title: Simulation of single-molecule trapping in a nanochannel.
abstract: The detection and trapping of single fluorescent molecules in solution within a nanochannel is studied using numerical simulations. As optical forces are insufficient for trapping molecules much smaller than the optical wavelength, a means for sensing a molecule's position along the nanochannel and adjusting electrokinetic motion to compensate diffusion is assessed. Fluorescence excitation is provided by two adjacently focused laser beams containing temporally interleaved laser pulses. Photon detection is time-gated, and the displacement of the molecule from the middle of the two foci alters the count rates collected in the two detection channels. An algorithm for feedback control of the electrokinetic motion in response to the timing of photons, to reposition the molecule back toward the middle for trapping and to rapidly reload the trap after a molecule photobleaches or escapes, is evaluated. While accommodating the limited electrokinetic speed and the finite latency of feedback imposed by experimental hardware, the algorithm is shown to be effective for trapping fast-diffusing single-chromophore molecules within a micron-sized confocal region. Studies show that there is an optimum laser power for which loss of molecules from the trap due to either photobleaching or shot-noise fluctuations is minimized.
authors.affiliation: University of Tennessee Space Institute, Center for Laser Applications, Tullahoma, Tennessee TN 37388, USA.
authors.forename: William Neil
authors.initials: WN
authors.lastname: Robinson
authors.forename: Lloyd M
authors.initials: LM
authors.lastname: Davis
mesh_terms: D001704:Biopolymers / Q000302:isolation & purification* / Q000528:radiation effects*; D003198:Computer Simulation; D008027:Light; D008846:Micromanipulation / Q000379:methods*; D008956:Models, Chemical; D043942:Nanotubes / Q000737:chemistry* / Q000648:ultrastructure*; D052898:Optical Tweezers
chemical_list: D001704:Biopolymers
references.citation: Proc Natl Acad Sci U S A. 2007 Jul 31;104(31):12596-602
references.pmid: 17664434
references.citation: Anal Chem. 2003 Dec 1;75(23):6634-41
references.pmid: 14640739
references.citation: Cell Biochem Biophys. 2007;48(1):1-15
references.pmid: 17703064
references.citation: Biopolymers. 2007 Feb 5;85(2):131-43
references.pmid: 17103421
references.citation: Appl Opt. 1998 Apr 20;37(12):2315-26
references.pmid: 18273158
references.citation: Curr Pharm Biotechnol. 2006 Aug;7(4):287-301
references.pmid: 16918405
references.citation: Opt Express. 2005 Oct 3;13(20):8069-82
references.pmid: 19498837
references.citation: Annu Int Conf IEEE Eng Med Biol Soc. 2009;2009:1396-9
references.pmid: 19964522
references.citation: Microsc Res Tech. 2004 Jan 1;63(1):34-49
references.pmid: 14677132
references.citation: Biotechnol Bioeng. 1990 Feb 20;35(4):327-38
references.pmid: 18592527
references.citation: Curr Pharm Biotechnol. 2003 Dec;4(6):451-62
references.pmid: 14683437
references.citation: Biophys J. 2001 Jun;80(6):2987-99
references.pmid: 11371471
references.citation: Opt Express. 2008 May 12;16(10):6941-56
references.pmid: 18545398
references.citation: Anal Chem. 2008 Dec 15;80(24):9830-4
references.pmid: 19072277
references.citation: Biophys J. 2002 Jun;82(6):3314-29
references.pmid: 12023254
references.citation: Proc Natl Acad Sci U S A. 1997 May 13;94(10):4853-60
references.pmid: 9144154
references.citation: Phys Rev Lett. 2005 Mar 25;94(11):118102
references.pmid: 15903893