FOURIER ANALYSIS OF ANGULAR DISTRIBUTIONS FOR MOTILE MICROORGANISMS

The method of Fourier transformation is used to analyze histograms of the angular distribution of organisms moving with respect to a stimulus, in this case the light direction. In the Fourier spectra, the components with the highest amplitudes indicate the modality of orientation, i.e. the number of preferred directions, and the corresponding phase values indicate the deviation from the light direction. In the frequency domain, those components with high amplitude and/or those with low frequencies (low-pass filtering) can be selected and used to reconstruct a smoothed histogram by means of an inverse Fourier transform. This method reduces the noise level and reveals the prominent features of histograms. Examples of unimodal, bimodal and multimodal distributions are shown in their original and smoothed form for the flagellate Euglena gracilis , and for amoebae and pseudoplasmodia or the slime mold Dictyostelium discoideum.     

Synthesis and Chemical Transformations of 5-Alkyl(phenyl)-4,5,6,7-tetrahydro[1,2,4]triazolo[1,5-<Emphasis Type="Italic">a</Emphasis>]pyrimidin-7-oles

5,5,7-Trimethyl-4,5,6,7-tetrahydro[1,2,4]triazolo[1,5-a]pyrimidin-7-ol was synthesized by cyclocondensation of 3-amino-1,2,4-triazole with 4-methylpent-3-en-2-one; its chemical transformations, and also the transformations of 5-phenyl-4,5,6,7-tetrahydro[1,2,4]triazolo[1,5-a]pyrimidin-7-ol were investigated in reactions with reagents of diverse electronic nature.     

3-Hydroxypyrimido[1,2-a]benzimidazoles

The oxidation of aromatic derivatives of 1,4- and 3,4-dihydropyrimido[1,2a]benzimidazoles gave the corresponding 3-hydroxy-3,4-dihydro derivatives and the dehydrogenation of these compounds was carried out. An x-ray diffraction structural analysis was carried out on 2-(4-dimethylaminophenyl)-3-hydroxy-4-phenyl-3,4-dihydropyrimido[1,2a]benzimidazole.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 688–693, May, 1993.     

A FLAVOPROTEIN IN Phycomyces blakesleeanus WITH SHORT FLUORESCENCE LIFETIME

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.     

Chemical conversions of 5,7-disubstituted dihydro-1,2,4-triazolo[1,5-a]pyrimidines

Hydrolysis, oxidation, reduction, alkylation, and nitrosation of aromatic-substituted dihydro-1,2,4-triazolo-[1,5-a]pyrimidines have been studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1638–1642, December, 1990.     

Mechanism for the formation of gas-phase protonated alcohol-ether adducts by VUV laser ionization and density-functional calculations

The neutral vapors above liquid alcohol/ether mixtures, (diethyl ether/methanol, diethyl ether/ethanol, tetrahydrofuran/methanol, and tetrahydrofuran/ethanol) were co-expanded with He in a supersonic jet, ionized with a 118-nm vacuum ultraviolet laser, and detected in a time-of-flight mass spectrometer. In each case, features attributed to protonated alcohol-ether dimers and protonated ether monomers were observed, as well as those ions obtained by ionizing neat alcohol or ether samples alone. Theoretical calculations, carried out to establish the energetics of the various possible reactions leading to the formation of the observed binary adducts, indicate that the most thermodynamically favorable pathway corresponds to the addition of a protonated alcohol monomer to neutral ether.     

Cyclocondensation of 3-Amino-1,2,4-triazoles with Esters of Substituted Cinnamic Acids and Aromatic Unsaturated Ketones

We have studied the reactions of 3-amino, 3,5-diamino-, and 3-amino-5-trifluoromethyl-1,2,4-triazole with esters of substituted cinnamic acids and aromatic unsaturated ketones; we have established the directionality of formation of the tetrahydrooxopyrimidine ring. We have carried out hydrolysis and hydrazinolysis of 7-phenyl-4,5,6,7-tetrahydro-1,2,4-triazolo[1,5-a]pyrimidin-5-one. We have conducted an X-ray diffraction study of isopropylidene hydrazide of 3-(5-amino-1,2,4-triazol-1-yl)-3-phenylpropionic acid.     

Simulation studies of branched polymer molecules

Monte Carlo simulation results are presented for lattice models of uniform stars (one branch point of functionality f = 3), combs (two branch points, ? = 3,3) and brushes (two branch points ? = 3,4 and ? = 3,5). We estimate the critical exponent γ(?), the ratio g(?) = 〈S(?)〉/〈S(1)〉 (where 〈S(?)〉 is the mean-square radius of gyration of a structure having ? branches and N monomers), and the meansquare end-to-end branch lengths, as a function of the number and arrangement of branches. Comparisons with theoretical predictions and experimental data are made where possible, leading to a test of some predictions, and a suggestion concerning future experiments.