Direction Of Pulling Research Articles

Conductance and assembly of quasi-1D coordination chain molecular junctions with triazole derivatives.

Incorporating transition metal atoms into metal-molecule-metal junctions presents opportunities for exploring the electronic properties of coordination complexes, organometallics and metal-organic materials on the single molecule level. Recent single molecule conductance studies have shown that in situ incorporation of electrode metal atoms into coordination chains formed in the junction can occur with deprotonated, negatively charged organic ligands, such as the imidazolate (Im-) anion. However, the mechanism and chemical principles, such as the role of the charge state of the ligand, for the construction of such coordination chains are still debated. Here, we probe the role of the ligand charge state and electronic structure in single-molecule conductance and formation of metal-molecule coordination chains. We perform break junction measurements with triazole isomers, which can bridge junctions both in their neutral and charged forms, and find that prior deprotonation of the ligands is not required for coordination complex assembly, but can affect the molecular conductance and junction formation probability. Our results indicate that coordination chains can form with neutral ligands, as long as the electron density in the frontier MOs is concentrated at the binding sites and along the direction of pulling, promoting ligand binding and incorporation of gold atoms into the junction during elongation. Our findings may provide insight into design principles for in situ assembled molecular wires with transition metal atoms and open the door to electronic and spintronic studies of such materials.

Edukasi Auto Streching pada Kasus Nyeri Leher pada Siswa SMP Nurul Ilmi Kota Jambi

Neck pain is a complaint that often causes a person to come to a health facility for treatment. Auto stretching is a technique of stretching the muscles with the correct direction of pulling which is done independently with the aim of reducing pain. Based on the data collected, it was found that (80%) junior high school students who had less knowledge and had sufficient knowledge 3 (15%). After conducting counseling on reducing neck pain with auto stretching, there was an increase in the knowledge of junior high school students with a percentage of 5% increasing to 90%. The aim of this counseling to the community is to increase the knowledge of junior high school students about auto stretching in cases of neck pain. Methods Implementation of counseling activities is carried out by lecture and demonstration methods with a total of 20 participants. The material presented about auto stretching in neck pain includes the meaning, causes, pathophysiology of neck pain, as well as understanding, benefits, how to implement auto stretching. In counseling, discussions were also held between the presenters and participants to share experiences related to the theme of neck pain. To find out the participants' understanding of the material presented, an evaluation was held by asking a number of questions. The results of this activity showed an increase in junior high school students' knowledge about auto stretching for neck pain

The Drosophila mitotic spindle orientation machinery requires activation, not just localization

The orientation of the mitotic spindle at metaphase determines the placement of the daughter cells. Spindle orientation in animals typically relies on an evolutionarily conserved biological machine comprised of at least four proteins – called Pins, Gαi, Mud, and Dynein in flies – that exerts a pulling force on astral microtubules and reels the spindle into alignment. The canonical model for spindle orientation holds that the direction of pulling is determined by asymmetric placement of this machinery at the cell cortex. In most cell types, this placement is thought to be mediated by Pins, and a substantial body of literature is therefore devoted to identifying polarized cues that govern localized cortical enrichment of Pins. In this study we revisit the canonical model and find that it is incomplete. Spindle orientation in the Drosophila follicular epithelium and embryonic ectoderm requires not only Pins localization but also direct interaction between Pins and the multifunctional protein Discs large. This requirement can be over‐ridden by interaction with another Pins interacting protein, Inscuteable.

Investigation of the Ordered Structure in Partially Melted Isotactic Polypropylene.

The ordered structure of partially melted isotactic polypropylene (iPP) was investigated using polarized optical microscopy (POM) and small-/wide-angle X-ray scattering (SAXS/WAXS) measurements. The crystalline morphology was first examined by means of pulling a glass fiber through the iPP melt, which was generated by partially melting a preformed spherulite. The results from the POM experiments indicated that, even at a minimal pulling rate, the surviving ordered structure could also relocate along the direction of fiber pulling and grow into cylindrites eventually. In addition, during the quiescent crystallization from the partially melted sample, which had the same thermal history of fiber-pulling experiments, the obvious memory effect of melt was also observed from the results of X-ray experiments. Moreover, the SAXS profile derived from the partially melted iPP at 170 °C was fitted by the theory of scattering amplitude with the cylindrical form factor. The fit result implied that the surviving ordered structure is of cylindrical nanocrystals with a diameter D ≈ 30 ± 3 nm and height h ≈ 45 ± 3 nm, which can significantly influence the crystallization morphology and kinetics during the subsequent crystallization process.

