3rd Workshop on the Simultaneous Combination of Spectroscopies with X-ray Absorption, Scattering and Diffraction Techniques

Selective X-ray induced NO-photodissociation in hemoglobin crystals: evidences from a crystallography-assisted Raman microscopy study

5 Jul 2012, 10:30

1h 30m

Main Hall HG E

Poster contribution Biological / Pharmaceutical Research Poster Session

Speaker

Mr Andrea Pica (Dept Chemical Sciences, University of Naples "Federico II")

Description

Despite the high physiological relevance, hemoglobin crystal structures with NO bound to heme are less than 1% of the total ligated hemoglobins (Hbs) deposited in the Protein Data Bank. One of the major difficulties in obtaining nitrosyl-ligated Hbs is probably related to oxidative denitrosylation, being nitrosylated species very reactive toward O2. Raman-assisted crystallography can be a valuable tool to follow derivative crystal preparation[1,2], metal coordination states[3,4], and X-ray photodamage[5,6]. Here, using X-ray crystallography-assisted Raman microscopy, we show that upon X-ray exposure (SLS, X10SA beamline), crystals of nitrosylated hemoglobin from Trematomus bernacchii[7] undergo a selective photodissociation of the Fe-NO bond at the β chains generating penta-coordinate species. These data provide a physical explanation of the small amount of nitrosylated Hbs structures available in the literature, suggesting that X-ray induced photodissociation is a frequent and underestimated phenomenon[8,9]. [1] Carpentier et al, J App Cryst 2007, 40, 1113-1122. [2] Vergara et al., Acta Cryst D, 2008, 64, 167-71. [3] Katona et al, Science, 2007, 316, 449-53. [4] Vergara et al, JBC, 2010, 285, 32568-75. [5] McGeehan et al, J Synch rad, 2007, 14, 99-108. [6] Carpentier et al, Structure, 2010, 18, 1410-9. [7] Mazzarella et al., Proteins 2006, 65, 490-8. [8] Garman et al, Acta Cryst D, 2010, 66, 339-51. [9] Arcovito et al, Inorg chem, 2011, 50, 9423-9.