Segment Distributions of End-tethered Polymers in a Good Solvent

We use confocal fluorescence microscopy to study the conformation of single DNA molecules end-tethered to a solid substrate. The segment distribution rho(z) measured for chains with contour lengths 15.4 microm <or= L <or= 59.4 microm as a function of the distance from the substrate can be scaled onto a master curve depending only on the scaled distance z/R(g), in quantitative agreement with theoretical predictions for end-tethered polymers in a good solvent. The scaling of the radius of gyration R(g) approximately L(0.57+/-0.05) shows the presence of excluded-volume interactions between the charged DNA segments. Independent measurements of R(g) from end-segment distributions are in good agreement with values obtained from the segment distributions and provide evidence that the radius of gyration of end-tethered chains in a good solvent is identical to that of the free chain.