PhotochemistryPhotochemical Processes: Chemical reactions effected by light.Photosystem II Protein Complex: A large multisubunit protein complex found in the THYLAKOID MEMBRANE. It uses light energy derived from LIGHT-HARVESTING PROTEIN COMPLEXES to catalyze the splitting of WATER into DIOXYGEN and of reducing equivalents of HYDROGEN.Photosynthesis: The synthesis by organisms of organic chemical compounds, especially carbohydrates, from carbon dioxide using energy obtained from light rather than from the oxidation of chemical compounds. Photosynthesis comprises two separate processes: the light reactions and the dark reactions. In higher plants; GREEN ALGAE; and CYANOBACTERIA; NADPH and ATP formed by the light reactions drive the dark reactions which result in the fixation of carbon dioxide. (from Oxford Dictionary of Biochemistry and Molecular Biology, 2001)Chlorophyll: Porphyrin derivatives containing magnesium that act to convert light energy in photosynthetic organisms.Light: That portion of the electromagnetic spectrum in the visible, ultraviolet, and infrared range.Exobiology: The interdisciplinary science that studies evolutionary biology, including the origin and evolution of the major elements required for life, their processing in the interstellar medium and in protostellar systems. This field also includes the study of chemical evolution and the subsequent interactions between evolving biota and planetary evolution as well as the field of biology that deals with the study of extraterrestrial life.Chenopodiaceae: The goosefoot plant family of the order Caryophyllales, subclass Caryophyllidae, class Magnoliopsida. It includes beets and chard (BETA VULGARIS), as well as SPINACH, and salt tolerant plants.Photolysis: Chemical bond cleavage reactions resulting from absorption of radiant energy.Halorhodopsins: Light driven chloride ion pumps that are ubiquitously found in halophilic archaea (HALOBACTERIALES).Photosynthetic Reaction Center Complex Proteins: Protein complexes that take part in the process of PHOTOSYNTHESIS. They are located within the THYLAKOID MEMBRANES of plant CHLOROPLASTS and a variety of structures in more primitive organisms. There are two major complexes involved in the photosynthetic process called PHOTOSYSTEM I and PHOTOSYSTEM II.Earth (Planet): Planet that is the third in order from the sun. It is one of the four inner or terrestrial planets of the SOLAR SYSTEM.Atmosphere: The gaseous envelope surrounding a planet or similar body. (From Random House Unabridged Dictionary, 2d ed)Bacteriorhodopsins: Rhodopsins found in the PURPLE MEMBRANE of halophilic archaea such as HALOBACTERIUM HALOBIUM. Bacteriorhodopsins function as an energy transducers, converting light energy into electrochemical energy via PROTON PUMPS.Light-Harvesting Protein Complexes: Complexes containing CHLOROPHYLL and other photosensitive molecules. They serve to capture energy in the form of PHOTONS and are generally found as components of the PHOTOSYSTEM I PROTEIN COMPLEX or the PHOTOSYSTEM II PROTEIN COMPLEX.Desonide: A nonfluorinated corticosteroid anti-inflammatory agent used topically for DERMATOSES.Photoreceptors, Microbial: Light absorbing proteins and protein prosthetic groups found in certain microorganisms. Some microbial photoreceptors initiate specific chemical reactions which signal a change in the environment, while others generate energy by pumping specific ions across a cellular membrane.Plant Leaves: Expanded structures, usually green, of vascular plants, characteristically consisting of a bladelike expansion attached to a stem, and functioning as the principal organ of photosynthesis and transpiration. (American Heritage Dictionary, 2d ed)Rhodopsin: A purplish-red, light-sensitive pigment found in RETINAL ROD CELLS of most vertebrates. It is a complex consisting of a molecule of ROD OPSIN and a molecule of 11-cis retinal (RETINALDEHYDE). Rhodopsin exhibits peak absorption wavelength at about 500 nm.Phycobiliproteins: Light harvesting proteins found in phycobilisomes.Sensory Rhodopsins: Photosensory rhodopsins found in microorganisms such as HALOBACTERIA. They convert light signals into biochemical information that regulates certain cellular functions such as flagellar motor activity.Quantum Theory: The theory that the radiation and absorption of energy take place in definite quantities called quanta (E) which vary in size and are defined by the equation E=hv in which h is Planck's constant and v is the frequency of the radiation.Lasers: An optical source that emits photons in a coherent beam. Light Amplification by Stimulated Emission of Radiation (LASER) is brought about using devices that transform light of varying frequencies into a single intense, nearly nondivergent beam of monochromatic radiation. Lasers