Optical spectral diagnostics of the oxygenation level in periodontal tissues and photodynamic therapy using methylene blue in children with cerebral palsy.

Dental diseases occur in children with cerebral palsy three times higher than in healthy children. Low values of the unstimulated salivation rate (<0.3 ml per minute), pH and buffer capacity, changes in enzyme activity and sialic acid concentration, as well as increased saliva osmolarity and total protein concentration, which indicates impaired hydration, are the factors in the development of a gingiva disease in case of cerebral palsy. This leads to increased bacterial agglutination and the formation of acquired pellicle and biofilm, leading to the formation of dental plaque. There is a tendency toward an increase in the concentration of hemoglobin and a decrease in the degree of hemoglobin oxygenation, as well as an increase in the generation of reactive oxygen and nitrogen species. Photodynamic therapy (PDT) with the use of photosensitizer methylene blue improves blood circulation and the degree of oxygenation in periodontal tissues, as well as eliminates a bacterial biofilm. Analysis of back diffuse reflection spectra makes it possible to conduct non-invasive monitoring determine tissue areas with a low level of hemoglobin oxygenation for precision photodynamic exposure. Aim: To improve the effectiveness of phototheranostics methods using, namely PDT with simultaneous optical-spectral control, for the treatment of gingivitis in children with complex dental and somatic status (cerebral palsy). Methods: The study involved 15 children (6-18 y.o.) with various forms of cerebral palsy, in particular, spastic diplegia and atonic-astatic form and with gingivitis. The degree of hemoglobin oxygenation was measured in tissues before PDT and on the 12th day. PDT was performed using laser radiation (λ = 660 nm) with a power density of 150 mW/cm2 with a five-minute application of 0.01% MB. The total light dose was 45 ± 15 J/cm2. For statistical evaluation of the results, a paired Student's t-test was used. Results: The paper presents the results of phototheranostics using methylene blue in children with cerebral palsy. An increase in the level of hemoglobin oxygenation from 50 to 67% (p < 0.001) and a decrease in blood volume in the microcirculatory bed of periodontal tissues were shown. Conclusion: Photodynamic therapy methods with application of methylene blue make it possible to assess the state of the gingival mucosa tissue diseases objectively in real time, and to provide effective targeted therapy for gingivitis in children with cerebral palsy. There is a prospect that they can become widely used clinical methods.

Theranostic Properties of Crystalline Aluminum Phthalocyanine Nanoparticles as a Photosensitizer.

The study of phthalocyanines, known photosensitizers, for biomedical applications has been of high research interest for several decades. Of specific interest, nanophotosensitizers are crystalline aluminum phthalocyanine nanoparticles (AlPc NPs). In crystalline form, they are water-insoluble and atoxic, but upon contact with tumors, immune cells, or pathogenic microflora, they change their spectroscopic properties (acquire the ability to fluoresce and become phototoxic), which makes them upcoming agents for selective phototheranostics. Aqueous colloids of crystalline AlPc NPs with a hydrodynamic size of 104 ± 54 nm were obtained using ultrasonic dispersal and centrifugation. Intracellular accumulation and localization of AlPc were studied on HeLa and THP-1 cell cultures and macrophages (M0, M1, M2) by fluorescence microscopy. Crystallinity was assessed by XRD spectroscopy. Time-resolved spectroscopy was used to obtain characteristic fluorescence kinetics of AlPc NPs upon interaction with cell cultures. The photodynamic efficiency and fluorescence quantum yield of AlPc NPs in HeLa and THP-1 cells were evaluated. After entering the cells, AlPc NPs localized in lysosomes and fluorescence corresponding to individual AlPc molecules were observed, as well as destruction of lysosomes and a rapid decrease in fluorescence intensity during photodynamic action. The photodynamic efficiency of AlPc NPs in THP-1 cells was almost 1.8-fold that of the molecular form of AlPc (Photosens). A new mechanism for the occurrence of fluorescence and phototoxicity of AlPc NPs in interaction with cells is proposed.

