Equivalent Sites Research Articles

Dichotomous disorder model for single light-harvesting complexes

Photosynthetic organisms conserve the captured energy of solar radiation into stable chemical forms. To do so, they have evolved specialized systems of pigment–protein complexes consisting of light-harvesting antennas and reaction centres. Photosynthetic antennas contain remarkably dense arrangements of light-absorbing pigments held by the protein scaffold, and their function is to absorb light and funnel the excitation energy to the reaction centre. Decades of experimental and theoretical research resulted in a detailed understanding of the energy migration pathways within the photosynthetic apparatus. The key parameters determining the excitation relaxation and transfer are inter-pigment coupling and energetic disorder or non-equality of excitation energies at equivalent pigment sites due to the interaction with the disordered protein scaffold. Circularly symmetric light-harvesting antennas from purple bacteria present a beautiful example of the interplay between these parameters. The spectral signature of this interplay could be observed with the single-molecule fluorescence microscopy techniques. The results of these measurements were interpreted with an intuitively clear dichotomous model of disorder of pigment site energies.

The FKBP12 subunit modifies the long-range allosterism of the ryanodine receptor

Ryanodine receptors (RyRs) are large conductance intracellular channels controlling intracellular calcium homeostasis in myocytes, neurons, and other cell types. Loss of RyR’s constitutive cytoplasmic partner FKBP results in channel sensitization, dominant subconductance states, and increased cytoplasmic Ca2+. FKBP12 binds to RyR1’s cytoplasmic assembly 130 Å away from the ion gate at four equivalent sites in the RyR1 tetramer. To understand how FKBP12 binding alters RyR1’s channel properties, we studied the 3D structure of RyR1 alone in the closed conformation in the context of the open and closed conformations of FKBP12-bound RyR1. We analyzed the metrics of conformational changes of existing structures, the structure of the ion gate, and carried out multivariate statistical analysis of thousands of individual cryoEM RyR1 particles. We find that under closed state conditions, in the presence of FKBP12, the cytoplasmic domain of RyR1 adopts an upward conformation, whereas absence of FKBP12 results in a relaxed conformation, while the ion gate remains closed. The relaxed conformation is intermediate between the RyR1-FKBP12 complex closed (upward) and open (downward) conformations. The closed-relaxed conformation of RyR1 appears to be consistent with a lower energy barrier separating the closed and open states of RyR1-FKBP12, and suggests that FKBP12 plays an important role by restricting conformations within RyR1’s conformational landscape.

A new, deep quinoxaline-based cavitand receptor for the complexation of benzene.

We report the synthesis of a new macrocyclic receptor, namely 2,8,14,20-tetra-hexyl-4,24:6,10:12,16:18,22-O,O'-tetra-kis-[2,3-di-hydro-[1,4]dioxino[2,3-g]quinoxalin-7,8-di-yl]resorcin[4]arene, DeepQxCav, obtained by the addition of ethyl-ene glycol di-tosyl-ate to an octa-hydroxy quinoxaline cavitand. A 1:1 supra-molecular complex of this cavitand with benzene has been obtained and analysed through X-ray diffraction analysis. The complex, of general formula C92H88O16N8·C6H6, crystallizes in the space group C2/c, with the cavitand host located about a twofold rotation axis. The benzene guest, which is held inside the cavity by C-H⋯π inter-actions and dispersion forces, is disordered over two equivalent sites, one in a general position and one lying on a twofold axis. The crystal structure features C-H⋯O hydrogen bonds and C-H⋯π inter-actions involving the alkyl chains, the aromatic rings, and the O atoms of the dioxane moiety of the resorcinarene scaffold. The crystal studied was refined as a two-component twin.

An investigation on the evaluation of dynamic soil characteristics of the Elazig City through the 1-D equivalent linear site-response analysis

