These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Amide I bands of terminally blocked alanine in solutions investigated by infrared spectroscopy and density functional theory calculation: hydrogen-bonding interactions and solvent effects.
    Author: Lee ME, Lee SY, Joo SW, Cho KH.
    Journal: J Phys Chem B; 2009 May 14; 113(19):6894-7. PubMed ID: 19374358.
    Abstract:
    Structural aspects of terminally blocked alanine trans-N-acetyl-L-alanyl-trans-N'-methylamide (Ac-Ala-NHMe) in several different solvents were compared by attenuated total reflection infrared (ATR-IR) spectroscopy and density functional theory (DFT) calculations. The amide I bands between 1600 and 1700 cm(-1) appeared to change depending on media, indicating dissimilar hydrogen-bonding interactions among the peptides and solvent molecules. The minimum energy geometry in the isolated gas phase and aqueous environments were calculated at the B3LYP/6-311++G** theoretical level. In the solid state, Ac-Ala-NHMe is assumed to have an extended beta-stranded structure (C5), whereas it is assumed to have a cyclic structure (C7eq or alphaL) in a nonpolar tetrahydrofuran (THF) solvent. The optimized backbone dihedral angles (Phi, Psi) of Ac-Ala-NHMe plus four explicit water molecules were estimated to be -94 degrees and +133 degrees, respectively, indicating the polyproline II structure (PII). The energy differences between the most stable conformers were predicted to be larger for Ac-Ala-NHMe, which implies that more conformational ensemble structures should coexist for the gas phase than for the aqueous medium with explicit water molecules.
    [Abstract] [Full Text] [Related] [New Search]