title: Supramolecular synergy in the boundary lubrication of synovial joints.
abstract: Hyaluronan, lubricin and phospholipids, molecules ubiquitous in synovial joints, such as hips and knees, have separately been invoked as the lubricants responsible for the remarkable lubrication of articular cartilage; but alone, these molecules cannot explain the extremely low friction at the high pressures of such joints. We find that surface-anchored hyaluronan molecules complex synergistically with phosphatidylcholine lipids present in joints to form a boundary lubricating layer, which, with coefficient of friction μ≈0.001 at pressures to over 100 atm, has a frictional behaviour resembling that of articular cartilage in the major joints. Our findings point to a scenario where each of the molecules has a different role but must act together with the others: hyaluronan, anchored at the outer surface of articular cartilage by lubricin molecules, complexes with joint phosphatidylcholines to provide the extreme lubrication of synovial joints via the hydration-lubrication mechanism.
authors.affiliation: Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Jasmine
authors.initials: J
authors.lastname: Seror
authors.affiliation: 1] Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel [2] Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Linyi
authors.initials: L
authors.lastname: Zhu
authors.affiliation: Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Ronit
authors.initials: R
authors.lastname: Goldberg
authors.affiliation: Wellcome Trust Center for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Day
authors.affiliation: Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Jacob
authors.identifier: 0000000166020694
authors.initials: J
authors.lastname: Klein
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry; D019921:Biotinylation; D002358:Cartilage, Articular / Q000502:physiology; D017276:Friction; D006023:Glycoproteins / Q000737:chemistry* / Q000502:physiology; D006801:Humans; D006820:Hyaluronic Acid / Q000737:chemistry* / Q000502:physiology; D007596:Joints / Q000502:physiology; D008081:Liposomes / Q000737:chemistry; D008956:Models, Chemical; D010713:Phosphatidylcholines / Q000737:chemistry* / Q000502:physiology; D011312:Pressure; D013314:Stress, Mechanical; D013499:Surface Properties; D013582:Synovial Fluid / Q000737:chemistry* / Q000502:physiology; D000099158:Proteoglycan 4
chemical_list: D000538:Aluminum Silicates; D006023:Glycoproteins; D006820:Hyaluronic Acid; D008081:Liposomes; D010713:Phosphatidylcholines; D000099158:Proteoglycan 4; C011934:mica