Relaxation Rate Research Articles

In Situ Spin Polarization Measurement Method and Identification of Optimal Spin Polarization Range in Atomic Magnetometer

AbstractIn this study, an in situ measurement method of spin polarization in single‐beam atomic magnetometer is presented. Modeling magnetic linewidth by incorporating nonlinear attenuation along the propagation direction of light and employing the output response equation of magnetometers at zero‐field resonance. Utilizing the model for fitting to extract relaxation rate information, the photon absorption cross‐sections at three temperatures are estimated to be , , and , respectively. Further, the spin polarization curves are obtained by introducing the spin polarization equations. Given the diminishing marginal utility resulting from the enhancement of performance through increased spin polarization, long‐term sensitivity is employed to determine optimal spin polarization range. The optimal long‐term sensitivity for four displayed states is (@31.5Hz), while the ultimate minimum sensitivity is 10.7 (@31.5Hz). The optimal spin polarization ranges at three temperatures are 78.9%–87.1%, 82.3%–88.5%, and 84.5%–88.4%, respectively. The measurement method applied to single‐beam magnetometer can be easily extended to multi‐axis vector magnetometer. The determination of optimal spin polarization range is of great significance for the performance and stability of the magnetometer system, improving the sensitivity of magnetic field measurement, and ensuring its widespread application in bio‐magnetic measurement.

Graphene coating-modified LiCoO2 films as high-performance cathode material in quasi-solid-state thin-film lithium batteries

LiCoO2 (LCO) films were successfully prepared using a radio frequency magnetron sputtering method, and the interface between the LCO cathode films and Li1.5Al0.5Ge1.5(PO4)3 (LAGP) solid electrolyte was modified by a graphene (G) buffer layer. The composition and morphology of the thin-film samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The LCO thin film annealed at 600 °C had excellent charge transport properties, respectively delivering initial charge and discharge specific capacities of 162.7 mAh·g−1 and 124.5 mAh·g−1 at 0.1C in a half-cell structure. Relaxation time distribution reconstruction impedance analysis and rate characteristic analysis of an LCO/G/LAGP/G/LCO symmetric cell demonstrated that the flexible graphene buffer layer effectively improved the contact impedance of the interface and structure stability of the active materials. After cycling for 1000 h at current densities of 0.02 mA·cm−2 and 0.5 mA·cm−2, the LCO/G/LAGP/G/LCO symmetric cell still maintained stable polarization voltages of 0.05 V and 0.7 V, respectively. In addition, an assembled LCO/G/LAGP/Li quasi-solid-state film lithium battery presented an initial discharge specific capacity of 109.53 mAh·g−1 at 0.1C, with a capacity retention rate of 71.86 % after 100 cycles.

Effects of Gadolinium Retention in the Brains of Type 2 Diabetic Rats after Repeated Administration of Gadolinium-Based MRI Contrast Agents on Neurobiology and NLRP3 Inflammasome Activation.

The neurotoxic potential of gadolinium (Gd)-based contrast agents (GBCAs) retention in the brains of patients with type 2 diabetes mellitus (T2DM) is unclear. To determine the deposition and clearance of GBCAs in T2DM rats and the mechanism by which Gd enhances nucleotide-binding oligomerization domain-3 (NLRP3) inflammasome activation. Cross-sectional, prospective. 104 T2DM male Wistar rats. 9.4-T, T1-weighted fast spin echo sequence. T2DM (male Wistar rats, n = 52) and control group (healthy, male Wistar rats, n = 52) rats received saline, gadodiamide, Gd-diethylenetriaminepentaacetic acid, and gadoterate meglumine for four consecutive days per week for 7 weeks. The distribution and clearance of Gd in the certain brain were assessed by MRI (T1 signal intensity and relaxation rate R1, on the last day of each week), inductively coupled plasma mass-spectroscopy, ultraperformance liquid chromatography mass spectrometry, and transmission electron microscopy. Behavioral tests, histopathological features, and the effects of GBCAs on neuroinflammation were also analyzed. One-way analysis of variance, bonferroni method, and unpaired t-test. A P-value <0.05 was considered statistically significant. The movement distance and appearance time in the open field test of the T2DM rats in the gadodiamide group were significantly shorter than in the other groups. Furthermore, the expression of NLRP3, Pro-Caspase-1, interleukin-1β (IL-1β), and apoptosis-associated speck-like protein containing a CARD protein in neurons was significantly higher in the gadodiamide group than in the saline group, as shown by Western blot. Gadodiamide also induced differentiation of microglia into M1 type, decreased the neuronal mitochondrial membrane potential, and significantly increased neuronal apoptosis from flow cytometry. T2DM may affect both the deposition and clearance of GBCAs in the brain. Informed by the T2DM model, gadodiamide could mediate the neuroinflammatory response by NLRP3 inflammasome activation. 1 TECHNICAL EFFICACY: Stage 1.

