Orientation of peptides in aqueous monolayer films. Infrared reflection-absorption spectroscopy studies of a synthetic amphipathic beta-sheet

Infrared reflection-absorption spectroscopy (IRRAS) intensities of the Amide I vibration are used to develop a quantitative approach for determining the Euler angles that describe the orientation of protein beta-sheets in aqueous monolayer films. A synthetic amphipathic peptide, Val-Glu-Val-Orn-Val-Glu-Val-Orn-Val-Glu-Val-Orn-Val-OH is used as a test case. The pattern of Amide I frequencies suggests that the molecule is organized as an antiparallel beta-sheet at the air/water interface. The model used to simulate the Amide I intensities reveals that the beta-sheet has a slight preferential alignment parallel to the direction of compression; i.e., deviation from uniaxial symmetry is observed. In addition, the sheet is found to lie flat on the aqueous surface, with (presumably) the polar side chains interacting with the aqueous subphase. Limitations and advantages of the theoretical approach are discussed.     

Eine geometrische Kennzeichnung linearer Abbildungen

Ohne ZusammenfassungHerrn Prof. Dr. J. Krames zum 75. Geburtstag gewidmet     

Kreisgeometrie in der isotropen Ebene

Ohne ZusammenfassungHerrn K. Strubecker zum 60. Geburtstag gewidmet     

Buchbesprechungen

Ohne Zusammenfassung     

Die Flächen mit Böschungslinien als Fallinien

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Goldstone boson counting in relativistic systems at finite density

We study the effects of finite chemical potential on the pattern of symmetry breaking within the relativistic linear sigma model. In accordance with previous works we show that type-II Goldstone bosons may appear whose dispersion relation is quadratic in momentum in the long-wavelength limit. We show that their presence is tightly connected with nonzero densities of non-Abelian Noether charges, and formulate a general counting rule for the number of the Goldstone bosons. Working at tree level, we conclude with the discussion of the loop effects. Our results find an application in particular to cold dense quark matter, where a type-II Goldstone boson has been found, e.g., in the phases with kaon condensation.     

Einsatz der Abriebmethode für die Verwechslungsprüfung hochlegierter Stähle

The method of abrasion of small sample quantities on Al₂O₃-disks is applicable to alloy and high-alloy steels. For example the contents of the elements Si, Cr, Ni, Mn, V, W, Mo, Ti and Nb may be determined quantitatively. The possible sorting of high-alloy steels and scarp is an important thing of economy. The method of abrasion with a X-ray spectrometric detection system is simple and of low costs.     

Studies in chemical ionization mass spectrometry: V—localization of homoconjugated triene and tetraene units in aliphatic compounds

The homoconjugated triene (‘linolenic acid unsaturation’) and tetraene (‘arachidonic acid unsaturation’) pattern can be readily recognized and localized in aliphatic compounds by chemical ionization (NO) mass spectrometry. This method may be used for the screening of biological material, especially in food analysis.     

FTIR studies of collagen model peptides: complementary experimental and simulation approaches to conformation and unfolding

X-ray crystallography of collagen model peptides has provided high-resolution structures of the basic triple-helical conformation and its water-mediated hydration network. Vibrational spectroscopy provides a useful bridge for transferring the structural information from X-ray diffraction to collagen in its native environment. The vibrational mode most useful for this purpose is the amide I mode (mostly peptide bond C=O stretch) near 1650 cm-1. The current study refines and extends the range of utility of a novel simulation method that accurately predicts the infrared (IR) amide I spectral contour from the three-dimensional structure of a protein or peptide. The approach is demonstrated through accurate simulation of the experimental amide I contour in solution for both a standard triple helix, (Pro-Pro-Gly)10, and a second peptide with a Gly --> Ala substitution in the middle of the chain that models the effect of a mutation in the native collagen sequence. Monitoring the major amide I peak as a function of temperature gives sharp thermal transitions for both peptides, similar to those obtained by circular dichroism spectroscopy, and the Fourier transform infrared (FTIR) spectra of the unfolded states were compared with polyproline II. The simulation studies were extended to model early stages of thermal denaturation of (Pro-Pro-Gly)10. Dihedral angle changes suggested by molecular dynamics simulations were made in a stepwise fashion to generate peptide unwinding from each end, which emulates the effect of increasing temperature. Simulated bands from these new structures were then compared to the experimental bands obtained as temperature was increased. The similarity between the simulated and experimental IR spectra lends credence to the simulation method and paves the way for a variety of applications.     

Die konstant gedrallten windschiefen Flächen 4. Grades mit reduzibler Fernkurve

Ohne ZusammenfassungHerrnFriedrich Lösch zum 60. Geburtstag am 10. Dezember 1963 gewidmet