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291.
We report room-temperature ordered multiphoton emission from multiexciton states of single CdSe(CdZnS) core(-shell) colloidal nanocrystals (NCs) that are synthesized by wet chemical methods. Spectrally and temporally resolved measurements of biexciton and triexciton emission from single NCs are also presented. A simple four level system models the results accurately and provides estimates for biexciton and triexciton radiative lifetimes and quantum yields. 相似文献
292.
Krook Margareta Lindbladh Christer Eriksen Jon Amund Mosbach Klaus 《Molecular diversity》1997,3(3):149-159
A cyclic nonapeptide library displayed on filamentous bacteriophages was selected 6 times against α-chymotrypsin (EC 3.4.21.1)
at three different pH conditions (6.5, 7.0, and 7.5). Phage peptide clones from the sixth selection, at all three pH conditions,
interacted more strongly with α-chymotrypsin than the original library and a wild-type phage did. DNA sequencing of the selected
phage peptide clones showed that different cyclic nonapeptide sequences had been selected at the different pH conditions.
The oxidized form of the synthetic peptide, Cys-Cys-Phe-Ser-Trp-Arg-Cys-Arg-Cys, selected at pH 7.5, could completely inhibit
the enzymatic activity of α-chymotrypsin. The structurally related enzymes trypsin (bovine) and elastase (porcine) were only
marginally inhibited by the same peptide under the same conditions. The inhibition constant for α-chymotrypsin was estimated
to be 10-6 M. Phage clones expressing this peptide had a lower affinity for phenylmethylsulfonylfluoride-modified α-chymotrypsin than
for natural α-chymotrypsin as determined by an enzyme immunosorbent assay. This peptide phage clone was also competitively
prevented from binding to α-chymotrypsin by the corresponding synthetic oxidized peptide. Collectively, the results suggest
that the oxidized form of the selected peptide Cys-Cys-Phe-Ser-Trp-Arg-Cys-Arg-Cys interacts with the active site of α-chymotrypsin
and acts as a specific inhibitor to the enzyme. To our knowledge, the selected sequence Cys-Cys-Phe-Ser-Trp-Arg-Cys-Arg-Cys
has not been found in nature.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
293.
294.
Irena Blute Martin Svensson Krister Holmberg Margareta Bergh Ann-Therese Karlberg 《Colloids and surfaces. A, Physicochemical and engineering aspects》1999,160(3):241-236
The solution behaviour has been investigated for an alcohol ethoxylate terminated with a formic acid ester. This compound has previously been reported to be an important degradation product in the auto-oxidation of alcohol ethoxylates. In this work we have investigated the solution behaviour of the formic acid ester surfactant C12H25(OCH2CH2)4OCHO (C12E4---OCHO). The pure formate was found to be sparsely soluble in water with no clear point at 0.1%. The critical micelle concentration was found to be 129 μM at 35°C, compared to 50 μM for the parent surfactant C12H25(OCH2CH2)5OH (C12E5). To mimic the behaviour of the oxidised surfactant, the formate was mixed in different ratios with C12E5 and the cloud point, surface tension and critical micelle concentration (cmc) of these mixtures were studied. The gradual increase of formate was found to shift the cloud point and isotropic regions to lower temperatures. The cmc of the mixture was found to be lower than for the pure surfactant. The favourable interaction was analysed according to the non-ideal model by Rubingh and the interaction parameter, β, was determined to be −4±0.53, which is unusually large for a mixture of two non-ionic surfactants. These results indicate that the reduction of cloud point observed during oxidation of non-ionic surfactants can in part be attributed to the formation of formate esters. 相似文献
295.
296.
Experimental Mechanics - Little is known about the effect of water content on the mechanical properties of dual cross-linked hydrogels. To quantify the changes in the mechanical response and... 相似文献
297.
Bernd Giese Philipp Wettstein Christian Sthelin Frdrique Barbosa Markus Neuburger Margareta Zehnder Pablo Wessig 《Angewandte Chemie (International ed. in English)》1999,38(17):2586-2587
The helical-chiral character of the diradical intermediate 2 , which cyclizes quicker than it equilibrates, explains the memory effect of chirality that occurs during the enantioselective photocyclization of alanine derivative 1 to give the proline derivative 3 . Ts=H3CC6H4SO2. 相似文献
298.
ABSTRACT The elastic constants Cik of solids are related to the amplitude of the strain fluctuations which can be simulated atomistically, thus offering a possibility of determining the Cik values of the solid of interest based on a proposed atomistic arrangement and a given interaction between the atoms. We show that the approach is practical by calculating the elastic constants of crystalline (orthorhombic) polyethylene, crystalline (monoclinic) isotactic polypropylene, and glassy bisphenol-A-polycarbonate. 相似文献