This compendium presents some of the major applications of neutron scattering techniques to problems in biology. It is a record of the papers presented at the Neutrons in Biology Conference, the third in an occasional series held to highlight progress in the field and to provide a focus for future direction. The strength ofthe neutron scattering technique remains principally in the manipula tion of scattering density through hydrogen and deuterium atoms. The development ofad vanced detectors, innovative instrument and beamline components, and sophisticated data acquisition systems through the 1970s and early 1980s provided a sound foundation for the technique. With continued development, some of the exotic and expensive equipment has become affordable by the medium-sized facilities, thereby broadening the user base considerably. Despite problems with the major neutron sources in the late 1980s and early 1990s, some spectacular results have been achieved. Whilst the high and medium flux beam reac tors will continue to make a major impact in the field, the results from the first experi ments, and the planned developments on spallation neutron sources, clearly indicate that the technique has enormous potential.
This Thesis in biological physics has two components, describing the use of X-ray scattering techniques to study the structure of two different stacked lipid membrane systems. The first part focuses on the interaction between a short 11-mer peptide, Tat, which is part of the Tat protein in the HIV-1 virus. Although highly positively charged, the Tat protein has been shown to translocate through hydrocarbon lipid bilayers easily, without requiring the cell’s energy, which is counter to its Born self-energy. In this work Tat’s location in the headgroup region was demonstrated using a combined X-ray scattering and molecular dynamics approach. Bilayer thinning was observed as well as softening of different membrane mimics due to Tat. It was concluded that Tat’s headgroup location, which increases the area/lipid, and its bilayer softening likely reduce the energy barrier for passive translocation. The second part is a rigorous investigation of an enigmatic phase in the phase diagram of the lipid dimyristoylphosphatidylcholine (DMPC). The ripple phase has fascinated many researchers in condensed matter physics and physical chemistry as an example of periodically modulated phases, with many theoretical and simulation papers published. Despite systematic studies over the past three decades, molecular details of the structure were still lacking. By obtaining the highest resolution X-ray data so far, this work revealed the complex nature of the chain packing, as well as confirming that the major side is thicker than the minor side of the saw-tooth ripple structure. The new model shows that the chains in the major arm are tilted with respect to the bilayer normal and that the chains in the minor arm are slightly more disordered than all-trans gel-phase chains, i.e., the chains in the minor arm are more fluid-like. This work provides the highest resolution X-ray structure of the ripple phase to-date.
The latest developments in quantum and classical molecular dynamics, related techniques, and their applications to several fields of science and engineering. Molecular simulations include a broad range of methodologies such as Monte Carlo, Brownian dynamics, lattice dynamics, and molecular dynamics (MD). Features of this book: • Presents advances in methodologies, introduces quantum methods and lists new techniques for classical MD • Deals with complex systems: biomolecules, aqueous solutions, ice and clathrates, liquid crystals, polymers • Provides chemical reactions, interfaces, catalysis, surface phenomena and solids Although the book is not formally divided into methods and applications, the chapters are arranged starting with those that discuss new algorithms, methods and techniques, followed by several important applications.
Author: Committee on Planetary and Lunar Exploration
Publisher: National Academies Press
Since its discovery in 1610, Europa-one of Jupiter's four large moons-has been an object of interest to astronomers and planetary scientists. Much of this interest stems from observations made by NASA's Voyager and Galileo spacecraft and from Earth-based telescopes indicating that Europa's surface is quite young, with very little evidence of cratering, and made principally of water ice. More recently, theoretical models of the jovian system and Europa have suggested that tidal heating may have resulted in the existence of liquid water, and perhaps an ocean, beneath Europa's surface. NASA's ongoing Galileo mission has profoundly expanded our understanding of Europa and the dynamics of the jovian system, and may allow us to constrain theoretical models of Europa's subsurface structure. Meanwhile, since the time of the Voyagers, there has been a revolution in our understanding of the limits of life on Earth. Life has been detected thriving in environments previously thought to be untenable-around hydrothermal vent systems on the seafloor, deep underground in basaltic rocks, and within polar ice. Elsewhere in the solar system, including on Europa, environments thought to be compatible with life as we know it on Earth are now considered possible, or even probable. Spacecraft missions are being planned that may be capable of proving their existence. Against this background, the Space Studies Board charged its Committee on Planetary and Lunar Exploration (COMPLEX) to perform a comprehensive study to assess current knowledge about Europa, outline a strategy for future spacecraft missions to Europa, and identify opportunities for complementary Earth-based studies of Europa. (See the preface for a full statement of the charge.)
I get by with a little help from my friends The Beatles: Sgt. Pepper This book should have been in Danish. Any decent person must be able to express himself in his mother's tongue, also when expounding scientific ideas and results. Had I stuck to this ideal, the book would have been read by very few people, and, indeed, appreciated by even fewer. Having it publ ished in English gives me a chance to fulfill one ambition: to be read and judged by the international scientific community. Another reason is that the majority of my professional friends are regrettably unread in Danish, just as I am in Hebrew, Finnish and even Italian. I want to deprive them of the most obvious excuse for not reading my opus. Like a man I admired, I will first of all thank my wife. In his autobiography, Meir Weisgal, then President of the Weizmann Insti tute of SCience, wrote about his wife: "In addition to her natural endowments - which are considerable - she was a more than competent part-tim~ secretary." He wrote on, and so shall I. The book has been edited by my wife. So if the reader finds the layout pleasant as, in actual fact, I myself do, Birgit is to be praised. If there are blemishes, I am to be blamed for not having caught them.
Biological systems are regulated by the thermodynamic parameters of pressure and temperature. New analytical and computational methods and various kinds of spectroscopy allow detailed studies of the structure and function of biological systems under extreme conditions, as well as the possibility to explicate the origin and evolution of life. This volume addresses researchers and students exploring the new world of biological systems under extreme environmental conditions.
Advances in Biological and Medical Physics, Volume 15 covers papers on the productive applications of physical science in biology and medicine. The book presents articles dealing with the geometric influence of bone matrix on the differentiation of fibroblasts and information on human repetitious DNA; the complexity of the human genome; and possible directions for future research. The text then describes the problem of biological time. The microcirculatory basis of fluid exchange is also considered. The book concludes with articles dealing with the possibilities for electron microscopy and diffraction of wet, unstained and unfixed biological material, as well as with the metabolic events in localized compartments of the living cell carried out through the use of rapid microspectrofluorometry. Biological and medical physicists and students taking these courses will find the book invaluable.
It is possible to "stretch" a liquid and, when suitably prepared, liquids are capable of sustaining substantial levels of tension, often for significant periods of time. These negative pressure states are metastable but can last for days - long enough for substantial experimental investigation. This volume is a review of recent and current research into the behaviour of liquids under negative pressure. Part I deals with the thermodynamics of stretched liquids. Part II discusses the physical and chemical behaviour of liquids under negative pressure. Part III contains papers on the effect of negative pressure on the solidification of a liquid. Part IV is devoted to stretched helium and Part V discusses cavitation in various stretched liquids. Part VI deals with the effect of foreign substances on cavitation.