scholarly journals Bending-torsional elasticity and energetics of the plus-end microtubule tip

2021 ◽  
Author(s):  
Maxim Igaev ◽  
Helmut Grubmueller
Keyword(s):  
Activation Energy ◽  
Elastic Energy ◽  
Lattice Strain ◽  
Atomistic Simulations ◽  
Lateral Interactions ◽  
Time Resolved ◽  
Ratchet Mechanism ◽  
Torsional Strain ◽  
Spontaneous Relaxation ◽  
Lattice Formation

Microtubules (MTs), mesoscopic cellular filaments, grow primarily by the addition of GTP-bound tubulin dimers at their dynamic flaring plus-end tips. They operate as chemomechanical energy transducers with stochastic transitions to an astounding shortening motion upon hydrolyzing GTP to GDP. Time-resolved dynamics of the MT tip - a key determinant of this behavior - as a function of nucleotide state, internal lattice strain, and stabilizing lateral interactions have not been fully understood. Here, we use atomistic simulations to study the spontaneous relaxation of complete GTP-MT and GDP-MT tip models from unfavorable straight to relaxed splayed conformations and to comprehensively characterize the elasticity of MT tips. Our simulations reveal the dominance of viscoelastic dynamics of MT protofilaments during the relaxation process, driven by the stored bending-torsional strain and counterbalanced by the inter-protofilament interactions. We show that the post-hydrolysis MT tip is exposed to higher activation energy barriers for straight lattice formation, which translates into its inability to elongate. Our study provides an 'information ratchet' mechanism for the elastic energy conversion and release by MT tips and offers new insights into the mechanoenzymatics of MTs.

scholarly journals The Cross-Bridge Spring: Can Cool Muscles Store Elastic Energy?

Science ◽  
2013 ◽  
Vol 340 (6137) ◽  
pp. 1217-1220 ◽  
Author(s):  
N. T. George ◽  
T. C. Irving ◽  
C. D. Williams ◽  
T. L. Daniel
Keyword(s):  
Energy Storage ◽  
Elastic Energy ◽  
Molecular Motors ◽  
High Speed ◽  
Mechanical Energy ◽  
Elastic Strain Energy ◽  
Time Resolved ◽  
X Ray ◽  
Cross Bridge ◽  
Cross Bridges

Muscles not only generate force. They may act as springs, providing energy storage to drive locomotion. Although extensible myofilaments are implicated as sites of energy storage, we show that intramuscular temperature gradients may enable molecular motors (cross-bridges) to store elastic strain energy. By using time-resolved small-angle x-ray diffraction paired with in situ measurements of mechanical energy exchange in flight muscles of Manduca sexta, we produced high-speed movies of x-ray equatorial reflections, indicating cross-bridge association with myofilaments. A temperature gradient within the flight muscle leads to lower cross-bridge cycling in the cooler regions. Those cross-bridges could elastically return energy at the extrema of muscle lengthening and shortening, helping drive cyclic wing motions. These results suggest that cross-bridges can perform functions other than contraction, acting as molecular links for elastic energy storage.

Generalized Activation Energy Spectrum Theory: A New Approach for modeling Structural Relaxation in Amorphous Solids

1993 ◽  
Vol 321 ◽  
Author(s):  
Jung H. Shin ◽  
Harry A. Atwater
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Structural Relaxation ◽  
Ad Hoc ◽  
Amorphous Solids ◽  
Nucleation Kinetics ◽  
Crystal Silicon ◽  
Time Resolved ◽  
New Approach ◽  
Kinetics Of

ABSTRACTA general approach to the dynamics of structural relaxation in amorphous solids is developed. A form of the recombination kinetics of defects is chosen which removes the ad hoc assumption made in previous theories that defects recombine only with others of identical activation energy. The generalized theory is tested quantitatively by modelling the structural relaxation of amorphous silicon, and comparing the results with the experimental data on structural relaxation. It is found that the generalized theory is necessary in order to accurately describe the time-resolved relaxation data. The generalized theory is also applied to estimate the effect of irradiation on the nucleation kinetics of crystal silicon, and is found to agree well with experimental data.

scholarly journals Estimating the activation energy of bond hydrolysis by time-resolved weighing of dissolving crystals

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Philippe Ackerer ◽  
Arnaud Bouissonnié ◽  
Raphael di Chiara Roupert ◽  
Damien Daval
Keyword(s):  
Activation Energy ◽  
Crystal Surface ◽  
Calibration Method ◽  
Solute Concentration ◽  
Bond Breaking ◽  
Dissolution Rates ◽  
Experimental Conditions ◽  
Time Resolved ◽  
Crystal Dissolution ◽  
Dissolution Model

AbstractBond-breaking activation energy EB is nowadays a key parameter for understanding and modeling crystal dissolution processes. However, a methodology to estimate EB based on classical dissolution experiments still does not exist. We developed a new method based on the calibration of a Kossel type dissolution model on measured dissolution rates obtained by mass (or volume) variations over time. The dissolution model does not depend on the geometry of the crystal surface but only on the density of the different types of sites (kink, step, terrace, bulk). The calibration method was applied to different experimental setups (flow through and batch) with different ways of estimating the dissolution rates (solute concentration in the fluid, surface topography) for calcite crystals. Despite the variety of experimental conditions, the estimated bond-breaking activation energies were very close to each other (between 31 and 35 kJ/mol) and in good agreement with ab initio calculations.

scholarly journals Influence of Mn, Fe, Co, and Cu Doping on the Photoelectric Properties of 1T HfS2 Crystals

