Photochemical characterization

Wang, W. W., Sineshchekov, O. A., Spudich, E. N., and Spudich, J. L. (2003). Spectroscopic and photochemical characterization of a deep ocean proteorhodopsin.J. Biol. Chem. 36, 33985-33991. Waterbury, J. B., and Valois, F. W. (1993). Resistance to co-ocuring phages enables marine Synecho-cocus communities to coexist with cyanophages abundant in seawater. Appl. Environ. Microbiol. 59,... 

Bosca, F., Encinas, S., Heelis, P.F., and Miranda, M.A. (1997) Photophysical and photochemical characterization of a photosensitizing drug a combined steady state photolysis and laser flash photolysis study on carprofen, Chem. Res. Toxicol., 10, 820-827. 

In environmental photochemistry, research on photosensitized Initiated reactions In natural waters has focussed mainly on humic materials because they are one of the most abundant and also most strongly absorbing constituents In these waters. However, other potentially Important blogenlcally produced and photoreactlve compounds exist In seawater. One such class of compounds, which has received little attention either In terms of their concentration and distribution or their photochemical characterization In seawater. Is the flavins (FL). Flavins are of special Interest because they are among the few naturally occurring organic compounds In seawater with large cross sections at Incident... 

Soukka T, Kuningas K, Rantanen T et al (2005) Photochemical characterization of up-converting inorganic lanthanide phosphors as potential labels. J Fluoresc 15 513-528... 

Patton, D., Park, M., Wang, S., and Advincula, R.C., Evanescent waveguide and photochemical characterization of azobenzene-functionalized dendrimer ultrathin films, Langmuir, 18,1688,2002. 

Previous expositions of photochemical laws have distinguished ptominentiy between states of singlet and triplet multiplicity (1). This distinction continues to be important with respect to photophysics of smaH organic molecules, but among inorganic and organometaHic compounds, states of other multiplicities, eg, doublet and quartet states (23), play an important role. Spin conservation characterizes electronic molecular excitations and localized... 

Photochemical decomposition of riboflavin in neutral or acid solution gives lumichrome (3), 7,8-dimethyl all oxazine, which was synthesized and characterized by Karrer and his co-workers in 1934 (11). In alkaline solution, the irradiation product is lumiflavin (4), 7,8,10-trimethyhsoalloxazine its uv—vis absorption spectmm resembles that of riboflavin. It was prepared and characterized in 1933 (5). Another photodecomposition product of riboflavin is 7,8-dimethy1-10-foTmylmethy1isoa11oxazine (12). 

Either UV-VIS or IR spectroscopy can be combined with the technique of matrix isolation to detect and identify highly unstable intermediates. In this method, the intomediate is trapped in a solid inert matrix, usually one of the inert gases, at very low temperatures. Because each molecule is surrounded by inert gas atoms, there is no possiblity for intermolecular reactions and the rates of intramolecular reactions are slowed by the low temperature. Matrix isolation is a very useful method for characterizing intermediates in photochemical reactions. The method can also be used for gas-phase reactions which can be conducted in such a way that the intermediates can be rapidly condensed into the matrix. 

Pyridines and pyridazines bearing bulky perfluorinated groups behave similarly [149, ISO, ISI], although their photochemical rearrangement is not always clearly documented [752] Azaprismanes, however, have been isolated and fully characterized [75J] (equation 37)... 

Morishita, H., et al. (2002). Cloning and characterization of an active fragment of luciferase from a luminescent marine alga, Pyrocystis lunula. Photochem. Photobiol. 75 311-315. 

Viviani, V. R., et al. (1999a). Cloning and molecular characterization of the cDNA for the Brazilian larval click-beetle Pyrearinus termitilluminans luciferace. Photochem. Photobiol. 70 254-260. 

Ozin and Huber 112) synthesized and characterized very small silver particles, Ag n = 2-5) by conventional deposition methods, as well as by a novel technique that they have termed "cryophotoaggrega-tion. This study will be discussed in detail in Section III. Of interest here is a study of silver atoms and small, silver clusters entrapped in ice and high-molecular-weight paraffin (n-C22H46, n-C32Hg8) matrices 146) (see Figs. 7 and 8, and Tables IV and V). Besides the intriguing, multiple-site (solvation) occupancy of atomic silver in ice matrices, and their thermal and photochemical interconvertibility, their extremely... 

The objectives of the soil persistence experiments were (1) to learn the effect of soil type and concentration on the TCDD degradation rate, (2) to isolate and characterize degradation products from DCDD and TCDD, and (3) to determine whether chlorodioxins could be formed from chlorophenol condensation in the soil environment. This last study was essential since quality control at the manufacturing level could reduce or eliminate the formed dioxin impurity. But the biosynthesis of chlorodioxins by chlorophenol condensation in the soil environment could not be controlled and would have connotations for all chlorophenol-de-rived pesticides if formation did occur. The same question needed to be answered for photochemical condensation reactions leading to chloro-... 

The state of research on the two classes of acetylenic compounds described in this article, the cyclo[ ]carbons and tetraethynylethene derivatives, differs drastically. The synthesis of bulk quantities of a cyclocarbon remains a fascinating challenge in view of the expected instability of these compounds. These compounds would represent a fourth allotropic form of carbon, in addition to diamond, graphite, and the fullerenes. The full spectral characterization of macroscopic quantities of cyclo-C should provide a unique experimental calibration for the power of theoretical predictions dealing with the electronic and structural properties of conjugated n-chromophores of substantial size and number of heavy atoms. We believe that access to bulk cyclocarbon quantities will eventually be accomplished by controlled thermal or photochemical cycloreversion reactions of structurally defined, stable precursor molecules similar to those described in this review. 

Tacconi NR, Chenthamarakshan CR, Rajeshwar K, Tacconi El (2005) Selenium-modified titanium dioxide photochemical diode/electrolyte junctions Photocatalytic and electrochemical preparation, characterization, and model simulations. 1 Phys Chem B 109 11953-11960... 

H. (2001) Characterization of water contribution to excimer laser ablation of collagen. J. Photochem. Photobiol. A, 145, 195-200. 

By utilizing different probe wavelengths and time-scales, several different intermediates and their reactions were characterized by TR spectroscopy. These results in combination with fs-TA and fs-KTRF experiments provide important kinetics and structural information that enable an overall mechanistic characterization for the photophysical and photochemical events taking place after photolysis of pHP caged phosphates in various solvent environments. 

Our hypothesis for discussion in this section has been that the conical intersection can be characterized like any other reactive intermediate. On examining Figure 9.3 or 9.10, it is clear that a conical intersection divides the excited-state branch of the reaction path from the ground-state branch in a photochemical transformation. (We shall... 

Much attention has been devoted to the development of methods to generate quinone methides photochemically,1,19-20 since this provides temporal and spatial control over their formation (and subsequent reaction). In addition, the ability to photogenerate quinone methides enables their study using time-resolved absorption techniques (such as nanosecond laser flash photolysis (LFP)).21 This chapter covers the most important methods for the photogeneration of ortho-, meta-, and para-quinone methides. In addition, spectral and reactivity data are discussed for quinone methides that are characterized by LFP. 

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