title: Absorption in the Q-band region by isolated ferric heme+ and heme+(histidine) in vacuo.
abstract: Absorption by heme proteins is determined by the heme microenvironment that is often vacuumlike (hydrophobic pocket). Here we provide absorption spectra in the Q-band region of isolated ferric heme(+) and heme(+)(histidine) ions in vacuo to be used as references in protein biospectroscopy. Ions were photoexcited in an electrostatic storage ring and their decay monitored in time. Both ions display a triple band structure with maxima at 500, 518, and 530 nm. Previous attempts to study four-coordinate Fe(III)-heme(+) were hampered by the strong affinity of Fe(3+) for water and anions. Absorption at higher wavelengths is also measured, which is ascribed to charge-transfer transitions from the porphyrin to the iron. Finally, our data serve to benchmark theoretical calculations.
authors.affiliation: Department of Physics and Astronomy, Aarhus University, Ny Munkegade, DK-8000 Aarhus C, Denmark. jeanwyer@phys.au.dk
authors.forename: Jean Ann
authors.initials: JA
authors.lastname: Wyer
authors.forename: Steen
authors.initials: S
authors.lastname: Brøndsted Nielsen
mesh_terms: D000465:Algorithms; D000838:Anions / Q000737:chemistry; D002412:Cations / Q000737:chemistry; D005290:Ferric Compounds / Q000737:chemistry*; D005998:Glycine / Q000737:chemistry; D006418:Heme / Q000737:chemistry*; D006420:Hemeproteins / Q000737:chemistry*; D006639:Histidine / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D000432:Methanol / Q000737:chemistry; D008752:Methylene Chloride / Q000737:chemistry; D008956:Models, Chemical; D012997:Solvents / Q000737:chemistry; D013057:Spectrum Analysis; D055672:Static Electricity; D014618:Vacuum; D014867:Water / Q000737:chemistry
chemical_list: D000838:Anions; D002412:Cations; D005290:Ferric Compounds; D006420:Hemeproteins; D012997:Solvents; D014867:Water; D006418:Heme; D006639:Histidine; D008752:Methylene Chloride; D005998:Glycine; D000432:Methanol