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 173
Author(s):  
Der-Yuh Lin ◽  
Yu-Tai Shih ◽  
Wei-Chan Tseng ◽  
Chia-Feng Lin ◽  
Hone-Zern Chen
Keyword(s):  
Electron Microscopy ◽  
Activation Energy ◽  
Transition Metal Dichalcogenides ◽  
Chemical Vapor ◽  
Vital Role ◽  
Chemical Vapor Transport ◽  
Time Resolved ◽  
Cu Doping ◽  
Photoelectric Properties ◽  
Co Doped

Doping plays a vital role in the application of transition-metal dichalcogenides (TMDCs) because it can increase the functionality of TMDCs by tuning their native characteristics. In this study, the influence of Mn, Fe, Co, and Cu doping on the photoelectric properties of HfS2 was investigated. Pristine, Mn-, Fe-, Co-, and Cu-doped HfS2 crystals were grown using the chemical vapor transport method. Scanning electron microscopy images showed that the crystals were layered and transmission electron microscopy, X-ray diffraction, and Raman spectroscopy measurements confirmed that the crystals were in the 1T-phase with a CdI2-like structure. The bandgap of pristine HfS2 obtained from the absorption and photoconductivity spectra was approximately 1.99 eV. As the dopant changed from Mn, Fe, and Co, to Cu, the bandgap gradually increased. The activation energies of the samples were determined using temperature-dependent current-voltage curves. After doping, the activation energy decreased, and the Co-doped HfS2 exhibited the smallest activation energy. Time-resolved photoresponse measurements showed that doping improved the response of HfS2 to light; the Co-doped HfS2 exhibited the best response. The photoresponsivity of HfS2 as a function of the laser power and bias voltage was measured. After doping, the photoresponsivity increased markedly; the Co-doped HfS2 exhibited the highest photoresponsivity. All the experimental results indicated that doping with Mn, Fe, Co, and Cu significantly improved the photoresponsive performance of HfS2, of which Co-doped HfS2 had the best performance.

Using Space-Time Correlations to Identify Transient Defects

MRS Advances ◽  
2018 ◽  
Vol 3 (31) ◽  
pp. 1755-1760
Author(s):  
William Lowe ◽  
Jacob Eapen
Keyword(s):  
Dynamical Behavior ◽  
Atomistic Simulations ◽  
Dynamic Tension ◽  
Time Resolved ◽  
Scale Free ◽  
Self Organized ◽  
Time Correlations ◽  
Simulation Results ◽  
Early Radiation ◽  
Cubic Silicon Carbide

ABSTRACTAtomistic simulations are employed to investigate the dynamical behavior of atoms in cubic silicon carbide (SiC) following a 5 keV radiation knock. Specifically, we have computed the time-resolved van Hove self-correlation function, Gs(r,t), separately for the silicon and carbon sub-lattices. Our goal is to probe the early radiation damage mechanisms using a dynamical methodology. The simulation results show that the carbon atoms engage in a dynamic hopping mechanism as the system recovers from the radiation knock. The silicon atoms, however, exhibit a strikingly different behaviour: the time variation of 4πr2Gs(r,t) indicates a dynamic tension between the crystalline and disordered regions of the Si sub-lattice. The power-law tail of the 4πr2Gs(r,t) correlation for silicon atoms suggests a scale-free self-organized critical (SOC) state – a possible precursor to the collapse of the Si sub-lattice.

scholarly journals Nanoplasmonic Sensing of CH3NH3PbI3 Perovskite Formation in Mimic of Solar Cell Photoelectrodes

2018 ◽  
Author(s):  
Fahd M. Rajab
Keyword(s):  
Activation Energy ◽  
Tio2 Film ◽  
Mesoporous Tio2 ◽  
Photovoltaic Device ◽  
Localized Surface Plasmon ◽  
Significant Finding ◽  
Lead Iodide ◽  
Host Matrix ◽  
Time Resolved ◽  
Reaction Activation Energy

The formation of methylammonium lead iodide (CH3NH3PbI3) perovskite into mesoporous titania (TiO2) scaffold via a sequential deposition method is known to offer high quality films for good photovoltaic device performance. The growth reactions at the mesoporous TiO2 film depend on reactants concentration in the host matrix and the reaction activation energy. Here, we have used a NanoPlasmonic Sensing (NPS) approach with gold (Au) nanosensors to monitor the formation of CH3NH3PbI3 perovskite at the lower interface of 350 nm mesoporous TiO2, typical thickness used in a photovoltaic device. This technique provides time-resolved spectral shifts of the localized surface plasmon resonance at different operating temperatures and methylammonium iodide (CH3NH3I3) concentrations by recording changes in the local vicinity of the Au nanosensors at the mesoporous TiO2 film interface. Analytical studies included Ellipsometry, Scanning Electron Microscopy, and X-ray diffraction. The results show that perovskite conversion can be obtained at lower CH3NH3I3 concentrations if reaction activation energy is lowered. A significant finding is that the NPS response at 350 nm mesoporous TiO2 can widely change from red shifts to blue shifts depending on extent of conversion and morphology of perovskite formed at given reaction conditions.

New low activation energy processes in La2CuO4+δ by elastic energy loss experiments

1997 ◽  
Vol 282-287 ◽  
pp. 1429-1430 ◽  
Author(s):  
G. Cannelli ◽  
R. Cantelli ◽  
F. Cordero ◽  
F. Trequattrini ◽  
M. Ferretti
Keyword(s):  
Activation Energy ◽  
Energy Loss ◽  
Elastic Energy ◽  
Energy Processes
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