A Prototype Method for the Detection and Recognition of Pigments in the Environment Based on Optical Property Simulation.

The possibility of pigment detection and recognition in different environments such as solvents or proteins is a challenging, and at the same time demanding, task. It may be needed in very different situations: from the nondestructive in situ identification of pigments in paintings to the early detection of fungal infection in major agro-industrial crops and products. So, we propose a prototype method, the key feature of which is a procedure analyzing the lineshape of a spectrum. The shape of the absorption spectrum corresponding to this transition strongly depends on the immediate environment of a pigment and can serve as a marker to detect the presence of a particular pigment molecule in a sample. Considering carotenoids as an object of study, we demonstrate that the combined operation of the differential evolution algorithm and semiclassical quantum modeling of the optical response based on a generalized spectral density (the number of vibronic modes is arbitrary) allows us to distinguish quantum models of the pigment for different solvents. Moreover, it is determined that to predict the optical properties of monomeric pigments in protein, it is necessary to create a database containing, for each pigment, in addition to the absorption spectra measured in a predefined set of solvents, the parameters of the quantum model found using differential evolution.

Gaussian Decomposition vs. Semiclassical Quantum Simulation: Obtaining the High-Order Derivatives of a Spectrum in the Case of Photosynthetic Pigment Optical Properties Studying.

In this paper, a procedure for obtaining undistorted high derivatives (up to the eighth order) of the optical absorption spectra of biomolecule pigments has been developed. To assess the effectiveness of the procedure, the theoretical spectra of bacteriochlorophyll a, chlorophyll a, spheroidene, and spheroidenone were simulated by fitting the experimental spectra using the differential evolution algorithm. The experimental spectra were also approximated using sets of Gaussians to calculate the model absorption spectra. Theoretical and model spectra can be differentiated without smoothing (high-frequency noise filtering) to obtain high derivatives. Superimposition of the noise track on the model spectra allows us to obtain test spectra similar to the experimental ones. Comparison of the high derivatives of the model spectra with those of the test spectra allows us to find the optimal parameters of the filter, the application of which leads to minimal differences between the high derivatives of the model and test spectra. For all four studied pigments, it was shown that smoothing the experimental spectra with optimal filters makes it possible to obtain the eighth derivatives of the experimental spectra, which were close to the eighth derivatives of their theoretical spectra.

The role of the local environment on the structural heterogeneity of carotenoid ß-ionone rings.

Our analysis of the X-ray crystal structure of canthaxanthin (CAN) showed that its ketolated ß-ionone rings can adopt two energetically equal, but structurally distinct puckers. Quantum chemistry calculations revealed that the potential energy surface of the ß-ionone ring rotation over the plane of the conjugated π-system in carotenoids depends on the pucker state of the ß-ring. Considering different pucker states and ß-ionone ring rotation, we found six separate local minima on the potential energy surface defining the geometry of the keto-ß-ionone ring-two cis and one trans orientation for each of two pucker states. We observed a small difference in energy and no difference in relative orientation for the cis-minima, but a pronounced difference for the position of trans-minimum in alternative pucker configurations. An energetic advantage of ß-ionone ring rotation from a specific pucker type can reach up to 8 kJ/mol ([Formula: see text]). In addition, we performed the simulation of linear absorption of CAN in hexane and in a unit cell of the CAN crystal. The electronic energies of [Formula: see text] transition were estimated both for the CAN monomer and in the CAN crystal. The difference between them reached [Formula: see text], which roughly corresponds to the energy gap between A and B pucker states predicted by theoretical estimations. Finally, we have discussed the importance of such effects for biological systems whose local environment determines conformational mobility, and optical/functional characteristics of carotenoid.

In vitro renal calculi destruction by a high-frequency glow discharge plasma.

Despite the progress made in the treatment of nephrolithiasis, the existing methods of renal calculi destruction are not ideal and have both advantages and disadvantages. Considering the process of high-frequency glow discharge formation on the surface of an electrode and in an electrolyte solution, we obtained the results on the destruction of renal calculi in vitro. It was shown that the destruction of kidney stones by glow discharge plasma was caused by several processes-the plasma induced effect of hydrated electrons and shock wave effect of the electrolyte stimulated by electrical breakdowns in the plasma. The plasma generation modes were configured by estimating the thickness of the vapor-gas layer in which the plasma burns. Thus, the average rate of contact destruction of renal calculi was measured depending on the plasma generator input power and time of plasma exposure. We conclude that the method of stone fragmentation by high-frequency electrolyte plasma is rather perspective and can be used in endoscopic urology for percutaneous and transurethral lithotripsy.

