Energetic Changes Research Articles

Performance of Li-Ion Batteries: Contribution of Electronic and Ionic Factors

Different combinations of cathode and anode materials have been investigated for improving the energy content of Li-ion battery materials. One of the dominant factors of performance is related to the achieved battery voltage depending on the charging state of the battery. The voltage difference of the electrochemical cell is given by the change in the Gibbs energy for the exchange of Li which will again will depend on the exchange of electrons and ions between the two phases. A systematic experimental study on the relative influence of both contributions on the measurable battery voltage have not been performed yet. Therefore we will present in this contributions surface science studies of well-defined thin film electrodes which allows to compare changes in electronic structure and related electronic surface potentials with voltage measurements. In addition, we will present first experiments on the direct measurements of the ionic work function. A number of different thin film cathode materials with different composition of the layered oxides and olivine structural family have been prepared in recent years mostly by sputter deposition inside an integrated UHV system. Subsequently, the electronic structure and surface potentials as e. g. the electronic work function and the changes induced with charging have been determined by applying photoelectron spectroscopy. The experiments allow to relate energetic changes in the Fermi level positions to the measured battery voltage and thus deduce the relative contribution of the different electronic chemical potential to the battery voltage. Based on our data we conclude that the major contribution to the battery voltage is related to electronic work function variations of the different electrode materials. In addition, we have performed first experiments by experimentally determining the electronic and ionic work function of electrode materials. Such experiments allow to directly determine the chemical potential of the Li atom as given by the electronic and ionic contribution in relation to the vacuum level. With a Born-Haber cycle we can show that the experimentally determined values are in reasonable correspondence to the battery voltage. Summarizing our results we conclude that the performance of Li-ion batteries depend on the relative changes of bonding contributions for electrons and ions within the used electrodes with electrons providing the larger part to the battery voltage. Measured variations in performance must be related to deviations of the rigid band behavior of the electrode materials and to surface effects occurring in the given battery set-up.

Thermochemical study of tetravalent metal sulfate tetrahydrates: A4+(SO4)2(H2O)4 (A4+ = Zr, Ce, U)

The syntheses, characterization, and calorimetric measurements of enthalpies of formation of four tetravalent metal sulfate tetrahydrates (A4+(SO4)2(H2O)4 (A4+ = Zr, Ce, U): α-Zr(SO4)2(H2O)4, α-Ce(SO4)2(H2O)4, β-Ce(SO4)2(H2O)4, and β-U(SO4)2(H2O)4) are reported. Direct calorimetric measurements showed that the formation enthalpies of these compounds from the corresponding oxides correlate with the eightfold coordination radius of the tetravalent cations. An energetic slope change is observed between the α- (Fddd) and β- (Pnma) forms and is consistent with previously reported studies.

The Less the Better: How Suppressed Base Addition Boosts Production of Monoclonal Antibodies With Chinese Hamster Ovary Cells.

Biopharmaceutical production processes strive for the optimization of economic efficiency. Among others, the maximization of volumetric productivity is a key criterion. Typical parameters such as partial pressure of CO2 (pCO2) and pH are known to influence the performance although reasons are not yet fully elucidated. In this study the effects of pCO2 and pH shifts on the phenotypic performance were linked to metabolic and energetic changes. Short peak performance of qmAb (23 pg/cell/day) was achieved by early pCO2 shifts up to 200 mbar but followed by declining intracellular ATP levels to 2.5 fmol/cell and 80% increase of qLac. On the contrary, steadily rising qmAb could be installed by slight pH down-shifts ensuring constant cell specific ATP production (qATP) of 27 pmol/cell/day and high intracellular ATP levels of about 4 fmol/cell. As a result, maximum productivity was achieved combining highest qmAb (20 pg/cell/day) with maximum cell density and no lactate formation. Our results indicate that the energy availability in form of intracellular ATP is crucial for maintaining antibody synthesis and reacts sensitive to pCO2 and pH-process parameters typically responsible for inhomogeneities after scaling up.

