%0 Journal Article
%T Inexpensive hardware and software for photon statistics and correlation spectroscopy
%A Benjamin D. Gamari
%A Dianwen Zhang
%A Richard E. Buckman
%A Peker Milas
%A John S. Denker
%A Hui Chen
%A Hongmin Li
%A Lori S. Goldner
%J Physics
%D 2012
%I arXiv
%X Single-molecule sensitive microscopies and spectroscopies are transforming biophysics and materials science laboratories. Techniques such as fluorescence correlation spectroscopy (FCS) and single-molecule sensitive fluorescence resonance energy transfer (FRET) are now commonly available in research laboratories but are as yet infrequently available in teaching laboratories. We describe inexpensive electronics and open-source software that bridges this gap, making state-of-the-art measurement research capabilities accessible to undergraduates interested in biophysics. We include a pedagogical discussion of the intensity correlation function relevant to FCS and its calculation directly from photon arrival times. We demonstrate the system with a measurement of the hydrodynamic radius of a protein using FCS that is suitable for an undergraduate teaching laboratory. The FPGA-based electronics, which are easy to construct, are suitable for more advanced measurements as well, and several applications are demonstrated. As implemented, the system has 8 ns timing resolution, outputs to control up to four laser sources, and inputs for as many as four photon-counting detectors.
%U http://arxiv.org/abs/1206.3332v2