Chromosomal nucleoproteins: CD studies on reconstituted nucleohistones from avian erythrocytes

Conformational states of chromatin nu bodies induced by urea

Monomer chromatin nu bodies (nu1) from chicken erythrocyte nuclei were exposed to 0-10 M urea plus 0.2 mM EDTA (PH 7). Alterations in nu1 conformation were examined using hydrodynamic methods (i.e., S, eta, and (formula: see text)), thermal denaturation, circular dichroism, reactivity of histone thiol groups to N-ethyl maleimide, and electron microscopy. The two domains of a nu body (i.e., the DNA-rich shell and the protein-rich core) aeared to respond differently to the destabilizing effects of increasing urea; DNA conformation and stability exhibited noncooperative changes; the core protein structure revealed cooperative destabilization between 4 and 7 M urea. Companion studies on the conformation of the inner histone "heterotypic tetramer" also revealed cooperative destabilization with increasing urea concentration.

Interaction of Pt(II) complexes with DNAs from various sources. A circular dichroism study

The interaction of cis- and trans-Pt(NH3)2Cl2 with DNAs of different base composition was studied by means of circular dichroism (CD) spectroscopy. The spectra obtained indicated a partial transformation of the secondary structure of DNA (B- less than C transition) with an increased helix winding. Subtle differences were noted between the two isomers, possibly related to changes in base orientation due to the different molecular geometries of the P+(II) complexes.