Energetics and Interfacial Interactions of Spliceosomal Protein Dib1 Predicted with MD Simulations

The spliceosome is the highly dynamic macromolecular complex responsible for catalyzing the excision of introns from pre‐messenger RNA. The spliceosome consists of five small nuclear ribonucleoproteins as well as several additional proteins. As part of a complex assembly pathway, the essential protein Dib1 must leave the spliceosome. Experimental analysis has found a temperature sensitive phenotype of Dib1 (TS‐Dib1, F85A) that hinders splicing activity. This phenotype has also been hypothesized to perturb spliceosome assembly. Our current work uses atomistic molecular dynamic (MD) simulations to study the molecular interactions in the region of the spliceosome around Dib1 in order to determine what energetic and structural changes result from this point mutation.Starting with recently published cryo‐EM structures, the spliceosome was reduced to only include components in close proximity to Dib1 (either native or F85A). The reduced Dib1 structure consists of three snRNAs (U4, U5, and U6) and four proteins (Prp6, Prp8, Brr2, Prp31). Both systems, containing either native Dib1 or mutant Dib1, were simulated using atomistic MD simulations to identify energetic differences between native Dib1 and mutant TS‐Dib1. The simulation conditions mimicked the biological conditions of previous bulk splicing assays, with an aqueous solvent, 0.1 M salt, and temperature differences that have experimentally shown TS‐Dib1 inactivation. The MD simulations revealed a lower global binding energy in the TS‐Dib1 system compared to the native Dib1 system. Additionally, interfacial hydrogen bonding patterns displayed increased hydrogen bonding among Prp6, Prp8, and Dib1 in the native Dib1 system that were not present in the TS‐Dib1 system, which could contribute to the lower global binding energy. The results from the MD simulations support the experimentally observed temperature sensitivity in the TS‐Dib1 system and could help explain the role of Dib1 in spliceosome assembly.Support or Funding InformationNIH R15GM120720, Robert A Welch Foundation Grant W‐1905This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Carbon Monoxide Mediated Hydrogen Release from PtCu Single-Atom Alloys: The Punctured Molecular Cork Effect

Pt-based materials are used extensively in heterogeneous catalytic processes, but they are notoriously susceptible to poisoning by CO. In contrast, highly dilute binary alloys formed of isolated Pt atoms in a Cu metal host, known as PtCu single-atom alloys (SAAs), are more resilient to CO poisoning during catalytic hydrogenation reactions. In this article, we describe how CO affects the adsorption and desorption of H2 from a model PtCu(111) SAA surface and gain a microscopic understanding of these species’ interaction at the Pt atom active sites. By combining temperature-programmed desorption and scanning tunneling microscopy with first-principles kinetic Monte Carlo, we identify CO as a Pt site blocker that prevents the low temperature adsorption and desorption of H2, the so-called molecular cork effect, first realized when examining PdCu SAAs. Intriguingly, for the case of PtCu, H2 desorption occurs before CO release is detected. Furthermore, desorption experiments show a nonlinear relationship between CO coverage of the Pt sites and H2 desorption peak temperature. When all the Pt atoms are saturated by CO, a very sharp H2 desorption feature is observed 55 K above the regular desorption temperature of H2. Our simulations reveal that the origin of these effects is the fact that desorption of just one CO molecule from a Pt site facilitates the fast release of many molecules of H2. In fact, just 0.7% of the CO adsorbed at Pt sites has desorbed when the H2 desorption peak maximum is reached. The release of H2 from CO-corked PtCu SAA surfaces is analogous to the escape of gas from a pressurized container with a small puncture. Given that small changes in CO surface coverage lead to large changes in H2 evolution energetics, the punctured molecular cork effect must be considered when modeling reaction mechanisms on similar alloy systems.

Structural and energetic basis for novel epicatechin derivatives acting as GPER agonists through the MMGBSA method

(-)-Epicatechin (Epi) has been demonstrated to activate pathways involved in GPER-stimulated nitric oxide (NO) production via endothelial NO synthase, known as the eNOS/NO pathway. Previous studies combining synthesis of four Epi derivatives demonstrated that Epi and Epi-prop, Epi-4-prop and Epi-5-prop were able to bind GPER by acting as GPER agonists, whereas docking studies allowed observation of structural details of the binding of these derivatives at the GPER binding site. However, due to the nature of past studies, the theoretical methods employed did not allow observation of structural and energetic details linked to ligand binding at the GPER binding site. In this contribution, we explore the structural and energetic changes coupling the binding of Epi and its four derivatives to GPER. To this end, MD simulations on the microsecond scale (1 μs) with an MMGBSA approach were used for each GPER-ligand complex. Energetic analysis demonstrated that incorporation of several aliphatic chains to Epi contributed to increasing the affinity towards the GPER binding site, thus helping to explain the experimental evidence. Structural analysis demonstrated that Epi, Epi-4-prop and Epi-5-prop share more similar interactions at GPER binding sites with similar conformational behavior than with Epi-prop and Epi-Ms. However, Epi-prop had additional residues that could explain its different but related biological effects.

