Table 5. LC-MSE Data for Amino Acid Residue Variations between Heavy Chains A and B.
| variable site(s)a | peptide | RT (min) | sequence | theoretical mass (Da)b | measured mass (Da) | mass error (ppm) | intensity (counts) | |
|---|---|---|---|---|---|---|---|---|
| 354 |
HCA:T33–35c |
44.1 |
GQPREPQVYVYPPSRDELTK |
|
2358.1968 |
2358.1931 |
-1.6 |
116764 |
| HCB:T33–35c |
47.4 |
GQPREPQVYVLPPSRDELTK |
|
2308.2175 |
2308.2158 |
-0.7 |
119682 |
|
| 369 |
HCA:T36 |
48.0 |
NQVSLTCLVK |
|
1160.6223 |
1160.6239 |
1.4 |
226906 |
| HCB:T36 |
58.6 |
NQVSLLCLVK |
|
1172.6588 |
1172.6610 |
1.9 |
244944 |
|
| 395, 397, 408, 410 | HCA:T37 (1)d |
55.9 |
GFYPSDIAVEWESNGQPENNYK |
|
2543.1240 |
2543.1230 |
-0.4 |
175028 |
| HCA:T38 (2)d |
54.8 |
TTPPVLDSDGSFALVSK |
|
1732.8883 |
1732.8901 |
1.0 |
264347 |
|
| HCB:T37d | 81.4 | GFYPSDIAVEWESNGQPENNYLTWPPVLDSDGSFFLYSK | 4468.0488 | 4468.0439 | -1.1 | 172680 |
a. Numbering is based on the trastuzumab sequence. b. Mass corresponds to carbamidomethylated cysteines. c. A hyphen in the peptide number indicates miscleavage. d. The lysine at position 395 of HCa is a trypsin cleavage site, leading to the two tryptic peptides T37 and T38. Position 395 in HCb is a leucine, which is not a trypsin cleavage site. Therefore, the same amino acid range in HCb only leads to one tryptic peptide T37.