Theoretical approaches used in the modelling of reversible and irreversible mitochondrial swelling in vitro.

Existing theoretical approaches were considered that allow modelling of mitochondrial swelling (MS) dynamics. Simple phenomenological kinetic models were reviewed. Simple and extended biophysical and bioenergetic models that ignore mechanical properties of inner mitochondrial membrane (IMM), and similar models that include these mechanical properties were also reviewed. Limitations of these models we considered, as regards correct modelling of MS dynamics. It was found that simple phenomenological kinetic models have significant limitations, due to dependence of the kinetic parameter values estimated by fitting of the experimental data on the experimental conditions. Additionally, such simple models provide no understanding of the detailed mechanisms behind the MS dynamics, nor of the dynamics of various system parameters during MS. Thus, biophysical and bioenergetic models ignoring IMM mechanical properties can't be used to model the transition between reversible and irreversible MS. However, simple and extended biophysical models that include IMM mechanical properties allow modelling the transition to irreversible swelling. These latter models are still limited due to significantly simplified description of biochemistry, compared to those of bioenergetic models. Finally, a strategy of model development is proposed, towards correct interpretation of the mitochondrial life cycle, including the effects of MS dynamics.

Temperature dependence of IR exciton emission spectra in Müller cell intermediate filaments.

Temperature dependences of IR exciton properties in Müller cell (MC) intermediate filaments (IFs) isolated from porcine retina were studied. It was found that the widths of the spectral emission bands in the 2500 cm-1 and 5000 cm-1 energy ranges grow with temperature. It was found that temperature effects on the bandwidth may be described by thermal activation of the low-frequency vibrational modes of the IFs. The average activation energies for the two IR bands were estimated. Considering the dynamics of IR emission, its buildup time was independent on the sample temperature, while its decay time decreased with temperature. Thus, the emission decay rate increased exponentially with the sample temperature. The mechanisms explaining the observed temperature effects were proposed and discussed. Taking into account that MC IFs are capable of transmitting ATP hydrolysis energy within and between cells, with these properties being apparently common for all IFs, these IFs may be used by cells for physical energy transport and communications. As presently reported, temperature effects upon IR exciton spectra should not affect these proposed physiological functions to any significant extent. Therefore, the currently reported data are important for improving our understanding of the physical communication mechanisms operating within and between cells.

Photo-activation of mitochondrial ATP synthesis.

ATP production by mitochondria isolated from Saccharomyces cerevisiae cells was accelerated upon both direct and indirect mitochondrial photo-activation (MPA). The extent of direct MPA was dependent on the wavelength of excitation light. Direct MPA was created by light in cytochrome c spectral absorption bands (440, 520 and 550 nm), this light was absorbed producing electronically excited cytochrome c, and the excitation energy of the latter was used in the ATP production chain. The activity of cytochrome c was tested with 600 nm light, where cytochrome c does not absorb, and thus ATP production rate remained the same as in darkness. Note that ATP production rates were significantly larger under light at 550, 520 and 440 nm. Therefore, photo-activation of cytochrome c was the first step of MPA synthesis of ATP. Indirect MPA of ATP production also proceeded via electronically excited cytochrome c, by energy transfer from electronically excited Co/BN film to cytochrome c located in the inner mitochondrial membrane (IMM). Co/BN excitons were generated by photons absorbed by the Co/BN film, which was not in contact with the mitochondrial sample. Next, these excitons propagated along the Co/BN film to the part of the film that was in contact with the mitochondrial sample. There the exciton energy was transferred to cytochrome c located in the IMM, producing electronically excited cytochrome c. Thus, excited cytochrome c was generated in a way different from that of direct MPA. Next, the energy of excited cytochrome c was used in activated ATP synthesis, with virtually the same effect for 519 and 427 nm excitation. Thus, the first step of ATP synthesis in indirect MPA was the exciton energy transfer from Co/BN film to cytochrome c located in the IMM, producing an electronically excited cytochrome c molecule. A phenomenological mechanism of direct and indirect MPA was proposed, and the model parameters were obtained by fitting the model to the experimental data. However, more information is needed before the detailed mechanism of ATP synthesis activation by electronically excited cytochrome c could be understood. The present results support the earlier proposed hypothesis of indirect MPA of ATP production in vertebrate retina in daylight.

