Determination of Glycoproteins To each 1.5-mLfraction was added 1mL of a solution of ~ h o s ~ h o tungstic acid (Sigma,U.S.A.) at 5%(wlv) in 2 N HCI. ~heiurbidity developed was measured as transmittance at X = 470 nm within the 30 min after mixing. At this wavelength neither the glycoproteinnor phosphotnngstic acid present absorbance individually.
Results and Discussion
The fipure.shows the elution profile obtained. The first peak helings to the unbound glicoproteins and represents approximately 20%of the amount recovered. The second is obtained 3 m i after applying the sugar and represents more
than 56% of total. The last, indicative of strongly hound glycoproteins, represents nearly 23%. However, this precipitation is a destructive process, and to avoid losing all the sample, which would make further studies impossible, the routine visualization of glycoproteins in eluates can be performed with a Takatsy microtiter (Cooke, England) whose cups contain one or two drops of phosphotungstic acid solution. T o the first cup is added two drops of the first 1.5-mL fraction, to the second, two drops of the second fraction, and so on. After 30 min the possible precipitate is observed by illumination of the bottom of the cups. In this way, only a few microliters are lost in each fraction.
Volume 65
Number 6
June 1988
557
