Merck, C3657-5MG, Collagen from human placenta

Preparation Note
This product was prepared by a modification of the pepsin extraction and salt fractionation method of Niyibizi, C., et al., J. Biol. Chem., 259, 14170 (1984). It is an acid soluble collagen that can be dissolved in water with acetic acid added to pH 3.0 (5 mg/mL), yielding an opalescent, colorless solution.
Analysis Note
An SDS polyacrylamide gel electrophoresis test run under reducing conditions consistent with basement membrane collagen yields three major bands.
Other Notes
All collagen molecules are composed of three polypeptide chains arranged in a triple helical conformation, with a primary structure that is mostly a repeating motif with glycine in every third position and proline or 4-hydroxyproline frequently preceding the glycine residue.
Collagen is classified into a number of structurally and genetically distinct types. We use the nomenclature proposed by Bornstein and Traub. Be wary of confusing Sigma-type designations with recognized collagen classification types.
Disclaimer
This product should be stored desiccated at -20°C, and will retain activity in these conditions for 3 years.