bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetic-moment field generation in the reflection region in a cold magnetized plasma
Authors: Das Chandra , Bera B. , Chakraborty B. , Khan Manoranjan
Published: March 2009

Magnetization due to a magnetic moment contributes to the non-oscillating magnetic field in a plasma. The dynamics ofclassically bound electrons in the presence of an applied circularly polarized strong electromagnetic field in the reflection region generates this field. The special case of its resonant generation when the frequency of a right circularlypolarized wave is equal to the ion gyration frequency is studied here. Another source of non-oscillating magnetization isthe interaction of electromagnetic fields, including fields in the Alfvén-wave frequency range, with a cold collisionless fully ionized magnetized plasma also in the reflection region. The induced field from a left circularly polarized field at Alfvén-wave frequencies is paramagnetic, inversely proportional to the square of the ambient field and independent of the mass per particle of both electrons and ions. The induced field from a right circularly polarized field at Alfvén-wave frequencies is diamagnetic, inversely proportional to the cube of the ambient field and depends directly on the plasma mass density.
Scintillations in a magnetized plasma. Part 2. The fourth-order moment
Authors: Melrose D. B.
Published: March 2009

The theory of strong scintillations in a weakly anisotropic plasma is used to derive an equation satisfied by the correlation functions for the Stokes parameters. The coefficients that describe these correlation functions are determined explicitly in terms of a matrix generalization of the standard phasestructure function. In discussing implications of the theory, emphasis is placed on terms that have no counterpart in an isotropic plasma. It is shown that the decay of the linear polarizaiton that results from differential Faraday rotation is different in the mean squares and the square means of the Stokes parameters. In principle, this allows one to determine properties relating to the fluctuations of the magnetic field along the ray path. A formal treatment of polarization dependent intensity fluctuations in a magnetized plasma is presented and discussed briefly.
Nonlinear plasma waves with steady-state d.c. current
Authors: Rauf S. , Tataronis J. A.
Published: March 2009

Using a low-frequency, low-β model of a magnetized plasma, several nonlinear waves are studied. All the waves share the property that they have a self- consistent time-averaged current in the steady state. The first wave is a one- dimensional solitary wave that propagates obliquely to a static magnetic field. The wave magnetic field has a kink structure, which results in the production of the time-averaged current. A two-dimensional wave that propagates parallel to the background magnetic field is also discussed. This is a forced wave, requiring an antenna structure to support it in the steady state. The characteristics of the two-dimensional wave are dependent upon the wave speed, which in turn is determined by the speed of the travelling wave on the external antenna.
Electromagnetism of isotropic relativistic plasmas: Maxwell's formalism and the choice of gauge
Authors: de Gottal P. , Gariel J.
Published: March 2009

We define a new generalized symmetrical permittivity tensor of rank two, χαβ in order to characterize the inductions in Maxwell's formalism for an isotropic relativistic plasma. We then show that only the Lorentz gauge allows one to write the field potentials with a propagator inversely proportional to this tensor. In this sense, we may say that the Lorentz gauge is the only one suitable for Maxwell's formalism.
A National Custom: Debating Female Servitude in Late Nineteenth-Century Hong Kong
Authors: CARROLL JOHN M.
Published: March 2009

This article frames the debate about mui-tsai (meizai, female bondservants) in late nineteenth-century Hong Kong within changing conceptions of the colony's political, geographical and cultural position. Whereas some colonial officials saw the mui-tsai system as a national shame that challenged Britain's commitment to ending slavery, others argued that it was an archaic custom that would eventually dissolve as China modernized. The debate also showed the rise of a class of Chinese elites who had accumulated enough power to defend the mui-tsai system as a time-honoured Chinese custom, even while acknowledging that in Hong Kong they lived beyond the boundaries of Chinese sovereignty. Challenging notions of the reach of the colonial state and showing how colonial policies often had unintended consequences, this debate also reveals the analytical and explanatory weakness of concepts such as ‘colonial discourse’ or ‘the colonial mind’.
China in the Japanese Radical Gaze, 1945–1955
Authors: GAYLE CURTIS ANDERSON
Published: March 2009

Japanese images of China have much to tell us about the way Japan sees its own modernisation and its place in the international system. Contrary to popular belief, Japan did not turn unabashedly toward the USA after 1945. During the first decade after World War II, a number of important Japanese radical historians and thinkers decided that modernisation could be accomplished without the help of the West. Just when many in Japan were looking to America and Europe as exemplars of modernisation, others looked instead to revolutionary China and its past struggles against Japanese colonialism in the construction of a very different historical position from that ordinarily associated with the early post-war years. Certain Japanese historians, inspired by the push toward decolonisation in Asia, set about writing the history of the present in ways that aligned Japan with modern Chinese history. Even though China had just been liberated from Japanese colonial rule, Japanese Marxists saw their own position—under American imperialism—as historically and politically congruous with China's past war of resistance against Japan (1937–45). Through campaigns to develop a kind of cultural Marxism on the margins of Japanese society, they sought to bring about post-war Japanese ‘national liberation’ from American hegemony in ways that consciously simulated past Chinese resistance to Imperial Japan. Replacing Japan's own cultural Marxist traditions from the pre-war era with the more palpable and acceptable example of China, they also hoped a new form of Asian internationalism could remedy the problem of Japan's wartime past. The historical irony associated with this discursive twist deferred to future generations the problem of how the Left* would come to terms with the past.
RNA structure
Authors: Kallenbach Neville R. , Berman Helen M.
Published: March 2009

