Two- and three-dimensional image analysis in bioanalytical measurement systems

Statistics of DNA single molecule dynamics in DC electrophoresis systems were used to predict ensemble electrophoretic migration times and overall band shapes. Migration times are predicted adequately and the asymmetric band shapes observed in electrophoresis are mirrored in asymmetric migration time distributions of single molecules. The proper scaling relation is not known so it is not been possible to establish whether or not the data accurately predicts bandwidth from single DNA molecule dynamics. Similar successes and limitations are observed for field inversion electrophoresis. Sample size studies show that the range of possibilities for DNA motions is limited and much of it is explored rapidly.; The first three-dimensional (3-D) description of DNA electrophoretic migration is reported. The assumption of uniform probability of out of plane orientations, frequently made for DNA migration theory, has been verified. However the use of apparent two dimensional (2-D) opening angles underestimates the true behavior. An extension of the Oana/Doi ellipsoidal approximation to DNA dimensions is used for quantitative descriptions. Although several limitations of the 3-D ellipsoid approximation are pointed out, it is sufficient for DNA migration image analysis.; Scanning electron microscopy (SEM) and extended focus (EF) light microscopy were used for acquiring surface images of electrochemical surface enhanced Raman spectroscopy (SERS) substrates. Self-similarity was found from 30 mum to 100 nm and was used to define an optimum fractal dimension for SERS activity, approximately 1.7. The activity thresholds found by both SEM and EF light microscopy are similar. Therefore, EF microscopy can be used to assess the quality of an electrode surface before it is irrevocably committed to an experiment.