SCANNING FORCE MICROSCOPY OF CHROMATIN

Scanning force microscopy (SFM) is a new method to obtain the topograp hy of surfaces with nanometer-resolution. The ability to image under l iquids makes the technique attractive for biological applications, esp ecially for the determination of the ultrastructure of biomolecules un der native conditions. One growing field of interest is the investigat ion of chromatin and chromatin-related structures. Different levels of chromatin condensation were the subject of several previous SFM inves tigations, from the nucleosomal chain, to the 30-nm fiber, ending with the metaphase chromosome. The SFM yielded new information on such fun damental problems as the core spacing of the nucleosomal chain, the in ternal structure of the 30-nm fiber and the banding mechanism of metap hase chromosomes. Other investigations dealt with the SFM characteriza tion of polytene chromosomes. This paper reviews the state-of-the-art in SFM chromatin research and discusses future developments in this fi eld.