This review is concerned primarily with the physical structure and changes in the structure of RNA molecules. It will be evident that we have not attempted comprehensive coverage of what amounts to a vast literature. We have tried to stay away from particular areas that have been recently reviewed elsewhere. Citations to and information from them are included, however, so that access to the literature is available. Much of what we treat in depth deals with the crystal structures and solution behaviour of model RNA compounds, including synthetic polymers and molecular fragments such as dinucleoside phosphates. Sequence data on natural RNA are cited, but not in detail. Similarly, apart from tRNA, natural RNAs the structural determinations of which are presently not so far advanced, are not dwelt upon. We have tried to present in detail the available structural data with scaled drawings that permit facile comparisons of molecular geometries.
Intracellular studies on transmitter effects on neurones in isolated brain slices
Authors: Andersen P. , Langmoen I. A.
Published: March 2009

In the study of transmitter mechanisms in the peripheral nervous system and the spinal cord, intracellular recording has been a great advantage. In contrast, studies on central synapses have often used more indirect techniques, often extracellular recording from a cell or a small group of cells. In particular, a large amount of information has been acquired by iontophoretic application of drugs, often with a multibarrel electrode system where the iontophoretic electrodes are coupled to a recording electrode. Because of the difficulties with proper intracellular recording from intact brain preparations, there are relatively few intracellular studies on central transmitter effects. This situation compares unfavourably with the many studies on spinal cord, and, in particular, on peripheral nervous tissue.
Ligand–receptor interactions: facts and fantasies
Authors: Klotz Irving M.
Published: March 2009

Except when radiation participates, all biological activities involve contact interactions between constituent reactants. At the molecular level, if one of the participants is smaller than its complementary partner, the former is usually designated the ‘ligand’ and the latter the ‘receptor’. Thus in an enzyme–substrate complex, the substrate is the ligand, the enzyme is the receptor. In immunological interactions, the ligand is the hapten or antigen, the receptor is the immunoglobulin. Neurotransmitters or hormones are effector ligands when they are bound to receptor sites at synapses or on cell membranes.
Reactions of electron-transfer proteins at electrodes
Authors: Armstrong Fraser A. , Hill H. Allen O. , Walton Nicholas J.
Published: March 2009

Studies of electron-transfer reactions of redox proteins have, in recent years, attracted widespread interest and attention. Progress has been evident from both physical and biological standpoints, with the increasing availability of three-dimensional structural data for many small electron-transfer proteins prompting a variety of systematic investigations (Isied, 1985). Most recently, attention has been directed towards questions concerning the elementary transfer of electrons between spatially remote redox sites, and the nature of protein–protein interactions which, for intermolecular processes, stabilize specific precursor complexes which may be optimally juxtaposed for electron-transfer. These and other issues, including the necessary reversibility of protein interfacial interactions and the dynamic properties of proteins as carriers of electrons in biological electron-transport systems, are now being addressed in the rapidly emerging field of direct (unmediated) protein electrochemistry. It is our intention in this article to discuss developments made in this area and highlight points which we believe to have the most bearing on our current understanding of diffusion-dominated, protein-mediated electron transport at electrode surfaces. First we shall outline some basic considerations which are best considered with reference to homogeneous systems.
Recent X-ray diffraction studies of muscle
Authors: Hanson Jean
Published: March 2009

An intact living muscle has such a regular structure that it diffracts light or X-rays, thereby providing patterns that contain uniquely valuable information. Interpretation of these patterns is not straightforward, but is helped by light microscopy and electron microscopy, which can often provide similar though less reliable information. At all levels of complexity, from that of the fibrils to that of the molecules, structure in a muscle is orderly. No other natural cell assembly is so suited to study by the diffraction method, and the results obtained in recent years are an outstanding example of how this method can elucidate a biological problem. In contrast to protein crystallography, where the system studied is artificial, muscle can be examined in its natural state, during normal activity. The levels of structure explored as yet in muscle are above that of the atoms in the molecules. Such structure is more commonly investigated by electron microscopy, and the application of the diffraction method to living muscle has provided a valuable check on the preparative artifacts that worry the microscopist. The great complexity of a muscle, as compared with a protein crystal, and the fact that the system is only semi-crystalline, giving a much less detailed diffraction pattern, make the problems of interpretation especially difficult. But a great deal of useful information is available about other properties of muscle and its constituents, and the flourishing state of muscle biology at present is a major factor contributing to the successful application of the diffraction method.
Factors influencing the polymerization of outer fibre microtubule protein
Authors: Stephens R. E.
Published: March 2009

