A MAXIMUM-LIKELIHOOD ESTIMATOR TO DISTINGUISH SINGLE MOLECULES BY THEIR FLUORESCENCE DECAYS

We have developed a maximum likelihood estimator to distinguish betwee n similar molecules at the single molecule level based upon fluorescen ce decay measurements. Time-resolved fluorescence measurements for sin gle Rhodamine 6G and tetramethylrhodamine isothiocyanate molecules in fluid flow are derived from time-correlated single photon counting. A maximum likelihood estimator is developed and applied to data from a m ixture of molecules. Single molecules are identified and distinguished by their fluorescence time decays. Comparison is made between identif ication error rates and theoretical predictions. To our knowledge, thi s is the first reported example of single molecule identification by f luorescence decay in a mixture.