Numerical and experimental evaluation of a variable-stiffness wedge anchorage for basalt-fiber-reinforced polymer tendons

The small-sized variable-stiffness wedge (VSW) anchorage, a second-generation solution, was numerically optimized to anchor basalt-fiber-reinforced polymer tendons, building upon the previous first-generation anchorage. The static, fatigue, and relaxation characteristics of the anchorage were experimentally evaluated. Results revealed that VSWs effectively mitigated radial stress concentration within the tendons compared to constant stiffness wedges. Bonding optimization techniques involving cross-splitting and sandblasting proved advantageous in accurately assessing the tensile properties of round tendons. The second-generation anchorage demonstrated an 87% anchoring efficiency, surpassing that of a longer commercial steel-wedge anchorage significantly. The tendon-anchorage assembly can sustain 2 million cyclic loadings under a maximum fatigue stress of 0.44 ffpk (standard value for tendon tensile strength) and a stress range of 0.04 ffpk; moreover, sliding between wedges and tendons resulted in negligible stress reduction across various stress ranges. A logarithmic function effectively modeled the relationship between relaxation time and load retention in tendons with R-squared values consistently above 0.94 throughout; furthermore, the million-hour relaxation rate closely aligned with observed tendon behavior. The application of an initial tensile stress of 0.5 ffpk to tendons allowed for simultaneous high strength and minimal prestress loss.

Carbon-detected deuterium solid-state NMR rotating frame relaxation measurements for protein methyl groups under magic angle spinning

Deuterium rotating frame solid-state NMR relaxation measurements (2H R1ρ) are important tools in quantitative studies of molecular dynamics. We demonstrate how 2H to 13C cross-polarization (CP) approaches under 10–40 kHz magic angle spinning rates can be combined with the 2H R1ρ blocks to allow for extension of deuterium rotating frame relaxation studies to methyl groups in biomolecules. This extension permits detection on the 13C nuclei and, hence, for the achievement of site-specific resolution. The measurements are demonstrated using a nine-residue low complexity peptide with the sequence GGKGMGFGL, in which a single selective −13CD3 label is placed at the methionine residue. Carbon-detected measurements are compared with the deuterium direct-detection results, which allows for fine-tuning of experimental approaches. In particular, we show how the adiabatic respiration CP scheme and the double adiabatic sweep on the 2H and 13C channels can be combined with the 2H R1ρ relaxation rates measurement. Off-resonance 2H R1ρ measurements are investigated in addition to the on-resonance condition, as they extent the range of effective spin-locking field.

Measuring Protein-Ligand Binding by Hyperpolarized Ultrafast NMR.

Protein-ligand interactions can be detected by observing changes in the transverse relaxation rates of the ligand upon binding. The ultrafast NMR technique, which correlates the chemical shift with the transverse relaxation rate, allows for the simultaneous acquisition of R2 for carbon spins at different positions. In combination with dissolution dynamic nuclear polarization (D-DNP), where the signal intensity is enhanced by thousands of times, the R2 values of several carbon signals from unlabeled benzylamine are observable within a single scan. The hyperpolarized ultrafast chemical shift-R2 correlated experiment separates chemical shift encoding from the readout phase in the NMR pulse sequence, which allows it to beat the fundamental limit on the spectral resolution otherwise imposed by the sampling theorem. Applications enabled by the ability to measure multiple relaxation rates in a single scan include the study of structural properties of protein-ligand interactions.

Multivariate Machine Learning Models of Nanoscale Porosity from Ultrafast NMR Relaxometry.

Nanoporous materials are of great interest in many applications, such as catalysis, separation, and energy storage. The performance of these materials is closely related to their pore sizes, which are inefficient to determine through the conventional measurement of gas adsorption isotherms. Nuclear magnetic resonance (NMR) relaxometry has emerged as a technique highly sensitive to porosity in such materials. Nonetheless, streamlined methods to estimate pore size from NMR relaxometry remain elusive. Previous attempts have been hindered by inverting a time domain signal to relaxation rate distribution, and dealing with resulting parameters that vary in number, location, and magnitude. Here we invoke well-established machine learning techniques to directly correlate time domain signals to BET surface areas for a set of metal-organic frameworks (MOFs) imbibed with solvent at varied concentrations. We employ this series of MOFs to establish a correlation between NMR signal and surface area via partial least squares (PLS), following screening with principal component analysis, and apply the PLS model to predict surface area of various nanoporous materials. This approach offers a high-throughput, non-destructive way to assess porosity in c.a. one minute. We anticipate this work will contribute to the development of new materials with optimized pore sizes for various applications.

