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Optical spectroscopy and nanosecond flash photolysis (Nd:YAG laser, 355 nm, pulse duration 5 ns, mean energy 5 mJ/pulse) were used to study the photochemistry of Fe(III)(C2O4)3(3-) complex in aqueous solutions. The main photochemical process was found to be intramolecular electron transfer from the ligand to Fe(III) ion with formation of a primary radical complex [(C2O4)2Fe(II)(C2O4(*))](3-). The yield of radical species (i.e., CO2(*-) and C2O4(*-)) was found to be less than 6% of Fe(III)(C2O4)3(3-) disappeared after flash. [(C2O4)2Fe(II)(C2O4(*))](3-) dissociates reversibly into oxalate ion and a secondary radical complex, [(C2O4)Fe(II)(C2O4(*))](-). The latter reacts with the initial complex and dissociates to Fe(II)(C2O4) and oxalate radical. In this framework, the absorption spectra and rate constants of the reactions of all intermediates were determined.

Transformed Gibbs free energy values of respiratory reactions are calculated to address the spontaneity, selectivity, control, and efficiency of oxidative phosphorylation. We present tangible explanations for ubiquinone’s role mitochondria, HCN > H2S order of cellular toxicity in aerobes and why oxygen inhibits anaerobes. Our data/arguments highlight the significance of proton deficiency in NADH/mitochondria and link the ‘oxygen → ROS (reactive oxygen species) → water’ metabolic pathway to the macroscopic physiologies of ATP-synthesis, trans-membrane potential, thermogenesis, and homeostasis. This ‘murburn perspective’ affords a probabilistically and thermodynamically viable precept for the origin and evolution of the ‘working logic’ of oxygen-centric life.

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Starting from basic molecular structure and redox properties of its components, we build a macroscopic cellular electrophysiological model. We first present a murburn purview that could explain ion-distribution in bulk-milieu/membrane-interface and support the origin of transmembrane potential (TMP) in cells. In particular, the discussion focuses on how cells achieve disparity in the distribution of monovalent and divalent cations within (K + > Na + > Mg 2+ > Ca 2+ ) and outside (Na + > K + > Ca 2+ > Mg 2+ ). We explore how TMP could vary for resting/graded/action potentials generation and project a model for impulse conduction in neurons. Outcomes based in murburn bioenergetic equilibriums leading to solubilization of ionpairs, membrane's permittivity, protein channels' fluxes, and proteins' innate ability to bind/adsorb ions selectively are projected as the integral rationale. We also provide experimental modalities to ratify the projections.

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Nanosecond laser flash photolysis, absorption and fluorescent spectroscopy were used to study the influence of pH on the photophysical and photochemical processes of 5-sulfosalicylic acid (SSA) in aqueous solutions. Information on the excited singlet state intramolecular proton transfer (ESIPT) of the SSA ions could be deduced from the dependence of the quantum yield and the spectral maximum of SSA fluorescence on the pH of the medium. The main photochemical active form of SSA at pH < 10 is the dianion (HSSA 2− ). Excitation of this species gives rise to the HSSA 2− triplet state, to the SSA •2− radical anion and to the hydrated electron. In a neutral medium, the main decay channels of these intermediates are T-T annihilation, recombination and capture by the HSSA 2− dianion, respectively. A decrease of pH leads to an increase of the second-order rate constants of disappearance of both HSSA 2− triplet state and SSA •2− radical anion due to their protonation.