Microtubule proteins have recently been prepared and characterized from a number of diverse sources. Renaud, Rowe & Gibbons (1966, 1968) have obtained a protein from acetone powders ofTetrahymena pyriformiscilia and from isolated outer fibre doublets of this same species. The protein has an actin-like amino acid composition, a minimum subunit weight of 55000, and 7·5 free sulphydryl groups per mole of monomer. Stephens (1968a) has fractionated sea-urchin flagella, following the procedure of Gibbons (1965), to obtain the isolated outer fibres and has found the protein to have properties virtually identical to those of its ciliary counterpart. Both the flagellar and the ciliary outer-fibre proteins contain 1 mole of bound guanine nucleotide per mole of protein subunit (Stephens, Renaud & Gibbons, 1967).
The Biochemical Basis of Long-Term Memory
Authors: Roberts Richard B. , Flexner Louis B.
Published: March 2009

Learning and memory are important elements of our daily lives, familiar to all through introspection. Yet the mechanisms underlying these processes are still for the most part unknown. Here are problems which combine a maximum of intrinsic and practical interest with a minimum of actual knowledge and understanding. Years of our lives are dedicated to the formation of certain long-term memories and behaviour patterns, yet we have only rudimentary notions of how such ‘schooling’ is best accomplished. There is no certainty in any aspect of the process. We are not sure whether relatively few cells or millions participate in a memory trace; whether these cells change as a whole, or whether the changes are limited to synaptic regions. In fact, we cannot be certain whether the changes are confined to the neurones or whether the glia also participate.
The neglected interface: the biology of water as a liquid-gas system
Authors: Schmidt-Nielsen Knut
Published: March 2009

Water, solutes and membranes have long been the subject of intensive research, and many excellent reviews have brought the major biological problems in focus, have discussed accomplishments, and have outlined unsolved problems. The most interesting results pertain to the role of membranes, whether ‘active’ or ‘passive’, which separate different solutions, in other words, membranes at a water–water inerface Liquid gas interfaces have receied less attention, and I therefore wish to review some biological problem which relate to such systems. I shall discuss a variety of phenomena which may have little in common, except that they all bear onthe transition of water between liquid and gas.
Molecular characteristics of biogenic monoamines and their analogs
Authors: Carlström D. , Bergin R. , Falkenberg G.
Published: March 2009

Until recently there has been very limited information concerning the molecular geometry and conformation of biogenic monoamines and this lack of knowledge has seriously hampered efforts to unravel the structure—function relationships at the molecular level. Nevertheless, several theories have been proposed regarding interaction between the monoamines and their receptor sites. This is especially true for the neurohumoral transmitters dopamine, noradrenaline (norepinephrine) and serotonin (5-hydroxytryptamine), the target areas of which seem to be specific not only in the sense of chemical structure but also from the steric point of view. The well-known differences in biological activity due to chiralty illustrate the importance of the three-dimensional architecture of the molecules and indicate also the presence of stereospecific receptor sites. A detailed knowledge of the conformation of the biogenic monoamines would not only elucidate the requirements upon a natural or synthetic monoamine for proper function but also give indirect information about the geometry of the receptor sites.
Prospects in genetic engineering of plants
Authors: Heyn R. Frans , Rörsch Arthur , Schilperoort Robbert A.
Published: March 2009

Genetic engineering has quite rightly an image of science fiction. The time when new species with any wanted combination of genetic properties can be ordered from an animal or plant breeding factory seems far away. The layman's view that the science fiction of today is the reality of tomorrow is certainly an insufficient argument to justify optimism. If this were so, we should by now be able to produce hybrids between members of the animal and plant kingdom as was foreseen by a nineteenth-century equivalent of Fred Hoyle (see Fig. I). Despite the scepsis expressed by the prominent scientist Si.r Macfarlane Burnet in his bookGenes, Dreams and Realities(1971), recent advances in molecular genetics have raised new enthusiasm (and uneasiness) which make people speak of genetic engineering as something to aim at as an approach to correct inborn errors of metabolism. This will, however, not be our principal dish if we restrict ourselves to a vegetarian menu. We view genetic engineering of plants not only as a future method to improve species, but also as a fundamental approach to the study of gene expression, especially with respect to cell differentiation. If we consider the term literally, the definition of genetic engineering might be any intentional genetic manipulation to alter species or to make new ones. In this sense genetic engineering was practised long before Mendel presented his laws (1865). In the seventeenth century the bulb growers of the Low Countries produced new varieties of tulips for which prices of a thousand forms each were paid (at the 1636 price index!). We notice here already a strong impact of genetic engineering on society; the so-called crazy tulip trade caused a financial disaster on the Amsterdam stock-exchange comparable to the Wall Street crash in the 1930s.
Heavy metal toxicities
Authors: Bremner Ian
Published: March 2009

Several reviews have been published recently on the toxicity of heavy metals, but few of these have made any reference to the influence of the nutritional state of animals upon their tolerance of heavy metals. Furthermore, the clinical and metabolic changes occurring as a consequence of increased dietary intake of heavy metals are extremely dependent on factors such as the mineral composition of the diet and nature of the protein source. These aspects will be given particular attention in this review.
The control system regulating breathing in man
Authors: Cunningham D. J. C.
Published: March 2009

This review takes the regulation of breathing in man as an example of a highly developed and much studied control system in higher mammals.
Free-energy dissipation constrainst on the accuracy of enzymatic selections
Authors: Blomberg C. , Ehrenberg M. , Kurland C. G.
Published: March 2009

A bacterium incorporates amino acids into protein with an error frequency close to one in three thousand (Edelman & Gallant, 1977). Nevertheless, the structural differences between related amino acids are so small that it is difficult to see how they can be distinguished from each other with such accuracy (see, for example, Pauling, 1958).

