TY - JOUR. T1 - Kinetics of the Reaction of Electron Deficient Olefins with Nitrile Ylides Generated by Laser Flash Photolysis of Substituted Azirines. AU - Turro, Nicholas J.. AU - Hrovat, David A.. AU - Gould, Ian. AU - Padwa, Albert. AU - Dent, William. AU - Rosenthal, Robert J.. PY - 1983. Y1 - 1983. UR - http://www.scopus.com/inward/record.url?scp=84985545765&partnerID=8YFLogxK. UR - http://www.scopus.com/inward/citedby.url?scp=84985545765&partnerID=8YFLogxK. U2 - 10.1002/anie.198306252. DO - 10.1002/anie.198306252. M3 - Article. AN - SCOPUS:84985545765. VL - 22. SP - 625. EP - 627. JO - Angewandte Chemie - International Edition. JF - Angewandte Chemie - International Edition. SN - 1433-7851. IS - 8. ER - ...
60]Fullerene is oxidized to its radical cation at preparative scale by means of photoinduced electron transfer (PET). In general, C-60(.+) reacts with various H-donors such as alcohols, aldehydes, ethers etc., under formation of 1,2-dihydro[60]fullerenes. In case of tert-butanol, propionic acid and glycol, for example, product formation is also initiated by H-abstraction from the OH group. Both time-resolved laser flash photolysis studies and ESR spectroscopic investigations clearly demonstrate the formation of C-60(.+) using PET conditions. Upon addition of H-donors such as methanol the signal of C-60(.+) is quenched as monitored both by laser flash photolysis and ESR spectroscopy. Based on these studies we assume the oxidation of C-60 followed by abstraction of hydrogen from the H-donor ...
Effects of four photodegradation products of nifedipine (nitroso-, nitro-, azoxy- and N,N-dioxide-derivatives) were studied in the rat aortic strip suspended in the bath medium. In the CaCl2-free bath medium containing 40 mM KCl, CaCl2 (2.5 mM) induced contraction, which was relaxed by nifedipine (-log [EC50] = 8.66 M) and all the four photodegradation products (-log[EC50] = 4.15-4.82 M). The EC50 values for all these substances were not affected by denuding the vessel of endothelium. In the bath medium containing KCl (15 mM), Bay K-8644 (2 x 10(-6) M) induced contraction, which was relaxed by nifedipine (10(-9)-10(-6) M) and its four photodegradation products (3 x 10(-6)-10(-4) M). Norepinephrine (10(-7) M) induced contraction, which was relaxed by the nitroso-derivative (10(-4) M) noncompetitively (pIC50 = 4.37) but not by three other photodegradation products. Both methylene blue and hemoglobin had no effect on the relaxation produced by the nitroso-derivative. Phorbol 12-myristate ...
Rate constants for quenching of triplet sensitizers by several alkyl peroxides were measured by laser flash photolysis in benzene solution. Because these rate constants decrease monotonically with sensitizer triplet energy, electronic energy transfer is concluded to be the likely quenching mechanism. A rough correlation exists between quenching rate constants and peroxide thermal lability. Finally, the computer interfaced laser flash photolysis apparatus which was used in these measurements is described in detail ...
1J3Y: Direct observation of photolysis-induced tertiary structural changes in human hemoglobin; Crystal structure of alpha(Fe)-beta(Ni) hemoglobin (laser photolysed)
TY - JOUR. T1 - Photolysis of indomethacin in methanol. AU - Wu, An-Bang. AU - Cheng, Hui Wen. AU - Hu, Chien-Ming. AU - Chen, Fu An. AU - Chou, Tzu Chang. AU - Chen, Chau Yang. PY - 1997/1/27. Y1 - 1997/1/27. N2 - A novel photo-oxidation product containing a six-membered 1,2-dioxane ring was isolated from the photolysis of indomethacin in methanol and a possible mechanism is proposed.. AB - A novel photo-oxidation product containing a six-membered 1,2-dioxane ring was isolated from the photolysis of indomethacin in methanol and a possible mechanism is proposed.. UR - http://www.scopus.com/inward/record.url?scp=0031034669&partnerID=8YFLogxK. UR - http://www.scopus.com/inward/citedby.url?scp=0031034669&partnerID=8YFLogxK. U2 - 10.1016/S0040-4039(96)02379-9. DO - 10.1016/S0040-4039(96)02379-9. M3 - Article. AN - SCOPUS:0031034669. VL - 38. SP - 621. EP - 622. JO - Tetrahedron Letters. JF - Tetrahedron Letters. SN - 0040-4039. IS - 4. ER - ...
