Types of 96-well plates used for BCA protein quantification - (Jan/18/2012 )

Is a round-bottomed plate fine for measuring BCA using a plate reader?

How does the light (emission or absoption?) work in these machines?

Also, is a non-transparent one ok? or does it have to allow light to pass through the plate?

You need a transparent flat bottomed plate to read the concentration effectively by absorbance (BCA is an absorbance assay - you are measuring at only one wavelength, no excitation and emission). Round bottomed plates scattter the light too much to be effective for the reading. Non-transparent plates don't work with absorbance for obvious reasons!