Illumination accelerates the decay of the O-intermediate of pharaonis phoborhodopsin (sensory rhodopsin II)

pharaonis phoborhodopsin (ppR, also called pharaonis sensory rhodopsin II [psRII]) is a member of the archaeal rhodopsin family and acts as a repellent phototaxis receptor of Natronobacterium pharaonis. Upon illumination, ppR is excited and undergoes a linear cyclic photoreaction, namely, a photocycle that constitutes photointermediates such as M- and O-intermediates (ppRM and ppRO, respectively). Under a constant background illumination (>600 nm) that irradiates ppRO, the decay rate of the flash-induced ppRO increased with an increase in the background light intensity, indicating the photoreactivity of ppRO. Azide did not influence the light-accelerated ppRO decay, but the time required for the cycle to be completed became shortened in an azide concentration-dependent manner because of acceleration of ppRM decay. Hence, the turnover rate of photocycling increased appreciably in the presence of both the background illumination and the azide. The observation reported previously (Schmies, G. et al. 2000, Biophys. J. 78:967-976) is discussed in connection with the present observations.     

Enhanced optical sensing of anions with amide-functionalized gold nanoparticles

A gold nanoparticle surface-modified with amide ligands shows enhanced optical sensing of anions: the detection limit is increased by about three orders of magnitude higher than that originally expected from the anion binding ability of neutral amide ligands.     

Siladenoserinols M–P,sulfonated serinol derivatives from a tunicate

Four new sulfonated serinol derivatives, siladenoserinols M–P (1–4), were isolated from a tunicate of the family Didemnidae collected in Indonesia. Their chemical structures were elucidated by the interpretation of NMR and mass spectroscopic data. Two of them (2 and 4) were revealed to be disulfonate serinol derivatives, and the others were monosulfonates. Siladenoserinols A (5) and B (6), which we previously isolated from the same tunicate, inhibited the p53–Hdm2 interaction with an IC₅₀ value of 2.0?μM. However, 1–4 did not inhibit the activity. The result suggested that the acetyl group in the bicyclic ketal unit and/or the glycerophospholipid moiety in 5 and 6 were responsible for the inhibition of the p53–Hdm2 interaction.     

Evaluation of the DNA Alkylation Properties of a Chlorambucil-Conjugated Cyclic Pyrrole-Imidazole Polyamide

Hairpin pyrrole-imidazole polyamides (hPIPs) and their chlorambucil (Chb) conjugates (hPIP-Chbs) can alkylate DNA in a sequence-specific manner, and have been studied as anticancer drugs. Here, we conjugated Chb to a cyclic PIP (cPIP), which is known to have a higher binding affinity than the corresponding hPIP, and investigated the DNA alkylation properties of the resulting cPIP-Chb using the optimized capillary electrophoresis method and conventional HPLC product analysis. cPIP-Chb conjugate 3 showed higher alkylation activity at its binding sites than did hPIP-Chb conjugates 1 and 2 . Subsequent HPLC analysis revealed that the alkylation site of conjugate 3 , which was identified by capillary electrophoresis, was reliable and that conjugate 3 alkylates the N3 position of adenine as do hPIP-Chbs. Moreover, conjugate 3 showed higher cytotoxicity against LNCaP prostate cancer cells than did conjugate 1 and cytotoxicity comparable to that of conjugate 2 . These results suggest that cPIP-Chbs could be novel DNA alkylating anticancer drugs.     

Luminance and Chromaticity Conditions of a Bichromatic Cross Pattern for Chromatically-Uniform Transparency

We can perceive a surface through another surface. This perception is called transparency. It is known that transparency can be perceived even if the stimulus conditions are not consistent with physical conditions for a real transparent surface. In this study, we measured the ranges of luminance and chromaticity of the overlapping area of two crossed layers at which a surface was perceived as chromatically-uniform transparent. As the results, the luminance range of the overlapping area existed around or near the luminance of the inducing area. The upper and lower limits of the luminance range were higher for the dark background than for the light background. Moreover, the chromatic range existed around the additive colormixture line between two chromaticities of the inducing areas for both dark and light backgrounds. This indicates that the perceptual transparency mechanism would divide the color of an additive color mixture into the original colors that exist in the inducing areas. We noticed that the perceptual appearance of the stimulus changed greatly depending on the luminances of the overlapping area and the background. These differences in perceptual appearance would be a factor explaining individual difference and deciding the luminance conditions for transparency.     

Cobalt-catalyzed regioselective [3+2] annulation of ortho-formyl and acetyl substituted phenylboronic acids with alkynes

Treatment of alkynes with ortho-formyl and acetyl phenylboronic acids in the presence of a cobalt catalyst resulted in the formation of 2,3-disubstituted indenols in good yields. When aryl silyl alkynes were used, 2-aryl-3-silyl indenols were obtained regioselectively in good yields.