Indeed, the selection of amino acids during protein synthesis is carried out twice: first by the aminoacyl-tRNA synthetases and then by the codon-programmed ribosome. Each of these substrate selections is in fact a double selection. In the case of the synthetase both a particular amino acid and a corresponding cognate tRNA must be chosen to form the aminoacyl-tRNA. On the ribosome, the aminoacyl-tRNA must be matched with a cognate codon, and then the mRNA must be advanced by exactly one codon length to position the next codon in the appropriate ribosome site so that it too can be translated.
Allosteric interpretation of haemoglobin properties
Authors: Shulman R. G. , Hopfield J. J , Ogawa S.
Published: March 2009

It is our purpose to review recent experiments on haemoglobin in order to discuss them in terms of the two state model of cooperativity. Excellent previous reviews are available of the chemistry of haemoglobin (Antonini & Brunori, 1971; Gibson, 1959b) which are referred to when possible. The plethora of data necessitates that a selection must be made in a review. An intentionally wide range of experiments is selected to exhibit
The physical aspects of energy transduction in biological systems
Authors: Blumenfeld L. A.
Published: March 2009

The primary energy sources for all the organisms living on the Earth are either sunlight or the energy liberated during chemical transformations (mainly, oxidation) of certain substances – food. Within the cell this energy is transformed, accumulated, and then utilized to ensure a multitude of processes (synthesis of new low- and high-molecular compounds, muscle contraction, luminescence, transfer of ions counter to their concentration gradients, etc.).

The role of universal ‘energy keeper’, of the, as it were, ‘energy small change’ in biology is played by the molecules of adenosine tri- phosphate (ATP) whose hydrolytic dissociation in water solutions with the formation of adenosine diphosphate (ADP) and inorganic phosphate (P1) is accompanied by a rather strong decrease of system energy.†
Multi-stage proofreading in DNA replication
Authors: Beckman Robert A. , Loeb Lawrence A.
Published: March 2009

The mechanisms by which DNA polymerases achieve their remarkable fidelity, including base selection and proofreading, are briefly reviewed. Nine proofreading models from the current literature are evaluated in the light of steady-state and transient kinetic studies ofE. coliDNA polymerase I, the beststudied DNA polymerase.
Experimental methods for investigating protein adsorption kinetics at surfaces
Authors: Ramsden Jeremy J.
Published: March 2009

The adsorption of proteins at the solid-liquid interface is a process of fundamental importance in nature. Extensive reviews (MacRitchie, 1978; Andrade & Hlady, 1986; Norde, 1986) testify to the strong interest which has been shown in the problem during the past few decades. Norde & Lyklema (1978) have rightly pointed out that protein adsorption is scientifically intriguing; the phenomenology is complicated and includes many presently apparently irreconcilable observations.
Applications of ultrafast laser spectroscopy for the study of biological systems
Authors: Holzwarth Alfred R.
Published: March 2009

The discovery of mode-locked laser operation now nearly two decades ago has started a development which enables researchers to probe the dynamics of ultrafast physical and chemical processes at the molecular level on shorter and shorter time scales. Naturally the first applications were in the fields of photophysics and photochemistry where it was then possible for the first time to probe electronic and vibrational relaxation processes on a sub-nanosecond timescale. The development went from lasers producing pulses of many picoseconds to the shortest pulses which are at present just a few femtoseconds long. Soon after their discovery ultrashort pulses were applied also to biological systems which has revealed a wealth of information contributing to our understanding of a broadrange of biological processes on the molecular level.It is the aim of this review to discuss the recent advances and point out some future trends in the study of ultrafast processes in biological systems using laser techniques. The emphasis will be mainly on new results obtained during the last 5 or 6 years. The term ultrafast means that I shall restrict myself to sub-nanosecond processes with a few exceptions.
Molecular Tuning of Ion Binding to Calcium Signaling Proteins
Authors: Falke Joseph J. , Drake Steven K. , Hazard Andrea L. , Peersen Olve B.
Published: March 2009

Intracellular calcium plays an essential role in the transduction of most hormonal, neuronal, visual, and muscle stimuli. (Recent reviews include Putney, 1993; Berridge, 1993a,b; Tsunoda, 1993; Gnegy, 1993; Bachset al.1992; Hanson & Schulman, 1992; Villereal & Byron, 1992; Premack & Gardner, 1992; Meanset al.1991).
DNA–carcinogen interaction: covalent DNA-adducts of benzo(a)pyrene 7, 8-dihydrodiol 9, 10-epoxides studied by biochemical and biophysical techniques
Authors: Gräslund Astrid , Jernström Bengt
Published: March 2009

