ASSESSING THE IMPACT OF BACKBONE LENGTH AND CAPPING AGENT ON THE CONFORMATIONAL PREFERENCES OF A MODEL PEPTIDE: CONFORMATION SPECIFIC IR AND UV SPECTROSCOPY OF 2-AMINOISOBUTYRIC ACID

Gord, Joseph R.

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Description

Title

ASSESSING THE IMPACT OF BACKBONE LENGTH AND CAPPING AGENT ON THE CONFORMATIONAL PREFERENCES OF A MODEL PEPTIDE: CONFORMATION SPECIFIC IR AND UV SPECTROSCOPY OF 2-AMINOISOBUTYRIC ACID

Author(s)

Gord, Joseph R.

Contributor(s)

• Zwier, Timothy S.
• Kubasik, Matthew A.
• Hewett, Daniel M.

Issue Date

22-Jun-15

Keyword(s)

Structure determination

Abstract

2-Aminoisobutyric acid (Aib) is an achiral, ${alpha}$-amino acid having two equivalent methyl groups attached to C$_{alpha}$. Extended Aib oligomers are known to have a strong preference for the adoption of a 3$_{10}$-helical structure in the condensed phase.footnote{Toniolo, C.; Bonora, G. M.; Barone, V.; Bavoso, A.; Benedetti, E.; Di Blasio, B.; Grimaldi, P.; Lelj, F.; Pavone, V.; Pedone, C., Conformation of Pleionomers of $alpha$-Aminoisobutyric Acid. textit{Macromolecules} textbf{1985}, textit{18}, 895-902.} Here, we have taken a simplifying step and focused on the intrinsic folding propensities of Aib by looking at a series of capped Aib oligomers in the gas phase, free from the influence of solvent molecules and cooled in a supersonic expansion. Resonant two-photon ionization and IR-UV holeburning have been used to record single-conformation UV spectra using the Z-cap as the UV chromophore. Resonant ion-dip infrared (RIDIR) spectroscopy provides single-conformation IR spectra in the OH stretch and NH stretch regions. Data have been collected on a set of Z-(Aib)$_{n}$-X oligomers with n = 1, 2, 4, 6 and X = -OH and -OMethyl. The impacts of these capping groups and differences in backbone length have been found to dramatically influence the conformational space accessed by the molecules studied here. Oligomers of n=4 have sufficient backbone length for a full turn of the 3$_{10}$-helix to be formed. Early interpretation of the data collected shows clear spectroscopic markers signaling the onset of 3$_{10}$-helix formation as well as evidence of structures incorporating C7 and C14 hydrogen bonded rings.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

English

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