scholarly journals Internal Motion of Chromatin Fibers Is Governed by Dynamics of Uncompressed Linker Strands

2020 ◽  
Vol 119 (11) ◽  
pp. 2326-2334
Author(s):  
Rajib Basak ◽  
William Rosencrans ◽  
Indresh Yadav ◽  
Peiyan Yan ◽  
Nikolay V. Berezhnoy ◽  
...  
Keyword(s):  
Internal Motion ◽  
Chromatin Fibers

Localization of DNA in chromatin using ESI and osmium ammine staining

1990 ◽  
Vol 48 (3) ◽  
pp. 116-117
Author(s):  
C.L. Woodcock ◽  
R.A. Horowitz ◽  
D. P. Bazett-Jones ◽  
A.L. Olins
Keyword(s):  
Spectroscopic Imaging ◽  
Energy Losses ◽  
Electron Spectroscopic Imaging ◽  
Feulgen Reaction ◽  
Specific Location ◽  
Eukaryotic Nucleus ◽  
Chromatin Fibers ◽  
Patiria Miniata ◽  
Model Structures

In the eukaryotic nucleus, DNA is packaged into nucleosomes, and the nucleosome chain folded into ‘30nm’ chromatin fibers. A number of different model structures, each with a specific location of nucleosomal and linker DNA have been proposed for the arrangment of nucleosomes within the fiber. We are exploring two strategies for testing the models by localizing DNA within chromatin: electron spectroscopic imaging (ESI) of phosphorus atoms, and osmium ammine (OSAM) staining, a method based on the DNA-specific Feulgen reaction.Sperm were obtained from Patiria miniata (starfish), fixed in 2% GA in 150mM NaCl, 15mM HEPES pH 8.0, and embedded In Lowiciyl K11M at -55C. For OSAM staining, sections 100nm to 150nm thick were treated as described, and stereo pairs recorded at 40,000x and 100KV using a Philips CM10 TEM. (The new osmium ammine-B stain is available from Polysciences Inc). Uranyl-lead (U-Pb) staining was as described. ESI was carried out on unstained, very thin (<30 nm) beveled sections at 80KV using a Zeiss EM902. Images were recorded at 20,000x and 30,000x with median energy losses of 110eV, 120eV and 160eV, and a window of 20eV.

Apparitions and Atmosphères (1958–61)

2017 ◽  
Author(s):  
Benjamin R. Levy
Keyword(s):  
Electronic Music ◽  
Internal Motion ◽  
Orchestral Works ◽  
Compositional Technique

This chapter examines Ligeti’s breakthrough orchestral works Apparitions and Atmosphères. These successful compositions translate some of the ideas developed in the electronic music studio into orchestral writing, in particular, techniques for organizing rhythm and for handling sound masses to create a static surface with a sense of internal motion. In interviews Ligeti claimed to have attempted to move in this direction while still in Hungary with the unfinished pieces Víziók and Sötét és Világos. A comparison of the extant sketches for these works shows the degree to which his experiences in the electronic studio resulted in a refinement of compositional technique, nuanced textures, and original orchestration.

scholarly journals Nucleosome Stacking Defines The Structural And Mechanical Properites Of Chromatin Fibers

2009 ◽  
Vol 96 (3) ◽  
pp. 35a
Author(s):  
Fan-Tso Chien ◽  
Maarten Kruithof ◽  
Andrew Routh ◽  
Daniela Rhodes ◽  
John van Noort
Keyword(s):  
Chromatin Fibers

scholarly journals Chromatin fibers observed in situ in frozen hydrated sections. Native fiber diameter is not correlated with nucleosome repeat length.

1994 ◽  
Vol 125 (1) ◽  
pp. 11-19 ◽  
Author(s):  
C L Woodcock
Keyword(s):  
Cell Types ◽  
Repeat Length ◽  
Strong Positive Correlation ◽  
Whole Cells ◽  
Chromosome Architecture ◽  
Chromatin Fibers ◽  
The Moment ◽  
Chicken Erythrocytes ◽  
Patiria Miniata

Chromatin fibers have been observed and measured in frozen hydrated sections of three types of cell (chicken erythrocytes and sperm of Patiria miniata and Thyone briareus) representing an approximately 20-bp range of nucleosomal repeat lengths. For sperm of the starfish P. miniata, it was possible to obtain images of chromatin fibers from cells that were swimming in seawater up to the moment of cryo-immobilization, thus providing a record of the native morphology of the chromatin of these cells. Glutaraldehyde fixation produced no significant changes in the ultrastructure or diameter of chromatin fibers, and fiber diameters observed in cryosections were similar to those recorded after low temperature embedding in Lowicryl K11M. Chromatin fiber diameters measured from cryosections of the three types of nuclei were similar, a striking contrast to the situation for chromatin isolated from these cell types, where a strong positive correlation between diameter and nucleosomal repeat length has been established. The demonstration of chromatin fibers in unfixed whole cells establishes an unequivocal baseline for the study of native chromatin and chromosome architecture. The significant differences between chromatin fibers in nucleo and after isolation supports a previous observation (P. J. Giannasca, R. A. Horowitz, and C. L. Woodcock. 1993. J. Cell Sci. 105:551-561), and suggests that structural studies on isolated material should be interpreted with caution until the changes that accompany chromatin isolation are understood.

Partial denaturation of small chromatin fragments: direct evidence for the radial distribution of nucleosomes in folded chromatin fibers

1998 ◽  
Vol 111 (12) ◽  
pp. 1707-1715
Author(s):  
A. Bermudez ◽  
S. Bartolome ◽  
J.R. Daban
Keyword(s):  
Radial Distribution ◽  
Direct Evidence ◽  
Dna Loops ◽  
Entry Points ◽  
Partial Denaturation ◽  
Chromatin Fibers ◽  
High Concentrations ◽  
Chicken Erythrocytes ◽  
Top View ◽  
Electrostatic Repulsions

To examine the internal structure of chromatin fibers, we have developed procedures for partial denaturation of small chromatin fragments (8–30 nucleosomes) from chicken erythrocytes. Electron micrographs of samples prepared under conditions that cause nucleosome dissociation show rods and loops projecting from short compact fibers fixed by glutaraldehyde in 1.7 mM Mg2+. According to previous studies in our laboratory, these images correspond to the top view of partially denatured fibers. Our results indicate that rods and loops consist of extended duplex DNA of different lengths. DNA in loops is nicked, as demonstrated by experiments performed in the presence of high concentrations of ethidium bromide. Length measurements indicate that the radial projections of DNA are produced by unfolding of nucleosomal units. Loops are formed by DNA from denatured nucleosomes in internal positions of the fiber; DNA from denatured nucleosomes in terminal positions form rods. Our micrographs show clearly a radial distribution of DNA loops and rods projecting from fibers. Rods are orthogonal to the surface of the chromatin fragments. Considering that the high ionic strength used in this study (0.8-2.0 M NaCl) neutralizes the electrostatic repulsions between rods and fiber, this observation suggests that rods are extensions of nucleosomes radially organized inside the fiber. The position of the entry points of DNA loops into the fiber could be influenced by constraint on loops, but our results showing that the arc that separates these points in dinucleosome loops is relatively short suggest that consecutive nucleosomes are relatively close to each other in the folded fiber.

Internal Motion in Polystyrene

1977 ◽  
pp. 486-488
Author(s):  
Gwynne Jones ◽  
David Caroline
Keyword(s):  
Internal Motion
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