Conformation-specific infrared and ultraviolet spectroscopy of cold [YAPAA+H]+ and [YGPAA+H]+ ions: A stereochemical 'twist' on the β-hairpin turn

DeBlase, Andrew F.

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https://hdl.handle.net/2142/97149 Copy

Description

Title

Conformation-specific infrared and ultraviolet spectroscopy of cold [YAPAA+H]+ and [YGPAA+H]+ ions: A stereochemical 'twist' on the β-hairpin turn

Author(s)

DeBlase, Andrew F.

Contributor(s)

• Zwier, Timothy S.
• McLuckey, Scott A.
• Burke, Nicole L.
• Lawler, John T.
• Harrilal, Christopher P.

Issue Date

2017-06-23

Keyword(s)

Ions

Abstract

Incorporation of the unnatural D-proline ($^{D}$P) stereoisomer into a polypeptide sequence is a typical strategy to encourage formation of $beta$-hairpin loops because natural sequences are often unstructured in solution. Using conformation-specific IR and UV spectroscopy of cold (10 K) gas-phase ions, we probe the inherent conformational preferences of the $^{D}$P and $^{L}$P diastereomers in the protonated peptide [YAPAA+H]$^{+}$, where only intramolecular interactions are possible. Consistent with the solution phase studies, one of the conformers of [YADPAA+H]$^{+}$ is folded into a charge-stabilized $beta$-hairpin turn. However, a second predominant conformer family containing two sequential $gamma$-turns is also identified, with similar energetic stability. A single conformational isomer of the $^{L}$P diastereomer, [YALPAA+H]$^{+}$, is found and assigned to a structure that is not the anticipated “mirror image” $beta$-turn. Instead, the $^{L}$P stereo center promotes a cis alanine-proline amide bond. The assigned structures contain clues that the preference of the $^{D}$P diastereomer to support a trans-amide bond and the proclivity of $^{L}$P for a cis-amide bond is sterically driven and can be reversed by substituting glycine for alanine in position 2, forming [YGLPAA+H]$^{+}$. These results provide a basis for understanding the residue-specific and stereo-specific alterations in the potential energy surface that underlie these changing preferences, providing insights to the origin of $beta$-hairpin formation.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Permalink

http://hdl.handle.net/2142/97149

DOI

https://doi.org/10.15278/isms.2017.FE04

Copyright and License Information

Copyright 2017 Andrew F. DeBlase

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