In this paper it is pointed out that there is a convergence temperature for the enthalpy change associated with the dissolution process into water of four solid cz-amino acids : glycine, DL-alpha-alanine, DL-alpha-aminobutyric acid and DL-alpha-norvaline. It is important that the value of the convergence temperature for alpha-amino acids, T-H* = 91.2 +/- 6.3 degrees C is very close to that determined for the denaturation of small globular proteins, T-H* = 100 +/- 6 degrees C. This result is analysed thoroughly in order to obtain information about the energetics of the protein denaturation process. The analysis points out that there is an energy penalty, due to the dehydration and burial of polar groups, that tends to counterbalance the energy gain due to the formation of polar and dispersive interactions in the close-packed interior of globular proteins.