Modulation of the absorption maximum of rhodopsin by amino acids in the C-terminus

Vision begins when light is absorbed by visual pigments. It is commonly believed that the absorption spectra of visual pigments are modulated by interactions between the retinal and amino acids within or near 4.5 angstroms of the retinal in the transmembrane (TM) segments. However, this dogma has not been rigorously tested. In this study, we show that the retinal-opsin interactions extend well beyond the retinal binding pocket. We found that, although it is positioned outside of TM segments, the C-terminus of the rhodopsin in the rockfish longspine thornyhead (Sebastolobus altivelis) modulates its lambda(max) by interacting mainly with the last TM segment. Our results illustrate how amino acids in the C-terminus are likely to interact with the retinal. We anticipate our analyses to be a starting point for viewing the spectral tuning of visual pigments as interactions between the retinal and key amino acids that are distributed throughout the entire pigment.     

New Acylated Presenegenin Saponins from Two Species of Muraltia

Six new acylated bisdesmosidic triterpene glycosides 1 – 6 were isolated from the roots of Muraltia heisteria (L.) DC., as three inseparable mixtures 1 / 2, 3 / 4 , and 5 / 6 of the (E)‐ and (Z)‐3,4,5‐trimethoxycinnamoyl derivatives. The compound pair 1 / 2 along with four known saponins were also isolated from the roots of Muraltia satureioides DC. Their structures were elucidated mainly by spectroscopic experiments including 2D‐NMR techniques as 3‐O‐(β‐D ‐glucopyranosyl)presenegenin 28‐{O‐β‐D ‐apiofuranosyl‐(1→3)‐O‐[β‐D ‐xylopyranosyl‐(1→4)]‐O‐α‐L ‐rhamnopyranosyl‐(1→2)‐O‐[6‐O‐acetyl‐β‐D ‐galactopyranosyl‐(1→3)]‐4‐O‐[(E)‐3,4,5‐trimethoxycinnamoyl]‐β‐D ‐fucopyranosyl} ester ( 1 ) and its (Z)‐isomer 2 , 3‐O‐(β‐D ‐glucopyranosyl)presenegenin 28‐{O‐6‐O‐acetyl‐β‐D ‐galactopyranosyl‐(1→3)‐O‐[3‐O‐acetyl‐α‐L ‐rhamnopyranosyl‐(1→2)]‐4‐O‐[(E)‐3,4,5‐trimethoxycinnamoyl]‐β‐D ‐fucopyranosyl} ester ( 3 ) and its (Z)‐isomer 4 , and 3‐O‐(β‐D ‐glucopyranosyl)presenegenin 28‐{O‐3‐O‐acetyl‐α‐L ‐rhamnopyranosyl‐(1→2)‐O‐[β‐D ‐xylopyranosyl‐(1→3)]‐4‐O‐[(E)‐3,4,5‐trimethoxycinnamoyl]‐β‐D ‐fucopyranosyl} ester ( 5 ) and its (Z)‐isomer 6 , respectively.     

Electrochemically regenerative visible light-induced reactivity of α-Fe2O3 films with Ag(core)–AgCl(shell) microcrystal composites

Ag(core)–AgCl(shell) microcrystal composites (Ag@AgCl) have been formed on an α-Fe₂O₃ film-coated SnO₂ electrode by a 2 step method consisting of the electrochemical reduction of Ag⁺ ions and the subsequent electrochemical oxidation. The synergy of α-Fe₂O₃ and Ag@AgCl gave rise to a high visible light-induced reactivity (λ_ex > 420 nm) for the oxidation of 2-naphthol (2-NAP) used as a model water pollutant in the presence and absence of oxygen. These findings were attributable to the function of Ag@AgCl composites as an excellent charge-separation promoter and built-in acceptor.     

Mechanismus der Charge-transfer-Polymerisation. 12. Mitt. Der Einfluß der Wellenlänge des einfallenden Lichtes auf die kationische Photopolymerisation von N-Vinylcarbazol mit Bromund Chloranil in Benzol

Ohne Zusammenfassung     

ATR mode of surface magnon polaritons on YIG

The first discussion on ATR mode of surface magnon polaritons on semi- infinite YIG is presented for the Otto configuration (polyethylene-air-YIG geometry). Damping and the effect of retardation are included in the analysis. The thickness of the air layer appropriate for ATR measurements is determined.     

Consecutive elongation of alanine oligopeptides at the second time range under hydrothermal conditions using a microflow reactor system

During the course of the study of the hydrothermal stability of alanine oligopeptides, a small amount of oligopeptides longer than the starting oligopeptides was found in the reaction products. On the basis of this unexpected finding and the investigation of the reaction mechanism, the elongation of oligopeptides using (Ala)3, (Ala)4, and (Ala)5 was attempted in aqueous solution at 275-310 degrees C within the second time range using a microflow reactor system. The elongation of (Ala)4 and (Ala)5 succeeded in the presence of an excess amount of Ala monomer. This is probably due to the fact that the elongation rate is competitive or somewhat faster than the degradation of peptide bonding. On the contrary, the elongation of (Ala)3 was not possible since it was immediately converted to diketopiperazine.