Consideration of the effects of the site response in the design of civil structures systems is of important to mitigate the damages to a certain extent on structures and the environment. Hence, it is relatively crucial to reliably attain the dynamic soil parameters of an earthquake-prone city/state. In the current study, a comprehensive investigation on the dynamic soil properties of the city of Elazig with very close proximity to the East Anatolian Fault Zone (EAFZ) having a high potential of producing destructive earthquakes is carried out. Performing probabilistic seismic hazard analysis (PSHA), the moment magnitude of the city is determined as Mw = 7.7 according to 10% probability of exceedance in 50 years. Bedrock-level acceleration spectra is developed utilizing different attenuation relationships for the city, and 1-D equivalent linear site response analysis is conducted on an example soil profile of the city through the SHAKE2000 software considering 16 earthquake motions recorded at the bedrock level. Local surface acceleration spectra obtained from the analysis are then compared to the design spectra of the Turkish Seismic Code for Buildings (TSCB) and Eurocode-8 (EC8) in an attempt to identify the difference between the code spectra and local surface spectra. In addition, in situ geotechnical tests of standard penetration and seismic refraction are conducted at different locations of the study area. Incorporating the results from the field tests into the site response analysis, the soil amplification factor, predominant soil period, peak ground acceleration and spectral maps for the period of T = 0.2 and T = 1.0 s are obtained for the study area. The outcomes from the analysis reveals that structures with higher vibration period than T = 1.0 s are subjected to lower spectral acceleration (Sa), whereas higher Sa values can be used for those with a vibration period lower than T = 0.2 s.

Controlling the preferential motion of chiral molecular walkers on a surface.

Molecular walkers standing on two or more "feet" on an anisotropic periodic potential of a crystal surface may perform a one-dimensional Brownian motion at the surface-vacuum interface along a particular direction in which their mobility is the largest. In thermal equilibrium the molecules move with equal probabilities both ways along this direction, as expected from the detailed balance principle, well-known in chemical reactivity and in the theory of molecular motors. For molecules that possess an asymmetric potential energy surface (PES), we propose a generic method based on the application of a time-periodic external stimulus that would enable the molecules to move preferentially in a single direction thereby acting as Brownian ratchets. To illustrate this method, we consider a prototypical synthetic chiral molecular walker, 1,3-bis(imidazol-1-ylmethyl)-5(1-phenylethyl)benzene, diffusing on the anisotropic Cu(110) surface along the Cu rows. As unveiled by our kinetic Monte Carlo simulations based on the rates calculated using ab initio density functional theory, this molecule moves to the nearest equivalent lattice site via the so-called inchworm mechanism in which it steps first with the rear foot and then with the front foot. As a result, the molecule diffuses via a two-step mechanism, and due to its inherent asymmetry, the corresponding PES is also spatially asymmetric. Taking advantage of this fact, we show how the external stimulus can be tuned to separate molecules of different chirality, orientation and conformation. The consequences of these findings for molecular machines and the separation of enantiomers are also discussed.

Matrix-induced Linear Stark Effect of Single Dibenzoterrylene Molecules in 2,3-Dibromonaphthalene Crystal.

Absorption and fluorescence from single molecules can be tuned by applying an external electric field – a phenomenon known as the Stark effect. A linear Stark effect is associated to a lack of centrosymmetry of the guest in the host matrix. Centrosymmetric guests can display a linear Stark effect in disordered matrices, but the response of individual guest molecules is often relatively weak and non‐uniform, with a broad distribution of the Stark coefficients. Here we introduce a novel single‐molecule host‐guest system, dibenzoterrylene (DBT) in 2,3‐dibromonaphthalene (DBN) crystal. Fluorescent DBT molecules show excellent spectral stability with a large linear Stark effect, of the order of 1.5 GHz/kVcm−1, corresponding to an electric dipole moment change of around 2 D. Remarkably, when the electric field is aligned with the a crystal axis, nearly all DBT molecules show either positive or negative Stark shifts with similar absolute values. These results are consistent with quantum chemistry calculations. Those indicate that DBT substitutes three DBN molecules along the a‐axis, giving rise to eight equivalent embedding sites, related by the three glide planes of the orthorhombic crystal. The static dipole moment of DBT molecules is created by host‐induced breaking of the inversion symmetry. This new host–guest system is promising for applications that require a high sensitivity of fluorescent emitters to electric fields, for example to probe weak electric fields.

Role of crystal transformation on the enhanced thermoelectric performance in Mn-doped Cu2SnS3

Mohite-type Cu2SnS3 exhibits a large degree of manipulation in both electronic and phonon transport properties by transition metal doping. In this work, the effects of Mn doping on the transport properties of Cu2SnS3 were investigated. A crystal transition occurred upon doping from cation-ordered monoclinic structure to cation-disordered cubic and tetragonal structures. Such a crystal transition caused a significant increase of DOS effective mass of carriers, m*, which should be caused by the improved degeneracy of the bands at the Fermi level due to the improved symmetry, and also by the participation (in the upper valence bands) of unfilled d-orbitals of Mn cations that share crystallographically equivalent sites with Cu cations. Meanwhile the lattice thermal conductivity (∼0.4 W m−1K−1 at ∼773 K) was suppressed effectively, which should also be linked to the disorder structure induced by Mn-doping. Benefitting from the increased carrier density and much improved m*, a remarkable power factor of 0.92 mWm−1K−2 has been obtained at 723 K. The highest ZT ∼0.68 at 723 K is almost 15 times increased as compared to that of pristine Cu2SnS3.

