Devices for Flow Step Focusing (FSF)

Abstract

Flow step focusing isolates and concentrates a molecule of interest by flowing a liquid comprising a molecule of interest through a main channel having an inlet and an outlet with application of a first pressure at the inlet; applying a voltage along the channel during the flowing, wherein the voltage is configured to have a polarity such that it drives the molecule of interest in a direction opposite the flow of the liquid; controlling the first pressure and/or the voltage in a manner so as to trap and concentrate the molecule of interest in a region of the main channel; and removing the concentrated molecule of interest from the channel by recovering a portion of the liquid from a side channel diverging from the main channel, wherein the side channel is maintained at a pressure lower than the first pressure. Also disclosed is an apparatus for such.

What is claimed is: 
     
         1 . An apparatus configured to isolate and concentrate a molecule of interest, the apparatus comprising:
 a main channel having an inlet and an outlet;   a side channel intersecting the main channel and having a side channel outlet;   a first pressure controller operably connected to the inlet and configured for pumping fluid into the inlet;   a second pressure controller operably connected to either the main channel outlet or the side channel outlet and configured to apply a pressure thereto; and   electrodes at each of the inlet and the outlet operably connected to a voltage controller configured to generate a voltage between the electrodes so as to generate an electric field along the channel, wherein the electric field is sufficiently strong to drive a molecule of interest in a direction opposite to flow of a liquid from the inlet to the outlet.   
     
     
         2 . An apparatus according to  claim 1 , wherein the main channel is substantially optically transparent at the intersection with the side channel. 
     
     
         3 . The apparatus according to  claim 1 , further comprising a second side channel positioned in the vicinity of the side channel and configured to add fluid to the main channel. 
     
     
         4 . The apparatus according to  claim 1 , further comprising a detector configured to detect a position of a band of a molecule of interest in the main channel. 
     
     
         5 . The apparatus according to  claim 4 , further comprising an automated system configured to receive the position of the band from the detector and to adjust the first pressure controller and/or the voltage controller in response thereto. 
     
     
         6 . The apparatus according to  claim 1 , further comprising an analytic instrument operably connected to the side channel outlet. 
     
     
         7 . The apparatus according to  claim 6 , wherein said analytic instrument is a mass spectrometer. 
     
     
         8 . The apparatus according to  claim 6 , further comprising a protein digester downstream of the side channel outlet. 
     
     
         9 . An apparatus configured to isolate and concentrate a molecule of interest, the apparatus comprising:
 a main channel having an inlet and an outlet;   a side channel intersecting the main channel and having a side channel outlet;   a first pressure controller operably connected to the inlet and configured for pumping fluid into the inlet;   a second pressure controller operably connected to either the main channel outlet or the side channel outlet and configured to apply a pressure thereto;   electrodes at each of the inlet and the outlet operably connected to a voltage controller configured to generate a voltage between the electrodes so as to generate an electric field along the channel, wherein the electric field is sufficiently strong to drive a molecule of interest in a direction opposite to flow of a liquid from the inlet to the outlet; and   a detector configured to detect a position of a band of a molecule of interest in the main channel, the detector operating through a region of the main channel at the intersection with the side channel that is substantially optically transparent.