Structural Changes in Human Serum Albumin According to the Data on the Phosphorescence Kinetics of a Luminescent Probe — Eosin

Abstract

The influence of the human serum albumin (HSA) denaturation by a surface-active substance (sodium dodecyl sulfate (SDS)) on the phosphorescence of a luminescent probe (eosin) has been investigated. The dependences of the eosin-phosphorescence intensity on the SDS concentration were determined at different pH levels of an HSA solution. It has been shown that at SDS concentrations lower than the critical concentration necessary for micelle formation, the hydrophobic interactions of eosin with the protein influence the deactivation of the eosin triplet states.Keywords: protein, phosphorescence at room temperature, human serum albumin, surface-active substance, sodium dodecyl sulfate, micelle, protein denaturation, luminescent probe. Introduction.Structural changes in proteins can be determined by different methods, such as the methods of x-ray structural analysis [1], nuclear magnetic resonance [2], laser-correlation spectroscopy of dynamic light scattering [3], luminescence [4], etc. Fluorescence methods allow one to determine the polarity of the chromophore microsurrounding and the rate of rotational diffusion of a protein and its conformational mobility [5]. In [6,7], the structural dynamics of proteins was determined by the phosphorescence of their chromophoric groups (tryptophanyl) at room temperature. However, the number of chromophoric groups possessing phosphorescence is limited, which generates a need for the development of methods that would allow one to investigate the structural changes in proteins with the use of luminescent probes related to them. For example, in [8], in investigating the phosphorescence decay kinetics of isothiocyanate derivatives of eosin and erythrosin, related to proteins, the accessibility of the active centers of metalloenzymes was detected and the possibility of investigating the diffusion collisions of proteins in solutions was demonstrated. In [9], the influence of the molecular dynamics of proteins on the photoinduced electron transfer in the eosin-myoglobin complex has been revealed. Thus, the method of investigating the structure of proteins and the dynamics of its change by the phosphorescence of luminescent probes related to them holds much promise.In the present work, a method is proposed for control of the structural transformation of a protein by the changes in its absorption and fluorescence spectra and the changes in the intensity and lifetime of phosphorescence of a luminescent probe related to it. We investigated the deactivation of the triplet states of a luminescent probe caused by changes in the structure of a protein under the action of a surface-active substance present in concentrations critical for the micelle formation. The importance of investigating the action of a surface-active substance on the structure of a protein is explained by the fact that many biological and pharmaceutical systems contain proteins and surface-active substances [10]. Such investigations allows one, on the one hand, to obtain data on the changes in the structure of protein compoun...

Luminescent spectral characteristics of eosin in solutions of human serum albumin when denatured by treatment with sodium dodecyl sulfate

“…Thirdly, it affects blood viscosity, which is extremely important for maintaining a normal blood pressure level. Fourthly, it serves as a carrier for hormones, lipids, mineral substances, and drugs.Various optical methods are used to detect structural conformational changes in protein molecules, such as laser correlation spectroscopy of dynamically scattered light [2-4], Raman spectroscopy [5], luminescent analysis methods [6][7][8][9]. In this work, to study the structure of HSA and the dynamics of its conformational rearrangements during denaturing when treated with SDS as a function of the solution pH, we used the luminescent spectral characteristics of the luminescent probe eosin in a buffered solution of the protein.…”

Interglobular Diffusion of an Energy Donor in Triplet-Triplet Energy Transfer in Proteins

“…In [25], it is shown that eosin also binds with bovine serum albumin. On the basis of spectral and kinetic studies [13], we found that almost all eosin is gathered at protein globules when HSA concentration in a water solution reaches HSA = 1 mg/mL. By changing the eosin concentration, it was obtained that the optimal concentration of eosin in HSA for the registration of prolonged luminescence is 4 ⋅ 10 −6 M.…”

“…This feature allows one to use the T-T energy transfer between donors and acceptors bound to a human serum albumin (HSA) to determine minor structural variations in proteins [12]. The phosphorescence of a probe, that is, an eosin bound to HSA macromolecules, turned to be sensitive to pH variations in protein solutions [13] and to the presence of heavy metal ions in proteins. Quenching of the eosin phosphorescence in the presence of heavy metal ions is used thus helping us determine the presence of heavy metals in human serum albumin [14].…”

Modeling of the kinetics of pyrene-bromide phosphorescence in aqueous-micellar media

“…Pyrene bromide was photoexcited into the absorption band maximum. The lifetime of the pyrene bromide triplet state was determined using a specially developed pulsed spectrofluorimeter [19]. Three sections can be seen in the curve showing the dependence of the phosphorescence intensity on the solution photoirradiation time.…”