id	author	title	date	pages	extension	mime	words	sentences	flesch	summary	cache	txt
cord-280578-4yxda0mf	Tian, Xinsheng	Molecular cloning, expression, purification and crystallographic analysis of PRRSV 3CL protease	2007-07-28		.txt	text/plain	1535	95	65	Viruses of the order Nidovirales regulate their genome expression by synthesizing two multidomain precursor polyproteins that are subsequently cleaved into functional viral proteins mainly by the 3CL protease (den Boon et al., 1991; Birtley et al., 2005; Snijder et al., 1996; van Aken et al., 2006) . The amplified DNA fragment encoding the PRRSV 3CL protease was inserted into the GST-fusion expression vector pGEX-6p-1 (GE Healthcare) with SmaI/XhoI sites (introduced by PCR primers). For protein expression, the plasmid was transformed into Escherichia coli strain BL21 (DE3) competent cells and the single colony was inoculated into Luria-Bertani (LB) medium with 50 mg l À1 ampicillin (Sigma, USA) at 310 K for overnight growth. For crystallization, the purified protein was concentrated to approximately 20 mg ml À1 and the buffer was exchanged to 10 mM Tris-HCl, 10 mM NaCl, 1 mM EDTA, 1 mM DTT pH 7.5.	./cache/cord-280578-4yxda0mf.txt	./txt/cord-280578-4yxda0mf.txt