Local topology and its effects on grain boundary and solute segregation in HCP magnesium

First principles simulations were carried out to study the energetics of ten special grain boundaries in pure magnesium. The relaxed systems were subjected to topological analysis which revealed correlation between grain boundary energy and local structures conforming to the Mg bulk symmetry. In addition, three different elements with various observed effects were selected from groups 4, 12 and lanthanides of the periodic table and energetic changes imparted by them were calculated for two boundaries with the lowest and higher interfacial energy, respectively. Local topological analysis based on Voronoi polyhedra was utilized to estimate the atomic volume of each segregant and the strain energy associated with it. The contributions of strain and chemical bonding to the grain boundary energetics were then assessed. It was found that while the variation of computed energetics can be justified by the cooperative and competitive role of the strain and chemical bonding respectively, topological analysis applied to the boundary served as an effective complementary method to explain segregation-induced energetic variations.

Gene expression and energetic metabolism changes in the whiteleg shrimp (Litopenaeus vannamei) in response to short‐term hypoxia

In shrimp, several physiological, metabolic and gene expression patterns related to the use of carbohydrates have been associated with hypoxia since this limiting factor modifies aerobic glycolysis to anaerobic glycolysis. The aim of this work was to analyse the effect of short-term hypoxia on oxygen consumption (OC), carbohydrate content and expression of hypoxia inducible factor 1 (HIF-1), glycolysis and Krebs’ cycle genes in Litopenaeus vannamei juvenile shrimps to elucidate use of energy in shrimps during the periods of low oxygen concentration commonly found in culture ponds. At low oxygen concentration, a decrease in shrimp OC, an increase in carbohydrate content and an increase in expression of HIF-1, glycolysis and Krebs’ cycle genes in shrimp gills were registered. These results might indicate that exposure of L. vannamei to short-term hypoxia implies the use of carbohydrates as metabolic fuel triggered by an increase in transcription of HIF-1, glycolysis and Krebs’ cycle pathway genes, as a strategy to maintain a balance between oxidative and anaerobic metabolism and to sustain the energy supply as a compensation to low oxygen availability.

Orientational Order in Self-Assembled Nanocrystal Superlattices.

Self-assembly of nanocrystals into functional materials requires precise control over nanoparticle interactions in solution that are dominated by organic ligands that densely cover the surface of nanocrystals. Recent experiments have demonstrated that small truncated-octahedral nanocrystals can self-assemble into a range of superstructures with different translational and orientational order of nanocrystals. The origin of this structural diversity remains unclear. Here, we use molecular dynamics computer simulations to study the self-assembly of these nanocrystals over a broad range of ligand lengths and solvent conditions. Our model, which is based on a coarse-grained description of ligands and solvent effects, reproduces the experimentally observed superstructures, including recently observed superlattices with partial and short-ranged orientational alignment of nanocrystals. We show that small differences in nanoparticle shape, ligand length and coverage, and solvent conditions can lead to markedly different self-assembled superstructures due to subtle changes in the free energetics of ligand interactions. Our results rationalize the large variety of different reported superlattices self-assembled from seemingly similar particles and can serve as a guide for the targeted self-assembly of nanocrystal superstructures.

Cu and Zr surface sites in photocatalytic activity of TiO2 nanoparticles: The effect of Zr distribution

The present work is focused on the role of ZrO2 modification in the performance of CuO modified TiO2. Zirconia loading leads to formation of more resistant photocatalytic layers compared to samples modified with only copper containing species. Surface modification of mixed phase TiO2 with CuO/ZrO2 improves the degradation of Reactive blue 19 dye under simulated solar irradiation. An in-depth investigation of the catalysts showed that in case of CuO/ZrO2 modification, the covering of the TiO2 surface with zirconium containing species prevents morphological and harmful energetic changes induced by copper species formed on the rutile TiO2 phase at a higher copper loading.

Hibernation and daily torpor in Australian and New Zealand bats: does the climate zone matter?

