COVALENT BINDING OF BIOLOGICAL SAMPLES TO SOLID SUPPORTS FOR SCANNINGPROBE MICROSCOPY IN BUFFER SOLUTION

Scanning force microscopy allows imaging of biological molecules in th eir native state in buffer solution. To this end samples have to be fi xed to a flat solid support so that they cannot be displaced by the sc anning tip. Here we describe a method to achieve the covalent binding of biological samples to glass surfaces. Coverslips were chemically mo dified with the photoactivatable cross-linker N-5-azido-2-nitrobenzoyl oxysuccinimide. Samples are squeezed between derivatized coverslips an d then cross-linked to the glass surface by irradiation with ultraviol et light. Such samples can be imaged repeatedly by the scanning force microscope without loss; of image quality, whereas identical but not i mmobilized samples are pushed away by the stylus.