As the demand for large-scale analysis of gene expres- sion using DNA arrays increases, the importance of the surface characterization of DNA arrays has emerged. We com- pared the efficiency of molecular biological applications on solid-phases with different surface polarities to identify the most optimal conditions. We employed thiol-gold reactions for DNA immobilization on solid surfaces. The surface polarity was controlled by creating a self-assembled monolayer (SAM) of mercaptohexanol or hepthanethiol, which create hydrop- hilic or hydrophobic surface properties, respectively. A hyd- rophilic environment was found to be much more favorable to solid-phase molecular biological manipulations. A SAM of mercaptoethanol had the highest affinity to DNA mole- cules in our experimetns and it showed greater efficiency in terms of DNA hybridization and polymerization. The opti- mal DNA concentration for immobilization was found to be 0.5 mM. The optimal reaction time for both thiolated DNA and matrix molecules was 10 min and for the polymerase reaction time was 150 min. Under these optimized condi- tions, molecular biology techniques including DNA hybri- dization, ligation, polymerization, PCR and multiplex PCR were shown to be feasible in solid-state conditions. We de-monstrated from our present analysis the importance of surface polarity in solid-phase molecular biological appli- cations. A hydrophilic SAM generated a far more favorable envi- ronment than hydrophobic SAM for solid‐state molecular techniques. Our findings suggest that the conditions and met- hods identified here could be used for DNA‐DNA hybri- dization applications such as DNA chips and for the further development of solid-phase genetic engineering applicatio- ns that involve DNA-enzyme interactions.

The influence of the polarity of the spreading solvent on the properties of the monolayer of poly(styrene-co-acrylonitrile)'s with various acrylonitrile contents was studied. The surface pressure - area isotherm and the apparent dipole moment - area isotherm were obtained and analyzed when the mixtures of methylene chloride and N-N-dimethylformamide used as spreading solvent. The isotherms were strongly influenced by the polarity of the solvent.