Amino Acids in Aqueous Solution

In the previous chapter, the focus was mainly on the behavior of ions in solution. The effect of concentration, solvent, as well as pH have been investigated; furthermore, alkali metal ions as well as transition metal ions have been studied. In this chapter, the investigation will be extended from ions to molecules, more specifically toward the behavior of amino acids in solution. Amino acids are the building blocks of proteins, and hence protein structure and reactivity are dependent on the specific properties of the incorporated amino acids. Particularly relevant for the understanding of biological activity, though, is the effect of water on the structure, both geometric and electronic, of amino acids. Especially the amino acids side chains have a strong influence on how the protein behaves in water. Water, in fact, takes part in a wide range of reactions within the cell, and it is, at various amounts, an integral part of all proteins. Moreover, the particular structure of the solvated amino acid is very sensitive to the pH of the solution; this is one reason why pH regulation is important in living organisms [111].