eprintid: 14441 rev_number: 29 userid: 1291 dir: disk0/00/01/44/41 datestamp: 2012-09-25 14:21:58 lastmod: 2021-06-12 23:55:16 status_changed: 2012-09-25 14:21:58 type: article metadata_visibility: show item_issues_count: 0 eprint_status: archive creators_name: Bykov, SV creators_name: Myshakina, NS creators_name: Asher, SA creators_email: creators_email: creators_email: asher@pitt.edu creators_id: creators_id: creators_id: ASHER title: Dependence of glycine CH2 stretching frequencies on conformation, ionization state, and hydrogen bonding ispublished: pub divisions: sch_as_chemistry full_text_status: public abstract: We experimentally and theoretically examined the conformation, pH, and temperature dependence of the CH2 stretching frequencies of glycine (gly) in solution and in the crystalline state. To separate the effects of the amine and carboxyl groups on the CH2 stretching frequencies we examined the Raman spectra of 2,2,2-d3-ethylamine (CD 3-CH2-NH2) and 3,3,3-d3-propionic acid (CD3-CH2-COOH) in D2O. The symmetric (vsCH2) and asymmetric (vasCH2) stretching frequencies show a significant dependence on gly conformation. We quantified the relation between the frequency splitting (Δ = v asCH2 -vsCH2) and the ξ angle which determines the gly conformational geometry. This relation allows us to determine the conformation of gly directly from the Raman spectral frequencies. We observe a large dependence of the vsCH2 and v asCH2 frequencies on the ionization state of the amine group, which we demonstrate theoretically results from a negative hyperconjugation between the nitrogen lone pair and the C-H antibonding orbitais. The magnitude of this effect is maximized for C-H bonds trans to the nitrogen lone pair. In contrast, a small dependence of the CH2 stretching frequencies on the carboxyl group ionization state arises from derealization of electron density from carboxyl oxygen to C-H bonding orbitals. According to our experimental observations and theoretical calculations the temperature dependence of the vsCH2 and v asCH2 of gly is due to the change in the hydrogen-bonding strength of the amine/carboxyl groups to water. © 2008 American Chemical Society. date: 2008-05-08 date_type: published publication: Journal of Physical Chemistry B volume: 112 number: 18 pagerange: 5803 - 5812 refereed: TRUE issn: 1520-6106 id_number: 10.1021/jp710136c other_id: NLM NIHMS239071 other_id: NLM PMC2952399 pmcid: PMC2952399 pmid: 18447350 mesh_headings: Amines--chemistry mesh_headings: Carbon--chemistry mesh_headings: Glycine--chemistry mesh_headings: Hydrogen--chemistry mesh_headings: Hydrogen Bonding mesh_headings: Ions--chemistry mesh_headings: Models, Molecular mesh_headings: Molecular Conformation mesh_headings: Propionic Acids--chemistry mesh_headings: Solutions mesh_headings: Spectrum Analysis, Raman mesh_headings: Temperature mesh_headings: Vibration chemical_names: Amines chemical_names: Ions chemical_names: Propionic Acids chemical_names: Solutions chemical_names: Hydrogen chemical_names: Glycine chemical_names: Carbon chemical_names: propionic acid citation: Bykov, SV and Myshakina, NS and Asher, SA (2008) Dependence of glycine CH2 stretching frequencies on conformation, ionization state, and hydrogen bonding. Journal of Physical Chemistry B, 112 (18). 5803 - 5812. ISSN 1520-6106 document_url: http://d-scholarship-dev.library.pitt.edu/14441/1/licence.txt