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GENE TRANSCRIPTION SIGNALING WITH A THICKNESS SHEAR MODE ACOUSTIC WAVE BIOSENSOR.  C.N. Jayarajah and M. Thompson.  Department of Chemistry, University of Toronto, Canada

   An on-line acoustic wave biosensor for the detection of in-vitro gene transcription is presented.  A piezoelectric crystal with a cold coating on which the DNA is immobilized functions as the sensor.  The thickness shear mode acoustic wave device is used here to distinguish the binding of surface immobilized strong and weak, and closed and open promoter DNA sequences to the T7 RNA polymerase.  Furthermore, the synthesis of mRNA on the sensor surface has been monitored. A two fold decrease in resonance frequency is observed in going from closed to open promoter in the absence of ribonucleotides.  In the presence of ribonucleotides, a four fold decrease in resonance frequency is observed. This change is accompanied by a significant increase in motional resistance.  The data obtained for the interaction of actinomycin-D with the promoter DNA in inhibiting transcription suggests that this drug molecule not only intercalates with double stranded DNA, but also binds strongly to single stranded DNA as demonstrated by a six fold decrease in resonance frequency.  This biosensor offers several advantages over conventional methods, such as label free detection in real time, and the generation of multidimensional data.  The multidimensional data obtained includes resonance frequency and motional resistance, which afford us information other than mass loading, such as changes in viscoelastic properties, surface charge and free energy, and conformation.  Moreover, the curves of resonance frequency as a function of time contain information on association and dissociation kinetics.  The results presented here suggest that this sensor is a viable technique to identify gravity dependent transcription factors, and to detect the effects of gravitational perturbation and other stress factors associated with space research on gene transcription.  This biosensor is also useful in detecting specific gene expression levels in organisms with relevance to astrobiology.

(Supported by NSERC, Canada)

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