I am not even sure why you are using 14ml falcons for the heat shock I usually use those for recovery and it is not absolutely required. You can do the heat shock in 1.5ml eppies anything between 30 sec to 45 sec should work. You can do the recovery also in the eppie after adding 1ml of SOC or LB without shaking at 37C but the efficiency will be lower. Optimally you do the heat shock if an eppie add 1ml SOC then move the mix to larger vessel for proper aeration anything with a size of 10ml or larger should do and recover at 37C for 1 hour in a shaking water bath.

Hanna Alalam the manufacturer protocol stated that 14 ml falcon were recommended/required because the heat shock step was tailored to it, most of the other transformations I've done have been in the 1.5 mL 's. Thanks for your answer, I will try heat shock as you've suggested.

Hanna Alalam , I have a question. It is true that in real life there is little difference between a 30 s and a 45 s heat shock, but I would expect the rate of heat transfer to be significantly different between an epi and a Falcon tube (different materials, different wall thickness) and hence, I have always assumed that substituting Falcons for eppies would have a larger impact on transformation efficiency than heat shock length (although of course I mostly use eppies for convenience). Have you ever compared directly eppies vs Falcon tubes?

Hello Alejandro Martin I have not compared directly but for sure you are right that there are differences, however, from a practical point of all you care about will be getting transformants (unless you are preparing a genomic library then the efficiency is really important). The shape of the vessel does have an effect for example in neb-10-beta cells it requires a heat shock of exactly 30 sec in the provided vessel to give optimum efficiency. I can , however, point you to a paper where they compared optimal transformation methods for different strains (using 14ml falcons) and the summary is basically as follows:

Prep method:

Hanahan's method most effective for DH5α, XL-1 Blue and JM109 strains.

CaCl2 method was best for SCS110, TOP10 and BL21 strains.

Recovery medium:

SOB is optimal for XL1 blue while is not so good for JM109 and did not have a significant effect on the other strains.

Heat shock:

no significant difference between 45 sec and 90 sec for all tested strains.

As you can seen even with 14ml falcons the heat shock time in itself was not significant therefore I would not expect the reaction to fail if you switch to eppies (you will probably get more than enough colonies) for routine work.

I have used XL1-blue with eppies without any problems and you will get a large number of colonies, however, since they are advertised as "supercomptent" the manual provided with that grade of competence provides a protocol in which they know gives you the highest transformation efficiency (since you bought the high competence grade).

Hope this helps!

source:

Article A comparison and optimization of methods and factors affecti...

Hanna Alalam , great find, thanks a lot for the link!!!