European XFEL Science Seminar

Correlated spin and structural dynamics in the recombination of nitric oxide (NO) to deoxy-Myoglobin in physiological media

by Camila Bacellar (École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland)

E1.173 (Campus Schenefeld main building (XHQ))


Campus Schenefeld main building (XHQ)

Myoglobin is a small protein consisting of a single polypeptide chain of 153 amino acid residues and a heme group as its active center. It plays a central role in many biological functions based on detection, transport, release and/or binding of molecular ligands such as O2, CO, NO, CN, etc. The unligated high spin form (deoxyMb) binds the ligand at the Fe center of the porphyrin, leading to a change to the planar low spin ligated form. Since, the heme group is equivalent in all Myoglobin forms, variations in the functions of ligated Mbs arise from differences in spin, electronic configuration and geometric structure. Nitrosyl-Myoglobin (MbNO), in particular, is not entirely understood despite its biological relevance as it controls various physiological responses. The ultrafast photodissociation of low spin, planar MbNO leads to the high spin, domed unligated Mb. However, part of the population undergoes recombination in multiple timescales (10s to 100s ps) through an intermediate state that is presumed to be a high spin domed ligated form of MbNO. In order to elucidate the dissociation-recombination dynamics of MbNO, we carried out combined ultrafast X-ray emission spectroscopy (XES), X-ray diffuse scattering (XDS) at the newly designed FXE beamline. Preliminary data aims to correlate the local spin (from XES) to conformational changes (from XDS) in the first demonstration of combined ultrafast XES, XDS on a protein in physiological media