Effect of an inhalation anesthetic on the viscosity of aqueous bovine serum albumin solutions

Physico-chemical characterization of bovine serum albumin in solution and as deposited on surfaces

The interactions between proteins and solid surfaces are important for the formation of biocompatible materials. In this study, the physicochemical properties of Bovin serum albumin (BSA) in solution and on a solid surface were studied. The zeta potential and number of uncompensated charges on BSA surfaces were determined from electrophoretic mobility measurements. The dynamic viscosity was also measured to determine BSA conformations in solution, and the data were converted to the effective length L(ef) of the BSA molecule. The length of a BSA molecule was measured to be 8.3 nm in the compact state (N form at pH 4-9) and 26.7 nm in the extended state (F-form). This study demonstrates that the relationship between the hydrodynamic radius, dynamic viscosity and electrophoretic mobility can provide information about the shape and conformation of biopolymer in solution. The contact angle measurements and deposition of fluorescent latex particles were used to characterise BSA monolayers on a mica surface, which were produced by controlled adsorption under diffusion transport. The results suggest that the distribution of charge across a BSA molecule is heterogeneous as evidenced by the presence of positive and negative patches. The maximum contact angle was observed under conditions in which both BSA and mica were oppositely charged. A higher positive zeta potential of BSA was observed to correlate with a higher contact angle. However, at a higher negative zeta potential, BSA exhibited a lower binding affinity. The charge distribution across BSA monolayers was also studied via the colloidal deposition method using negatively charged fluorescent latex particles. Unexpectedly, the fluorescent latex particles adsorbed onto BSA monolayers, even when the effective zeta potential of BSA was negative. This phenomenon may originate from the heterogeneous charge distribution across BSA molecules.

Albumin binds self-assembling dyes as specific polymolecular ligands

Self-assembling dyes with a structure related to Congo red (e.g. Evans blue) form polymolecular complexes with albumin. The dyes, which are lacking a self-assembling property (Trypan blue, ANS) bind as single molecules. The supramolecular character of dye ligands bound to albumin was demonstrated by indicating the complexation of dye molecules outnumbering the binding sites in albumin and by measuring the hydrodynamic radius of albumin which is growing upon complexation of self-assembling dye in contrast to dyes lacking this property. The self-assembled character of Congo red was also proved using it as a carrier introducing to albumin the intercalated nonbonding foreign compounds. Supramolecular, ordered character of the dye in the complex with albumin was also revealed by finding that self-assembling dyes become chiral upon complexation. Congo red complexation makes albumin less resistant to low pH as concluded from the facilitated N-F transition, observed in studies based on the measurement of hydrodynamic radius. This particular interference with protein stability and the specific changes in digestion resulted from binding of Congo red suggest that the self-assembled dye penetrates the central crevice of albumin.