Table 1. Comparison of Hyperfine Splittings (Azza) at 60 K for Spin-Labeled SBL1b with Variations in pH and Lipid (LOPC) and Predicted Water Exposurec.
| residue | Azz at pH 7 | Azz at pH 9 | Azz with LOPC | water exposure |
|---|---|---|---|---|
| I257R1 | 3.74 | 3.73 | 3.61 | 58 |
| T259R1 | 3.47 | 3.47 | 3.61 | 6 |
| K260R1 | 3.72 | 3.51 | 3.58 | 57 |
| S261R1 | 3.64 | 3.57 | 3.56 | 20 |
| L262R1 | 3.43 | 3.43 | 3.54 | 0 |
| S263R1 | 3.77 | 3.53 | 3.61 | 20 |
| Q264R1 | 3.75 | 3.55 | 3.64 | 94 |
| I265R1 | 3.74 | 3.56 | 3.60 | 68 |
| Q267R1 | 3.61 | 3.54 | 3.61 | 18 |
| F270R1 | 3.31 | 3.60 | 3.61 | 1 |
| F274R1 | NDd | 3.65 | 3.66 | 10 |
| L541R1 | NDd | 3.54 | 3.66 | 27 |
a
Values of Azz are given in millitesla.
b
Residues 257–274 are on helix 2, and residue 541 is on helix 11.
c
Values of water exposure are given in square angstroms and were determined using the DSSP software package39 with the crystal structure of PDB entry 1YGE.
d
Measurements of F274R1 and L541R1 at pH 7 were not determined.