Biomedical subjects

K Varmuza

Publications and source records attributed to K Varmuza.

4 recordsLinked to original sources

PubMed2003

Systematic toxicological analysis: computer-assisted identification of poisons in biological materials.

A new software was developed to improve the chances for identification of a "general unknown" in complex biological materials. To achieve this goal, the total ion current chromatogram was simplified by filtering the acquired mass spectra via an automated subtraction procedure, which removed mass spectra originating from the sample matrix, as well as interfering substances from the extraction procedure. It could be shown that this tool emphasizes mass spectra of exceptional compounds, and therefore provides the forensic toxicologist with further evidence-even in cases where mass spectral data of the unknown compound are not available in "standard" spectral libraries.

Body Fluids↗

PubMed2001

Characteristic substructures in sets of organic compounds with similar infrared spectra.

A method based on the determination of maximum common substructures is applied for the generation of substructures which are characteristic for a given set of molecular structures. The molecular structures are from hitlists obtained by spectral library searches; the hitlists contain those reference compounds, which have infrared spectra most similar to that from the query compound. The influences of various parameters of this method are investigated with the aim to improve the relevance of the obtained substructures for the structure of the query compound.

Journal Article↗

PubMed2000

Substructure isomorphism matrix

A substructure isomorphism matrix n x p contains binary elements describing which of the given p query structures (substructures) are part of the given n target structures (molecular structures). Such a matrix can be used to investigate the diversity of the target structures and allows the characterization and comparison of structural libraries. A quadratic substructure isomorphism matrix n x n is obtained if the same structures are used as molecular structures and as substructures; this matrix contains full information about the topological hierarchy of the n structures. A hierarchical arrangement of chemical structures is useful for the evaluation of results obtained from searches in structure databases.

Journal Article↗

PubMed1995

MS-UTIL: a program for interpretation and manipulation of mass spectra and chemical structures.

A computer program for personal computers has been developed, which enables the user of interpret fragmentation processes in electron impact mass spectrometry more easily. Starting with a low resolution mass spectrum and a selected chemical structure, fragments of the molecule which are related to the spectral data can be created interactively. Some frequently occurring fragmentation reactions can be performed automatically. An included editor allows the user to draw chemical structures and to create or modify mass spectra. Fragments of a molecule can be displayed as a tree. One aim of the program is to facilitate learning of fragmentation reactions. Furthermore, the program serves as a tool for verifying fragmentation mechanisms proposed and for checking presumptive chemical structure formulas of unidentified compounds.

Image Interpretation, Computer-Assisted↗