A theoretical insight into the photophysics of psoralen

Psoralen photophysics has been studied on quantum chemistry grounds using the multiconfigurational second-order perturbation method CASPT2. Absorption and emission spectra of the system have been rationalized by computing the energies and properties of the low-lying singlet and triplet excited states. The S1 ππ* state has been determined to be responsible of the lowest absorption and fluorescence bands and to initially carry the population in the photophysical processes related to the phototherapeutic properties of psoralen derivatives. The low-lying T1 ππ* state is, on the other hand, protagonist of the phosphorescence, and its prevalent role in the reactivity of psoralen is suggested to be related to the elongation of the pyrone ring C3–C4 bond, where the spin density is distributed on both carbon atoms. Analysis of energy gaps and spin-orbit coupling elements indicates that the efficient photophysical process leading to the population of the lowest triplet state does not take place at the Franck-Condon region but along the S1 relaxation [email protected] [email protected] [email protected]

Excited singlet molecular O-2 ((1)Delta g) is generated enzymatically from excited carbonyls in the dark

In mammalian tissues, ultraweak chemiluminescence arising from biomolecule oxidation has been attributed to the radiative deactivation of singlet molecular oxygen [O-2 ((1)Delta(g))] and electronically excited triplet carbonyl products involving dioxetane intermediates. Herein, we describe evidence of the generation of O-2 ((1)Delta(g)) in aqueous solution via energy transfer from excited triplet acetone. This involves thermolysis of 3,3,4,4-tetramethyl-1,2-dioxetane, a chemical source, and horseradish peroxidase-catalyzed oxidation of 2-methylpropanal, as an enzymatic source. Both sources of excited carbonyls showed characteristic light emission at 1,270 nm, directly indicative of the monomolecular decay of O-2 ((1)Delta(g)). Indirect analysis of O2 (1Dg) by electron paramagnetic resonance using the chemical trap 2,2,6,6-tetramethylpiperidine showed the formation of 2,2,6,6-tetramethylpiperidine-1-oxyl. Using [O-18]-labeled triplet, ground state molecular oxygen [O-18(2) ((3)Sigma(g) -)], chemical trapping of O-18(2) ((1)Delta(g)) with disodium salt of anthracene-9,10-diyldiethane-2,1-diyl disulfate yielding the corresponding double-[O-18]-labeled 9,10-endoperoxide, was detected through mass spectrometry. This corroborates formation of O-2 ((1)Delta(g)). Altogether, photoemission and chemical trapping studies clearly demonstrate that chemically and enzymatically nascent excited carbonyl generates O-18(2) ((1)Delta(g)) by triplet-triplet energy transfer to ground state oxygen O-2 ((1)Delta(g)), and supports the long formulated hypothesis of O-2 ((1)Delta(g)) involvement in physiological and pathophysiological events that might take place in tissues in the absence of light.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)PRONEX/FINEP (Programa de Apoio aos Nucleos de Excelencia)PRPUSP (Pro-Reitoria de Pesquisa da Universidade de São Paulo)Instituto do Milenio-RedoxomaNAP Redoxoma (PRPUSP)Fundo Bunka de Pesquisa Banco Sumitomo Mitsui )L'OREALJohn Simon Guggenheim Memorial FoundationNational Foundation for Cancer Research, Bethesda, MD, USAUniv São Paulo, Inst Quim, Dept Bioquim, BR-05513970 São Paulo, BrazilUniv Fed Parana, Dept Bioquim & Biol Mol, Set Ciencias Biol, BR-80060000 Curitiba, Parana, BrazilCEA Grenoble, Inst Nanosci & Cryogenie, F-38054 Grenoble 9, FranceUniv Dusseldorf, Inst Biochem & Mol Biol 1, Dusseldorf, GermanyUniv Dusseldorf, Leibniz Res Inst Environm Med, Dusseldorf, GermanyUniversidade Federal de São Paulo, Inst Ciencias Ambientais Quim & Farmaceut, Dept Ciencias Exatas & Terra, São Paulo, BrazilUniversidade Federal de São Paulo, Inst Ciencias Ambientais Quim & Farmaceut, Dept Ciencias Exatas & Terra, São Paulo, BrazilFAPESP: 2006/56530-4FAPESP: 2012/12663-1Instituto do Milenio-Redoxoma: 420011/2005-6FAPESP: 573530/2008-4NAP Redoxoma (PRPUSP): 2011.1.9352.1.8FAPESP: 2013/07937-8Web of Scienc

Derivation of consistent hard rock (1000<Vs<3000 m/s) GMPEs from surface and down-hole recordings: Analysis of KiK-net data

A key component in seismic hazard assessment is the estimation of ground motion for hard rock sites, either for applications to installations built on this site category, or as an input motion for site response computation. Empirical ground motion prediction equations (GMPEs) are the traditional basis for estimating ground motion while VS30 is the basis to account for site conditions. As current GMPEs are poorly constrained for VS30 larger than 1000 m/s, the presently used approach for estimating hazard on hard rock sites consists of “host-to-target” adjustment techniques based on VS30 and κ0 values. The present study investigates alternative methods on the basis of a KiK-net dataset corresponding to stiff and rocky sites with 500 < VS30 < 1350 m/s. The existence of sensor pairs (one at the surface and one in depth) and the availability of P- and S-wave velocity profiles allow deriving two “virtual” datasets associated to outcropping hard rock sites with VS in the range [1000, 3000] m/s with two independent corrections: 1/down-hole recordings modified from within motion to outcropping motion with a depth correction factor, 2/surface recordings deconvolved from their specific site response derived through 1D simulation. GMPEs with simple functional forms are then developed, including a VS30 site term. They lead to consistent and robust hard-rock motion estimates, which prove to be significantly lower than host-to-target adjustment predictions. The difference can reach a factor up to 3–4 beyond 5 Hz for very hard-rock, but decreases for decreasing frequency until vanishing below 2 Hz

Cloning, Expression and Purification of an Acetoacetyl CoA Thiolase from Sunflower Cotyledon

Thiolase I and II coexist as part of the glyoxysomal β-oxidation system in sunflower (Helianthus annuus L.) cotyledons, the only system shown to have both forms. The importance of thiolases can be underscored not only by their ubiquity, but also by their involvement in a wide variety of processes in plants, animals and bacteria. Here we describe the cloning, expression and purification of acetoacetyl CoA thiolase (AACT) in enzymatically active form. Use of the extensive amount of sequence information from the databases facilitated the efficient generation of the gene-specific primers used in the RACE protocols. The recombinant AACT (1233 bp) shares 75% similarity with other plant AACTs. Comparison of specific activity of this recombinant AACT to a previously reported enzyme purified from primary sunflower cotyledon tissue was very similar (263 nkat/mg protein vs 220 nkat/mg protein, respectively). Combining the most pure fractions from the affinity column, the enzyme was purified 88-fold with a 55% yield of the enzymatically active, 47 kDa AACT