FIG. 4.
Concentrations of collagen measured by the hydroxyproline assay using DMAB dissolved in 30% HClO4 or HCl plus 70% isopropanol. Source tissues, which were differentially treated, included native (n = 16) or engineered (n = 36) bovine cartilage and leporine tissues (n = 4). The leporine tissues included, in ascending order of collagen concentration, liver, testis, meniscus, and tendon. Aliquots of each tissue digest were diluted with a variable amount of excess papain solution to a volume of 100 μL to achieve concentrations of collagen within the limits of the assay standard curve. There was excellent concordance (ρc = 0.976) between collagen concentrations measured using HClO4 or HCl.