Changes In Torsion Angles Research Articles

Clinical insights into tooth extraction via torsion method: a biomechanical analysis of the tooth-periodontal ligament complex.

Traditionally, extracting single, flat- or curved-rooted teeth through twisting is unfeasible. However, our clinical practice suggests that such teeth can be extracted efficiently through moderate twisting in a minimally invasive manner. Given the lack of studies on biomechanics of the tooth-periodontal ligament (PDL) complex during torsion, which has further constrained its application, we assessed the feasibility of the torsion method for extracting single-rooted teeth and evaluated its minimally invasive potential. Using three-dimensional finite element analysis, we examined the stress distribution of the tooth and PDL during torsion. Then, we examined changes in the optimal torsion angle (OTA) and stress distribution across various anatomical scenarios. During torsion loading, stress concentration was primarily observed on the sing-rooted tooth surface near the alveolar crest, whereas molars at the root furcation. The OTA was found to increase under conditions such as narrowing of root width, decrease in the root apical curvature, change from type I to IV bone, alveolar bone loss, and shortening of root length. Moreover, the clinically validated model demonstrated that 74% of outcomes fell within the standard OTA range. In conclusion, the decrease in PDL area necessitated a larger angle for complete PDL tearing. Single-rooted teeth with root width-to-thickness ratios of ≥0.42 and apical curvatures of ≤30°are suitable for extraction using the torsion method. This study confirms the feasibility of the torsion method for minimally invasive tooth extraction and expands its indications, laying the theoretical foundation and essential insights for its clinical application.

Model Prediction and Optimization of Belt Drive System Vibration Suppression Based on Industrial Robot Joints

Addressing the vibration issues caused by torsional angle changes in the belt transmission systems of industrial robots during practical applications, this paper introduces a control strategy that integrates a Model Predictive Control (MPC) compensation mechanism. By applying the Lagrangian method, a dynamic mathematical model correlating torsional angle and torque was established, and an algorithm design combining MPC with its compensatory controller was developed. This strategy was validated in a MATLAB simulation environment. Simulation results demonstrate that, compared to traditional sliding mode control, the newly proposed controller significantly improved response speed in tracking the torsional angle's position and angular velocity, achieving enhancements of approximately 2 seconds and 1 second, respectively. This led to higher tracking accuracy and faster convergence speed, effectively enhancing the vibration suppression performance of industrial robot joint belt transmission systems.

High sensitivity vector torsion sensor based on a single Stress-Applying fiber Sagnac interferometer

A vector torsion sensor based on a Single Stress-Applying Fiber (SSAF) Sagnac interferometer is proposed and experimentally demonstrated. Taking use of the high birefringence and structural asymmetry of the SSAF, the spectrum of SSAF based Sagnac interferometer shows both wavelength shift and intensity variation with the change of torsion angle. A torsion sensitivity as high as 53.3 nm/(rad/m) can be achieved by wavelength demodulation and 4.3 dB/(rad/m) by intensity demodulation. In addition, the torsion direction can be also recognized in the torsion angle range from −50° to 50°. The temperature cross sensitivity is 0.03 rad/m/℃ by wavelength demodulation in the temperature range from 20℃ to 38℃. The advantages of high sensitivity, direction recognition, multi-parameter demodulation and simple structure make the sensor great potential in civil engineering, surgical robot and other applications.

Thermosalient Effect of 5-Fluorobenzoyl-4-(4-methoxyphenyl)ethynyl-1-methylimidazole without Phase Transition

5-Fluorobenzoyl-4-(4-methoxyphenyl)ethynyl-1-methylimidazole 1 exhibited a thermosalient effect without phase transition. The crystal of 1 was jumped by heating to about 80 °C using a hot plate. No phase transition peak was observed at this temperature range according to DSC measurement, unlike renowned thermosalient crystals. Variable-temperature X-ray crystal structure analyses revealed that anisotropical cell constant expansion resulting from the torsion angle change between the imidazole group and carbonyl moiety induced unit cell constant expansion and the thermosalient effect.

