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- Quantum mechanism of light energy propagation through an avian retinaPublication . Zueva, Lidia; Golubeva, Tatiana; Korneeva, Elena; Resto, Oscar; Inyushin, Mikhail; Khmelinskii, Igor; Makarov, VladimirTaking into account the ultrastructure of the Pied Flycatcher foveal retina reported earlier and the earlier reported properties of Muller cell (MC) intermediate filaments (IFs) isolated from vertebrate retina, we proposed a quantum mechanism (QM) of light energy transfer from the inner limiting membrane level to visual pigments in the photoreceptor cells. This mechanism involves electronic excitation energy transfer in a donor-acceptor system, with the IFs excited by photons acting as energy donors, and visual pigments in the photoreceptor cells acting as energy acceptors. It was shown earlier that IFs with diameter 10 nm and length 117 mu m isolated from vertebrate eye retina demonstrate properties of light energy guide, where exciton propagates along such IFs from MC endfeet area to photoreceptor cell area. The energy is mostly transferred via the contact exchange quantum mechanism. Our estimates demonstrate that energy transfer efficiencies in such systems may exceed 80-90%. Thus, the presently developed quantum mechanism of light energy transfer in the inverted retina complements the generally accepted classic optical mechanism and the mechanism whereby Muller cells transmit light like optical fibers. The proposed QM of light energy transfer in the inverted retina explains the high image contrast achieved in photopic conditions by an avian eye, being probably also active in other vertebrates.
- Absorption spectra of Muler cell intermediate filaments: experimental results and theoretical modelsPublication . Khmelinskii, Igor; Makarov, VladimirExperimental spectra of Muller cell (MC) intermediate filaments (IFs) isolated from porcine retina are reported in this work. The absorption spectra recorded at different MC IF concentrations were used to estimate their absorption cross-sections at different wavelengths. The average absorption cross-section of a single MC IF was ca. (0.97...2.01) x 10(-1) cm(2) in the 650-445 nm spectral range. To interpret these experimental absorption spectra, we made ab initio calculations of the optical spectra of a-helix polypeptides, and also used a simplified theoretical approach that modeled an IF by a conductive wire. The energy spectra of the refractive index, extinction coefficient (absorption cross-section), energy loss and reflectivity functions for different photon polarizations, with strong anisotropy with respect to the system axis, were calculated ab initio for polyglycine a-helix molecule containing 1000 glycine residues. Strong anisotropy of these parameters was explained by photons interacting with different electronic transitions. Note that similarly strong anisotropy was also obtained for the optical absorption cross-sections in the simplified model. Both modeling approaches were used for calculating the absorption cross sections of interest. As a result, the absorption cross-section for photons propagating axially along MC IFs was much larger than their geometrical cross-section. The latter result was explained taking into account the density of electronic states, with numerous electrons contributing to the transition intensity at a given energy. We found that the simple conductive wire model describes the MC IF absorption spectrum better than the ab initio spectra. The latter conclusion was explained by the limitations of ab initio analysis, which only took into account one alpha-helix with 1000 aminoacids, whereas each porcine Muller cell IF is assembled of thousands of protein molecules, reaching the total length of ca. 100 mu m. The presently reported results contribute to the understanding of the quantum mechanism of high-contrast vision of vertebrate eyes. Published by Elsevier B.V.
- Quantum confinement in multi-nanolayer sandwich systemsPublication . Khmelinskii, Igor; Makarov, Vladimir I.Presently we explored quantum confinement (QC) in three-nanolayer sandwich systems, composed of Au-SnO2-Fe, Au-SnO2-Si and Au-SnO2-Ag layers. We recorded the absorption spectra of these sandwich systems, all with discrete structure. We recorded the action spectra of the photocurrent for the Au-SnO2-Fe sandwich system, with the photocurrent quantum yields increasing with the photon energy, achieving 3.1 at 4.7 x 10(4) cm(-1). The photocurrent action spectra correlate with high accuracy with optical absorption spectra. We discuss the mechanisms determining the absorption bandwidth value, including surface imperfections, thermal distribution of the vibrational level populations in the electronic ground state, and the diabatic coupling of levels of the excited state to those of a "dark" state. Volt-Ampere (V/A) characteristics were recorded for all three of the sandwich systems, quite similar to those of a Schottky diode. We report the parameter values of the V/A characteristics, found by fitting the experimental data with a theoretical curve. We also report charge density changes in the SnO2 layer caused by low constant voltage applied to the sandwich structure, observed as changes in the absorption band intensity.
- Multivariate curve resolution Alternating least squares analysis of the total synchronous fluorescence spectra: An attempt to identify polyphenols contribution to the emission of apple juicesPublication . Wlodarska, Katarzyna; Pawlak-Lemanska, Katarzyna; Khmelinskii, Igor; Sikorska, EwaPresently we applied multivariate curve resolution alternating least squares (MCR-ALS) method for the analysis of front-face total synchronous fluorescence spectra (TSFS) of differently processed apple juices. This analysis enabled extracting of the TSFS profiles of five fluorescent components with distinct spectral characteristics and different contributions to the fluorescence of individual juices. Based on the spectral profiles and quantitative relationship with the chemical parameters describing the antioxidant properties of juices, three of the resolved components may be tentatively attributed to phenolic compounds. The analysis using multiple linear regression (MLR) and partial least square (PLS) regression confirmed better performance of fluorescence for the prediction of the total flavonoid content (TFC) as opposed to the total phenolic content (TPC) and total antioxidant capacity (TAC). This study demonstrated that MCR-ALS decomposition of the TSFS may provide a selective tool for understanding and interpretation of the observed relationships between the fluorescence and the total antioxidant indices of the apple juices.
- Optical transparency and electrical conductivity of intermediate filaments in Muller cells and single-wall carbon nanotubesPublication . Khmelinskii, Igor; Makarov, VladimirPresently we investigated the electrical conductivity and optical transparency of Muller cell intermediate filaments. For comparison, the same properties were also explored in the model system of single-wall carbon nanotubes. We report the method of separation and purification of porcine (Sus scrofa domestica) intermediate filaments, extracted from the retinal Muller cells. We also report experimental and theoretical methods of measurements and calculations of the resistivity and light transmission yield by the intermediate filaments and single wall carbon nanotubes. The measured resistivity values were (4.7 +/- 0.3) x 10(-4) and (2.8 +/- 0.2) x 10(-4) Omega.m(-1).cm(2) at 5 degrees C (278 K), for the intermediate filaments and single wall carbon nanotubes, respectively, being quite close to those of typical metals. We report a method for measuring the light energy transmission by these nanostructures. We found that they efficiently transfer excitation energy along their axis, with the light reemitted at their other end. The measured yields of transferred light energy were 0.50 +/- 0.03 and 0.26 +/- 0.02 for intermediate filaments and single wall carbon nanotubes, respectively (lambda(exc) = 546.1 nm