  Proteins dissolved in a drop induce and enhance the pinning of the drop
contact line. This effect dramatically increases volume of drops that are
vertically pinned on a flat siliconized substrate. The drop pinning behavior
exhibits two regimes: for low protein content in a drop the pinning increases
as the contact angle hysteresis increases, and for high protein content the
pinning decreases as the surface tension of the protein solution decreases.
