Fluorescence anisotropy decay of ethidium bromide bound to nucleosomal core particles.

We have measured the fluorescence anisotropy decay of ethidium bromide bound to nucleosomal core particles (145 DNA base pairs) for very small values of the binding ratio (0.0005 less than or equal to r less than or equal to 0.01).

Immunochemical detection of changes in chromatin subunits induced by histone H4 acetylation.

Native, reassociated, and reconstituted core particles from chicken erythrocytes were compared by both biophysical and immunochemical methods. No significant difference between the three types of core particles could be demonstrated by electron microscopy, circular dichroism, or immunochemical analysis with antisera to histone H2B, H2A, and H3. Core particles were also reconstituted with calf thymus non-acetylated H3, H2A, and H2B with either mono-, di-, or tri-acetylated H4 isolated from cuttle -fish testes.

Core particle stability critically depends upon a small number of terminal nucleotides.

An apparently homogeneous population of core particles is in fact composed of three subpopulations which behave differently when exposed to a high concentration of ethidium bromide or to 0.6 M NaCl. These subspecies have been identified by the use of several techniques, viz.

The use of various buffers in the preparation of human lymphocytes for SEM observation.

A study is presented of various buffers utilized in the preparation of human lymphocytes for scanning electron microscopy. Of nineteen different buffers tested, Hanks' balanced salt solution +0.04 mol sucrose appeared most adequate for satisfactory preservation of lymphocyte surface architecture.

Distribution of antigenicity in chicken erythrocyte histone H5.

We have compared the inhibitory strengths of eight peptides from chicken histone H5 to that of the parent protein (189 residues) in complement fixation by guinea pig anti-H5 serum complexed with the homologous histone. Two precisely delineated regions (residues 59 to 65 and 94 to 99) and two less-defined regions (between 66 and 93; 100 and 189) are depicted. The sequences of particular consequences are quite conserved in avian histone H5 while the most variable N-terminal portion of 31 residues has no inhibitory effect.

Isolation and physical characterization of a stable core particle.

Core particles were prepared from mature chicken erythrocytes chromatin, according to the method of Lutter (J. Mol. Biol.

[Analyses of histones and of nucleosomal DNA of normal and vitamin B 12 starved Euglena].

An extraction and electrophoresis of histones from normal and starved Euglena cell nuclei allows us to show the presence of five types of histones in the two cases but a lower degree of acetylation appears in H4 histone from starved cells. It was shown that DNA repeat length from the two kinds of chromatin is comparable (225 b.p.

Ethidium bromide binding to core particle: comparison with native chromatin.

Ethidium bromide intercalation into DNA of nuclease digested erythrocyte chromatin and core particle, was followed at low ionic strength by fluorescence measurements, equilibrium dialysis using 14C labelled dye, circular dichroism and electron microscopy. High affinity binding sites in the chromatin are no more present in the core particle, i.e.

Location of the globular region in chicken erythrocyte histone H5.

Chicken erythrocyte histone H5 has been cleaved by acetic acid hydrolysis at the two aspartic acid residues 65 and 99 and the 4 peptides (1-65), (66-185) (1-99) (100-185) recovered in a pure form. 270 MHz magnetic resonance and circular dichroic studies show that the two C-terminal peptides are unable to form secondary or tertiary structure. The N-terminal peptides however, form both secondary and tertiary structure.

The fine structure of Strongylocentrotus purpuratus testes.

The fine structure os Strongylocentrotus purpuratis testes has been examined. No obviously important differences appear to exist between the description reported here and the published fine structure of testes obtained from other sources. The most useful fixative was found to be a mixture of glutaraldehyde-paraformaldehyde.

Circular dichroism as a probe of DNA structure inside reconstituted nucleohistones.

Reconstituted nucleohistones were obtained by mixing in given conditions acid extracted histones and eukaryotic DNA. The histone/DNA ratio (w/w) was in the range 0.35 - 0.

Structural studies of chicken erythrocyte histone H5.

Spectroscopic studies (nuclear magnetic resonance, circular dichroism and infrared) have been carried out on chicken erythrocyte histone H5 and on three peptides cleaved therefrom: 1-31, 32-197 and 58-197. It is shown that at ionic strengths above o.1M part of the H5 molecule takes up a globular conformation containing 14% alpha helix but no beta sheet structure.

Non-histone chromosomal proteins easily extractible from chick erythrocytes.

Those non-histone chromosomal proteins which are easily extractible from chick erythrocytes differ substantially from proteins similarly extracted from other tissues of various species. Although a protein P1 was isolated along with histone H1 by extraction of calf thymus chromatin with HC1O4, the same procedure did not extract this protein from chick erythrocyte chromatin of either normal or regenerating blood. Likewise , non-histone proteins extracted with 0.

Comparison between histones FV and F2a2 of chicken erythrocyte. I. Structure, stability and conformation of the free proteins.

Purified chicken erythrocyte histones FV and F2a2 were studied by means of circular dichroism as a function of ionic strength and temperature. The percentage of alpha-helical regions was calculated by comparison with reference spectra obtained with four standard proteins of known tertiary structure. Maximal alpha-helical organization, reached in high ionic strength, was estimated to 14% and 23% for FV and F2a2 respectively.

Comparison between histones FV and F2a2 of chicken erythrocyte. II. Interaction with homologous DNA.

The conformation and stability of artificial complexes between chicken erythrocyte DNA and homologous histones FV and F2a2 was studied by circular dichroism (CD) and thermal denaturation followed by both absorbance and CD measurements. The complexes are made after a stepwise potassium fluoride gradient dialysis without urea and studied at low ionic strength (10-minus 3 M). 1) No structural changes of the DNA can be detected up to r equals 0.