G. V. Schulz zum 70. Geburtstag mit herzlichen Wunschen gewidmet (Eingangsdatum: 14. Oktober 1975) ZUSAMMENFASSUNG:Das Verhalten polymolekularer Substanzen bei der inelastischen Lichtstreuung wird theoretisch untersucht. Fur das dabei auftretende uber einen Photomultiplier erhaltene Spektrum und die dazugehorige Autokorrelationsfunktion werden normierte Beziehungen aufgestellt. Hierin treten z-Mittel der Summen von Produkten aus den Streufunktionen mit Lorentzfunktionen bzw. mit Exponentialfunktionen auf.Beispiele von Polymeren mit Schulz-Verteilungen des Molekulargewichts werden berechnet und dabei auch der EinfluB der Relaxationszeit bestimmt. Fur die umgekehrte Aufgabe, uber die Streuexperimente die Molekulargewichtsverteilung zu erfassen, werden verschiedene analytische und numerische Losungsmoglichkeiten angegeben und die dabei moglichen, aus MeB-Ungenauigkeiten resultierenden Fehler auf das Molekulargewicht und die Breite der Verteilung diskutiert.
SUMMARY:The behaviourofpolydisperse substances in inelastic light scattering is examined theoretically. Normalized relations for the spectrum and the corresponding autocorrelation function as observed by a photomultiplier are given. The relations contain sums of products of the scattering functions with Lorentz functions or exponential functions which represent z-averages.Examples for polymers with Schulz distributions of the molecular weight are calculated and the influence of the relaxation time is determined. For the inverse problem, namely to find the molecular weight distribution from scattering experiments, different analytical and numerical solutions are given. The influence of experimental errors on the molecular weight and the width of the distribution is discussed.
Average configuration-dependent properties (mean-square radius of gyration, mean-square end-to-end distance, helical content, helix probability profile, and average number of amino acid residues in a helical segment) have been evaluated for unperturbed partially helical polypeptides by using two weighting schemes. The weighting schemes differ with regard to whether end effects in a helical segment are assigned in like manner to amino acid residues at each end or are instead associated with only one amino acid residue. Molecules considered are block copolypeptides and specific sequence copolypeptides with amino acid sequences corresponding to those found in 44 proteins. Without exception, helix formation in the proteins is found to exhibit greater cooperativity if amino acid residues at each end of a helical segment contribute to the end effects. The helix probability profile for proteins is also found to be much smoother with this weighting scheme. Block copolypeptides show more dramatic changes in helicity, helix probability profile, and average number of amino acid residues in a helical segment. Unperturbed dimensions for both proteins and block copolypeptides are nearly independent of the weighting scheme adopted. Modification of the statistical weights used for arginyl, histidyl, and lysyl residues can produce helicities and unperturbed dimensions in reasonable agreement with helicities and dimensions deduced from circular dichroism spectra and viscosity measurements of complexes formed by reduced bovine serum albumin and sodium dodecyl sulfate.
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