[Relation of photochemical capacity to enzymatic processes].
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Enzymes↗
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[Possible intervention of photochemical mechanism in the process of cancerization by aromatic hydrocarbons and their heterocyclic analogues].
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Energy Transfer↗
Inhibition of retrovirus-induced syncytium formation by photoproducts of a brominated 1,8-naphthalimide compound.
A major disadvantage of conventional phototherapy is the requirement for the in situ delivery of stimulating photoenergy subsequent to the binding of photochemicals to target malignant cells, or virus-infected cells, or viruses. This drawback has resulted in considerable limitation in the use of photochemicals in photomedicine. To circumvent this problem, we have investigated the antiviral efficacy of a brominated 1,8-naphthalimide photocompound, termed LY66Br [3-bromo-4-(hexylamino)-N-hexyl-1,8-naphthalimide], which upon exposure to visible light at 420 nm generates independently of oxygen one or more stable antiviral molecular photoproducts (e.g., is 'preactivated'). Human cell lines infected with the human immunodeficiency virus type 1 (HIV-1), or with the human T-lymphotropic virus type-1 (HTLV-I) exposed to photochemical products of LY66Br (P-LY66Br) completely lost their ability to form syncytia in vitro. Photoproducts of P-LY66Br retain full antiviral activity for at least 3 and 6 weeks when stored at room temperature and at -80 degrees C, respectively. Concentrations of P-LY66Br, effective in inhibiting syncytium formation mediated by HIV-1 and HTLV-I, were nontoxic to normal red cell components of whole blood (red blood cell 2,3-diphosphoglyceric acid, adenosine triphosphate, osmotic fragility or blood type antigens). Additionally, no evidence of acute toxicity was demonstrated in mice following an intravenous bolus inoculation to achieve plasma concentration of 600 microM of P-LY66Br. These findings represent the first demonstration of inhibition of retrovirus-induced syncytium formation by a photochemical product, and justify further investigation of the preactivation process of photochemicals in the treatment of systemic viral infections such as the acquired immunodeficiency syndrome (AIDS), in cancer therapy, and in sterilization of banked blood products.
1-Naphthylamine↗
Photochemical N-demethylation of alkaloids.
Certain alkaloids were observed to undergo N-demethylation processes under photochemical conditions. Tropine, acetyltropine, tropinone, and atropine were cleanly N-demethylated upon treatment with tetraphenylporphin, oxygen, and light. Dextromethorphan also underwent a N-demethylation reaction, but reacted further to afford an imine. In contrast, 14-acyloxycodeinones underwent a photochemically induced tandem N-demethylation acyl migration.
Alkaloids↗
A study of reactive oxygen species in mainstream of cigarette.
UNLABELLED: Reactive oxygenated species (ROS) not only exist in living organisms, they also exist in our environment. Combustion process and photochemical reactions are the major source of environmental ROS, and combustion process produced ROS has been gradually gaining attention in recent years. The purpose of this study is to determine the concentrations of ROS in the mainstream smoke of cigarettes sold in the marketplace using the DCFH2 fluorescence method and to understand particulate and gaseous concentrations of ROS. This research will also discuss the relationship between ROS and nicotine, found in popular cigarette brands, as well as the effectiveness of cigarette filters to remove ROS. Results indicate that the ROS concentration of mainstream smoke is 18.64-54.81 nmol H2O2/l while the correlation coefficients of nicotine and tar to total ROS are 0.959 and 0.909, respectively. Gaseous ROS concentrations are 14.32-39.03 nmol H2O2/l, and make up 71.21-85.99% of the total. It can be clearly seen therefore, that ROS exist mainly in the gaseous phase. Particulate ROS is dominant at PM2.5 (ROS(TSP)/ROS(PM2.5) is 0.652-0.959). The experimental results involving the tobacco leaves and cigarette ash show that ROS in mainstream smoke comes from the combustion process and not from the tobacco leaves. There is no effective means of eliminating ROS from mainstream smoke, regardless of whether a cigarette filter contains active charcoal. PRACTICAL IMPLICATIONS: This study showed that cigarette combustion will produce high concentration of ROS, and this high concentration of ROS in mainstream cigarette smoke probably is one major factor contributing to a high incidence of lung cancer in smokers. Environmental tobacco smoke (ETS) or second-hand smoke is a major indoor air pollutant that could potentially harm non-smokers. We will try to determine the ROS in ETS in the future.