Effects of pulsed electric fields on exciton propagation efficiency along Müller cell intermediate filaments. Possible separation mechanism of high- and low-contrast images by the eye-brain system.

In the current study, we tested a possible mechanism of low- and high-contrast image component discrimination by the vertebrate eye-brain system. Apparently the eye-brain system has to discriminate between the low-contrast image component formed by light scattered within the retina, due to interaction of photons with cells and their parts, and the high-contrast image component transmitted by excitons via the quantum mechanism. Presently, effects of pulsed electric fields applied to Müller cell (MC) intermediate filaments (IFs) on the efficiency of exciton propagation were explored. The effects of both pulse duration and amplitude were recorded. These experimental results show that the eye-brain system may be using signal modulation to discriminate between high- and low-contrast image components, improving our understanding of high-contrast vision in vertebrates.

Contrary to consensus, oxidation of ethanol by human alcohol dehydrogenase (ADH) 1A is activated by ATP.

Presently we report that enzymatic oxidation of ethanol (EtOH) by ADH1A alcohol dehydrogenase is strongly accelerated in presence of adenosine triphosphate (ATP), by up to the factor of 20 in vitro. This result provides a different look on the role of ATP in functioning of alcohol dehydrogenases (ADH), which until presently were a textbook example of enzymes not requiring ATP and successfully operating without it. However, ATP is available in every living cell and will activate reactions conducted by ADH enzymes in vivo. Therefore, the body of published literature describing properties of numerous ADH enzymes requires a thorough revision.

Reaction coupling in ADH1A alcohol dehydrogenase enzyme by exciplex formation with adenosine diphosphate moderated by low-energy electronic excited states.

Two commonly accepted theories about enzymes were revisited. The first states that adenosine triphosphate (ATP)-stored energy is only released when the substrate is in place, because the substrate changes the enzyme structure when it is bound to the enzyme. In fact, as demonstrated and discussed presently, no structural changes are required, and ATP-stored energy is released when it can be used. The second states that ATP-released energy moves along the enzyme molecule in the form of molecular vibrations (Davydov's vibrational solitons). In fact, as reported presently, energy released upon ATP hydrolysis moves in the form of excited-state electrons (excitons), with no molecular vibrations involved. The relevant experimental evidence was obtained for the human ADH1A alcohol dehydrogenase enzyme. Spontaneous ATP hydrolysis in the absence of substrate was apparently prevented by electronically excited enzyme + adenosine diphosphate (ADP) + inorganic phosphate (P) complex (exciplex) formed upon ATP hydrolysis. This exciplex kept ADP + P bound and in place for the inverse reaction, until the excess energy was dissipated in the enzyme-catalyzed reaction or by energy transfer to a suitable acceptor. Additionally, and contrary to textbooks, ADH1A has required ATP, working orders of magnitude faster in its presence.

Energy transfer along Müller cell intermediate filaments isolated from porcine retina: I. Excitons produced by ADH1A dimers upon simultaneous hydrolysis of two ATP molecules.

