Dear Engin,
We have just purchased a new iTC200 but are still waiting
for it to arrive. I can update you when we've done some
experiments in the new year to compare with the old
Microcal.
As you say we were attracted due to the reported low
sample useage. You will have to realise though that these
are idealised numbers thye are quoting. For example for
the VP-ITC they say you only need 1.4 ml to fill the
sample cell and 0.3 ml to fill the syringe. In reality you
need to use about 1.8-2.0 ml and 0.4-0.5 ml to avoid
bubbles etc. They gave us some numbers but I can't
remember them exactly, but I think the iTC200 will
realistically need about 0.3 ml to fill the cell rather
than 0.2 ml. My estimate would be you'll need about 1/4 to
1/5 of the sample volume of the VP-ITC realistically.
Which is still a huge improvement though.
They also claim that the iTC200 will be equally sensitive
using the smaller volumes but I guess we'll need to wait
and see. I did get some info from Microcal when I asked
them about a specific system we're studying which has a
tight binding affinity (about 5 nM). The basic answer was
that the only situation where the VP-ITC might be better
is when you are dealing with a binding response that is
about 1 nM and has a low deltaH response (i.e the binding
has a very high c-value). In this case you would need less
volume in the iTC200 but it would need to be more
concetrated (say about 3 fold). I will say that I have a
lot of trust in Microcal and I have confidence that this
instrument will do pretty much what they say it will (and
I'm not being paid honest).
Feel free to contact me again in the new year when we
should have some comparative data.
Cheers,
Brett
On Thu, 6 Dec 2007 11:29:48 -0800
Engin Ozkan <[EMAIL PROTECTED]> wrote:
Fellow crystallographers and biochemists,
This will be off topic. Does anyone have any experience
with the new ITC Microcal is selling (itc200)? They
claim that itc200 requires one seventh the sample
volumes. We're especially interested in an equipment
that would require less sample without sacrificing
signal. We've had difficulty obtaining such information
from MicroCal or other sources.
Engin
-----
Stanford University School of Medicine
Molecular and Cellular Physiology