Evaluation of the site amplification factors estimated by equivalent linear site response analysis using time series and random vibration theory based approaches

The objective of this study is to estimate and compare the site amplification factors (AFs) using two different one dimensional (1-D) equivalent-linear (EQL) site response analysis approaches: the time series (TS) approach and the random vibration theory (RVT) based method. For this purpose, random soil profiles combined with different soil types, EQL soil properties, and unit weights are tested at several input ground motion levels. Analysis results showed that the AFs estimated by the TS-approach are systematically higher than the AFs estimated by the RVT-based method in the short period range (T < 0.5 s), especially when the bedrock peak ground acceleration is higher than 0.2 g. The relative difference between the AFs estimated in both methods is most prominent in granular soils: differences reach up to 35–40% compared to 10–15% for clays. On the other hand, the AFs calculated in this study are in good agreement with the empirical AF models utilized in recent ground motion models, indicating that the RVT-based AF models may be preferred in the future to cover a larger range of scenarios than the empirical datasets.

Effect of Electron-Nuclear Hyperfine Interactions on Multiple-Quantum Coherences in Photogenerated Covalent Radical (Qubit) Pairs.

Ultrafast photodriven electron transfer reactions starting from an excited singlet state in an organic donor-acceptor molecule can generate a spin-correlated radical pair (RP) with an initially entangled spin state that may prove useful as a two-qubit pair in quantum information protocols. Here we investigate the effects of modulating electron-nuclear hyperfine coupling by rapidly transferring an electron between two equivalent sites comprising the reduced acceptor of the RP. A covalent electron donor-acceptor molecule including a tetrathiafulvalene (TTF) donor, a 4-aminonaphthalene-1,8-imide (ANI) chromophoric primary acceptor, and an m-xylene bridged cyclophane having two equivalent pyromellitimides (PI2), TTF-ANI-PI2, as a secondary acceptor was synthesized along with an analogous molecule having one pyromellitimide (PI) acceptor, TTF-ANI-PI. Photoexcitation of ANI within each molecule results in sub-nanosecond formation of TTF+•-ANI-PI-• and TTF+•-ANI-PI2-•. The effect of reducing electron-nuclear hyperfine interactions in TTF+•-ANI-PI2-• relative to TTF+•-ANI-PI-• on decoherence of multiple-quantum coherences has been measured by pulse-EPR spectroscopy. This contribution is especially relevant in the absence of modulation of exchange or dipolar interactions, as with the RP at a fixed distance in the molecules in this work. The theoretical prediction of the contribution from an ensemble of hyperfine interactions to decoherence in these RPs is shown to be less than the full width at half-maximum of the quantum beat frequencies measured experimentally. Pulse bandwidth and off-resonant excitation by square microwave pulses are proposed as larger contributors to decoherence in these molecules than the hyperfine interactions, and specific pulse shapes relevant to arbitrary waveform generation are introduced.

Equivalent linear computation of response spectra for liquefiable sites: The spectral interpolation method

A simplified methodology is presented for the computation of elastic response spectra at liquefiable sites, based on the widely used equivalent linear site response analysis method. The target response spectrum is obtained by frequency dependent interpolation between the response spectra for “non-liquefied” and for “liquefied” ground, the former computed for the native soil properties, without excess pore pressure buildup, and the latter for the properties of the liquefied soil. Apart from the structural frequency, the interpolation coefficient is also related to the factor of safety against liquefaction. In this way, the proposed methodology takes indirectly into account the initial segment of the seismic excitation time-history, until the onset of liquefaction, which is of cornerstone importance for the overall ground response at sites with low and moderate liquefaction potential. Results of parametric nonlinear numerical analyses and three field case studies are used to calibrate the methodology and evaluate its accuracy. In addition, the potential of the proposed methodology for defining code-oriented design spectra for liquefiable sites is examined.

