文摘
The ultrastructure of isolated fibrils of Chondrosia reniformis sponge collagen was investigated by collectingcharacteristic data, such as fibril thickness, width, D-band periodicity, and height modulation, using atomic forcemicroscopy (AFM) and transmission electron microscopy (TEM). Therefore an adapted pre-processing of theinsoluble collagen into homogeneous suspensions using neutral buffer solutions was essential, and severalpurification steps have been developed. Fourier transform infrared reflection-absorption spectroscopy (FT-IRAS)of the purified sponge collagen showed remarkable analogy of peak positions and intensities with the spectra offibrillar calf skin type I collagen, despite the diverse phylogenetic and evolutionary origin. The sponge collagen'smorphology is compared with that of other fibrillar collagens, and the typical banding of the separated singlefibrils is discussed by comparison of topographical data obtained using AFM and corresponding TEM investigationsusing common staining methods. As the TEM images of the negatively stained fibrils showed alternating darkand light bands, AFM revealed a characteristic periodicity of protrusions (overlap zones) followed by two equalinterband regions (gap zones). AFM and TEM results were correlated and multiperiodicity in Chondrosia collagen'sbanding is demonstrated. The periodic dark bands observed in TEM images correspond directly to the periodicprotrusions seen by AFM. As a result, we provide an improved, updated model of the collagen's structure andorganization.