RESUMEN

As one of the most crucial properties of DNA, the structural stability and the mechanical strength are attracting a great attention. Here, we take advantage of high force resolution and high special resolution of Atom Force Microscope and investigate the mechanical force of DNA duplexes. To evaluate the base pair hydrogen bond strength and base stacking force in DNA strands, we designed two modes (unzipping and stretching) for the measurement rupture forces. Employing k-means clustering algorithm, the ruptured force are clustered and the mean values are estimated. We assessed the influence of experimental parameters and performed the force evaluation for DNA duplexes of pure dG/dC and dA/dT base pairs. The base binding strength of single dG/dC and single dA/dT were estimated to be 20.0 ± 0.2 pN and 14.0 ± 0.3 pN, respectively, and the base stacking interaction was estimated to be 2.0 ± 0.1 pN. Our results provide valuable information about the quantitative evaluation of the mechanical properties of the DNA duplexes.

Asunto(s)

RESUMEN

Random drift and faulty visual display are the main problems in Atomic Force Microscopy (AFM) based robotic nanomanipulation. As far as we know, there are no effective methods available to solve these problems. In this paper, an On-line Sensing and Display (OSD) method is proposed to solve these problems. The OSD method mainly includes two subprocesses: Local-Scan-Before-Manipulation (LSBM) and Local-Scan-After-Manipulation (LSAM). During manipulation, LSBM and LSAM are on-line performed for random drift compensation and faulty visual display correction respectively. Through this way, the bad influence aroused from random drift and faulty visual display can be eliminated in real time. The visual feedback keeps consistent with the true environment changes during the process of manipulation, which makes several operations being finished without an image scan in between. Experiments show the increased effectiveness and efficiency of AFM based nanomanipulation.