The supramolecular organisation of fibrillin-rich microfibrils determines the mechanical properties of bovine zonular filaments.
The zonular filaments from the eyes of cows are rich in microfibrils containing fibrillin. Tensile tests, stress-relaxation tests and X-ray diffraction studies were used to study the relationship between the mechanical behaviour of zonular filaments and the molecular packing and structure of the fibrillin-rich microfibrils. Zonular filaments show a non-linear (J-shaped) stress-strain curve and appreciable stress-relaxation. It is proposed that the non-linear properties are due to local variations in waviness in the microfibrils or assemblies of microfibrils, which straighten out and become more regularly aligned with strain. Previous and current X-ray diffraction results consistently show a partial ordering of microfibrils in zonular filaments into staggered aggregates which become more ordered and laterally aligned on stretching. Although the removal and re-addition of Ca(2+) is known to change the molecular structure of fibrillin, no effect was observed on the tensile properties of the zonular filaments. It is hypothesised that strain-induced deformation in the supramolecular aggregate packing may not be Ca(2+)-sensitive but could dominate the mechanical behaviour of microfibrillar arrays in zonular filaments.
Wright
D M
DM
The Royal Veterinary and Agricultural University, Copenhagen, Denmark, School of Biosciences, Cardiff University, Cardiff CF1 3US, UK.
Duance
V C
VC
Wess
T J
TJ
Kielty
C M
CM
Purslow
P P
PP
D000818:Animals; D001696:Biomechanical Phenomena; D002118:Calcium / Q000008:administration & dosage; D002417:Cattle / Q000033:anatomy & histology*; D004548:Elasticity; D005123:Eye / Q000648:ultrastructure*; D000071837:Fibrillins; D020894:Microfibrils / Q000737:chemistry / Q000502:physiology* / Q000648:ultrastructure*; D008840:Microfilament Proteins / Q000648:ultrastructure*; D014961:X-Ray Diffraction
D000071837:Fibrillins; D008840:Microfilament Proteins; D002118:Calcium