title: Signal enhancement by a multi-layered substrate for mutagen detection using an SOS response-induced green fluorescent protein in genetically modified Escherichia coli.
abstract: In this paper, we describe a method to enhance the fluorescence signal of mutagen detection using SOS response-induced green fluorescence protein (GFP) in genetically modified Escherichia coli using a multi-layered substrate.  To generate E. coli that express SOS response-induced GFP, we constructed a plasmid carrying the RecA promoter located upstream of the GFP gene and used it to transform E. coli BL21.  The transformed strain was incubated with mitomycin C (MMC), a typical mutagen, and then immobilized on a multi-layered substrate with Ag and a thin Al(2)O(3) layer on a glass slide.  Since the multi-layered substrate technique is an optical technique with potential to enhance the fluorescence of fluorophore placed on top of the substrate, the multi-layered substrate was expected to improve the fluorescence signal of mutagen detection.  We obtained an average 14-fold fluorescence enhancement of MMC-induced GFP in the concentration range 1 to 1000 ng/ml.  In addition, the lower detection limit of MMC was improved using this technique, and was estimated to be 1 ng/ml because of an enlargement of the difference between the blank and the signal of 1 ng/ml of MMC.
authors.affiliation: School of Bioscience and Biotechnology, Tokyo University of Technology, 1404-1 Katakura, Hachiouji, Tokyo 192–0982, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Etoh
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Yasuda
authors.forename: Takuo
authors.initials: T
authors.lastname: Akimoto
mesh_terms: D004926:Escherichia coli / Q000235:genetics*; D049452:Green Fluorescent Proteins / Q000235:genetics*; D057230:Limit of Detection; D016685:Mitomycin / Q000032:analysis* / Q000633:toxicity; D009153:Mutagens / Q000032:analysis* / Q000633:toxicity; D010957:Plasmids; D011401:Promoter Regions, Genetic; D011938:Rec A Recombinases / Q000235:genetics; D013014:SOS Response, Genetics; D013050:Spectrometry, Fluorescence
chemical_list: D009153:Mutagens; D049452:Green Fluorescent Proteins; D016685:Mitomycin; D011938:Rec A Recombinases