operate in the infrared, visible, ultraviolet, or X-ray regions of the spectrum.Photons: Discrete concentrations of energy, apparently massless elementary particles, that move at the speed of light. They are the unit or quantum of electromagnetic radiation. Photons are emitted when electrons move from one energy state to another. (From Hawley's Condensed Chemical Dictionary, 11th ed)Cryptochromes: Flavoproteins that function as circadian rhythm signaling proteins in ANIMALS and as blue-light photoreceptors in PLANTS. They are structurally-related to DNA PHOTOLYASES and it is believed that both classes of proteins may have originated from an earlier protein that played a role in protecting primitive organisms from the cyclical exposure to UV LIGHT.Fluorescence: The property of emitting radiation while being irradiated. The radiation emitted is usually of longer wavelength than that incident or absorbed, e.g., a substance can be irradiated with invisible radiation and emit visible light. X-ray fluorescence is used in diagnosis.Halobacterium: A genus of HALOBACTERIACEAE whose growth requires a high concentration of salt. Binary fission is by constriction.Water: A clear, odorless, tasteless liquid that is essential for most animal and plant life and is an excellent solvent for many substances. The chemical formula is hydrogen oxide (H2O). (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Retinaldehyde: A carotenoid constituent of visual pigments. It is the oxidized form of retinol which functions as the active component of the visual cycle. It is bound to the protein opsin forming the complex rhodopsin. When stimulated by visible light, the retinal component of the rhodopsin complex undergoes isomerization at the 11-position of the double bond to the cis-form; this is reversed in "dark" reactions to return to the native trans-configuration.Spectrophotometry: The art or process of comparing photometrically the relative intensities of the light in different parts of the spectrum.Retinal Pigments: Photosensitive protein complexes of varied light absorption properties which are expressed in the PHOTORECEPTOR CELLS. They are OPSINS conjugated with VITAMIN A-based chromophores. Chromophores capture photons of light, leading to the activation of opsins and a biochemical cascade that ultimately excites the photoreceptor cells.Ultraviolet Rays: That portion of the electromagnetic spectrum immediately below the visible range and extending into the x-ray frequencies. The longer wavelengths (near-UV or biotic or vital rays) are necessary for the endogenous synthesis of vitamin D and are also called antirachitic rays; the shorter, ionizing wavelengths (far-UV or abiotic or extravital rays) are viricidal, bactericidal, mutagenic, and carcinogenic and are used as disinfectants.Spectrum Analysis: The measurement of the amplitude of the components of a complex waveform throughout the frequency range of the waveform. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Carbon Dioxide: A colorless, odorless gas that can be formed by the body and is necessary for the respiration cycle of plants and animals.Flavins: Derivatives of the dimethylisoalloxazine (7,8-dimethylbenzo[g]pteridine-2,4(3H,10H)-dione) skeleton. Flavin derivatives serve an electron transfer function as ENZYME COFACTORS in FLAVOPROTEINS.FlavoproteinsPhotosystem I Protein Complex: A large multisubunit protein complex that is found in the THYLAKOID MEMBRANE. It uses light energy derived from LIGHT-HARVESTING PROTEIN COMPLEXES to drive electron transfer reactions that result in either the reduction of NADP to NADPH or the transport of PROTONS across the membrane.Cyanobacteria: A phylum of oxygenic photosynthetic bacteria comprised of unicellular to multicellular bacteria possessing CHLOROPHYLL a and carrying out oxygenic PHOTOSYNTHESIS. Cyanobacteria are the only known organisms capable of fixing both CARBON DIOXIDE (in the presence of light) and NITROGEN. Cell morphology can include nitrogen-fixing heterocysts and/or resting cells called akinetes. Formerly called blue-green algae, cyanobacteria were traditionally treated as ALGAE.Carbon: A nonmetallic element with atomic symbol C, atomic number 6, and atomic weight [12.0096; 12.0116]. It may occur as several different allotropes including DIAMOND; CHARCOAL; and GRAPHITE; and as SOOT from incompletely burned fuel.Carotenoids: The general name for a group of fat-soluble pigments found in green, yellow, and leafy vegetables, and yellow fruits. They are aliphatic hydrocarbons consisting of a polyisoprene backbone.Electron Transport: The process by which ELECTRONS are transported from a reduced substrate to molecular OXYGEN. (From Bennington, Saunders Dictionary and Encyclopedia of Laboratory Medicine and Technology, 1984, p270)Rhodobacter sphaeroides: Spherical phototrophic bacteria found in mud and stagnant water exposed to light.Protons: Stable elementary particles having the smallest known positive charge, found in the nuclei of all elements. The proton mass is less than that of a neutron. A proton is the nucleus of the light hydrogen atom, i.e., the hydrogen ion.Spectrophotometry, Ultraviolet: Determination of the spectra of ultraviolet absorption by specific molecules in gases or liquids, for example Cl2, SO2, NO2, CS2, ozone, mercury vapor, and various unsaturated compounds. