scholarly journals Direct measurement of conformational strain energy in protofilaments curling outward from disassembling microtubule tips

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Jonathan W Driver ◽  
Elisabeth A Geyer ◽  
Megan E Bailey ◽  
Luke M Rice ◽  
Charles L Asbury
Keyword(s):  
Direct Measurement ◽  
Strain Energy ◽  
Wave Model ◽  
Mechanical Work ◽  
Direct Approach ◽  
Work Output ◽  
Gtp Hydrolysis ◽  
Bending Strain ◽  
Motor Enzymes ◽  
Β Tubulin

Disassembling microtubules can generate movement independently of motor enzymes, especially at kinetochores where they drive chromosome motility. A popular explanation is the ‘conformational wave’ model, in which protofilaments pull on the kinetochore as they curl outward from a disassembling tip. But whether protofilaments can work efficiently via this spring-like mechanism has been unclear. By modifying a previous assay to use recombinant tubulin and feedback-controlled laser trapping, we directly demonstrate the spring-like elasticity of curling protofilaments. Measuring their mechanical work output suggests they carry ~25% of the energy of GTP hydrolysis as bending strain, enabling them to drive movement with efficiency similar to conventional motors. Surprisingly, a β-tubulin mutant that dramatically slows disassembly has no effect on work output, indicating an uncoupling of disassembly speed from protofilament strain. These results show the wave mechanism can make a major contribution to kinetochore motility and establish a direct approach for measuring tubulin mechano-chemistry.

Helical Domain Patterns in Tube Configurations: Effect of Geometry Length Scales

2011 ◽  
Vol 172-174 ◽  
pp. 1090-1095 ◽  
Author(s):  
R.H. Zhou ◽  
Qing Ping Sun
Keyword(s):  
Strain Energy ◽  
Optical Measurement ◽  
Strong Support ◽  
Martensite Phase ◽  
Helical Domain ◽  
Self Organized ◽  
Bending Strain ◽  
Strain Martensite ◽  
Tube Geometry

Superelastic NiTi polycrystalline tubes, when subjected to quasi-static stretching, transform from an initial austenite phase to a high-strain martensite phase by the formation and growth of a macroscopic self-organized helical domain as deformation progresses. This paper performed an experimental study on the effects of the externally applied stretching and tube geometry (length L, wall-thickness h and tube radius R) on the martensitic helical domains in the tubes under very slow (isothermal) stretching. The evolution of the helical domains with the applied strain in different tube geometries are quantified by in-situ optical measurement. We demonstrate that the shape of the self-organized helical domain and its evolution are governed by the competition between bending strain energy and domain front energy in minimizing the total energy of the tube system. The former favors a long slim helical domain, while the latter favors a short fat helical domain. The experimental results provide a strong support to the recently developed theoretical relationship.

Myocardial anaerobic metabolism in intact dogs

1963 ◽  
Vol 204 (3) ◽  
pp. 427-432 ◽  
Author(s):  
William A. Neill ◽  
Norman Krasnow ◽  
Herbert J. Levine ◽  
Richard Gorlin
Keyword(s):  
Energy Source ◽  
Oxygen Consumption ◽  
Oxidative Metabolism ◽  
Anaerobic Metabolism ◽  
Muscle Metabolism ◽  
Mechanical Work ◽  
Work Output ◽  
Heart Work ◽  
Anaerobic Energy ◽  
The Difference

Energy liberated from substrates of heart muscle metabolism appears as mechanical work and heat. External mechanical work and heat production of the left ventricle were compared with its oxygen consumption in intact dogs. Under control conditions, within the range of accuracy possible, the sum of work and heat was equal to energy from oxidative metabolism. Intravascular administration of cyanide increased heart work but reduced its rate of aerobic metabolism. During the cyanide effect, work plus heat exceeded the energy available from oxidative metabolism. The difference represents myocardial anaerobic metabolism. Since the energy of mechanical work output alone was greater than the myocardial aerobic energy source, a portion of the anaerobic energy liberated must have been converted to mechanical work.

Study on Characteristics of Energy for Hard Roof Fracture in Island Workface

2013 ◽  
Vol 734-737 ◽  
pp. 694-697
Author(s):  
Xu Feng Pang ◽  
Ke Xue Zhang
Keyword(s):  
Strain Energy ◽  
Typical Case ◽  
Energy Characteristics ◽  
Hard Roof ◽  
Coal Bump ◽  
Bending Strain ◽  
Before And After ◽  
Mechanical Models

According to the characteristics of the island workface with hard roof, various mechanical models of hard roof in island workface are established, to analyze energy characteristics of hard roof before and after the first fracture in island workface with all round gobs, derived their simplified formulas of bending strain energy for hard roof before and after the first fracture, and using these formulas to estimate the bending strain energy for the typical case of coal bump, reveals the energy cause of coal bump and verify the validity of these formulas.

