BOVINE ELASTIN AND KAPPA-ELASTIN SECONDARY STRUCTURE DETERMINATION BY OPTICAL SPECTROSCOPIES

Elastin is the macromolecular polymer of tropoelastin molecules responsible for the elastic properties of tissues. The understanding of its specific elasticity is uncertain because its structure is still unknown. Here, we report the first experimental quantitative determination. of bovine elastin secondary structures as well as those of its corresponding soluble K-elastin. Using circular dichroism and Fourier transform infrared and near infrared Fourier transform Raman spectroscopic data, we estimated the secondary structure contents of elastin to be similar to 10% alpha-helices, similar to 45% beta-sheets, and similar to 45% undefined conformations. These values were very close to those we had previously determined for the free monomeric tropoelastin molecule, suggesting thus that elastin would be constituted of a closely packed assembly of globular beta structural class tropoelastin molecules crosslinked to form the elastic network (liquid drop model of elastin architecture). The presence of a strong hydration shell is demonstrated for elastin, and its possible contribution to elasticity is discussed.