Manipulation of single DNA molecules in globular state: recovery into capillary and direct laser trapping

A novel micro-manipulation method has been developed for large chromosomal single DNA molecules which are easily cut by shearing stress in solution. For genome analysis, the manipulation technique is very important, and will contribute to enhance speed and accuracy. The transformation into globular structure is effective to suppress the fragmentation. The transformation is reversible between the globular state and the random coil state, depending on the concentration of solution. The authors utilized the transformation to manipulate single large DNA molecules. Recovery of a transformed globular yeast chromosomal DNA has been demonstrated. A large globular DNA molecule can be transported by recovering into a glass capillary. The fragmentation can be eliminated effectively. The authors also confirmed, for the first time, that a globular DNA could be trapped and transported. The direct laser-trapping of a DNA molecule is possible even for a smaller DNA molecules such as T4 phage by a YAG laser of 180 mW