Imatinib (IMT) is a promising tyrosine kinase inhibitor used in the treatment of some types of human cancer. It constitutes a successful example of rational drug design based on the optimization of the chemical structure to reach an improved pharmacological activity. Cutaneous reactions, such as increased photosensitivity or pseudoporphyria, are among the most common nonhematological IMT side effects; however, the molecular bases of these clinical observations have not been determined. Thus, to gain insight into the IMT photosensitizing properties, we addressed its photobehavior together with that of its potentially photoactive anilino-pyrimidine and pyridyl-pyrimidine fragments. In this context, steady-state and time-resolved fluorescence as well as laser flash photolysis experiments have been conducted, and the DNA photosensitization potential has been investigated by means of single-strand break detection using agarose gel electrophoresis. The obtained results reveal that the drug itself and ...
Slice preparation. Brain slices were prepared as described previously (Aghajanian and Marek, 1997) and in adherence with protocols approved by the University of California, Irvine Institutional Animal Care and Use Committee. All efforts were made to minimize the number of animals used and their suffering. Briefly, 2.5- to 3.5-week-old FVB/N mice were deeply anesthetized with halothane and decapitated. The brains were quickly removed and placed in ice-cold artificial CSF (aCSF) bubbled with 95%O2-5% CO2. A 300-μm-thick coronal section containing the prefrontal cortex was blocked and glued to the stage of a Vibroslice (Campden Instruments, Loughborough, UK) oscillating microslicer. The standard aCSF used in the recording chambers was composed of the following (in mm): 125 NaCl, 2.5 KCl, 1.25 NaH2PO4, 10d-glucose, 25 NaHCO3, 2 CaCl2, and 1.2 MgSO4, pH 7.3-7.4. Flow rate for aCSF was ∼3 ml/min. There was at least a 1 hr recovery period before the initiation of experiments. Layer V pyramidal ...
Photolysis of mono and di-carboxylic acids that are adsorbed onto the surface of the iron oxyhydroxide (goethite) results in an oxidation of the organic material and a reduction from Fe(III) to Fe(II) in the iron complex. There is a subsequent release of Fe2+ ions into solution. At constant light flux and constant solution light absorption, the factors responsible for the degree of photolytic reaction include: the number of lattice sites that are bonded by the organic acid; the rate of acid readsorption to the surface during photolysis; the conformation and structure of the organic acid; the degree of oxidation of the organic acid; the presence or absence of an ??-hydroxy group on the acid, the number of carbons in the di-acid chain and the conformation of the di-acid. The ability to liberate Fe(III) at pH 6.5 from the geothite lattice is described by the lyotropic series: tartrate|citrate| oxalate | glycolate...
... ,The ARC Laser MISC combines a pharo unit + Lyla laser module = Photolysis.,medicine,medical supply,medical supplies,medical product
Molecular oxygen was used to probe the mechanism of the phototransformation of chlorobenzene and 4-chloroanisole in organic solvents. Laser flash photolysis, electron paramagnetic resonance and product distribution studies clarified the reaction mechanisms of these compounds under a wide range of conditions. The main primary photochemical reaction step is the homolytic cleavage of the C-Cl bond to produce a triplet radical pair in the solvent cage. In non-polar solvents hydrogen abstraction, after radical diffusion, leads to reduction. In polar solvents, in addition to H-abstraction, electron transfer within the caged radical pair occurs and leads to an ion pair (phenyl cation and Cl-). In the presence of oxygen, phenyl radicals can form phenylperoxyl radicals which have a bathochromically shifted absorption, thus making the homolytic cleavage visible by flash photolysis. The peroxyl radicals can couple, leading to more polar compounds, or undergo back reaction to the phenyl radical. For concentrations
The recombination of I atoms after laser flash photolysis was studied in the presence of NO or NO2 at 320-450 DegK and 0-200 atm of He. The reaction proceeds in 2 stages. The 1st stage is governed by the recombination I + NO (+He) -, INO (+He) or I + NO2 (+He) -, INO2 (+He), for which the full falloff curves are derived. The 2nd stage is governed either by reaction between 2 INO (or INO2) mols., or, at higher temps., by thermal decompn. of INO (or INO2). The reaction involves the elementary steps of a typical intermediate complex mechanism of atom recombination. The rates of all of these elementary steps can be sepd. From the I + NO .dblarw. INO and I + NO2 .dblarw. INO2 equil. consts. the enthalpies of formation of INO and INO2 of DHf0298(INO) = 29.0 +- 1 kcal mole-1 and DHf0298(INO2) = 14.4 +- 1 kcal mole-1, resp., are derived.. Keywords: 15465-40-4P ; 58585-94-7P Role: PREP (Preparation) (formation and reactions of ; kinetics and thermodn. of) ; 10102-43-9 ; 10102-44-0 Role: RCT (Reactant) ; ...
