Techniques in Protein Chemistry [antikvár]

PREFACE In writing this book I have been guided by the needs of biochemist s who have had limited practical experience of the chemistry of proteins and who may wish to try their hand at a tentative characterization and structural examination of the protein or peptide part of their particular experimental system. Some technical aspects of the subject have become rather complicated by numerous modifications in procedure and at times, it is difficult even for the specialist worker to decide on the respective merits of all the variants. My aim therefore has been to compile a practical handbook in which established analytical methods are discussed in detail, recent promising techniques are touched on briefly, and in which theoretical considerations are introduced only where they have a direct bearing on practice. A recurring difficulty that has to be faced by all who work with proteins is the lack of a simple criterion of purity that might be applied to purified preparations. Crystallinity has long been abandoned as a criterion of homogeneity and quantitative solubility tests have been applied in very few cases. The minimum requirement generally acceptable is evidence of homogeneity from data provided by column chromatography, electrophoresis under different conditions of pH, and sedimentation in the ultracentrifuge. Two chapters in this book are devoted to column chromatography and electrophoresis of proteins. A discussion of the ultracentrifuge is not included since the information is available in special operational manuals. In the interests of brevity accounts of the more complicated physical equipment, e.g. counter-current distribution apparatus, are also omitted. The final criterion for a single molecular species is the demonstration of a unique amino acid sequence and hence the major part of this book is concerned with methods for sequence determination, selective cleavage of peptide chains, fractionation