Multivariate Machine Learning Models of Nanoscale Porosity from Ultrafast NMR Relaxometry

AbstractNanoporous materials are of great interest in many applications, such as catalysis, separation, and energy storage. The performance of these materials is closely related to their pore sizes, which are inefficient to determine through the conventional measurement of gas adsorption isotherms. Nuclear magnetic resonance (NMR) relaxometry has emerged as a technique highly sensitive to porosity in such materials. Nonetheless, streamlined methods to estimate pore size from NMR relaxometry remain elusive. Previous attempts have been hindered by inverting a time domain signal to relaxation rate distribution, and dealing with resulting parameters that vary in number, location, and magnitude. Here we invoke well‐established machine learning techniques to directly correlate time domain signals to BET surface areas for a set of metal‐organic frameworks (MOFs) imbibed with solvent at varied concentrations. We employ this series of MOFs to establish a correlation between NMR signal and surface area via partial least squares (PLS), following screening with principal component analysis, and apply the PLS model to predict surface area of various nanoporous materials. This approach offers a high‐throughput, non‐destructive way to assess porosity in c.a. one minute. We anticipate this work will contribute to the development of new materials with optimized pore sizes for various applications.

Electron–ion temperature relaxation in nonideal plasmas: High accuracy classical molecular dynamics simulations

AbstractIn this work, we prepare a simulation framework for a high‐accuracy numerical study of electron–ion temperature relaxation in nonideal (strongly coupled) plasmas. The existing relaxation rate theories require either parameter selection or some pre‐knowledge of the electron–ion correlation functions and effective interaction potentials. This makes non‐equilibrium classical and quantum molecular dynamics simulations a crucial stage in the study of energy transfer rates. We begin by revisiting the classical molecular dynamics simulations of a system of equally charged particles with different masses on a neutralizing background. We accurately simulate this simple ab‐initio (parameterless) system with controlled precision in terms of number of particles, mass ratio, and energy convergence. The predictions for the equally charged system are compared to the previous simulations and theories, which are reproduced with higher accuracy. We also perform a series of classical molecular dynamics simulations of the system of oppositely charged particles with the corrected Kelbg potential based on the quantum statistical approach. We analyze the differences and similarities between the same‐charge and opposite‐charge systems. Some remarks about the forthcoming application of quantum simulations with the help of WPMD or WPMD‐DFT methods are given.

Dynamics of eugenol included in β-cyclodextrin by nuclear magnetic resonance and molecular simulations.

Eugenol-β-cyclodextrin complex has been widely used because of the enhanced stability and conservation of the properties of eugenol. Applications in food and health sciences have been shown previously, which makes this complex an excellent model to understand and develop methodologies for the analysis and prediction of physical properties. In this work, the dynamics of eugenol incorporated into β-cyclodextrin are presented, using NMR relaxation rates, and the predictive capabilities of molecular dynamics simulations are discussed. Results show a hindered rotation of eugenol around the principal inertial axes when located inside β-cyclodextrin. Moreover, a translational movement of the whole complex is demonstrated.

Computing the frequency-dependent NMR relaxation of 1H nuclei in liquid water.

We present a computational framework for reliably determining the frequency-dependent intermolecular and intramolecular nuclear magnetic resonance (NMR) dipole-dipole relaxation rates of spin 1/2 nuclei from Molecular Dynamics (MD) simulations. This approach avoids the alterations caused by the well-known finite-size effects of translational diffusion. Moreover, a procedure is derived to control and correct for effects caused by fixed distance-sampling cutoffs and periodic boundary conditions. By construction, this approach is capable of accurately predicting the correct low-frequency scaling behavior of the intermolecular NMR dipole-dipole relaxation rate and thus allows for the reliable calculation of the frequency-dependent relaxation rate over many orders of magnitude. Our approach is based on the utilization of the theory of Hwang and Freed for the intermolecular dipole-dipole correlation function and its corresponding spectral density [L.-P. Hwang and J. H. Freed, J. Chem. Phys. 63, 4017-4025 (1975)] and its combination with data from MD simulations. The deviations from the Hwang and Freed theory caused by periodic boundary conditions and sampling distance cutoffs are quantified by means of random walker Monte Carlo simulations. An expression based on the Hwang and Freed theory is also suggested for correcting those effects. As a proof of principle, our approach is demonstrated by computing the frequency-dependent intermolecular and intramolecular dipolar NMR relaxation rates of 1H nuclei in liquid water at 273 and 298K based on the simulations of the TIP4P/2005 model. Our calculations are suggesting that the intermolecular contribution to the 1H NMR relaxation rate of the TIP4P/2005 model in the extreme narrowing limit has previously been substantially underestimated.