Development of technology for repair of shaped elements of pipeline systems in hard-to-reach places

It is proposed that erosion or corrosion worn out bends of pipeline systems in hard-to-reach places be repaired by trenchless methods by pulling a sleeve or a flexible composite pipe with a piston. The possibility of implementing such an idea is confirmed by theoretical and experimental studies. Mathematical modeling of the process of pulling a sleeve by a piston by a pipeline that contains a defective tap is performed. Formulas are derived for determining all resistance forces acting on a mobile system, patterns of pressure changes at the compressor outlet during such work are determined. A technique has been developed for calculating the friction force between the sleeve and the inner wall of the pipeline at the outlet, due to the pressing of the sleeve through a change in the direction of pulling. The dependence of the required pressure for the piston to extend the sleeve only with a defective bend on the bend angle of the bend is determined. An experimental setup has been developed and built to study the dynamics of the sleeve pulling by a piston. As a result of the experimental tests, it was found that it is possible to extend the sleeve through a pipeline with a piston that contains bend. The resistance forces acting on the moving system, the patterns of pressure change at the beginning of the pipeline in time when the sleeve is pulled by the piston, are experimentally determined. The experimental results are compared with the results of theoretical calculations and the reliability of theoretically derived dependencies is confirmed. The technique and technology for repairing defective pipe bends in hard-to-reach places has been developed by pulling a sleeve or a flexible composite pipe with a piston. The piston moves under the pressure of the air supplied to the piston space by the compressor. A drum with a wound sleeve or flexible composite pipe is placed in a cylindrical sealed chamber. A special supporting device has been developed to place a flexible composite pipe wound into a bay in a cylindrical sealed chamber.

Increasing of the Efficiency of Extraction of Elements from Soil by a Tubular Diesel Hammer

For the extraction of piles, sheet piling, and casings from soil, we propose new decisions for the devices that make it possible to increase the machine time of using diesel hammers due to the extension of the field of their application. The efficient combination of the dynamic action by shock pulses and static extraction forces directed upward in the direction of pulling of elements from the soil makes it possible to use tubular-type diesel hammers not only to deepen but also to extract elements from soils.

Video analysis for the evaluation of vaginal births: a prospective observational study.

Video documentation is nowadays well established in many fields of medicine, but mostly in unreal situations such as simulation training. We here present the application of video for teaching and learning purposes during the birth process. The aim of video documentation during labour is to provide an observational tool for obstetric care by midwives and obstetricians, with the opportunity for evaluation and education afterwards, especially in absence of the woman in labour and her family. Between February 2015 and June 2017, we conducted a prospective observational study on women aged over 18 years with singleton pregnancies with vertex presentation at term, who gave birth vaginally in the labour ward at the Division of Obstetrics of the University Hospital of Zurich. The end of birth (crowning of the head and fetal extraction) with the manual actions and manoeuvers performed was recorded on video in 100 births. Procedures were analysed afterwards by a senior consultant and evaluated with the staff involved. We found frequent notable omissions during vaginal deliveries, concerning technical and nontechnical skills. Those aspects included inappropriate aseptic technique (e.g., no sterile underlay or sterile gloves), improper fetal head slowdown during expulsion, lack of visualisation of the perineum during fetal extraction/expulsion, lack of hip, shoulder and arm guiding while extracting the fetus, inappropriate episiotomy technique (wrong handling of the scissors, cutting angle too steep) and improper communication between the woman giving birth and the staff. During vacuum extractions, incorrect positioning of the cup, and inappropriate direction of pulling and handling of the cup were recorded. Video analysis of obstetric procedures in the labour ward is an easily applicable and very useful tool for teaching and learning purposes. It contributes to showing and improving the quality of procedures and the interactions of the staff and can be used for staff evaluation.

Video analysis for the evaluation of vaginal births: a prospective observational study.

