Abstract
Following removal of most of the telopeptide regions with pepsin, bovine dermal collagen gelled more slowly to form fibrils with a weak banding pattern. The reduction in gelling rate reflected an increase in the length of the nucleation phase and a lower rate of turbidity increase during the growth phase; the activation energy of both phases was increased. Lanthanide ions, phosphate, or, to a lesser degree, Ca2+ restored higher gelling rates to pepsin-treated collagen, but were unable to improve the banding pattern. Only lanthanide ions were able to accelerate the polymerization of intact collagen, lowering the activation energies of both the nucleation and growth phases. Lanthanide ions and phosphate also improved the banding characteristics of fibrils formed from intact collagen, without changing their width. Luminescence studies confirmed the direct binding of Tb3+ to collagen and suggested that the lanthanide ions may mediate their effects on fibrillogenesis by attaching to the helical part of the molecule. Quantitative considerations indicate that five or less lanthanide ion-binding sites per collagen molecule may be involved in the promotion of fibril formation.
Highlights
Following removal of most ofthe telopeptide regions whengrowth has ceased, the collagen molecules with pepsin, bovine dermal collagen gelled more slowly within the fibrils form covalent cross-links which render the to form fibrils with a weak banding pattern
Collagen Polymerization-Preparation of collagen and lanthanide involves linear growth to form filamentswhich subsequently solutions has been described in Ref. 16.Gelling curves were analyzed aggregate laterally into fibrils during thegrowth phase [6,7,8]. by reference to threeparameters: the length of the nucleation phase
Fluorescence at 545 nm (@); t, (0)dA;/dt (m). These data confirm the importance of the telopeptide regions to both the qualitativeandquantitativeaspects of collagen fibrillogenesis
Summary
From the OrthopaedicResearch Laboratory, University of Pittsburgh, School of Medicine, Pittsburgh, Pennsylvania I5261. Numerous studies(e.g.2 , 4 , 5 ) attest to thseigmoidal nature of the increase in turbidity with time thaot ccurs as collagen solutions polymerize Descriptions of such gelling curves usually make reference to the nucleation or lag phase,during which there is little change in turbidity, and the subsequent (approximately 3 mg/ml) in 10 mM HCI. Collagen Polymerization-Preparation of collagen and lanthanide involves linear growth to form filamentswhich subsequently solutions has been described in Ref. 16.Gelling curves were analyzed aggregate laterally into fibrils during thegrowth phase [6,7,8]. L The abbreviations used are: p-collagen, pepsin-treated collagen; To whom correspondence should be addressed Orthopaedic Re- i-collagen, intact collagen; SDS, sodium dodecyl sulfate; PAGE, polsearch Laboratory, 986 Scaife Hall, University of Pittsburgh, School yacrylamide gel electrophoresis; Pipes, 1,4-piperazinediethanesulof Medicine, Pittsburgh, PA 15261. Excitation (250-350 nm) and emission (300-600 nm) spectra were recorded with a Perkin-Elmerfluorescence spectrophotometer Model 650-10s
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