How does aggregation influence absorbtion at 280nm? - (Feb/15/2010 )

Hi!

If a protein aggregates, does it absorb the same way at 280 nm or does it drop/increase in absorption?
Can one say anything generally here... ?

When we purify a new protein always make a meassurement at 230 nm due to (theoretically) the ratio 230/280 gives you the agreggation %. Nearly always, some % of your 280 absorbance is light scattering due to the presence of aggregates, it is not strange to obtain a 10-25% of aggregates in a purification procedure. Sometimes, if you change the buffer or make use of several specific aditives (detergents, DTT, caothopic agents) that improve the solubility, the % of aggregates diminish and your absorbance at 280 nm goes down also.