S100 is a small dimeric protein with a molecular weight of approximately 10.5 kD, and belongs to a multigenic family of calcium‑binding proteins. S100A1 (α) and S100B (β) were the first members described, originally isolated as an unfractionated mixture by Moore 3 from bovine brain and named S100 after its solubility in a 100 % saturated ammonium sulfate solution. In the meantime, at least 21 different members of the S100 family have been identified.
S100A1 and S100B are predominantly expressed by cells of the central nervous system, mainly astroglial cells, but are also expressed in melanoma cells and to some extent in other tissues. The functional protein, which is composed of hetero - or homodimers of A1 and B, is implicated in a variety of intra - and extracellular regulatory activities.
In patients suffering from malignant melanoma, especially stage II, III, and IV, elevated S100 serum levels may indicate disease progression. Serial measurements can be useful for follow‑up and monitoring therapy success in these patients. In addition, levels of S100 rise in the CSF (cerebro‑spinal fluid) and are released in peripheral blood after a variety of cerebral lesions. S100 can be detected in patients with cerebral damage caused by several events, e.g. traumatic brain injuries or stroke.
SI units Conversion Calculator. Convert S100 level to ng/mL, ng/dL, ng/100mL, ng%, ng/L, µg/L. Clinical laboratory units online conversion from conventional or traditional units to Si units. Table of conversion factors for S100 unit conversion to ng/mL, ng/dL, ng/100mL, ng%, ng/L, µg/L.