Nucleosome conformation: pH and organic solvent effects.

AUTOR(ES)

Zama, M

RESUMO

Monomer nucleosomes (nu 1) from chicken erythrocyte nuclei were examined in aqueous buffers (8 greater than pH greater than 3) and in solvent mixtures (i.e., water and ethanol, ethylene glycol, dioxane, dimethyl sulfoxide, 2-methyl-2,4-pentanediol, polyethylene glycol, sucrose, or urea). Circular dichroism, laser Raman spectroscopy of nu 1, and the fluorescence of nu 1 labeled with N-(3-pyrene) maleimide on thiol groups of H3 histone were employed to detect conformational transitions in nu 1. The results of pH studies were as follows: 5.5 greater than pH greater than 4.8, suppression of DNA ellipticity and no change of histone alpha-helix; 4.6 greater than pH greater than 4.2 an irreversible increase in the B character of DNA, a slight loss of histone alpha-helix, and a parallel loss of pyrene excimer fluorescence; 4 greater than pH, aggregation of nu 1 and protonation of the DNA bases C and A. Results obtained in the studies of nu 1 in solvent mixtures included the following: sharp conformational transitions that variously involved an increase in the B character of DNA, a slight loss of histone alpha-helix, and a loss of pyrene excimer. Different solvents required different concentrations to effect these conformational changes.

Documentos Relacionados

• Influence of pH on adaptive resistance of Pseudomonas aeruginosa to aminoglycosides and their postantibiotic effects.
• Necleoside conformations. 19. Temperature and pH effects on the conformation of guanosine phosphates.
• Nucleoside conformations. 19. Temperature and pH effects on the conformation of guanosine phosphates
• Permeabilization and fusion of uncharged lipid vesicles induced by the HIV-1 fusion peptide adopting an extended conformation: dose and sequence effects.
• Effects of Environmental pH on the Internal pH of Chlorella pyrenoidosa, Scenedesmus quadricauda, and Euglena mutabilis1