Subdiffusive Molecular Motion in Nanochannels Observed by Fluorescence Correlation Spectroscopy

摘要

The influence of confinement on biomolecule motion innglass channels of nanometric height has been investigatednwith fluorescence correlation spectroscopy (FCS). Wenmeasured intrachannel molecule diffusion time and concentrationnbased on a single-component diffusion modelnas a function of molecule size to channel height (rg/h).nPoly(ethylene glycol) (PEG) of 20 kDa and dextran ofn40 kDa showed a reduction of their diffusion coefficientsnof almost 1 order of magnitude when nanochannelnheight approached probe diameter, whereas rhodaminen6G (Rh6G) was shown to be almost unaffectednfrom confinement. Subdiffusive motion has been provennfor flexible molecules in nanochannels, and deviationsntoward a square root dependence of mobility with timenfor confinement up to molecule size rg/h ∼ 0.5 werenregistered. Diffusion coefficient time dependence hasnbeen evaluated and described with a model that accountsnfor diffusion time increase due to moleculenrearrangements related to molecule flexibility andnsurface interactions dynamics. The evaluation of thensubdiffusive mode and the key parameters extractednat the single-molecule level of partitioning, intrachannelndiffusion time, desorption time, and binding probabilitynat surfaces can be exploited for the engineering ofnbioanalytic nanodevices.