Dear fellow crystallographers - a question about spectrophotometers for protein concentration determination.

We are so last millennium - using Bradford reagent/ 1 ml cuvette for protein conc. determination.

We have been considering buying a Nanodrop machine (small volume, no dilution needed, fast, easy). However, while testing our samples using a colleague's machine, we have gotten readings up to 100% different to our Bradford assay (all fully purified proteins). For example, Bradford says 6 mg/ml, Nanodrop 3 mg/ml. So while it is fun/easy to use the Nanodrop, I am not sure how reliable are the measurements (your thoughts?).

So QUESTION 1: What are people's experience regarding the correlation between Nanodrop and Bradford?

While researching the Nanodrop machine, I heard about the Implen NanoPhotmeter Pearl. So Question 2: Is the Pearl better/worse/same as the Nanodrop for our purpose?

Thank you for helping us to advance to the next millennium, even if it is nearly a dozen years late.


Arnon Lavie, Professor
Dept. of Biochemistry and Molecular Genetics
University of Illinois at Chicago
900 S. Ashland Ave.
Molecular Biology Research Building, Room 1108 (M/C 669)
Chicago, IL 60607
                             Tel:        (312) 355-5029
                             Fax:        (312) 355-4535

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