IR exciton propagation was explored in Müller cell (MC) intermediate filaments (IFs) filling a capillary matrix. These IFs have been isolated from porcine retina using different methods, while their properties were almost identical. Therefore, IFs isolated from the whole retinas were used presently. IR excitons were generated by IR radiation at 2 µm wavelength, or by enzymatic ATP hydrolysis, with the energy transferred to IFs. Excitons produced by ATP hydrolysis required simultaneous energy contribution of two ATP molecules, indicating simultaneous hydrolysis of two ATP molecules in the naturally dimeric human alcohol dehydrogenase enzyme (ADH1A). ATP hydrolysis was thus catalyzed by ADH1A…NAD+ enzymatic complexes absorbed at the IF extremities protruding out of the capillary matrix. The IR emission spectra of excitons were dependent on the exciton generation method. We believe this resulted from the exciton energy distribution varying in function of the generation method used. The latter seems reasonable, given the very long excited-state lifetimes, implying low nonradiative relaxation rates. The energy liberated by ATP hydrolysis has been measured directly in these experiments, for the first time. The results demonstrate that contrary to the predictions of equilibrium thermodynamics, the liberated energy is independent on the ATP/ADP concentration ratio, indicating that non-equilibrium reactions take place. Time-resolved experiments with excitons produced by pulsed IR radiation evaluated characteristic exciton propagation and emission times. For the first time, biexcitonic processes were observed in biological objects, whereby simultaneous hydrolysis of two ATP molecules bound to the same dimeric ADH1A molecule generated excitons carrying twice the energy liberated by hydrolysis of a single ATP molecule. The results reported indicate that ATP-liberated energy may be transmitted along natural polypeptide nanofibers in vivo, within and between live cells. These ideas could promote new understanding of the biophysics of life.

On the Effects of Mechanical Stress of Biological Membranes in Modeling of Swelling Dynamics of Biological Systems.

We highlight mechanical stretching and bending of membranes and the importance of membrane deformations in the analysis of swelling dynamics of biological systems, including cells and subcellular organelles. Membrane deformation upon swelling generates tensile stress and internal pressure, contributing to volume changes in biological systems. Therefore, in addition to physical (internal/external) and chemical factors, mechanical properties of the membranes should be considered in modeling analysis of cellular swelling. Here we describe an approach that considers mechanical properties of the membranes in the analysis of swelling dynamics of biological systems. This approach includes membrane bending and stretching deformations into the model, producing a more realistic description of swelling. We also discuss the effects of membrane stretching on swelling dynamics. We report that additional pressure generated by membrane bending is negligible, compared to pressures generated by membrane stretching, when both membrane surface area and volume are variable parameters. Note that bending deformations are reversible, while stretching deformation may be irreversible, leading to membrane disruption when they exceed a certain threshold level. Therefore, bending deformations need only be considered in reversible physiological swelling, whereas stretching deformations should also be considered in pathological irreversible swelling. Thus, the currently proposed approach may be used to develop a detailed biophysical model describing the transition from physiological to pathological swelling mode.

Optimization of upconversion luminescence excitation mode for deeper in vivo bioimaging without contrast loss or overheating.

Upconversion nanoparticles have attracted considerable attention as luminescent markers for bioimaging and sensing due to their capability to convert near-infrared (NIR) excitation into visible or NIR luminescence. However, the wavelength of about 970 nm is commonly used for the upconversion luminescence excitation, where the strong absorption of water is observed, which can lead to laser-induced overheating effects. One of the strategies for avoiding such laser-induced heating involves shifting the excitation into shorter wavelengths region. However, the influence of wavelength change on luminescent images quality has not been investigated yet. In this work, we compare wavelengths of 920, 940 and 970 nm for upconversion luminescence excitation in the thickness of biological tissues in terms of detected signal intensity and obtained image quality (contrast and signal-to-background ratio). Studies on biological tissue phantoms with various scattering and absorbing properties were performed to analyze the influence of optical parameters on the depth and contrast of the images obtained under 920-970 nm excitation. It was shown that at the same power the excitation wavelength shift reduces the detected signal intensity and the resulting image contrast. Visualization of biological tissue samples using shorter excitation wavelengths 920 and 940 nm also reduces signal-to-background ratio (S/B) of the obtained images. The S/B of the obtained images amounted to 2, 6 and 8 for 920, 940 and 970 nm, respectively. It was demonstrated that pulse-periodic excitation mode is preferable for obtaining high quality luminescent images of biological tissues deep layers and minimize overheating. Short pulse durations (duty cycle 20%) don't result in heating even for 1 W cm-2 pumping power density and allow obtaining high luminescence intensity, which provides good images quality.