Video documentation is nowadays well established in many fields of medicine, but mostly in unreal situations such as simulation training. We here present the application of video for teaching and learning purposes during the birth process. The aim of video documentation during labour is to provide an observational tool for obstetric care by midwives and obstetricians, with the opportunity for evaluation and education afterwards, especially in absence of the woman in labour and her family. Between February 2015 and June 2017, we conducted a prospective observational study on women aged over 18 years with singleton pregnancies with vertex presentation at term, who gave birth vaginally in the labour ward at the Division of Obstetrics of the University Hospital of Zurich. The end of birth (crowning of the head and fetal extraction) with the manual actions and manoeuvers performed was recorded on video in 100 births. Procedures were analysed afterwards by a senior consultant and evaluated with the staff involved. We found frequent notable omissions during vaginal deliveries, concerning technical and nontechnical skills. Those aspects included inappropriate aseptic technique (e.g., no sterile underlay or sterile gloves), improper fetal head slowdown during expulsion, lack of visualisation of the perineum during fetal extraction/expulsion, lack of hip, shoulder and arm guiding while extracting the fetus, inappropriate episiotomy technique (wrong handling of the scissors, cutting angle too steep) and improper communication between the woman giving birth and the staff. During vacuum extractions, incorrect positioning of the cup, and inappropriate direction of pulling and handling of the cup were recorded. Video analysis of obstetric procedures in the labour ward is an easily applicable and very useful tool for teaching and learning purposes. It contributes to showing and improving the quality of procedures and the interactions of the staff and can be used for staff evaluation.

Curvature‐Induced Sorting of Lipids in Plasma Membrane Tethers

AbstractMembrane curvature controls the spatial organization and activity of cells. Lipid sorting in cell membranes can be explained by matching lipid molecular shape to regions of different curvatures. A molecular view of curvature‐induced lipid sorting is obtained using coarse‐grained molecular dynamics. A model membrane consisting of an asymmetric bilayer of multiple lipid species is simulated. Curvature is induced by pulling a tether, that is, a bilayer nanotube, from a flat membrane. Pulling is performed both from the inner and outer leaflets, corresponding to directions in and out of the cell. Redistribution of different lipid types between the tether and the bilayer is observed, leading to spatial variations in the composition of both leaflets, and, in turn, softening of the tether. Depending on the direction of pulling, the lipid distributions and the tether properties differ. Formation of a tether from the planar membrane thus induces lipid sorting without phase separation.

Relevance of the Speed and Direction of Pulling in Simple Modular Proteins.

A theoretical framework capable of predicting the first unit that unfolds in pulled modular proteins has been recently introduced, for "fast enough" pulling velocities. Within this picture, we investigate the unfolding pathway in a chain of identical units and predict that the module closest to the pulled end opens first. Steered molecular dynamics of a simple construct, specifically a chain composed of two coiled-coil motives, shows that this is indeed the case. Notwithstanding, the unfolding behavior strongly depends on the terminus (C or N) from which this homopolyprotein is pulled. Therefore, anisotropic features are revealed and seem to play an important role for the observed unfolding pathway.

Direction-dependent force-induced dissociation dynamics of an entropic-driven lock-and-key assembly.

The unbinding dynamics of a nanosized sphere-and-cavity assembly under the pulling of constant force and constant loading rate is explored by dissipative particle dynamics simulations. The formation of this matched lock-and-key pair in a polymer solution is driven by the depletion attraction. The two-dimensional free energy landscape U(x,z) associated with this assembly is constructed. Our results indicate that the unbinding pathway along the orientation of the assembly is unfavorable due to the relatively high energy barrier compared to that along the tortuous minimum path whose energy barrier is not high. It is also found that the dissociation rate depends on the direction of the external force (θ) with respect to the assembly orientation. The presence of the force component perpendicular to the assembly orientation can reduce the bond lifetime significantly by driving the key particle to approach the minimum path. Moreover, the dissociation dynamics can be facilitated even by a pushing force compared to the spontaneous dissociation (without forces). To elucidate the effective pathway under pulling, the escaping position is analyzed and its mean direction with respect to the assembly orientation rises generally with increasing θ, revealing that the presence of the force component along the minimum pathway is helpful. The importance of the direction of the external pulling has been demonstrated in our simple system. Therefore, this effect should be considered in more complicated unbinding experiments.

Curvature-Induced Lipid Sorting in Plasma Membrane Tethers

Membrane tethers are nanotubes formed by lipid bilayers. They are efficient structures for cellular transport and communication, and for storage of excess membrane area. Previous tether pulling experiments provided insights on membrane mechanical properties, and the curvature effects on phase behaviour and distribution of coexisting phases. However, detailed information on tether properties and variations in composition is challenging to obtain experimentally due to the small diameters and dynamic nature of tethers. Here we provide a molecular view on curvature-induced lipid sorting in plasma membrane tethers. We pulled tethers from an idealized plasma membrane model using molecular dynamics simulations with the coarse-grained Martini model. The membrane consists of 63 lipid types with an asymmetric distribution of components between the leaflets [JACS, 2014, 136, 14554]. The tethers are formed by applying an external constant force to a lipid patch in the direction normal to the bilayer plane [Biophys J, 1012, 102, 1866]. Pulling is performed both from the inner and outer leaflets, corresponding to the direction in and out of the cell, respectively. As a result of pulling, we observe re-distribution of different lipid types along the regions of different curvature without macroscopic phase separation. Depending on the direction of pulling, the distribution of lipids and the tether properties differ.

