scholarly journals A surface-bound molecule that undergoes optically biased Brownian rotation

2014 ◽  
Vol 9 (2) ◽  
pp. 131-136 ◽  
Author(s):  
James A. Hutchison ◽  
Hiroshi Uji-i ◽  
Ania Deres ◽  
Tom Vosch ◽  
Susana Rocha ◽  
...  
Keyword(s):  
2014 ◽  
Vol 11 (97) ◽  
pp. 20140320 ◽  
Author(s):  
Gabriel Rosser ◽  
Ruth E. Baker ◽  
Judith P. Armitage ◽  
Alexander G. Fletcher

Most free-swimming bacteria move in approximately straight lines, interspersed with random reorientation phases. A key open question concerns varying mechanisms by which reorientation occurs. We combine mathematical modelling with analysis of a large tracking dataset to study the poorly understood reorientation mechanism in the monoflagellate species Rhodobacter sphaeroides . The flagellum on this species rotates counterclockwise to propel the bacterium, periodically ceasing rotation to enable reorientation. When rotation restarts the cell body usually points in a new direction. It has been assumed that the new direction is simply the result of Brownian rotation. We consider three variants of a self-propelled particle model of bacterial motility. The first considers rotational diffusion only, corresponding to a non-chemotactic mutant strain. Two further models incorporate stochastic reorientations, describing ‘run-and-tumble’ motility. We derive expressions for key summary statistics and simulate each model using a stochastic computational algorithm. We also discuss the effect of cell geometry on rotational diffusion. Working with a previously published tracking dataset, we compare predictions of the models with data on individual stopping events in R. sphaeroides . This provides strong evidence that this species undergoes some form of active reorientation rather than simple reorientation by Brownian rotation.


1977 ◽  
Vol 31 (3) ◽  
pp. 548-557 ◽  
Author(s):  
F. M. Kuni ◽  
B. A. Storonkin

1980 ◽  
Vol 61 (6) ◽  
pp. 327-376 ◽  
Author(s):  
George Wyllie

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Eva Bertosin ◽  
Christopher M. Maffeo ◽  
Thomas Drexler ◽  
Maximilian N. Honemann ◽  
Aleksei Aksimentiev ◽  
...  

AbstractBiological molecular motors transform chemical energy into mechanical work by coupling cyclic catalytic reactions to large-scale structural transitions. Mechanical deformation can be surprisingly efficient in realizing such coupling, as demonstrated by the F1FO ATP synthase. Here, we describe a synthetic molecular mechanism that transforms a rotary motion of an asymmetric camshaft into reciprocating large-scale transitions in a surrounding stator orchestrated by mechanical deformation. We design the mechanism using DNA origami, characterize its structure via cryo-electron microscopy, and examine its dynamic behavior using single-particle fluorescence microscopy and molecular dynamics simulations. While the camshaft can rotate inside the stator by diffusion, the stator’s mechanics makes the camshaft pause at preferred orientations. By changing the stator’s mechanical stiffness, we accelerate or suppress the Brownian rotation, demonstrating an allosteric coupling between the camshaft and the stator. Our mechanism provides a framework for manufacturing artificial nanomachines that function because of coordinated movements of their components.


2006 ◽  
Vol 11 (4) ◽  
pp. 189-194 ◽  
Author(s):  
Seok-Hwan Chung ◽  
Axel Hoffmann ◽  
Liaohai Chen ◽  
Shouheng Sun ◽  
Konstantin Guslienko ◽  
...  

1972 ◽  
Vol 56 (4) ◽  
pp. 803-813 ◽  
Author(s):  
E. J. Hinch ◽  
L. G. Leal

A problem of theoretical interest in suspension rheology is the calculation of bulk rheological properties for a dilute suspension of spherical dipolar particles in the presence of weak Brownian rotation, when the applied field is perpendicular to the local vorticity of the bulk flow. In the present note, we determine the asymptotic form for the orientation distribution of the dipole axis in the limit of weak Brownian motion and use this distribution to determine the corresponding rheological properties of the suspension. The bulk stress is then discussed in terms of an effective viscosity for shear flow.


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