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61.
[structure: see text] A strategy for the synthesis of ajudazol A, an unusual, pharmacologically active metabolite from myxobacteria, based on the Stille cross-coupling of a 2-stannyl-oxazole with a vinyl iodide unit is described; the vinyl halide unit containing a (Z,Z)-diene was prepared in one pot by the double acetylene carbocupration of a functionalized alkyl cuprate followed by trapping with 2,3-dibromopropene. 相似文献
62.
Hachenberg J Streng C Süske E Vauth S Mayr SG Krebs HU Samwer K 《Physical review letters》2004,92(24):246102
The crossover in kinetic roughening of thin films from a particle-character-dominated regime to continuous growth behavior has been observed in this work. This has been accomplished by atomic force microscopy investigations of pulsed laser deposited amorphous organic films with thicknesses ranging from several nanometers to more than 4 microm. The early-stage random-deposition-like processes end once a closed layer is formed, which grows without saturation on the characteristic length scales. In addition, the influence of oblique film deposition has been examined and interpreted. 相似文献
63.
The hindered diffusion and binding of proteins of different sizes (lysozyme, BSA and IgG) in an agarose gel is described using adsorption kinetic and diffusional data together with an experimentally determined pore size distribution in the gel. The validity of the pore model, including variable diffusion coefficients and porosities is tested against experimental confocal microscopy data. No fitting parameters were used in the present model. The importance of knowing the gel structure is demonstrated especially for large proteins such as IgG. Experimental confocal microscopy data can be explained by the present model. 相似文献
64.
Directional synthesis of a dye-linked conducting homopolymer 总被引:2,自引:0,他引:2
We report a new synthesis of a 10,20-diphenyl-5,15-bis(4-cyanophenyl)porphyrin (1) and its reduction to give 10,20-diphenyl-5,15-bis(4-formylphenyl)porphyrin (2). When the conducting polymer poly(2',5'-dioctyl-4,4' '-terphenylenecyanovinylene) was prepared in the presence of 2, we obtained a three-domain structure, compound 3, consisting of two homopolymer blocks (J domains) with the porphyrin dye molecule (P domain) in the middle. The JPJ assembly was subjected to photophysical studies where we showed that the J domain could serve as a light-harvesting antenna for the P domain. 相似文献
65.
Adam W Krebs O Orfanopoulos M Stratakis M Vougioukalakis GC 《The Journal of organic chemistry》2003,68(6):2420-2425
The intramolecular and intermolecular kinetic isotope effects (KIE) have been determined for the nitrosoarene ene reaction with deuterium-stereolabeled 2,3-dimethyl-2-butenes (TME). trans-TME-d(6) (k(H)/k(D) = 3.0) and gem-TME-d(6) (k(H)/k(D) = 4.0) show large intramolecular primary isotope effects. In contrast, the intramolecular competition in cis-TME-d(6) (k(H)/k(D) = 1.5) and the intermolecular competition for the TME-d(0)/TME-d(12) pair (k(H)/k(D) = 1.98) show considerably smaller, but mechanistically significant kinetic isotope effects. The latter fact is rationalized in terms of reversible formation of a three-membered-ring intermediate, namely the aziridine N-oxide, or a similar unsymmetrical, polarized diradical in the first step of the reaction. Such reversibility has also been implied earlier for triazolinedione (TAD) and singlet oxygen ((1)O(2)) with deuterium-stereolabeled 2-butenes, but of the three enophiles, ArNO is the most sensitive toward reversibility, which is due to its moderate reactivity and its high steric demand. 相似文献
66.
67.
A sequence of positive integers is called a -sequence if every integer has at most representations with all in and . A -sequence is also called a -sequence or Sidon sequence. The main result is the following
Theorem. Let be a -sequence and for an integer . Then there is a -sequence of size , where .
Corollary. Let . The interval then contains a -sequence of size , when .
68.
69.
70.
L. Flatow und H. A. Krebs 《Fresenius' Journal of Analytical Chemistry》1928,75(1-2):78-80
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