Laser microdissection of metaphase chromosomes and characterization by atomic force microscopy.

A new experimental setup has been constructed in which a UV laser microbeam and atomic force microscopy (AFM) have been combined on an inverted microscope in order to manipulate and visualize chromosomes with high resolution. The laser beam has been used to dissect Muntjak metaphase chromosomes and was aimed to optimize the physical size of the cuts. The capability of the AFM to visualize biological material with relative ease has been used to characterize the microdissected chromosomes. This work demonstrates that chromosome fiber material can be removed completely at the cut site using appropriate laser power. The minimum cut size achieved with a 337-nm nitrogen UV laser was between 600 and 800 nm. The smallest distance between the cuts was around 500 nm, corresponding to the finest probe for further biochemical use after physical translocation such as the polymerase chain reaction. Limitations on minimizing the cut size due to diffraction-limited focusing and the effects of laser ablation of biomaterial are discussed. © 1997 Society of Photo-Optical Instrumentation Engineers.