VOLUME-SPECIFIC AMINO-ACID-ANALYSIS - A METHOD FOR Z(A) DETERMINATION

A general method has been developed for determining the number of mole cules per asymmetric unit, Z(a), of a protein crystal. The method, vol ume-specific amino acid analysis, relies on the direct measurement of the number of protein molecules in a crystal as normalized by the crys tal volume. The method is accurate, straightforward to implement and s ensitive enough for application to small (0.002 m3) crystals. Although the procedures described here are specific to proteins, extension to nucleic acid crystals should be possible.