Warm up the spectrophotometer by leaving it on for at least 15 minutes before you start using it.
Prepare small samples that have known concentrations of glycoproteins or "known standards." Start your concentrations as high as 100 micrograms of glycoprotein per milliliter (ml) of distilled water, and for each subsequent standard, dilute your concentration by half; i.e., 50 micrograms/ml, 25 micrograms/ml.
Add Bradford reagent dye and Brilliant Blue G from your Bradford assay kit to each known standard. Allow it to sit and react for five minutes.
Prepare the sample for which you want to quantify your glycoprotein concentration. The sample should contain between five and 100 micrograms of glycoprotein per ml. Add Bradford reagent dye and Brilliant Blue G.
Place the assay plate containing standards and unknowns in a spectrophotometer. For the standards, obtain a calibration curve, graphing absorbance vs. known concentration. This curve, for the range of concentrations used as previously mentioned, should be linear. Calculate a linear equation to describe your curve.
Plug your absorbance values for your known sample into the linear equation you obtained in the previous step. Calculate the glycoprotein concentration for your sample.
Add Bradford dye and Brilliant Blue G to the unknown sample in the assay plate.
Add Bradford dye and Brilliant Blue G to another well of the assay plate, without adding any known or unknown solutions.
Read the assay plate in the spectrophotometer, at 465 and 595 nm. The well containing only Bradford dye and Brilliant Blue G should have peak absorbance -- the wavelength where the absorbance is at its maximum; this will be displayed by your spectrophotometer software automatically -- of 465.
For the unknown sample, if it contains proteins, the absorbance peak maximum will occur at 595 nm. If, on the other hand, your sample consists primarily of carbohydrates, not proteins, like the well containing only Bradford dye and Brilliant Blue G, its peak absorbance will occur at 465 nm.