Table 1.
Validated sites and nature of modification in acro-apoE3 following trypsin and elastase digestion and LC-MS/MS analysis *.
| Trypsin | Elastase | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Site | Mass Increase | † Best ASCORE | Spectral Count Acro-ApoE3 | Nature of Lys Modification | Site | Mass Increase | † Best Ascore | Spectral Count Acro-ApoE3 | Nature of Modification |
| K1 | - | - | - | - | K1 | 76 | 1000 | 3 | MP-Lys |
| K69 | 76 | 161.94 | 9 | MP-Lys § | K69 | 76 | 1000 | 12 | MP-Lys |
| K69 | 56 | 100.09 | 3 | Propanal adduct | K69 | 56 | 100.09 | 2 | Propanal adduct |
| K69 | 38 | 1000 | 1 | Aldimine | K69 | - | - | - | - |
| K72 | 76 | 119.87 | 9 | MP-Lys | K72 | 76 | 153.17 | 15 | MP-Lys |
| K72 | 38 | 1000 | 1 | Aldimine | K72 | 38 | 1000 | 2 | Aldimine |
| K75 | 76 | 1000 | 6 | MP-Lys | K75 | 76 | 1000 | 8 | MP-Lys |
| K75 | 94 | 1000 | 1 | FDP-Lys †† | K75 | 94 | 1000 | 1 | FDP-Lys |
| K75 | 56 | 120.17 | 2 | Propanal adduct | K75 | - | - | - | - |
| K75 | 38 | 1000 | 1 | Aldimine | K75 | - | - | - | - |
| K95 | 76 | 1000 | 5 | MP-Lys | K95 | 76 | 1000 | 4 | MP-Lys |
| K95 | 94 | 1000 | 1 | FDP-Lys | K95 | 94 | 1000 | 1 | FDP-Lys |
| K143 | - | - | - | - | - | - | - | - | - |
| K146 | - | - | - | - | - | - | - | - | - |
| K157 | 76 | 1000 | 6 | MP-Lys | K157 | 76 | 1000 | 9 | MP-Lys |
| K233 | 76 | 1000 | 9 | MP-Lys | K233 | 76 | 1000 | 11 | MP-Lys |
| K233 | 56 | 1000 | 4 | Propanal adduct | K233 | 56 | 1000 | 2 | Propanal adduct |
| K233 | 38 | 1000 | 1 | Aldimine | K233 | 38 | 1000 | 1 | Aldimine |
| K242 | 76 | 1000 | 4 | MP-Lys | K242 | 76 | 1000 | 4 | MP-Lys |
| K242 | 94 | 1000 | 2 | FDP-Lys | K242 | 94 | 1000 | 2 | FDP-Lys |
| K262 | 76 | 1000 | 6 | MP-Lys | K262 | 76 | 1000 | 8 | MP-Lys |
| K282 | 76 | 1000 | 1 | MP-Lys | K282 | 76 | 1000 | 3 | MP-Lys |
* Shown are those sites identified only in acro-apoE3 (i.e., spectral count = 0 for corresponding site in unmodified apoE3) or for which the spectral score was higher in acro-apoE3 than that for unmodified apoE3. † Ascore is a measure of the probability of correct localization of acrolein-modified site determined as defined under Supplemental Information. The localization probability is 1 for all the validated sites. § MP-Lys: Nε-(3-methylpyridinium)-lysine; †† FDP-Lys: Nε-(3-formyl-3,4-dehydropiperidino)lysine.