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Molecular Structure: The location of the atoms, groups or ions relative to one another in a molecule, as well as the number, type and location of covalent bonds.Kinetics: The rate dynamics in chemical or physical systems.Spectrophotometry, Infrared: Spectrophotometry in the infrared region, usually for the purpose of chemical analysis through measurement of absorption spectra associated with rotational and vibrational energy levels of molecules. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Chloroplasts: Plant cell inclusion bodies that contain the photosynthetic pigment CHLOROPHYLL, which is associated with the membrane of THYLAKOIDS. Chloroplasts occur in cells of leaves and young stems of plants. They are also found in some forms of PHYTOPLANKTON such as HAPTOPHYTA; DINOFLAGELLATES; DIATOMS; and CRYPTOPHYTA.Spectrum Analysis, Raman: Analysis of the intensity of Raman scattering of monochromatic light as a function of frequency of the scattered light.Electron Spin Resonance Spectroscopy: A technique applicable to the wide variety of substances which exhibit paramagnetism because of the magnetic moments of unpaired electrons. The spectra are useful for detection and identification, for determination of electron structure, for study of interactions between molecules, and for measurement of nuclear spins and moments. (From McGraw-Hill Encyclopedia of Science and Technology, 7th edition) Electron nuclear double resonance (ENDOR) spectroscopy is a variant of the technique which can give enhanced resolution. Electron spin resonance analysis can now be used in vivo, including imaging applications such as MAGNETIC RESONANCE IMAGING.Oxygen: An element with atomic symbol O, atomic number 8, and atomic weight [15.99903; 15.99977]. It is the most abundant element on earth and essential for respiration.Isomerism: The phenomenon whereby certain chemical compounds have structures that are different although the compounds possess the same elemental composition. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed)Oxidation-Reduction: A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471).Models, Chemical: Theoretical representations that simulate the behavior or activity of chemical processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment.Temperature: The property of objects that determines the direction of heat flow when they are placed in direct thermal contact. The temperature is the energy of microscopic motions (vibrational and translational) of the particles of atoms.Sodium Chloride: A ubiquitous sodium salt that is commonly used to season food.Spectrometry, Fluorescence: Measurement of the intensity and quality of fluorescence.Plants: Multicellular, eukaryotic life forms of kingdom Plantae (sensu lato), comprising the VIRIDIPLANTAE; RHODOPHYTA; and GLAUCOPHYTA; all of which acquired chloroplasts by direct endosymbiosis of CYANOBACTERIA. They are characterized by a mainly photosynthetic mode of nutrition; essentially unlimited growth at localized regions of cell divisions (MERISTEMS); cellulose within cells providing rigidity; the absence of organs of locomotion; absence of nervous and sensory systems; and an alternation of haploid and diploid generations.Hydrogen-Ion Concentration: The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH = log 1/2[1/(H+)], where (H+) is the hydrogen ion concentration in gram equivalents per liter of solution. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Models, Molecular: Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures.Plant Proteins: Proteins found in plants (flowers, herbs, shrubs, trees, etc.). The concept does not include proteins found in vegetables for which VEGETABLE PROTEINS is available.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Bacterial Proteins: Proteins found in any species of bacterium.Protein Conformation: The characteristic 3-dimensional shape of a protein, including the secondary, supersecondary (motifs), tertiary (domains) and quaternary structure of the peptide chain. PROTEIN STRUCTURE, QUATERNARY describes the conformation assumed by multimeric proteins (aggregates of more than one polypeptide chain).

