title: Polarized X-ray absorption near-edge structure spectroscopy of neuroglobin and myoglobin single crystals.
abstract: Polarized Fe K-edge X-ray absorption near-edge structure (XANES) spectra of murine carbonmonoxy-neuroglobin (NgbCO) single crystals have been collected and compared with a number of derivatives of sperm whale myoglobin (Mb), that is, the nitrosyl (MbNO) and deoxy (Mb) derivatives, the previously reported cyanomet (MbCN) and carbonmonoxy (MbCO) derivatives, and the cryogenic photoproduct of MbCO (Mb·CO). The single crystals under study exhibit a strong XANES angular dichroism which allows the heme geometry of each sample to be analyzed with extremely high accuracy via the full multiple scattering (MS) approach. The results of two alternative methods to undergo the MS analysis have been compared with high resolution X-ray diffraction (XRD) data and with X-ray absorption spectroscopy (XAS) data in solution. As a result of the present analysis, the Fe-heme structure in solution and in the cryo-trapped NgbCO single crystal (which cracks at room temperature) are the same. Accordingly, the residual energy involved in the protein relaxation responsible of crystal cracking at room temperature after CO binding does not reside in the heme pocket. A combined approach (polarized XANES and XRD) is suggested to be applied on the same single crystals of metalloproteins at opportunely equipped synchrotron beamlines.
authors.affiliation: Istituto di Biochimica e Biochimica Clinica, Università Cattolica del Sacro Cuore, L. go F. Vito 1, 00168 Rome, Italy. alessandro.arcovito@rm.unicatt.it
authors.forename: Alessandro
authors.initials: A
authors.lastname: Arcovito
authors.forename: Chiara
authors.initials: C
authors.lastname: Ardiccioni
authors.forename: Michele
authors.initials: M
authors.lastname: Cianci
authors.forename: Paola
authors.initials: P
authors.lastname: D'Angelo
authors.forename: Beatrice
authors.initials: B
authors.lastname: Vallone
authors.forename: Stefano
authors.initials: S
authors.lastname: Della Longa
mesh_terms: D000818:Animals; D002248:Carbon Monoxide / Q000737:chemistry; D018360:Crystallography, X-Ray; D005914:Globins / Q000737:chemistry*; D008786:Metmyoglobin / Q000737:chemistry; D051379:Mice; D008958:Models, Molecular; D009211:Myoglobin / Q000737:chemistry*; D009419:Nerve Tissue Proteins / Q000737:chemistry*; D000078787:Neuroglobin; D050661:Sperm Whale / Q000378:metabolism*; D056928:X-Ray Absorption Spectroscopy / Q000379:methods*
chemical_list: D009211:Myoglobin; D009419:Nerve Tissue Proteins; D000078787:Neuroglobin; C007177:cyanometmyoglobin; C031560:myoglobin nitroxide; D008786:Metmyoglobin; D002248:Carbon Monoxide; D005914:Globins