Recombinant protein expression
Getting from a plasmid to purified protein means picking a host that folds and modifies your target correctly, then capturing it fast on a resin matched to whatever tag you fused. E. coli with a λDE3 lysogen is the default for simple soluble targets; insect and mammalian systems earn their overhead when your protein needs post-translational modification the bacterial host can't do.
Transform the expression host
Move your expression construct into a λDE3 lysogen strain (BL21(DE3), or BL21(DE3)pLysS for tighter basal repression of toxic targets) carrying the T7 RNA polymerase your cloning strain lacks.
Express under selection
Grow under antibiotic selection for the resistance marker on your vector, and, for insect or mammalian hosts, in an expression-formulated serum-free medium suited to the cell line and expression system.
Capture by tag
Lyse and load onto an affinity resin matched to your fusion tag, Ni-NTA or cobalt-IDA for a His tag, glutathione agarose for GST, and elute with imidazole gradient or reduced glutathione, respectively.
Confirm expression by gel
Run induced vs. uninduced lysate and eluate against a protein ladder on SDS-PAGE to confirm the target is expressed, soluble, and enriched at the expected molecular weight before scaling up.
Every product below is pulled live from the catalog, not hand-curated marketing copy.
E. coli, insect, or mammalian expression?
E. coli is fastest and cheapest and handles simple, non-glycosylated soluble targets well. Insect (baculovirus) and mammalian systems cost more time and money but correctly fold, disulfide-bond, and glycosylate complex or secreted proteins that misfold or aggregate as inclusion bodies in bacteria.
BL21(DE3) or BL21(DE3)pLysS?
Plain BL21(DE3) is the default. Reach for the pLysS variant when your target is toxic to the host or prone to leaky pre-induction expression, the pLysS-encoded T7 lysozyme suppresses basal T7 RNA polymerase activity before induction, at some cost to eventual yield.
His tag or GST tag?
A His tag is small, rarely interferes with folding or activity, and captures on inexpensive Ni-NTA or cobalt resin under native or denaturing conditions. A GST tag is much larger, can improve solubility of a difficult target, and its glutathione-resin elution is gentle (physiological pH, no imidazole), useful when imidazole would interfere with a downstream assay.
Ni-NTA or cobalt for a His-tagged capture?
Ni-NTA gives higher binding capacity and is the default; cobalt-IDA binds more selectively (lower capacity, less background from native E. coli histidine-rich proteins), worth switching to if a Ni-NTA prep keeps showing the same contaminating bands.
More application workflows, curated products, and category links live on the applications hub. Datasheets, SDS, and Certificates of Analysis are under Documents.