Towards understanding non-equivalence of α and β subunits within human hemoglobin in conformational relaxation and molecular oxygen rebinding.

Picosecond to millisecond laser time-resolved transient absorption spectroscopy was used to study molecular oxygen (O) rebinding and conformational relaxation following O photodissociation in the α and β subunits within human hemoglobin in the quaternary R-like structure. Oxy-cyanomet valency hybrids, α(Fe-O)β(Fe-CN) and α(Fe-CN)β(Fe-O), were used as models for oxygenated R-state hemoglobin. An extended kinetic model for geminate O rebinding in the ferrous hemoglobin subunits, ligand migration between the primary and secondary docking site(s), and nonexponential tertiary relaxation within the R quaternary structure, was introduced and discussed.

Photooxidation of herbicide amitrole in the presence of fulvic acid.

Fulvic acid (Henan ChangSheng Corporation) photoinduced degradation of non-UVA-absorbing herbicide amitrole (3-amino-1,2,4-triazole, AMT) as a way for its removal from polluted water was investigated in details. It was shown that the main primary species generated by fulvic acid under UVA radiation, triplet state and hydrated electron, are not directly involved in the herbicide degradation. AMT decays in reactions with secondary intermediates, reactive oxygen species, formed in reactions of the primary ones with dissolved oxygen.

Molecular oxygen migration through the xenon docking sites of human hemoglobin in the R-state.

A nanosecond laser flash-photolysis technique was used to study bimolecular and geminate molecular oxygen (O2) rebinding to tetrameric human hemoglobin and its isolated α and β chains in buffer solutions equilibrated with 1atm of air and up to 25atm of xenon. Xenon binding to the isolated α chains and to the α subunits within tetrameric hemoglobin was found to cause a decrease in the efficiency of O2 escape by a factor of ~1.30 and 3.

Photophysical properties and singlet oxygen generation efficiencies of water-soluble fullerene nanoparticles.

As various fullerene derivatives have been developed, it is necessary to explore their photophysical properties for potential use in photoelectronics and medicine. Here, we address the photophysical properties of newly synthesized water-soluble fullerene-based nanoparticles and polyhydroxylated fullerene as a representative water-soluble fullerene derivative. They show broad emission band arising from a wide-range of excitation energies.

Photosensitized singlet oxygen luminescence from the protein matrix of Zn-substituted myoglobin.

A nanosecond laser near-infrared spectrometer was used to study singlet oxygen ((1)O2) emission in a protein matrix. Myoglobin in which the intact heme is substituted by Zn-protoporphyrin IX (ZnPP) was employed. Every collision of ground state molecular oxygen with ZnPP in the excited triplet state results in (1)O2 generation within the protein matrix.

Does photodissociation of molecular oxygen from myoglobin and hemoglobin yield singlet oxygen?

Time-resolved luminescence measurements in the near-infrared region indicate that photodissociation of molecular oxygen from myoglobin and hemoglobin does not produce detectable quantities of singlet oxygen. A simple and highly sensitive method of luminescence quantification is developed and used to determine the upper limit for the quantum yield of singlet oxygen production. The proposed method was preliminarily evaluated using model data sets and confirmed with experimental data for aqueous solutions of 5,10,15,20-tetrakis(4-N-methylpyridyl) porphyrin.

Spontaneous emission of singlet oxygen near dielectric nano-objects and radiative diagnostics of bio-objects.

We investigate modifications of a spontaneous emission rate near the surface of the hemoglobin-like dielectric structure in the long-wavelength limit. We demonstrate that notwithstanding the small size of the dielectric structure, an influence of its shape cannot be neglected. Even for moderate dielectric contrasts one can expect having significant and detectable enhancement or suppression of the spontaneous emission rate near the surface of the biological macromolecule.

The kinetics of molecular oxygen migration in the isolated α chains of human hemoglobin as revealed by molecular dynamics simulations and laser kinetic spectroscopy.

Bimolecular and germinate molecular oxygen (O(2)) rebinding to isolated α chains of human adult hemoglobin in solutions is analyzed. Multiple extended molecular dynamics (MD) simulations of the O(2) migration within the protein after dissociation are described. Computational modeling is exploited to identify hydrophobic pockets within the αchains and internal O(2) migration pathways associated with the experimentally observed ligand rebinding kinetics.

Molecular oxygen binding with alpha and beta subunits within the R quaternary state of human hemoglobin in solutions and porous sol-gel matrices.

Nanosecond laser flash-photolysis technique was used to study bimolecular and geminate molecular oxygen (O2) rebinding to alpha and beta subunits within oxygenated human adult hemoglobin in solutions and porous wet sol-gel matrices. Plasticity associated with the tertiary structure within R-state hemoglobin is explored through measurements that focus on the functional properties of hemoglobin under conditions designed to tune the tertiary structure without inducing the R to T transition. Inequivalence in the O2 binding to the alpha and beta hemes within the R quaternary structure is studied.

Effect of zinc and cadmium ions on structure and function of myoglobin.

Laser flash photolysis technique was used to study zinc and cadmium ion effects on bimolecular and nanosecond geminate molecular oxygen (O(2)) rebinding to horse heart myoglobin. Time courses for geminate recombination are analyzed in terms of a three-step, side path model. In the presence of metal ions, the greatest changes are observed in the rate constant of the O(2) rebinding from within the primary docking site and the rate constant of the O(2) migration from the primary site to the secondary xenon docking sites.

