Organization of collagen in the presence of diphenyl phosphoryl azide (DPPA): An in vitro study

Collagen, an important fibrous protein and its stability is closely related to organizational order. In this work, organization of collagen in the presence of diphenyl phosphoryl azide (DPPA) was studied using circular dichroic spectroscopy, stress–strain characteristics and fibrillogenesis. The reconstituted collagen fibrils in the presence of DPPA were characterized using Fourier transform infrared spectroscopy, differential scanning calorimetry, X-ray diffraction and polarizing light microscopy. CD spectra show that the secondary structure of the collagen molecule is preserved when the concentrations of DPPA is less than 0.018 μM. The Increase in shearing stress with shearing speed is 5–8% higher in the presence of DPPA may be due to the rigidity of the collagen chains. DPPA facilitates self assembly processes, thinner fibrils are seen in polarizing light microscopy and seem to favor the molecular and phase structure of collagen. Thermal stability of collagen in the presence of DPPA ensured the integrity and stabilization of reconstituted collagen fibrillar matrices. Collagen fibrils have higher denaturation enthalpy 15 J/gm at 0.5 μM (DPPA) when compared to 10.5 J/gm for native collagen fibrils which is an indication of more stable fibrils. As a result, the reconstituted collagen fibrils in the presence of DPPA brought about the stabilization of the secondary structure of collagen molecules at lower concentrations of DPPA.