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11.
In order to assign the structural changes of the protein, observed in the Fourier transform infrared (FT-IR) difference spectra of the rhodopsin-metarhodopsin-II transition, to specific regions of the protein, rhodopsin was treated by proteases. Nonilluminated and bleached rhodopsin was treated with protease K and papain. Rhodopsin digested in the bleached state was subsequently regenerated with 11-cis-retinal. From these modified samples the rhodopsin-metarhodopsin-II FT-IR difference spectra were measured. Comparing the difference spectra with that of unmodified rhodopsin, clear deviations in the amide-I and amide-II spectral range are observed. This indicates that in the unmodified pigment conformational changes of those parts of the cytosolic surface take place which are susceptible to the proteases. From the larger spectral changes obtained with samples digested in the bleached state it is concluded that the extent of modification is larger. The difference spectra of rhodopsin modified with 10 mM dithiothreitol support the existence of the 4th loop which also undergoes conformational changes. The spectral changes are interpreted in terms of a transition of an ordered structure of the loops in rhodopsin to a more random structure in metarhodopsin-II. The results demonstrate that by combining FT-IR spectroscopy with protein modification by specific proteases, conformational changes of the protein can be localized to specific regions. 相似文献
12.
Ellis D Lopez ME McIntosh R Rosair GM Welch AJ Quenardelle R 《Chemical communications (Cambridge, England)》2005,(10):1348-1350
Reduction of 1,12-closo-C2B10H12 or its C,C-dimethyl analogue with sodium in liquid ammonia followed by metallation with {CpCo}2+, {(arene)Ru}2+ or {(dppe)Ni}2+ fragments affords the first examples of 4,1,10-MC2B10 species; thermolysis of these yields the appropriate 4,1,12-MC2B10 isomers, unavailable for (arene)Ru metallacarboranes by similar thermolysis of known 4,1,6-MC2B10 compounds. 相似文献
13.
1,2endo-Trimethylenenorbornane (1) in the presence of aluminium bromide in carbon disulfide at ?60° isomerizes at a much higher rate than its 2exo-isomer 2 to 2endo, 6endo-trimethylenenorbornane (3) as the sole product. By consequence, the hydrocarbon 2 being the next intermediate in the sequence of the adamantane rearrangement of 1 seems to be very unlikely. 相似文献
14.
2-Aza-7-thia-twistanes (or 2-thia-7-aza-twistanes, respectively) The suitably substituted 9-thiabicylo[3.3.1]nonanes 7–9 and 17 were synthesized and subsequently cyclized to the 2-aza-7-thia-twistanes 21–23 and 19 , respectivelly, from which several other twistane derivatives ( 20 and 24–29 ) were prepared. 相似文献
15.
In the AlBr3-catalyzed adamantane rearrangement in CS2 of 1,2-exo-trimethylenenorbornane ( 1 ) to 2-endo,6-endo-trimethylenenorbornane ( 3 ), hydride-ion abstraction occurs at C(6) from the exo-side. The kH/kD value for competition between 1 and 5 (Dexo-C(6)) was 1.58 ± 0.05, whereas no kinetic isotope effect was operative for competition between unlabeled 1 and 4 (Dendo-C(5)) and between 1 and 6 (Dendo-C(6)). 相似文献
16.
Teh-Chang Chou Holger Lange Rolf Gleiter Tibor Ggh Miroslav Krí Max H. Pfenninger Marian Valentíny Camille Ganter 《Helvetica chimica acta》1995,78(8):2011-2025
Three 1,4-dimethylidenecyclohexanes, bridged in the 2,6- and 3,5-positions by two ethano ( 4 ), one ethano and one propano ( 5 ), and two propano bridges ( 6 ) have been synthesized. The interaction of the two exocyclic methylidene groups has been investigated by He(I) photoelectron (PE) spectroscopy. It revealed a slightly larger energy difference (0.8 eV) for 4 and 5 as compared to the parent 1,4-dimethylidenecyclohexane ( 7 ) (0.7 eV). The interpretation of the PE spectra was based on the comparison with PE data of related systems and with the results of semiempirical calculations on 4–6 . 相似文献
17.
18.
U M Ganter E D Schmid F Siebert 《Journal of photochemistry and photobiology. B, Biology》1988,2(4):417-426
The photoreaction of vacuum-dried rhodopsin was monitored by UV-visible absorption spectroscopy. The results indicate that in dry rhodopsin, isorhodopsin and lumirhodopsin a protonation equilibrium exists between the protonated and the non-protonated Schiff base. On hydration the water stabilizes the protonated forms. In metarhodopsin-I the protein itself is able to stabilize the protonated Schiff base. The direct involvement of water in the retinal binding site was demonstrated by measuring the rhodopsin-bathorhodopsin FTIR difference spectra of rhodopsin hydrated with H2O and H2(18)O. The results are discussed with respect to the problem of charge stabilization and energy storage. 相似文献
19.
Oxymercuration of cis, cis-1, 5-cyclooctadiene ( 1 ), followed by treatment with potassium iodide and subsequent reaction with iodine, leads to six isomeric diiodides which represent the three possible stereoisomers 2 , 3 , and 4 of 2, 5-diiodo-9-oxabicyclo[4.2.1]nonane as well as 5 , 6 , and 7 of 2, 6-diiodo-9-oxabicyclo[3.3.1]nonane. The isolation, structure determination and some reactions of these diiodo compounds 2 – 7 are described. 相似文献
20.
Pierre Raboisson Dominique SchultzClaire Lugnier Romain MathieuJean-Jacques Bourguignon 《Tetrahedron letters》2003,44(4):703-705
An expedient synthesis of 8-acylamidopyrazolo[1,5-a]-1,3,5-triazines was developed by treating 8-amino-4-[N-(4-aminophenyl)-N-(methyl)amino]pyrazolo[1,5-a]-1,3,5-triazine with various acyl chlorides following by the displacement of the so-formed N-(methyl)-N-[4-(acylamido)phenyl]amino leaving group with various amines. Applications to high-throughput synthesis are suggested. 相似文献