Does the postPCR 4-degree hold damage the thermal cycler ??

[chovek69]

Hi guys,

Today, all of a sudden, my boss gave an order to cut the postPCR 4
degree hold on all PCR programs "'cause this could damage the machine
and/or shorten its life"- he said. Could it be possible ? Interestengly
most of the thermal cyclers have an in-built 4 degree holds by default.

I am also interested in how the Peltier is capable of cooling down the
block to 4 degrees as this is opposed by the thermodynamics. Any
suggestions ?

[Jose de las Heras]

Post by chovek69
Hi guys,
Today, all of a sudden, my boss gave an order to cut the postPCR 4
degree hold on all PCR programs "'cause this could damage the machine
and/or shorten its life"- he said. Could it be possible ? Interestengly
most of the thermal cyclers have an in-built 4 degree holds by default.
I am also interested in how the Peltier is capable of cooling down the
block to 4 degrees as this is opposed by the thermodynamics. Any
suggestions ?

I can't say how stressful it is for the block to hold a 4 degree temperature
overnight, but we also have the rule of avoiding overninght 4 degree holds
if possible...

as for the Peltier effect...

http://en.wikipedia.org/wiki/Peltier-Seebeck_effect

Jose

[Louis Hom]

I have no evidence that an overnight 4deg hold causes excessive wear on a
thermocycler, but having touched the hot side of a peltier module cooling
to 4deg, it wouldn't at all surprise me if it did present a problem.

FWIW, I have done many overnight 10deg holds without ill effect on the
DNA. I don't know if it's any better for the instrument, but it makes me
feel better.

[DK]

Post by Louis Hom
I have no evidence that an overnight 4deg hold causes excessive wear on a
thermocycler, but having touched the hot side of a peltier module cooling
to 4deg, it wouldn't at all surprise me if it did present a problem.

It's only a problem if the fan breaks. Peltier itself chips themselves
can withstand high temps very well. Modern Beckman centrifuges
have Peltier-based cooling systems - and these machines are built
to last decades.

Post by Louis Hom
FWIW, I have done many overnight 10deg holds without ill effect on the
DNA. I don't know if it's any better for the instrument, but it makes me
feel better.

For long life of the instrument, occasional sacrifice of the small
animal might be needed :-)

[Jose de las Heras]

Post by DK

Post by Louis Hom
I have no evidence that an overnight 4deg hold causes excessive wear on a
thermocycler, but having touched the hot side of a peltier module cooling
to 4deg, it wouldn't at all surprise me if it did present a problem.

It's only a problem if the fan breaks. Peltier itself chips themselves
can withstand high temps very well. Modern Beckman centrifuges
have Peltier-based cooling systems - and these machines are built
to last decades.

Post by Louis Hom
FWIW, I have done many overnight 10deg holds without ill effect on the
DNA. I don't know if it's any better for the instrument, but it makes me
feel better.

For long life of the instrument, occasional sacrifice of the small
animal might be needed :-)

Shit... I am the shortest one in the lab...

Jose

[Maite Courel]

I have no clues about the damages on thermocycler, but I prefer to hold my

Post by Louis Hom
I have no evidence that an overnight 4deg hold causes excessive wear on a
thermocycler, but having touched the hot side of a peltier module cooling
to 4deg, it wouldn't at all surprise me if it did present a problem.
FWIW, I have done many overnight 10deg holds without ill effect on the
DNA. I don't know if it's any better for the instrument, but it makes me
feel better.
--
______________________________________________________________________________
Lou Hom >K'93
http://www.ocf.berkeley.edu/~lhom/
_______________________________________________
Methods mailing list
http://www.bio.net/biomail/listinfo/methods

[Rory O'Brien]

I think its more to do with the condensation which forms underneath the
block; can't be good for it...

Completely unecessary anyway; samples have already been cycled to 94 degrees
30 or so times, sitting at rt overnight doesn't harm your samples one bit.

- Rory

-----Original Message-----
Sent: 16 June 2006 13:31
Subject: Re: Does the postPCR 4-degree hold damage the
thermal cycler ??
I have no evidence that an overnight 4deg hold causes
excessive wear on a thermocycler, but having touched the hot
side of a peltier module cooling to 4deg, it wouldn't at all
surprise me if it did present a problem.
FWIW, I have done many overnight 10deg holds without ill
effect on the DNA. I don't know if it's any better for the
instrument, but it makes me feel better.

[chovek69]

Thanks all,

I have searched the manuals of all of our 5 different PCR machines and
there were no even a slight note on the possible damage of 4 deg.
holds.

Post by Rory O'Brien
I think its more to do with the condensation which forms underneath the
block; can't be good for it...
Completely unecessary anyway; samples have already been cycled to 94 degrees
30 or so times, sitting at rt overnight doesn't harm your samples one bit.
- Rory

-----Original Message-----
Sent: 16 June 2006 13:31
Subject: Re: Does the postPCR 4-degree hold damage the
thermal cycler ??
I have no evidence that an overnight 4deg hold causes
excessive wear on a thermocycler, but having touched the hot
side of a peltier module cooling to 4deg, it wouldn't at all
surprise me if it did present a problem.
FWIW, I have done many overnight 10deg holds without ill
effect on the DNA. I don't know if it's any better for the
instrument, but it makes me feel better.

[a***@syngenta.com]

Post by Rory O'Brien
Completely unecessary anyway; samples have already been
cycled to 94 degrees 30 or so times, sitting at rt overnight
doesn't harm your samples one bit.

A good point, but what if you're using a proof reading polymerase with
exonuclease activity. Don't you risk your product being chewed up?

A.-