Physical Properties of Amino Acid Solutions

Abstract

There is currently considerable and renewed interest in what may be termed the ‘non-bonding’ interactions which occur between atoms and molecules and much of this interest stems from an appreciation of the role such interactions play in biological systems [1–5]. A significant amount of the work in this area has been performed where the principal objective has been the investigation of relatively simple systems containing small molecules which incorporate some of the molecular features associated with biopolymers. It is not unfair to say that most of our, admittedly sketchy, knowledge of the nature and magnitudes of non-bonding interactions, has been derived from studies on such ‘model’ compounds. The amino acids have not surprisingly attracted considerable interest in this regard and the objective of this chapter is to present a summary of some aspects of the physicochemical behaviour of such molecules in aqueous systems. The approach adopted is largely based upon pictorial and diagrammatic representations rather than the algebraic approach frequently, and often necessarily, used by investigators with a physical chemistry background. One consequence of the decision to use this type of approach is that it is sometimes necessary to oversimplify situations, but this is not uncommon in chemistry. Many of the ideas used here are applicable to solutions containing solutes other than amino acids and occasionally we shall draw on information from other systems if the appropriate information is not available for amino acids.