45 research outputs found
Effects of intermediate bound states in dynamic force spectroscopy
We revisit here some aspects of the interpretation of dynamic force
spectroscopy experiments. The standard theory predicts a typical unbinding
force linearly proportional to the logarithm of the loading rate when
a single energetical barrier controls the unbinding process; for a more complex
situation of barriers, it predicts at most linear segments for the
vs. curve, each segment characterizing a different barrier. We
here extend this existing picture using a refined approximation, we provide a
more general analytical formula, and show that in principle up to
segments can show up experimentally. As a consequence the interpretation of
data can be ambiguous, for the characteristics and even the number of barriers.
A further possible outcome of a multiple-barrier landscape is a bimodal or
multimodal distribution of the unbinding force at a given loading rate, a
feature recently observed experimentally.Comment: 7 pages, 5 figure
Mechanical Response of a Small Swimmer Driven by Conformational Transitions
A conformation space kinetic model is constructed to drive the deformation
cycle of a three-sphere swimmer to achieve propulsion at low Reynolds number.
We analyze the effect of an external load on the performance of this kinetic
swimmer, and show that it depends sensitively on where the force is exerted, so
that there is no general force--velocity relation. We discuss how the
conformational cycle of such swimmers should be designed to increase their
performance in resisting forces applied at specific points.Comment: 4 pages, 3 figures; accepted for publication in Phys. Rev. Let
Transverse electrokinetic and microfluidic effects in micro-patterned channels: lubrication analysis for slab geometries
Off-diagonal (transverse) effects in micro-patterned geometries are predicted
and analyzed within the general frame of linear response theory, relating
applied presure gradient and electric field to flow and electric current. These
effects could contribute to the design of pumps, mixers or flow detectors.
Shape and charge density modulations are proposed as a means to obtain sizeable
transverse effects, as demonstrated by focusing on simple geometries and using
the lubrication approximation.Comment: 9 pages, 7 figure