ABSTRACT
Nanodissection of single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) has been investigated by atomic force microscopy (AFM). It is found that both ss- and dsDNA can be repeatedly dissected by an AFM tip. However, a comparison study indicates that ssDNA is a little bit more easily broken by the AFM tip than dsDNA. This is supported by the fact that the time requested to break ssDNA is shorter than that of dsDNA in the same dissection procedure under the same load. Our experiment also shows that dissection of the DNA strand is very sensitive to the load applied, and a small change of the load lead to different results.
Subject(s)
DNA/chemistry , DNA/ultrastructure , Microchemistry/methods , Microdissection/methods , Micromanipulation/methods , Microscopy, Atomic Force/methods , Nanotechnology/methods , DNA/isolation & purification , Materials Testing/methods , Particle Size , Physical Stimulation/methods , Stress, MechanicalABSTRACT
The radial compression properties of single DNA molecules have been studied using vibrating scanning polarization force microscopy. By imaging DNA molecules at different vibration amplitude set-point values, we obtain the correlations between radially applied force and DNA compression, from which the radial compressive elasticity can be deduced. The estimated elastic modulus is approximately 20-70 MPa under small external forces (<0.4 nN) and increases to approximately 100-200 MPa for large loads.
Subject(s)
DNA/chemistry , DNA/ultrastructure , Micromanipulation/methods , Microscopy, Atomic Force/methods , Microscopy, Polarization/methods , Models, Chemical , Models, Molecular , Compressive Strength , Computer Simulation , DNA/analysis , Elasticity , Image Interpretation, Computer-Assisted/methods , Nucleic Acid Conformation , Stress, Mechanical , VibrationABSTRACT
Recently, the isolation and biochemical analysis of DNA at the single-molecule level has been recognized as very important for genetic research and clinical analysis. A unique technique for the positioning, dissection, and isolation of single DNA molecules using atomic force microscopy (AFM) has been demonstrated. Full-length genome DNA molecules were first deposited and stretched by a modified "molecular combing" technique onto a 3-aminopropyl triethoxysilane-coated mica substrate. A single DNA fragment was dissected from one of those genome DNA strands with the AFM tip at the desired position, and then isolated (or picked up) after a special operation called "kneading". All the operations including imaging, dissection, and isolation could be carried out with one tip. The isolated DNA fragment on the AFM tip could be successfully amplified by single-molecule PCR.
