Capillary Isoelectric Focusing of Proteins

Field & Gradient

Electric field 15 kV/cm

pH gradient width 7.0 pH

Diffusion / temperature 4

Proteins (by pI)

Live Readouts

Focusing time

0.0 s

Off-gradient bands

0 / 5

Worst-pair resolution R_s

—

How it works

Inside the capillary a stable pH gradient runs from the acidic anode to the basic cathode (built and held in place by carrier ampholytes). A protein's net electric charge depends on the local pH — above its isoelectric point (pI) it is net negative, below it, net positive. The simulation drives each molecule with:

z(pH) = z_max · tanh[k · (pI − pH)]
v(x)  = μ · E · z(pH(x))

Because z(pH) flips sign exactly at pH = pI, every molecule is pushed back toward the point in the capillary where the local pH equals its own pI — a self-focusing restoring force, not a simple constant drift. Random thermal diffusion keeps trying to spread each band back out; the sharp band width you see is the steady-state balance between the two, exactly as in real capillary isoelectric focusing (cIEF).

Electric field — scales the focusing force μ·E; higher field pulls proteins to their pI faster and tightens each band.
pH gradient width — narrowing it steepens dpH/dx, sharpening resolution, but any protein whose pI falls outside the covered range can no longer find its null point and piles up at the nearest electrode instead — a real trade-off ampholyte selection has to make.
Diffusion / temperature — raises the random-walk term that broadens each band; more heat (higher run current) means blurrier peaks.
Resolution R_s reported below mirrors the standard separation-science definition, R_s = Δx / [2(σ₁+σ₂)], applied to the worst-separated pair of adjacent bands.

Anode · low pH Cathode · high pH

⚠ Couldn't load the 3D engineThree.js failed to load from the CDN. Check your connection and reload.