Establishment of the --Linkage

A number of the methods which depend on pK-values, including paper electrophoresis and ion-exchange chromatography, provide clear results for the derivatives of neutral a-amino acids. For derivatives of P-and y-amino acids and amines this is not necessarily the case. The lability towards acid is also indicative, but it is not easy to exploit it in quantitative measurements. 

It can be said generally that differentiation is straightforward when both the a- and the y-isomers are available. When only one isomer is available, definite proof of structure can be provided only by one of the unambiguous methods mentioned above. A review concerned with identification of y-glutamyl derivatives has been published 247). 

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