Search results for "ultraviolet"

Connection between Absorption Properties and Conformational Changes in Deinococcus radiodurans Phytochrome

2014

Phytochromes consist of several protein domains and a linear tetrapyrrole molecule, which interact as a red-light-sensing system. In this study, size-exclusion chromatography and light-scattering techniques are combined with UV-vis spectroscopy to investigate light-induced changes in dimeric Deinococcus radiodurans bacterial phytochrome (DrBphP) and its subdomains. The photosensory unit (DrCBD-PHY) shows an unusually stable Pfr state with minimal dark reversion, whereas the histidine kinase (HK) domain facilitates dark reversion to the resting state. Size-exclusion chromatography reveals that all phytochrome fragments remain as dimers in the illuminated state and dark state. Still, the elut…

Ultraviolet radiation protection by a beach umbrella.

2010

A beach umbrella intercepts all direct UV irradiance, but only part of the diffuse component. Using a simple sky view factor model, we have determined the fraction of the hemispheric diffuse irradiance that is not intercepted by the umbrella. Assuming a sensor at the surface and close to the center of the umbrella, isotropic diffuse irradiance and for an umbrella of 80 cm radius and 100 cm high, our results show that approximately 34% of the incident horizontal irradiance is not intercepted by the umbrella. These results agree with irradiance measurements conducted with and without the umbrella. The model is next extended to examine receipt of UV radiation by a human figure in a vertical po…

Molecular structures and vibrations of m-methylaniline in the S0 and S1 states studied by laser induced fluorescence spectroscopy and ab initio calcu…

2000

Abstract The UV fluorescence excitation and dispersed fluorescence spectra of a jet-cooled m-methylaniline have been obtained for the S1←S0 transition, in which some of the bands have been observed for the first time. The main spectral bands have been assigned by comparison with those of other relevant substituted benzenes. It was found that the spectra exhibit an important feature which is the internal rotation of the methyl group in the electronic ground and excited states. Ab initio calculations at MP2/6-31G* and CIS/6-31G* show that the optimized structure of m-methylaniline in the ground state is not planar with the amino group having sp3 hybridation-like character due to the existence…

EFFECTS OF SENSITIZED AND UNSENSITIZED LONGWAVE U.V.-IRRADIATION ON THE SOLUTION PROPERTIES OF DNA

1971

— Two types of photoreactions occur in DNA irradiated in aqueous systems with longwave u.v.-light (Λ > 295 nm), namely, (a) thymine dimerization, and (b) single- and double-strand breakage of the sugar phosphate backbone; these two reactions are unrelated. The presence of acetophenone as a photosensitizer caused an increase in dimerization by a factor of 16, and an increase in single-strand breaks by a factor of 4. The number of thymine dimers per single-strand break is about 100 in the sensitized and 25 in the unsensitized reaction. The alteration of the radius of gyration of DNA molecules is that expected by the degradation observed. At the same time the change in hyperchromicity is very …

New reagent for the detection of sesquiterpene lactones by thin-layer chromatography.

1984

Characterization of aquatic humic substances and their metal complexes by immobilized metal-chelate affinity chromatography on iron(III)-loaded ion e…

2001

The analytical fractionation of aquatic humic substances (HS) by means of immobilized metal-chelate affinity chromatography (IMAC) on metal-loaded chelating ion exchangers is described. The cellulose HYPHAN, loaded with different trivalent ions, and the chelate exchanger Chelex 100, loaded to 90% of its capacity with Fe(III), were used. The cellulose HYPHAN, loaded with 2% Fe(III), resulted in HS distribution coefficients Kd of up to 10(3.7) mL/g at pH 4.0 continuously decreasing down to 10(1.5) at pH 12, which were appropriate for HS fractionation by a pH-depending chromatographic procedure. Similar distribution coefficients Kd were obtained for HS sorption onto Fe(III)-loaded Chelex 100. …

Retention behaviour of paracelsin peptides on reversed-phase silicas with varying n-alkyl chain length and ligand density.

1989

As part of further investigations on the characterization of the ligand-induced conformational stabilization of peptides, two series of n-alkyldimethylsilyl bonded silicas have been prepared. In series A the n-alkyl chain length, n, of the bonded phase was varied between 1 and 20 carbon atoms at a constant ligand density. In series B the ligand density, alpha exp, was gradually changed from 0 to 4.1 mumol/m2 on a C1, C4, C6, C8 and C18 bonded phase. The retention behaviour of four peptides of the paracelsin family were examined under isocratic conditions, using a ternary mobile phase of water-methanol-acetonitrile (22:39:39, v/v/v). Plots of k' versus n showed pronounced maxima between n = …

Electropolymerization of N-methylanthranilic acid and spectroelectrochemical characterization of the formed film

2009

Abstract The electropolymerization of N-methylanthranilic acid (NMAA) is reported in this paper. The monomer is substituted both at ortho- and N-position and, to the best of our knowledge, it has not been previously electropolymerized. Electropolymerization of NMAA was done on glassy carbon and optically transparent (indium) tin oxide electrodes. The obtained films, which are probably of an oligomeric nature (oligoNMMA), were characterized with cyclic voltammetry (CV), in situ UV–vis and Raman spectroscopy, ex situ FTIR spectroscopy and scanning electron microscopy (SEM). Our results show that NMAA can be electropolymerized as thin films in 1.0 M HClO4, but the oxidation and reduction peak …

General and Theoretical Aspects of the Metal Enolates

2010

1 General Aspects 2 Structure of the Metal Enolates 3 Spectroscopy of the Metal Enolates 4 Reactivity of the Metal Enolates 5 Acknowledgments Keywords: general and theoretical aspects of metal enolates; metal enolate structure; calcium and magnesium enolates; spectroscopy of metal enolates - NMR spectroscopy; UV spectroscopy; enolate, applied to anionic structure with two carbon atoms bound through double bond; IR spectroscopy; generalized gradient approximation (GGA-DFT) for adsorption modes of acetone

ChemInform Abstract: General and Theoretical Aspects of the Metal Enolates

2010

1 General Aspects 2 Structure of the Metal Enolates 3 Spectroscopy of the Metal Enolates 4 Reactivity of the Metal Enolates 5 Acknowledgments Keywords: general and theoretical aspects of metal enolates; metal enolate structure; calcium and magnesium enolates; spectroscopy of metal enolates - NMR spectroscopy; UV spectroscopy; enolate, applied to anionic structure with two carbon atoms bound through double bond; IR spectroscopy; generalized gradient approximation (GGA-DFT) for adsorption modes of acetone