Determination of molecular weights by fluctuation spectroscopy: application to DNA

A method for determining molecular weights of macromolecules by measuring spontaneous concentration fluctuations is described. The method is absolute, rapid, and requires no shearing forces on the molecules. We have applied this technique to the determination of molecular weight of DNA molecules. The molecular weight values obtained for T2 phage DNA (1.14 X 10(8)) and replicating Escherichia coli DNA (3.9 X 10(9)) agree with previous results. By monitoring individual molecules, an estimate of the molecular weight of nuclei and individual chromosomal DNA molecules of Drosophila melanogaster was obtained.