The endogenous chromophore of retinal G protein-coupled receptor opsin from the pigment epithelium. (1/2984)

The recent identification of nonvisual opsins has revealed an expanding family of vertebrate opsin genes. The retinal pigment epithelium (RPE) and Muller cells contain a blue and UV light-absorbing opsin, the RPE retinal G protein-coupled receptor (RGR, or RGR opsin). The spectral properties of RGR purified from bovine RPE suggest that RGR is conjugated in vivo to a retinal chromophore through a covalent Schiff base bond. In this study, the isomeric structure of the endogenous chromophore of RGR was identified by the hydroxylamine derivatization method. The retinaloximes derived from RGR in the dark consisted predominantly of the all-trans isomer. Irradiation of RGR with 470-nm monochromatic or near-UV light resulted in stereospecific isomerization of the bound all-trans-retinal to an 11-cis configuration. The stereospecificity of photoisomerization of the all-trans-retinal chromophore of RGR was lost by denaturation of the protein in SDS. Under the in vitro conditions, the photosensitivity of RGR is at least 34% that of bovine rhodopsin. These results provide evidence that RGR is bound in vivo primarily to all-trans-retinal and is capable of operating as a stereospecific photoisomerase that generates 11-cis-retinal in the pigment epithelium.  (+info)

Histologic analysis of photochemical lesions produced in rhesus retina by short-wave-length light. (2/2984)

The photopathology of retinal lesions produced by extended exposure (1000 sec) to low corneal power levels (62 microW) of blue light (441 nm) was investigated by light microscopy in 20 rhesus eyes over an interval ranging from 1 hr to 90 days after exposure. Results indicate a nonthermal type of photochemical lesion originating in the retinal pigment epithelium and leading to a histological response with hypopigmentation which requires 48 hr to appear. This type of lesion helps to explain solar retinitis and eclipse blindness and has significance for aging and degenerative changes in the retina.  (+info)

Photophysical analysis of class I major histocompatibility complex protein assembly using a xanthene-derivatized beta2-microglobulin. (3/2984)

Spectral changes and a sixfold increase in the emission intensity were observed in the fluorescence of a single xanthene probe (Texas red) attached to beta2m-microglobulin (beta2m) upon assembly of beta2m into a ternary complex with mouse H-2Kd heavy chain and influenza nuclear protein peptide. Dissociation of the labeled beta2m from the ternary complex restored the probe's fluorescence and absorption spectra and reduced the emission intensity. Thus changes in xanthene probe fluorescence upon association/dissociation of the labeled beta2m molecule with/from the ternary complex provide a simple and convenient method for studying the assembly/dissociation mechanism of the class I major histocompatibility complex (MHC-I) encoded molecule. The photophysical changes in the probe can be accounted for by the oligomerization of free labeled beta2m molecules. The fluorescence at 610 nm is due to beta2m dimers, where the probes are significantly separated spatially so that their emission and excitation properties are close to those of xanthene monomers. Fluorescence around 630 nm is due to beta2m oligomers where xanthene probes interact. Minima in the steady-state excitation (550 nm) and emission (630 nm) anisotropy spectra correlate with the maxima of the high-order oligomer excitation and emission spectra, showing that their fluorescence is more depolarized. These photophysical features are explained by splitting of the first singlet excited state of interacting xanthene probes that can be modeled by exciton theory.  (+info)

Resolution of fluorescence correlation measurements. (4/2984)

The resolution limit of fluorescence correlation spectroscopy for two-component solutions is investigated theoretically and experimentally. The autocorrelation function for two different particles in solution were computed, statistical noise was added, and the resulting curve was fitted with a least squares fit. These simulations show that the ability to distinguish between two different molecular species in solution depends strongly on the number of photons detected from each particle, their difference in size, and the concentration of each component in solution. To distinguish two components, their diffusion times must differ by at least a factor of 1.6 for comparable quantum yields and a high fluorescence signal. Experiments were conducted with Rhodamine 6G and Rhodamine-labeled bovine serum albumin. The experimental results support the simulations. In addition, they show that even with a high fluorescence signal but significantly different quantum yields, the diffusion times must differ by a factor much bigger than 1.6 to distinguish the two components. Depending on the quantum yields and the difference in size, there exists a concentration threshold for the less abundant component below which it is not possible to determine with statistical means alone that two particles are in solution.  (+info)

