Infrared-ultraviolet double resonance spectroscopy has been applied to study the infrared spectra of the supersonically cooled gas phase complexes of formic acid, acetic acid, propionic acid, formamide, and water with 9-hydroxy-9-fluorenecarboxylic acid (9HFCA), an analog of glycolic acid. In these complexes each binding partner to 9HFCA can function as both proton donor and acceptor. Relative ...

The title compound, 2C(3)H(7)N(6) (+)·C(6)H(2)N(2)O(4) (2-)·4H(2)O or (tataH)(2)(pzdc)·4H(2)O, was synthesised by a reaction between pyrazine-2,3-dicarboxylic acid (H(2)pzdc) as a proton donor and 2,4,6-triamino-1,3,5-triazin (tata) as a proton acceptor. In the crystal structure, an extensive series of O-H⋯O, O-H⋯N, N-H⋯O and N-H⋯N hydrogen bonds generates a three-dimensional framework with the...

Despite thermodynamic, bioenergetic and phylogenetic failings, the 81-year-old concept of primordial soup remains central to mainstream thinking on the origin of life. But soup is homogeneous in pH and redox potential, and so has no capacity for energy coupling by chemiosmosis. Thermodynamic constraints make chemiosmosis strictly necessary for carbon and energy metabolism in all free-living che...

We study a model of a light-induced proton pump in artificial reaction centers. The model contains a molecular triad with four electron states (i.e., one donor state, two photosensitive group states, and one acceptor state) as well as a molecular shuttle having one electron and one proton-binding sites. The shuttle diffuses between the sides of the membrane and translocates protons energeticall...

The bacterial reaction center (RC) converts light into chemical energy through the reduction of an internal quinone molecule Q(B) to Q(B)H(2). In the native RC, proton transfer is coupled to electron transfer and is not rate-controlling. Consequently, proton transfer is not directly observable, and its rate was unknown. In this work, we present a method for making proton transfer rate-controlli...

Fe-containing superoxide dismutase (FeSOD) and MnSOD are widely assumed to employ the same catalytic mechanism. However this has not been completely tested. In 1985, Bull and Fee showed that FeSOD took up a proton upon reduction [J. Am. Chem. Soc. 107 (1985) 3295]. We now demonstrate that MnSOD incorporates the same crucial coupling between electron transfer and proton transfer. The redox-coupl...

For blue-shifted hydrogen-bonded systems, the hydrogen stretching frequency increases rather than decreases on complexation. In computations at various levels of theory, the blue-shift in the archetypical system, F(3)C-H.FH, is reproduced at the Hartree-Fock level, indicating that electron correlation is not the primary cause. Calculations also demonstrate that a blue-shift does not require eit...

The theoretical study in this paper is based on the experimental result that the rate of photoinduced electron transfer is ∼102 times slower through a donor-(amidinium-carboxylate)-acceptor salt bridge than through the corresponding switched interface donor-(carboxylate-amidinium)-acceptor complex (Kirby, J. P.; Roberts, J. A.; Nocera, D. G. J. Am. Chem. Soc. 1997, 119, 9230). This experimental...

The optimized geometries, harmonic vibrational frequencies, and energies of the structures of monohydrated alloxan were computed at the DFT/ωB97X-D and B3LYP/6-311++G** level of theory. Results confirm that the monohydrate exists as a dipolar alloxan-water complex which represents a global minimum on the potential energy surface (PES). Trajectory dynamics simulations show that attempt to reorie...

(17)O NMR spectroscopy combined with first-principles calculations was employed to understand the local structure and dynamics of the phosphate ions and protons in the paraelectric phase of the proton conductor CsH2PO4. For the room-temperature structure, the results confirm that one proton (H1) is localized in an asymmetric H-bond (between O1 donor and O2 acceptor oxygen atoms), whereas the H2...