ABSORPTION SPECTRA OF TCA-DENATURED RHODOPSIN AND OF A SCHIFF BASE COMPOUND OF RETINAL

Abstract— When TCA-denatured rhodopsin was frozen in liquid nitrogen, Λ_max was markedly shifted to longer wavelengths as the concentration of TCA increased. After TCA denaturation, species specific absorption disappeared and the absorption maxima of the squid pigments became identical with those of corresponding pigments of octopus.
In solutions at 5° the bathochromic shift of Λ_max of TCA denatured rhodopsin was observed at higher concentrations of TCA than in the frozen state. Λ_max of N-retinylidene-butylamine (NRB) was also displaced towards longer wavelengths with increasing concentrations of TCA. This bathochromic shift was enhanced by freezing. The mode of the bathochromic shift of Λ_max provoked by TCA was very similar both in the cases of denatured rhodopsin and of NRB. The absorption spectrum of NRB was identical in shape with that of TCA-denatured rhodopsin, as the half-band widths of both materials were about 5500 cm^-1 in the liquid state and 5000 cm^-1 in the frozen state. Λ_max of retinal and NRB were red shifted in polar and polarizable solvents.
It was concluded that the strong acidity and the relatively large polarizability of TCA are responsible for the bathochromic shift of Λ_max of the Schiff base in TCA-denatured rhodopsin.     

Photocleavage reaction of bromine substituted aromatic acyl compounds studied by CIDEP and transient absorption spectroscopy

The photocleavage of the CBr bond in bromoacetylnaphthalene is investigated by transient absorption and time resolved EPR spectroscopy. In the transient absorption of 2-bromo-2′-acetylnaphthalene, the absorption band observed at λ_max ~440 nm is assigned to the triplet state of the parent molecule. After decay of the triplet absorption, a long lived absorption band is observed at λ_max ~380 nm, which is assigned to naphthoylmethyl radical. The yield of this radical is not dependent on the concentration of oxygen even though the absorption band of the triplet state was quenched by addition of oxygen. Thus we conclude that the spin multiplicity of the precursor molecule is singlet. The CW time resolved EPR spectrum shows a typical E?/A CIDEP pattern of three hyperfine lines of the naphthoylmethyl radical. This result suggests some contribution from triplet precursor molecules. However, a careful analysis of the time profile of the CIDEP intensity observed by FT-EPR revealed that the polarization is generated from the radical pair mechanism (RPM) from the encountered pair of two free naphthoylmethyl radicals and the radical-triplet pair mechanism. RPM polarization by the geminate radical pair, formed by the Br atom and the naphthoylmethyl radical, is not observed. This fact indicates that large spin-orbit coupling (Δg and/or fast spin relaxation by g anisotropy) spoils the RPM polarization. The finding is in contrast to the recent observation of RPM polarization in the Cl cleavage reaction of 1-(chloromethyl)naphthalene.     

EXTRACTION OF RETINAL FROM Paramecium bursaria

Abstract— The ciliated protozoan Paramecium bursaria is photosensitive. Retinal, which is the chromophore of the visual pigments of many multicellular animals, was extracted from P. bursaria and identified by HPLC. The procedure of identification was based on the change in polarity achieved by reducing retinal with sodium borohydrate to form retinol. This method is useful for the detection of small amounts of retinal in cells containing large amounts of other substances with similar polarity. The presence of retinal in P. bursaria suggests that this ciliate may contain a photoreceptor pigment with retinal as the chromophore.     

Top quark properties

Since the top quark was discovered at Tevatron in 1995, many top quark properties have been measured. However, the top quark is still interesting due to unique features which originate from the extremely heavy mass, and providing various test grounds on the Standard Model as well as searches for a new physics. Though the measurements of the top quark had been performed only at Tevatron so far, LHC is now ready for measurements with more top quarks than Tevatron. In this article, recent measurements of top quark properties from Tevatron (CDF and D?) as well as LHC (ATLAS and CMS) are presented.