Действие ультрафиолетового излучения на тиамин и дисульфиды тиамина

In a neutral medium, the exposure of thiamine disulfide to the ultraviolet of solar radiation (as well as to the ultraviolet radiation of mercury lamp with λ > 300 nm) results in the formation of a thiamine molecule with closed thiazole ring and a molecule of thiamine thiazolone. Asymmetric thiamine disulfides, e.g., thiamine propyl disulfide, on exposure to ultraviolet (UVA range) produced thiamine and propyl disulfides. Thiamine and thiazolone of thiamine are stable upon exposure to light of 320-400 nm (UVA range). UV irradiation within spectral range of 200-300 nm results in further photodestruction of thiamine and thiamine thiazolone and production of 2-methyl-4-amino-5aminomethyl-pyrimidine as the main photoproduct. The possibility to use thiamine disulfide derivatives as a promising class of anti-cataract drugs as well as drugs to decrease the toxic effect of ultraviolet radiation on human retina is discussed. Под действием ультрафиолетового солнечного излучения (а также ультрафиолетового излучения ртутной лампы с λ > 300 нм) на тиамин дисульфид в нейтральной водной среде образуются молекулы тиамина с закрытым тиазоловым циклом и молекулы тиазолона тиамина. Асимметричный дисульфид тиамина, например тиаминпропил дисульфид, под действием ультрафиолетового излучения (UVA диапазон) образует тиамин и пропилдисульфид соответственно. Тиамин и тиазолон тиамина устойчивы к действию излучения 320-400 нм (UVA диапазон). При воздействии ультрафиолетового излучения с λ от 200 до 300 нм происходит фотодеструкция тиамина и тиазолона тиамина и образуется 2-метил4-амино-5-аминометил-пиримидин в качестве основного продукта. Обсуждается возможность использования дисульфидных производных тиамина как перспективного класса антикатарактальных препаратов, а также препаратов для снижения токсического действия ультрафиолетового излучения на сетчатку глаза

Time Resolved Photoelectron Spectroscopy of Thioflavin T Photoisomerization: A Simulation Study

The excited state isomerization of thioflavin T (ThT) is responsible for the quenching of its fluorescence in a non-restricted environment. The fluorescence quantum yield increases substantially upon binding to amyloid fibers. Simulations reveal that the variation of the twisting angle between benzothiazole and benzene groups (ϕ(1)) is responsible for the sub-picosecond fluorescence quenching. The evolution of the twisting process can be directly probed by photoelectron emission with energies ε ≥ 1.0 eV before the molecule reaches the ϕ(1)-twisted configuration (~300 fs)

Nanoparticle vesicle encoding for imaging and tracking cell populations.

For phenotypic behavior to be understood in the context of cell lineage and local environment, properties of individual cells must be measured relative to population-wide traits. However, the inability to accurately identify, track and measure thousands of single cells via high-throughput microscopy has impeded dynamic studies of cell populations. We demonstrate unique labeling of cells, driven by the heterogeneous random uptake of fluorescent nanoparticles of different emission colors. By sequentially exposing a cell population to different particles, we generated a large number of unique digital codes, which corresponded to the cell-specific number of nanoparticle-loaded vesicles and were visible within a given fluorescence channel. When three colors are used, the assay can self-generate over 17,000 individual codes identifiable using a typical fluorescence microscope. The color-codes provided immediate visualization of cell identity and allowed us to track human cells with a success rate of 78% across image frames separated by 8 h

Extrinsic Fluorescent Dyes as Tools for Protein Characterization

Noncovalent, extrinsic fluorescent dyes are applied in various fields of protein analysis, e.g. to characterize folding intermediates, measure surface hydrophobicity, and detect aggregation or fibrillation. The main underlying mechanisms, which explain the fluorescence properties of many extrinsic dyes, are solvent relaxation processes and (twisted) intramolecular charge transfer reactions, which are affected by the environment and by interactions of the dyes with proteins. In recent time, the use of extrinsic fluorescent dyes such as ANS, Bis-ANS, Nile Red, Thioflavin T and others has increased, because of their versatility, sensitivity and suitability for high-throughput screening. The intention of this review is to give an overview of available extrinsic dyes, explain their spectral properties, and show illustrative examples of their various applications in protein characterization

