Hello, I am used to purified HIV-1 NC protein which contains two zinc fingers. Protocol uses PEI precipitation. (See Dynamical behavior of the HIV-1 nucleocapsid protein *Journal of Molecular Biology* <http://www.sciencedirect.com/science/journal/00222836> Volume 279, Issue 3 <http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%236899%231998%23997209996%23314103%23FLA%23&_cdi=6899&_pubType=J&view=c&_auth=y&_acct=C000035758&_version=1&_urlVersion=0&_userid=5279227&md5=fce969b8b79dec76169a85659cfb9b22>, 12 June 1998, Pages 633-649). The pH has to be carfefully checked, it depends on your protein pI. And PEI must be added drops after drops under vigourous stirring.
Pierre Barraud Laboratoire de Cristallographie et RMN biologiques Faculté de Pharmacie, CNRS UMR 8015, case 48 4 avenue de l'observatoire 75006 PARIS tel:33 1 53 73 15 72 fax: 33 1 53 73 99 25 http://lcrbw.pharmacie.univ-paris5.fr