Influence of limb positioning during image acquisition on femoral torsion measurements: implications for surgical planning

ABSTRACT Femoral torsion is an important parameter to accurately quantify when planning for the correction of structural pathomorphology. The purpose of this study was to quantify the influence of limb positioning during image acquisition and of alignment techniques on femoral torsion measurements, by measuring the change in femoral torsion angle, upon digital rotations that simulate flexion/extension and adduction/abduction positions of the femur. Femoral torsion measurements were reduced up to 1° and increased up to 0.35° per each degree of flexion and abduction, respectively. The estimation of femoral torsion measurements yielded a difference up to 5.8° between the aligned and non-aligned cases.

N-Acetyl Side-Chain Conformation in Saccharides: Solution Models Obtained from MA'AT Analysis.

MA'AT analysis has been applied to model the conformational properties of N-acetyl side-chains in biologically important GlcNAc and ManNAc monosaccharides and in a βGlcNAc-(1→4)-βGlcNAc disaccharide. Density functional theory calculations were conducted to obtain parameterized equations that relate the magnitudes and signs of 10 spin-coupling constants to conformations of the C2-N2 bonds of GlcNAc and ManNAc. Six of these equations were used with experimental J-couplings, measured in H2O/2H2O and DMSO-d6 solvents in selectively 13C-labeled compounds, to model the C1-C2-N2-C1' torsion angle (θ1) in GlcNAc and ManNAc residues. MA'AT analysis gave mean values of θ1 of 106° for αGlcNAc and ∼116° for βGlcNAc residues, with circular standard deviations (CSDs) of 21-22° in aqueous solution, in excellent agreement with those obtained by aqueous molecular dynamics (MD) simulation. Parameter space plots revealed unique MA'AT fits of the data, and root mean squared deviations (<0.2 Hz) were twofold smaller than those back-calculated from MD models, indicating that the MA'AT models better fit the experimental J-couplings. Context effects on both θ1 values were found to be small in a βGlcNAc-(1→4)-βGlcNAc disaccharide. MA'AT analysis gave a mean value of θ1 of 249° for αManNAc in H2O/2H2O, with a CSD of ∼19°, with both values in good agreement with MD. MA'AT models of N-acetyl side-chains are similar to those obtained previously for O-acetyl side-chains (J. Phys. Chem. B 2017, 121, 66-77). Both O- and N-acetylation conformationally constrain the C-O or C-N bonds relative to the same bonds in unsubstituted compounds. The present work confirms the ability of MA'AT analysis to reveal relatively small changes in mean molecular torsion angles in solution and provides additional evidence of the method as an experimental tool complementary to MD simulation.

Identifying the Molecular Origins of Green BN-TADF Material Degradation and Device Stability via in situ Raman Spectroscopy.

There is little investigation into the impact of molecular conformation on device efficiency and degradation of boron-nitrogen thermally activated delayed fluorescence emitters (BN-TADF). Herein, three highly-efficient green BN-TADF emitters have been designed to unveil the impact of peripheral phenyl groups on device efficiencies and lifetimes. Compared to BN-PhOH with the lowest EQEmax of 19 %, BN-PhOCH3 and BN-PhN(CH3 )2 have achieved strongly enhanced EQEmax of 25.6 % and 24.1 %, respectively. Importantly, the device lifetimes (LT50 ) are dramatically improved from 1.7 h of BN-PhOH to 4.4 h of BN-PhOCH3 and 7.7 h of BN-PhN(CH3 )2 without encapsulation. According to in situ Raman spectroscopy and simulations, BN-PhN(CH3 )2 of less conformation change after aging exhibits the best photostability. It is proposed that the torsion angle change between the BN core and the peripheral phenyl group results in BN-TADF degradation. This knowledge means precisely tuning peripheral groups of BN-TADF can achieve both higher device efficiencies and longer lifetimes.