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Instrumentation is used in the undergraduate chemistry curriculum to help demonstrate the fundamental aspects of chemical reactions and demonstrate how it can be used to determine certain properties of a chemical system. For example, absorbance spectroscopy teaches students about transmission and absorption of radiation by a compound and how these measurements can be used to determine concentration or chemical reaction order. Chromatography illustrates to students how the structure of compounds can help isolate them from others. When certain techniques are coupled together, the concepts are layered and even more can be learned about the system being studied.
CNBCs Brian Sullivan reports the largest oil refinery in the United States is shuttng down as other refineries decide to go offline as well.
Desensitization of μ-opioid receptors (MORs) develops over 5-15 min following application of some but not all opioid agonists and lasts for 10s of min following agonist removal. The decrease in function is receptor selective (homologous) and could result from (1) a reduction in receptor number or (2) a decrease in receptor coupling. The present investigation used photolysis of two caged opioid ligands in order to examine the kinetics of MOR-induced potassium conductance before and following MOR desensitization. Photolysis of a caged antagonist, caged-naloxone (CNV-NLX), blocked the current induced by a series of agonists and the time constant of decline was significantly decreased following desensitization. The increase in the rate of current decay was not observed following partial blockade of receptors with the irreversible antagonist, β-CNA. The time constant of current decay following desensitization was never more rapid than 1s, suggesting an increased agonist off rate rather than an ...
A layered construction for use in decontaminating a surface or enclosed space is described. The construction is an electrochemical cell which includes a cathode, an electrolyte layer, an anode and a protective surface layer. A precursor compound that can be electrically decomposed to release an oxidant, on demand and over an extended period of time, is included in the layered structure, preferably in the electrolyte layer. The oxidant compounds react with various different chemical or biological contaminants in contact the protective layer, thereby deactivating, destroying or devitalizing the contaminants. The layered construction is suitable for application to a device or substrate, or placement in an enclosed space, and can be used on sensitive surfaces such as electronic components and human skin.
Abstract The photodegradation of the herbicides atrazine and ametryn with visible light in aerated neutral aqueous solutions and 5, 10, 15, 20-tetrakis (2,6-dichloro-3-sulfophenyl) porphyrin or 5, 10, 15, 20-tetrakis (4-sulfophenyl) porphyrin as sensitizers are reported for the first time. Our findings show that the degradation percentage reached 30% for atrazine and 63% for ametryn. The final photoproducts were characterized as dealkylated s-triazines. Photolysis of the pesticides in the presence of a singlet oxygen quencher showed only a minor contribution of this type of mechanism, while a bimolecular quenching reaction between the triplet state of the sensitizer and the pesticides is excluded by flash photolysis studies. It is proposed that the mechanism may involve the formation of a superoxide radical anion from the triplet state of the sensitizer and molecular oxygen, followed by a radical decomposition pathway ...