Filtration↗
Fundamentals of the psoralen-based Helinx technology for inactivation of infectious pathogens and leukocytes in platelets and plasma.
Psoralens plus ultraviolet A (UVA) light inactivate viruses and bacteria as well as leukocytes. A system employing the synthetic psoralen compound amotosalen hydrochloride (S-59), in combination with UVA light, is being developed to decontaminate platelet concentrates and plasma in a blood-bank setting. S-59 is a heterocyclic psoralen compound that reacts by a three-step process with nucleic acids (NAs): (1) S-59 intercalates into the double helix; (2) upon illumination with long-wavelength ultraviolet light (UVA), it covalently attaches to a single strand, forming a monoadduct; and (3) additional illumination causes a photoreaction of the monoadduct with the second NA strand, resulting in an interstrand crosslink. The reaction occurs with the genomic material of DNA- and RNA-based viruses and occurs in genomes that are single stranded as well as double stranded. Inactivation rate is related to genome size. Large genomes such as those in leukocytes are far more susceptible to inactivation than are viruses such as hepatitis B virus (HBV), which is inactivated (>10(5) logs) under conditions being developed for blood-bank use. The efficiency of the process is affected by a number of practical considerations such as solution components and light source. The S-59 photochemical treatment process (PCT) has been optimized for platelet concentrates as currently processed for transfusion.
DNA↗
Photodegradation of antibiotics on soil surfaces: laboratory studies on sulfadiazine in an ozone-controlled environment.
Among the processes affecting transport and degradation of antibiotics released to the environment during application of manure and slurry to agricultural land, photochemical transformations are of particular interest. Drying-out of the top soil layer under field conditions enables sorption of surface-applied antibiotics to soil dust, thus facilitating direct, indirect, and sensitized photodegradation at the soil/atmosphere interface. For studying various photochemical transformation processes of sulfadiazine, a photovolatility chamber designed in accordance with the requirements of the USEPA Guideline and 161-3 was used. Application of 14C-labeled sulfadiazine enabled complete mass balances and allowed for investigating the impact of various surfaces (glass and soil dust) and environmental factors, i.e., irradiation and atmospheric ozone, on photodegradation and volatilization. Volatilization was shown to be a negligible process. Even after increasing the air temperature up to 35 degrees C only minor amounts of sulfadiazine and transformation products (0.01-0.28% of applied radioactivity) volatilized. Due to direct and indirect photodegradation, the highest extent of mineralization to 14CO2 (3.9%), the formation of degradation products and of nonextractable soil residues was measured in irradiated soil dust experiments using ozone concentrations of 200 ppb. However, even in the dark significant mineralization was observed when ozone was present, indicating ozone-controlled transformation of sulfadiazine to occur at the soil surface.
Anti-Infective Agents↗
Photochemical decomposition of phenazone derivatives. Part 7: Mechanism of decomposition in aqueous solutions.
Kinetic studies, supplemented by the isolation and identification of the products of decomposition, have proved the process of photochemical decomposition of phenazone derivatives to be a complex reaction, involving several successive parallel reactions, one of which is predominant depending on the concentration of the solution and the atmosphere above it. In an oxygen-free atmosphere and at low concentrations (10(-4) mol/dm3) decomposition is almost wholly the result of second photolysis of zero order to aziridine derivative----aniline----isonitrile. At higher concentrations (10(-3)-10(-2) mol/dm3), the contribution from the reaction of water photoaddition to the double bond C3-C4 increases. Whereas at concentrations of order greater than or equal to 10(-2) mol/dm3, photoisomerization to imidazole derivatives is predominant. In air, one onserves additionally a second reaction of photooxidation to 4-hydroxy-phenazone----1-acetylo-1-methyl-2-phenyl-hydrazine, a reaction of photodemethylation at N2 with simultaneous oxidation to the 4-ketoderivative, and reactions of hydrolysis characteristic for the individual derivatives. The principal primary photolytic reaction for the group of compounds studied consists in cleavage of the N1-N2 bond of the pyrazoline ring.
