Lecture_3_molecular_forces_2011

# Lecture_3_molecular_forces_2011 - Introduction to...

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Introduction to Biophysics Lecture 3 Molecular forces in Biological Structures

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non-covalent interactions Electrostatic interaction Charge – dipole interaction Induced Dipoles Cation - π interaction Dispersion forces Hydrophobic forces Hydration forces Hydrogen bounds Steric repulsion
Electrostatic self energy: The energy of placing ion in a dielectric medium. Consider the work done to bring a small increment of charge δ q’ to the surface of a sphere with radius r, already carrying a charge, q’ This charging process can be integrated to get the total work done, starting with charge = 0 and final charge = q. This equation can be used to estimate the free energy (F) of placing an ion in a solvent with particular dielectric constant. Find a difference between the electrostatic self-energy for ion (Na + , r=0.95Å) in two media (water and hydrocarbon(membrane)) and estimate the free energy of transfer of Na + ions between two media. Give a answer in k B T and kcal mole -1

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Can we predict partition - (P) or distribution coefficient (D) (the ratio of concentrations of a compound in the two phases of a mixture of two immiscible solvents at equilibrium.) of charged particle (ion) in water/hydrocarbon system by knowing its electrostatic self-energy?
Discrete distribution Probability of observing x i N i /N =P(x i ) for large N Σ i P(x i ) = 1 normalization condition Continuous distributions Bins of width d x dN (x 0

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## This note was uploaded on 12/09/2011 for the course PHYS 570 taught by Professor Staff during the Fall '08 term at Purdue.

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Lecture_3_molecular_forces_2011 - Introduction to...

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