Toward understanding the high PDT efficacy of chlorin e6-polyvinylpyrrolidone formulations: photophysical and molecular aspects of photosensitizer-polymer interaction in vitro.

It is recognized that chlorin e6-polyvinylpyrrolidone (Ce6-PVP) formulations are characterized by a high efficacy in photodynamic therapy of malignant tumors. Currently, a commercially available formulation of this type is Photolon (Fotolon) with Ce6:PVP=1:1 (w/w) and the weight-average molecular weight of PVP is 1.2x10(4).

Mutual effects of proton and sodium chloride on oxygenation of liganded human hemoglobin.

The different effects of pH and NaCl on individual O2-binding properties of alpha and beta subunits within liganded tetramer and dimer of human hemoglobin (HbA) were examined in a number of laser time-resolved spectroscopic measurements. A previously proposed approach [Dzhagarov BM & Lepeshkevich SV (2004) Chem Phys Lett390, 59-64] was used to determine the extent of subunit dissociation rate constant difference and subunit affinity difference from a single flash photolysis experiment. To investigate the effect of NaCl concentration on the association and dissociation rate constants we carried out a series of experiments at four different concentrations (0.

A kinetic description of dioxygen motion within alpha- and beta-subunits of human hemoglobin in the R-state: geminate and bimolecular stages of the oxygenation reaction.

Laser flash photolysis technique is used to study human hemoglobin (HbA) oxygenation. Monomolecular geminate oxygenation of triliganded R-state HbA molecules is described by a function of three exponentials. Geminate oxygenation of the alpha-subunit within R-state HbA is characterized by two components with time constants of 0.

Laser kinetic spectroscopy studies of the bimolecular oxygenation of alpha- and beta-subunits within the R-state of human hemoglobin.

Bimolecular oxygenation of tri-liganded R-state human hemoglobin (HbA) is described by bi-exponential kinetics with association rate constants k(alpha) = 27.2 +/- 1.3 (micro M*sec)(-1) and k(beta) = 62.

[Combined effect of gamma-irradiation and sodium nitrite on the oxidative sensitivity of rat hemoglobin].

gamma-Irradiation has been defined to increase in the rats blood the methemoglobin level providing for shortening the initiation phase and accelerates the autocatalytic phase initiation, reduces the period of half transforming hemoglobin into methemoglobin and increases the velocity of its oxidation. Alongside with the latter there is observed a violation of methemoglobin concentration growth dependence on the animals irradiation dose (in the range of 0.16-0.

Fluorescence decay time distribution analysis reveals two types of binding sites for 1,8-anilinonaphthalene sulfonate in native human oxyhemoglobin.

Binding of 1,8-anilinonaphthalene sulfonate (1,8-ANS) with native human oxyhemoglobin (Hb) in 50 mM potassium phosphate buffer (pH 7.4) was studied by steady-state fluorescence spectroscopy and by laser spectrofluorimetry with subnanosecond time resolution. The distribution of fluorescence decay times and parameters of two- and three-exponential deconvolution of the fluorescence kinetics of 1,8-ANS in Hb solution demonstrate that the emission at wavelengths lambdaem of 455-600 nm is not single-exponential and has components with mean decay times < 0.

Time-resolved fluorescence reveals two binding sites of 1,8-ANS in intact human oxyhemoglobin.

Time-resolved fluorescence of 1,8-anilinonaphthalene sulfonate (1,8-ANS) fluorescent probe bound to intact human oxyhemoglobin (HbO2) is investigated. Fluorescence emission spectra of 1,8-ANS in a potassium buffer solution (pH 7.4) of HbO2 undergo a substantial blue shift during first 6 ns after pulsed optical excitation at 337.

Photophysics of the cationic 5,10,15,20-tetrakis (4-N-methylpyridyl) porphyrin bound to DNA, [poly (dA-dT)]2 and [poly (dG-dC)]2: interaction with molecular oxygen studied by porphyrin triplet-triplet absorption and singlet oxygen luminescence.

Interaction between molecular oxygen and the cationic free-base 5,10,15,20-tetrakis (4-N-methylpyridyl) porphyrin (H2TMpyP4+) complexed with [poly (dA-dT)]2, [poly (dG-dC)]2 and calf thymus DNA, has been monitored in air-saturated heavy water solutions through porphyrin triplet-triplet absorption and singlet oxygen luminescence. Three different rate constants of porphyrin triplet state quenching have been found which correspond to different accessibilities of molecular oxygen to porphyrins embedded in the duplexes. The longest triplet state lifetime (30 microseconds), found for porphyrin bound to [poly (dG-dC)]2, corresponds to molecules well protected from oxygen.

[The alkaline Bohr effect: regulation of O2 binding with triliganded hemoglobin Hb(O2)3].

The processes of the proton concentration effect on the oxygen binding with triliganded human hemoglobin Hb(O2)3 have been studied by time resolved absorption spectroscopy. The pH-dependencies analysis carried out has shown that R-state alkaline Bohr effect was formed by two amino acid residues with pK = 7.3 +/- 0.