A surface plasmon resonance based optical device for mass sensitive detection of biomolecular interactions at a chip surface was utilized for the first time for quantitative real-time analysis of the action of DNA manipulating enzymes, such as ligase, restriction nucleases and polymerases (1). Sequence-based DNA analysis, first introduced with oligonucleotide model systems, was extended to the scanning and screening for mutations in PCR amplified DNA from clinically relevant samples (2,3). The experimental set-up for mutation detection was further developed by the introduction of a subtractive mismatch sensitive hybridization outside the instrument and a subsequent determination of the relative amounts of remaining oligonucleotides with analytical biosensor monitoring of hybridizations between fully complementary oligonucleotides (4,5). In conclusion, the applied technology was found to be a suitable tool for a wide range of molecular biology applications, with emphasis on hybridization analysis and mutation detection.