Methods, devices and systems for characterizing proteins

Abstract

A method of characterizing a polypeptide, comprising providing a first capillary channel having a separation buffer disposed within, wherein the separation buffer comprises a non-crosslinked polymer solution, a buffering agent, a detergent, and a lipophilic dye. The separation buffer is provided such that, at the time of detection, the detergent concentration in the buffer is not above the critical micelle concentration. The polypeptide is introduced into one end of the capillary channel. An electric field is applied across a length of the capillary channel, which transports polypeptides of different sizes through the polymer solution at different rates. The polypeptide is then detected as it passes a point along the length of the capillary channel.

What is claimed is:  
     
         1 . A microfluidic device comprising: 
 a body structure having at least one main channel, said main channel having an analysis segment and a detection segment;    at least a first diluent source fluidly coupled to the main channel at a first location immediately upstream of said detection segment; and    a flow controller operably coupled to the first diluent source for delivering the first diluent into the main channel at said first location.    
     
     
         2 . The device of  claim 1 , wherein the first location is positioned along said main channel at a point after the analysis segment and immediately before the detection segment.  
     
     
         3 . The device of  claim 1 , further comprising at least a second diluent source fluidly coupled to the main channel at a second location immediately upstream of said detection segment.  
     
     
         4 . The device of  claim 1 , wherein the flow controller comprises an electrical controller.  
     
     
         5 . The device of  claim 3 , wherein the first and second diluent sources are fluidly coupled to the main channel at a common intersection.  
     
     
         6 . The device of  claim 1 , wherein the analysis segment comprises a detergent having a detergent concentration that is at or above a CMC for the detergent, and the detection segment comprises a detergent having a detergent concentration that is below the CMC for the detergent.  
     
     
         7 . The device of  claim 1 , wherein the main channel comprises a separation buffer that includes a polymer matrix and a buffering agent.  
     
     
         8 . The device of  claim 6 , wherein the detergent in the analysis segment and detection segment is an alkyl sulfate detergent.  
     
     
         9 . The device of  claim 6 , wherein the detergent in the analysis segment and detection segment is selected from sodium decylsulfate, sodium dodecylsulfate and sodium octadecylsulfate.  
     
     
         10 . The device of  claim 7 , wherein the first diluent comprises a dilution buffer that comprises the buffering agent and no detergent.  
     
     
         11 . The device of  claim 1  wherein the main channel is a separation channel in which a separation operation is performed, and wherein the first diluent source intersects the main channel at a location which is substantially downstream along a length of the main channel.  
     
     
         12 . The device of  claim 1  wherein the main channel is a separation channel in which a separation operation is performed, and wherein the first diluent source intersects the main channel at a location after the separation operation is performed.