Treatment of personality disorder using a whole of service stepped care approach: A cluster randomized controlled trial.

Background and objectivesPeople with personality disorders are prevalent in emergency and inpatient mental health services. We examined whether implementing a stepped care model of psychological therapy reduces demand on hospital units by people with personality disorder, in a cluster randomized controlled trial.MethodA total of 642 inpatients (average age 36.8, 50.5% female) with a primary ICD-10 personality disorder were recruited during 18 months baseline, then monitored during an 18 month active trial phase. In the active trial phase two equivalent sites were randomised to either treatment as usual (TAU), or a whole of service intervention that diverted people away from hospital and into stepped care psychological therapy clinics. The study design was cost neutral, with no additional staff or resources deployed between sites. A linear mixed models analysis evaluated outcomes.ResultsAs predicted, demand on hospital services reduced significantly in the intervention compared to TAU site. The intervention site evidenced shorter bed days, from an average of 13.46 days at baseline to 4.28 days per admission, and patients were 1.3 times less likely to re-present to the emergency department compared to TAU. Direct cost savings for implementing the approach was estimated at USD$2,720 per patient per year. Limitations included not directly comparing individual symptom changes.ConclusionsUsing a whole of service stepped care model of treatment for personality disorder significantly reduced demand on hospital services.

Direct observation of symmetrization of hydrogen bond in \u03b4-AlOOH under mantle conditions using neutron diffraction

At ambient pressure, the hydrogen bond in materials such as ice, hydrates, and hydrous minerals that compose the Earth and icy planets generally takes an asymmetric O-H···O configuration. Pressure significantly affects this configuration, and it is predicted to become symmetric, such that the hydrogen is centered between the two oxygen atoms at high pressure. Changes of physical properties of minerals relevant to this symmetrization have been found; however, the atomic configuration around this symmetrization has remained elusive so far. Here we observed the pressure response of the hydrogen bonds in the aluminous hydrous minerals δ-AlOOH and δ-AlOOD by means of a neutron diffraction experiment. We find that the transition from P21nm to Pnnm at 9.0 GPa, accompanied by a change in the axial ratios of δ-AlOOH, corresponds to the disorder of hydrogen bond between two equivalent sites across the center of the O···O line. Symmetrization of the hydrogen bond is observed at 18.1 GPa, which is considerably higher than the disorder pressure. Moreover, there is a significant isotope effect on hydrogen bond geometry and transition pressure. This study indicates that disorder of the hydrogen bond as a precursor of symmetrization may also play an important role in determining the physical properties of minerals such as bulk modulus and seismic wave velocities in the Earth’s mantle.

A spectroscopy and microscopy study of silicon nanoclusters grown on β-Si3N4(0 0 0 1)/Si(1 1 1) interface

Silicon has been grown on the (8 × 8)–reconstructed β-Si3N4(0 0 0 1) surface at 350 °C temperature. The pure Volmer-Weber growth mode has induced the formation of nano-sized silicon clusters randomly distributed on the surface. Synchrotron radiation photoelectron spectroscopy and scanning tunneling microscopy have been employed to study the system. A fit to the photoemission spectra, complemented by topographic information, has allowed us to assign each Si2p and N1s component to the different non equivalent sites of silicon and nitrogen atoms.

Exploring Local Disorder within CAU-1 Frameworks Using Hyperpolarized 129Xe NMR Spectroscopy.

The sorption properties of metal-organic frameworks (MOFs) can be influenced by introducing covalently attached functional side chains, which make this subclass of porous materials promising for applications as diverse as gas storage and separation, catalysis, and drug delivery. The incorporation of side groups usually comes along with disorder, as the synthesis procedures rarely allow for one specific position among a larger group of equivalent sites to be selected. For a series of isoreticular CAU-1 frameworks, chosen as model compounds, one out of four positions at every linker is modified with equal probability. Here, we investigate the influence of this disorder on Ar sorption and 129Xe nuclear magnetic resonance spectroscopy using hyperpolarized 129Xe gas. Models used for predicting the pore dimensions as well as their distributions were derived from the unfunctionalized framework by replacing one proton at every linker with either an amino, an acetamide, or a methyl urea functionality. The resulting structures were optimized using density functional theory (DFT) calculations. Results from void analyses and Monte Carlo force field simulations suggest that for available Ar nonlocal DFT (NLDFT) kernels, neither the pore dimensions nor the distributions induced by the side-chain disorder are well-reproduced. By contrast, we found the 129Xe chemical shift analysis for the shift observed at high temperature to be well-suited to develop a detailed fingerprint of the porosity and side-chain disorder within the isoreticular CAU-1 series. After calibrating the 129Xe limiting shift of the amino-functionalized framework with DFT calculations, the downfield shifts for the other two derivatives are an excellent measure for the reduction of the accessible pore space and reveal a strong preference for the side chains toward the octahedral voids for both cases. We expect that the strategy presented here can be commonly applied to disorder phenomena within MOFs in the future.