In silico simulation of reversible and irreversible swelling of mitochondria: The role of membrane rigidity.

Mitochondria have been widely accepted as the main source of ATP in the cell. The inner mitochondrial membrane (IMM) is important for the maintenance of ATP production and other functions of mitochondria. The electron transport chain (ETC) generates an electrochemical gradient of protons known as the proton-motive force across the IMM and thus produces the mitochondrial membrane potential that is critical to ATP synthesis. One of the main factors regulating the structural and functional integrity of the IMM is the changes in the matrix volume. Mild (reversible) swelling regulates mitochondrial metabolism and function; however, excessive (irreversible) swelling causes mitochondrial dysfunction and cell death. The central mechanism of mitochondrial swelling includes the opening of non-selective channels known as permeability transition pores (PTPs) in the IMM by high mitochondrial Ca2+ and reactive oxygen species (ROS). The mechanisms of reversible and irreversible mitochondrial swelling and transition between these two states are still unknown. The present study elucidates an upgraded biophysical model of reversible and irreversible mitochondrial swelling dynamics. The model provides a description of the PTP regulation dynamics using an additional differential equation. The rigidity tensor was used in numerical simulations of the mitochondrial parameter dynamics with different initial conditions defined by Ca2+ concentration in the sarco/endoplasmic reticulum. We were able to estimate the values of the IMM rigidity tensor components by fitting the model to the previously reported experimental data. Overall, the model provides a better description of the reversible and irreversible mitochondrial swelling dynamics.

Energy propagation along polypeptide α-helix: Experimental data and ab initio zone structure.

We report new theoretical and experimental results that may significantly change our ideas on the workings of life. We performed ab initio analysis of the band structure of periodic α-helix polypeptides (PP) in function of the chain length. Three different calculation approaches were tested: (a) PP described semiempirically as a one-dimensional object, with the amino acids substituted by effective atoms; (b) density functional theory (DFT) as implemented in WIEN2k approach, and (c) CRYSTAL-17 software package. The approach (c) was used for the detailed ab initio analysis, as it provided better accuracy in less computation time. We found that the bandgap was weakly dependent on the PP composition, with the asymptotic values in the 0.43 - 0.63 eV range. We estimated the effective electron and hole masses, their mean free path and mobility for the glycine-PP. The electron mobility in the PP conductive band was about half of that in polycrystalline silicon. The PP zone structure was used to study the mechanism of energy transfer along the PP. The current-voltage (I/V) characteristics of Müller cell (MC) intermediate filaments (IFs) from porcine retina were experimentally measured. The measured I/V characteristics show that the IFs behave as semiconductors. These results were discussed in light of the presently reported PP zone structure theory. The results obtained may open new areas in biomedical research and applications.

Macro-scale transport of the excitation energy along a metal nanotrack: exciton-plasmon energy transfer mechanism.

Presently 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.

Müller glial cells contribute to dim light vision in the spectacled caiman (Caiman crocodilus fuscus): Analysis of retinal light transmission.

