# Thermal and Solvent-Isotope Effects on the Flagellar Rotary Motor near Zero Load

 Title: Thermal and Solvent-Isotope Effects on the Flagellar Rotary Motor near Zero Load Author: Berg, Howard Curtis; Yuan, Junhua Note: Order does not necessarily reflect citation order of authors. Citation: Yuan, Junhua and Howard C. Berg. 2010. Thermal and solvent-isotope effects on the flagellar rotary motor near zero load. Biophysical Journal 98(10): 2121-2126. Full Text & Related Files: Biophys.J.2.pdf (138.4Kb; PDF) Abstract: In Escherichia coli, the behavior of the ﬂagellar rotary motor near zero load can be studied by scattering light from nanogold spheres attached to proximal hooks of cells lacking ﬂagellar ﬁlaments. We used this method to monitor changes in speed when cells were subjected to changes in temperature or shifted from a medium made with $$H{_2}O$$ to one made with $$D_{2}O$$. In $$H{_2}O$$, the speed increased with temperature in a near-exponential manner, with an activation enthalpy of $$52 \pm 4$$ kJ/mol ($$12.0 \pm 1.0$$ kcal/mol). In $$D_{2}O$$, the speed increased in a similar manner, with an activation enthalpy of $$50 \pm 4$$ kJ/mol. The speed in $$H{_2}O$$ was higher than that in $$D_{2}O$$ by a factor of $$1.53 \pm 0.14$$. We performed comparison studies of variations in temperature and solvent isotope, using motors operating at high loads. The variations were small, consistent with previous observations. The implications of these results for proton translocation are discussed. Published Version: doi: 10.1016/j.bpj.2010.01.061 Terms of Use: This article is made available under the terms and conditions applicable to Other Posted Material, as set forth at http://nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of-use#LAA Citable link to this page: http://nrs.harvard.edu/urn-3:HUL.InstRepos:9032268 Downloads of this work: