I know co-workers of mine routinely leave their water in the hood after they finish PCR and the water has been repeatedly exposed to UV. They have not seen any negative impact on their PCRs.

Hello there,

if you only put water (nothing containing DNA like your primers or your DNA matrix), there souldn't be any problem with that. To my knowledge, UV radiation doesn't do anything to water.

My opinion is: you can use this water for your PCR,

Cheers

If this was pure water that did not contain any chemicals or DNA/RNA/enzymes, then it's OK.

I am agree with Vicent and Natalia, if ony is water, nothing could happend =D

If you are doubting, you can use new water, and use this water to other thing.

In theory the water should OK. It is a possibility that the UV may have a photoxidation effect if you are using a polystryrene container ( eg tissue culture plate) as UV irradiation has been used to modify microtitre plate surfaces, though what effect this will have on the water I don't know.

Ian

I know co-workers of mine routinely leave their water in the hood after they finish PCR and the water has been repeatedly exposed to UV. They have not seen any negative impact on their PCRs.

As long as we are discussing pure water without primers etc. I would use it without a doubt:-)

UV has no effect on pure water. As the others have stated, you can use this for your PCR.

thank you all for your quick response. Yeah, that was pure water , without any primers & enzymes. As you all are saying that uv doesnt effect pure water, i think i should use it for further reactions. I'll inform you if i got any negative results.

thank you all.

one more thing to ask.... if pure water is contaminated with some bacterial dna, Can uv radiation be used to disinfect it ?

The short answer is no:-)

Pure as in ultrapure water is known to be corrosive and if stored in wrong plasticware can cause leaching of certain materials that might effect the PCR especially in the presence of UV as it will accelerate the process.

Though its rare with lab grade good plasticware, it is possible.

as quoted here "Storage of ultrapure water

Storing ultrapure water will introduce leachables to the water. Plastic containers leach out organics and some ions. Glass containers do not leach out as much organics, but they can introduce ions into the water. Storing ultrapure water would also encourage the proliferation of bacteria. "

This is from here http://www.millipore.com/lab_water/clw4/lc_ms

But for all intents and purposes its seem like a long shot that this would happen, the source can be a bad filteration unit or inhibitors co extracted with the DNA itself, is more likely explanation.

And to answer the part of using UV to disinfect bacterial DNA in water..its a NO.

The water treatment with UV before PCR, can not cause any problem. On the contrary, it is good practice to expose the materials used in PCR (plastic, micropipettes, and even the water) to UV radiation before starting to prepare the PCR mix. Exposicion at UV, can form dimers between two consecutives pyrimidines (especially between two thymines) in this way it is achieved that any contaminating DNA that might be present in the materials becomes unable to serve as template. Then the contaminant DNA can not be copied by the polymerase during PCR, avoiding the formation of nonspecific products.

Anyway, I do not recommend it as a good method to disinfect water. You should always use ultrapure water

If you leave the UV sterilization of a cleanbench on for too long, there could be high concentration of ozon developing within the closed bench. We've seen problems with that in the past. 20 min of exposure shouldn't be a problem, though.

As Guillermo mentioned UV is absorbed by DNA and leads to dimers that will block replication on the strands. Therefore you could use it to "decontaminate" your water sample. However the DNA will still be bound by the polymerase and can actually trap it during elongation (it will be released during denaturing step though). So if you have a huge contamination with DNA you can decrease the PCR efficiency and might want to rather use something else to actually get rid of the contaminating DNA (heparin resin e.g.). For small amounts of contaminating DNA it should work though if you expose it long enough.

When talking about UV, you should understand the spectral composition of your UV source. UVC (250-280nm) has bactericidal effect and is used for disinfection. UVB (280-320nm) and UVA (320-400) do not affect the clear water.

Now you have the plastic surface sterile and damaged, but most of uv radiation if not all has been absorbed by the plasticware

You have asked a very good question for all those who want to improve their research methodology: Look, never do any research with a biased mind. Be open to all types of observation that you get. In this case I will not give you the answer (which is very simple), but I want you to do the study and then come back to ask the reason for what you have observed.

I just worry about the ozon will affect the PCR reaction.

20 minutes shouldn't be a problem. However, I agree with Francesc that if the water is in plastic probably the UV light will never reach it (depends of the plastic, but many of them absorb UV). If the water is in a glass bottle the UV will reach the water… and 20 minutes shouldn't be a problem (However if any ozone has been formed, like many people here is worried about, the quantity will be so small that as soon as you open the bottle or recipient to take the water it will be lost in the atmosphere)