NEW POLYACRYLAMIDE GEL-BASED METHODS OF SAMPLE PREPARATION FOR OPTICAL MICROSCOPY - IMMOBILIZATION OF DNA-MOLECULES FOR OPTICAL MAPPING

New methods have been developed for rapid immobilization of biological macromolecules and other microscopic objects from aqueous solution at gel/gel, gel/solid and gel/solution interfaces using thin polyacrylam ide gels covalently bound to glass surfaces, When quickly spread over a dry gel, an aqueous sample loses most of its water and low-molecular -weight solutes due to migration of these components into the gel, All optically observable objects thus become concentrated at the gel surf ace and may be easily located by light microscopy, Based on this, a pr ocedure for binding DNA at a positively charged gel/solution interface was developed, A mild immobilization of the DNA molecules was obtaine d, allowing 'all in focus' observations of DNA digestion by restrictio n endonucleases with an apparent rate close to that in solution.