Table 1.

Enthalpies, ΔH, of selected proteins

ProteinT range °CQ10ΔH kcal mol−1Reference(s)
TRPA126–16≈10−4010
TRPM827–1824−56 (−112)11
TRPC525–40≈10−4012
25–15≈2−14
TRPV425–4510, 1944, 5713, 14
TRPV324–34336415
TRPV141–504075, 90–1009, 16
TRPV250–60>100>10017, 18
Comparators
 Hemoglobin T → R transition−1019
 Shaker K+ channel C-type inactivation−1620
 AdiC arginine agmatine antiporter substrate occlusion521
 Hexokinase closing222
  • Values of Q10, determined in the indicated temperature range to either heat (red) or cold (blue) for various TRP channels. Corresponding ΔH are calculated from Eq. 6B; numbers in parentheses for TRPM8 from Brauchi et al.'s (11) fit of the van't Hoff plot. We do not list Q10s measured over more moderate deviations from room temperature. Q10s often increased on repeated trials, indicating that proteins become modified by internal ligand changes (e.g., Ca2+), equivalent to failure of the protein to return to its initial conformation between trials. Bottom four rows: For comparison, ΔH values are shown for several systems of carefully studied protein conformational rearrangements near 20 °C. We thank Feng Qing for providing data before publication (18).