Table 2.
Intrinsic size parameters (ISP) for individual components for doubly-protonated peptide ions.
| individual component | ISPa | individual component | ISPa |
|---|---|---|---|
| Gly | 0.93 (0.02) | Asp | 0.93 (0.02) |
| Pro | 1.00 (0.02) | Glu | 0.93 (0.02) |
| Ala | 0.96 (0.01) | Asn | 0.91 (0.02) |
| Val | 1.02 (0.02) | Gln | 0.94 (0.03) |
| Ile | 1.07 (0.02) | Ser | 0.95 (0.02) |
| Leu | 1.13 (0.01) | Thr | 0.93 (0.02) |
| Met | 1.08 (0.03) | Cys | 0.96 (0.03) |
| His | 1.11 (0.03) | Lys | 0.96 (0.02) |
| Phe | 1.04 (0.02) | Arg | 1.02 (0.03) |
| Tyr | 0.99 (0.03) | Amb | 0.92 (0.04) |
| Trp | 0.95 (0.04) | Palc | 1.26 (0.04) |
Intrinsic size parameters (ISP) are calculated from 406 [Pep+2H]2+ ions, combining the measurements provided here with a database by Dilger, et al.15 The [Pep+2H]2+ subset was limited to pentapeptides or larger with sequences that terminate in Lys or Arg. Reduced cross sections were generated by division of the experimental cross section with a second-order polynomial of Ω = −1.53E-5x2 + 0.1834x + 73.7590, where x is the molecular mass. The uncertainty is listed in parenthesis and represents one standard deviation about the mean. Please see text for details and references on the derivation of the ISP values and the errors.
“Am” represents the carboxyamidomethyl group.
“Pal” represents the palmitoyl group.