Conjugated Polymers Combined with a Molecular Beacon for Label‐Free and Self‐Signal‐Amplifying DNA Microarrays

A conjugated polymer (CP) and molecular‐beacon‐based solid‐state DNA sensing system is developed to achieve sensitive, label‐free detection. A novel conjugated poly(oxadiazole) derivative exhibiting amine and thiol functional groups ( POX‐SH ) is developed for unique chemical and photochemical stability and convenient solid‐state on‐chip DNA synthesis. POX‐SH is soluble in most nonpolar organic solvents and exhibits intense blue fluorescence. POX‐SH is covalently immobilized onto a maleimido‐functionalized glass slide by means of its thiol group. Molecular beacons having a fluorescent dye or quencher molecule as the fluorescence resonance energy transfer (FRET) acceptor are synthesized on the immobilized POX‐SH layer through direct on‐chip oligonucleotide synthesis using the amine side chain of POX‐SH . Selective hybridization of the molecular beacon probes with the target DNA sequence opens up the molecular beacon probes and affects the FRET between POX‐SH and the dye or quencher, producing a sensitive and label‐free fluorescence sensory signal. Various molecular design parameters, such as the size of the stem and loop of the molecular beacon, the choice of dye, and the number of quencher molecules are systematically controlled, and their effects on the sensitivity and selectivity are investigated.     

THE EFFECT OF PRETREATMENT CONDITIONS ON THE FTS ACTIVITY AND SELECTIVITY OF CHARCOAL AND TITANIA SUPPORTED MOLYBDENUM CATALYSTS

The effects of pretreatment conditions and potassium promotion on the activities and selectivities of charcoal and titania supported molybdenum were investigated. It was found that perhaps the most important variables are the reduction time, and temperature. Optimum reduction conditions were four hours at 773 K. Shorter times and lower temperatures lead to dramatically reduced activity. The order of potassium addition as a promoter was also found to be very important. Loading of potassium before molybdenum loading leads to the most efficient use of potassium in terms of higher selectivities.