Efficient approximations for stationary single-channel Ca2+ nanodomains across length scales

摘要: We consider the stationary solution for Ca2+ concentration near a point source describing single-channel nanodomain, in presence of single mobile buffer with one-to-one binding. present computationally efficient approximants that estimate nanodomains great accuracy broad regions parameter space. The presented have functional form combines rational and exponential functions, which is similar to well-known Excess Buffer Approximation linear approximation, but parameters estimated using two novel (to our knowledge) methods. One methods involves interpolation between short-range Taylor series its long-range asymptotic inverse powers distance from channel. Although this method has already been used find Pade (rational-function) concentration, extending interpolants combining functions improves significant fraction relevant A second based on variational approach, global minimization an appropriate respect chosen approximations. Extensive sensitivity analysis presented, comparing these previously developed approximants. Apart increased accuracy, strength they can be extended more realistic buffers multiple binding sites characterized by cooperative binding, such as calmodulin calretinin. STATEMENT OF SIGNIFICANCEMathematical computational modeling plays important role study local signals underlying vesicle exocysosis, muscle contraction other fundamental physiological processes. Closed-form approximations steady-state distribution vicinity open channel proved particularly useful qualitative signals. simple buffer, achieve over wide range model parameters. Such provide estimating concentrations without resorting numerical simulations, allow dependence nanodomain properties diffusivity.