PMID-sentid	Pub_year	Sent_text		comp_official_name	comp_offsetprotein_name	organism	prot_offset
9056490-3	1997	With repeated cycles of freezing and thawing as a first step, the purification of the recombinant ch-DHFR to homogeneity requires only one further step, gel filtration on a Sephadex G-75 column with 85-90% enzyme recovery, two to three times higher than that obtained with the commonly used affinity chromatography on a methotrexate-Sepharose column.	Sepharose	333-342	dihydrofolate reductase	Escherichia coli	101-105