Please share experiences of using DEPC reated water?

Errol E.S.Kwan at massey.ac.nz
Thu Mar 22 17:30:50 EST 2001


Calm down.  I was only making a comment on safety and not lecturing
anyone, just making sure that people are aware that sniffing toxic
chemicals isn't normal practise, considering there are quite a few
people using the newsgroup who don't have a strong background with the
use of dangerous chemicals. 

No I don't always take full precautions with most chemicals unless
they have a skull and cross bones on the bottle, then I'm quite
careful.  Although I have not used DEPC if I were to use it I would
still keep in in the fume hood considering it is sometimes used to
extract DNA from cells I wouldn't want it in my body.



On Thu, 22 Mar 2001 15:53:47 -0400, "David F. Spencer"
<dspencer at is.dal.ca> wrote:

>In article <3aafecbc.239815366 at news.massey.ac.nz>, 
>E.S.Kwan at massey.ac.nz (Errol) wrote:
>
>> >Although DEPC is considered to be unstable in water solution it does 
>> >persist at low levels. I DEPC-treated one of my stocks of BLOTTO years 
>> >ago, immediately after placed it at 65C for considerable time to try to 
>> >break down the DEPC, and the solution still has that sweet DEPC smell 
>> >when you take off the cap and sniff it. 
>> 
>> Is it normal practise for you to sniff toxic chemicals?  If you read
>> the warnings is says to work in a fume hood and wear an approved
>> respirator (among other things), so don't you think that you shouldn't
>> be sniffing this stuff?
>
>Oh get a grip!
>
>If your lab practices are dictated by a mindless, hysterical reading of 
>Material Safety Data Sheets (MSDS) you must have a pretty stressful 
>life. The MSDS for _Tris_ calls for a respirator and working with 
>mechanical exhaust (not to mention the special gloves and goggles). 
>Sucrose handling is only slightly less restrictive. If you actually 
>bothered to educate yourself about DEPC or any lab chemical you'd be 
>able to make more reasonable choices and not have the audacity to 
>lecture me (or anyone else) on what is safe and what isn't.
>
>The MSDS has to stretch to embellish the hazard of DEPC by stating that 
>DEPC can react with ammonia to produce urethane, which in animal studies 
>is regarded as a carcinogen. Otherwise DEPC is an irritant, to skin, 
>mucous membranes, etc. Capsaicin is clearly a much bigger "hazard".
>
>DEPC is described at length in a paper by Ehrenberg, Fedorcsak and 
>Solymosy in 'Progress in Nucleic Acids Research and Molecular Biology' 
>vol. 16, 1976. The chemistry of DEPC reactions with DNA are well 
>understood and they are not mutagenic, given that the carbethoxylation 
>of purines (which occurs only in single-stranded DNA/RNA) leads to 
>apurinic sites. In addition, the very poor solubility of DEPC in water 
>coupled with its instability in water, especially in biological 
>environments containing amino acids in general and histidine in 
>particular, means that the chance a DEPC molecule could ever _in vivo_ 
>get near a nucleic acid target is insignificant. Your health is at 
>greater risk while standing in front of a running high speed centrifuge. 
>You're far more likely to be injured or killed in a molecular biology 
>lab by physics rather than chemistry.
>
>The MSDS claims that beta-mercaptoethanol is more dangerous than DEPC, 
>the LD50 level for beta-mercap being less than a third that of DEPC. In 
>fact according to the MSDS beta-mercap is more toxic than phenol, figure 
>that one out. And here I've been working with beta-mercap for more than 
>30 years not realizing I was jeopardizing my life and everyone within 
>smelling distance. We all know that the real problem with beta-mercap 
>occurs when you are working with it but the people around you don't know 
>it and they keep looking at you calling you a pig.
>
>In reality there are relatively few chemicals that constitute a serious  
>threat in the normal molecular biology lab. I don't snort PMSF, I 
>wouldn't mouth pipette azide solutions if I worked with them, and I 
>wouldn't go near acetylaminofluorenes. People have to use some sense 
>when working with acrylamide, obviously phenol and chloroform, plus less 
>common things like actinomycin-D. But when you consider how the average 
>molecular biology lab operates, if there were that many nasty chemicals 
>lying around then people would be dropping like flies. Frankly I'm 
>actually surprised that more lab people don't kill or maim/sicken 
>themselves.
>
>To return to the original issue which was why people treat water, etc. 
>with DEPC. With a few exceptions there is no intelligent reason. It is 
>the same misguided ignorance that prompted someone in this building a 
>few years ago to autoclave phenol. Fortunately I wasn't the person to 
>walk into the autoclave room during that brilliant exercise. That could 
>have resulted in a serious lab mishap caused by strangulation.
>
>And no I can't tell you what DEPC tastes like, but I would imagine 
>beta-mercap doesn't taste that great. I can only handle capsaicin in 
>small amounts, in its natural form of course.
>
>-- 
>David F. Spencer, PhD
>Dept. of Biochemistry and Molecular Biology
>Dalhousie University
>Halifax, Nova Scotia, Canada
>
>dspencer at is.dal.ca




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