Surface Activity of Proteins

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Surface Activity of Proteins Chemical and Physicochemical Modifications edited by Shlomo Magdassi The Hebrew University of Jerusalem Jerusalem, Israel

Start of Citation[PU]Marcel Dekker, Inc.[/PU][DP]1996[/DP]End of Citation

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Library of Congress Cataloging-in-Publication Data Surface activity of proteins : chemical and physicochemical modifications / edited by Shlomo Magdassi. p. cm. Includes index. ISBN 0-8247-9532-6 (hardcover: alk. paper) 1. Protein engineering. 2. Proteins—Surfaces. 3. Proteins— Chemical modification. I. Magdassi, Shlomo. TP248.65.P76S87 1996 660'.63—dc20 96-25981 CIP The publisher offers discounts on this book when ordered in bulk quantities. For more information, write to Special Sales/ Professional Marketing at the address below. This book is printed on acid-free paper. Copyright © 1996 by Marcel Dekker, Inc. All Rights Reserved.

Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming, and recording, or by any information storage and retrieval system, without permission in writing from the publisher. Marcel Dekker, Inc. 270 Madison Avenue, New York, New York 10016

Current printing (last digit): 10 9 8 7 6 5 4 3 2 1 PRINTED IN THE UNITED STATES OF AMERICA

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Preface Proteins are biopolymers that are encountered in many applications, such as food emulsions, hair conditioners, photographic emulsions, and various medical diagnostic products. Many of these applications are frequently based on the unique surface activity of the proteins, which is reflected in functional properties such as foaming, emulsification, and gelling. The proteins are composed of polymeric chains containing many hydrophobic and hydrophilic domains, often giving the molecules an amphipathic structure somewhat similar to that of polymeric surfactants. Because the functional properties of the proteins are strongly dependent on their molecular characteristics this should be taken into account in order to select the proper protein for an application. In general, using a protein in a given application requires a combination of several properties, such as gelling with emulsification, adsorption with steric stabilization, and so forth. Improved functional properties can often result from enhancement of the surface activity of the protein. Alteration of surface activity of proteins can be achieved by various methods, and among them chemical modifications seem to be the most promising. This book deals with the modification of the surface activity of proteins from two points of view: first a description of specific modification methods, such as increasing the negative charges by succinylation, or attachment of surfactant

Start of Citation[PU]Marcel Dekker, Inc.[/PU][DP]1996[/DP]End of Citation

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molecules without formation of covalent bonds, and second evaluation of the implication of the various modifications on the surface activity, using examples of specific systems and applications. The book gathers several approaches to modifying the surface activity of proteins, and therefore it contains both theoretical and practical descriptions. After an introductory chapter describing the basic phenomena related to the behavior of proteins at various interfaces, the following modification methods are reviewed: attachment of hydrophobic groups, increasing the anionic charges, deamidation and phosphorylation, formation of protein–polysaccharide conjugates, and proteolysis and linking of various functional groups by enzymatic reactions. These chapters are followed by a discussion of noncovalent modifications, such as binding of surfactants to proteins and denaturation of globular proteins. Some of these modifications are presented in the last chapter, which focuses on applications of proteins in food products. Other methods, such as attachment of positively charged groups to the protein, are not included in the book, mainly because of the lack of information linking modification to specific surface activity. Some of the modifications discussed here have already been applied in various products. Sometimes they are used unknowingly, for example, in cosmetic products containing both surfactants and proteins. I hope that the scientific information and the description of the possible approaches to altering functional properties and surface activity of proteins presented in this book will be useful to scientists interested in understanding the behavior of proteins at interfaces, as well as to those who wish to find new applications and products based on proteins.

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Contents Preface

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Contributors

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1. Introduction: Surface Activity and Functional Properties of Proteins Shlomo Magdassi and Alexander Kamyshny

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2. Enhanced Hydrophobicity: Formation and Properties of Surface-Active Proteins Shlomo Magdassi and Ofer Toledano

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3. Increased Anionic Charge: Conformational and Functional Properties K. D. Schwenke

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4. Deamidation and Phosphorylation for Food Protein Modification Frederick F. Shih

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5. Preparation and Functional Properties of Protein–Polysaccharide Conjugates Akio Kato

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115

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6. Enzymatic Modification as a Tool for Alteration of Safety and Quality of Food Proteins Gyöngyi Hajós

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7. Denaturation of Globular Proteins in Relation to Their Functional Properties Jacques Lefebvre and Perla Relkin

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8. Protein–Surfactant Interactions Malcolm N. Jones

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9. Factors Affecting Applications of Native and Modified Proteins in Food Products M. E. Mangino and W. James Harper

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Index

323

Start of Citation[PU]Marcel Dekker, Inc.[/PU][DP]1996[/DP]End of Citation