Collagen fibrils in bone are crosslinked with?
Correct answer : D. Pyridinium
Molecular structure of pyridinium
Collagen fibrils in bone are cross-linked with pyridinium. It increases bone strength. During bone resorption by osteoclasts, these cross-links are released. They act as biochemical markers of bone resorption. Pyridinium cross-links can be detected in urine.
Collagen fibers – Electron microscopy
Ref: Davidson’s Principles and Practice of Medicine, 22nd Edition, p1062.
Related journal article: Urinary excretion of pyridinium crosslinks of collagen in patients with osteoporosis and the effects of bone fracture. A M McLaren, L D Hordon, H A Bird and S P Robins. Ann Rheum Dis. 1992 May; 51(5): 648–651. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1005699/