Exposure to various chemicals, either due to occupation or lifestyle, is considered to be a major contributing factor to tumour formation in man (Higginson, 1969; Doll and Peto, 1981). An important and prevalent class of potent carcinogeniccompounds present in the environment is polycyclic aromatic hydrocarbons(PAHs), which are found in various petroleum and combustion products derived from heat and power generation and motor vehicle exhausts (Baum, 1978). Furthermore, since PAHs are generally formed by pyrolysis of organic matters such as tobacco smoking and certain procedures of food preparation, the PAH exposure to humans is extensive.
Allosteric linkage-induced distortions of the prosthetic group in haem proteins as derived by the theoretical interpretation of the depolarization ratio in resonance Raman scattering
Authors: Schweitzer-Stenner Reinhard
Published: March 2009

The relationship between functional properties of haem proteins, particularly ligand binding and Bohr effect, and associated variations of the tertiary and quaternary structures is one of the main objectives of haem protein research. In this context one aims to get detailed knowledge of the coupling mechanisms which are involved in the transduction of structural changes from the protein to the functional haem group along distinct pathways.
Ionic regulation of egg activation
Authors: Whitaker M. J. , Steinhardt R. A.
Published: March 2009

Developing cells have constantly to make decisions: when to proliferate and divide, when and how to differentiate. It is an increasingly attractive idea that these decisions involve changes in intracellular cation concentrations. Our ideas about the mechanisms of changes in intracellular cations come largely from the application of biophysical techniques in the study of excitable tissues. These ideas are proving very valuable to the investigation of the control of proliferation and cell development and it is evident that the ionic mechanisms which pertain in nerve and muscle have their counterparts in other cells. Just as alterations in intracellular ion concentrations serve a signalling function in excitable tissue, so too they act as signals during development. Since almost all the quantitative data on the ionic mechanisms of fertilization come from work on sea urchins we have confined our review to sea urchin eggs.
Thermodynamics and membrane processes
Authors: Klein Roger A.
Published: March 2009

This review represents a personal view of membrane thermodynamics. I do not intend to deal at all with the irreversible thermodynamics of membrane mass transfer processes. This aspect has been covered far more competently and completely by other people (Bittar, 1970; Paterson, 1970; Rottenberg, Caplan & Essig, 1970; Mitchell, 1970; Rothschildet al.1980; Oster, Perelson & Katchalsky, 1973; Kedem & Katchalsky, 1958; Schwartz, 1971). The recent review on osmosis by Hill (1979) is a particularly succinct appraisal of a facet of irreversible membrane thermodynamics. Arata & Nishimura (1980) have considered the coupling of electron transfer to vectorial processes in biological membranes.
Bacteriorhodopsin: a biological material for information processing
Authors: Oesterhelt Dieter , Bräuchle Christoph , Hampp Norbert
Published: March 2009

Technology which makes use of biological materials has advanced dramatically in the last few decades. Production of specific biochemicals by selected microbial strains, the use of enzymes for stereospecific biosynthesis of materials and gene technological production of biologically important macromolecules are a few examples of these developments.
Damage to proteins due to the direct action of ionizing radiation
Authors: Kempner E. S.
Published: March 2009

Proteins exposed to ionizing radiation suffer both reversible and irreversible effects. Reversible effects are defined as those which disappear in a short period of time after the removal of the radiation field and without further treatment of the sample. Irreversible effects are those which cause a permanent alteration in the structure of a protein.
Interrelations of bioenergetic and sensory functions of the retinal proteins
Authors: Skulachev Vladimir P.
Published: March 2009

Rhodopsins are intrinsic membrane retinal-containing proteins composed of 7 hydrophobic a-helical transmembrane columns and hydrophilic sequences of various length connecting the helices and localized at N- and C-ends of the polypeptide. The chromophore (retinal) forms a Schiff base with a lysine residue in the middle part of the last a-helix. Absorption of a photon results in isomerization of retinal which gives rise to a conformational change in the protein moiety.
Distance geometry and related methods for protein structure determination from NMR data
Authors: Braun Werner
Published: March 2009

The method of choice to reveal the conformation of protein molecules in atomic detail has been X-ray single-crystal analysis. Since the first structural analysis of diffraction patterns, computer calculations have been an important tool in these studies (Blundell & Johnson, 1976). As is described by Sheldrick (1985), it has been taken for granted that a necessary first step in the determination of a protein structure would be writing computer programs to fit structure factors. In contrast the combined use of the structural analysis of NMR data and computer calculations has been quite limited. An early attempt of such structural calculations was the quantitative determination of mononucleotide conformations in solution using lanthanide ion shifts (Barry et al. 1971).
NMR studies of kinetics in cells and tissues
Authors: Brindle Kevin M. , Campbell Iain D.
Published: March 2009