Antipyrine↗
Optimal experimental design and artificial neural networks applied to the photochemically enhanced Fenton reaction.
Among advanced oxidation processes (AOPs), the photochemically enhanced Fenton reaction may be considered as one of the most efficient for the degradation of contaminants in industrial wastewater. This process involves a series of complex reactions. Therefore, an empirical model based on artificial neural networks has been developed for fitting the experimental data obtained in a laboratory batch reactor for the degradation of 2,4-dimethyl aniline (2,4-xylidine), chosen as a model pollutant. The model describes the evolution of the pollutant concentration during irradiation time as a function of the process conditions. It has been used for simulating the behavior of the reaction system in sensitivity studies aimed at optimizing the amounts of reactants employed in the process, an iron(III) salt and hydrogen peroxide, as well as the temperature. The results show that the process is most sensitive to the concentration of iron(III) salt and temperature, whereas the concentration of hydrogen peroxide has a minor effect.
Aniline Compounds↗
Photochemical inactivation of enzymes.
The mechanisms of enzyme inactivation by ultraviolet light and visible light in the presence of sensitizing dyes are reviewed. Recent flash photolysis studies on amino acids and enzymes are summarized in terms of proposed models relating the initial photochemical reactions to permanent chemical and biological damage. The generation and reactions of singlet oxygen are discussed in connection with photodynamic processes. The photochemical results are compared with ionizing radiations, particularly pulse radiolytic methods employing radical anions as selective probes. The interrelationships between the various modes of enzyme inactivation are discussed, as well as the new information to be learned about the structure and functions of the native enzymes from selective radiation-induced alterations.
Carboxypeptidases↗
Sonochemical and photochemical oxidation of organic matter.
Recent developments in sonochemistry have led us to study its use to treat water and wastewater. The effects of ultrasound wave in hydrophilic chemical oxidations are mainly due to hydroxyl radical production during the cavitation-induced water decomposition. Currently, the sonochemical destruction of aromatic compounds in water solution is obtained with low rates. The aim of this work is to evaluate the efficiency of the sonochemical effect in conjunction with a photochemical irradiation. Taking phenol as an example, the combined action of sonochemistry and photochemistry has been considered in a 'sonuv' reactor. An important enhancement of the degradation rate of phenol has been observed. It may be the result of three different oxidative processes: direct photochemical action, high frequency sonochemistry and reaction with ozone (produced by UV irradiation of air). The process has been successfully tested to lower the chemical oxygen demand of a municipal wastewater.
Journal Article↗
Preclinical safety profile of plasma prepared using the INTERCEPT Blood System.
BACKGROUND AND OBJECTIVES: The newly developed INTERCEPT Blood System for plasma uses the addition of a new psoralen, amotosalen HCl (AMOTOSALEN), followed by illumination with ultraviolet A light, to inactivate viruses, bacteria, protozoa and leucocytes that may contaminate fresh-frozen plasma (FFP). Extensive toxicology studies were performed to characterize the safety of the photochemical treatment process for its intended use with plasma. MATERIALS AND METHODS: The studies of general toxicology, safety pharmacology, phototoxicity, reproductive toxicity and venous irritation, summarized in this review, provide a comprehensive toxicology profile for photochemically treated 100% plasma. RESULTS: No specific target organ toxicity (based on clinical or histological pathology), phototoxicity, or reproductive toxicity was observed. CONCLUSIONS: The results of an extensive series of studies have demonstrated no toxicologically relevant effects of photochemically treated 100% plasma prepared using the INTERCEPT Blood System for plasma.
Animals↗
Photochemical and Nonphotochemical Fluorescence Quenching Processes in the Diatom Phaeodactylum tricornutum.
