[Complexes of antiparallel telomeric G-quadruplex d(TTAGGG)4 with carboxymethyl tetracationic porphyrins].

Porphyrins comprise a chemical class widely used in drug design. Cationic porphyrins may bind to DNA guanine quadruplexes. We report the parameters of binding of 5,10,15,20-tetrakis(N-carboxymethyl-4-pyridinium)porphyrin (P1) and 5,10,15,20-tetrakis(N-etoxy-carbonylmethyl-4-pyridinium)porphyrin (P2) to antiparallel telomeric G-quadruplex formed by d(TTAGGG)4 sequence (TelQ). The binding constants (K(i)) and the number of binding sites (N(i)) were determined from absorption isotherms generated from absorption spectra of complexes of P1 and P2 with TelQ. Compound P1 demonstrated a high affinity to TelQ (K1 = (40 +/- 6) x 10(6) M(-1), N1 = 1; K2 = (5.4 +/- 0.4) x 10(6) M(-1), N = 2). In contrast, the binding constants of P2-TelQ complexes (K1 = (3.1 +/- 0.2) x 10(6) M(-1), N1 = 1; K2 = (1.2 +/- 0.2) x x 10(6) M(-1), N2 = 2) were one order of magnitude smaller than the respective values for P2-TelQ complexes. Measurements of quantum yield and fluorescence lifetime of drug-TelQ complexes revealed two types of binding sites for P1 and P2 on the quadruplex oligonucleotide. The 'strong' complexes can result from interaction of the porphyrinswith TTA loops whereas the weaker complexes are formed with G-quartets. The altered TelQ conformation detected by circular dichroism spectra of P1-TelQ complexes can be explained by a disruption of a G-quartet. We conclude that peripheral carboxy groups contribute tothe high affinity of P1 for the antiparallel telomeric G-quadruplex.

Synthesis of water-soluble porphyrin with tyrosine fragments and study of its interaction with S-protein of SARS-CoV-2.

The multistage purposeful synthesis of 5,15-bis(4'-l-N-tyrosinylamidophenyl)-10,20-bis(N-methylpyridin-3'-yl)porphine diiodide was carried out, and the optimum synthesis conditions were determined. 5,15-Bis(4'-nitrophenyl)-10,20-bis(pyridin-3'-yl)porphine served as the starting porphyrin. The structure, individual character, and purity of the target compound were proved by electron spectroscopy, 1H NMR spectroscopy, mass spectrometry (MALDI TOF), and TLC. Specific features of the interaction of the synthesized porphyrin with S-protein of SARS-CoV-2 were studied using spectral and thermochemical methods, including conditions of photoirradiation. The photoirradiation of the synthesized porphyrin in a complex with the SARS-CoV-2 S-protein can result in the partial oxidation of amino acid residues of the protein and distort its primary and secondary structures. The photoirradiation of the S-protein complex with the porphyrin decreases its thermal resistance to melting by 15 °C compared to the free S-protein and causes porphyrin release.

Fluorescence properties and quantum-chemical modeling of tert-butyl-substituted porphyrazines: Structural and ionization effect.

Synthesis and identification of tetrakis-[5,6-bis(4-tert-butylphenyl)pyrazino] porphyrazine, tetra-(4-tert-butyl)phthalocyanine and octakis-(4-tert-butylphenyl)porphyrazine were carried out. Spectrophotometric method was used to study the spectral, acidic and fluorescence properties of the synthesized compounds. It was determined that the synthesized tert-butyl-substituted porphyrazines exhibit a high sensitivity of fluorescence to the molecule ionization. To understand the features of the spectral properties the geometry optimization and an analysis of energy levels and localization of highest occupied and lowest unoccupied molecular orbitals of the studied compounds were performed on the basis of density functional theory with the BP86 functional and the def2-TZVP basis set. The effect of substituents in molecular fragments of the macrocycle on the acidic and electro-optical properties of the studied compounds is revealed. Materials with pH-tunable fluorescence were designed.

[Nucleic acids as a basis for creating biosensors]. / Nukleonovye kisloty kak osnova dlia sozdaniia biosensorov.

Here we present a brief conception of biosensors. Structural peculiarities and properties of single- and double-stranded nucleic acids that are to be taken into account when creating biosensors on the basis of these biomolecules are considered. On the example of two biologically active compounds a possibility is shown for constructing biosensors on the basis of liquid-crystalline dispersions of low molecular mass DNA and on the basis of liquid-crystalline DNA dispersions immobilized due to their inclusion into the synthetic polymeric matrix.

The computational and experimental investigations of photophysical and spectroscopic properties of BF2 dipyrromethene complexes.

The electronic excited states of BF2 dipyrromethene (2BrDPM, DPMI, DPMII, PM567 and 4PhDPM) complexes were investigated using the extended multi-configuration quasi-degenerate at the second order of perturbation theory (XMCQDPT2) and the second-order approximate coupled-cluster (CC2) methods. The excitation energies calculated by CC2 are significantly overestimated by 0.42-0.59 eV because of the substantial contributions of double excitation levels to excited states (>10%). However, the calculated XMCQDPT2 excitation energies agree well with experimental ones within the accuracy 0.11-0.20eV. The very low lasing efficiency (7.8-8.4%) of 4PhDPM compound was explained by the T1→T4 and T1→T5 reabsorptions at XMCQDPT2 level of theory. The molecular photonics of pyrromethenes are studied using a combination of the first-principle and semi-empirical calculations. The main mechanism for the deactivation of the energy of the first singlet excited electronic state is the radiative electronic transition for DPMI, DPMII, PM567 and 4PhDPM compounds. Also, the main mechanism for the quenching of fluorescence in considered complexes (except DPMII compound) is the internal conversion. The processes of the internal conversion and intersystem crossing compete with each other in DPMII compound. The measured and calculated fluorescence quantum yields agree well for all considered molecules.