—δG), will favour those of its highly directional polar (hydrogen-bonding) interactions with its immediate neighbours for which the maximum pairwise enthalpy of interaction (—δH ) is greatest; that is, it will favour the strongest interactions. We describe such behaviour as ‘compliant’, since anI 1 water molecule will continually adjust its position to maximize these strong interactions. Its behaviour towards its remaining immediate neighbours, with whom it interacts relatively weakly (but still favourably), we describe as ‘recalcitrant’, since it will be unable to adjust its position to maximize simultaneously these interactions. The second, the ‘charge transfer’ postulate, states that the strong polar kosmotrope–water interaction has at least a small amount of covalent character, resulting in significant transfer of charge from polar kosmotropes to water–especially of negative charge from Lewis bases (both neutral and anionic); and that the water-structuring effect of polar kosmotropes is caused not only by the tight binding (partial immobilization) of the immediately adjacent (I 1 ) water molecules, but also by an attempt to distribute among several water molecules the charge transferred from the solute. When extensive, cumulative charge transfer to solvent occurs, as with macromolecular polyphosphates, the solvation layer (the layer of solvent whose behaviour is determined by the solute) can become up to 5- or 6-water-molecules thick. We then use the ‘relative competition’ postulate, which lends itself to simple diagramming, in conjunction with the ‘charge transfer’ postulate to provide a new, startlingly simple and direct qualitative explanation for the heat of dilution of neutral polar solutes and the temperature dependence of relative viscosity of neutral polar solutes in aqueous solution. This explanation also requires the new and intriguing general conclusion that as the temperature of aqueous solutions is lowered towards o °C, solutes tend to acquire a non-uniform distribution in the solution, becoming increasingly likely to cluster 2 water molecules away from other solutes and surfaces (the driving force for this process being the conversion of transition layer water to bulk water). The implications of these conclusions for understanding the mechanism of action of general (gaseous) anaesthetics and other important interfacial phenomena are then addressed.
Tập 18 Số 4 - Trang 323-422 - 1985
Physical principles of membrane organization Membranes are the most common cellular structures in both plants and animals. They are now recognized as being involved in almost all aspects of cellular activity ranging from motility and food entrapment in simple unicellular organisms, to energy transduction, immunorecognition, nerve conduction and biosynthesis in plants and higher organisms. This functional diversity is reflected in the wide variety of lipids and particularly of proteins that compose different membranes. An understanding of the physical principles that govern the molecular organization of membranes is essential for an understanding of their physiological roles sincestructure andfunction are much more interdependent in membranes than in, say, simple chemical reactions in solution. We must recognize, however, that the word ‘understanding’ means different things in different disciplines, and nowhere is this more apparent than in this multidisciplinary area where biology, chemistry and physics meet.
Tập 13 Số 2 - Trang 121-200 - 1980
Hydrogen exchange and structural dynamics of proteins and nucleic acids Though the structures presented in crystallographic models of macromolecules appear to possess rock-like solidity, real proteins and nucleic acids are not particularly rigid. Most structural work to date has centred upon the native state of macromolecules, the most probable macromolecular form. But the native state of a molecule is merely its most abundant form, certainly not its only form. Thermodynamics requires that all other possible structural forms, however improbable, must also exist, albeit with representation corresponding to the factor exp( —G i /RT ) for each state of free energyG i (see Moelwyn-Hughes, 1961), and one appreciates that each molecule within a population of molecules will in time explore the vast ensemble ofpossible structural states.
Tập 16 Số 4 - Trang 521-655 - 1983
Deuterium magnetic resonance: theory and application to lipid membranes Proton and carbon-13 nmr spectra of unsonicated lipid bilayers and biological membranes are generally dominated by strong proton–proton and proton–carbon dipolar interactions. As a result the spectra contain a large number of overlapping resonances and are rather difficult to analyse. Nevertheless, important information on the structure and dynamic behaviour of lipid systems has been provided by these techniques (Wennerström & Lindblom, 1977).
