CHICKEN ERYTHROCYTE NUCLEOSOMES HAVE A DEFINED ORIENTATION ALONG THE LINKER DNA - A SCANNING FORCE MICROSCOPY STUDY

The orientation of nucleosomes was investigated using scanning force m icroscopy (SFM) of hypotonically spread chicken chromatin. A virtual c ross section parallel to the substrate at half maximum height of the n ucleosomal structure revealed an elliptical shape. The orientation of the major axis of this ellipse was investigated in reference to the di rection of the axis of the nucleosomal chain. An alignment of the nucl eosomes along the nucleosomal chain was observed, with more than 50% o f the nucleosomes aligned with the long axis of the chain within less than or equal to 30 degrees deviation. The alignment distribution peak ed at 10-20 degrees. The application of SFM-based image processing for the structural investigation of a protein-DNA complex demonstrates th e potential for this approach in structural molecular biology.