INTERRELATION OF GENES POLYMORPHISM OF THE ENDOTHELIAL NO-SYNTHASE (G894T, T786C) AND THE ENDOTHELIN-1 (G5665T) WITH THE EFFICIENCY OF THERAPY IN PATIENTS WITH ARTERIAL HYPERTENSION AFTER PREVIOUS ISCHEMIC STROKE

Background. Gene polymorphism of the endothelial NO-synthase (e-NOS) (G894T, T786C) and endothelin-1 (EDN-1) (G5665T) may be associated with a different response of patients with arterial hypertension (AH) to endotheliotropic therapy (ET). The aim of the study was to investigate the interrelation of the gene polymorphism of the e-NOS (G894T, T786C) and EDN-1 (G5665T) with the efficacy of therapy in patients with arterial hypertension after previous ischemic stroke. Material and methods: 65 people with arterial hypertension of II degree after previous ischemic stroke were examined. In all the patients, genotypes of e-NOS genes (G894T, T786C) and EDN-1 (G5665T) gene were determined. Endothelial function and vascular wall stiffness parameters were assessed in subgroups of homozygotes for dominant alleles (SGA) and in subgroups containing a recessive allele (SGB) before and after 12 weeks of ET. Results: Patients of SGB of e-NOS (G894T, T786C) and EDN-1 (G5665T) genes did not show a significant increase in forearm blood flow (FBF) and the percentage of target values of this parameter was lower compared to that in SGA. There was no significant decrease in the pulse wave velocity (PWV) in patients of EDN-1 (G5665T) gene SGB. The percentage of achievement of the target values of PWV in SGB was lower compared to that in SGA. Conclusions: Gene polymorphism of the e-NOS (G894T, T786C) and EDN-1 (G5665T) is not associated with the hypotensive effect of the drugs. The effect of the G894T e-NOS gene, T786C e-NOS gene and the G5665T EDN-1 gene correlated with the efficacy of endothelial dysfunction correction, which is manifested by the absence of a significant increase in FBF in carriers of genotypes with recessive alleles. The interrelation of the G5665T EDN-1 gene with the efficiency of correction of increased pulse wave velocity has been revealed, which is manifested by the absence of a significant lowering of this parameter in carriers of genotype with recessive alleles

Solvent Polarity Effect on Nonradiative Decay Rate of Thioflavin T

It has been established earlier that fluorescence quantum yield of thioflavin T (ThT)a probe widely used for amyloid fibrils detectionis viscosity-dependent, and photophysical properties of ThT can be well-described by the fluorescent molecular rotor model, which associates twisted internal charge transfer (TICT) reaction with the main nonradiative decay process in the excited state of the dye. Solutions of ThT in a range of polar solvents were studied using steady-state fluorescence and sub-picosecond transient absorption spectroscopy methods, and we showed that solvent effect on nonradiative transition rate <i>k</i>_nr cannot be reduced to the dependence on viscosity only and that ∼3 times change of <i>k</i>_nr can be observed for ThT in aprotic solvents and water, which correlates with solvent polarity. Different behavior was observed in alcohol solutions, particularly in longer <i>n</i>-alcohols, where TICT rate was mainly determined by rotational diffusion of ThT fragments. Quantum-chemical calculations of S₀ → S₁ transition energy were performed to get insight of polar solvent contribution to the excited-state energy stabilization. Effect of polar solvent on electronic energy levels of ThT was simulated by applying homogeneous electric field according to the Onsager cavity model. Static solvent effect on the excited-state potential energy surface, where charge transfer reaction takes place, was not essential to account for experimentally observed TICT rate differences in water and aprotic solvents. From the other side, nonradiative decay rate of ThT in water, ethylene glycol, and aprotic solvents was found to follow dynamics of polar solvation <i>k</i>_nr ∼ τ_<i>S</i>^–1, which can explain dependence of the TICT rate on both polarity and viscosity of the solvents