A Novel Biodegradable Composite Polymer Material Based on PLGA and Silver Oxide Nanoparticles with Unique Physicochemical Properties and Biocompatibility with Mammalian Cells.

A method for obtaining a stable colloidal solution of silver oxide nanoparticles has been developed using laser ablation. The method allows one to obtain nanoparticles with a monomodal size distribution and a concentration of more than 108 nanoparticles per mL. On the basis of the obtained nanoparticles and the PLGA polymer, a nanocomposite material was manufactured. The manufacturing technology allows one to obtain a nanocomposite material without significant defects. Nanoparticles are not evenly distributed in the material and form domains in the composite. Reactive oxygen species (hydrogen peroxide and hydroxyl radical) are intensively generated on the surfaces of the nanocomposite. Additionally, on the surface of the composite material, an intensive formation of protein long-lived active forms is observed. The ELISA method was used to demonstrate the generation of 8-oxoguanine in DNA on the developed nanocomposite material. It was found that the multiplication of microorganisms on the developed nanocomposite material is significantly decreased. At the same time, the nanocomposite does not inhibit proliferation of mammalian cells. The developed nanocomposite material can be used as an affordable and non-toxic nanomaterial to create bacteriostatic coatings that are safe for humans.

The Relationship between the Spatial Arrangement of Pigments and Exciton Transition Moments in Photosynthetic Light-Harvesting Complexes.

Considering bacteriochlorophyll molecules embedded in the protein matrix of the light-harvesting complexes of purple bacteria (known as LH2 and LH1-RC) as examples of systems of interacting pigment molecules, we investigated the relationship between the spatial arrangement of the pigments and their exciton transition moments. Based on the recently reported crystal structures of LH2 and LH1-RC and the outcomes of previous theoretical studies, as well as adopting the Frenkel exciton Hamiltonian for two-level molecules, we performed visualizations of the LH2 and LH1 exciton transition moments. To make the electron transition moments in the exciton representation invariant with respect to the position of the system in space, a system of pigments must be translated to the center of mass before starting the calculations. As a result, the visualization of the transition moments for LH2 provided the following pattern: two strong transitions were outside of LH2 and the other two were perpendicular and at the center of LH2. The antenna of LH1-RC was characterized as having the same location of the strongest moments in the center of the complex, exactly as in the B850 ring, which actually coincides with the RC. Considering LH2 and LH1 as supermolecules, each of which has excitation energies and corresponding transition moments, we propose that the outer transitions of LH2 can be important for inter-complex energy exchange, while the inner transitions keep the energy in the complex; moreover, in the case of LH1, the inner transitions increased the rate of antenna-to-RC energy transfer.

The Effect of Plant Growth Compensation by Adding Silicon-Containing Fertilizer under Light Stress Conditions.

The effects of different spectral compositions of light-emitting diode (LED) sources and fertilizer containing biologically active silicon (Si) in the nutrient solution on morphological and physiological plant response were studied. Qualitative indicators and the productivity of plants of a red-leaved and a green-leaved lettuce were estimated. Lettuce was grown applying low-volume hydroponics in closed artificial agroecosystems. The positive effect of Si fertilizer used as a microadditive in the nutrient solution on the freshly harvested biomass was established on the thirtieth day of vegetation under LEDs. Increase in productivity of the red-leaved lettuce for freshly harvested biomass was 26.6%, while for the green-leaved lettuce no loss of dry matter was observed. However, being grown under sodium lamps, a negative impact of Si fertilizer on productivity of both types of plants was observed: the amount of harvested biomass decreased by 22.6% and 30.3% for the green- and red-leaved lettuces, respectively. The effect of using Si fertilizer dramatically changed during the total growing period: up to the fifteenth day of cultivation, a sharp inhibition of the growth of both types of lettuce was observed; then, by the thirtieth day of LED lighting, Si fertilizer showed a stress-protective effect and had a positive influence on the plants. However, by the period of ripening there was no effect of using the fertilizer. Therefore, we can conclude that the use of Si fertilizers is preferable only when LED irradiation is applied throughout the active plant growth period.

