Molecular aggregation characterized by high order autocorrelation in fluorescence correlation spectroscopy.
The use of high order autocorrelation in fluorescence correlation spectroscopy for investigating aggregation in a sample that contains fluorescent molecules is described. Theoretical expressions for the fluorescence fluctuation autocorrelation functions defined by gm,n(tau) = [(delta fm(t + tau)delta fm(t] - (delta Fm(t] (delta Fn(t]]/(F)m+n, where delta F(t) is the fluorescence fluctuation at time t, (F) is the average fluorescence, and m and n are integers less than or equal to 3, are derived. Methods for determining the number densities and relative fluorescence yields of aggregates of different sizes from a series of Gm,n(0) values are outlined. The method is applied to 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate suspended in solutions of water and ethyl alcohol. The technique presented may prove useful in detecting and characterizing aggregates of fluorescent-labeled biological molecules such as cell surface receptors.
Palmer
A G
AG
Department of Chemistry, University of North Carolina at Chapel Hill 27514.
Thompson
N L
NL
D002232:Carbocyanines; D005456:Fluorescent Dyes; D046911:Macromolecular Substances; D008433:Mathematics; D008962:Models, Theoretical; D008968:Molecular Conformation; D011804:Quinolines; D013050:Spectrometry, Fluorescence / Q000379:methods
D002232:Carbocyanines; D005456:Fluorescent Dyes; D046911:Macromolecular Substances; D011804:Quinolines; C024286:3,3'-dioctadecylindocarbocyanine