Effect of Concentrated Urea Solution on the Precipitating Power of Antiovalbumin: Significance of Formation of Protein Complexes

Abstract

Studies on the effect of concentrated urea on the precipitating power of a variety of antibodies showed that complexing occurred upon removal of urea, since urea-treated prepns. often showed an increase in amt. of precipitable protein at opt. antigen-antibody concns. and the effect was markedly dependent upon the protein treatment with urea. Three rabbit anti-ovalbumins were studied, namely, whole antiserum, antibody partially purified with (NH4)2SO4 pptn. and antibody isolated from a specific ppt. by acid dissociation. All 3 came from a pool of fresh rabbit serum with an opt. proportion zone of 1:6,000 and 2 mg. of antibody per ml. of whole serum. Each was treated in 3 different protein cones. Solid urea was added to each to a final conc. of 8M, the pH was held to 8 and the soln. stayed at room temp. for 48 hrs. Urea was dialyzed against 1 NaCl and the protein conc. adjusted to a uniform value. Tests were made using 2-fold antigen dilutions, and the ppts. were analyzed for N. Undiluted whole serum gave no ppt. in any antigen dilution, but upon reduction to 1.36% protein its activity was 89% of that of untreated serum. At 0.58% protein the activity was about the same as that of the control. Partially purified antibody (5% soln.) gave 28% more ppt. than the control. Highly purified antibody showed no effect from the urea treatment.