We aim to summarise what is known about torpor use and patterns in Australian and New Zealand (ANZ) bats from temperate, tropical/subtropical and arid/semiarid regions and to identify whether and how they differ. ANZ bats comprise ~90 species from 10 families. Members of at least nine of these are known to use torpor, but detailed knowledge is currently restricted to the pteropodids, molossids, mystacinids, and vespertilionids. In temperate areas, several species can hibernate (use a sequence of multiday torpor bouts) in trees or caves mostly during winter and continue to use short bouts of torpor for the rest of the year, including while reproducing. Subtropical vespertilionids also use multiday torpor in winter and brief bouts of torpor in summer, which permit a reduction in foraging, probably in part to avoid predators. Like temperate-zone vespertilionids they show little or no seasonal change in thermal energetics during torpor, and observed changes in torpor patterns in the wild appear largely due to temperature effects. In contrast, subtropical blossom-bats (pteropodids) exhibit more pronounced daily torpor in summer than winter related to nectar availability, and this involves a seasonal change in physiology. Even in tropical areas, vespertilionids express short bouts of torpor lasting ~5 h in winter; summer data are not available. In the arid zone, molossids and vespertilionids use torpor throughout the year, including during desert heat waves. Given the same thermal conditions, torpor bouts in desert bats are longer in summer than in winter, probably to minimise water loss. Thus, torpor in ANZ bats is used by members of all or most families over the entire region, its regional and seasonal expression is often not pronounced or as expected, and it plays a key role in energy and water balance and other crucial biological functions that enhance long-term survival by individuals.

Отражение света от слоя гиперболического метаматериала

In this paper, we study the features of reflection of a plane elliptically polarized electromagnetic wave falling from an isotropic non-absorbing medium on a layer of hyperbolic metamaterial (HMM) the optical axis of which is parallel to the interface and the diagonal values ​​of the dielectric constant are less than the dielectric constant of an isotropic medium. It is shown that changing the values of the angle of incidence and the angle between the plane of incidence and the optical axis of the HMM one can realize different regimes of refrection: when ordinary ( or extraodinary) wave or both waves decay from the interface. Meanwhile, in the latter case, for some values ​​of the angles the decaying can be nonexponential. For these three cases, numerical calculations of the reflection coefficient from the ITO / Ag nanostructure layer are performed. When the polarization of the incident wave varies, the energetic reflection coefficient changes from minimum to maximum values which depend on the layer thickness. Unlike usual anisotropic media, in all cases the maximum value of the reflection coefficient tends to unity with increasing the layer thickness. When the amplitude of the ordinary or extraordinary wave does not decrease from the interface, the minimum reflection coefficient periodically vanishes with increasing layer thickness due to the interference. In the case when both waves decay, and under some conditions the incidence is not exponential, the minimum reflection coefficient vanishes at a certain layer thickness, and then tends to unity.

Effect of Familial Mutations on the Interconversion of α-Helix to β-Sheet Structures in an Amyloid-Forming Peptide: Insight from Umbrella Sampling Simulations.

Understanding the initial events of aggregation of amyloid β monomers to form β-sheet rich fibrils is useful for the development of therapeutics for Alzheimer's disease. In this context, the changes in energetics involved in the aggregation of helical amyloid β monomers into β-sheet rich dimers have been investigated using umbrella sampling simulations and density functional theory calculations. The results from umbrella sampling simulations for the free energy profile for the interconversion closely agree with the results of density functional theory calculations. The results reveal that helical peptides converted to β-sheet structures through coil-like conformations as intermediates that are mostly stabilized by intramolecular hydrogen bonds. The stabilization of intermediate structures could be a possible way to inhibit fibril formation. Mutations substantially decrease the height of the energy barrier for interconversion from α-helix to β-sheet structure when compared to that of the wild type, something that is attributed to an increase in the number of intramolecular hydrogen bonds between backbone atoms in the coil structures that correspond to a maximum value on the free energy surface. The reduction of the energy barrier leads to an enhancement of the rate of aggregation of amyloid β monomers upon introduction of various familial mutations, which is consistent with previous experimental reports.

Ab Initio Investigation of Atomistic Insights into the Nanoflake Formation of Transition-Metal Dichalcogenides: The Examples of MoS2, MoSe2, and MoTe2

An atom-level understanding of the evolution of the physical and chemical properties of transition-metal dichalcogenide (TMD) nanoflakes is a key step to improve our knowledge of two-dimensional (2D) TMD materials, which can help in the designing of new 2D materials. Here, we report a density functional theory (DFT) study of the evolution of the structural, energetic, and electronic properties of (MoQ2)n nanoflakes, where Q = S, Se, and Te and n = 1–16. All optimized DFT configurations for each system (10n) were generated by an in-house implementation of the tree-growth scheme combined with the modified Euclidean similarity distance algorithm, which reduces a large set configurations (10n million) to 10n trial structures. We found that the energetic favored configurations change between two sorts of clusters: frameworks elongated in one dimension with tetrahedral and square pyramidal coordination of Mo atoms, which is followed by 2D nanoflakes with tetrahedral, square pyramidal, and distorted octahedral c...