In this research intermolecular and intramolecular triplet sensitization has been employed to photochemically generate triplet alkyl nitrene intermediates in solution. Photolyzing with light greater than 300 nm assures that only the ketone chromophore is exclusively excited to its triplet excited state. Once generated, the ketone can transfer its triplet energy to the azide moiety which loses molecular nitrogen to give a triplet alkyl nitrene intermediate. Intermolecular triplet sensitization in solution allowed trapping of triplet alkyl nitrene intermediates via bimolecular reactions. Photolysis of 1-azidoadamantane in solution with acetophenone, benzophenone and acetone led to an azo-dimer as the major product. This product comes from dimerization of two triplet alkyl nitrenes. Intermolecular sensitized photolysis of benzyl azide led to N-methyleneaniline as the major photoproduct with acetophenone as the triplet sensitizer. With benzophenone as the triplet sensitizer the major product was ...
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5The sEPSC was not blocked by Cd2+, Co2+, Mg2+ or Gd3+ ions, by the inhibitor of hyperpolarisation-activated current (IH) ZD7288, or by the purinoceptor inhibitor PPADS. Activation was not affected by inhibitors of phospholipase C (PLC) or protein kinase C (PKC), nor mimicked by photorelease of InsP3 or Ca2+. The results show that mGluR1 in PNs produces a slow activation of cation-permeable ion channels which is not mediated by PLC activation, Ca2+ release from stores, or via the activation of PKC ...
Photolysis of r-1,c-2,t-3,t-4-tetraphenylcyclobutane: quantum yield determinations via high performance liquid chromatography | R.B. Frings; W. Schnabel | download | BookSC. Download books for free. Find books
Infrared and ultraviolet-visible absorption cross-sections, effective quantum yields of photolysis and OH reaction rate coefficients for CFCHO and CFCHCHO are reported. Relative rate measurements at 298(2) K and 1013(10) hPa, give (OH + CFCHO)/(OH + CHCH) = 2.00(13), (OH + CFCHCHO)/(OH + CHCHOH) = 1.21(5) and (OH +
0028]Sensitizers can be incorporated into the shells of capsules formed from non-cross linked polymers, crosslinked polymers, lipids, anionic lipids, crosslinkable synthetic lipids, block copolymers, inorganic capsules, and combinations thereof. A wide variety of sensitizers with high absorption cross-sections (both fluorescent and non-fluorescent), can be incorporated into the shells of the capsules to allow for spectrally tunable photolysis. In addition, these sensitizers can be incorporated onto the surface of the shell or interior of the capsule. Typical sensitizers useful in capsules of the invention include carbocyanine-based dyes, rhodamine-based dyes, fluorescein-based dyes, various non-fluorescent dyes, neutral dyes, zwitterionic dyes, positively-charged dyes, negatively-charged dyes, reactive dyes, tagged dyes that contain an antibody, and combinations thereof. In one embodiment, the sensitizer is 1,1-dioctadecyl-3,3,3,3,-tetramethylindodicarbocyanine, 4-chlorobenzenesulfonate salt ...
1990) TUNGSTEN(VI) COMPLEXES AS NEW PRODUCTS IN THE HIGH-INTENSITY PHOTOLYSIS OF OCTACYANOTUNGSTATE(V) ION IN HYDROXYLIC SOLVENTS - CRYSTAL-STRUCTURE OF [PPH4]2[W(CN)6O].H2O AND [PPH4]2[W(CN)5O(OME)]. JOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS (8). pp. 2331-2336 ...
TY - JOUR. T1 - Rate constants of sulfate radical anion reactions with organic molecules. T2 - A review. AU - Wojnárovits, L.. AU - Takács, E.. PY - 2019/4/1. Y1 - 2019/4/1. N2 - The rate constants of sulfate radical anion reaction (kSO4[rad]−) with about 230 organic molecules of environmental interest are tabulated and discussed, together with both the methods of rate constant determinations and the reaction mechanisms. kSO4[rad]−s were collected from the original publications. The highest values in the ∼109 M−1 s−1 range are published for aromatic molecules. There is a tendency that electron donating substituents increase and electron withdrawing substituents decrease these values. There are just a few compounds with rate constants established using different techniques in different laboratories. kSO4[rad]−s determined in different laboratories by the direct techniques, pulse radiolysis or laser flash photolysis, in most cases agree reasonably. The values determined by ...
