POLYMERIZATION ON THE ROCKS - NEGATIVELY-CHARGED ALPHA-AMINO-ACIDS

Oligomers of the negatively-charged amino acids, glutamic acid, aspart ic acid, and O-phospho-L-serine are adsorbed by hydroxylapatite and il lite with affinities that increase with oligomer length. In the case o f oligo-glutamic acids adsorbed on hydroxylapatite, addition of an ext ra residue results in an approximately four-fold increase in the stren gth of adsorption. Oligomers much longer than the 7-mer are retained t enaciously by the mineral. Repeated incubation of short oligo-glutamic acids adsorbed on hydroxylapatite or illite with activated monomer le ads to the accumulation of oligomers at least 45 units long. The corre sponding reactions of aspartic acid and O-phospho-L-serine on hyroxyla patite are less effective in generating long oligomers, while illite f ails to accumulate substantial amounts of long oligomers of aspartic a cid or O-phospho-L-serine.