Browsing by Author "Makarov, Vladimir"
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- 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.
- Current–voltage characteristics of a Co/Ni bilayer nanofilmPublication . Khmelinskii, Igor; Makarov, VladimirWidespread interest in optical and electrical properties of nanostructured systems began more than 20 years ago. Here, optical and electrical properties of Co/Ni bilayer nanofilms are explored. These optical and electrical properties were described in terms of a common confined wavefunction spanning both Co and Ni layers. The effective relative electron mass parameter f estimated for this bilayer film was about 0.1489. Temperature dependence of the current-voltage characteristics of the Co/Ni bilayer nanofilms was described as that of a Schottky diode with the Schottky barrier height of US = 24 cm-1, very small compared to other semiconducting materials. Therefore, Co/Ni bilayer nanofilms apparently had semiconducting properties, which may approxi-mately be described using Schottky diode theory. Such semiconducting properties of bilayer metal nanofilms could be used in special low-temperature low-consumption electronic devices.
- Electric field modulation of energy transfer along intermediate filaments isolated from porcine retinaPublication . Khmelinskii, Igor; Makarov, VladimirWe report an experimental method for simultaneous measurement of the electric properties and energy transfer by natural biological fibers. We found that energy transfer efficiency along intermediate filaments (IFs) isolated from porcine retina varied with the potential difference applied to these IFs. The maximum measured effect amounted to 25% of the transfer efficiency increase. The recorded I/U plots characteristic of the IFs demonstrate the behavior of a semiconductor with 0.62 eV band gap. These results show that the image signal might be modulated by the potential difference across the cell membrane, facilitating image contrast enhancement in the brain.
- Electric field modulation of light energy transmission along intermediate filaments isolated from porcine retinaPublication . Khmelinskii, Igor; Makarov, VladimirPresently we report new experimental method for simultaneous measurements of electrical and optical properties in vitro for the intermediate filaments (IFs) in the axial direction, complemented by the method to measure light intensity absorbed by IFs aligned within the capillary matrix. These methods were used to simultaneously measure spectroscopic and electric properties of Müller cell (MC) IFs extracted from porcine retina. Using light at 546 nm, we found that these IFs are excellent conductors of light energy, with the efficiency of ca. 0.5 without external voltage field and 0.7 in presence of an external voltage of 0.1 V, and good conductors of electric current, with the conductivity value close to that of typical metals. We also found that the efficiency of light energy transmission along IFs depends on the external applied voltage. The presently reported optical and electrical properties of MC IFs may endow vertebrate eyes with high-contrast vision, providing evidence in favor of a mechanism regulating the amount of light energy transmitted via MC IFs between inner and outer limiting membrane levels in vertebrate retina.
- Electron microscopy study of the central retinal fovea in Pied flycatcher: evidence of a mechanism of light energy transmission through the retinaPublication . Zueva, Lidia; Golubeva, Tatiana; Korneeva, Elena; Resto, Oscar; Inyushin, Mikhail; Khmelinskii, Igor; Makarov, VladimirWe present unique ultrastructural data on avian retinal cells. Presently and earlier (Zueva et al., 2016) we explored distribution of intermediate filaments (IFs) in retinal cells of the Pied flycatcher (Ficedula hypoleuca, Passeriformes, Aves) in the central foveolar zone. This retinal zone only contains single and double cone photoreceptors. Previously we found that continuous IFs span Müller cells (MC) lengthwise from the retinal inner limiting membrane (ILM) layer up to the outer limiting membrane (OLM) layer. Here we describe long cylindrical bundles of IFs (IFBs) inside the cone inner segments (CIS) adjoining the cone plasma membrane, with these IFBs following along the cone lengthwise, and surrounding the cone at equal spacing one from the other. Double cones form a combined unit, wherein they are separated by their respective plasma membranes. Double cones thus have a common external ring of IFBs, surrounding both cone components. In the layer of cilia, the IFBs that continue into the cone outer segment (COS) follow on to the cone apical tip along the direction of incident light, with single IFs separating from the IFB, touching, and sometimes passing in-between the light-sensitive lamellae of the COS. These new data support our previous hypothesis on the quantum mechanism of light energy propagation through the vertebrate retina (Zueva et al., 2016, 2019).
- Focusing effects of ballistic transverse-quantized excitons in metal nanofilmsPublication . Makarov, Vladimir; Khmelinskii, IgorNew type of behavior of transverse-quantized excitons was discovered in metal nanofilms. These excitons demonstrated ballistic properties, propagating along nanofilms in straight lines along centimeter distances, reflecting at the film patch boundaries, and refracting at the boundary separating films of different materials but with the same exciton energy. Exciton reflection and focusing was explored in elliptically shaped metal film patches, along with exciton refraction on the boundary line separating two different film patches with compatible transverse-confinementgenerated electronic structures. These transverse-quantized excitons interact with phonons very weakly, prohibited by symmetry selection rules. The latter statement was confirmed in timeresolved experiments. Weak interactions explain rectilinear trajectories and long lifetimes of excitons in thin metal films.
