Comparison of ESI-MS Spectra in MassBank Database

Metabolomics is one of the most important topics in biology and medical science. In metabolomics, metabolites from biological samples are measured by mass spectrometry (MS) and then identified by database searches for similar spectra. Since spectra from the same compound may differ depending on measurement conditions, comparison measure is a crucial issue for identifying compounds from their spectra. A standard method for comparison is normalized dot product or cosine correlation between spectral peaks. We discuss the weighting scheme for preprocessing peak intensities and demonstrate comparison results for about 9,000 spectra in our publicly available MassBank database (http://www. massbank.jp/).