Chemotactic responses of Escherichia coli to small jumps of photoreleased L-aspartate. (5/2984)

Computer-assisted motion analysis coupled to flash photolysis of caged chemoeffectors provides a means for time-resolved analysis of bacterial chemotaxis. Escherichia coli taxis toward the amino acid attractant L-aspartate is mediated by the Tar receptor. The physiology of this response, as well as Tar structure and biochemistry, has been studied extensively. The beta-2, 6-dinitrobenzyl ester of L-aspartic acid and the 1-(2-nitrophenyl)ethyl ether of 8-hydroxypyrene-1,3,6-tris-sulfonic acid were synthesized. These compounds liberated L-aspartate and the fluorophore 8-hydroxypyrene 1,3,6-tris-sulfonic acid (pyranine) upon irradiation with near-UV light. Photorelease of the fluorophore was used to define the amplitude and temporal stability of the aspartate jumps employed in chemotaxis experiments. The dependence of chemotactic adaptation times on aspartate concentration, determined in mixing experiments, was best fit by two Tar aspartate-binding sites. Signal processing (excitation) times, amplitudes, and adaptive recovery of responses elicited by aspartate jumps producing less than 20% change in receptor occupancy were characterized in photorelease assays. Aspartate concentration jumps in the nanomolar range elicited measurable responses. The response threshold and sensitivity of swimming bacteria matched those of bacteria tethered to glass by a single flagellum. Stimuli of similar magnitude, delivered either by rapid mixing or photorelease, evoked responses of similar strength, as assessed by recovery time measurements. These times remained proportional to change in receptor occupancy close to threshold, irrespective of prior occupancy. Motor excitation responses decayed exponentially with time. Rates of excitation responses near threshold ranged from 2 to 7 s-1. These values are consistent with control of excitation signaling by decay of phosphorylated pools of the response regulator protein, CheY. Excitation response rates increased slightly with stimulus size up to values limited by the instrumentation; the most rapid was measured to be 16 +/- 3 (SE) s-1. This increase may reflect simultaneous activation of CheY dephosphorylation, together with inhibition of its phosphorylation.  (+info)

Resolution of the paradox of red cell shape changes in low and high pH. (6/2984)

The molecular basis of cell shape regulation in acidic pH was investigated in human erythrocytes. Intact erythrocytes maintain normal shape in the cell pH range 6.3-7.9, but invaginate at lower pH values. However, consistent with predicted pH-dependent changes in the erythrocyte membrane skeleton, isolated erythrocyte membranes evaginate in acidic pH. Moreover, intact cells evaginate at pH greater than 7.9, but isolated membranes invaginate in this condition. Labeling with the hydrophobic, photoactivatable probe 5-[125I]iodonaphthyl-1-azide demonstrated pH-dependent hydrophobic insertion of an amphitropic protein into membranes of intact cells but not into isolated membranes. Based on molecular weight and on reconstitution experiments using stripped inside-out vesicles, the most likely candidate for the variably labeled protein is glyceraldehyde-3-phosphate dehydrogenase. Resealing of isolated membranes reconstituted both the shape changes and the hydrophobic labeling profile seen in intact cells. This observation appears to resolve the paradox of the contradictory pH dependence of shape changes of intact cells and isolated membranes. In intact erythrocytes, the demonstrated protein-membrane interaction would oppose pH-dependent shape effects of the spectrin membrane skeleton, stabilizing cell shape in moderately abnormal pH. Stabilization of erythrocyte shape in moderately acidic pH may prevent inappropriate red cell destruction in the spleen.  (+info)

Analysis of the membrane-interacting domains of myelin basic protein by hydrophobic photolabeling. (7/2984)