Curvature-Induced Lipid Sorting in Plasma Membrane Tethers

Membrane tethers are nanotubes formed by lipid bilayers. They are efficient structures for cellular transport and communication, and for storage of excess membrane area. Previous tether pulling experiments provided insights on membrane mechanical properties, and the curvature effects on phase behaviour and distribution of coexisting phases. However, detailed information on tether properties and variations in composition is challenging to obtain experimentally due to the small diameters and dynamic nature of tethers.Here we provide a molecular view on curvature-induced lipid sorting in plasma membrane tethers. We pulled tethers from an idealized plasma membrane model using molecular dynamics simulations with the coarse-grained Martini model. The membrane consists of 63 lipid types with an asymmetric distribution of components between the leaflets [JACS, 2014, 136, 14554]. The tethers are formed by applying an external constant force to a lipid patch in the direction normal to the bilayer plane [Biophys J, 1012, 102, 1866]. Pulling is performed both from the inner and outer leaflets, corresponding to the direction in and out of the cell, respectively. As a result of pulling, we observe re-distribution of different lipid types along the regions of different curvature without macroscopic phase separation. Depending on the direction of pulling, the distribution of lipids and the tether properties differ.

Protein co-translocational unfolding depends on the direction of pulling

Protein unfolding and translocation through pores occurs during trafficking between organelles, protein degradation and bacterial toxin delivery. In vivo, co-translocational unfolding can be affected by the end of the polypeptide that is threaded into the pore first. Recently, we have shown that co-translocational unfolding can be followed in a model system at the single-molecule level, thereby unravelling molecular steps and their kinetics. Here, we show that the unfolding kinetics of the model substrate thioredoxin, when pulled through an α-haemolysin pore, differ markedly depending on whether the process is initiated from the C terminus or the N terminus. Further, when thioredoxin is pulled from the N terminus, the unfolding pathway bifurcates: some molecules finish unfolding quickly, while others finish ~100 times slower. Our findings have important implications for the understanding of biological unfolding mechanisms and in the application of nanopore technology for the detection of proteins and their modifications.

Unbinding and unfolding of adhesion protein complexes through stretching: interplay between shear and tensile mechanical clamps.

Using coarse-grained molecular dynamics simulations, we analyze mechanically induced dissociation and unfolding of the protein complex CD48-2B4. This heterodimer is an indispensable component of the immunological system: 2B4 is a receptor on natural killer cells whereas CD48 is expressed on surfaces of various immune cells. So far, its mechanostability has not been assessed either experimentally or theoretically. We find that the dissociation processes strongly depend on the direction of pulling and may take place in several pathways. Interestingly, the CD48-2B4 interface can be divided into three distinct patches that act as units when resisting the pulling forces. At experimentally accessible pulling speeds, the characteristic mechanostability forces are in the range between 100 and 200 pN, depending on the pulling direction. These characteristic forces need not be associated with tensile forces involved in the act of separation of the complex because prior shear-involving unraveling within individual proteins may give rise to a higher force peak.

Single-Molecule Rupture Dynamics on Multidimensional Landscapes

The unfolding of a biomolecule by stretching force is commonly treated theoretically as one-dimensional dynamics along the reaction coordinate coincident with the direction of pulling. Here we explore a situation, particularly relevant to complex biomolecules, when the pulling direction alone is not an adequate reaction coordinate for the unfolding or rupture process. We show that in this case the system can respond to pulling force in unusual ways. Our theory points out a remarkably simple, but largely overlooked, mechanism of the complex responses of biomolecules to force. The mechanism originates from the basic property of the transition state to change its structure under applied force. A relationship is established between a key experimental observable, force-dependent lifetime, and the microscopic properties of the biomolecule in the form of an analytical solution to the problem of a force-induced molecular transition in two dimensions. The theory is applicable to biological contexts ranging from protein folding to ligand-receptor interactions.