Analysis of changes in tibial torsion angle on open-wedge high tibial osteotomy depending on the osteotomy level

PurposeThis study evaluated the tibial torsional angle changes of 72 knees before and after open-wedge high tibial osteotomy (OWHTO) and compared the results according to the osteotomy level.Materials and methodsSeventy patients (72 knees) with Kellgren–Lawrence grade 3 underwent OWHTO. Demographic data, operation procedures, and measurement of mechanical tibiofemoral angle (mTFA), anatomical tibiofemoral angle (aTFA), tibial torsional angle (TTA), and pre- and postoperative Lysholm and International Knee Documentation Committee (IKDC) scores were obtained. The authors analyzed TTA changes between 30 knees with high-level osteotomy (group A) and 42 knees with low-level osteotomy (group B).ResultsThe changes of TTAs in the subjects of 72 knees went from 29.26 ± 5.6° preoperative mean to 25.36 ± 6.4° postoperative mean (p = 0.032). The postoperative TTAs of group A (mean 27.4 ± 4.8°) and B (mean 25.7 ± 4.9°) were statistically significant (p < 0.01). Preoperative Lysholm and IKDC scores of 72 knees had means of 49.1 ± 3.5 and 49.0 ± 15.2, respectively, and postoperative means of 85.7 ± 8.56 and 78.0 ± 17.6, respectively, which were statistically significant (p < 0.01).ConclusionsChanges of TTA with internal rotation of distal tibia were observed following OWHTO. High-level osteotomy on the proximal tibia’s lateral cortex had less internal rotation of the distal tibia than low-level osteotomy.

Methyl β-lactoside [methyl β-D-galactopyranosyl-(1→4)-β-D-glucopyranoside] monohydrate: a solvomorphism study.

Methyl β-lactoside [methyl β-D-galactopyranosyl-(1→4)-β-D-glucopyranoside] monohydrate, C13H24O11·H2O, (I), was obtained via spontaneous transformation of methyl β-lactoside methanol solvate, (II), during air-drying. Cremer-Pople puckering parameters indicate that the β-D-Galp (β-D-galactopyranosyl) and β-D-Glcp (β-D-glucopyranosyl) rings in (I) adopt slightly distorted 4C1 chair conformations, with the former distorted towards a boat form (BC1,C4) and the latter towards a twist-boat form (O5SC2). Puckering parameters for (I) and (II) indicate that the conformation of the βGalp ring is slightly more affected than the βGlcp ring by the solvomorphism. Conformations of the terminal O-glycosidic linkages in (I) and (II) are virtually identical, whereas those of the internal O-glycosidic linkage show torsion-angle changes of 6° in both C-O bonds. The exocyclic hydroxymethyl group in the βGalp residue adopts a gt conformation (C4' anti to O6') in both (I) and (II), whereas that in the βGlcp residue adopts a gg (gauche-gauche) conformation (H5 anti to O6) in (II) and a gt (gauche-trans) conformation (C4 anti to O6) in (I). The latter conformational change is critical to the solvomorphism in that it allows water to participate in three hydrogen bonds in (I) as opposed to only two hydrogen bonds in (II), potentially producing a more energetically stable structure for (I) than for (II). Visual inspection of the crystalline lattice of (II) reveals channels in which methanol solvent resides and through which solvent might exchange during solvomorphism. These channels are less apparent in the crystalline lattice of (I).

Modular Synthesis of Tetraurea and Octaurea Macrocycles Encoded with Specific Monomer Sequences

Modular Synthesis of Tetraurea and Octaurea Macrocycles Encoded with Specific Monomer Sequences

Curvature of the Retroviral Capsid Assembly Is Modulated by a Molecular Switch.

During the maturation step, the retroviral capsid proteins (CAs) assemble into polymorphic capsids. Their acute curvature is largely determined by 12 pentamers inserted into the hexameric lattice. However, how the CA switches its conformation to control assembly curvature remains unclear. We report the high-resolution structural model of the Rous sarcoma virus (RSV) CA T = 1 capsid, established by molecular dynamics simulations combining solid-state NMR and prior cryoelectron tomography restraints. Comparing this with our previous model of the RSV CA tubular assembly, we identify the key residues for dictating the incorporation of acute curvatures. These residues undergo large torsion angle changes, resulting in a 34° rotation of the C-terminal domain relative to its N-terminal domain around the flexible interdomain linker, without substantial changes of either the conformation of individual domains or the assembly contact interfaces. This knowledge provides new insights to help decipher the mechanism of the retroviral capsid assembly.