Chemical Effects on Subcritical Fracture in Silica From Molecular Dynamics Simulations

AbstractFracture toughness of silicates is reduced in aqueous environments due to water‐silica interactions at the crack tip. To investigate this effect, classical molecular dynamics simulations using the bond‐order‐based reactive force field (ReaxFF) were used to simulate silica fracture. The chemical and mechanical aspects were separated by simulating fracture in (a) a vacuum with dynamic loading, (b) an aqueous environment with dynamic loading, and (c) an aqueous environment with static subcritical mechanical loading to track silica dissolution. The addition of water to silica fracture reduced the silica fracture toughness by ~25%, a trend consistent with experimentally reported results. Analysis of Si─O bonds in the process zone and calculations of dissipation energy associated with fracture indicated that water relaxes the entire process zone and not just the surface. Additionally, the crack tip sharpens during fracture in water and an increased number of microscopic propagation events occur. This results in earlier fracture in systems with increasing mechanical loading in aqueous conditions, despite the lack of significant silica dissolution. Therefore, the threshold for Si─O bond breakage has been lowered in the presence of water and the reduction in fracture toughness is due to structural and energetic changes in the silica, rather than specific dissolution events.

Understanding Film-To-Stripe Transition of Conjugated Polymers Driven by Meniscus Instability.

Meniscus instability during meniscus-guided solution coating and printing of conjugated polymers has a significant impact on the deposit morphology and the charge-transport characteristics. The lack of quantitative investigation on meniscus-instability-induced morphology transition for conjugated polymers hindered the ability to precisely control conjugated polymer deposition for desired applications. Herein, we report a film-to-stripe morphology transition caused by stick-and-slip meniscus instability during solution coating seen in multiple donor-acceptor polymer systems. We observe the coexistence of film and stripe morphologies at the critical coating speed. Surprisingly, higher charge-carrier mobility is measured in transistors fabricated from stripes despite their same deposition condition as the films at the critical speed. To understand the origin of the morphology transition, we further construct a generalizable surface free energy model to validate the hypothesis that the morphology transition occurs to minimize the system surface free energy. As the system surface free energy varies during a stick-and-slip cycle, we focus on evaluating the maximum surface free energy at a given condition, which corresponds to the sticking state right before slipping. Indeed, we observe the increase of the maximum system surface free energy with theincrease in coating speed prior to film-to-stripe morphology transition andanabrupt drop in the maximum system surface free energy post-transition when the coating speed is further increased,whichisassociatedwith thereduced meniscus length during stripe deposition. Such an energetic change originates from the competition between pinning and depinning forces on a partial wetting substrate which underpins the film-to-stripe transition. This work establishes a quantitative approach for understanding meniscus-instability-induced morphology transition during solution coating. The mechanistic understanding may further facilitate the use of meniscus instability for lithography-free patterning or to suppress instability for highly homogeneous thin film deposition.

How Hydrophobic Hydration Destabilizes Surfactant Micelles at Low Temperature: A Coarse-Grained Simulation Study.

Micelles are self-assembled aggregates of amphiphilic surfactant molecules that are important in a variety of applications, including drug delivery, detergency, and catalysis. It is known that the micellization process is driven by the same physiochemical forces that drive protein folding, aggregation, and biological membrane self-assembly. Nevertheless, the molecular details of how micelle stability changes in water at low temperature are not fully clear. We develop and use a coarse-grained model to investigate how the interplay between nonionic surfactants and the surrounding water at the nanoscale affects the stability of micelles at high and low temperatures. Simulations of preformed C12E5 micelles in explicit water at a range of temperatures reveal the existence of two distinct surfactant conformations within the micelle, a bent structure and an extended structure, the latter being more prevalent at low temperature. Favorable interactions of the surfactant with more ordered solvation water stabilizes the extended configuration, allowing nanoscale wetting of the dry, hydrophobic core of the micelle, leading to the micelle breaking. Taken together, our coarse-grained simulations unravel how energetic and structural changes of the surfactant and the surrounding water destabilize micelles at low temperature, which is a direct consequence of the weakened hydrophobicity. Our approach thus provides an effective mean for extracting the molecular-level changes during hydrophobicity-driven destabilization of molecular self-assembly, which is important in a wide range of fields, including biology, polymer science, and nanotechnology.

