[Protein-analysis] Re: Analysis of proteins from milk

[Dr Engelbert Buxbaum]

Am 22.08.2007, 07:14 Uhr, schrieb <dogoyi from mail.uonbi.ac.ke>:

> One of my undergraduate students has initiated some work to analyse
> nutritional content of milk from some indigenous animals.  One of the
> experiments we intend to carry out is quantification and SDS-PAGE of milk
> proteins.  Can somebody out there advise on any available method that can
> remove the "milk colour" which would probably interfere with our assay or
> analysis?

Nutritional value depends on the amino acid composition more han on the  
number or nature of proteins, so hydrolysis followed by HPLC aa analysis  
would probably give more information than SDS-PAGE. Hydrolysis can be  
accomplished either by 6 N HCl (24 h, 110 deg C in evacuated and sealed  
ampules), by barium hydroxide (McGrath 1972) or NaOH (Landry & Delhaye  
1996). It is generally worthwhile to also submit samples with known  
amounts of a standard protein to analysis, to get a feel for the error  
associated with this procedure.

The "milk colour" is caused by fat droplets, so the standard  
Chloroform/Methanol (Wessel & Flügge 1984) precipitation should do fine  
for removing it.