Conceptual Construction of Isoelectric Point Based on the“Total”Dissociation Model
ZHU Liang-Liang1, XIAO Ling2**
1. School of Life Science,Anqing Normal University,Anqing 246311,China; 2. School of Resources and Environment,Anqing Normal University,Anqing 246311,China
Abstract The isoelectric point(pI)is a key physicochemical parameter for zwitterions;however,the current teaching reference books present an oversimplified conceptualization of pI that fails to accurately capture its thermodynamic essence and lacks logical relation to established computational approaches.To address these conceptual limitations,this study redefines pI as the solution pH at which the zwitterionic species with a net charge of zero attains maximum relative concentration.Upon this rigorous definition,we propose a comprehensive framework through development of a “total” dissociation equilibrium model.This model not only derives the mathematical formulation for amino acid pI calculation but also provides a systematic analysis of their charge distribution patterns under varying pH conditions.Our derivation process requires no advanced mathematical skills,yet yields enhanced precision compared to the conventional method.This pedagogical advancement enables students to achieve deeper comprehension of zwitterion ionization behavior.In summary,this paper presents a novel perspective on understanding the concept of pI,and provides a rigorous proof method for the calculation formula.The related analyses and discussions offer valuable references for both theoretical and experimental instruction concerning pI.
ZHU Liang-Liang, XIAO Ling. Conceptual Construction of Isoelectric Point Based on the“Total”Dissociation Model[J]. Chinese Journal of Chemical Education, 2025, 46(12): 116-122.