Insecticide-resistance mechanism of Plutella xylostella (L.) associated with amino acid substitutions in acetylcholinesterase-1: A molecular docking and molecular dynamics investigation

Acetylcholinesterase-1 (AChE1) is a vital enzyme involved in neurotransmission and represents an attractive insecticide-target for organophosphates and carbamates in Plutella xylostella (Linneaus), an important pest of cruciferous crops worldwide. However, insecticide-resistance often occurs due to mutations, making many organophosphates and carbamates ineffective. In particular, A298S and G324A mutations in AChE1 significantly lower the binding affinity of insecticides. In the present study, the wild-type and mutant AChE1 structures were constructed and their structural stabilities, residual flexibilities were investigated through molecular dynamics simulations. Subsequently, the structural and energetic changes responsible for the insecticide-resistance in AChE1 were analyzed using molecular docking. The results of molecular dynamics simulation showed that the mutant AChE1 shows little structural deviation than the wild-type, indicate the structural instability. Furthermore, the docking results demonstrated that these mutations break the intermolecular hydrogen bonding interactions and thereby affect the prothiofos as well as all insecticide binding. Hence, the results could provide some insights into the resistance mechanism of AChE1 in insecticides binding and helpful in the development of novel insecticides that are less susceptible to insecticide-resistance.

Decadal Variability of Eddy Characteristics and Energetics in the Kuroshio Extension: Unstable Versus Stable States

AbstractUsing the Estimating Circulation and Climate of the Ocean Phase II product, this study investigates the eddy characteristics and energetics in two dynamical regimes within the Kuroshio Extension (KE) region. Based on the empirical orthogonal function analysis, it is found that the decadal evolution of eddy kinetic energy in the KE region is characterized by a delayed negative correlation between the upstream and downstream. Besides the out‐of‐phase change in eddy activity levels, eddy characteristics and energetics in the upstream KE are also different from those in the downstream. In the upstream region, eddies are stretched in the zonal direction and the unstable state is characterized by strong eddy‐shedding processes. During these processes, cyclonic eddies are found to be formed in the first quasi‐stationary meander and finally pinched off from the KE jet. Energy budget illustrates that the eddy shedding processes are triggered by baroclinic instability, while barotropic instability becomes the dominated energy source after the meander is fully developed. Accompanied by the generation of cyclonic eddies, significant inverse energy cascade is detected. When the upstream KE is stable, the eddy activity is dominated by baroclinic instability and the inverse energy cascade occurs similarly. Distinct from the upstream, eddies in the downstream KE tend to be stretched in the meridional direction and the decadal variability of eddy kinetic energy in this region is mainly regulated by the upstream through lateral advection.

Unraveling the mechanism of the cadherin-catenin-actin catch bond.

The adherens junctions between epithelial cells involve a protein complex formed by E-cadherin, β-catenin, α-catenin and F-actin. The stability of this complex was a puzzle for many years, since in vitro studies could reconstitute various stable subsets of the individual proteins, but never the entirety. The missing ingredient turned out to be mechanical tension: a recent experiment that applied physiological forces to the complex with an optical tweezer dramatically increased its lifetime, a phenomenon known as catch bonding. However, in the absence of a crystal structure for the full complex, the microscopic details of the catch bond mechanism remain mysterious. Building on structural clues that point to α-catenin as the force transducer, we present a quantitative theoretical model for how the catch bond arises, fully accounting for the experimental lifetime distributions. The underlying hypothesis is that force induces a rotational transition between two conformations of α-catenin, overcoming a significant energy barrier due to a network of salt bridges. This transition allosterically regulates the energies at the interface between α-catenin and F-actin. The model allows us to predict these energetic changes, as well as highlighting the importance of the salt bridge rotational barrier. By stabilizing one of the α-catenin states, this barrier could play a role in how the complex responds to additional in vivo binding partners like vinculin. Since significant conformational energy barriers are a common feature of other adhesion systems that exhibit catch bonds, our model can be adapted into a general theoretical framework for integrating structure and function in a variety of force-regulated protein complexes.