Myelin basic protein is a water soluble membrane protein which interacts with acidic lipids through some type of hydrophobic interaction in addition to electrostatic interactions. Here we show that it can be labeled from within the lipid bilayer when bound to acidic lipids with the hydrophobic photolabel 3-(trifluoromethyl)-3-(m-[125I]iodophenyl)diazirine (TID) and by two lipid photolabels. The latter included one with the reactive group near the apolar/polar interface and one with the reactive group linked to an acyl chain to position it deeper in the bilayer. The regions of the protein which interact hydrophobically with lipid to the greatest extent were determined by cleaving the TID-labeled myelin basic protein (MBP) with cathepsin D into peptides 1-43, 44-89, and 90-170. All three peptides from lipid-bound protein were labeled much more than peptides from the protein labeled in solution. However, the peptide labeling pattern was similar for both environments. The two peptides in the N-terminal half were labeled similarly and about twice as much as the C-terminal peptide indicating that the N-terminal half interacts hydrophobically with lipid more than the C-terminal half. MBP can be modified post-translationally in vivo, including by deamidation, which may alter its interactions with lipid. However, deamidation had no effect on the TID labeling of MBP or on the labeling pattern of the cathepsin D peptides. The site of deamidation has been reported to be in the C-terminal half, and its lack of effect on hydrophobic interactions of MBP with lipid are consistent with the conclusion that the N-terminal half interacts hydrophobically more than the C-terminal half. Since other studies of the interaction of isolated N-terminal and C-terminal peptides with lipid also indicate that the N-terminal half interacts hydrophobically with lipid more than the C-terminal half, these results from photolabeling of the intact protein suggest that the N-terminal half of the intact protein interacts with lipid in a similar way as the isolated peptide. The similar behavior of the intact protein to that of its isolated peptides suggests that when the purified protein binds to acidic lipids, it is in a conformation which allows both halves of the protein to interact independently with the lipid bilayer. That is, it does not form a hydrophobic domain made up from different parts of the protein.  (+info)

Photochemical internalization: a novel technology for delivery of macromolecules into cytosol. (8/2984)

The therapeutic usefulness of macromolecules, such as in gene therapy, is often limited by an inefficient transfer of the macromolecule to the cytosol and a lack of tissue-specific targeting. The possibility of photochemically releasing macromolecules from endosomes and lysosomes into the cytosol was examined. Endocytosed macromolecules and photosensitizer were exposed to light and intracellular localization and the expression of macomolecules in the cytosol was analyzed. This novel technology, named photochemical internalization (PCI), was found to efficiently deliver type I ribosome-inactivating proteins, horseradish peroxidase, a p21ras-derived peptide, and a plasmid encoding green fluorescent protein into cytosol in a light-dependent manner. The results presented here show that PCI can induce efficient light-directed delivery of macromolecules into the cytosol, indicating that PCI may have a variety of useful applications for site-specific drug delivery, e.g., in gene therapy, vaccination, and cancer treatment.  (+info)