Nonphotochemical fluorescence quenching was found to exist in the dark-adapted state in the diatom Phaeodactylum tricornutum. Pretreatment of cells with the uncoupler carbonylcyanide m-chlorophenylhydrazone (CCCP) or with nigericin resulted in increases in dark-adapted minimum and maximum fluorescence yields. This suggests that a pH gradient exists across the thylakoid membrane in the dark, which serves to quench fluorescence levels nonphotochemically. The physiological processes involved in establishing this proton gradient were sensitive to anaerobiosis and antimycin A. Based on these results, it is likely that this energization of the thylakoid membrane is due in part to chlororespiration, which involves oxygen-dependent electron flow through the plastoquinone pool. Chlororespiration has been shown previously to occur in diatoms. In addition, we observed that cells treated with 3-(3,4-dichlorophenyl)-1,1-dimethylurea exhibited very strong nonphotochemical quenching when illuminated with actinic light. The rate and extent of this quenching were light-intensity dependent. This quenching was reversed upon addition of CCCP or nigericin and was thus due primarily to the establishment of a pH gradient across the thylakoid membrane. Preincubation of cells with CCCP or nigericin or antimycin A completely abolished this quenching. Cyclic electron transport processes around photosystem I may be involved in establishing this proton gradient across the thylakoid membrane under conditions where linear electron transport is inhibited. At steady state under normal physiological conditions, the qualitative changes in photochemical and nonphotochemical fluorescence quenching at increasing photon flux densities were similar to those in higher plants. However, important quantitative differences existed at limiting and saturating intensities. Dissimilarities in the factors that regulate fluorescence quenching mechanisms in these organisms may account for these differences.
Journal Article↗
Trypanosoma cruzi inactivation in human platelet concentrates and plasma by a psoralen (amotosalen HCl) and long-wavelength UV.
Trypanosoma cruzi, the protozoan pathogen that causes Chagas' disease, can be found in the blood of infected individuals for their entire life span. This presents a serious challenge in safeguarding blood products. Transmission of T. cruzi from blood products is a frequent occurrence in Latin America, where Chagas' disease is endemic. This study was designed to determine whether T. cruzi could be inactivated in human platelet concentrates and plasma by a photochemical treatment process with long-wavelength UV A light (UVA, 320 to 400 nm) plus the psoralen amotosalen HCl (Cerus Corporation). Units of platelet concentrates (300 ml) and plasma (300 ml) were intentionally contaminated with approximately 10(6) T. cruzi trypomastigotes, the T. cruzi form found in the bloodstream, per ml. The viability of T. cruzi after photochemical inactivation was determined by their ability to replicate in 3T3 fibroblasts. Controls, including treatment with 150 micro M amotosalen or 3 J/cm(2) UVA alone, did not lead to reduction of the viability of T. cruzi in plasma or platelet concentrates. However, treatment with 150 micro M amotosalen plus 3 J/cm(2) UVA inactivated T. cruzi to undetectable levels in plasma and platelet concentrates. This represented a >5.4-log reduction of T. cruzi in platelet concentrates and >5.0-log reduction of T. cruzi in plasma. We conclude that the amotosalen plus UVA photochemical inactivation technology is effective in inactivating high levels of protozoan pathogens, such as T. cruzi, in platelet concentrates and plasma, as has been previously shown for numerous viruses and bacteria.
Animals↗
Modular Photoswitchable Molecular Glues for Chemo-Optogenetic Control of Protein Function in Living Cells.
Optogenetic systems using photosensitive proteins and chemically induced dimerization/proximity (CID/CIP) approaches enabled by chemical dimerizers (also termed molecular glues), are powerful tools to elucidate the dynamics of biological systems and to dissect complex biological regulatory networks. Here, we report a versatile chemo-optogenetic system using modular, photoswitchable molecular glues (sMGs) that can undergo repeated cycles of optical control to switch protein function on and off. We use molecular dynamics (MD) simulations to rationally design the sMGs and further expand their scope by incorporating different photoswitches, resulting in sMGs with customizable properties. We demonstrate that this system can be used to reversibly control protein localization, organelle positioning, protein-fragment complementation as well as posttranslational protein levels by light with high spatiotemporal precision. This system enables sophisticated optical manipulation of cellular processes and thus opens up a new avenue for chemo-optogenetics.