Vibrational and conformational analysis of structural phase transition in Estradiol 17β valerate with temperature

Estradiol 17β valerate (E2V) is a hormonal medicine widely used in hormone replacement therapy. E2V undergoes a reversible isosymmetric structural phase transition at low temperature (̴ 250 K) which results from the reorientation of the valerate chain. The reversible isosymmetric structural phase transition follows Ehrenfest’s classification when described as first-order and Buerger’s classification when classified as order–disorder. The conformational difference also induces changes in molecular torsional angles and on the hydrogen bond pattern. In combination with density functional theory (DFT) calculations, vibrational spectroscopy has been used to correlate the valerate chain modes with the modifications of the dihedral angles on phase transition. We are expecting improvement in our understanding of the phase transition mechanism driven by the temperature. The Conformational analysis reveals the feasible structures corresponding to changes in the dihedral angles associated with the valerate chain. The infrared spectra of calculated conformers are in good agreement with the experimental spectra of E2V structure recorded at room temperature revealing that the changes in valerate chain modes at 1115 cm−1, 1200 cm-1and 1415 cm−1 fingerprint the molecular conformation.An investigation made to determine the ligand–protein interaction of E2V through docking against estrogen receptor (ER) reveals the inhibitive and agonist nature of E2V.

Insights into Structure and Aggregation Behavior of Elastin-like Polypeptide Coacervates: All-Atom Molecular Dynamics Simulations.

The stimuli-responsive character of elastin-like polypeptides (ELP) has led to their use in a wide range of applications. The temperature-triggered aggregation, or LCST behavior, of ELPs is a complex and multistep phenomenon, which proposed to include the structural transitions, loss of hydrophobic hydration, expulsion of water molecules and physical association of chains. Thus, the origin and detailed mechanism of LCST in ELPs is difficult to elucidate. Here, to gain insights into structure and dynamics of coacervates, we performed all-atom molecular dynamics simulations of 27 90-mer ELPs in explicit water at 350 K. Two sequences, poly(VGPVG)18 and poly(VPGVG)18, were examined due to their experimentally observed differences in thermal hysteresis albeit identical overall composition but different arrangement of amino acids. The simulation results indicate that surface hydrophobicity of poly(VGPVG) aggregate is less than that of the poly(VPGVG) aggregate, and there are marked changes in torsion angles and the propensities of secondary structural motifs during the aggregation process. Moreover, there are significant differences between structure of a single polypeptide in water and structure within the aggregate. Overall, the aggregation process is driven by the formation of peptide-peptide interactions whereas the average hydration of peptides remains almost the same between dissolved and aggregated states. Even though the aggregation is driven by the hydrophobic interactions, ELP coacervate has no hydrophobic core and contains many water molecules. Overall, our findings provide an insight into the sequence-dependent structure of coacervates and molecular behavior of individual peptides during aggregation.

Helical Homometallic Trinickel String Complexes with Mixed Hard Nitrogen and Sulfur Donors: Structural and Magnetic Studies

Abstract A new tridentate and rigid ligand containing S,N-hetero donor, the 1H-1,8-naphthyridine-2-thione (Hnpt), is designed and developed to build up the first homonuclear nickel string supported by the mixed-donor ligands. Three asymmetric nickel strings possessing the structural feature of the (4,0) configuration are synthesized, namely the (4,0)-Ni3(npt)4(NCS) (1), (4,0)-[Ni3(npt)4(NCS)](PF6) (2) and (4,0)-Ni3(npt)4(NCS)2 (3). Due to the nature of the naphthyridyl group and sulfur donor, complex 1 is composed of one stabilized mixed-valent unit [Ni2]3+ and one low spin nickel thiolate. 1 and 2 are the quasi-1D coordination polymers in the solid-state, in which the molecules are linked by the weak intermolecular Ni⋯SCN interactions. 2 and 3 possess the same Ni36+ oxidized state with the different donation of axial ligands. The weaker donor in 2 yields the low spin state in the middle Ni(II). The stronger axial donor and the rigidity of ligand in 3 lead to the change of torsion angle, creating the unprecedented high spin Ni(II) inside the nickel string. This high spin Ni(II) with the square planar geometry is an unusual structure and magnetism among nickel strings. Detailed magnetic studies allow us to establish the spin state of each nickel in these three complexes. Besides, three different torsion angles with the same ligand and metal provide us with an opportunity to examine the factors governing the helicity of rigid ligands.

