The F0 complex of the ATP synthase of Escherichia coli contains a proton pathway with large proton polarizability caused by collective proton fluctuation

Abstract

The F0 complex of the Escherichia coli ATP synthase embedded into cardiolipin liposomes was studied by FT-IR spectroscopy. For comparison, respective studies were performed with dried F0 liposomes and with F0 liposomes treated with N,N'-dicyclohexyl-carbodiimide (DCCD), which binds to Asp-61 of subunit c. Furthermore, the effect of H2O-->D2O exchange on the infrared spectrum was investigated. With F0 liposomes an infrared continuum is observed beginning at about 3000 cm-1 and extending toward smaller wavenumbers. In the DCCD-treated sample, this continuum is no longer observed. It vanishes also with drying of the liposomes. After H2O-->D2O exchange, this infrared continuum begins at about 2350 cm-1 and is less intense. All of these results demonstrate that a proton pathway in native F0 is present, in which the protons are shifted in a hydrogen-bonded chain with large proton polarizability due to collective proton tunneling. With the D2O-hydrated system, deuteron polarizability due to collective deuteron motion is observed, but the polarizability due to collective deuteron motion is smaller. Such pathways are very efficient, because they conduct protons or deuterons within picoseconds. These pathways lose their polarizability if the F0 complex is blocked by DCCD or if the liposomes are dried. On the basis of our results on the proton polarizability of hydrogen bonds and hydrogen-bonded systems and on the basis of structural data from the literature, the nature of the proton pathway of the F0 complex of E. coli is discussed.

Evidence for a Partially Folded Intermediate in α-Synuclein Fibril Formation

“…Effect of pH on ␣-Synuclein Fibrillation-The histological dye thioflavin T is widely used for the detection of amyloid fibrils (29,44,45). In the presence of fibrils, ThT gives rise to a new excitation maximum at 450 nm and enhanced emission at 482 nm, whereas unbound ThT is essentially non-fluorescent at these wavelengths.…”

Coherent Tunnel Repolarization of a Hydrogen Bonded Chain

“…Since the tunnel splitting ∆ for the model given by the anisotropy energy, equation (15), was calculated in [28], there is no need in repeating these calculations in the present paper. In this part, following [28], we dwell upon the key points of these calculations.…”

“…Thus, our problem is reduced to the model of a one-domain ferromagnetic particle with anisotropy energy given by equation (12) or equation (15). The problem of the macroscopic quantum coherence which corresponds to the tunnel switching of the particle magnetic momentum between the two equilibrium directions with the same energy was considered in detail (see, e.g., [25,26,28]), and we make use of these results to estimate the tunnelling frequency for our case.…”

“…The short hydrogen-bonded chains are one of the main proton channel elements of proton-conducting biomembranes [10,11]. It is well known [10,[12][13][14][15][16][17], that this chain has a great polarisability which fluctuates between two opposite directions. Many optical and kinetic properties of H-bonded chains are defined by different mechanisms of the polarization oscillations.…”

Molecular Heteroconjugation Equilibria in (n-Butylamine + Acetic Acid) Systems in Binary (Dimethyl Sulfoxide + 1,4-Dioxane) Solvent Mixtures

“…The acid-base interaction together with ongoing processes of hydrogenbond formation are crucial for the formation of structures of biomolecules and biochemical reactions, as reflected by the rapidly increasing number of reports on the subject [1,4]. In non-aqueous media, relatively, wellexplored are equilibria of acid-base dissociation of both molecular (1) and cationic acids (2), as well as those of anionic homoconjugation (3), and more recently, of cationic homoconjugation (4):…”