Bartl, Joerg; Steenken, S.; Mayr, Herbert und McClelland, R. A. (1990): Photo-heterolysis and -homolysis of substituted diphenylmethyl halides, acetates, and phenyl ethers in acetonitrile: characterization of diphenylmethyl cations and radicals generated by 248-nm laser flash photolysis. In: Journal of the American Chemical Society, Vol. 112, Nr. 19: S. 6918-6928 ...
The building blocks of intracellular Ca2+ signals evoked by inositol 1,4,5-trisphosphate receptors (IP3Rs) are Ca2+ puffs, transient focal increases in Ca2+ concentration that reflect the opening of small clusters of IP3Rs. We use total internal reflection fluorescence microscopy and automated analyses to detect Ca2+ puffs evoked by photolysis of caged IP3 or activation of endogenous muscarinic receptors with carbachol in human embryonic kidney 293 cells. Ca2+ puffs evoked by carbachol initiated at an estimated 65±7 sites/cell, and the sites remained immobile for many minutes. Photolysis of caged IP3 evoked Ca2+ puffs at a similar number of sites (100±35). Increasing the carbachol concentration increased the frequency of Ca2+ puffs without unmasking additional Ca2+ release sites. By measuring responses to sequential stimulation with carbachol or photolysed caged IP3, we established that the two stimuli evoked Ca2+ puffs at the same sites. We conclude that IP3-evoked Ca2+ puffs initiate at numerous
Our current research is both basic and applied. Our basic research is concerned with fundamental aspects of the mechanism of protein folding. A series of novel techniques have been developed to study the dynamics of fast processes in protein folding. These include the use of nanosecond pulsed lasers to trigger and monitor the folding reaction, as well as single molecule fluorescence measurements. Simple theoretical models are used to interpret the experimental results and expose the basic underlying physics of these processes. The experimental results and theoretical modeling are providing critical benchmarks for the construction of a detailed picture of the sequence of events as a protein forms its native conformation from the random structures of the unfolded polypeptide chain. A highly sensitive and pathophysiologically-relevant kinetic assay has been developed to screen compounds for ant-sickling activity. The assay uses laser photolysis to induce sickling and automated image analysis to ...
Akos spent a period of six weeks in Kiel (November to December of 1999). He was involved in our studies of the SiH3 oxidation kinetics with the laser photolysis - flow tube - quadrupole mass spectrometer combination. He also assisted in the set-up of a long path UV absorption cell. Akos came back to Kiel in 2000.. ...
Sometimes when a photon hits a molecule, the energy from the photon causes the molecule to break apart. Scientists use the term "photodissociation" for such events. Photodissociation plays a very important role in the chemistry of planetary atmospheres, including atmospheric chemistry here on Earth.. Photons of visible light can cause the photodissociation of some molecules. However, ultraviolet photons are even more likely to shatter molecular bonds because they carry more energy. The bonds between atoms within a molecule have characteristic strengths. For example, the triple bond of molecular nitrogen (N2) is stronger than the double bond of molecular oxygen (O2). This means that the bond between nitrogen atoms in N2 is harder to break, so a higher-energy photon is required to photodissociate N 2 than is the case for O2. Each such bond has a corresponding energy level that a photon must minimally carry to break that bond. If a photon carries more energy than the minimum required to break a ...
Principal Investigator:KOIKE Makoto, Project Period (FY):1995 - 1996, Research Category:Grant-in-Aid for Scientific Research (A), Section:試験, Research Field:Space and upper atmospheric physics
Hydrogen is the most plentiful gas in the universe and having only one proton, it is the simplest element known to man. As a gas, hydrogen is lighter
A structurally constrained derivative of 4′,7-dihydroxyflavylium was studied in aqueous solution and in CTAB micelles by pH jumps, flash photolysis and continuous irradiation with spectroscopic details assessed as well by theoretical calculations. In water, up to pH = 8, the compound shows only acid base che
Photodegradation caused by the ultraviolet portion of terrestrial solar radiation has been studied extensively.1-6Polymer photodegradation has been examined mainly through changes in various...
