Table 3. Summary of the Peak Assignments for the Side Chain Vibrational Modes within the Side Chain Band (1600–1500 cm–1) As Determined by the Synchronous and Asynchronous Plots.
|
Hscen1a peak position (cm–1) |
Hscen2 peak position (cm–1) |
Hscen3 peak position
(cm–1) |
||||||
|---|---|---|---|---|---|---|---|---|
| peak assignmentb | stretching vibrational mode | 5–35 °Cc | 40–95 °Cd | 5–35 °Cc | 40–95 °Cd | 5–35 °Cc | 40–60 °Cc | 60–90 °Cd |
| arginine | guanidinium νa(N–D) | 1608.7 | 1610.0 | 1603.4 | 1602.8 | 1604.2 | 1608.8 | 1613.3 |
| arginine | guanidinium νs(N–D) | 1578.7 | 1586.2 | 1591.8 | 1597.5 | 1581.3 | 1585.8 | 1581.3 |
| aspartate | νs(COO–) | 1561.4 | 1566.0 | 1572.5 | 1575.0 | 1560.5 | 1562.8 | 1564.1 |
| glutamate | νs(COO–) | 1539.0 | 1548.0 | 1546.8 | 1552.5 | 1546.9 | 1551.3 | 1555.6 |
a
The underlined peak position represents the greatest intensity change for the auto peaks within the synchronous plot.
b
Hscen1 and Hscen2 contain a single Tyr residue, and Hscen3 contains two Tyr residues, observed at 1517 cm–1, which will not be discussed in this work.
c
Aspartate and glutamate peak positions are characteristic of the bound state, presumably in the lower-affinity CaBS.41
d
Aspartate and glutamate peak positions are characteristic of the unbound (apo) state within the high-affinity CaBS. The loss of calcium binding occurs because of the high-temperature perturbation as a prerequisite step to thermal unfolding.