Schwob Lucas, Lalande Mathieu, Rangama Jimmy, Egorov Dmitrii, Hoekstra Ronnie, Pandey Rahul, Eden Samuel, Schlathölter Thomas, Vizcaino Violaine, Poully Jean-Christophe
CIMAP, UMR 6252 (CEA/CNRS/ENSICAEN/Université de Caen Normandie), Caen, France.
Phys Chem Chem Phys. 2017 Jul 19;19(28):18321-18329. doi: 10.1039/c7cp02527k.
Cartilage and tendons owe their special mechanical properties to the fibrous collagen structure. These strong fibrils are aggregates of a sub-unit consisting of three collagen proteins wound around each other in a triple helix. Even though collagen is the most abundant protein in the human body, the response of this protein complex to ionizing radiation has never been studied. In this work, we probe the direct effects of VUV and soft X-ray photons on isolated models of the collagen triple helix, by coupling a tandem mass spectrometer to a synchrotron beamline. Single-photon absorption is found to induce electronic excitation, ionization and conversion into internal energy leading to inter- and intra-molecular fragmentation, mainly due to Gly-Pro peptide bond cleavages. Our results indicate that increasing the photon energy from 14 to 22 eV reduces fragmentation. We explain this surprising behavior by a smooth transition from excitation to ionization occurring with increasing photon energy. Moreover, our data support the assumption of a stabilization of the triple helix models by proline hydroxylation via intra-complex stereoelectronic effects, instead of the influence of solvent.
软骨和肌腱的特殊力学性能归因于纤维状的胶原蛋白结构。这些强纤维是由三个胶原蛋白蛋白以三螺旋形式相互缠绕组成的亚基聚集体。尽管胶原蛋白是人体中最丰富的蛋白质，但这种蛋白质复合物对电离辐射的反应从未被研究过。在这项工作中，我们通过将串联质谱仪与同步加速器光束线耦合，探究了真空紫外（VUV）和软X射线光子对分离的胶原蛋白三螺旋模型的直接影响。发现单光子吸收会诱导电子激发、电离并转化为内能从而导致分子间和分子内碎片化，这主要是由于甘氨酸-脯氨酸肽键的断裂。我们的结果表明，将光子能量从14 eV增加到22 eV会减少碎片化。我们通过随着光子能量增加从激发到电离的平稳转变来解释这种令人惊讶的行为。此外，我们的数据支持通过复合物内立体电子效应而非溶剂的影响，脯氨酸羟基化使三螺旋模型稳定的假设。
