MatrixDB stores experimental data established by full-length proteins, matricryptins, glycosaminoglycans, lipids and cations. MatrixDB reports interactions with individual polypeptide chains or with multimers (e.g. collagens, laminins, thrombospondins) when appropriate. Multimers are treated as permanent complexes, referencing EBI identifiers when possible. Human interactions were inferred from non-human homologous interactions when available.