A globular protein carries net charge and has radius

PHYSICS · Multi-part · Fermi University Physics · Biophysics & Medical Physics · Macromolecules, membranes and cell architecture · Macromolecules, membranes and cell architecture

Forces, Machines and Signals, Ch Charges in salt water and the assembly of amphiphiles

Problem

A globular protein carries net charge −6e-6e and has radius a=2.5 nma = 2.5\,\mathrm{nm}. It sits in 100 mM100\,\mathrm{mM} monovalent salt at 298 K298\,\mathrm{K} (εr=78.4\varepsilon_r = 78.4, ℓB=0.715 nm\ell_B = 0.715\,\mathrm{nm}). ((a)) Find the Debye length at this ionic strength. ((b)) Use the screened potential of a charged sphere, ψ0=kBTezℓBa(1+κa)\psi_0 = \dfrac{k_BT}{e}\dfrac{z\ell_B}{a(1+\kappa a)}, to find the surface potential.

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