Halobenzene Adducts of a Dysprosocenium Single-Molecule Magnet.

Dysprosium complexes with strong axial crystal fields are promising candidates for single-molecule magnets (SMMs), which could be used for high-density data storage. Isolated dysprosocenium cations, [Dy(CpR)2]+ (CpR = substituted cyclopentadienyl), have recently shown magnetic hysteresis (a memory effect) above the temperature of liquid nitrogen. Synthetic efforts have focused on reducing strong transverse ligand fields in these systems as they are known to enhance magnetic relaxation by spin-phonon mechanisms. Here we show that equatorial coordination of the halobenzenes PhX (X = F, Cl, Br) and o-C6H4F2 to the cation of a recently reported dysprosocenium complex [Dy(Cpttt)(Cp*)][Al{OC(CF3)3}4] (Cpttt = C5H2tBu3-1,2,4; Cp* = C5Me5) reduces magnetic hysteresis temperatures compared to that of the parent cation. We find that this is due to increased effectiveness of both one- (Orbach) and two-phonon (Raman) relaxation mechanisms, which correlate with the electronegativity and number of interactions with the halide despite κ1-coordination of a single halobenzene having a minimal effect on the metrical parameters of [Dy(Cpttt)(Cp*)(PhX-κ1-X)]+ cations vs the isolated [Dy(Cpttt)(Cp*)]+ cation. We observe unusual divergent behavior of relaxation rates at low temperatures in [Dy(Cpttt)(Cp*)(PhX)][Al{OC(CF3)3}4], which we attribute to a phonon bottleneck effect. We find that, despite the transverse fields introduced by the monohalobenzenes in these cations, the interactions are sufficiently weak that the effective barriers to magnetization reversal remain above 1000 cm-1, being only ca. 100 cm-1 lower than for the parent complex, [Dy(Cpttt)(Cp*)][Al{OC(CF3)3}4].

The effects of biological crowders on fibrillization, structure, diffusion, and conformational dynamics of α-synuclein.

α-synuclein is an intrinsically disordered protein (IDP) whose aggregation in presynaptic neuronal cells is a pathological hallmark of Lewy body formation and Parkinson's disease. This aggregation process is likely affected by the crowded macromolecular cellular environment. In this study, α-synuclein was studied in the presence of both a synthetic crowder, Ficoll70, and a biological crowder composed of lysed cells that better mimics the biocomplexity of the cellular environment. 15 N-1 H HSQC NMR results show similar α-synuclein chemical shifts in non-crowded and all crowded conditions implying that it remains similarly unstructured in all conditions. Nevertheless, both HSQC NMR and fluorescence measurements indicate that, only in the cell lysate, α-synuclein forms aggregates over a timescale of 48 h. 15 N-edited diffusion measurements indicate that all crowders slow down the α-synuclein's diffusivity. Interestingly, at high concentrations, α-synuclein diffuses faster in cell lysate than in Ficoll70, possibly due to additional soft (e.g., electrostatic or hydrophobic) interactions. 15 N-edited relaxation measurements show that some residues are more mobile in cell lysate than in Ficoll70; the rates that are most different are predominantly in hydrophobic residues. We thus examined cell lysates with reduced hydrophobicity and found slower dynamics (higher relaxation rates) in several α-synuclein residues. Taken together, these experiments suggest that while cell lysate does not substantially affect α-synuclein structure (HSQC spectra), it does affect chain dynamics and translational diffusion, and strongly affects aggregation over a timescale of days, in a manner that is different from either no crowder or an artificial crowder: soft hydrophobic interactions are implicated.