In this study, we show the capability of Müller glial cells to transport light through the inverted retina of reptiles, specifically the retina of the spectacled caimans. Thus, confirming that Müller cells of lower vertebrates also improve retinal light transmission. Confocal imaging of freshly isolated retinal wholemounts, that preserved the refractive index landscape of the tissue, indicated that the retina of the spectacled caiman is adapted for vision under dim light conditions. For light transmission experiments, we used a setup with two axially aligned objectives imaging the retina from both sides to project the light onto the inner (vitreal) surface and to detect the transmitted light behind the retina at the receptor layer. Simultaneously, a confocal microscope obtained images of the Müller cells embedded within the vital tissue. Projections of light onto several representative Müller cell trunks within the inner plexiform layer, i.e. (i) trunks with a straight orientation, (ii) trunks which are formed by the inner processes and (iii) trunks which get split into inner processes, were associated with increases in the intensity of the transmitted light. Projections of light onto the periphery of the Müller cell endfeet resulted in a lower intensity of transmitted light. In this way, retinal glial (Müller) cells support dim light vision by improving the signal-to-noise ratio which increases the sensitivity to light. The field of illuminated photoreceptors mainly include rods reflecting the rod dominance of the of tissue. A subpopulation of Müller cells with downstreaming cone cells led to a high-intensity illumination of the cones, while the surrounding rods were illuminated by light of lower intensity. Therefore, Müller cells that lie in front of cones may adapt the intensity of the transmitted light to the different sensitivities of cones and rods, presumably allowing a simultaneous vision with both receptor types under dim light conditions.

Computational Modeling of In Vitro Swelling of Mitochondria: A Biophysical Approach.

Swelling of mitochondria plays an important role in the pathogenesis of human diseases by stimulating mitochondria-mediated cell death through apoptosis, necrosis, and autophagy. Changes in the permeability of the inner mitochondrial membrane (IMM) of ions and other substances induce an increase in the colloid osmotic pressure, leading to matrix swelling. Modeling of mitochondrial swelling is important for simulation and prediction of in vivo events in the cell during oxidative and energy stress. In the present study, we developed a computational model that describes the mechanism of mitochondrial swelling based on osmosis, the rigidity of the IMM, and dynamics of ionic/neutral species. The model describes a new biophysical approach to swelling dynamics, where osmotic pressure created in the matrix is compensated for by the rigidity of the IMM, i.e., osmotic pressure induces membrane deformation, which compensates for the osmotic pressure effect. Thus, the effect is linear and reversible at small membrane deformations, allowing the membrane to restore its normal form. On the other hand, the membrane rigidity drops to zero at large deformations, and the swelling becomes irreversible. As a result, an increased number of dysfunctional mitochondria can activate mitophagy and initiate cell death. Numerical modeling analysis produced results that reasonably describe the experimental data reported earlier.

Improving cytotoxicity against cancer cells by chemo-photodynamic combined modalities using silver-graphene quantum dots nanocomposites.

The combination of chemotherapy and photodynamic therapy has emerged as a promising strategy for cancer therapy due to its synergistic effects. In this work, PEGylated silver nanoparticles decorated with graphene quantum dots (Ag-GQDs) were tested as a platform to deliver a chemotherapy drug and a photosensitizer, simultaneously, in chemo-photodynamic therapy against HeLa and DU145 cancer cells in vitro. Ag-GQDs have displayed high efficiency in delivering doxorubicin as a model chemotherapy drug to both cancer cells. The Ag-GQDs exhibited a strong antitumor activity by inducing apoptosis in cancer cells without affecting the viability of normal cells. Moreover, the Ag-GQDs exhibited a cytotoxic effect due to the generation of the reactive singlet oxygen upon 425 nm irradiation, indicating their applicability in photodynamic therapy. In comparison with chemo or photodynamic treatment alone, the combined treatment of Ag-GQDs conjugated with doxorubicin under irradiation with a 425 nm lamp significantly increased the death in DU145 and HeLa. This study suggests Ag-GQDs as a multifunctional and efficient therapeutic system for chemo-photodynamic modalities in cancer therapy.

External control of the Drosophila melanogaster egg to imago development period by specific combinations of 3D low-frequency electric and magnetic fields.