Covalent Radical Pairs as Spin Qubits: Influence of Rapid Electron Motion between Two Equivalent Sites on Spin Coherence.

Ultrafast photodriven electron transfer reactions starting from an excited singlet state in an organic donor-acceptor molecule generate a radical pair (RP) in which the two spins are initially entangled and, in principle, can serve as coupled spin qubits in quantum information science (QIS) applications, provided that spin coherence lifetimes in these RPs are long. Here we investigate the effects of electron transfer between two equivalent sites comprising the reduced acceptor of the RP. A covalent electron donor-acceptor molecule (D-C-A24+) including a p-methoxyaniline donor (D), a 4-aminonaphthalene-1,8-imide chromophoric primary acceptor (C), and a m-xylene bridged cyclophane having two equivalent phenyl-extended viologens (A24+) as a secondary acceptor was synthesized along with the analogous molecule having one phenyl-extended viologen acceptor and a second, more difficult to reduce 2,5-dimethoxyphenyl-extended viologen in a very similar cyclophane structure (D-C-A4+). Photoexcitation of C within each molecule results in subnanosecond formation of D+•-C-A23+• and D+•-C-A3+•. The spin dynamics of these RPs were characterized by time-resolved EPR spectroscopy and magnetic field effects on the RP yield in both CH3CN and CD3CN. The data show that rapid electron hopping within A23+• promotes spin decoherence in D+•-C-A23+• relative to D+•-C-A3+• having a monomeric acceptor, while the interaction of the RP electron spins with the nuclear spins of the solvent have little or no effect on the spin dynamics. These observations provide important information for designing and understanding novel molecular assemblies of spin qubits with long coherence times for QIS applications.

Effect of uncertainty in $$V_{\mathrm{S}}{-}N$$ V S - N correlations on seismic site response analysis

This paper studies the reliability of the calculated shear-wave velocity ( $$V_{\mathrm{S}}$$ ) from different available $$V_{\mathrm{S}}$$ and SPT-N correlations in terms of seismic site response analysis. In the present study, various $$V_{\mathrm{S}}$$ –N correlations developed for different regions around the globe have been used to calculate the bound of $$V_{\mathrm{S}}$$ variations with depth at three different sites in Kolkata city. This bound has later been used to generate the random $$V_{\mathrm{S}}$$ profiles using the Monte Carlo simulation. Equivalent linear site response analysis has been performed to study the response of those generated profiles under different input motion excitations. Strong-to-weak ground motion records have been used for this purpose. The amplification spectra of the generated $$V_{\mathrm{S}}$$ profiles using all soil types and specific soil-type $$V_{\mathrm{S}}$$ –N correlations show significant variations. The study also shows that the $$V_{\mathrm{S}}$$ –N correlation may result in quite different $$V_{\mathrm{S},30}$$ values and subsequently it may lead to the different site classes according to the NEHRP 2003 classification. So, the random choice of the $$V_{\mathrm{S}}$$ –N correlation, where the direct measurement of $$V_{\mathrm{S}}$$ is not available, may affect the outcome of seismic hazard analysis significantly. The study points out the need for accurate estimation of the $$V_{\mathrm{S}}$$ profile either from in-situ determination or using site-specific correlation.

