[Modification of the ligand load and structure of human serum albumin with different methods of isolation]

The influence of isolation procedures on physico-chemical properties of human serum albumin (HSA) has been studied using differential scanning calorimetry and infrared spectroscopy. Fractionation of blood plasma with polyethylene glycol (PEG) followed by ion-exchange chromatography produced healthy donor albumin whose melting thermograms were identical to those of the HSA in non-fractionated plasma. The endotherms of HSA samples isolated by affinity chromatography (AC) and native electrophoresis (EP) are bimodal as distinct from monophasic endotherms of PEG-HSA preparations. The changes in the melting curves result from increased levels of nonesterified fatty acids in AC-HSA samples and modification of the protein secondary structure revealed in EP-HSA samples by IR-spectroscopy. Analysis of HSA melting thermograms in patients with uremia, chronic hepatitis and peritonitis revealed that the PEG method permits to preserve, in the greatest degree, the thermodynamic features of various "pathological" HSA. The experimental results demonstrate the advantage of the PEG technique in isolation of native HSA in the norm and under pathology.