Circular dichroism of two conformations of poly[d(G-C)] induced by low pH.
AUTOR(ES)
Antao, V P
RESUMO
Circular dichroism (CD) and UV absorption data showed that poly[d(G-C)] (at 0.09M NaCl, 0.01M Na+ (phosphate), 20 degrees C) underwent two conformational transitions upon lowering of the pH by the addition of HCl. The first transition was complete at about pH 3.0. The second transition was complete upon lowering the pH to 2.6 or upon raising the temperature, at pH 3.0, to about 40 degrees C. There was no indication of denaturation during either transition. The CD spectrum for the second acid conformation had large CD bands including a positive one at 288nm, a characteristic associated with C X C+ base-pairs. Electron microscopy showed no significant formation of condensed supramolecular aggregates corresponding to the first or second acid forms of poly[d(G-C)]. On the basis of spectral data, electron microscopy, and proton-uptake measurements, we propose models for the secondary structures that poly[d(G-C)] adopts in its two acid conformations.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=341357Documentos Relacionados
- CD of six different conformational rearrangements of poly[d(A-G).d(C-T)] induced by low pH.
- Unusual proton exchange properties of Z-form poly[d(G-C)]
- Comparative transcription of right- and left-handed poly[d(G-C)] by wheat germ RNA polymerase II.
- Poly(dG).poly(dC) at neutral and alkaline pH: the formation of triple stranded poly(dG).poly(dG).poly(dC).
- Differential promotion and suppression of Z leads to B transitions in poly[d(G-C)] by histone subclasses, polyamino acids and polyamines.