Rapid concentration jumps of Ins(1,4,5)P3 or ATP were made inside Limulus ventral photoreceptors by flash photolysis of the parent caged compounds. In intact ventral photoreceptors, the photolysis flash evokes a maximum amplitude light-activated current; therefore, a procedure was developed for uncoupling phototransduction by blocking two of the initial reactions in the cascade, rhodopsin excitation and G protein activation. Rhodopsin was inactivated by exposure to hydroxylamine and bright light. This procedure abolished the early receptor potential and reduced the quantum efficiency by 325 +/- 90-fold (mean +/- SD). G protein activation was blocked by injection of guanosine-5-O-(2-thiodiphosphate) (GDP beta S). GDP beta S injection reduced the quantum efficiency by 1,881 +/- 1,153-fold (mean +/- SD). Together hydroxylamine exposure and GDP beta S injection reduced the quantum efficiency by 870,000 +/- 650,000-fold (mean +/- SD). After the combined treatment, photoreceptors produced quantum ...
United States Patent Richard B. Hartman White Bear Lake; George H. Smith, Maplewood, both Minn. 857,552 Sept. 12, 1969 Nov. 2, 1971 Minnesota Mining and Manufacturing Company Saint Paul, Minn. [72] Inventors [21 Appl. No. [22] Filed [45] Patented [73] Assignee [54] PROPENONE SENSITIZERS FOR THE PHOTOLYSIS OF ORGANIC HALOGEN COMPOUNDS 8 Claims, No Drawings 52 us. Cl 96/90, [51] Int. Cl G03c 1/60, G030 1/72 [50] Field of Search 96/90, 88, 48,115 P, 35.1, 73, 74, 65, 66.3, 99, 100, 1.3, 1.5 [56] References Cited UNITED STATES PATENTS 3,081,165 3/1963 Ebert 96/l.3 3,374,094 3/1968 Wainer 96/90 X Primary Examiner-John T. Goolkasian Assistant Examiner-M. E. McCamish Attorney-Kinney, Alexander, Sell, Steldt & De La Hunt ABSTRACT: Photosensitive compositions containing nonbasic propenone compounds as sensitizers for photolyzable organic halogen compounds, and image recording elements in which at least one layer contains such photosensitive compositions. PROPENONE SENSITIZERS FOR THE PHOTOLYSIS OF ...
The radical cation and the two lowest excited singlet Rydberg states of DABCO (1,4-diazabicyclo[2.2.2]octane) are studied. Experimentally, the radical cation of DABCO is generated by either laser flash photolysis in solution at room temperature or by gamma-irradiation in a Freon glass at 77 K, and its electronic absorption and resonance Raman spectra in these two media are reported. The present resonance Raman spectra differ substantially from previous reports given in the Literature, and it is concluded that a number of bands attributed previously to the DABCO radical cation are due to other species. Theoretically, the absorption and resonance Raman spectra are interpreted on the basis of density functional theory (DFT; B3LYP/6-31G(d)) calculations and wave packet propagation methods. The same DFT calculations are used to interpret excitation and multiphoton ionization spectra of the two lowest singlet Rydberg states, making use of the close similarity between a Rydberg state and its ionic ...
In 1967, Norrish and Porter were honoured with Nobel prize for their seminal work on understanding the fast chemical reactions using flash photolysis technique.1 Since then benzophenone (Bzp) serves as an archetypal system for understanding the photochemistry of various aromatic ketones. Aromatic ketones find their use in various technologically significant applications like sunscreen, photocatalysis, etc., apart from their fundamental interest.2 Efficacy of aromatic ketones for use in various applications relies upon their photophysics and photochemistry. Therefore, understanding the photophysics and photochemistry of Bzp has attracted several experimental and theoretical investigations.2 Despite these myriads of investigations, pathways for populating the lowest triplet state (T1) after photoexcitation to the S1 state remains still elusive. There are two plausible pathways: i) a direct ISC from S1(nπ*) to T1(nπ*); or ii) an indirect process, involving ISC from S1(nπ*) to T1(ππ*) with ...
