Protein Water Interactions

This book is aimed at understanding which molecular parameters control the thermodynamics, structure, and functions of the protein-water systems. Proteins are one of the most important classes of biological molecules. Water binding (hydration or biological water) plays a crucial role in determining the structure, stability, and functions of proteins. Knowledge of processes occurring upon hydration or dehydration of protein macromolecules is very important in biotechnological and pharmaceutical applications of proteins such as their use as biocatalysts, biosensors, and selective adsorbents. There are essential differences between hydration and bulk water surrounding a protein. This means that a characterisation of the hydration of protein macromolecules requires elucidating the effects of both the protein on water and vice versa. Therefore, a quantitative estimation of the protein and water contributions to the thermodynamic functions of binary protein-water systems is of considerable fundamental importance and practical interest. This book describes the basic principles of a novel methodology to investigate the protein-water interactions. This methodology is based on the analysis of the excess thermodynamic functions of mixing. The thermodynamic properties (volume V, enthalpy H, entropy S, heat capacity Cp, and Gibbs free energy G) of a real binary water-protein system can be expressed in terms of the excess functions. They are the difference between the thermodynamic function of mixing in a real system and the value corresponding to an ideal system at the same temperature, pressure and composition. For an ideal system, all excess functions are zero. Deviations of the excess functions from zero indicate the extent to which the studied binary system is non-ideal due to strong specific interactions between components (ie: hydrogen bonding and charge-charge interactions).

The book is devoted to expanding current views on the phenomena of protein functionality in food systems. Protein functionalities in foods have been the object ofextensive research over the last thirty to forty years and significant progress has been made in understanding the mechanism and factors influencing the functionality of proteins. The functionality of proteins is one of the fastest developing fields in the studies of protein utilization in foods. Currently, a broad spectrum of data related to protein functionality in food systems has been collected, however, much more needs to be known. In this volume, the most important functional properties offood proteins are presented: Protein solubility, water holding capacity and fat binding, emulsifying, foaming, and gelling properties as affected by protein source, environmental factors (pH, temperature, ionic strength) and protein concentration; Relationships between protein conformation, physicochemical properties, and functional properties; Protein functional properties as influenced by various food processing conditions, particularly heat treatment, dehydration, freezing and storage when frozen, extraction and other processes; Effects ofprotein modification on the enhancementofprotein functionality; Utilization ofvarious proteins in improving functional properties in food systems. Those aspects of protein functionality are presented which the author believes to be interesting and most important for protein utilization in food systems. The book is recommended to students and food scientists engaged in food protein research and food industry research, and development scientists. Table ofContents Introduction 1 References 5 Chapter 1 Solubility ofProteins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1. 1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1. 1. 1 Factors Affecting Solubility ofProteins. . . . . . . . . . . . . . . . . . . . . . . .

Proceedings of the 14th Jerusalem Symposium on Quantum Chemistry and Biochemistry, Jerusalem, Israel, April 13-16, 1981

A unified overview of the dynamical properties of water and its unique and diverse role in biological and chemical processes.

This book is aimed at understanding which molecular parameters control the thermodynamics, structure, and functions of the protein-water systems. Proteins are one of the most important classes of biological molecules. Water binding (hydration or biological water) plays a crucial role in determining the structure, stability, and functions of proteins. Knowledge of processes occurring upon hydration or dehydration of protein macromolecules is very important in biotechnological and pharmaceutical applications of proteins such as their use as biocatalysts, biosensors, and selective adsorbents. There are essential differences between hydration and bulk water surrounding a protein. This means that a characterization of the hydration of protein macromolecules requires elucidating the effects of both the protein on water and vice versa. Therefore, a quantitative estimation of the protein and water contributions to the thermodynamic functions of binary protein-water systems is of considerable fundamental importance and practical interest. This book describes the basic principles of a novel methodology to investigate the protein-water interactions. This methodology is based on the analysis of the excess thermodynamic functions of mixing. The thermodynamic properties (volume V, enthalpy H, entropy S, heat capacity Cp, and Gibbs free energy G) of a real binary water-protein system can be expressed in terms of the excess functions. They are the difference between the thermodynamic function of mixing in a real system and the value corresponding to an ideal system at the same temperature, pressure and composition. For an ideal system, all excess functions are zero. Deviations of the excess functions from zero indicate the extent to which the studied binary system is non-ideal due to strong specific interactions between components (i.e., hydrogen bonding and charge-charge interactions).

This work covers advances in the interactions of proteins with their solvent environment and provides fundamental physical information useful for the application of proteins in biotechnology and industrial processes. It discusses in detail structure, dynamic and thermodynamic aspects of protein hydration, as well as proteins in aqueous and organic solvents as they relate to protein function, stability and folding.

This volume is the last in the series comprising "Water-A Comprehensive Treatise. " It was originally planned to combine aqueous solutions of macro molecules and disperse systems in one volume, but largely because of the extensive coverage required by recent developments in aqueous solutions of proteins and synthetic polymers I decided to separate topics dealing with water in disperse systems. The systems treated in the present volume are of a complex nature so that the theoretical frameworks established earlier in Volume 1 and utilized in Volumes 2 and 3 cannot at the present time be applied. On the other hand the systems discussed in Volumes 4 and 5 in particular, border on the many biological and technological areas where important attributes are related to the common factor-water. Included among such diverse problem areas are food processing and preservation, cryopreservation, paper and textile finishing, membrane processes, hemodynamics, etc. It is to be hoped that in days to come some of the results and principles discussed in these five volumes can be applied to improve our understanding of the complex in teractions in medically and industrially important spheres of scientific ac tivity. An age seems to have passed since the concept of creating this treatise was first discussed, and since work began on Volume 1, much has happened in the science of Water; some of the recent developments were highlighted at this year's Gordon Research Conference in Plymouth, N. H.