Enzyme quantification

Abstract

The invention generally relates to methods for quantifying an amount of enzyme molecules. Systems and methods of the invention are provided for measuring an amount of target by forming a plurality of fluid partitions, a subset of which include the target, performing an enzyme-catalyzed reaction in the subset, and detecting the number of partitions in the subset. The amount of target can be determined based on the detected number.

1 - 18 . (canceled) 
     
     
         19 . A method for detecting target molecules, the method comprising:
 providing a fluid sample comprising biological cells and a detection component for binding to target molecules secreted from the biological cells;   partitioning the fluid sample into a plurality of separate and isolated partitions of fluid; and   detecting each of the plurality of partitions associated with one or more secreted target molecules of one or more of the plurality of partitions, wherein the one or more secreted target molecules is a protein.   
     
     
         20 . The method of  claim 19 , wherein the secreted target molecule is a single biological molecule. 
     
     
         21 . The method of  claim 20 , wherein the single biological molecule is a protein. 
     
     
         22 . The method of  claim 21 , wherein the protein is an enzyme. 
     
     
         23 . The method of  claim 19 , wherein at least one of the plurality of droplets comprises a single biological cell. 
     
     
         24 . The method of  claim 19 , wherein the biological cell is bacteria. 
     
     
         25 . The method of  claim 24 , further comprising providing conditions suitable to cause the biological cells to replicate and secrete target biological molecules. 
     
     
         26 . The method of  claim 25 , wherein the target biological molecule comprises protease. 
     
     
         27 . The method of  claim 19 , wherein the detection component comprises one or more detectable labels. 
     
     
         28 . The method of  claim 27 , wherein the one or more detectable labels comprises at least one of an optical label, an enzymatic label, and a radioactive label. 
     
     
         29 . The method of  claim 28 , wherein the one or more detectable labels comprises one or more fluorogenic substances. 
     
     
         30 . The method of  claim 28 , wherein the event comprises release of a detectable label in at least one of the plurality of droplets. 
     
     
         31 . The method of  claim 30 , further comprising conducting a reaction in the at least one of the plurality of partitions, wherein the reaction results in release of the detectable label. 
     
     
         32 . The method of  claim 31 , wherein the reaction is an enzymatic reaction in one or more droplets containing a secreted target biological molecule, wherein, in response to the enzymatic reaction, the detectable label from each detection component is released. 
     
     
         33 . The method of  claim 30 , further comprising monitoring the reaction and detecting a signal from the released detectable label for determining the presence of a secreted target molecule. 
     
     
         34 . The method of  claim 33 , wherein monitoring each of the plurality of droplets comprises measuring at least one property associated with each of the plurality of droplets based on detection of signals from the one or more detectable labels with a detector. 
     
     
         35 . The method of  claim 34 , wherein the at least one property is an optical property. 
     
     
         36 . The method of  claim 35 , wherein the detector is at least one of an optical detector and a fluorescence detector. 
     
     
         37 . The method of  claim 36 , further comprising:
 detecting, with a fluorescence detector, an intensity of a fluorescent signal emitted from a detectable label; and/or   capturing, with an optical detector, one or more images of a fluorescent signal emitted from a detectable label.   
     
     
         38 . The method of  claim 19 , further comprising sorting the plurality of droplets into at least a first subset of droplets and a second subset of droplets, wherein each of the droplets of the first subset comprises no secreted target molecules and each of the droplets of the second subset comprises a secreted target molecule.