Mapping temperature-dependent conformational change in the voltage-sensing domain of an engineered heat-activated K+ channel

Temperature-dependent regulation of ion channel activity is critical for a variety of physiological processes ranging from immune response to perception of noxious stimuli. Our understanding of the structural mechanisms that underlie temperature sensing remains limited, in part due to the difficulty of combining high-resolution structural analysis with temperature stimulus. Here, we use NMR to compare the temperature-dependent behavior of Shaker potassium channel voltage sensor domain (WT-VSD) to its engineered temperature sensitive (TS-VSD) variant. Further insight into the molecular basis for temperature-dependent behavior is obtained by analyzing the experimental results together with molecular dynamics simulations. Our studies reveal that the overall secondary structure of the engineered TS-VSD is identical to the wild-type channels except for local changes in backbone torsion angles near the site of substitution (V369S and F370S). Remarkably however, these structural differences result in increased hydration of the voltage-sensing arginines and the S4-S5 linker helix in the TS-VSD at higher temperatures, in contrast to the WT-VSD. These findings highlight how subtle differences in the primary structure can result in large-scale changes in solvation and thereby confer increased temperature-dependent activity beyond that predicted by linear summation of solvation energies of individual substituents.

Modulation of trithiophene-based chalcone positional isomers by twist angle variation: Ultrafast nonlinear optical properties and excited-state dynamics

The nonlinearities involves the interaction between multiple sources, to minimize variable factors, four trithiophene chalcone isomeric molecules were designed and synthesized to investigate the modulation of torsion angle changes (6°, 25°, 37°, 60°) on optical nonlinearities. The electronic excitation properties and relevant parameters were calculated through quantum chemical methods. Femtosecond Z-scan measurements showed that the four molecules exhibited configuration-dependent reverse saturation absorption (RSA) at 600 and 700 nm and had ≥1 figure of merit (F) at 700 nm. Combined with the orbital delocalization index, the results indicated that the spatial delocalization of electrons is gradually suppressed with system twisting. Transient absorption spectra revealed a transition from the locally excited (LE) state to the charge transfer (CT) state, and the planarized structure promotes the relaxation of excited particles. This study suggest that these novel trithiophene derivatives possess potential in nonlinear optical applications and provide an approach for the optimization of nonlinear functional isomeric materials.

Understanding Ring Puckering in Small Molecules and Cyclic Peptides.

The geometry of a molecule plays a significant role in determining its physical and chemical properties. Despite its importance, there are relatively few studies on ring puckering and conformations, often focused on small cycloalkanes, 5- and 6-membered carbohydrate rings, and specific macrocycle families. We lack a general understanding of the puckering preferences of medium-sized rings and macrocycles. To address this, we provide an extensive conformational analysis of a diverse set of rings. We used Cremer–Pople puckering coordinates to study the trends of the ring conformation across a set of 140 000 diverse small molecules, including small rings, macrocycles, and cyclic peptides. By standardizing using key atoms, we show that the ring conformations can be classified into relatively few conformational clusters, based on their canonical forms. The number of such canonical clusters increases slowly with ring size. Ring puckering motions, especially pseudo-rotations, are generally restricted and differ between clusters. More importantly, we propose models to map puckering preferences to torsion space, which allows us to understand the inter-related changes in torsion angles during pseudo-rotation and other puckering motions. Beyond ring puckers, our models also explain the change in substituent orientation upon puckering. We also present a novel knowledge-based sampling method using the puckering preferences and coupled substituent motion to generate ring conformations efficiently. In summary, this work provides an improved understanding of general ring puckering preferences, which will in turn accelerate the identification of low-energy ring conformations for applications from polymeric materials to drug binding.

