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Conformational characterization of nucleosomes by principal component analysis of their electron micrographs
Author(s) -
ZABAL M. M. Z.,
CZARNOTA G. J.,
BAZETTJONES D. P.,
OTTENSMEYER F. P.
Publication year - 1993
Publication title -
journal of microscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0022-2720
DOI - 10.1111/j.1365-2818.1993.tb03414.x
Subject(s) - nucleosome , macromolecule , principal component analysis , crystallography , electron microscope , chemistry , ellipsoid , biophysics , histone , dna , biology , optics , biochemistry , physics , mathematics , statistics , astronomy
Summary Optimized fixation conditions were determined for protein‐protein and protein‐DNA crosslinking within calf‐thymus nucleosomes in low monovalent salt concentrations. Nucleosomes were examined without heavy‐atom staining by darkfield electron microscopy. The dimensions of these macromolecular complexes and those of HeLa core particles optimally fixed in divalent salt were analysed using principal component analysis. According to this analysis the structure of the calf‐thymus nucleosomes was best presented by a prolate ellipsoid. Particle images had average major and minor axis lengths of 14·1 and 10·5 nm, respectively. In contrast, the HeLa nucleosomes were best modelled by an oblate ellipsoid from the analysis of their images, which had average major and minor axes of 13·3 and 11·5 nm. The applicability of this multivariate statistical analysis to the interpretation of macromolecular images is illustrated and discussed.