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101.
Hoogesteger FJ van Walree CA Jenneskens LW Roest MR Verhoeven JW Schuddeboom W Piet JJ Warman JM 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(16):2948-2959
The photophysical properties of a bicyclohexylidene (1DA) and a bicyclohexyl (2DA) substituted with an anilino electron donor and a dicyanoethylene electron acceptor have been studied. Quenching of local donor emission is observed for these compounds as well as quenching of the "pseudo-local" acceptor emission. Transient absorption spectra show dialkylanilino-type radical-cation and dicyanoethylene-type radical-anion absorptions. These results show that intramolecular charge separation takes place in 1DA and 2DA. This was corroborated by time-resolved microwave conductivity measurements from which large excited-state dipole moments were found for both 1DA and 2DA. Time-resolved fluorescence spectroscopy revealed that in the charge-separated state in cyclohexane for 2DA, molecular folding takes place on a nanosecond timescale. For 1DA in cyclohexane, either charge separation takes place in a (fully) folded conformation or very rapid (subnanosecond timescale) folding takes place subsequent to charge separation. In addition to this difference in conformational behavior, the presence of the exocyclic double bond between the cyclohexyl-type rings results in efficient quenching of the anilino donor triplet state and acceleration of the charge recombination rate by a factor of 20. 相似文献
102.
Methods are described for achieving stepwise replacement of all BH terminal hydrogens in CoC2B4 clusters with halogen or alkyl groups, leading to complexes such as Cp*Co(2,3-Et2C2B4X4) (X=Me or I) and Cp*Co(2,3-Et2C2B4IMe2[O3SCF3]). Building on earlier work on B-functionalization of small metallacarboranes via metal-catalyzed cross-coupling, two- and three-dimensional macrocycles containing four to six metal centers have been constructed systematically from monomeric precursor complexes. 相似文献
103.
Immunological and chemical studies of cell surfaces from normal and transformed BALB/c fibroblasts have shown alterations associated with transformation. The cells studied include normal lines which do not cause tumors when injected into BALB/c mice, viral transformants, and spontaneous transformants which cause tumors that either regress or grow progressively, killing the host. The spontaneously transformed progressors include cell lines which are immunogenic and nonimmunogenic as determined by the ability of tumor excision to protect an animal from subsequent rechallenge by tumor cells. Tumor-bearing mice produce lymphocytes which are nonspecifically cytotoxic for all the normal and transformed lines. Some of the cell lines induce specific antibody formation in BALB/hosts. Antisera have been prepared in rabbits which are specific for the transformed cell lines. These antisera can be used to determine specific surface changes on the transformed cells. Chemical studies have shown glycolipid alterations between the normal cells and some, but not all, of the transformants. Glycoproteins labeled by lactoperoxidase-125I or [3H] glucosamine were compared by SDS gel electrophoresis. Results from these studies do not show changes associated with malignancy. Individual glycoprotein regions from gels were treated with pronase, and the glycopeptides compared by Sephadex G50 chromatography. Alterations in glycopeptides from several cellular glycoproteins are the only changes which appear to be associated with malignancy. 相似文献
104.
This paper presents a real-time detection of Mycobacterium tuberculosis (M. TB) using a wireless magnetoelastic sensor. The sensor is fabricated by coating a magnetoelastic ribbon (Metglas 2826MB) with a polyurethane protecting film. M. TB consumes the nutrients of a liquid culture medium in growing and reproducing process, which results in properties changes (viscosity, density, elasticity, ion concentration, etc.) of the culture medium, and consequently changes in the resonance frequency of the magnetoelastic sensor. Using the described technique M. TB is quantified and sensor response is proportional to logarithmic values of the M. TB concentration from 10(4) to 10(9)cells ml(-1), with a detection limit of 10(4)cells ml(-1) at a noise level of approximately 10 Hz. The sensor can be used effectively for monitoring the bacterial growth and good results were obtained when used in sputum sample. The drug-resistance of isoniazid (INH) and rifampin (RFP) on M. TB growth in culture medium was evaluated based on this proposed method. The wireless nature of the presented device facilitates the aseptic operations. 相似文献
105.
Hu Y Al-Mestarihi A Grimes CL Kahne D Bachmann BO 《Journal of the American Chemical Society》2008,130(47):15756-15757
Herein we describe the cloning, functional expression and initial characterization of ORF36 from Micromonospora carbonacae var. africana and rubN8 from Streptomyces achromogenes var. rubradiris. The purified enzymes play the same role, the double-oxidation of TDP-evernosamine to TDP-evernitrosose in the everninomycin and rubradirin pathways, respectively. 相似文献
106.
107.
Richard J. Wallace Diarmuid Grimes 《Journal of Algorithms in Cognition, Informatics and Logic》2008,63(1-3):114
Variable ordering heuristics that sample information before or during search in order to inform subsequent decisions have shown better performance and greater robustness than standard heuristics. One such strategy, the “weighted degree heuristic,” is based on weighting constraints according to their involvement in failure during search. A more recent approach uses “random probing” with restarting to gain information less subject to sampling bias. To date, these approaches have not been carefully analysed experimentally. In the present work, several important findings are presented, including a better delineation of the class of events that is sampled, an analysis of the importance of informed choices at the beginning of search, and a demonstration that random probing identifies sources of global contention effectively even when these are not clearly demarcated. These experiments show how empirical analysis can clarify subtle issues in the analysis of heuristic procedures for difficult search problems. 相似文献
108.
109.
Friedel–Crafts cyclization products were obtained using 1.1 equivalents of environmentally benign trichloroacetic anhydride as sole reagent and solvent. The resulting ketones included benzothiepins, benzothiopyrans, benzoxepins, dibenzothiepins, dibenzoxepins, and tetralones. 相似文献
110.
The Innate Immune Protein Nod2 Binds Directly to MDP, a Bacterial Cell Wall Fragment 总被引:1,自引:0,他引:1
CL Grimes Lde Z Ariyananda JE Melnyk EK O'Shea 《Journal of the American Chemical Society》2012,134(33):13535-13537
Mammalian Nod2 is an intracellular protein that is implicated in the innate immune response to the bacterial cell wall and is associated with the development of Crohn's disease, Blau syndrome, and gastrointestinal cancers. Nod2 is required for an immune response to muramyl dipeptide (MDP), an immunostimulatory fragment of bacterial cell wall, but it is not known whether MDP binds directly to Nod2. We report the expression and purification of human Nod2 from insect cells. Using novel MDP self-assembled monolayers (SAMs), we provide the first biochemical evidence for a direct, high-affinity interaction between Nod2 and MDP. 相似文献