[Taxacom] Palcohol?

Tue Apr 22 15:12:08 CDT 2014

Keep in mind that hydrolysis is not the only DNA killing process. Nucleases are a major problem as well and even 96% Ethanol, although displacing most of the water, does not shut down nuclease activity. This particularly applies to enzyme-rich tissue such as liver or spleen (or most internal organs, for that matter). For this reason, many vertebrate samples collected in the 'good old times' by fixing chunks of liver in ETOH cannot be used for high throughput analysis of mitochondrial DNA. I would discourage the assumption that if you simply fix your specimen in Ethanol, you are guaranteed to retain its DNA intact for ages to come. It will still degrade over time, even quicker than in a dry specimen. For arthropods that can be preserved dry for morphology, it is best not to use ethanol at all, unless there is high ambient humidity. For specimens that have to be preserved in Ethanol, it is a good idea to store them at low temperatures until they are sampled for molecular analyses. 

----- Original Message -----

From: "David Campbell" <pleuronaia at gmail.com> 
Cc: taxacom at mailman.nhm.ku.edu 
Sent: Tuesday, April 22, 2014 12:43:05 PM 
Subject: Re: [Taxacom] Palcohol? 

I think that the actual culprit for trashing DNA is water. The problem 
with isopropanol is that it is not as effective for replacing the water as 
ethanol is, allowing the DNA to degrade. Similarly a low concentration of 
ethanol won't preserve the DNA. Depending on the size and composition of 
the taxon, the water from the tissues may significantly dilute the 
preservative. 

On Tue, Apr 22, 2014 at 11:23 AM, Ken Kinman <kinman at hotmail.com> wrote: 

> Hi all, 
> I've never stored insects in alcohol, but I've read that both 
> ethanol and isopropanol can make them brittle (some say ethanol is worse, 
> others say isopropanol is worse). But there does seem to be agreement that 
> concentrations above 70% of either of them can definitely make them 
> brittle. Anyway, I am wondering if the addition of glycerol helps mitigate 
> that problem. A few of my spider specimens were saved from dehydration 
> when the alcohol evaporated over the years, but the glycerol kept them 
> moist. -----------------Ken 
> P.S. I couldn't find anything about DNA being trashed by isopropanol. It 
> is often used to extract DNA, so does it only trash the DNA over a long 
> time period? Most of my spiders were collected in the 1970s. 
> 
> 
> ------------------------------------------------------------------------------------------------------------ 
> 
> > On 22.04.2014 13:15, John Noyes wrote: 
> > > Apart from trashing DNA, it also trashes many types of smaller 
> > > insects by making them so stiff that the become difficult/impossible 
> > > to card-mount or put on slides. The same also goes for IMS. 
> > > 
> > > John 
> > > 
> > > John Noyes 
> > > Scientific Associate 
> > > Department of Life Sciences 
> > > Natural History Museum 
> > > Cromwell Road 
> > > South Kensington 
> > > London SW7 5BD 
> > > UK 
> > > jsn at nhm.ac.uk 
> > > Tel.: +44 (0) 207 942 5594 
> > > Fax.: +44 (0) 207 942 5229 
> > > 
> > > Universal Chalcidoidea Database (everything you wanted to know about 
> > > chalcidoids and more): 
> > > www.nhm.ac.uk/chalcidoids 
> > > 
> > > 
> > > -----Original Message----- 
> > > From: taxacom-bounces at mailman.nhm.ku.edu 
> > > [mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Daniel 
> > > Janzen 
> > > Sent: 22 April 2014 22:38 
> > > To: Neal Evenhuis 
> > > Cc: taxacom at mailman.nhm.ku.edu 
> > > Subject: Re: [Taxacom] Palcohol? 
> > > 
> > > It is my understanding that isopropyl alcohol trashes DNA or 
> > > otherwise makes it very difficult to extract. Think on that for 
> > > pickling museum specimens. I know of no circumstance where you can 
> > > get (or ship) isopropyl but not get (or ship) 80-95% ethanol. 
> > > 
> > > Just a thought. Dan Janzen 
> > > 
> 
> 
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> Celebrating 27 years of Taxacom in 2014. 
> 

-- 
Dr. David Campbell 
Assistant Professor, Geology 
Department of Natural Sciences 
Box 7270 
Gardner-Webb University 
Boiling Springs NC 28017 
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Celebrating 27 years of Taxacom in 2014. 