muramidase and 1-4-dioxane

Well-controlled poly(N-vinylpyrrolidone) (PVP)-grafted silicon surfaces were prepared by surface-initiated atom transfer radical polymerization (SI-ATRP) with 1,4-dioxane/water mixtures as solvents and CuCl/5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane (Me6TATD) as a catalyst. The thickness of the PVP layer on the surface increased with reaction time, suggesting that the ATRP grafting of N-vinylpyrrolidone (NVP) from the silicon surfaces was a well-controlled process. The water contact angle and X-ray photoelectron spectroscopy (XPS) were used to characterize the modified surfaces. The protein adsorption property of the PVP-grafted surfaces was evaluated using a radiolabeling method. Compared with unmodified silicon surfaces, a Si-PVP60 surface with a PVP thickness of 15.06 nm reduced the level of adsorption of fibrinogen, human serum albumin (HSA), and lysozyme by 75, 93, and 81%, respectively. Moreover, the level of fibrinogen adsorption decreases gradually with an increase in PVP thickness. However, no significant difference in fibrinogen adsorption was found when the PVP layer was thicker than the critical thickness of 13.45 nm.

Topics: Adsorption; Catalysis; Dioxanes; Fibrinogen; Humans; Materials Testing; Models, Chemical; Muramidase; Proteins; Pyrrolidinones; Serum Albumin; Silicon; Solvents; Surface Properties; Water

Conformational features of reduced and disulfide intact hen egg white lysozyme in aqueous 1,4-dioxane and 3-chloro-1, 2-propanediol solutions have been examined using circular dichroism and fluorescence spectroscopy. We find that in presence of 1, 4-dioxane, reduced lysozyme assumes a relatively compact conformational form with secondary structure closer to native state and no tertiary structure as judged by peptide and aromatic CD spectra and ANS binding studies monitored by fluorescence. Further, in presence of 40% (v/v) 3-chloro-1, 2-propanediol, disulfide intact lysozyme (DI-lysozyme) assumes a conformational form with native like secondary structure and no tertiary structure akin to a molten globule state. We correlate our results to kinetic hydrogen- deuterium exchange NMR results of the refolding of lysozyme available in literature and suggest that the conformational forms observed in our study could be models for kinetic intermediates in the refolding of lysozyme.

Topics: alpha-Chlorohydrin; Animals; Chickens; Dioxanes; Disulfides; Female; Muramidase; Oxidation-Reduction; Protein Conformation; Protein Folding

On the basis of scanning microcalorimetry data from literature and our own measurements, we have calculated the changes in preferential solvation of lysozyme upon heat denaturation in six solvent systems: water + methanol, ethanol, propanol [data from Velicelebi, G., & Sturtevant, J. M. (1979) Biochemistry 18, 1180], acetone, p-dioxane [data from Fujita, Y., & Noda, Y. (1983) Bull. Chem. Soc.Jpn. 56, 233], and dimethylsulfoxide [our data Kovrigin, E. L., Kirkitadze, M. D., & Potekhin, S. A. (1996) Biofizika 41, 549-553; Kovrigin, E. L., & Potekhin, S. A. (1996) Biofizika 41, 1201-1206]. These preferential solvation changes are (in effect) the numbers of cosolvent molecules entering or leaving the solvation shell of the protein upon denaturation. It has been shown that for a group of five substances in the initial activity range (approximately up to 0. 3) the denaturational changes of preferential solvation of lysozyme do not depend on the nature of the solvent and depend only on its activity. This suggests that lysozyme does not distinguish these substances in the initial activity range and preferential solvation has a nonspecific character. It has been shown also that preferential solvation DeltaGamma23 does not depend on the pH value at least for dimethylsulfoxide-water solutions. This indicates that the chargeable groups exposed on denaturation do not contribute significantly to preferential interaction of the protein surface with the solution components.

Topics: 1-Propanol; Acetone; Calorimetry, Differential Scanning; Dimethyl Sulfoxide; Dioxanes; Ethanol; Hot Temperature; Methanol; Muramidase; Protein Denaturation; Solutions; Solvents; Thermodynamics; Water

Topics: Dioxanes; Dioxins; Ethanol; Ethylene Chlorohydrin; Muramidase; Research; Spectrophotometry; Tryptophan