Time seems to be in short supply for researchers these days, there never seems to be enough of it. Whether you're staying up to all hours of the night preparing that talk or desperately trying to put the finishing touches on the paper that has to be in FedEx's hands by 5pm, the one phrase that keeps repeating in your mind is "if I only had a little more time".
Well, Invitrogen is trying to help.
Unfortunately they're not going to be able to help much with the talk, but what they are doing is cutting down the amount of time that you spend cloning your PCR products. Their TOPO TA Cloning System requires only 5 minutes to go from PCR product to transformation and you don¹t even have to add ligase. Invitrogen has done this by taking advantage of the ligation activity of topoisomerase I and the nontemplate-dependent terminal transferase activity of taq (which adds a single deoxyadenosine (A) to the 3' ends of PCR products). By coupling topoisomerase I to the ends of a linearized vector containing single, overhanging 3' deoxythymidine (T) residues, Invitrogen has created an "activated" vector that will spontaneously ligate PCR products in 5 minutes at room temperature. The ligation product is then ready for transformation into either electro- or chemically competent cells. If you buy the TOPO TA Cloning Kit, you also get Invitrogen¹s TOP10 or TOP10F' competent cells, which take a little over an hour to transform.
According to the quality control blurb that comes with the protocol book for the TOPO TA Cloning Kit, the pCR2.1 TOPO vector yields > 95% white colonies (when using blue/white screening) and that of the 95% white colonies, >90% will contain the correct PCR product. In my experience, the > 95% figure may be a bit optimistic on their part (it's probably more like >75% or so, although I must admit that I don't always count all the colonies on a plate), but the vast majority (>90%) of the white colonies that I pick do contain PCR product. The total number of colonies that you get after transformation is usually on the low-side (indicating that not all of the PCR product is being efficiently ligated), but when you¹re cloning PCR products, you don¹t always need 10^7 colonies.
The only other beef I have with this product is its price. The Topo TA Cloning Kit comes with enough vector and competent cells for 20 reactions (also available in 40 reactions with a slight price break) all for around $300 (US). That's definitely on the pricey side, but I guess that's the going rate for saving time.