What are the approximate minimum order quantity and lead time for custom recombinant proteins?

To obtain 90% purity and a 300-amino-acid extracellular domain within 8000, it is advisable not to put all the money on one CRO's final delivery. It can be split into two steps: first spend a few thousand to run a small-scale expression test to confirm whether it can be secreted and expressed, whether the molecular weight is correct, and whether the His tag can be recognized by WB; after the test succeeds, pay the remainder for scale-up purification. The contract should clearly state that the deliverables include SDS-PAGE, SEC, endotoxin, concentration, and buffer, and specify that if the purity does not meet the standard, one free rework is allowed. When used for antibody screening, it is not necessarily required to buy several hundred micrograms at once; first take 100 µg for ELISA and preliminary screening, and if it is sufficient, then order more. Regarding lead time, if the CRO has an existing gene library or a mature 293 platform, it can be as fast as 3 to 4 weeks, but do not make too firm a commitment.

A 300-amino-acid human membrane protein ectodomain with a His tag, 90% purity, no GMP required—this kind of request is already considered relatively routine among CROs. The large quote variations mainly come from the expression system: secretory expression in HEK293 or Expi293 is closest to native folding and glycosylation, but it is expensive; insect or E. coli expression is cheaper, but glycosylation and disulfide bonds may differ, so for antibody screening it depends on whether your downstream application requires native epitopes. Under 8,000, you can generally only get a small scale, such as 0.5 to 1 mg delivered; anything more or requiring strict QC will be very tight. It is recommended to specify the purity requirement from above 90% to reduced and non-reduced SDS-PAGE plus SEC, rather than just writing a number.

For conventional CRO services, the minimum order quantity for custom proteins like this is usually calculated per project, with delivery of 0.5 to 1 mg or a fixed package size, not based on the number of clones. The lead time, from gene synthesis, codon optimization, subcloning, and expression testing to purification, is generally 4 to 6 weeks; however, for membrane protein extracellular domains, if low expression, aggregation, or multimerization occurs, it may be extended to 8 weeks or even longer. Before signing the contract, have the CRO clarify whether expression condition screening, solubility testing, and one failure retry are included. To cover these with an 8,000 budget, it is advisable to choose a company with experience in similar membrane protein extracellular domains and require interim reports: completion of gene synthesis, Western blot of the expression test supernatant, and SDS-PAGE after purification, as this helps control risk.