Although it is generally true that thermodynamics do not influence kinetics, this NOT the case for electron transfer reactions in solution. Marcus Theory explains why so, using straightforward physical chemical principles such as transition state theory, Arrhenius' Law, and Franck-Condon Principle. Here background applications of are presented, with special emphasis given to biological redox reactions. Interesting conclusions arise from theory also discussed. These include nonlinear...

Since at least the 1960s, organic chemistry textbooks have featured pKa tables for acids that include values H2O and H3O+ (15.74 −1.74, respectively) are thermodynamically chemically indefensible. Here we trace this error back to Brønsted's early contributions in 1920s Brønsted–Lowry Theory of bases. Organic chemists generally defend use these by citing measurements equilibrium constant water + methoxide acid–base reaction suggested methanol (pKa = 15.54) is a stronger acid than water; from...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Real Reason Why Oil and Water Don't MixTodd P. Silverstein View Author Information Willamette University, Chemistry Department, 900 State Street, Salem, OR 97301-3922Cite this: J. Chem. Educ. 1998, 75, 1, 116Publication Date (Web):January 1998Publication History Received3 August 2009Published online1 January 1998Published inissue 1 1998https://pubs.acs.org/doi/10.1021/ed075p116https://doi.org/10.1021/ed075p116research-articleACS...

Abstract In the early 1900s, Brønsted used two different pairs of p K a values for water and aqueous proton: He denoted 14.00 0.00 (respectively) as “conventional” values, 15.74 −1.74 “rational” values. Although conventional have been supported by both experiment theory, rational employed in vast majority studies involving plots up to present day. Here we meta‐analysis 67 published from 1924 2010, revealing that ’ more frequently appear statistical outliers (a greater than 80 % rejection...

At least eleven thylakoid proteins become phosphorylated under reducing conditions, and redox titration has identified a common midpoint potential of Em = +38 +/- 4 mV, n 0.95 0.06. In the presence phosphatase inhibitor NaF (10 mM), dependency phosphorylation is found to be essentially unchanged: +50 3 1.02 0.04. Thylakoid membranes were in light then incubated at various potentials for 15 min dark; no was observed dephosphorylation any 17 bands distinguishable by autoradiography...

Enzyme activators lower Km (the Michaelis constant) and/or raise Vmax asymptotic reaction velocity at infinite substrate concentration); conversely, inhibitors . But what if an effector moves both and in the same direction? Uncompetitive inhibitors, which decrease by factor, are most common example of this. A less well-known occurs often when crowding agents added to buffer order mimic environment commonly encountered vivo. Crowding tested on different enzymes have been shown every...

IUPAC gives several different definitions of oxidation: loss electrons, increase in oxidation state, hydrogen, or gain oxygen. Most introductory general chemistry textbooks use all these at one time another, which can lead to some confusion the minds first-year students. Some paradoxical "exceptions" include (i) real electrons are not always lost oxidations; (ii) hydrogen and oxygen transfer reactions redox reactions; (iii) oxidations that involve oxygen, atom is oxidant. The "increase...

The toxicity of mercury is often attributed to its tight binding cysteine thiolate anions in vital enzymes. To test our hypothesis that Hg(II) histidine could be a significant factor mercury's toxic effects, we studied the enzyme chymotrypsin, which lacks free thiols; found chymotrypsin not only inhibited, but also denatured by Hg(II). We followed aggregation increase visible absorbance due light scattering. Hg(II)-induced precipitation increased dramatically above pH 6.5, and imidazole...

Living cells are crowded. The presence of so many macromolecules packed into a confined environment affects the structure and function biological components, kinetics thermodynamics biochemical reactions. In fact, crowding studies have already led to important insights, such as existence metabolons other temporary protein complexes that play essential roles in metabolism, cell signaling, organization intracellular environment. Even so, this topic is rarely addressed chemistry biochemistry...

Recently, in a paper entitled "Protonic conductor: Better understanding [sic] neural resting and action potential," Lee applied his Transmembrane Electrostatically-Localized Protons (TELP) hypothesis to neuronal signaling. He stated that Hodgkin's cable theory "could not fully explain the different conductive patterns unmyelinated myelinated nerves," whereas TELP "enables much better of resting/action potential [the biological significance of] axon myelination…" However, Lee's predicts under...

Recent high-resolution pH measurements in mitochondria show ΔpH across the F1F0 ATP synthase to be quite low, 0.07–0.32. Our meta-analysis of published values transmembrane potential (Δψ) shows it identical vivo and vitro: -159 ± 16 mV. With low ΔpH, thermodynamic efficiency proton-driven synthesis exceeds 100 % for average- low-potential (−123 mV) mitochondria, possibly also high-potential (−180 mitochondria. Efficiencies exceeding may violate second law thermodynamics, suggest a need...

In a recent series of papers, James W. Lee reported that mitochondrial oxidative phosphorylation violates the second law thermodynamics and it is allowed to do so because "Type-B" process features lateral longitudinal membrane asymmetry. We show here these contentions are based on problematic interpretations literature. More reliable values Δ

For some time now, there has been disagreement concerning the best way to denote aqueous proton in chemical equations. Recent results have shown that although hydronium ion, H3O+, may exist as a participant kinetic mechanisms, thermodynamic ground-state structure for hydrated is actually hexahydrate, H+·(H2O)6, or H13O6+. We report here short history of this debate and brief summary recent spectroscopic results. Finally, we argue overwhelming majority reactions studied lower-division college...

ADVERTISEMENT RETURN TO ISSUEPREVDemoNEXTSurface Tension Gradients Induced by Temperature: The Thermal Marangoni EffectMarcos Gugliotti , Mauricio S. Baptista Mario J. Politi Todd P. Silverstein and Carl D. Slater View Author Information Instituto de Quimica, Universidade São Paulo, CEP: 05508-900 Brazil Department of Chemistry, Willamette University, Salem, OR 97301-3922 Michigan State East Lansing, MI 48824Cite this: Chem. Educ. 2004, 81, 6, 824Publication Date (Web):June 1,...

Abstract We have developed a multiweek laboratory project in which students isolate myoglobin and characterize its structure, function, redox state. The important techniques covered this include size‐exclusion chromatography, electrophoresis, spectrophotometric titration, FTIR spectroscopy. Regarding protein work with computer modeling visualization of homologues, after they spectroscopically thermal denaturation. Students also study function (ligand binding equilibrium) are instructed on...

Although the pKa of water has been shown to be 14.0 at 25 °C both experimentally and theoretically, a subset organic chemists listed as 15.7 aqueous proton (H+ or H3O+) −1.7 since least early 1930s. These values were found primarily in research literature until 1960s, which time they began appearing chemistry textbooks. The validity 15.7/–1.7 fiercely debated literature. At heart one argument supporting these is proposal that small concentration "solute" molecules, H2O(aq), can exist...

The high propensity of protons to stay at interfaces has attracted much attention over the decades. It enables long-range interfacial proton diffusion without relying on titratable residues or electrostatic attraction. As a result, various phenomena manifest themselves, ranging from spillover in material sciences local circuits between pumps and ATP synthases bioenergetics. In an attempt replace all existing theoretical experimental insight into origin protons’ preference for interfaces,...