Effects of surface rates for the series reaction A → B → C on successive separated spherical sites

A steady - state series reaction A →B → C, consisting of a first reaction A →B on sphere 1 of radius a1 with first order kinetic rate constant kA and reactant diffusivity DA, followed by a second reaction B → C on sphere 2 of radius a2 with a first order kinetic rate constant kB and a B chemical species diffusivity DB, occurs on two discrete chemically active spheres a center - to – center distance d apart. The twin spherical harmonic expansion method with a Neumann iterative solution of the coefficient equations is used to generate a rigorous solution for the rate of series reaction in terms of an expansion in the inverse dimensionless center - to - center sphere separation d (=d⁄((a_1+a_2 ))) up to the inverse thirteenth power. The expansion coefficients depend on three dimensionless parameters (γ,λ_A,λ_B), where the dimensionless inverse surface kinetic constants are λ_A=D_A⁄a_1 kA on sphere 1, λ_B=D_B⁄(a_2 k_B ) on the sphere 2, while the geometry enters as the radius ratio γ=a_1⁄a_2 . Using these results an equivalent site kinetic change is imposed, first to λ_Aon site 1, then to λ_Bon site 2, to determine which site is more influential for the overall series reaction rate. Effects of γ geometry modification at several fixed kinetic surface site rates are examined. When either one of reactive spheres is diffusion controlled, various levels of λ kinetic controls at the other site or γ site geometries are generated to study the effects of site kinetics or geometry control on the series reaction rate. As the “other site” reaction rate also increases toward diffusion control, inflection points are observed to develop as precursors to a local maximum on the series reaction rate versus sphere separation curves. An application to the isomerization of n-pentane is presented.

Probing directionality of local electronic structure by momentum-selected STEM-EELS

Electron energy-loss spectroscopy (EELS) using a scanning transmission electron microscope (STEM) provides information on the local electronic structure around an atomic column irradiated by the incident electron probe. In this study, we present a method for detecting the directionality of chemical bonds with atomic resolution by selecting a specific atomic column and the direction of momentum transfer with an off-axis collection aperture in the STEM-EELS measurement. It is shown that the oxygen K-edge fine structures in SrTiO3 measured from the crystallographically equivalent oxygen sites, which are in TiO-planes perpendicular to the electron probe direction, show different structures depending on the directionality of the σ-bond between the oxygen and titanium atoms. This method opens up a way to explore the electronic states in anisotropic materials and interfaces with atomic resolution.

Reorientation kinetics of hydroxyl groups in anatase TiO2.

The reorientation kinetics of hydrogen in a variety of complexes in the anatase polymorph of TiO2 was investigated by means of stress-induced dichroism. For the hydrogen-defect resulting in an O-H vibrational mode with a frequency of 3389 cm-1, the energy barrier separating adjacent equivalent in-plane sites of hydrogen was determined to be independent of the isotope and equal to 0.74 ± 0.02 eV, whereas the attempt frequency was found to be (1.10 ± 0.20) × 1012 and (0.75 ± 0.15) × 1012 s-1 for hydrogen and deuterium, respectively. The defect with vibrational modes at 3412 and 3417 cm-1 previously assigned to isolated hydrogen did not reveal alignment under the stress up to room temperature, which indicates that the barrier of hydrogen motion is above 0.9 eV.

Time dependent loss of trabecular bone in human tibial plateau fractures.

We investigated if time between injury and surgery affects cancellous bone properties in patients suffering tibial plateau fractures (TPF), in terms of structural integrity and gene expression controlling bone loss. A cohort of 29 TPF, operated 1-17 days post-injury, had biopsies from the fracture and an equivalent contralateral limb site, at surgery. Samples were assessed using micro-computed tomography and real-time RT-PCR analysis for the expression of genes known to be involved in bone remodeling and fracture healing. Significant decreases in the injured vs control side were observed for bone volume fraction (BV/TV, -13.5 ± 6.0%, p = 0.011), trabecular number (Tb.N, -10.5 ± 5.9%, p = 0.041) and trabecular thickness (Tb.Th, -4.6 ± 2.5%, p = 0.033). Changes in these parameters were more evident in patients operated 5-17 days post-injury, compared to those operated in the first 4 days post-injury. A significant negative association was found between Tb.Th (r = -0.54, p < 0.01) and BV/TV (r = -0.39, p < 0.05) in relation to time post-injury in the injured limb. Both BV/TV and Tb.Th were negatively associated with expression of key molecular markers of bone resorption, CTSK, ACP5, and the ratio of RANKL:OPG mRNA. These structure/gene expression relationships did not exist in the contralateral tibial plateau of these patients. This study demonstrated that there is a significant early time-dependent bone loss in the proximal tibia after TPF. This bone loss was significantly associated with altered expression of genes typically involved in the process of osteoclastic bone resorption but possibly also bone resorption by osteocytes. The mechanism of early bone loss in such fractures should be a subject of further investigation. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2865-2875, 2018.