This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Talbot, K. J. Articles by Russell, P. J. Search for Related Content PubMed PubMed Citation Articles by Talbot, K. J. Articles by Russell, P. J. Agricola Articles by Talbot, K. J. Articles by Russell, P. J.

Articles

Nuclear Buoyant Density Determination and the Purification and Characterization of Wild-Type Neurospora Nuclei Using Percoll Density Gradients ¹

Biology Department, Reed College, Portland, Oregon 97202

A procedure has been developed using Percoll density gradients for the isolation and purification of nuclei from germinated conidia of wild-type Neurospora crassa St. Lawrence strain 74A. Crude nuclei were purified isopycnically in gradients of Percoll, which is silica coated with polyvinylpyrrolidone. A DNA:RNA:protein ratio of 1:3.5:6.5 was found in purified nuclei. Cytoplasmic contamination was found to be negligible in the nuclear preparations, as determined by electron microscopy and by following a radioactively-labeled ribosome tag during the isolation procedure. A small amount of endogenous ribonuclease activity was detected in the crude nuclear preparations, but not in suspensions of nuclei purified in the Percoll gradients. Ribosomal RNA was extracted from the nuclei in good yields, and electrophoretic analysis indicated the presence of precursor rRNA molecules, as well as the mature 17S and 25S rRNA species. Using the Percoll gradient system, the buoyant density of purified Neurospora nuclei was determined to be 1.08 grams per milliliter based on refractive index measurements.