The internal dynamic modes of charged self-assembled peptide fibrils

Photon correlation spectroscopy is used to study the internal dynamics of self-assembled charged peptide fibrils. Short neutral and charged polymeric aggregates have diffusive modes due to whole macromolecular motion. For long semiflexible fibrils the logarithm of the intermediate scattering function follows a q(2)t(3/4) scaling at long times consistent with a Kratky-Porod free energy and preaveraged Oseen hydrodynamics. Persistence lengths on the order of micrometers are calculated for the peptide fibrils consistent with estimates from the liquid-crystalline phase behavior. Fibril diameters (5-35 nm) calculated from the initial decay of the correlation functions are in agreement with transmission electron microscopy measurements.     

Azimuthal anisotropy of photon and charged parti cle emissionin 208Pb + 208Pb collisions at 158 $\ cdot A$ GeV/ c

The azimuthal distributions of photons and charged particles with respect to the event plane are investigated as a function of centrality in ²⁰⁸Pb + ²⁰⁸Pb collisions at 158 GeV/c in the WA98 experiment at the CERN SPS. The anisotropy of the azimuthal distributions is characterized using a Fourier analysis. For both the photon and charged particle distributions the first two Fourier coefficients are observed to decrease with increasing centrality. The observed anisotropies of the photon distributions compare well with the expectations from the charged particle measurements for all centralities.Received: 22 May 2004, Revised: 14 April 2005, Published online: 4 May 2005PACS: 25.75.Dw     

Analysis of chemical warfare agents III. Use of bis-nucleophiles in the trace level determination of phosgene and perfluoroisobutylene

The reactivity of phosgene and perfluoroisobutylene (PFIB) towards 1,2-bis-nucleophiles was exploited to allow determination of these gases in air samples. 2-Aminothiophenol (ATP), 3,4-dimercaptotoluene (DMT) and 2-hydroxymethylpiperidine (HMP) were evaluated as bis-nucleophiles capable of forming thermally-stable derivatives with phosgene and PFIB when loaded with triethylamine onto Tenax TA. Experimental design was used to optimise thermal desorption conditions. Detection limits in the low ngm(-3) range were observed for the five derivatives investigated. This work represents the most sensitive analytical method for trace level quantitation of phosgene and PFIB published to date.     

Dilepton and trilepton production by antineutrinos and neutrinos in neon

A sample of over 25,000 fully measured neutrino and antineutrino charged current interactions in BEBC includes 192 dilepton candidates. The prompt signal after subtraction of background is 41 ±7µ⁺ e ^-, 35±7µ⁺µ^- events from \(\bar v\) interactions, and 32±7µ^-µ⁺ events from ν interactions. There are 2 trileptons, µ^-µ^- e ⁺ and µ^-µ^-µ⁺. Results are compared with other experimental data and with the standard model. Limits to prompt like sign µ⁺ e ⁺, µ⁺µ⁺ and µ^-µ^- signals are given and compared with other experiments and with theoretical calculations.     

Efficient Preparation of Pyridinyl‐1,2,4‐Triazines via Telescoped Condensation with Diversely Functionalized 1,2‐Dicarbonyls

The development of materials for efficient chemoselective extraction of minor actinides remains at the forefront of research efforts in the area of separation science. Lewis basic complexants derived from nitrogen‐donor scaffolds are often employed in this area due to favorable complexation with the transuranic element americium. In the present work an efficient procedure for the preparation of eight useful 3‐pyridin‐2‐yl‐1,2,4‐triazines (2 novel) is demonstrated via telescoped condensation with the requisite 1,2‐dicarbonyl in two‐pots without additives, differentially extractive work‐up procedures, or recrystallization. Additional efforts in this area have demonstrated the utility of polar aprotic solvents for the preparation of nine functionalized pyridinyl‐2,6‐bis‐1,2,4‐triazines (4 novel) directly from the requisite 2,6‐pyridine dicarbonitrile in 49–99% yield over four total steps. The streamlined preparation of these important materials and detailed synthetic procedures is reported herein.     

A laser extraction/combustion technique for in situ delta(13)C analysis of organic and inorganic materials

A CO(2) laser extraction system is described for in situ delta(13)C analysis of organic and inorganic materials. Carbonaceous compounds volatilized by the laser are quantitatively converted to CO(2) gas by a combustion furnace mounted after the sample chamber. Gases produced by the laser and combustion processes are swept by helium carrier gas and separated by a packed gas chromatography column prior to their introduction to an isotope ratio monitoring mass spectrometer. A sample of lentil bean was analyzed at a spatial resolution of 200 μm and yielded delta(13)C values with precision of +/- 0.3 per thousand. The accuracy of delta(13)C measurements was better than +/- 0.5 per thousand from NBS 22 (mineral oil), USGS 24 (graphite), and IAEA CO-1 (calcium carbonate). Copyright 1999 John Wiley & Sons, Ltd.     

Structural and redox properties of mitochondrial cytochrome c co-sorbed with phosphate on hematite (alpha-Fe2O3) surfaces

The interaction of metalloproteins with oxides has implications not only for bioanalytical systems and biosensors but also in the areas of biomimetic photovoltaic devices, bioremediation, and bacterial metal reduction. Here, we investigate mitochondrial ferricytochrome c (Cyt c) co-sorption with 0.01 and 0.1 M phosphate on hematite (alpha-Fe2O3) surfaces as a function of pH (2-11). Although Cyt c sorption to hematite in the presence of phosphate is consistent with electrostatic attraction, other forces act upon Cyt c as well. The occurrence of multilayer adsorption, and our AFM observations, suggest that Cyt c aggregates as the pH approaches the Cyt c isoelectric point. In solution, methionine coordination of heme Fe occurs only between pH 3 and 7, but in the presence of phosphate this coordination is retained up to pH 10. Electrochemical evidence for the presence of native Cyt c occurs down to pH 3 and up to pH 10 in the absence of phosphate, and this range is extended to pH 2 and 11 in the presence of phosphate. Cyt c that initially adsorbs to a hematite surface may undergo conformation change and coat the surface with unfolded protein such that subsequently adsorbing protein is more likely to retain the native conformational state. AFM provides evidence for rapid sorption kinetics for Cyt c co-sorbed with 0.01 or 0.1 M phosphate. Cyt c co-sorbed with 0.01 M phosphate appears to unfold on the surface of hematite while Cyt c co-sorbed with 0.1 M phosphate possibly retains native conformation due to aggregation.     

Coherent production ofρ − mesons in charged current antineutrino-neon interactions in BEBC

Coherent production ofρ ^? mesons in charged current antineutrino interactions on neon nuclei is studied in the BEBC bubble chamber exposed to the CERN SPS wide band beam. The cross section is measured to be (95±25)·10^?40 cm² per neon nucleus, averaged over the beam energy spectrum. The distributions of kinematical variables and the absolute value of the cross section are in agreement with theoretical predictions based on the CVC hypothesis and the vector meson dominance model.