Biomolecules under mechanical stress: A simple mechanism of complex behavior

The unfolding of a biomolecule by stretching force is commonly treated theoretically as one-dimensional dynamics along the reaction coordinate coincident with the direction of pulling. Here we explore a situation, particularly relevant to complex biomolecules, when the pulling direction alone is not an adequate reaction coordinate for the unfolding or rupture process. We show that in this case the system can respond to pulling force in unusual ways. Our theory points out a remarkably simple, but largely overlooked, mechanism of the complex responses of biomolecules to force. The mechanism originates from the basic property of the transition state to change its structure under applied force. A relationship is established between a key experimental observable--force-dependent lifetime--and the microscopic properties of the biomolecule in the form of an analytical solution to the problem of a force-induced molecular transition in two dimensions. The theory is applicable to biological contexts ranging from protein folding to ligand-receptor interactions.

Mechanics of Collagen in the Human Bone: Role of Collagen-Hydroxyapatite Interactions

AbstractHere, we report results of our simulations studies on modeling the collagen-hydroxyapatite (HAP) interface in bone and influence of these interactions on mechanical behavior of collagen through molecular dynamics and steered molecular dynamics (SMD). Models of hexagonal HAP (10-10) and (0001) surface, and collagen with and without telopeptides were built to investigate the mechanical response of collagen in the proximity of mineral. The collagen molecule was pulled normal and parallel to the (0001) surface of hydroxyapatite. Water molecules were found have an important impact on deformation behavior of collagen in the proximity of HAP due to their large interaction energy with both collagen and HAP. Collagen appears stiffer at small displacement when pulled normal to HAP surface. At large displacement, collagen pulled parallel to HAP surface is stiffer. This difference in mechanical response of collagen pulled in parallel and perpendicular direction results from a difference in deformation mechanism of collagen. Further, the collagen molecule pulled in the proximity of HAP, parallel to surface, showed marked improvement in stiffness compared to absence of HAP. Furthermore, the deformation behavior of collagen not only depends on the presence or absence of HAP and direction of pulling, but also on the type of mineral surface in the proximity. The collagen pulled parallel to (10-10) and (0001) surfaces showed characteristically different type of load-displacement response. In addition, here we also report simulations on 300 nm length of collagen molecule indicating the role of length of model on the observed response in terms of both the magnitude of modulus obtained as well as the mechanisms of response of collagen to loading.

Tugging at Heartstrings

Biophysics![Figure][1] CREDIT: BERTZ ET AL., PROC. NATL. ACAD. SCI. U.S.A. 106 , 10.1073/PNAS.0902312106 (2009) One of the first lessons in learning to work with wood is that it exhibits a resistance to compression or tension that depends upon the direction in which force is applied. A macroscopic clue to this anisotropic behavior can be found by examining the wood grain. Bertz et al. demonstrate that this phenomenon can also be observed at the molecular level in their atomic force microscopy investigation of titin, a structural protein found in skeletal and cardiac muscle. In these tissues titin is subject to considerable force, and the endcap protein, telethonin (red), grasps two titin molecules, binding to the N-terminal domain Z1 (dark green and blue) and the next interior one Z2 (light green and blue). Pulling apart this joint requires a force of 700 pN when applied to Z2 (that is, the normal physiological direction of pulling), but only one-third as much force need be applied to Z1; the difference is accounted for by directionally oriented hydrogen bonds (gray) between telethonin and the Z2 domain. Proc. Natl. Acad. Sci. U.S.A. 106 , 10.1073/pnas.0902312106 (2009). [1]: pending:yes

Evaluation of Landscape Tree Stabilization Systems

We conducted pull tests on newly planted 7 cm (2.8 in) caliper, container-grown Quercus virginiana ‘SDLN’ PP#12015, Cathedral Oak® to simulate wind loading on nine commonly used landscape tree stabilization systems. Maximum force required to rotate the root ball 20° was used to compare systems. Terra Toggle™, Brooks Tree Brace®, and 2 × 2’s anchoring the root ball withstood the largest forces. Typically, trees secured by these three broke before the systems failed indicating that the systems were very effective. T-stakes, dowels, and Tree Staple™ performed no better than nonstaked controls. The three guying systems tested, ArborBrace®, Duckbill®, and rebar and ArborTie®, were statistically similar and required more force to failure than controls, but less than the group that withstood the largest forces. Direction of pulling had no influence on force to failure for any stabilization system tested.