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Enhanced binding and conformational selectivity in affinity capillary electrophoresis using a water‐soluble resorcin[4]arene as intrinsic buffer and electrokinetic host
Author(s) -
Samson Sheeba,
BritzMcKibbin Philip
Publication year - 2006
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.200500583
Subject(s) - chemistry , capillary electrophoresis , electrokinetic phenomena , selectivity , buffer (optical fiber) , electrophoresis , micellar electrokinetic chromatography , buffer solution , electrolyte , hydrophobic effect , enthalpy , chromatography , analytical chemistry (journal) , organic chemistry , telecommunications , physics , electrode , computer science , catalysis , quantum mechanics
Affinity capillary electrophoresis (ACE) is a widely used technique for quantifying non‐covalent molecular interactions that is dependent on the specific buffer conditions selected. In this study, dynamic 1:1 host‐guest inclusion complexation involving a charged resorcin[4]arene with a group of neutral corticosteroids was examined by ACE, where the macrocycle serves as both an intrinsic buffer and electrokinetic host. It was determined that over a 200% enhancement in the apparent binding constant ( K B ) was realized by ACE when using the host as an intrinsic buffer at pH 7.5 relative to an extrinsic sodium phosphate buffer system, which was also confirmed by 1 H‐NMR experiments. This report also revealed improved selectivity mediated by the discrete conformational properties of the complex among similar corticosteroid guests, as reflected by the complex mobility (μ ep, AC ) or the relative change in complexation‐induced mobility (1–μ ep, AC /μ ep, C ). This latter property is a unique feature of ACE reflective of hydrodynamic size selectivity involving bulky guests or substrates. 1 H‐NMR and computer molecular modeling provided complementary information regarding the relative orientation, conformation and overall molecular area of the complex. The coupling of thermodynamic ( K B ) and electrokinetic (μ ep, AC ) factors associated with complex formation in buffered solutions that minimize the effects of extrinsic electrolytes serves to enhance enthalpy‐driven molecular recognition processes by ACE.