Lecture_11_2011_sept29

Lecture_11_2011_sept29 - depending on the refractive index...

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Introduction to Biophysics Lecture 11 Focus on microsystem
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Although the far-from-equilibrium condition of an organism represents an absolute precondition of life, nevertheless, subsystems in the organism exist, which can be properly calculated using equilibrium thermodynamics.
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Concept of “global” state Global states are defined in terms of a protein’s functional capability. We will assume that a protein has a few – perhaps just two – of these global states. Global states can interconvert, in what we will call global transitions. In terms of structure the global state is a black box. A global state is envisioned as encompassing a large number of microstates. The microstates interconvert rapidly and the global state reflects the average behavior of these microstates. This view is taken directly from statistical mechanics.
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An optical tweezer is a scientific instrument that uses a focused laser beam to provide an attractive or repulsive force (typically on the order of piconewtons),
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Unformatted text preview: depending on the refractive index mismatch to physically hold and move microscopic dielectric objects. Optical tweezers have been particularly successful in studying a variety of biological systems in recent years. Dielectric particles are attracted along the gradient to the region of strongest electric field, which is the center of the beam. The scattering force results in the particle being displaced slightly downstream from the exact position of the beam waist. Microscope objective The force applied on the object depends linearly on displacement from the trap center. Suggested reading: Nelson Chapter 6 Home work: Demonstrate that Boltzmann Distribution minimizes the Fa – free energy of microsystem. Demonstrate that minimum of the F (free energy or Helmholtz energy) for microscopic state (a) in the thermal contact with large reservoir (B) equal to F(min)= -k B TlnZ where Z- is partition function...
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