An exciting aspect of NMR spectroscopy is its ability to monitor, non-invasively, a variety of small molecules in cells and tissues. This leads to the possibility of investigating details of cellular biochemistry previously obscured by separation and purification procedures.
Quantum mechanical calculations of NMR chemical shifts in nucleic acids
Authors: Giessner-Prettre C. , Pullman B.
Published: March 2009

During the last twenty-five years the development of quantum mechanical calculations and experimental measurements of chemical shifts of the different type of nuclei present in nucleic acids have run parallel in close relation to each other. The first calculations dealt with intramolecular effects on base proton shifts (Veillard, 1962) but the real breakthrough of the theory occurred with the advent of computations of intermolecular shielding due to the ring current effect of the nucleic acid bases (Giessner-Prettre & Pullman, 1970).
Kinetic analysis of lipid soluble ions and carriers
Authors: Hladky S. B.
Published: March 2009

The advent of methods for forming and studying lipid bilayer membranes (Mueller et al. 1962; Hanai et al. 1964) opened the way for some fifteen years of
intensive and productive study of the properties of lipid soluble ions and ion carriers. I expect that none will dissent from the view that Peter Läuger and his associates, including R. Benz and G. Stark, did more than any other research group to advance the study of the mechanism of the charge transfer. Between 1970 and 1981 they published more than 25 substantial contributions. Thus it is appropriate that this memorial issue should contain a short review of this subject. As I have the highest regard for their work I was very pleased to be asked to write such a chapter. There is little point in providing another general survey because Läuger's group published reviews at the end of this period (Benz et al. 1980; Läuger et al. 1981) and I also reviewed the field at length (Hladky, 1979a). Instead I would like to consider the three cornerstone papers of 1971, some of the difficulties that arose from those papers, how they were overcome, and three aspects of the description that are still incomplete.
Magnetic resonance studies of enzymesubstrate complexes with paramagnetic probes as illustrated by creatine kinase
Authors: Cohn Mildred
Published: March 2009

Only two spectroscopic methods are capable of detecting individual atoms in macromolecular systems, X-ray diffraction in the crystalline state and nuclear magnetic resonance (NMR) in the liquid state. For an enzyme-substrate complex, X-ray diffraction can yield information on the geometric structure at the active site and nuclear magnetic resonance absorption can, in principle, yield information on the electronic structure at the active site and on the conformation of enzyme-substrate complexes. Both types of information are needed for unraveling the mechanism of enzyme catalysis on the molecular level. The exciting successes of X-ray diffraction in delineating active sites are already established; NMR, a comparative latecomer among spectroscopic techniques is just beginning to demonstrate its potentialities. McDonald & Phillips have summarized in their excellent review (1969) the work on direct observation of hydrogen atoms (protons) by NMR spectroscopy which has advanced our knowledge of protein structure. The extensive studies of Jardetzky and his co-workers on the NMR of ribonuclease and its inhibitor complexes has culminated in a suggested mechanism of catalytic action (Robertset al.1969).
Physics and chemistry of spin labels
Authors: McConnell Harden M. , McFarland Betty Gaffney
Published: March 2009

Biological systems provide the physical chemist with an abundance of interesting, challenging and significant problems. One example is the problem of the molecular basis of co-operative or allosteric interactions between distant ligand or substrate binding sites in hemoglobin and in enzymes. This problem has been discussed recently inThis Journalby Eigen (1968) and by Wyman (1968). Another particularly challenging problem is the molecular organization of biological membranes. Such problems tend to be particularly resistant to solution by the straight-forward application of most spectroscopic techniques, in large part because of the enormous chemical and spectroscopic complexity of biological macromolecules. This spectroscopic complexity has stimulated the use of various ‘probes’ that can be introduced into selected sites in complex systems to provide spectroscopic signals that are comparatively free from interference. The use of heavy metal atoms (‘isomorphous replacement’) in X-ray studies of protein crystals (Green, Ingram & Perutz, 1954), and fluorescent dyes in the study of proteins in solutions (Weber, 1953; Steiner & Edelhoch, 1962) are early examples. Spin labels represent a new member of the family of spectroscopic structural probes. A spin label is a synthetic paramagnetic organic free radical, usually having a molecular structure and/or chemical reactivity that results in its attachment or incorporation at some particular target site in a biological macromolecule, or assemblage of macromolecules (Ohnishi & McConnell, 1965; Stoneet al.1965). This type of probe is being used in our laboratory to study allosteric interactions in proteins, and molecular dynamics and organization in membranes.
Surmounting barriers in ionic channels
Authors: Cooper K. E. , Gates P. Y. , Eisenberg R. S.
Published: March 2009

Biological cells are defined by the membrane that shields their vital molecules from the environment. The lipid bilayer of the membrane is an effective dielectric shield (Parsegian, 1969; Andersen, 1978; Honiget al.1986), preventing penetration by charged molecules: the lipid presents a large electrostatic energy barrier because it cannot neutralize the charge of solute molecules nearly as well as water. This energy barrier inhibits the permeation of solutes with local charge, even metabolites. Of course, metabolites do enter cells, and so physiologists have suspected (for a very long time, Hille, 1984, ch. 8) that the membrane shield is pierced by aqueous channels, through which solutes diffuse (with their local charge substantially neutralized) as they cross the membrane. These aqueous pores now have molecular reality (e.g. Nodaet al.1984; Miller, 1986). Each is formed by a specialized protein, integral to membranes, perhaps shaped like a thick-walled pipe, called ionic channels. Channels control the movement of many important molecules in and out of cells by the ‘gating’ mechanism that controls their opening and closing and by the selective properties of their open channel.
Theories of associative recall
Authors: Longuet-Higgins H. C. , Willshaw D. J. , Buneman O. P.
Published: March 2009

