High pressure Raman study of type‐I collagen

Abstract

The high pressure response of type-I collagen from bovine Achilles tendon is investigated with micro-Raman spectroscopy. Fluorinert™ and methanol-ethanol mixtures were used as pressure transmitting media (PTM) in a diamond anvil cell. The Raman spectrum of collagen is dominated by three bands centred at approximately 1450, 1660 and 2930 cm , attributed to C-H deformation, C=O stretching of the peptide bond (amide-I band) and C-H stretching modes respectively. Upon pressure increase, using Fluorinert™ as PTM, a shift towards higher frequencies of the C-H stretching and deformation peaks is observed. Contrary, the amide-I band peaks are shifted to lower frequencies with moderate pressure slopes. On the other hand, when using the alcohol mixture as PTM, the amide-I band exhibits more pronounced C=O bond softening, deduced from the shift to lower frequencies, suggesting a strengthening of the hydrogen bonds between glycine and proline residues of different collagen chains due to the presence of the polar alcohol molecules. Furthermore, some of the peaks exhibit abrupt changes in their pressure slopes at approximately 2 GPa, implying a variation in the compressibility of the collagen fibres. This could be attributed to a pitch change from 10/3 to 7/2, sliding of the tropocollagen molecules, twisting variation at the molecular level and/or elimination of the D-gaps induced by kink compression. All spectral changes are reversible upon pressure release, which indicates that denaturation has not taken place. Finally, a minor lipid phase contamination was detected in some sample spots. Its pressure response is also monitored.

Biomolecules under Pressure: Phase Diagrams, Volume Changes, and High Pressure Spectroscopic Techniques

“…The pressure shift of the spectral lines in vibrational spectroscopic techniques depends on the contribution of the normal vibration to the volume of the molecule [ 57 ]. Typically, dν/dp values are positive, due to the bond strengthening upon pressurization.…”

“…Although the weakness of the Raman scattering limits its applications in the structural analysis of biomolecules, there are some recent examples where it was successfully applied in the high pressure field. It was used to study pressure’s effect on collagen [ 57 ], and another group used Raman spectroscopy to detect the germination of pressure-treated spores by following the 1017 cm − 1 band of the Ca-dipicolinic acid [ 69 ].…”

Raman Spectroscopy in Skeletal Tissue Disorders and Tissue Engineering: Present and Prospective

“…Collagen type I structure was also studied under hydrostatic pressure. 62 The study of tendon enthesis by RS helped getting more insight on its development and structure. 63 Traditionally, it was believed that the tendon enthesis was divided into distinct regions, whereas mechanical studies suggested a gradual transition of tissue structure and functional properties.…”

Effects of low concentration of proanthocyanidins and oxidation conditions on myofibrillar protein in chicken breast muscle

“…Generally, the Raman spectral bands of amide I (1600-1700 cm -1 ) and amide III (1200-1300 cm -1 ) were used for measuring the secondary structure 10,11 . The MPs gel of high percent of α-helix, β-sheet, random coil and β-turn could be severally appointed at 1650-1658 cm -1 , 1665-1680 cm -1 , 1660-1665 cm -1 and 1680-1690 cm -1 12, 13 .…”