SOLUBILITY, PHASE-TRANSITION, KINETIC RIPENING AND GROWTH-RATES OF PORCINE PANCREATIC ALPHA-AMYLASE ISOENZYMES

Two polymorphic modifications, A and B, of porcine pancreatic a-amylase were grown between 4 and 30-degrees-C. A and B crystals are made up by two isoenzymes so that four crystal varieties (AI, AII, BI, BII) exist. A and B are easily distinguished due to their typical crystal habits but there is no difference between AI and AII or BI and BII respectively at least as concerns their unit cells. crystal habits and solubilities for instance. On the other hand, the growth rates are somewhat different, even if the overall rate determining step is volume diffusion. The transition temperature between A and B polymorphs is 18-degrees-C, A being stable above this temperature. A and B can undergo a phase transition by slightly changing the temperature around the transition point. Kinetic ripening experiments show that ripening can be used for growing larger crystals at the expenses of smaller ones.