Marshall Fixman

Bio: Marshall Fixman is an academic researcher from University of Oregon. The author has contributed to research in topics: Light scattering & Viscosity. The author has an hindex of 3, co-authored 3 publications receiving 351 citations.

Molten globule and protein folding.

Abstract: Publisher Summary This chapter describes the present state of the studies of the molten globule state and its role in protein folding and physiological processes Recent data on the intermediates (equilibrium and kinetic), focusing attention on the molten globule state are discussed in the chapter The molten globule has a native-like overall architecture (folding pattern) without including the rigid packing of side chains It is separated by first-order phase transitions from both the native and the unfolded states and represents a third thermodynamic state of protein molecules It is a universal kinetic intermediate in protein folding; the structure of this intermediate is similar to the structure of the equilibrium molten globule It is predicted and confirmed experimentally that the molten globule state can exist in a living cell and plays an important role in a number of physiological processes

Fractionation of DNA from mammalian cells by alkaline elution

Abstract: The method of alkaline elution provides a sensitive measure of DNA single-strand length distribution in mamalian cells and is applicable to a variety of problems concerning DNA damage, repair, and replication. The physical basis of the elution process was studied. The kinetics of elution above the alkaline transition pH were found to occur in two phases: an initial phase in which single-strand length is rate limiting, followed by a phase in which elution is accelerated due to the accumulation of alkali-induced strand breaks. The range of DNA single-strand lengths that can be discriminated by elution above the alkaline transition pH was estimated by calibration relative to the effects of x ray, and was found to be 5 X 10(8)-10(10) daltons. Shorter DNA strands elute within the pH transition zone, which extended from pH 11.3 to 11.7 when tetrapropylammonium hydroxide was used as base. This elution was relatively rapid, but was sharply limited by pH, according to the length of the strands: the length of the strands eluted increased with increasing pH. Alkaline elution was inhibited by treatment of cells with low concentrations of nitrogen mustard, a bifunctional alkylating known to cross-link DNA. On investigation of the possibility that DNA subclasses may differ in their elution behavior, satellite L strands were found to elute more slowly from cells exposed to a low dose of x ray than did the bulk DNA.

Viscosity, Sedimentation, et Cetera, of Ring- and Straight-Chain Polymers in Dilute Solution

Abstract: The hydrodynamic properties of straight‐chain and ring‐chain polymers whose dimensions are expanded over those of similar Gaussian coils have been calculated by a perturbation method based on the normal‐coordinate treatment with hydrodynamic interaction. Expansion is characterized by a parameter e, such that the mean‐square length is proportional to N1+e, N being the number of chain segments. For straight chains the intrinsic viscosity, expressed in terms of the Flory Φ (×10−23), decreases from 2.81 at e=0 to 0.686 at e=0.5, while for rings Φ varies from 1.85 to 0.422; the ratio straight:ring increases slowly from 1.5 to 2.0. The sedimentation coefficient of the straight chain increases by a factor of 2.4 over this range of e, while that of the ring goes up 2.2‐fold. The ratio straight: ring rises slowly from 0.85 to 0.91. The results on straight chains agree with those of previous workers, and the straight:ring ratio agrees with several experiments on the sedimentation of straight and ring forms of vario...