- Foveolar muller cells of the pied flycatcher: morphology and distribution of intermediate filaments regarding cell transparencyPublication . Zueva, Lidia; Golubeva, Tatiana; Korneeva, Elena; Makarov, Vladimir; Khmelinskii, Igor; Inyushin, MikhailSpecialized intermediate filaments (IFs) have critical importance for the clearness and uncommon transparency of vertebrate lens fiber cells, although the physical mechanisms involved are poorly understood. Recently, an unusual low-scattering light transport was also described in retinal Muller cells. Exploring the function of IFs in Muller cells, we have studied the morphology and distribution pattern of IFs and other cytoskeletal filaments inside the Muller cell main processes in the foveolar part of the avian (pied flycatcher) retina. We found that some IFs surrounded by globular nanoparticles (that we suggest are crystallines) are present in almost every part of the Muller cells that span the retina, including the microvilli. Unlike IFs implicated in the mechanical architecture of the cell, these IFs are not connected to any specific cellular membranes. Instead, they are organized into bundles, passing inside the cell from the endfeet to the photoreceptor, following the geometry of the processes, and repeatedly circumventing numerous obstacles. We believe that the presently reported data effectively confirm that the model of nanooptical channels built of the IFs may provide a viable explanation of Muller cell transparency.
- Intermediate filaments are natural energy conductors in live cellsPublication . Khmelinskii, Igor; Makarov, VladimirTwo possible mechanisms describing intra-and inter-cell energy transfer in biological systems were analyzed. The first one is based on Davydov vibration soliton (DVS) theory, implying C=O vibrational energy transfer along alpha-helix polypeptides. According to Davydov, a certain vibration of one of the C=O groups somehow receives the entirety of ATP hydrolysis energy within an enzyme molecule. Next, dipole-dipole interactions of the C=O groups of neighboring amino acid residues should ensure propagation of the DVS along the polypeptide chain, transporting it to the site of catalytic reaction. Strong limitations of this theory when applied to energy transfer in living systems were underlined, accompanied by total lack of experimental evidence of DVS existence. The second, much more viable mechanism, based on electronic excited state (exciton) propagation along individual protein molecules and their assemblies - intermediate filaments (IFs) - was considered and discussed in detail. Excitons in IFs may be generated by photon absorption or by ATP hydrolysis energy transfer to IFs. Infrared (IR) excitons were generated in the latter case, which propagated along IFs, enabling energy transfer within and between cells, and inter-cellular communications. Earlier is has been noted that high-contrast vision of vertebrates is based on photon energy propagation along Muller cell (MC) IFs in the form of excitons, from the inner limiting membrane retinal layer to the outer fragments of cone cells, located in the outer limiting membrane retinal layer. Therefore, MC IFs operate as photon energy guides, transferring excitons from MC to cone cells, and thus communicating external visual information to the retinal cones and the brain. We finally conclude that apparently the mechanism based on the properties of IFs as natural energy guides plays the main role in communications within and between cells of live organisms.
- Intermediate filaments in the retinal Muller cells as natural light energy guidesPublication . Khmelinskii, Igor; Makarov, VladimirIn the current study, we investigated transmission spectrum of the intermediate filaments (IFs) extracted from porcine retinal Muller cells (MC). The recorded transmission spectrum is quite similar to that of the entire guinea pig retina, providing direct proof that the quantum mechanism (QM) of light energy transmission through the inverted retina is in fact the main mechanism determining the high-contrast vision of the vertebrate eyes. The recorded transmission spectrum of the IFs was deconvoluted into four bands, which we assign to different types of IFs. We interpret the differences in the transmission band shape and maxima as differences in the effective electron mass, dependent on the IF structure and composition of its constituting proteins. We analyzed model systems containing IFs and dye molecules, and IFs bridging two adjacent cobalt nanofilms on a substrate. The respective results demonstrate that IFs function as waveguides transferring energy from an energy donor and to an energy acceptor, by way of the exchange mechanism. The presently reported results provide direct experimental confirmation of the earlier proposed quantum mechanism for the high-contrast vision of vertebrate eyes. The mechanism proposed in the current study may be generalized, providing a consistent alternative to Davydov's theory of vibrational solitons in enzymes.
- Macro-scale transport of the excitation energy along a metal nanotrack: exciton-plasmon energy transfer mechanismPublication . Khmelinskii, Igor; Skatchkov, Serguei N.; Makarov, VladimirPresently we report (i) excited state (exciton) propagation in a metal nanotrack over macroscopic distances, along with (ii) energy transfer from the nanotrack to adsorbed dye molecules. We measured the rates of both of these processes. We concluded that the effective speed of exciton propagation along the nanotrack is about 8 × 107 cm/s, much lower than the surface plasmon propagation speed of 1.4 × 1010 cm/s. We report that the transmitted energy yield depends on the nanotrack length, with the energy emitted from the surface much lower than the transmitted energy, i.e. the excited nanotrack mainly emits in its end zone. Our model thus assumes that the limiting step in the exciton propagation is the energy transfer between the originally prepared excitons and surface plasmons, with the rate constant of about 5.7 × 107 s-1. We also conclude that the energy transfer between the nanotrack and the adsorbed dye is limited by the excited-state lifetime in the nanotrack. Indeed, the measured characteristic buildup time of the dye emission is much longer than the characteristic energy transfer time to the dye of 81 ns, and thus must be determined by the excited state lifetime in the nanotrack. Indeed, the latter is very close to the characteristic buildup time of the dye emission. The data obtained are novel and very promising for a broad range of future applications.
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