The titration constants of some amides and dipeptides in relation to alcohol and formaldehyde titrations of amino-N

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Abstract
Titration constants at 25[degree] were detd. for d-glutamine, d-isoglutamine, l-isoasparagine, d-glutaminyl-glycine, d-glutaminyl-d-glutamic acid, and d-alanyl-l-proline, and re-detd. for d-tyrosyl-d-arginine and glycyl-l-proline. Factors influencing the magnitude of the respective [rho]K[image] are discussed, [alpha]-amides and [alpha]-peptides possess constants characteristically different from their [beta]- or [gamma]-analogues. In certain peptides the constants attributable to the amino group are unusually low, and the influence of this fact on the titrimetric estimation of biologic amino-N and on the study of peptidase action, is discussed. Advantages attending the use of iso-glutamine as a buffer in peptidase studies are outlined, and the necessary data as to the composition and stability of the buffer mixtures presented.