Gerald H. Pollack – författare

Elastic filaments refer mainly to titin, the largest of all known proteins. Titin was discovered initially in muscle cells, where it interconnects the thick filament with the Z-line. Titin forms a molecular spring that is responsible for maintaining the structural integrity of contracting muscle, ensuring efficient muscle contraction. More recently, it has become clear that titin is not restricted to muscle cells alone. For example, titin is found in chromosomes of neurons and also in blood platelets. This topic is fast becoming a focal point for research in understanding viscoelastic properties at the molecular, cellular, and tissue levels. In titin may lie a generic basis for biological viscoelasticity. It has become clear that titin may hold the key to certain clinical anomalies. For example, it is clear that titin-based ventricular stiffness is modulated by calcium and that titin is responsible for the altered stiffness in cardiomyopathies. It is also clear from evidence from a group of Finnish families that titin mutations may underlie some muscular dystrophies and that with other mutations chromatids fail to separate during mitosis.Thus, it is clear that this protein will have important clinical implications stemming from its biomechanical role. One aspect of this field is the bringing together of bioengineers with clinical researchers and biologists. Genetic and biochemical aspects of titin-related proteins are being studied together with front-line engineering approaches designed to measure the mechanics of titin either in small aggregates or in single molecules.

What is meant by the ‘state of water?’ Few would question that water coming out of a household tap is a liquid, but water in an ice cube is something altogether different: it is a solid that floats on tap water (also known as bulk water).

Phase transitions occur throughout nature. The most familiar example is the one that occurs in water – the abrupt, discontinuous transition from a liquid to a gas or a solid, induced by a subtle environmental change. Practically magical, the ever-so-slight shift of temperature or pressure can induce an astonishing transition from one entity to another entity that bears little resemblance to the first.So "convenient" a feature is seen throughout the domains of physics and chemistry, and one is therefore led to wonder whether it might also be common to biology. Indeed, many of the most fundamental cellular processes are arguably attributable to radical structural shifts triggered by subtle changes that cross a critical threshold. These processes include transport, motion, signaling, division, and other fundamental aspects of cellular function.Largely on the basis of this radical concept, a symposium was organized in Poitiers, France, to bring together people who have additional evidence for the role of phase transitions in biology, and this book is a compendium of some of the more far-reaching of those presentations, as well as several others that seemed to the editors to be compelling.The book should be suitable for anyone interested in the nature of biological function, particularly those who tire of lumbering along well trodden pathways of pursuit, and are eager to hear something fresh. The book is replete with fresh interpretations of familiar phenomena, and should serve as an excellent gateway to deeper understanding.

This volume presents the entire proceedings of the symposium organized by one of us (H. S. ) on November 11 to 15, 1991 at Hakone, Japan, under the title of "Mechanism of Myofllament Sliding in Muscle Contraction. " Among various kinds of energy transduction mechanisms in biological systems, the mechanism of muscle contraction has been studied most intensively and extensively over many years. Since the monumental discovery by the two Huxleys and coworkers that muscle contraction results from relative sliding between the thick and thin myofilaments, attention of muscle investigators has been focused on the question, what makes the fllaments slide past one another. In response to the above question, A. F. Huxley and Simmons put forward a contraction model in 1971, in which globular heads of myosin (cross-bridges) extending from the thick fllament first attach to actin on the thin fllament, and then change their angle of attachment to actin (power stroke) leading to force generation or myofilament sliding until they detach from the thin fllament. The rocking cross-bridge contraction model seemed to be entirely consistent with the kinetic scheme of actomyosin ATPase published by Lymn and Taylor at the same time, thus giving a strong impression to the people concerned that the muscle contraction mechanism would soon be sorted out. In his review lecture in 1974, however, A. F.

Elastic filaments refer mainly to titin, the largest of all known proteins. Titin was discovered initially in muscle cells, where it interconnects the thick filament with the Z-line. Titin forms a molecular spring that is responsible for maintaining the structural integrity of contracting muscle, ensuring efficient muscle contraction. More recently, it has become clear that titin is not restricted to muscle cells alone. For example, titin is found in chromosomes of neurons and also in blood platelets. This topic is fast becoming a focal point for research in understanding viscoelastic properties at the molecular, cellular, and tissue levels. In titin may lie a generic basis for biological viscoelasticity. It has become clear that titin may hold the key to certain clinical anomalies. For example, it is clear that titin-based ventricular stiffness is modulated by calcium and that titin is responsible for the altered stiffness in cardiomyopathies. It is also clear from evidence from a group of Finnish families that titin mutations may underlie some muscular dystrophies and that with other mutations chromatids fail to separate during mitosis. Thus, it is clear that this protein will have important clinical implications stemming from its biomechanical role. One aspect of this field is the bringing together of bioengineers with clinical researchers and biologists. Genetic and biochemical aspects of titin-related proteins are being studied together with front-line engineering approaches designed to measure the mechanics of titin either in small aggregates or in single molecules.

`In contrast to common practice, we have always tried to include as many discussions held at the meeting in our proceedings as possible, so as to enable readers to properly evaluate each paper presented, as well as to learn of future prospects in this field of research. Although the policy of including discussions occasions a long publication delay, we believe that it is worth repeating in our future publication, as we have met a number of young investigators fascinated by the discussions in our proceedings.... In the concluding remarks in this volume, Dr. Hugh E. Huxley, a principal architect of the sliding filament mechanism of muscle contraction, states that the molecular mechanism of myofilament sliding remains mysterious to all of us. We hope that this volume will stimulate muscle investigators to design and perform novel experiments to clarify the mysteries in muscle contraction.' Haruo Sugi and Gerald H. Pollack, excerpted from the Preface.

What is meant by the ‘state of water?’ Few would question that water coming out of a household tap is a liquid, but water in an ice cube is something altogether different: it is a solid that floats on tap water (also known as bulk water).