title: Imaging stretched single DNA molecules by pulsed-force-mode atomic force microscopy.
abstract: The effect of a surface water layer on DNA strands deposited on a substrate was studied by atomic force microscopy (AFM). DNA molecules were deposited and stretched on chemically modified glass coverslips by a molecular combing method. Lambda bacteriophage DNA molecules were aligned on the organosilane-modified substrate surfaces by chemical and physical adsorption during the molecular combing. The combed DNA molecules were observed in humidity-controlled air and in aqueous solutions by pulsed-force-mode AFM (PFM-AFM). Chemical modification of cantilevers with an Au-coated tip by organothiol compounds was also applied to DNA observation. Mapping adhesive forces in aqueous media was useful to discriminate chemically the DNA strands from the substrate surface. The results suggest that PFM-AFM can be used widely to image the stretched DNA molecules on the silane-modified substrates.
authors.affiliation: Department of Biomolecular Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan.
authors.forename: K J
authors.initials: KJ
authors.lastname: Kwak
authors.forename: H
authors.initials: H
authors.lastname: Kudo
authors.forename: M
authors.initials: M
authors.lastname: Fujihira
mesh_terms: D000327:Adsorption; D000388:Air; D010582:Bacteriophage lambda / Q000235:genetics*; D001583:Benzoxazoles / Q000378:metabolism; D004279:DNA, Viral / Q000737:chemistry / Q000235:genetics / Q000648:ultrastructure*; D005821:Genetic Techniques; D006813:Humidity; D018625:Microscopy, Atomic Force / Q000379:methods*; D008856:Microscopy, Fluorescence; D011806:Quinolinium Compounds / Q000378:metabolism; D012821:Silanes; D012996:Solutions; D013499:Surface Properties
chemical_list: D001583:Benzoxazoles; D004279:DNA, Viral; D011806:Quinolinium Compounds; D012821:Silanes; D012996:Solutions; C075296:1,1'-((4,4,7,7-tetramethyl)-4,7-diazaundecamethylene)bis-4-(3-methyl-2,3-dihydro(benzo-1,3-oxazole)-2-methylidene)quinolinium