Green fluorescent protein in the design of a living biosensing system for L-arabinose

Analysis of monosaccharides is typically performed using analytical systems that involve a separation step followed by a detection step, The separatio n step is usually necessary because of the high degree of structural simila rity between different monosaccharides, A novel sensing system for monosacc harides is described here in which living bacteria were designed to detect a model monosaccharide, L-arabinose, without the need for a separation step . In such sensing systems, analytes are detected by employing the selective recognition properties found in certain bacterial proteins. These systems are designed so that a reporter protein is expressed by the bacteria in res ponse to the analyte, The concentration of the analyte can be related to th e signal generated by the reporter protein, In the sensing system described here, the green fluorescent protein (GFP) was used as the reporter protein . L-Arabinose concentrations can be determined by monitoring the fluorescen ce emitted by the bacteria at 509 nm after excitation of GFP at 395 nm, The system can detect L-arabinose at concentrations as low as 5 x 10(-7) M and is selective over D-arabinose, the stereoisomer of the analyte, as well as over a variety of pentose and hexose sugars.