ИСТИНА

Serum albumin (SA) is the most abundant protein in blood plasma (BP). The main function of SA in blood circulatory is to transport different ligands such as fatty acids, drugs, metabolites, etc. and strongly depends on the protein conformation.
Optical methods are usually used to characterize SA conformational changes in solutions under different conditions (addition of chemicals, varying temperature, pH), and the results of these studies are extrapolated to human BP. Only a few works are devoted to investigation of SA conformation in BP to indicate pathological processes. The serious limitation of investigation of human BP via optical methods is to separate SA optical response from that of other components. Here we combine the advantages of optical methods with separation technique (capillary electrophoresis, CE). CE is based on the difference between mobilities of the components in the electric field, which depend on the charge to mass ratio. CE setups are usually equipped with a single type of detector, e.g., spectrophotometric. In this work we expanded the opportunities of CE by using simultaneously two types of optical detectors: optical density measurements at 254 nm (OD- channel) and laser induced fluorescence spectra with excitation at 405 nm and registration in the 450 – 750 nm range (LIF-channel). Here we investigate model solutions of bovine serum albumin (BSA) as well as human BP. The comparison of signals from OD- and LIF-channels confirms that BSA and human serum albumin in BP have a fluorescence band centered at 525 nm that can be excited at 405 nm. Though the origin of this 405 nm/525 nm band remains debatable, we suppose that it is due to the interactions between aromatic residues which lead to formation of new low energy excited states. We showed that the migration time of SA as well as the shape of the 405 nm/525 nm fluorescence band strongly depends on the bound ligands that allows one to use CE with OD- and LIF-channels for diagnostics of pathology.