  • The science-softCon UV/Vis + Photochemistry Database ( ) is a large and comprehensive collection of extended ultraviolet, vacuum ultraviolet, ultraviolet, visible and near infrared spectral data and other photochemical information assembled from published peer-reviewed papers. (
  • There are a number of key advantages of a continuous flow approach to photochemistry over a traditional batch method including consistent light penetration, controlled exposure times, precise temperature control and easy scalability as well as the removal of photochemical products from the irradiated area. (
  • The Solar Photochemistry core program at NREL, funded by the Office of Basic Energy Science, focuses on fundamental research of solar photoconversion in molecular, nanoscale, and semiconductor systems to capture, control, and convert solar radiation with high efficiency into electrochemical potential for electricity, chemicals, or fuels. (
  • Here, we assess the ability of TDDFT to describe the photochemistry of an important class of triplet sensitizers, namely, aromatic ketones. (
  • We show that most exchange-correlation functionals can only give a semi-qualitative picture of the overall photochemistry, in which the three-state crossing is rather represented as a triplet conical intersection separated from the intersystem crossing. (
  • The unique and easy-to-use design of the UV-150 gives access to photochemistry that is not readily available to most chemists. (
  • Microflow photochemistry combines successfully the benefits of microscopic dimensions and flow operation. (
  • This article gives an outline regarding the structure and content of the science-softCon UV/Vis + Photochemistry Database . (
  • Even though time-dependent density-functional theory (TDDFT) works generally well for describing excited states energies and properties in the Franck-Condon region, it can dramatically fail in predicting photochemistry, notably when electronic state crossings occur. (
  • 2 The UV/Vis + Photochemistry Database allows free and open access to all metadata, and cost-recovery pricing for data (or data licenses) in order to support the full data infrastructure. (
  • Browse our Scrabble Word Finder , Words With Friends cheat dictionary , and WordHub word solver to find words that end with photochemistry. (
  • Photochemistry is an interdisciplinary field drawing knowledge from various research areas within chemistry, materials science, physics and biology. (
  • Prof. Bahnemann has edited the volumes "Environmental Photochemistry Part II" and "Environmental Photochemistry Part III" of the Springer book series The Handbook of Environmental Chemistry . (
  • Photochemistry is an important area to study as it provides one very elegant way to generate short-lived (mostly free radical) intermediates through the absorption of one single photon the investigations of which yield important fundamental knowledge for the fields of chemistry, physics, and biology. (
  • Photochemistry is the branch of chemistry concerned with the chemical effects of light. (
  • Written as an authoritative guide for researchers involved in the development of bioinorganic photochemical processes, Bioinorganic Photochemistry is also accessible to scientists new to the field, and will be a key reference source for advanced courses in inorganic, and bioinorganic chemistry. (
  • The breadth of scientific and technological interests in the general topic of photochemistry is truly enormous and includes, for example, such diverse areas as microelectronics, atmospheric chemistry, organic synthesis, non-conventional photoimaging, photosynthesis, solar energy conversion, polymer technologies, and spectroscopy. (
  • This Specialist Periodical Report on Photochemistry aims to provide an annual review of photo-induced processes that have relevance to the above wide-ranging academic and commercial disciplines, and interests in chemistry, physics, biology and technology. (
  • Photochemistry of Simple Olefins: Chemistry of Electronic Excited States or Hot Ground States? (
  • Photochemistry is the branch of chemistry concerned with chemical reactions caused by Absorption of Visible Light , Ultraviolet (UV) , and Infrared (IR) . (
  • Although often thought to be a rare occurrence, the break down of the Born-Oppenheimer Approximation is actually common in chemistry and understanding the nature of this break down can be extremely useful in furthering research in areas such as photochemistry and solar energy conversion. (
  • Surface Water Photochemistry 1st Edition by Paola Calza and Publisher Royal Society of Chemistry. (
  • It includes tabular listings of reactants, products, yields, and references for all reactions, and the material is accessible to chemists with no special training in carbohydrate chemistry or photochemistry. (
  • This book stresses the interplay between radiation chemistry and photochemistry in studies of electron transfer. (
  • A PhD student position in the field of ultrafast photochemistry is open at the Department of Physical Chemistry, University of Geneva. (
  • Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science. (
  • This add-on module allows you to combine photochemistry with the benefits that flow chemistry offer. (
  • Advanced chemistry in a very mild and clean way, which immensely decreases the reaction time on photochemistry reactions and leads to highly pure products. (
  • Of particular interest to the photochemistry community are homogeneously catalyzed photochemical conversions including water splitting through photoexcited organometallic complexes as well as heterogeneous photocatalytic systems such as the ones studied in my own research teams in Hannover and Saint Petersburg. (
  • The photochemistry of some d6 metal carbonyl complexes is investigated. (
  • Mechanistic organic photochemistry is that aspect of organic photochemistry which seeks to explain the mechanisms of organic photochemical reactions. (