Optogenetics↗
The use of riboflavin for the inactivation of pathogens in blood products.
BACKGROUND AND OBJECTIVES: In recent years, the desire to develop methods to inactivate pathogens in blood components has continued to grow. Several of these proposed approaches have been introduced or are currently in clinical studies. The use of chemical inactivating agents must be considered in terms of the current safety of the blood supply and the potential risks that the introduction of new chemical entities into blood components may carry. The impact which these treatment procedures have on the in vitro and in vivo performance of these products must also be considered relative to the potential benefit of the pathogen inactivation potential they offer. This paper will discuss one possible approach for inactivating pathogens in blood using vitamin B2, Riboflavin, and light. MATERIALS AND METHODS: We have used Riboflavin for treating plasma and platelets and evaluated protein quality and platelet function in vitro. Initial toxicology tests to assess the impact of infusion of photoproducts generated in these processes have also been conducted in rodents. Cytotoxicity evaluations have been used to assess the possible impact of photoproduct toxicity in vivo. Virus and bacteria spiking studies using a variety of human and animal model pathogens have been conducted in order to asses the efficacy of this process. RESULTS: Initial toxicology assessment of the photoproducts of Riboflavin generated under the proposed treatment conditions have been favorable. Virus and bacteria clearance studies have demonstrated efficacy of the procedure against a wide range of human and animal pathogens, including intracellular HIV-1. Studies with platelet and plasma function indicated reductions in vitro comparable to other proposed treatment approaches. CONCLUSION: The use of Riboflavin in a photochemical decontamination process for blood components shows promise.
Blood Platelets↗
[Photoelectron decay time-resolved spectrum of AgCl crystals doped with K4Ru(CN)6 complex].
Microwave absorption and film dielectric spectrum detection technology was used to study the influence of complex K4Ru (CN)6 on the photoelectron decay time-resolved spectrum of cubic AgCl crystals illuminated in this paper. The results indicate that the influence of the doping content and doping position of the complex K4Ru(CN)6 on the photoelectron decay time-resolved spectrum is evident. The photoelectron decay process of this emulsion is slowest, and the photoelectron lifetime is longest when doped with K4Ru (CN)6 of 2.45 x 10(-5) mol x (mol Ag)(-1) at doping positions of 75% Ag.
Crystallization↗
Oxygen activation by photoexcited protoberberinium alkaloids from Mahonia aquifolium.
Protoberberinium salts, i.e. berberine (I), palmatine (II) and jatrorrhizine (III) prepared from Mahonia aquifolium (Pursh) Nutt. belong to isoquinoline alkaloids possessing interesting biological activity (e.g. antibacterial, antimalarial, antitumor). The characteristic UV/Vis absorption band maxima of I-III iodide salts were found in regions 350 and 425 nm in dimethylsulfoxide (DMSO) and ethanol solvents, and were only negligibly influenced by substitution changes on the C-2 and C-3 positions. The fluorescence intensity of protoberberinium salts monitored in ethanol solutions was significantly lowered by iodide counter-ions, and decreased in the order berberine > palmatine > jatrorrhizine. EPR spectroscopy supplied evidence of the formation of super-oxide anion radicals and singlet oxygen upon irradiation of berberine in oxygenated DMSO solvent. The photochemical generation of O(2) (.-) and (1)O(2) in DMSO solutions of palmatine and jatrorrhizine was substantially lower, and probably reflected the replacement of a photolabile methylenedioxy group at C-2 and C-3 positions in the berberine molecule by two methoxy groups in palmatine, and methoxyl (C-2) and hydroxyl (C-3) substitution in jatrorrhizine. Additionally, the powder EPR spectra of protoberberinium iodides I-III measured at 290 K revealed the presence of single-line EPR signals (g(eff) = 2.0044), which were attributed to hydroperoxidic structures produced by the autoxidation process. The photochemical reactions of protoberbenium salts producing reactive oxygen species after UVA excitation should be integrated in biological activity investigations, as well as in their applications in skin disorder treatment.
Berberine↗