Enthalpy and entropy changes of the flagellar motor

Range Table - link
Organism Bacteria Escherichia coli
Reference Turner L, Caplan SR, Berg HC. Temperature-induced switching of the bacterial flagellar motor. Biophys J. 1996 Oct71(4):2227-33. p.2231 table 1PubMed ID8889199
Method "[Researchers] used a strain of Escherichia coli (HCB437) that lacks chemotaxis signaling proteins, including the response regulator CheY, but which forms intact motor-switch complexes. At room temperature, tethered cells of this strain spin exclusively CCW [counter clockwise]...[researchers] calculated the activation energies (Figs. 5 A and B), enthalpies, and entropies (Figs. 6 A and B) for the forward and reverse transitions for each cell from transition state theory ... The standard free energy change was calculated from the equilibrium constant at each temperature (Fig. 5 C), and the standard enthalpy and entropy changes were calculated from the standard free energy change as a function of temperature (Fig. 6 C)."
Comments "The mean standard enthalpy and entropy changes for the forward transition are, respectively, about -400 kJ/mol and -1.5 kJ/K mol (see Table 1)...Even though the values vary from cell to cell, the overall trend is the same (Table 1). The standard enthalpy and entropy changes and the forward activation enthalpies and entropies are all negative the reverse activation enthalpies and entropies are all positive."
Entered by Uri M
ID 109868