Flux creep regimes and vortex phase diagram in β-FeSe single crystals

We analyze the relationship between critical current densities (JC) and flux creep rates (S) in β-FeSe single crystals. This analysis was based on magnetization measurements. Additionally, we establish correlations with the recently reported magnetic field-induced geometrical deformation of the vortex lattice, transitioning from hexagonal to square shape due to a rhombic distortion [A. V. Putilov et al. Phys. Rev 99 (2019) 144514]. The results show that the magnetic field dependence of Jc displays distinct regimes, which is reflected by changes in S. The vortex dynamics is analyzed within the framework of the collective creep theory. S is characterized by low pinning energies and glassy exponents according to the expectation for small-bundles at low temperatures and magnetic fields where a hexagonal vortex lattice was reported. Conversely, we observe a systematic increase in S, resembling a shift from small to large vortex bundles, at magnetic fields corresponding to the rhombic distortion. Last, the relaxation rates exhibit significant values for magnetic fields where a square vortex lattice is expected, suggesting a potential crossover from elastic to plastic creep. Our findings highlight a direct relationship between vortex lattice deformations and a decrease in vortex pinning related to vortex-defect interactions.

Evaluation of Fused Deposition Modeling Materials for 3D-Printed Container of Dosimetric Polymer Gel.

Accurate dosimetric verification is becoming increasingly important in radiotherapy. Although polymer gel dosimetry may be useful for verifying complex 3D dose distributions, it has limitations for clinical application due to its strong reactivity with oxygen and other contaminants. Therefore, it is important that the material of the gel storage container blocks reaction with external contaminants. In this study, we tested the effect of air and the chemical permeability of various polymer-based 3D printing materials that can be used as gel containers. A methacrylic acid, gelatin, and tetrakis (hydroxymethyl) phosphonium chloride gel was used. Five types of printing materials that can be applied to the fused deposition modeling (FDM)-type 3D printer were compared: acrylonitrile butadiene styrene (ABS), co-polyester (CPE), polycarbonate (PC), polylactic acid (PLA), and polypropylene (PP) (reference: glass vial). The map of R2 (1/T2) relaxation rates for each material, obtained from magnetic resonance imaging scans, was analyzed. Additionally, response histograms and dose calibration curves from the R2 map were evaluated. The R2 distribution showed that CPE had sharper boundaries than the other materials, and the profile gradient of CPE was also closest to the reference vial. Histograms and dose calibration showed that CPE provided the most homogeneous and the highest relative response of 83.5%, with 8.6% root mean square error, compared with the reference vial. These results indicate that CPE is a reasonable material for the FDM-type 3D printing gel container.

Enhanced cascaded lattice Boltzmann model for multiphase flow simulations at large density ratio

In recent years, the pseudopotential multiphase lattice Boltzmann method (LBM) has been widely applied in the numerical simulations of complex multiphase flow. However, numerical stability at high Weber (We) and Reynolds (Re) numbers seriously restricts its application. In the present work, the pseudopotential multiphase LBM is developed by introducing the entropic stabilizers to the cascaded collision operator, and thus, the numerical stability is effectively enhanced. The relaxation rates for different order moments are all determined by fluid viscosities and the maximum entropy condition instead of being user-defined. Furthermore, the surface tension and contact angle can be adjusted in a wide range, which extends the application of the pseudopotential multiphase model. The accuracy and capability of the present model to simulate the complex multiphase flow are validated by reproducing the droplet impact on the flat or textured superhydrophobic surfaces. In addition, a droplet impact on the superhydrophobic surface at We=1280 and Re=18000 is simulated, in which the Weber and Reynolds numbers have significantly increased. This strongly demonstrates that the present model can enhance the numerical stability in the simulation of large density ratio multiphase flows at simultaneously high Weber and Reynolds numbers, which means the present model can further extend the pseudopotential multiphase LBM to more realistic scientific and technical applications.

From Milliseconds to Minutes: Melittin Self-Assembly from Concerted Non-Equilibrium Pressure-Jump and Equilibrium Relaxation Nuclear Magnetic Resonance.

Non-equilibrium kinetics techniques like pressure-jump nuclear magnetic resonance (NMR) are powerful in tracking changes in oligomeric populations and are not limited by relaxation rates for the time scales of exchange that can be probed. However, these techniques are less sensitive to minor, transient populations than are Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion experiments. We integrated non-equilibrium pressure-jump and equilibrium CPMG relaxation dispersion data to fully map the kinetic landscape of melittin tetramerization. While monomeric peptides weakly form dimers (Kd,D/M ≈ 26 mM) whose population never exceeds 1.6% at 288 K, dimers associate tightly to form stable tetrameric species (Kd,T/D ≈ 740 nM). Exchange between the monomer and dimer, along with exchange between the dimer and tetramer, occurs on the millisecond time scale. The NMR approach developed herein can be readily applied to studying the folding and misfolding of a wide range of oligomeric assemblies.

