Polyunsaturated fatty acids inhibit Kv1.4 by interacting with positively charged extracellular pore residues

Polyunsaturated fatty acids (PUFAs) modulate voltage-gated K+ channel inactivation by an unknown site and mechanism. The effects of ω-6 and ω-3 PUFAs were investigated on the heterologously expressed Kv1.4 channel. PUFAs inhibited wild-type Kv1.4 during repetitive pulsing as a result of slowing of recovery from inactivation. In a mutant Kv1.4 channel lacking N-type inactivation, PUFAs reversibly enhanced C-type inactivation ( Kd, 15–43 μM). C-type inactivation was affected by extracellular H+ and K+ as well as PUFAs and there was an interaction among the three: the effect of PUFAs was reversed during acidosis and abolished on raising K+. Replacement of two positively charged residues in the extracellular pore (H508 and K532) abolished the effects of the PUFAs (and extracellular H+ and K+) on C-type inactivation but had no effect on the lipoelectric modulation of voltage sensor activation, suggesting two separable interaction sites/mechanisms of action of PUFAs. Charge calculations suggest that the acidic head group of the PUFAs raises the pKa of H508 and this reduces the K+ occupancy of the selectivity filter, stabilizing the C-type inactivated state.

DEUTERON ELECTRIC QUADRUPOLE AND OCTUPOLE POLARIZABILITIES

The direct transition-matrix approach to determination of the electric polarizabilities of quantum bound systems developed in my preceding work is applied to study the electric multipole polarizabilities of a two-particle bound complex with a central interaction between the particles. Expressions for the electric quadrupole and octupole polarizabilities of the deuteron are derived and their values in the case of the S-wave separable interaction potential are calculated.

On the epsilon - 0 limit of the Lippmann-Schwinger-Low states

The Lippmann–Schwinger–Low (LSL) quantum scattering states involve a resolvent operator depending on an infinitesimal adiabatic parameter ε. We reexamine the LSL formalism by taking the ε → + 0 limit at the end of the analysis (rather than at the outset). It is found that the LSL state vector |ψ kL > does not coincide with the Schrödinger eigen vector in Hilbert space as a whole, and the pair |ψ nL >, |ψ kL > is mutually nonorthogonal if the energy En = Ek, n ≠ k. For this purpose we carefully use a new type of projection operator ηk, a novel nonlinear relation among transition amplitudes, and a separable interaction as illustration. PACS Nos.: 0.3.65.Nk, 0.3.80.+r

HARTREE–FOCK–BOGOLUBOV APPROXIMATION IN THE MODELS WITH GENERAL FOUR-FERMION INTERACTION

An approach is proposed which allows one to investigate dynamical and thermodynamical properties of models with four-fermion interaction of general type. The approach combines ideas of the standard Bogolubov's approximating Hamiltonian method for the models with separable interaction with the method of Hartree–Fock approximation based on the ideas of self-consistency.