Histochemical studies on calcified tissues

Histochemical methods were used to detect differences in amino acid reactive groups between bone and osteoid, dentine and predentine. Three major differences were found: Predentine and osteoid contained more reactive sulphydryls than their mineralized counterparts. The greatest reaction for this reactive group was obtained at the mineralizing front. Dentine and bone contained a complex between amino and carboxylic acid groups; predentine and osteoid did not have this complex and carboxylic acid residues were less in these tissues. Dentine and bone contained much greater amounts of histidine or a histidine-like component than did predentine and osteoid. It is proposed that these differences are involved in initiation of mineralization.