biorad vs

[Tom Anderson]

On Wed, 15 Jan 2003, Dr Engelbert Buxbaum wrote:

> If true concentrations are required, Kjedal ashing may be used (that
> requires a lot of material), alternatively it is possible to calculate
> the absorbance of a protein at 280 nm from its amino acid composition,
> if the latter is known.

also, you can measure the absorbance at 214 nm, which is due to the
peptide bonds and is thus independent of composition. however, i think you
need rather specialised instruments and methods to do it, involving a
far-UV spectrophotometer, degassed buffers and whatnot. it's routinely
used to monitor the output from HPLC systems, but not for much else.

tom