title: Toward the understanding of the environmental effects on core ionizations.
abstract: Experimental X-ray absorption spectra are extensively used to determine electronic structure of small molecules but remain difficult to exploit for proteins due to the large number of peaks within their spectra. For such complex systems, theoretical tools like quantum mechanics/molecular mechanics methodology can greatly ease the assignment of the spectra. This study presents a systematic methodology to evaluate core-ionization energies (E(ion)) in proteins with the help of the asymptotic projection approach (Glushkov and Tsaune, Z. Vichislit. Matem. Mat. Fiz. 1985, 25, 298; Glushkov, Chem. Phys. Lett. 1997, 273, 122; Glushkov, Chem. Phys. Lett. 1998, 287, 189; Glushkov, J. Math. Chem. 2002, 31, 91; Glushkov, Opt. Spectrosc. 2002, 93, 15). An in-depth inspection of E(ion) of systems of increasing complexity is considered, going from amino acids to polyglycine and to glycine in human serum albumin (HSA). Computational analysis can help to better understand experimental data and to discriminate environmental effects by tracing them back to individual and collective electrostatic contributions. In the present work, it was found that E(ion) of alpha carbon of glycine residues in HSA ranges from 285 to 295 eV depending on their surroundings.
authors.affiliation: CEISAM, UMR CNRS 6230, BP 92208, Université de Nantes, 2, Rue de la Houssinière, 44322 Nantes, Cedex 3, France.
authors.forename: Adèle D
authors.initials: AD
authors.lastname: Laurent
authors.forename: Vitaly N
authors.initials: VN
authors.lastname: Glushkov
authors.forename: Thibaut
authors.initials: T
authors.lastname: Very
authors.forename: Xavier
authors.initials: X
authors.lastname: Assfeld
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D003198:Computer Simulation; D007477:Ions; D008956:Models, Chemical; D008958:Models, Molecular; D009930:Organic Chemicals; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy / Q000379:methods*
chemical_list: D000596:Amino Acids; D007477:Ions; D009930:Organic Chemicals; D011506:Proteins
keywords: QM/MM; amino acids; asymptotic projection; core ionizations; human serum albumin