Although the path length of NanoDrop is fixed. 1 ul may not form good liquid column. One trick is to spot a little bit more sample, 2-4 ul, on Nanodrop, specially for concentrated protein samples with glycerol and E. coli culture. It eliminate the bubble problem.
To get good reading, a new drop need to be used for each measurement. The liquid column may not form well when repeat with the same drop. Take a look at the liquid column. Nanodrop actually measures the sample twice for each reading. In consistent measurements give error message. As all the machines with moving parts, periodical maintenance is needed to give good readings. There may be a huge difference between Bradford and A200. In some cases none of them gives the true concentration. I wouldn't abandon Bradford, which by itself is very consistent if done right. Indicating how protein concentration is measured in publications will help the research community. Cheers, Chun -----Original Message----- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Bjørn Panyella Pedersen Sent: Thursday, June 16, 2011 1:19 PM To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Nanodrop versus Nanophotomter Pearl versus good old Bradford. On 2011-06-16 13:06, Filip Van Petegem wrote: > Even if evaporation is not an issue, one has to take pipetting errors into account > when dealing with small volumes. The relative error on 1-2ul is a lot bigger than on 50ul. True, but the nanodrop works independent of volumes, since it has a fixed pathlength. 1ul loaded will give the same result as 2ul loaded. hth -Bjørn -- Bjørn Panyella Pedersen Macromolecular Structure Group Dept. of Biochemistry and Biophysics University of California, San Francisco
