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31.
Abstract— The photoreceptor system for the blue-light-induced phototropism in the fungus Phycomyces blakesleeanus includes one or more flavin chromophores, probably located in the plasma membrane of the sporangiophore. From a plasma-membrane fraction of short synchronous sporangiophores, we have enriched, by column chromatography, specific proteins with covalently bound flavins. These flavoproteins were analyzed by a fluorescence lifetime assay. Flavoproteins with fluorescence lifetimes significantly less than 5 ns have been predicted to be involved in blue-light reception. We studied samples from a wild type strain and from the night-blind mutant LI. (genotype madC). For the enriched flavoprotein samples, we found predominant fluorescent components with lifetimes of 1.5 ns (74%) for wild type and 1.8 ns (83%) for LI. According to this assay, one or both of these flavoproteins are likely components of the blue-light photoreceptor system in P. blakesleeanus. 相似文献
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Trevisan J Angelov PP Patel II Najand GM Cheung KT Llabjani V Pollock HM Bruce SW Pant K Carmichael PL Scott AD Martin FL 《The Analyst》2010,135(12):3266-3272
The Syrian hamster embryo (SHE) assay (pH 6.7) is an in vitro candidate to replace in vivo carcinogenicity tests. However, the conventional method of visual scoring of foci (non-transformed vs. transformed colonies) can be time-consuming and is open to subjectivity. Infrared (IR) spectroscopy has the potential to provide objective assessment of such SHE colonies with the added advantage of potentially providing mechanistic information. In this study, SHE cells were treated with one of eight different chemical regimens, allowed in culture to attach and form foci on IR-reflective glass slides; these were subsequently interrogated by attenuated total reflection (ATR) Fourier-transform IR (FTIR) spectroscopy. Derived mid-IR spectra (n = 13,406) were subjected to chemometric analysis focusing primarily on the extraction of biochemical information related to test agent treatment and/or morphological transformation. The use of ATR-FTIR spectroscopy with chemometrics to analyze the SHE assay is a novel approach to toxicological assessment. 相似文献
34.
Pollock SN Coutsias EA Wester MJ Oprea TI 《Journal of chemical information and modeling》2008,48(7):1304-1310
Mapping the chemical space of small organic molecules is approached from a theoretical graph theory viewpoint, in an effort to begin the systematic exploration of molecular topologies. We present an algorithm for exhaustive generation of scaffold topologies with up to eight rings and an efficient comparison method for graphs within this class. This method uses the return index, a topological invariant derived from the adjacency matrix of the graph. Furthermore, we describe an algorithm that verifies the adequacy of the comparison method. Applications of this method for chemical space exploration in the context of drug discovery are discussed. The key result is a unique characterization of scaffold topologies, which may lead to more efficient ways to query large chemical databases. 相似文献
35.
Stinville J.C. Francis T. Polonsky A.T. Torbet C.J. Charpagne M.A. Chen Z. Balbus G.H. Bourdin F. Valle V. Callahan P.G. Echlin M.P. Pollock T.M. 《Experimental Mechanics》2021,61(2):331-348
Experimental Mechanics - Background: Advancements in the Digitial Image Correlation (DIC) technique over the past decade have greatly improved spatial resolution. However, many processes, such as... 相似文献
36.
Gregory B. Pollock 《The Journal of mathematical sociology》2013,37(1):55-72
Simple game (sensu Brown and Vincent, 1987) evolutionary theory, when coupled with social structure measured as non‐random encounter of strategy “clones”, often permits equilibrium refinement leading to Pareto superior outcomes (e.g., Axelrod, 1981; Myerson et al., 1991), a foundational goal of economic game theory (Myerson, 1991: 370–375). This conclusion, derived from analyses of one‐shot and infinitely repeated games, fails for finitely repeated games. While mutant cluster invasion enhances Pareto efficiency of equilibria in the former, it can depress Pareto efficiency in the latter. Cooperative equilibria of finitely repeated games (under economic analysis) can be susceptible to cluster‐invasion by even more Pareto efficient strategies which are not themselves evolutionarily stable. Evolutionary (simple) game theory's ability to eliminate Pareto inferior Nash equilibrium strategies induces vulnerabilities foreign to economic analysis. Simple game analysis of finitely repeated games suggests that social structure, modeled as perennial invasion by mutant‐clusters, can induce cyclic invasion, saturation, and loss of cooperation. 相似文献
37.
M. Deutschmann G. Otter H. Böttcher H.J. Schreiber V.T. Cocconi G. Kellner D.J. Kocher D.R.O. Morrison H. Saarikko K.L. Wernhard D. Kuhn R.M. Eason B. Pollock F. Mandl M. Markytan 《Physics letters. [Part B]》1978,73(1):96-98
A total of 101 ω? decays have been found in K?p interactions at 10 and . The decay angular distribution has been fitted under the assumptions that the ω? has spin either . It has been found that the probability of isotropy (spin is less than one in a thousand, whereas the probability for spin is about 70%. Thus, we exclude the spin assignment. The lifetime of the ω? is found to be (1.41?0.24+0.15) × 10?10s, in agreement with our earlier result based on about of the present sample. 相似文献
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The low reactivity of peptide-prolyl-thioesters in native chemical ligation is not due to steric effects at the β-carbon, but rather to the presence of a carbonyl moiety on the nitrogen atom of the proline. 相似文献
40.
Pollock EN 《Talanta》1969,16(9):1323-1326
Cerium can be determined colorimetrically in minerals with sulphanilic acid. Cerium(III) ions are oxidized with silver(II) in 1-7% sulphuric acid. Sulphanilic acid is oxidized by cerium(IV) ions in 20% sulphuric acid. The absorbance is determined at 540 nm. In the presence of maganese or chromium, cerium can be separated by precipitation as the oxalate. Lanthanum can be used as a gathering agent if necessary. 相似文献