Publications. "Production of a Putative Iron(V) Oxo Corrole Species by Photo-Disproportionation of a bis-Corrole Diiron(IV) m-Oxo Dimer; Implication for a Green Oxidation Catalyst" Dilusha Harischandra, Gerald Lowery, Rui Zhang, Martin Newcomb, Organic Letters, 2009, accepted for publication.. "Formation of Stable and Metastable Porphyrin- and Corrole-Iron(IV) Complexes and Isomerozations to Iron(III) Macrocyclic Radical Cation" Zhengzheng Pan, Dilusha N. Harischandra, Martin Newcomb, Journal of Inorganic Biochemistry. 2008, 103,174-181.. "Laser Flash Photolysis Production of Metal-Oxo Derivatives and Direct Kinetic Studies of Their Oxidation Reactions", Martin Newcomb, Rui Zhang, Zhengzheng Pan, Dilusha N. Harischandra, R. Esala P. Chandrasena, John H. Horner, Enrique Martinez II, Catalysis Today. 2006, 117, 98-104. "Photochemical Generation of a Highly Reactive Iron-Oxo Intermediate. A True Iron(V)-Oxo Species?", Dilusha N. Harischandra, Rui Zhang, Martin Newcomb, J. Am. Chem. Soc. 2005, 127, ...
Aqueous solutions of isovaline and its precursor molecule, 5-ethyl-5-methylhydantoin, were irradiated with ultraviolet and γ-ray photons, to evaluate their structural stability against space radiation. The degree of photolysis was measured and irradiation products were identified using chiral, reversed-phase and ion-exchange high-performance liquid chromatography. The experimental results show that the degree of photolysis of 5-ethyl-5-methylhydantoin is more significant than that of isovaline under ultraviolet light irradiation, while the results under γ-ray irradiation are the opposite. As the products of isovaline photolysis, aspartic acid, serine, glutamic acid and alanine were dominantly detected.
The light dependent stages of photosynthesis take place in the thylakoid membranes. Photosystems containing photosynthetic pigments are embedded in the membrane. These pigments trap light energy that can be converted into chemical energy in the form of ATP. 1. When a photon of light strikes PS II it excites an electron. A water molecule binds to an enzyme on PS II. 2. The excited electrons leave the PS and are passed onto the electron chain. The water molecule is split. This is called photolysis. 3. The oxygen produced from photolysis diffuses out of the plant through the stroma. The electrons produced from photolysis are used to replace those lost by PS II. 4. As each protein in the electron chain is reduced, protons are pumped across the thylakoid membrane from the stroma into the thylakoid space. This creates a proton gradient across the membrane. 5. The thylakoid membrane is impermeable to protons. Therefore the protons diffuse back into the stroma via ATP synthase enzymes. 6. Molecules of ...
Fig. 62: 1.8 Å resolution electron density maps determined at from Laue diffraction data. For clarity, the electron density shown is confined to a 6.5 Å slab through the heme. The photolysed maps are coloured green and the unphotolysed maps are coloured magenta. Where both densities overlap, they blend to white. A white stick model of the unphotolysed structure is included to guide the eye. The direction of molecular motion follows the magenta to green colour gradient. (a) Three large scale displacements near the CO-binding site (large arrows) are accompanied by more subtle correlated rearrangements throughout the entire protein (small arrows; not drawn to scale). (b-g) Enlarged views of the boxed region in panel (a) at time delays specified in the lower left of each panel. (b) Upon photolysis, the bound CO (magenta; site 0) dissociates and becomes trapped approximately 2 Å away in a docking site (green; site 1), close to the Phe29. To accommodate the docked CO, the Phe29 is displaced and ...
Golka, Leonie; 2019: Kinetische Untersuchungen zur Pyrolyse oxygenierter Kohlenwasserstoffe: Stoßwellenexperimente und kinetische Modellierungen. Jöckle, Philipp; 2019: Visible light-triggered precursor molecules: relating reactivity and ultrafast dynamics. Schweigert, Caroline; 2018: Untersuchungen Lokaler Umgebungsvariation auf das Relaxationsverhalten Photoangeregter Zustände von Molekülen in Lösung Mittels Femtosekunden-Breitband-Absorptionsspektroskopie. Janzer, Corina; 2017: NO2-Bildung unter Motorischen Bedingungen: Kinetische Modellierungen und Stoßwellenexperimente. Weber, Isabelle; 2017: Kinetic Studies with Shock Tubes: Instrumental Developments and the Thermal Decompostiion of Furan Derivatives. Eble, Julia; 2017: Zündung oxygenierter Kohlenwasserstoffe: Mechanismus und Elementarschritte. Bänsch, Cornelie; 2017: Reactions of Hydroxyl Radicals with Oxygenated Hydrocarbons in the Gas Phase: A Laser Photolysis/Laser-Induced Fluorescence Study. Kiecherer, Johannes; 2016: ...
