Exploration of pH-dependent behavior of the anion receptor pocket of subdomain IIA of HSA: Determination of effective pocket charge using the Debye-Hückel limiting law

Priyanka Bolel, Shubhashis Datta, Niharendu Mahapatra, Mintu Halder

Research output: Contribution to journalArticlepeer-review

20 Scopus citations

Abstract

Protein-ligand electrostatic interaction can be looked upon as ion receptor-ligand interaction, and the binding cavity of protein can be either an anion or cation receptor depending on the charge of the guest. Here we focus on the exploration of pH-modulated binding of a number of anionic ligands, specific to the subdomain IIA cavity of HSA, such as carmoisine, tartrazine, cochineal red, and warfarin. The logarithm of the binding constant is found to vary linearly with the square-root of ionic strength, indicating applicability of the Debye-Hückel limiting law to protein-ligand electrostatic binding equilibrium, and concludes that the subdomain IIA cavity is an anion receptor. The present approach is very unique that one can calculate the effective charge of the protein-based anion receptor pocket, and the calculated charge has been found to vary between +1 and +3 depending on the pH and ligand itself. The study also indicates that in such cases of specific ligand binding the pocket charge rather than the overall or surface charge of the macromolecule seems to have a paramount role in determining the strength of interaction. For the first time, it is demonstrated that the Debye-Hückel interionic interaction model can be successfully applied to understand the protein-based receptor-ligand electrostatic interaction in general.

Original languageEnglish
Pages (from-to)26-36
Number of pages11
JournalJournal of Physical Chemistry B
Volume118
Issue number1
DOIs
StatePublished - 9 Jan 2014
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

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