![\"\"](\"http:\/\/www.lablit.com\/images\/Precise.jpg\")
\nSignificant digits<\/strong> A Gilson P2 Pipetteman dialled to 0.165 microliters<\/em> <\/p>\n
\nThis obsession extends to my pipetting. Yesterday morning, I did a few calculations and worked out that I’d need to add 0.165 microliters of an RNA oligo duplex to achieve the correct concentration. Of course I could have rounded to 0.17, because my trusty P2 is probably not that accurate, but I didn’t. (And yes, I brought the final volume up to 10 microliters with 9.835 microliters of water, though on a P20 instrument, the closest you can dial without microscopic vision is about 9.84). <\/p>\n
\nI’ve always been like this. In school, I remember being affected very deeply by a math class discussion about precision<\/em> versus accuracy<\/em>: the classic illustration of the arrow-pierced bullseye target is still emblazoned on my long-term memory (see Wikipedia<\/a> for a version of this). Even when I am cooking, I tend to measure water to the bottom of the meniscus in the measuring cup, and dry ingredients to two decimal places on our swanky digital scale. I may not always be accurate, but by God am I precise. <\/p>\n \nSo is this behavior of any real value in the modern molecular biology laboratory, or is it all a sort of superstition? I guess I think that if you measure things carefully with the same instrument, all of your manipulations should be precise, if not accurate, on a relative scale. I know that there is no effective difference between 0.043 and 0.04 in practical biological terms for the experiments I’m doing, but it’s possible that my experiments are more reproducible as a result, and possibly more comparable when done on separate occasions. <\/p>\n \nI must confess, however, that I’ve caught myself relaxing a little bit on this point recently, for processes that I am pretty sure are fully robust. Only this morning I threw caution to the wind and diluted an antibody 1:100 in buffer by adding 1 microliter to 100 microliters instead of to 99. And I felt a lovely illicit little thrill in the process.<\/p>\n \nSometimes you have to live dangerously.<\/p>\n","protected":false},"excerpt":{"rendered":" My lab-side manner could charitably be described as ‘cautious’ \u2013 although ‘paranoid’ is probably closer to the truth. I am reluctant to take shortcuts in an experiment, for example, even when I suspect that it will make little difference. And … Continue reading