Basic e'poration advice

[John Dixon]

Hi, I used to make e'comp cells a while back and have just made several
new batches by the same method (the GYT resuspension protocol that was
published in TIBS technical tips a few years ago). 

We have a new GenePulserII now and although the competency of my cells
is OK (1-5x10E8), the time constants when I use my cells are 2-2.5
msec. When I used to do this previously, the constants were around
4.2-4.5msec, and the FAQ suggests 4.5 to 5.5msec. 

Should I be altering something to get that time constant up? - sorry in
advance if it's obvious like halving/doubling something but my
recollection of the equations that govern electricity has evaporated
long ago!

Parameters

Cells    100ul DH10B
DNA      1ul

kV       2.5 for 0.2cm cuvettes 1.8 kV for 0.1cm cuvettes
Ohms     100
uF       25


Cheers

JD

-- 
John Dixon                    Lab 44 (1223) 334131
Wellcome/CRC Institute        Fax 44 (1223) 334089
Cambridge University
United Kingdom CB2 1QR       e-m: jpcd100 at mole.bio.cam.ac.uk