Dr Engelbert Buxbaum wrote:
> Gerd Hoffmann wrote:
>>>>we want to try to determine protein concentration in a solution
>>containing fragments of "membrane-protein-crystalls". We
>>want to try this with a bradford assay.
>>> Any lipophilic or amphiphilic compound will interfere with Bradford,
> including lipids and detergents.
>> To remove the large fragments you may have to do protein precipitation
> either with chloroform/methanol (Wessel & Fluegge) or with TCA using
> desoxycholate as carrier (Bensadoun & Weinstein). There are a number of
> alternative methods (e.g. phenol/ether, calcium phosphate or certain
> dyes) which have not found widespread application. The purified protein
> is then dissolved in alkaline solution and determined either by the
> Lowry et al. procedure or with BCA (which is probably what the previous
> poster was referring to as "Pierce assay").
>> Alternatively, you can dot blot your sample onto a PVDF membrane, wash
> thoroughly and then stain the bound protein with Coomassie. The amount
> of stain bound to a spot can then be determined either with a flat bed
> scanner and quantitation with NIH-image, or by extraction of the dye
> with alkaly and photometric determination. In particular the scanner
> route is very quick and reasonably precise.
Thank you for your answer! In the moment we want to try the BCA method.
As a "fallback" we try the other experiments.