[Spm] Water quality (Don Chernoff at ASM)

[Cirnaym Fircnaym]

Dear Dr. Chernoff, 
                    We have had the exact same problem in our lab; that is, imaging DNA on mica in air, and finding particulates on the surface. We spent a long time trying to get to the bottom of it, and to the best of our knowledge the impurities actually come from two different sources. When making control samples incubated and washed with water from various sources (MilliQ, distilled, tap etc.) we noticed a variation between and within sources, and found that BPC Grade water from Sigma (W3513 - Biotechnology Performance Certified) gave the cleanest and most reproducible results. The other source of impurities we found was the nitrogen stream used to dry the samples after washing. What exactly these particulates are we never found out, but by running the nitrogen through a simple, home-made bubble trap, they largely went away. 
Hope this sorts your images out. Please feel free to contact me privately at smc90 at cam.ac.uk if you have any further questions. 

     Regards, 

          Stewart Carnally 




      
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