نتایج جستجو برای: internal bond
تعداد نتایج: 300930 فیلتر نتایج به سال:
A computer-readable dictionary for protein structure refinement is presented. The dictionary is based on the set of interatomic bonds and bond angles previously derived from small-molecule structures by Engh & Huber [Acta Cryst. (1991), A47, 392-400]. The internal inconsistency of the set is discussed. Some preliminary results derived from several protein structures refined at atomic resolution...
Di[dihydroxotin(IV)] Tröger's base bis-porphyrin 1, a host molecule with two internal and two external guest interaction sites, binds <or= 1 equivalent of dicarboxylic acid quantitatively within the chiral cavity, a regioselectivity amplified by initial ditopic H-bond formation, followed by kinetic trapping.
High Internal Phase Emulsion hydrogels are prepared from waterborne poly(N-isopropylacrylamide) nanogel dispersions which are non-covalently crosslinked through 2-ureido-4[1H] pyrimidinone (UPy) quadruple hydrogen bond groups. The reversible UPy crosslinks allow for the HIPE-hydrogels to be molded into objects which are thermo-responsive in nature.
The 1.8 Å resolution crystal structures of Escherichia coli aspartate aminotransferase reconstituted with 1-deazapyridoxal 5'-phosphate (deazaPLP; 2-formyl-3-hydroxy-4-methylbenzyl phosphate) in the internal aldimine and L-aspartate external aldimine forms are reported. The L-aspartate·deazaPLP external aldimine is extraordinarily stable (half-life of >20 days), allowing crystals of this interm...
Palladium-Catalyzed Oxidative Regio- and Diastereoselective Diarylating Carbocyclization of Dienynes
Transmetallation: A highly regio- and diastereoselective carbocyclization involving a palladium-catalyzed 1,2-addition of two carbon atoms across a conjugated diene has been developed (see scheme). The reaction is performed with dienynes and an oxygen tether containing a terminal or internal triple bond.
The palladium-catalyzed Sonogashira-type aerobic oxidative coupling of arylhydrazines with terminal alkynes via C-N bond cleavage has been developed; internal alkynes were afforded with a broad substrate scope. This reaction proceeds under copper- and base-free conditions with molecular oxygen as the sole oxidant and nitrogen and water as the only by-products.
Background and Aims: Retention and stability of the post and core system is the key factor for success of final restoration . The aim of this study was to evaluate the microtensile bond strength of the different composite core materials and bonding systems to a fiber post. Materials and Methods: To evaluate the bond strength of the composite resins to a fiber post ( DT light post) 60 posts ...
The rhodium(III)-catalyzed annulative coupling of 9-benzoylcarbazoles with internal alkynes proceeds efficiently through ortho C–H and C–N bond cleavages. This reaction provides direct access to variously substituted indanone derivatives. carbazolyl leaving group can be readily recovered reused for preparing the starting materials.
The functionalization of internal olefins has been a challenging task in organic synthesis. Efficient CuII-catalyzed trifluoromethylation of internal olefins, that is, α-oxoketene dithioacetals, has been achieved by using Cu(OH)2 as a catalyst and TMSCF3 as a trifluoromethylating reagent. The push-pull effect from the polarized olefin substrates facilitates the internal olefinic C-H trifluorome...
Electron motion in chemical bonds occurs on an attosecond timescale. This ultrafast motion can be driven by strong laser fields. Ultrashort asymmetric laser pulses are known to direct electrons to a certain direction. But do symmetric laser pulses destroy symmetry in breaking chemical bonds? Here we answer this question in the affirmative by employing a two-particle coincidence technique to inv...
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