Electric Birefringence of Cartilage Proteoglycan and its Association with Hyaluronic Acid
Electric birefringence measurements are reported for dilute aqueous solutions of proteoglycans. Complicated birefringence transients obtained over a range of applied electric fields of up to 6 kV cm-1 amplitude are shown to be consistent with the presence of three discrete relaxation phenomena, involving different rate processes. Analysis of the relaxation times suggests that self-association of the proteoglycan molecules occurs in the form of dimers which appear to be of head-to-head form. Single proteoglycan molecules and dimers co-exist in solution and contribute independent components to the birefringence at relatively low field strengths. With high applied fields, a third birefringence component can be observed which is attributed to motion of the chondroitin sulphate side chains in the field. In the presence of hyaluronic acid the proteoglycan molecules form complexes which are consistent with the model in which proteoglycans attach radially to extended hyaluronic acid chains. Proteoglycan samples for which the cystine residues have been reduced and alkylated show no evidence of this association with hyaluronic acid indicating the importance of the conformation of the proteoglycan molecule in its ability to bind to hyaluronic acid.
KeywordsHyaluronic Acid Cartilage Proteoglycan Short Decay Time Electric Birefringence High Applied Field
Unable to display preview. Download preview PDF.
- 1.Muir H and Hardingham T E, in MTP International Review of Science Series I, Vol.5 (1975).Google Scholar
- 3.Atkins E D T, Hardingham T E, Isaac D H and Muir H, Biochem. J. 141, (1974) 919.Google Scholar
- 4.Hardingham T E and Muir H, Biochem. J., 135, (1973) 905.Google Scholar
- 5.Hardingham T E and Muir H, Biochem. J., 139, (1974) 565.Google Scholar
- 7.Hawkins E Y, Foweraker A R and Jennings B R, Polymer, 19, (1978) 1233.Google Scholar
- 9.Hardingham T E, Ewins R J F and Muir H, Biochem. J., 157, (1976) 127.Google Scholar
- 10.Wells P J and Serafini-Fracassini A, Nature, New Biology, 243, (1975) 266.Google Scholar
- 11.Sheehan J K, Nieduszynski I A, Phelps C F, Muir H and Hardingham T E, Biochem. J., 171, (1978) 109.Google Scholar
- 12.Isles M, Foweraker A R, Jennings B R, Hardingham T and Muir H, Biochem. 173, 173, (1978) 237.Google Scholar
- 13.Hascall V C and Heinegard D, J. Biol. Chem., 249, (1974) 4242.Google Scholar
- 14.Rosenberg L, Hellman W and Kleinschmidt A K, J. Biol. Chem., 250, (1975) 1877.Google Scholar