The problem of how the brain stores and retrieves information is ultimately an experimental one, and its solution will doubtless call for the combined resources of psychology, physiology and molecular biology. But it is also a problem of great theoretical sophistication; and one of the major tasks confronting the brain scientist is the construction of theoretical models which are worthy of, and open to, experimental test. In this review we shall be concerned with the latter aspect of the problem of memory, which has attracted quite a lot of attention in the last few years. It is early yet to judge the relative merits of the various models in any detail; but as we shall see, most of those which have been developed beyond their initial hypotheses have a certain family resemblance, and it seems as if we may now be in possession of the basic ideas which will be needed for the understanding of one of the central problems of memory, namely the mechanism of associative recall.
Three-dimensional crystallization of membrane proteins
Authors: Kühlbrandt W.
Published: March 2009

As recently as 10 years ago, the prospect of solving the structure of any membrane protein by X-ray crystallography seemed remote. Since then, the threedimensional (3-D) structures of two membrane protein complexes, the bacterial photosynthetic reaction centres ofRhodopseudomonas viridis(Deisenhoferet al.1984, 1985) and ofRhodobacter sphaeroides(Allenet al.1986, 1987a, 6; Changet al.1986) have been determined at high resolution. This astonishing progress would not have been possible without the pioneering work of Michel and Garavito who first succeeded in growing 3-D crystals of the membrane proteins bacteriorhodopsin (Michel & Oesterhelt, 1980) and matrix porin (Garavito & Rosenbusch, 1980). X-ray crystallography is still the only routine method for determining the 3-D structures of biological macromolecules at high resolution and well-ordered 3-D crystals of sufficient size are the essential prerequisite.
Linear dichroism spectroscopy of nucleic acids
Authors: Norden Bengt , Kubista Mikael , Kurucsev Tomas
Published: March 2009

This review will consider solution studies of structure and interactions of DNA and DNA complexes using linear dichroism spectroscopy, with emphasis on the technique of orientation by flow. The theoretical and experimental background to be given may serve, in addition, as a general introduction into the state of the art of linear dichroism spectroscopy, particularly as it is applied to biophysical problems.
Genetics of the nervous system inDrosophila
Authors: Hall Jeffrey C.
Published: March 2009

The genetic analysis ofDrosophilaneurobiology has expanded into a considerable field. A host of genetic variants is now available for analyzing the development, structure, physiology, and chemistry of the fly's excitable cells and tissues and how they control the animal's behavior.
The effect of high pressure upon proteins and other biomolecules
Authors: Weber Gregorio , Drickamer Harry G.
Published: March 2009

We shall not attempt here to enumerate the results or review in a systematic way the significant literature dealing with the use of high pressure in studies of proteins and other molecules of biological interest. Two recent reviews on this subject, one by MOrild (1981) and another by Heremans (1982), and a further article by Jaenicke (1981) on enzymes under extreme environmental conditions contain expositions and references that would render redundatn such a task. Rather we concentrate here on the examination of othe conceptual framework employed in the interpretation of high pressure experiments and in the critical discussion of our knowledge of selected areas of present interest and likely future significance.
Electric linear dichroism and birefringence of biological polyelectrolytes
Authors: Charney Elliot
Published: March 2009

The phenomenon of electro-optic orientation was discovered by John Kerr in 1875 and has been used extensively for determining the optical polarizability anisotropy of small molecules and for high-speed transmission of optical signals. Measurements on biopolymers have been made at least since 1950, but only in the last decade have these yielded definitive structural and physical information. In the course of this review, it should become obvious that among the reasons for this late development is the inherent difficulty of analysing optical data that depend simultaneously on intrinsic optical-structural properties of the molecules, and on their degree of orientation under the conditions of the experiment. The problem has been particularly difficult far biopolymers such as the nucleic acids, whose polarization in an electric field is dependent on their special polyelectrolyte properties. These unique electrostatic properties are an important feature in the interpretation of the experimental observations.
The sodium channel of excitable and non-excitable cells
Authors: Villegas R. , Villegas Gloria M. , Rodriguez-Grille J. M. , Sorais-Landaez F.
Published: March 2009

Excitation and conduction in the majority of excitable cells, as originally described in the squid axon, are initiated by a transient and highly selective increase of the membrane Na conductance, which allows this ion to move passively down its electrochemical gradient (Hodgkin & Katz, 1949; Hodgkin & Huxley, 1952). The term ‘Na channel’ was introduced to describe the mechanism involved in this conductance change (Hodgkin & Keynes, 1955).
The physical principles of energy transduction in chloroplast thylakoid membranes
Authors: Thorne S. W. , Duniec J. T.
Published: March 2009

Photosynthesis in green plants or algae may be represented by an overall equation:

The energy necessary to promote this overall reaction is derived from light through absorption by pigment molecules — chiefly the chlorophylls.

