Alexey V. Solomonov

Spectroscopic Studies of the Supramolecular Interactions Between Uracil and 5-Hydroxy-6-Methyluracil with Bovine Serum Albumin and its Bilirubin Complex

Using fluorescence and absorption spectroscopy the interaction of bovine serum albumin and its bilirubin complex with uracil and 5-hydroxy-6-methyluracil in phosphate buffer at pH 7.4 was investigated. The parameters of forming intermolecular complexes (binding constants, quenching rate constants, the radius of the quenching sphere and etc.) were determined. The interaction between serum albumin and uracils is carried out by the static quenching of protein fluorescence and has predominantly hydrophobic character. Using synchronous fluorescence spectroscopy the influence of uracil and 5-hydroxy-6-methyluracil on the conformational changes of the protein molecule was studied. Uracils effectively binds to bilirubin-albumin complex compared to free protein, which is caused by the interaction with tetrapyrrolic pigment in macromolecular complex. Molecular docking calculations also being presented.

Recent Advances of Individual BODIPY and BODIPY-Based Functional Materials in Medical Diagnostics and Treatment

BACKGROUND The group of fluorophores on boron dipyrrin platform (4,4- difluoro-4-bora3a,4a-diaza-s-indacene, also known as BODIPY) has attracted much attention in the field of molecular sensorics, including sensing of biomolecules and bioprocesses. Structural diversity of existing BODIPY with ample opportunities of directed modification of compounds makes this class of fluorophores attractive for medical and biological purposes. The recent progress in the design and functionalization of BODIPY allows using them for modification of drug micro- and nanocarriers in order to improve their therapeutic effect in cancer treatment. At the same time, integration of BODIPY into drug carriers provides the possibility of in vitro and in vivo real time imaging of used drug carriers. The high fluorescent intensity and low toxicity of BODIPY granted for conjugation with different biomolecules. RESULTS The present review focuses on the recent advances for application of individual BODIPY in medical diagnostics, antimicrobial activity, as well as establishing the role of BODIPY in labeling of biomolecules (e.g. proteins, hormones and DNA). Also the review highlights the potential of BODIPY in functionalization of drug micro- and nanocarriers in order to achieve better therapeutic efficiency compared with non-modified materials. The advantages derived from the use of BODIPY for preparation and modification of drug carriers are critically evaluated and potential for future challenges, especially concerning the design of innovative multi-functional BODIPY-based nanocarriers, is discussed in detail using representative examples from literature. CONCLUSION Our objective was to show that BODIPY are powerful tools for bioimaging, labeling of biomolecules and construction of new multifunctional drug carriers.

Kinetics of oxidation of bilirubin and its protein complex by hydrogen peroxide in aqueous solutions

A comparative study of oxidation reactions of bilirubin and its complex with albumin was carried out in aqueous solutions under the action of hydrogen peroxide and molecular oxygen at different pH values. Free radical oxidation of the pigment in both free and bound forms at pH 7.4 was shown not to lead to the formation of biliverdin, but to be associated with the decomposition of the tetrapyrrole chromophore into monopyrrolic products. The effective and true rate constants of the reactions under study were determined. It was assumed that one possible mechanism of the oxidation reaction is associated with the interaction of peroxyl radicals and protons of the NH groups of bilirubin molecules at the limiting stage with the formation of a highly reactive radical intermediate. The binding of bilirubin with albumin was found to result in a considerable reduction in the rate of the oxidation reaction associated with the kinetic manifestation of the protein protection effect. It was found that the autoxidation of bilirubin by molecular oxygen with the formation of biliverdin at the intermediate stage can be observed with an increase in the pH of solutions.

The Interaction of BODIPY with bovine serum albumin and its bilirubin complex

Using fluorescence and electronic spectroscopy the interaction of boron-dipyrromethene complex (BODIPY) with bovine serum albumin (BSA) and its bilirubin macromolecular complex (BR·BSA) in aqueous solution was investigated. The interaction of BODIPY is carried out by the static quenching of protein fluorescence and is predominantly hydrophobic and electrostatic in nature. The values of the binding constants were (61.2 ± 2.8) · 103 and (6.51 ± 0.3) · 103 M−1. The interaction of BODIPY with proteins leads to the observed hypso- and bathochromic shift in BODIPY absorption band. Forster resonance energy transfer theory allowed of determing the donor-ligand distance, which were 2.88 and 2.46 nm for BSA and BR·BSA, respectively. Using synchronous fluorescence spectroscopy it was possible to reveal features of BODIPY influence on conformational changes in protein molecules. It was established that BODIPY more effectively interacts with BSA compared to BR·BSA.

Micellar coordination clusters based on nonionic surfactant Triton Х-114: stability, possibilities of modification, and peculiarities of reactions with cyclodextrins

New micellar coordination clusters (MCCs) were prepared by the introduction of a hydrophobic chelator onto the interface of nonionic surfactant Triton X-114 followed by “crosslinking” of the structures by metal ions. Their resistance to changes in ionic strength, pH of the solution, and temperature was investigated. Regularities in the interaction of MCCs with α-, β-, and γ-cyclodextrins (CD) were revealed. It was shown that the variation of the type and concentration of CD allowed one to control the mechanism of MCC synthesis and to affect their stability. The involvement of molecular modeling (molecular docking) made possible to elucidate the most energetically favorable structures of complexes of CD with components of MCCs.

Molecular complexation of uracil with bovine serum albumin and its complex with bilirubin studied by spectroscopic methods

The interactions of uracil (U) with bovine serum albumin (BSA) and its complex with bilirubin (BR·BSA) in phosphate buffer at pH 7.4 were studied by fluorescence and electronic spectroscopy. The parameters of the resulting intermolecular complexes (binding constants, quenching rate constants, the radius of the quenching sphere-of-action, etc.) were determined. The interaction of BSA with U occurs through a static quenching of protein fluorescence and has a predominantly hydrophobic character. The effect of U on the conformational changes of the protein molecule was analyzed by synchronous fluorescence spectroscopy. Uracil binds to BR·BSA more efficiently than to the free protein due to the interaction of U with the tetrapyrrole pigment incorporated in the macromolecular complex.