Synthesis and characterization of copper (I) particles as contrast agents in magnetic resonance imaging

Recent studies have focused on the link between metals and neurodegenerative diseases like multiple sclerosis (MS), particularly emphasizing the role of copper (Cu). Essential for vital functions, Cu imbalances can contribute to MS-related neurodegeneration and cerebral lesions. Interestingly, Cu accumulation could be a potential biomarker in magnetic resonance image (MRI) for MS. This study aimed to obtain copper(I) oxide nanoparticles (Cu2O-NPs) and evaluate their effectiveness in MRI as contrast agents or MS biomarkers. These nanoparticles were synthesized using the sol-gel method and analyzed via X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). MRI images were obtained introducing Cu2O-NPs into a cranial phantom at various concentrations and inversion times. Results showed that changes in MRI signal and longitudinal relaxation rate (T1) are associated with nanoparticle concentration, highlighting the potential of Cu2O-NPs in MRI applications for MS.

Superfluorinated, Highly Water-Soluble Polyphosphazenes as Potential 19F Magnetic Resonance Imaging (MRI) Contrast Agents.

"Hot spot" 19F magnetic resonance imaging (MRI) has garnered significant attention recently for its ability to image various disease markers quantitatively. Unlike conventional gadolinium-based MRI contrast agents, which rely on proton signal modulation, 19F-MRI's direct detection has a unique advantage in vivo, as the human body exhibits a negligible background 19F-signal. However, existing perfluorocarbon (PFC) or PFC-based contrast materials suffer from several limitations, including low longitudinal relaxation rates and relatively low imaging efficiency. Hence, we designed a macromolecular contrast agent featuring a high number of magnetically equivalent 19F-nuclei in a single macromolecule, adequate fluorine nucleus mobility, and excellent water solubility. This design utilizes superfluorinated polyphosphazene (PPz) polymers as the 19F-source; these are modified with sodium mercaptoethanesulfonate (MESNa) to achieve water solubility exceeding 360 mg/mL, which is a similar solubility to that of sodium chloride. We observed substantial signal enhancement in MRI with these novel macromolecular carriers compared to non-enhanced surroundings and aqueous trifluoroacetic acid (TFA) used as a positive control. In conclusion, these novel water-soluble macromolecular carriers represent a promising platform for future MRI contrast agents.

Ablation of skeletal muscle estrogen receptor alpha impairs contractility in male mice.

Estradiol and estrogen receptor α (ERα) have been shown to be important for the maintenance of skeletal muscle strength in females; however, little is known about the roles of estradiol and ERα in male muscle. The purpose of this study was to determine if skeletal muscle ERα is required for optimal contractility in male mice. We hypothesize that reduced ERα in skeletal muscle impairs contractility in male mice. Skeletal muscle-specific knockout (skmERαKO) male mice exhibited reduced strength across multiple muscles and several contractile parameters related to force generation and kinetics compared with wild-type littermates (skmERαWT). Isolated EDL muscle-specific isometric tetanic force, peak twitch force, peak concentric and peak eccentric forces, as well as the maximal rates of force development and relaxation were 11%-21% lower in skmERαKO compared with skmERαWT mice. In contrast, isolated soleus muscles from skmERαKO mice were not affected. In vivo peak torque of the anterior crural muscles was 20% lower in skmERαKO compared with skmERαWT mice. Muscle masses, contractile protein contents, fiber types, phosphorylation of the myosin regulatory light chain, and caffeine-elicited force did not differ between muscles of skmERαKO and skmERαWT mice, suggesting that strength deficits were not due to size, composition, or calcium release components of muscle contraction. These results indicate that in male mice, reduced skeletal muscle ERα blunts contractility to a magnitude similar to that previously reported in females; however, the mechanism may be sexually dimorphic.NEW & NOTEWORTHY We comprehensively measured in vitro and in vivo contractility of leg muscles with reduced estrogen receptor α (ERα) in male mice and reported that force generation and contraction kinetics are impaired. In contrast to findings in females, phosphorylation of myosin regulatory light chain cannot account for low force production in male skeletal muscle ERα knockout mice. These results indicate that ERα is required for optimal contractility in males and females but via sexually dimorphic means.