scholarly journals Correction: Direct measurement of the mechanical work during translocation by the ribosome

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Tingting Liu ◽  
Ariel Kaplan ◽  
Lisa Alexander ◽  
Shannon Yan ◽  
Jin-Der Wen ◽  
...  
Keyword(s):  
Direct Measurement ◽  
Mechanical Work

scholarly journals Direct measurement of the mechanical work during translocation by the ribosome

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Tingting Liu ◽  
Ariel Kaplan ◽  
Lisa Alexander ◽  
Shannon Yan ◽  
Jin-Der Wen ◽  
...  
Keyword(s):  
Optical Tweezers ◽  
Direct Measurement ◽  
Applied Force ◽  
Mechanical Work ◽  
Regulatory Role ◽  
Characteristic Distance ◽  
Detailed Understanding ◽  
Chemical Cycle ◽  
The One ◽  
Stable Structures

A detailed understanding of tRNA/mRNA translocation requires measurement of the forces generated by the ribosome during this movement. Such measurements have so far remained elusive and, thus, little is known about the relation between force and translocation and how this reflects on its mechanism and regulation. Here, we address these questions using optical tweezers to follow translation by individual ribosomes along single mRNA molecules, against an applied force. We find that translocation rates depend exponentially on the force, with a characteristic distance close to the one-codon step, ruling out the existence of sub-steps and showing that the ribosome likely functions as a Brownian ratchet. We show that the ribosome generates ∼13 pN of force, barely sufficient to unwind the most stable structures in mRNAs, thus providing a basis for their regulatory role. Our assay opens the way to characterizing the ribosome's full mechano–chemical cycle.

scholarly journals Stressing State Analysis on a Single Tube CFST Arch Under Spatial Loads

2019 ◽  
Vol 9 (23) ◽  
pp. 5039
Author(s):  
Kangkang Yang ◽  
Jian Yuan ◽  
Jun Shi ◽  
Kaikai Zheng ◽  
Jiyang Shen
Keyword(s):  
Strain Energy Density ◽  
Strain Energy ◽  
Characteristic Curve ◽  
Arch Model ◽  
Average Strain ◽  
Bending Strain ◽  
Strain Data ◽  
Internal Forces ◽  
Arch Structures ◽  
Behavior Characteristics

This paper analyzes the stressing state characteristics of a concrete-filled steel tubular (CFST) arch model under spatial loads, using the method of modeling structural stressing state and the thin plate simulating interpolation (TSI) method. Firstly, the parameter-generalized strain energy density (GSED) is applied to model the stressing state of the arch. Then, the normalized GSED sum at each load plots the characteristic curve. The characteristic loads P (66 kN) and Q (85 kN) in the curve are distinguished by the Mann–Kendall (M–K) criterion. To characterize structural axial and bending stressing states, the parameters of the sectional average strain and generalized bending strain are proposed as stressing state submodes. Finally, the TSI method is used to interpolate strain data for deep analysis of internal forces. By modeling the structural stressing state, the working behavior characteristics of arch structures are greatly revealed in a particular view and the results could provide a reference for the development of bridge design.

Effect of resistive loading on inspiratory work output in anesthetized cats

1984 ◽  
Vol 57 (3) ◽  
pp. 839-849 ◽  
Author(s):  
L. Zocchi ◽  
S. C. Luijendijk ◽  
W. A. Zin ◽  
A. Rossi ◽  
J. Milic-Emili
Keyword(s):  
Esophageal Pressure ◽  
Mechanical Work ◽  
Work Output ◽  
Inspiratory Muscles ◽  
Model Predictions ◽  
Resistive Loading ◽  
The Face ◽  
The Stability ◽  
Spontaneously Breathing ◽  
Inspiratory Work

In five spontaneously breathing anesthetized cats, we determined the inspiratory elastic (Wel), resistive (Wres), and total (WI) mechanical work rates (power) during control and first loaded inspirations through graded linear resistances (delta R) by “Campbell diagrams” based on measurement of esophageal pressure. WI did not change with delta R's up to 0.31 cmH2O X ml-1 X s, the concomitant decrease in Wel being balanced by an increase in Wres. The stability of WI in the face of delta R's was due to the vagally mediated prolongation of inspiration and the intrinsic properties of the respiratory system and of the contracting inspiratory muscles. To assess the separate contributions of volume-related and flow-related intrinsic mechanisms to the stability of WI, we made model predictions of the immediate effects of delta R's on inspiratory mechanical work output based on measurements of inspiratory driving pressure waves and passive and active respiratory resistance and elastance on the same five cats. The results suggest that the intrinsic stability of WI in the face of delta R's is provided primarily by the active elastance.

Sign in / Sign up

Export Citation Format

Share Document