Water assisted high proton conductance in a pure-inorganic framework vanadoborate

A new pure-inorganic framework vanadoborate H10[V12B18O54(OH)6]•20H2O (1) was hydrothermally synthesized and structurally characterized. Its inorganic framework was constructed by discrete [V12B18O54(OH)6]10- polyanion clusters decorated with H+ as counterions. For 1,...

Directional Proton Conductance in Bacteriorhodopsin Is Driven by 2 Concentration Gradient, Not Affinity Gradient

It is widely spread that microorganisms can harvest energy from sun light to establish electrochemical potential across cell membrane by pumping protons outward. Light driven proton pumping against a transmembrane gradient entails exquisite electronic and conformational reconfiguration at fs to ms time scales. However, transient molecular events along the photocycle of bacteriorhodopsin are difficult to comprehend from noisy electron density maps obtained from multiple experiments when the intermediate populations coexist and evolve as a function of 13 decades of time. Here I report an in-depth meta-analysis of the recent time-resolved datasets collected by several consortiums. This analysis deconvolutes the observed mixtures, thus substantially improves the quality of the electron density maps, and provides a clear visualization of the isolated intermediates from I to M. The primary photoproducts revealed here suggest a proton transfer uphill against 15 pH units is accomplished by the same physics that governs the tablecloth trick. While the Schiff base is displaced at the beginning of the photoisomerization within ~30 fs, the proton stays due to its inertia. This affinity-independent early deprotonation builds up a steep proton concentration gradient that drives the directional proton conductance toward the extracellular medium. This mechanism fundamentally deviates from the widely adopted assumption based on equilibrium processes driven by light-induced changes of proton affinities. The method of a numerical resolution of concurrent events from mixed observations is also generally applicable.

Directional proton conductance in bacteriorhodopsin is driven by concentration gradient, not affinity gradient

It is widely spread that microorganisms can harvest energy from sun light to establish electrochemical potential across cell membrane by pumping protons outward. Light driven proton pumping against a transmembrane gradient entails exquisite electronic and conformational reconfiguration at fs to ms time scales. However, transient molecular events along the photocycle of bacteriorhodopsin are difficult to comprehend from noisy electron density maps obtained from multiple experiments when the intermediate populations coexist and evolve as a function of 13 decades of time. Here I report an in-depth meta-analysis of the recent time-resolved datasets collected by several consortiums. This analysis deconvolutes the observed mixtures, thus substantially improves the quality of the electron density maps, and provides a clear visualization of the isolated intermediates from I to M. The primary photoproducts revealed here suggest a proton transfer uphill against 15 pH units is accomplished by the same physics that governs the tablecloth trick. While the Schiff base is displaced at the beginning of the photoisomerization within ~30 fs, the proton stays due to its inertia. This affinity-independent early deprotonation builds up a steep proton concentration gradient that drives the directional proton conductance toward the extracellular medium. This mechanism fundamentally deviates from the widely adopted assumption based on equilibrium processes driven by light-induced changes of proton affinities. The method of a numerical resolution of concurrent events from mixed observations is also generally applicable.

Directional proton conductance in bacteriorhodopsin is driven by concentration gradient, not affinity gradient

It is widely spread that microorganisms can harvest energy from sun light to establish electrochemical potential across cell membrane by pumping protons outward. Light driven proton pumping against a transmembrane gradient entails exquisite electronic and conformational reconfiguration at fs to ms time scales. However, transient molecular events along the photocycle of bacteriorhodopsin are difficult to comprehend from noisy electron density maps obtained from multiple experiments when the intermediate populations coexist and evolve as a function of 13 decades of time. Here I report an in-depth meta-analysis of the recent time-resolved datasets collected by several consortiums. This analysis deconvolutes the observed mixtures, thus substantially improves the quality of the electron density maps, and provides a clear visualization of the isolated intermediates from I to M. The primary photoproducts revealed here suggest a proton transfer uphill against 15 pH units is accomplished by the same physics that governs the tablecloth trick. While the Schiff base is displaced at the beginning of the photoisomerization within ~30 fs, the proton stays due to its inertia. This affinity-independent early deprotonation builds up a steep proton concentration gradient that drives the directional proton conductance toward the extracellular medium. This mechanism fundamentally deviates from the widely adopted assumption based on equilibrium processes driven by light-induced changes of proton affinities. The method of a numerical resolution of concurrent events from mixed observations is also generally applicable.

