Table 2.
Determination of hapten density on BSA-MPAD conjugates using MALDI-TOF mass spectrometric methodThe number of lysine groups on protein being utilized for conjugates before and after conjugation are given in brackets for (a) 2, 4-D-protein conjugates and (b) atrazine–protein conjugates
| 2, 4-D-protein conjugates | ||||
| Sample | BSA-2,4D conjugate | Observed massa (kD) | Change in mass (∆M) in dalton | Approximate no. of 2,4-D molecules/BSA moleculeb |
| D0 | BSA | 67,221.0 | 0 | |
| D1 | 1:5 | 67,962.6 | 3.35 (3) | |
| D2 | 1:10 | 69,171.5 | 8.82 (9) | |
| D3 | 1:20 | 70,228.0 | 13.60 (14) | |
| D4 | 1:40 | 70,926.8 | 16.76 (17) | |
| D5 | 1:100 | Did not fly | – | – |
| Atrazine–protein conjugates | ||||
| Sample | BSA-MPAD conjugate | Observed massa | Change in mass (∆M) in dalton | Approximate no. of 2,4-D molecules/BSA moleculeb |
| M0 | BSA only | 67,221.0 | 0 | 0 |
| M1 | 1:5 | 67,744.9 | 523.9 | 1.84 (2) |
| M2 | 1:10 | 68,293.8 | 1,072.8 | 3.76 (4) |
| M3 | 1:20 | 70,288.7 | 3,067.7 | 10.75 (11) |
| M4 | 1:40 | 71,720.8 | 4,499.8 | 15.77 (16) |
| M5 | 1:100 | Did not fly | – | – |
aMass calculated from the average of three scans. Each scan was averaged from 50 profiles
bNumber of haptens molecules per molecule of BSA were calculated by determining the difference in molecular weight (∆M)/molecular weight of hapten