THE 'OPSIN SHIFT' IN BACTERIORHODOPSIN: STUDIES WITH ARTIFICIAL BACTERIORHODOPSINS

Abstract— The difference (in cm⁻¹) in absorption maxima between the protonated Schiff base of retinals and the pigment derived therefrom has been defined as the opsin shift. It represents the influence of the opsin binding site on the chromophore. The analysis of the opsin shifts of a series of dihydrobacteriorhodopsins has led to the external point-charge model, which in addition to a counter anion near the Schiff base ammonium, carries another negative charge in the vicinity of the β-ionone ring. This is in striking contrast to the external point-charge model proposed earlier for the bovine visual pigment. The absorption maxima of rhodopsins formed from bromo- and phenyl retinals support the two models. A retinal carrying a photoaffinity label has yielded a nonbleachable bacteriorhodopsin.     

Characterizationf of autoxidation products of retinoic acid

Retinoic acid underwent autoxidation in 90% ethanol at 25–85.5 °C to give epoxides, dioxetanes, an endoperoxide, and double-bond cleavage products. The majority of these products appear to have resulted from the initial direct oxidation of the olefinic carbons rather than from the expected allylic oxidation process.     

Irradiated rare‐earth‐doped powellite single crystal probed by confocal Raman mapping and transmission electron microscopy

The irradiation‐induced damages and structure modifications of rare earths doped powellite single crystal have been precisely studied using optical and electron microscopy techniques, including optical interferometry, confocal micro‐Raman spectroscopy and transmission electron microscopy. The surface of powellite crystal pops out anisotropically after exposing under Ar ion beam, with a saturation swelling value of 2.0% along a‐axis and 1.3% along the c‐axis of powellite at high dose. Raman mapping on focused ion‐beam sections (5 × 3 µm²) perpendicular to the irradiated surface reveals that irradiation damage induces orientation‐dependent compressive stresses in powellite. However, no significant anisotropic effect has been found on the irradiation‐induced structural disorder in powellite. At low dose (0.012 dpa), the main irradiation‐induced defects created in powellite crystal are small defect clusters. By comparison, the dominant kinds of defects in high‐dose (5.0 dpa) sample are dislocations loops and networks. Copyright © 2014 John Wiley & Sons, Ltd.     

Regioselective bond cleavage in the dissociative electron transfer to benzyl thiocyanates

The electrochemical reduction of benzyl thiocyanate and p-nitrobenzyl thiocyanate was investigated in acetonitrile at an inert electrode. These two compounds reveal a change in the reductive cleavage mechanism, and more interestingly, they show a clear-cut example of a regioselective bond dissociation. Both phenomena may be understood on the basis of the dissociative ET theory and its extension to the formation/dissociation reactions of radical ions. While the effect of the standard oxidation potential of the leaving group seems to be predominant in understanding the change in the ET mechanism by changing the driving force, the regioselective cleavage is dictated by changes in the intrinsic barrier related to the nature of the substituent on the aryl moiety.     

Game representations of classes of piecewise definable functions

We present a general way of defining various reduction games on ω which “represent” corresponding topologically defined classes of functions. In particular, we will show how to construct games for piecewise defined functions, for functions which are pointwise limit of certain sequences of functions and for Γ ‐measurable functions. These games turn out to be useful as a combinatorial tool for the study of general reducibilities for subsets of the Baire space [10] (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Beyond Borel-amenability: Scales and superamenable reducibilities

We analyze the degree-structure induced by large reducibilities under the Axiom of Determinacy. This generalizes the analysis of Borel reducibilities given in Alessandro Andretta and Donald A. Martin (2003) [1], Luca Motto Ros (2009) [6] and Luca Motto Ros. (in press) [5] e.g. to the projective levels.     

The Hurewicz dichotomy for generalized Baire spaces

By classical results of Hurewicz, Kechris and Saint-Raymond, an analytic subset of a Polish space X is covered by a K_σ subset of X if and only if it does not contain a closed-in-X subset homeomorphic to the Baire space ^ww. We consider the analogous statement (which we call the Hurewicz dichotomy) for ∑₁¹j subsets of the generalized Baire space ^κκ for a given uncountable cardinal κ with κ = κ^<κ. We show that the statement that this dichotomy holds at all uncountable regular cardinals is consistent with the axioms of ZFC together with GCH and large cardinal axioms. In contrast, we show that the dichotomy fails at all uncountable regular cardinals after we add a Cohen real to a model of GCH. We also discuss connections with some regularity properties, like the κ-perfect set property, the κ-Miller measurability, and the κ-Sacks measurability.