We report that the duration of the egg-to-imago development period of the Drosophila melanogaster, and the imago longevity, are both controllable by combinations of external 3-dimensional (3D) low-frequency electric and magnetic fields (LFEMFs). Both these periods may be reduced or increased by applying an appropriate configuration of external 3D LFEMFs. We report that the longevity of D. melanogaster imagoes correlates with the duration of the egg-to-imago development period of the respective eggs. We infer that metabolic processes in both eggs and imago are either accelerated (resulting in reduced time periods) or slowed down (resulting in increased time periods). We propose that external 3D LFEMFs induce electric currents in live systems as well as mechanical vibrations on sub-cell, whole-cell and cell-group levels. These external fields induce media polarization due to ionic motion and orientation of electric dipoles that could moderate the observed effects. We found that the longevity of D. melanogaster imagoes is affected by action of 3D LFEMFs on the respective eggs in the embryonic development period (EDP). We interpret this effect as resulting from changes in the regulation mechanism of metabolic processes in D. melanogaster eggs, inherited by the resulting imagoes. We also tested separate effects of either 3D electric or 3D magnetic fields, which were significantly weaker.

Modulation effect of low-frequency electric and magnetic fields on CO2 production and rates of acetate and pyruvate formation in Saccharomyces cerevisiae cell culture.

We studied action of one-dimensional, two-dimensional and three-dimensional low-frequency oscillating electric and magnetic fields on sugar metabolism in Saccharomyces cerevisiae cell culture. S. cerevisiae cells were grown on a minimal medium containing glucose (10%) as a carbon source and salts (0.3-0.5%) that supplied nitrogen, phosphorus and trace metals. We found that appropriate three-dimensional field patterns can either accelerate or inhibit sugar metabolism in yeast cells, as compared to control experiments. We also studied aerobic sugar metabolism, with similar results. Sugar metabolism was monitored by formation of pyruvate, acetate and CO2. We found that for the P1 parameter set the cell metabolism accelerates as evaluated by all of the monitored chemical products, and the cell density growth rate also accelerates, with opposite effects observed for the P2 parameter set. These parameter sets are introduced using D, ω, φ, B, ω', and φ' - vectors defining amplitudes, frequencies and phases of periodic electric and magnetic fields, respectively. Thus, the P1 parameter set: D = (2.6, 3.1, 2.2) V/cm; ω = (0.8, 1.6, 0.2) kHz; φ = (1.31, 0.9, 1.0) rad; B = (3.1, 7.2, 7.2) × 10(-4) T; ω' = (2.1, 1.3, 3.1) kHz; φ' = (0.4, 2.1, 2.8) rad; and the P2 parameter set: D = (4.3, 1.6, 3.8) V/cm; ω = (3.3, 1.8, 2.8) kHz; φ = (0.86, 1.1, 0.4) rad; B = (5.4, 1.3, 1.3) × 10(-4) T; ω' = (1.3, 1.7, 0.9) kHz; φ' = (2.6, 1.7, 1.7) rad. The effects obtained for the less complex field combinations that used one-dimensional or two-dimensional configurations, or omitted either the electric or the magnetic contribution, were significantly weaker than those obtained for the complete P1 and P2 parameter sets.

Photodissociation of (SO2⋯XH) Van der Waals complexes and clusters (XH = C2H2, C2H4, C2H6) excited at 32,040-32,090 cm(-1) with formation of HSO2 and X.

We studied photodecomposition dynamics of (SO2⋯XH) Van der Waals' (VdW) complexes and clusters in gas phase, with X = C2H, C2H3, and C2H5. SO2 was excited by frequency-doubled radiation of a tunable dye laser and resonance-enhanced multiphoton ionization was used to detect the C2H (m/z 25), C2H3 (m/z 27), and C2H5 (m/z 29) ions by time-of-flight mass spectroscopy. Spectra obtained at higher nozzle pressures (P0 > 2.5 atm) indicate formation of clusters. Detailed studies of the VdW complex structure were carried out by analyzing the rotational structure of the respective action spectra. We also performed ab initio theoretical analysis of structures of the VdW complexes and transitional states leading to photodecomposition. We find that the structure of the transition state is significantly different as compared to the equilibrium ground-state structure of the respective complex. The photodecomposition mechanism depends on the hydrocarbon molecule bound to SO2.