Physics Homework: Fluorescence Lifetime Imaging, Single Molecule Spectroscopy, and FRET, Assignments of Physics

Download Physics Homework: Fluorescence Lifetime Imaging, Single Molecule Spectroscopy, and FRET and more Assignments Physics in PDF only on Docsity! Homework#3 Physics598OS page 1/2 Due October 18, 2005 1) FLI – Fluorescence Lifetime Imaging a) Starting from the result for frequency domain: show that Give the shape of the single lifetime curve. (Hint split r into x and y. Use the single lifetime formula for phase and mod ) b) Solve the measured phase and modulation for a two component system with an intensity ratio between the two single lifetime components of a. If both lifetimes are known, what is a in terms of the measured phase, mod, and the lifetimes? c) Give a relationship between the phase and the modulation for a single lifetime (frequency and the lifetime should not appear in the relation). d) How many independent parameters of the lifetime distribution function, I, can be found with only one frequency domain measurement? How can one make a new measurement to get more parameters (what varies)? How many measurements would be required to solve a two single lifetime system? A Gaussian distribution? Three single lifetimes with one known lifetime? 2) Single Molecule Spectroscopy a) Why photon-bunching is a characteristic of only single molecule excitation? Does the ensemble excitation/emission show photon-bunching? Why? b) There is another interesting phenomenon called “photon-antibunching”, which is a characteristic of single molecule fluorescence emission as well. In your own word, explain what it is and why two opposite things occur on the same system? c) From Orrit M. and Bernard J. PRL 1990 v.65 p.2716, the FWHM of the excitation peak from a single molecule is ~ 12 MHz, what is the FWHM of the excitation peak of fluorescein in solution? sin ( ) ( ) sin ( ) cos ( ) ( ) cos ( ) tot tot tot tot M I M d M I M d j t t j t t j t t j t t = = ò ò ( ) ( )totr I r dt t t= ò v v