Dynamics of relative torsional vibrations in the formation of a regular microrelief on internal cylindrical surfaces

The article presents the results of analysis of modern literature sources in search of mathematical models describing the dynamics of the process of forming regular microrelief on the inner cylindrical surfaces of parts operating in difficult conditions, in order to increase their life cycle. The absence of mathematical models describing this process and the peculiarities of its implementation with the point action of the deforming element on the surface of the body part are established. The movements of the tool during the process of forming a regular microrelief on the inner cylindrical surface of the body of the part are considered and the driving forces that follow this process are analyzed. Based on the results of the analysis, a mathematical model of the dynamic process of forming regular microrelief on the inner cylindrical surface of the body of the part was developed. The peculiarity of this process is that microrelief is formed by concentrated force, the point of application of which is constantly changing in the radial and axial directions relative to the part. Therefore, the mathematical model that describes this process will have a discrete right-hand side. It is proposed to model such an action using Dirac delta functions with linear and temporal variables, using the method of regularization of these features, in particular, existing methods of integrating the corresponding nonlinear mathematical models of torsional vibrations of a part. Analytical relations describing these vibrations in the process of forming a regular microrelief are obtained. Using Maple software 3D changes in torsion angle depending on different values of the source data are constructed. The conducted research will allow to consider torsional oscillations that is crucial for long cylindrical details, such as sleeves of hydraulic cylinders, parts of drilling mechanisms and others.

Effect of twisting deformation on electronic structure and optical properties of gold-doped black phosphorene

The first-principles method based on density functional theory is used to study the effect of torsion deformation on the electronic structure and optical properties of gold-doped black phosphorene. The results show that the electronic structure of the gold-doped black phosphorene system is more sensitive to torsion deformation than that of the intrinsic black phosphorene system under torsion. The analysis of the energy band structure indicates that intrinsic black phosphorene is a direct band gap semiconductor. After being doped with gold, it can realize its transformation from semiconductor into metal. After the gold-doped black phosphorene system is twisted by 1°, the band gap is opened and becomes an indirect band gap semiconductor. As the torsion angle increases, the band gap of the intrinsic black phosphorene system increases slowly, while the band gap of the gold-doped black phosphorene system first decreases, then increases, and then decreases. From the analysis of the density of states, it is found that when the torsion angle changes from 0° to 5°, the intrinsic black phosphorene system has a strong sp orbital hybridization. The s orbit and p orbit contribute to the conduction band and the valence band, but the p orbit is better than the s orbit. The contribution to the total density of states is more, and the s orbital, p orbital and d orbital of the gold-doped black phosphorene system all contribute to the total density of states. From the analysis of optical properties, it is found that compared with the intrinsic black phosphorene system with a torsion angle of 0°, the intrinsic black phosphorene twisted system exhibits a blue shift at the absorption peak and reflection peak, and the gold-doped black phosphorene twisted system exhibits a blue shift in both absorption peak and reflection peak. Both the absorption peak and the reflection peak are red-shifted.

Hypervariability of accessible and inaccessible conformational space of proteins.

Proteins undergo motions in a range of amplitudes, from domain motions to backbone rotations, leading to changes in (φ,ψ) torsion angles and small-scale bond vibrations and angle bending. Here, we study the extent of variations in (φ,ψ) values in proteins and the effects of bond geometry variations due to vibrational motions in a protein on the accessible, (steric clash-free) (φ,ψ) space. We perform 1-fs timestep unconstrained molecular dynamics simulations on super-high-resolution protein structures. Extent of variations in bond geometry during the simulation is within acceptable ranges of bond lengths and angles. However, the steric clash-free (φ,ψ) space continuously changes as seen in bond geometry-specific (φ,ψ) steric maps at the residue level during simulations. (φ,ψ) regions that have steric clash at one timepoint can become steric clash-free at a different timepoint through minor adjustments to backbone bond lengths and angles. Also instances of (φ,ψ) transitions from the left to right half of the (φ,ψ) map in consecutive snapshots of the trajectory are seen. Although the two quadrants are separated by a steric clash-prone region, corresponding to a high-energy barrier, height of this barrier is lowered by adjusting the bond geometry such that a bridging region of steric clash-free, low-energy (φ,ψ) values is formed. We demonstrate the idea of dynamically varying nature of acceptable and accessible (φ,ψ) steric space in proteins, which has implications for protein folding; proteins could sample (φ,ψ) space which is originally considered to be inaccessible, during folding, through minor adjustments to their backbone bond geometry.