A Theoretical Analysis of Relations between Pressure Changes along Xylem Vessels and Propagation of Variation Potential in Higher Plants.

Variation potential (VP) is an important long-distance electrical signal in higher plants that is induced by local damages, influences numerous physiological processes, and participates in plant adaptation to stressors. The transmission of increased hydraulic pressure through xylem vessels is the probable mechanism of VP propagation in plants; however, the rates of the pressure transmission and VP propagation can strongly vary. We analyzed this problem on the basis of a simple mathematical model of the pressure distribution along a xylem vessel, which was approximated by a tube with a pressure gradient. It is assumed that the VP is initiated if the integral over pressure is more than a threshold one, taking into account that the pressure is transiently increased in the initial point of the tube and is kept constant in the terminal point. It was shown that this simple model can well describe the parameters of VP propagation in higher plants, including the increase in time before VP initiation and the decrease in the rate of VP propagation with an increase in the distance from the zone of damage. Considering three types of the pressure dynamics, our model predicts that the velocity of VP propagation can be stimulated by an increase in the length of a plant shoot and also depends on pressure dynamics in the damaged zone. Our results theoretically support the hypothesis about the impact of pressure variations in xylem vessels on VP propagation.

The role of vibronic modes in formation of red antenna states of cyanobacterial PSI.

Cyanobacterial photosystem I (PSI) constitutes monomeric and trimeric pigment-protein complexes whose optical properties are marked by the presence of long-wavelength absorption bands. In spite of numerous experimental studies, the nature of these bands is still under debate and requires intensive theoretical analysis. Collecting together the data of linear spectroscopy and single-molecule spectroscopy (SMS) of PSI from Arthrospira platensis, we performed quantum modeling of the optical response based on molecular exciton theory (ET) and the multimode Brownian oscillator model (MBOM). Applying MBOM, the spectra of the red antenna state were calculated considering a particular for each red state adjustment of the low-frequency vibronic modes. Within the framework of our PSI exciton model it was shown that the coupling energy between antenna chlorophylls cannot be a factor of the red states formation, thus the long-wavelength bands are calculated without attribution to so-called antenna red chlorophylls. By the fitting of Huang-Rhys factors and frequencies for the lowest vibronic modes, we were able to reproduce the effects of strong and weak electron-phonon coupling experimentally observed in SMS spectra of red antenna states. Based on our theoretical calculations and also analysis of existing crystal structures of cyanobacterial PSI, we assumed that long-wavelength Chls can be localized in the peripheral protein subunits containing one or two pigment molecules.

Structural peculiarities of keto-carotenoids in water-soluble proteins revealed by simulation of linear absorption.

To prevent irreversible damage caused by an excess of incident light, the photosynthetic machinery of many cyanobacteria uniquely utilizes the water-soluble orange carotenoid protein (OCP) containing a single keto-carotenoid molecule. This molecule is non-covalently embedded into the two OCP domains which are interconnected by a flexible linker. The phenomenon of OCP photoactivation, causing significant changes in carotenoid absorption in the orange and red form of OCP, is currently being thoroughly studied. Numerous additional spectral forms of natural and synthetic OCP-like proteins have been unearthed. The optical properties of carotenoids are strongly determined by the interaction of their electronic states with vibrational modes, the surrounding protein matrix, and the solvent. In this work, the effects of the pigment-protein interaction and vibrational relaxation in OCP were studied by computational simulation of linear absorption. Taking into account Raman spectroscopy data and applying the multimode Brownian oscillator model as well as the cumulant expansion technique, we have calculated a set of characteristic microparameters sufficient to demarcate different carotenoid states in OCP forms, using the model carotenoids spheroidene and spheroidenone in methanol/acetone solution as benchmarks. The most crucial microparameters, which determine the effect of solvent and protein environment, are the Huang-Rhys factors and the frequencies of C[double bond, length as m-dash]C and C-C stretching modes, the low-frequency mode and the FWHM due to inhomogeneous line broadening. Considering the difference of linear absorption between spheroidene and spheroidenone, which remarkably resembles the photoinduced changes of OCP absorption, and applying quantum chemical calculations, we discuss structural and functional determinants of carotenoid binding proteins.