'Fine' for me means comparable to SEC-MALLS measurements and reproducible.
I use the E calculated from the sequence using the protparam server at Expasy.

============================
David C. Briggs PhD
Father, Structural Biologist and Sceptic
============================
University of Manchester E-mail:
david.c.bri...@manchester.ac.uk
============================
http://manchester.academia.edu/DavidBriggs (v.sensible)
http://xtaldave.wordpress.com/ (sensible)
http://xtaldave.posterous.com/ (less sensible)
Twitter: @xtaldave
Skype: DocDCB
============================



On 16 June 2011 22:31, Edward A. Berry <ber...@upstate.edu> wrote:
> Arnon Lavie wrote:
> ~~~
>>
>> 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?
>>
> Bradford is an assay, Nanodrop is a spectrophotometer.
> Both the A280 and Bradford methods are strongly dependent on
> amino acid composition, so unless you correct A280 for that
> as mentioned by Filip, either one is semiquantitative.
> Occasionally you come across a protein with no tryptophan
> which will have a much lower extinction coefficient.
> Try making a 1 g/l solution of gelatin (collagen?)
> and see what its A280 is!  I noticed recently the
> "protparam" tool at http://ca.expasy.org/cgi-bin/protparam
> estimates the extinction coefficient given a sequence.
>
>
>
> David Briggs wrote:
> ~~~
>>
>> I wouldn't touch Bradford with a barge-pole. I've found it to be
>> wildly inaccurate for certain proteins I've handled, where as the
>> OD280 measurements have been fine.
>>
> One wonders what does "fine" mean, like same as with Biuret or
> Kjeldahl nitrogen, or solution made up by weight?
>
>
>

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