In this project the photodegradation of 3,5-diamino-6-chloro-N-(2-(methylamino)ethyl)pyrazine-2-carboxamide was studied. A hypothetical degradation pattern for the compound was proposed and the aim of the project was to study the formed secondary photodegradants and to, if possible, structure elucidate some of these compounds. In order to do this, the parent compound was photodegraded in two steps, where a primary photodegradant was isolated using semi-preparative supercritical fluid chromatography (SFC) and then further degraded into the secondary photodegradants.. The photodegradation was first carried out in aqueous solution, where the parent compound was irradiated in UV-A light of 300-400 nm. This resulted in a primary photodegradant with a molecular ion of m/z = 227, where the chloride in position 6 of the pyrazine group had been replaced by a hydroxyl group. During the large scale photodegradation, prior to the preparative purification, the yield of primary photodegradant was very low due ...
George Paul Hess George Paul Hess, professor emeritus of biochemistry at Cornell University, passed away at his home in Ithaca, N.Y., in September. He was 92. Hess was born in Vienna, Austria, and moved to the United States as a teenager. He completed his undergraduate and doctoral studies in biochemistry at the University of California, Berkeley, and did postdoctoral training in chemistry at the Massachusetts Institute of Technology. In 1955, Hess joined Cornell Universitys molecular biology and genetics department, where he would work for more than 50 years. Hess research focused on the structure and function of membrane-bound proteins that regulate communication between cells in the nervous system. He led a research group that developed new methods of exploring these proteins including a laser-pulse photolysis method and light-activated neurotransmitters.. Highly respected for his research acumen, Hess was a John S. Guggenheim fellow, a Fulbright senior research scholar and a recipient of ...
TY - JOUR. T1 - Competition for electrons between mono-oxygenations of pyridine and 2-hydroxypyridine. AU - Yang, Chao. AU - Tang, Yingxia. AU - Xu, Hua. AU - Yan, Ning. AU - Li, Naiyu. AU - Zhang, Yongming. AU - Rittmann, Bruce. PY - 2018/5/21. Y1 - 2018/5/21. N2 - Pyridine and its heterocyclic derivatives are widely encountered in industrial wastewaters, and they are relatively recalcitrant to biodegradation. Pyridine biodegradation is initiated by two mono-oxygenation reactions that compete for intracellular electron donor (2H). In our experiments, UV photolysis of pyridine generated succinate, whose oxidation augmented the intracellular electron donor and accelerated pyridine biodegradation and mineralization. The first mono-oxygenation reaction always was faster than the second one, because electrons provided by intracellular electron donors were preferentially utilized by the first mono-oxygenase; this was true even when the concentration of 2HP was greater than the concentration of ...
The direct photolysis of an organic molecule occurs when it absorbs sufficient light energy to result in a structural transformation. The absorption of light in the ultra violet (UV)-visible range, 110-750 nm, can result in the electronic excitation of an organic molecule. The stratospheric ozone layer prevents UV light of less than 290 nm from reaching the earths surface. Therefore, only light at wavelengths between 290 and 750 nm can result in photochemical transformations in the environment. A conservative approach to estimating a photochemical degradation rate is to assume that degradation will occur in proportion to the amount of light wavelengths ,290 nm absorbed by the molecule. This substance contains hydrocarbon molecules that absorb UV light below 290 nm, a range of UV light that does not reach the earths surface. Therefore, this substance does not have the potential to undergo photolysis in water, and this fate process will not contribute to a measurable degradative loss of this ...
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There are only so many ways that you can "clean" air of particles and volatile organic chemicals (VOC), bacteria, virus and mould. In general these include: • Filtration • Adsorption • Ionization to generate charged particles • Photolysis to generate free radicals Removing particles from air requires the use of high performance filters, which are […]. ...