Tập 10 Số 3 - Trang 353-418 - 1977
The NADH:ubiquinone oxidoreductase (complex I) of respiratory chains The inner membranes of mitochondria contain three multi-subunit enzyme complexes that act successively to transfer electrons from NADH to oxygen, which is reduced to water (Fig. I). The first enzyme in the electron transfer chain, NADH:ubiquinone oxidoreductase (or complex I), is the subject of this review. It removes electrons from NADH and passes them via a series of enzyme-bound redox centres (FMN and Fe-S clusters) to the electron acceptor ubiquinone. For each pair of electrons transferred from NADH to ubiquinone it is usually considered that four protons are removed from the matrix (see section 4.1 for further discussion of this point).
Tập 25 Số 3 - Trang 253-324 - 1992
Role of uncoupled and non-coupled oxidations in maintenance of safely low levels of oxygen and its one-electron reductants Abstract To proceed at a high rate, phosphorylating respiration requires ADP to be available. In the resting state, when the energy consumption is low, the ADP concentration decreases so that phosphorylating respiration ceases. This may result in an increase in the intracellular concentrations of O2 as well as of one-electron O2 reductants such as2 and the O2 reductants when phosphorylating respiration fails to do this job due to lack of ADP. In particular, it is proposed that some increase in the H+ leak of mitochondrial membrane in State 4 lowers2 consumption and decreases the level of2 reductant. In this connection, the role of natural uncouplers (thyroid hormones), recouplers (male sex hormones and progesterone), non-specific pore in the inner mitochondrial membrane, and apoptosis, as well as of non-coupled electron transfer chains in plants and bacteria will be considered.
Tập 29 Số 2 - Trang 169-202 - 1996
Membrane fusion proteins of enveloped animal viruses In a living cell membrane-bound compartments are continuously either separated or united through fusion reactions, and literally thousands of such reactions take place every minute. The formation of membrane vesicles from pre-existing membranes, and their fusion with specific acceptor membranes, constitute a prerequisite for the transport of most impermeant molecules and macromolecules into the cell by endocytosis, out of the cell by exocytosis, and between the cellular organelles (Palade, 1975; Silverstein, 1978; Evered & Collins, 1982). Less frequent, but equally crucial, are fusion events in fertilization, cell division, polykaryon formation, enucleation, etc. (for reviews see Poste & Nicholson, 1978). Although a great deal is known about the properties and consequences of individual forms of membrane fusion in cellular systems, and about fusion in artificial lipid membranes, the molecular basis for the reactions remain largely unclear.
Tập 16 Số 2 - Trang 151-195 - 1983
Mechanisms of cooperativity and allosteric regulation in proteins AUosteric proteins control and coordinate chemical events in the living cell. When Monod conceived that idea he said that he had discovered the second secret of life. The first was the structure of DNA. The theory as published by Monodet al. (1963) was concerned chiefly with cooperativity and feedback inhibition of enzymes, such as the inhibition of threonine deaminase, the first enzyme in the pathway of the synthesis of isoleucine, by isoleucine, and its activation by valine. Two years later the theory was formalized by Monodet al. (1965).
Tập 22 Số 2 - Trang 139-237 - 1989
Hydrodynamic properties of complex, rigid, biological macromolecules: theory and applications Among the Various methods for characterizing macromolecules in solution, hydrodynamic techniques play a major role. Since the advent of the ultracentrifuge and the development of viscometric apparatus, sedimentation coefficients and intrinsic viscosities have been extensively used to learn about the size and shape of synthetic and biological polymers. More recently, refined techniques such as quasielastic light scattering, transient electric birefringence and fluorescence anisotropy decay have made it possible to obtain in a simple and rapid way quantitative information of high precision on the translational and rotational brownian dynamics of dissolved macromolecules.
Tập 14 Số 1 - Trang 81-139 - 1981