Structure characterization of human serum proteins in solution and dry state

The present report describes application of advanced analytical methods to establish correlation between changes in human serum proteins of patients with coronary atherosclerosis (protein metabolism) before and after moderate beer consumption. Intrinsic fluorescence, circular dichroism (CD), differential scanning calorimetry and hydrophobicity (So) were used to study human serum proteins. Globulin and albumin from human serum (HSG and HSA, respectively) were denatured with 8 m urea as the maximal concentration. The results obtained provided evidence of differences in their secondary and tertiary structures. The thermal denaturation of HSA and HSG expressed in temperature of denaturation (Td, degrees C), enthalpy (DeltaH, kcal/mol) and entropy (DeltaS kcal/mol K) showed qualitative changes in these protein fractions, which were characterized and compared with fluorescence and CD. Number of hydrogen bonds (n) ruptured during this process was calculated from these thermodynamic parameters and then used for determination of the degree of denaturation (%D). Unfolding of HSA and HSG fractions is a result of promoted interactions between exposed functional groups, which involve conformational changes of alpha-helix, beta-sheet and aperiodic structure. Here evidence is provided that the loosening of the human serum protein structure takes place primarily in various concentrations of urea before and after beer consumption (BC). Differences in the fluorescence behavior of the proteins are attributed to disruption of the structure of proteins by denaturants as well as by the change in their compactability as a result of ethanol consumption. In summary, thermal denaturation parameters, fluorescence, So and the content of secondary structure have shown that HSG is more stable fraction than HSA.

Beer consumption and changes in stability of human serum proteins

The aim of this study was to evaluate the influence of beer consumption (BC) on the functional and structural properties of human serum proteins (HSP). Thirty-eight volunteers (after coronary bypass) were divided into two groups: experimental (EG) and control (CG). Nineteen volunteers of the EG consumed 330 mL per day of beer (about 20 g of alcohol) for 30 consecutive days. The CG volunteers consumed mineral water instead of beer. Blood samples were collected from EG and CG patients before and after the experiment. Albumin (Alb), globulin (Glo), and methanol-precipitable proteins (MPP) from human serum were denatured with 8 M urea. Fluorescence and electrophoresis were employed in order to elucidate urea-induced conformational changes and structural behavior of proteins. The measured fluorescence emission spectra were used to estimate the stability of native and denatured protein fractions before and after BC. It was found that before BC the fractions most stable to urea denaturation were Glo, Alb, and MPP fractions. After BC in most of the beer-consuming patients (EG) some changes in native and denatured protein fractions were detected: a tendency to lower stability and minor structural deviations. These qualitative changes were more profound in MPP than in Alb and Glo. Thus, Glo is more resistible to alcohol influence than Alb, which in turn is more resistible than MPP. No serum protein changes were detected in patients of CG.

Intrinsic tryptophan fluorescence of human serum proteins and related conformational changes

The unfolding of human serum proteins (HSP) was studied by measuring the intrinsic fluorescence intensity at a wavelength of excitation corresponding to tryptophan's or typosine's fluorescence and surface hydrophobicity. The maxima emission wavelengths (lambdamax) of human serum albumin (HSA) and human serum globulin (HSG) before beer consumption (BC) were 336.0 and 337.0 nm and after BC shifted to 335.0 and 334.0 nm, respectively. The surface hydrophobicity slightly increased after BC. In a solution of 8 M urea the lambdamax of BSA shifted to 346.4 and that of BSG to 342.5 nm. In contrast, in the same solution but after BC the lambdamax positions of HSA and HSG shifted to 355.9 and 357.7 nm, respectively. A decrease in fluorescence intensity, a shift in the maximum of emission, and an increase in surface hydrophobicity which reflected unfolding of proteins were observed. Here we provide evidence that the loosening of the HSP structure takes place primarily in various concentrations of urea before and after beer consumption. Differences in the fluorescence behavior of the proteins are attributed to disruption of the structure of proteins by denaturants as well as by the change in their compactability as a result of ethanol consumption.