In the first measurement of enzymatic proton transfer at liquid helium temperatures, we examine protonation of the peroxo-ferriheme state of heme oxygenase (HO) produced by in situ radiolytic cryoreduction of oxy-HO in H2O and D2O solvents at ca. 4 K and above, and compare these findings with analogous measurements for oxy-P450cam and for oxy-Mb. Proton transfer in HO occurs at helium temperatu...

The reaction center from Rhodobacter sphaeroides uses light energy for the reduction and protonation of a quinone molecule, Q(B). This process involves the transfer of two protons from the aqueous solution to the protein-bound Q(B) molecule. The second proton, H(+)(2), is supplied to Q(B) by Glu-L212, an internal residue protonated in response to formation of Q(A)(-) and Q(B)(-). In this work, ...

Proton transfer in the nanoscopic water channels of polyelectrolyte fuel cell membranes was studied using a photoacid, 8-hydroxypyrene-1,3,6-trisulfonic acid sodium salt (HPTS), in the channels. The local environment of the probe was determined using 8-methoxypyrene-1,3,6-trisulfonic acid sodium salt (MPTS), which is not a photoacid. Three fully hydrated membranes, Nafion (DuPont) and two 3M me...

In protein environments, proton transfer reactions occur along polar or charged residues and isolated water molecules. These species consist of H-bond networks that serve as proton transfer pathways; therefore, thorough understanding of H-bond energetics is essential when investigating proton transfer reactions in protein environments. When the pKa values (or proton affinity) of the H-bond dono...

CytcO (cytochrome c oxidase) is a membrane-bound multisubunit protein which catalyses the reduction of O(2) to H(2)O. The reaction is arranged topographically so that the electrons and protons are taken from opposite sides of the membrane and, in addition, it is also linked to proton pumping across the membrane. Thus the CytcO moves an equivalent of two positive charges across the membrane per ...

Using the freon mixture CDF(3)/CDClF(2) as solvent we have been able to measure the (1)H and (15)N NMR spectra of the doubly (15)N labeled 2,2'-bipyridinium cation (BpyH(+)) at temperatures down to 115 K. The obtained NMR parameters strongly depend on the type of counteranions indicating the formation of ion pairs. In the case of the bulky poorly coordinating tetrakis[3,5-bis(trifluoromethyl)ph...

Molecular dynamics simulations are combined with quantum chemistry calculations of instantaneous proton-transfer energy profiles to investigate proton-transfer events in the transient pathway of cytochrome P450eryF (6-deoxyerythronolide B hydroxylase; CYP107A1), from the oxyferrous species to the catalytically active ferryl oxygen species (compound I). This reaction is one of the most fundament...

The reactions between 1,3-dialkynes and ammonia derivatives (such as hydrazine and hydroxylamine) for the formation of five-membered N-heterocycles (i.e. 3,5-disubstituted pyrazole and 3,5-disubstituted isoxazole) have been investigated using the density functional theory (DFT) method. The calculated results indicate that the favorable mechanism of this kind of reaction generally contains four ...

Proton transport is critical for many technologies and a variety of biochemical biophysical processes. transfer between molecules (via structural diffusion) considered to be an efficient mechanism in highly proton conducting materials. Yet, the what controls energy barriers this process remain poorly understood. It was shown that mixing phosphoric acid (PA) with lidocaine leads increase conduct...