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Toxin gamma is a basic, low-molecular-weight, neurotoxic protein, isolated from the venom of the Brazilian scorpion, Tityus serrulatus. Raman spectra (400-1800 cm-1 region) of this toxin in both the lyophilized state and in 0.1 M acetate buffer (pH 4.5) and the infrared spectrum (700-4000 cm-1 region) of a solid film were investigated. From the vibrational(More)
We report on the size, shape, structure, and interactions of lysozyme in the ternary system lysozyme/DMSO/water at low protein concentrations. Three structural regimes have been identified, which we term the "folded" (0 < φ(DMSO) < 0.7), "unfolded" (0.7 ≤ φ(DMSO) < 0.9), and "partially collapsed" (0.9 ≤ φ(DMSO) < 1.0) regime. Lysozyme resides in a folded(More)
A low-resolution 1H NMR relaxometry study on the dynamics of an n-decane/water emulsion stabilized by beta-casein is presented. Spin-spin (transverse) relaxation time constants (T2) were used to assess relative mobilities of emulsion components, by a selective deuteration procedure. Data analysis allowed the emulsion investigated to be described by a(More)
Semi-solid viscoelastic matrices produced out of lysozyme in organic/aqueous media [tetramethylurea (TMU)/water] were characterized by small angle X-ray scattering (SAXS). The scattering curves were modeled in their form and interference factors. Radii of gyration of scattering particles were found to undergo a dramatic increase from 14 A in water to(More)
OBJECTIVES Studies of the viscoelastic properties of the vocal folds are normally performed with rheometers that use parallel plates whose interplate space is usually arbitrarily assigned a fixed value. In tissues subject to variation of thickness between samples, fixed gaps could result in different compressions, compromising the comparison among them. We(More)
Biopolymers and their derivatives are being actively investigated as substitutes for petroleum-based polymers. This has generated an intense interest in investigating new solvents, in particular for cellulose, chitin/chitosan, and starch. This overview focuses on recent advances in the dissolution and derivatization of these polysaccharides in solutions of(More)
The gelation process of lysozyme in water/tetramethylurea in the presence of salt was investigated as a function of temperature and system composition by rheology, infrared spectroscopy, and microcalorimetry. Times and temperatures of gelation were determined from the variation of the storage (G') and loss (G'') moduli. It was found that gelation times(More)
Rheological properties of lysozyme viscoelastic matrices resulting from a sol-gel transition taking place in organic/aqueous media at room temperature were investigated. Gel-like structures, of transparent appearance, developed out of lysozyme (5.0 mmol/dm(3)) dispersed in tetramethylurea (TMU)/water binary mixtures, at TMU mass fraction (w) ranging from(More)
A model of a rheologically relevant protein, omega-gliadin, is proposed and studied in this work by means of molecular dynamics techniques. The model is based on an octapeptide repeat motif that is experimentally described as characteristic of that protein and as constituting it almost entirely. The initial molecular structure consisted of 20 such repeats.(More)
We used a recently developed software that mimics a cytoplasm/membrane environment, with an interface separating two continuous media of different dielectric constants (1). This software has been designed to allow modelling of different kinds of molecules of biological interest such as proteins and drugs, in each of the isolated continuous media, as well as(More)