Acidic citrate stabilizes blood samples for assay of total homocysteine.

min were as follows: At 70 MPa (10 000 lb./in.), no pressure effect was evident; ;10% of maximal binding was observed at 140 MPa, 20% at 210 MPa, 50% at 280 MPa, and 80% at 420 MPa. Preincubation of the anti-p24 antibody alone (without the p24 antigen) at 420 MPa for 10 min did not result in any discernible decrease in absorbance, indicating that pressures as great as 420 MPa did not affect the ability of the antibody to subsequently bind to the antigen. Applying 420 MPa for different times enhanced the binding of antigen to antibody rapidly, with 50% binding in 5 min. Maximum binding was reached in 10 min, as indicated by binding of 79% in 10 min, 69% in 25 min, and 82% in 50 min (Fig. 1). As these data show, the binding achieved in overnight incubations at atmospheric pressure was not attained at the pressures used in this study. Higher pressures than those studied here or longer incubations at lower pressures may allow greater binding to occur. From this preliminary study we conclude that high pressure can be used to accelerate the binding of an antibody to an antigen. This phenomenon could find practical application in shortening assay times and in greatly reducing the amount of reagents required in immunoassays and other binding assays, such as those used in clinical and high-throughput screening assays.