Photosynthesis occurs in chloroplasts - subcellular organelles in which all the chlorophyll pigments are located. The chloroplasts comprise membranous, structures, and can be classified into two types. To the first type belong chloroplasts with appressed stacks of lamellar membranes, termed grana. These chloroplasts occur in mesophyll cells (C3plants). The second type of chloroplasts are those with lamellar membranes that do not form the grana structures; they occur in bundle sheath cells of maize and other monocotyledons (C4plants, Hatch & Slack, 1970). In algae a greater diversity of structure occurs (Kirk & Tilney-Basset, 1978). Fluorescence microscopy indicates that chlorophyll molecules are localized mainly in the grana membrane regions of mesophyll-type chloroplasts and uniformly throughout the bundle sheath cells (Spencer & Wildman, 1962). Mesophyll chloroplasts are flattened saucer-shaped organelles (20 or more in each cell) of between 5000 and 10000 nm in diameter, and of thickness 1000–2000 nm, whilst the individual grana are each of the order of 300–500 nm in diameter. The available evidence suggests that individual lamellar membranes are arranged to form vesicles, or sacks where the internal space is completely delimited from the external space. These individual closed membrane structures were termed thylakoids (Menke, 1962).
The localization and assay of chemical elements by microprobe methods
Authors: Hall T. A. , Gupta Brij L.
Published: March 2009

The principle of the microprobe analysis of chemical elements is illustrated in Fig. i. Some kind of radiation is directed on to the specimen, generating signals characteristic of the elements present. Local analysis in situ is achieved in one of two ways. Most often the impinging beam is finely focused so that the signal at any moment comes only from a selected microregion. Alternatively, in some instruments, the impinging beam floods a larger region but the emergent signals characteristic of a particular element may be selected and focused to give an elemental ‘map’ or ‘image’.
Amino acid sequence, haem-iron co-ordination geometry and functional properties of mitochondrial and bacterial c-type cytochromes
Authors: Senn Hans , Wüthrich Kurt
Published: March 2009

Cytochromes are found in all biological oxidation Systems which involve transport of reducing equivalents through organized chains of membrane bound intermediates, regardless of the ultimate oxidant (Keilin, 1966; Bartsch, 1978; Meyer & Kamen, 1982). Thus, cytochromes are present not only in the aerobic mitochondrial and bac-terial respiratory chain, but are also found in much more diversified procariotic Systems, including all varieties of facultative anaerobes (nitrate and nitrite reducers), obligate anaerobes (sulphate reducers and phototrophic sulphur bacteria), facultative photoheterotrophes (phototrophic non-sulphur purple bacteria), and the photoautotrophic cyanobacteria (blue-green algae). Among the different types of cytochromes occurring in the cell, the soluble c-type cytochromes (‘class I’, Meyer & Kamen, 1982) are the most abundant and best characterized group of proteins (Bartsch, 1978; Meyer & Kamen, 1982; Dickerson & Timkovitch, 1975; Lemberg & Barrett, 1973; Salemme, 1977; Ferguson-Miller, Brautigan & Margoliash, 1979). The amino acid sequences of more than 80 mitochrondrial and close to 40 bacterial cytochromes c are known (Meyer & Kamen, 1982; Dickerson & Timkovitch, 1975; Schwartz & Dayhoff, 1976; Dayhoff & Barker, 1978).
Free energy cost and accuracy in branched selection processes of biosynthesis
Authors: Blomberg Clas
Published: March 2009

Selection in biochemical synthesis processes is a very important task: processes as protein or nucleic acid synthesis must be very accurate although the cell abounds with closely related molecules which, intuitively, should be difficult to distinguish. The mechanisms of selection and the underlying processes have been extensively studied in the last years, and the ideas have been developed into mathematical models to visualize the potentials of recognition and error correction. There are several aspects on this, the main aspect of the present work being the important fact that the cell must pay for the increased accuracy in terms of available free energy: processes are driven from equilibrium, and do away with appreciable dissipation.
Structures and mechanisms of DNA restriction and modification enzymes
Authors: Modrich Paul
Published: March 2009

DNA restriction and modification enzymes are responsible for the hostspecific barriers to interstrain and interspecies transfer of genetic information that have been observed in a variety of bacterial cell types. Although the phenomenon of host specificity was initially observed in the early 1950s (Luria & Human, 1952; Bertani & Weigle, 1953), it was nearly a decade later that Arber and his colleagues accurately predicted the molecular basis of the phenomenon. Their experiments with bacteriophage λ demonstrated that a given host-specificity system imparts a specific modification to the viral DNA, and further, that restriction of DNA lacking the appropriate modification is s consquence of nucleolytic hydrolysis upon entry into the host cell (Arber & Dussoix, 1962; Dussoix & Arber, 1962; Arber, Hattman & Dussoix, 1963).