Interactions between dansyl amino acids and human serum albumin using high-performance liquid chromatography: mobile-phase pH and temperature considerations.
The reversed-phase liquid chromatography (RPLC) retention mechanism of a series of dansyl amino acids was investigated over a wide range of mobile-phase pH and column temperatures using human serum albumin (HSA) as a chiral stationary phase. Thermodynamic constants for the transfer of a solute from the mobile to the HSA stationary phases were determined. Different van't Hoff plot shapes were observed with different mobile-phase pH values, indicating a change in the retention mechanism. Enthalpy-entropy compensation revealed that the solute retention mechanism was independent of the compound molecular structure, the same at four pH values (5.5, 6, 6.5, and 8), but changed at pH = 7 and 7.5. Differential scanning calorimetry was used to show phase transition in the HSA stationary phase at pH = 7 and 7.5. A new theory was presented to explain that the HSA protein structure balance between a disordered and an ordered solid-like state. Variations of column temperature and mobile-phase pH tend to cause this phase transition between these two states, explaining the observed thermodynamic constant variations with pH and temperature.
Peyrin
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E
Laboratoire de Chimie Analytique, Faculté de Médecine et Pharmacie, Besancon, France.
Guillaume
Y C
YC
Guinchard
C
C
D000596:Amino Acids / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D003619:Dansyl Compounds / Q000737:chemistry*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008432:Mathematical Computing; D008958:Models, Molecular; D012709:Serum Albumin / Q000737:chemistry*; D013696:Temperature; D013816:Thermodynamics
D000596:Amino Acids; D003619:Dansyl Compounds; D012709:Serum Albumin