  • Bioinorganic Photochemistry provides a comprehensive overview of the concepts and reactions fundamental to the field, illustrating important applications in biological, medical and environmental sciences. (
  • We propose that this difference is due to peroxy radical photochemistry that leads to reactions typically found only in combustion mechanisms: direct peroxy radical isomerization and the reverse dissociation reaction that leads to a vibrationally excited parent molecule that can scramble the location of the radical site. (
  • The study of chemical reactions that proceed with the absorption of light by atoms or molecules is known as photochemistry. (
  • Nonlinear two-quantum excitation of biomolecules and water provides realization of chemical reactions with the dissolved molecules participating, and the products of such reactions differ qualitatively from those of classical linear photochemistry. (
  • In nature, photochemistry is of immense importance as it is the basis of photosynthesis, vision, and the formation of vitamin D with sunlight. (
  • The Biosphere Effects on AeRosols and Photochemistry Experiment (BEARPEX) was a multi-investigator collaboration conducted as two eight week deployments, August-October 2007 and June-July 2009. (
  • In the present study, the impact of aerosols on the photochemistry in Mexico City is evaluated using the WRF-CHEM model for the period from 24 to 29 March during the MCMA-2006/MILAGRO campaign. (
  • At the limits of modern photochemistry, methods are also appearing that can be used for studies of ultrafast relaxation in larger systems. (
  • The position is related to the SNF funded project of Dr. Tatu Kumpulainen and the work will be carried out in collaboration with the Ultrafast Photochemistry group of Prof. Eric Vauthey. (
  • Can you tell us about your research specifically that related to photochemistry? (
  • Is an interdisciplinary research text on the application of nanophotonic (physical/chemical) research and effects in devices for applications, bridging a gap between conventional pthotophysics/photochemistry and nanoscience.Nanophotonics. (
  • Is an interdisciplinary research text on the application of nanophotonic (physical/chemical) research and effects in devices for applications, bridging a gap between conventional pthotophysics/photochemistry and nanoscience. (
  • In the decade after this book first appeared in 1974, research involving organic photochemistry was prolific. (
  • The goal of the Asymmetric Catalysis and Photochemistry Research Line is to develop new general catalysis concepts and applying them to the synthesis of complex molecules and pharmaceuticals. (
  • Brouwer, who also heads the Nanophotochemistry research group at ARCNL, received the award for his significant contributions to the photochemistry research field. (
  • Lifetime estimates using extrapolated ethyl peroxy absorption cross sections and the actinic flux near 310 nm show that peroxy radical photochemistry can play a significant role in defining the product spectrum of secondary organic aerosol in pristine (low-NOx) environments. (
  • Here, the wavelength-dependent photochemistry of vinylneoxanthobilirubic acid methyl ester, a simplified model of a bilirubin dipyrrinone subunit responsible for a lumirubin-like structural rearrangement, was thoroughly investigated by liquid chromatography and mass and absorption spectroscopies, with the application of a multivariate curve resolution analysis method supplemented with quantum chemical calculations. (
  • Photochemistry in continuous flow offers multiple advantages over its batch-wise analogue. (
  • According to the second law of photochemistry, known as the Stark-Einstein law (for physicists Johannes Stark and Albert Einstein), for each photon of light absorbed by a chemical system, no more than one molecule is activated for a photochemical reaction, as defined by the quantum yield. (
  • Here, we assess the ability of TDDFT to describe the photochemistry of an important class of triplet sensitizers, namely, aromatic ketones. (
  • This article gives an outline regarding the structure and content of the science-softCon UV/Vis + Photochemistry Database . (
  • Even though time-dependent density-functional theory (TDDFT) works generally well for describing excited states energies and properties in the Franck-Condon region, it can dramatically fail in predicting photochemistry, notably when electronic state crossings occur. (
  • The book concludes with an outlook for the future of environmental protection, discussing emerging techniques in the field of pollution abatement, and the potential for bioinorganic photochemistry as a pathway to developing cheap, environmentally friendly sources of energy. (
  • The book is written by experts in the field of photochemistry, optics, material science, bioscience, and so on for providing advanced knowledge of nanophotonics. (
  • Within the last 10 years, photochemistry has begun to be used in the field of dental materials for the photocuring of methacrylate monomers. (
  • In the broad field of chemical reactivity, a discipline that has grown with an extraordinary rate is photochemistry. (
  • The above demonstration is just that, a demonstration, and is not meant to offend experts in the field of photography and photochemistry. (
  • Among the most recent avenues being pursued is photochemistry at adsorbate-metal interfaces where bond breaking within the adsorbate, surface rearrangement, reaction with coadsorbates, and adsorbate desorption have all been observed in systems where thermal effects can be ruled out. (
  • Also hear from leading expert Professor Detlef Bahnemann about the latest trends in photochemistry and what the future holds. (
  • This thesis focuses on the photochemistry of heteroaromatic biomolecules. (
  • Two-Quantum Photochemistry (Nauka, Moscow, 1976). (