Directional proton conductance in bacteriorhodopsin is driven by concentration gradient, not affinity gradient

It is widely spread that microorganisms can harvest energy from sun light to establish electrochemical potential across cell membrane by pumping protons outward. Light driven proton pumping against a transmembrane gradient entails exquisite electronic and conformational reconfiguration at fs to ms time scales. However, transient molecular events along the photocycle of bacteriorhodopsin are difficult to comprehend from noisy electron density maps obtained from multiple experiments when the intermediate populations coexist and evolve as a function of 13 decades of time. Here I report an in-depth meta-analysis of the recent time-resolved datasets collected by several consortiums. This analysis deconvolutes the observed mixtures, thus substantially improves the quality of the electron density maps, and provides a clear visualization of the isolated intermediates from I to M. The primary photoproducts revealed here suggest a proton transfer uphill against 15 pH units is accomplished by the same physics that governs the tablecloth trick. While the Schiff base is displaced at the beginning of the photoisomerization within ~30 fs, the proton stays due to its inertia. This affinity-independent early deprotonation builds up a steep proton concentration gradient that drives the directional proton conductance toward the extracellular medium. This mechanism fundamentally deviates from the widely adopted assumption based on equilibrium processes driven by light-induced changes of proton affinities. The method of a numerical resolution of concurrent events from mixed observations is also generally applicable.

Stable covalent cross-linked polyfluoro sulfonated polyimide membranes with high proton conductance and vanadium resistance for application in vanadium redox flow battery

The performance of vanadium redox flow battery (VRFB) is largely determined by the membrane as a separator. To address the trade-off issue between proton conductance and vanadium resistance of sulfonated...

Structural models of mitochondrial uncoupling proteins obtained in DPC micelles are not physiologically relevant for their uncoupling activity

Uncoupling protein 1 (UCP1) is found in the inner mitochondrial membrane of brown adipocyte. In the presence of long-chain fatty acids (LCFA), UCP1 increases the proton conductance, which, in turn, increases fatty acid oxidation and energy release as heat. Several atomic models of UCP1 and UCP2 have been obtained by NMR in dodecylphosphocholine (DPC), a detergent known to inactivate UCP1. Based on NMR titration experiment on UCP1 with LCFA, it has been proposed that K56 and K269 are crucial for LCFA binding and UCP1 activation. Given the numerous controversies on the use of DPC for structure-function analyses of membrane proteins, we revisited those UCP1 mutants in a more physiological context by expressing them in the mitochondria of S. cerevisiae. Mitochondrial respiration, assayed on permeabilized spheroplasts, enables the determination of UCP1 activation and inhibition. The K56S, K269S and K56S/K269S mutants did not display any default in activation, which shows that the NMR experiments in DPC detergent are not relevant to understand UCP1 function.

Mechanical inhibition of isolated Vo from V/A-ATPase for proton conductance

V-ATPase is an energy converting enzyme, coupling ATP hydrolysis/synthesis in the hydrophilic V1 domain, with proton flow through the Vo membrane domain, via rotation of the central rotor complex relative to the surrounding stator apparatus. Upon dissociation from the V1 domain, the Vo domain of the eukaryotic V-ATPase can adopt a physiologically relevant auto-inhibited form in which proton conductance through the Vo domain is prevented, however the molecular mechanism of this inhibition is not fully understood. Using cryo-electron microscopy, we determined the structure of both the holo V/A-ATPase and isolated Vo at near-atomic resolution, respectively. These structures clarify how the isolated Vo domain adopts the auto-inhibited form and how the holo complex prevents formation of the inhibited Vo form.