Interactions of aggregating peptides probed by IR-UV action spectroscopy

Abstract

The interplay between intramolecular and formed inter-sheet hydrogen bonds and the effect of dispersion interactions on the formation of peptide dimers is studied using IR-UV action spectroscopy.

Formation of Neutral Peptide Aggregates as Studied by Mass‐Selective IR Action Spectroscopy

“…In contrast, the studied neutral dimer did form a β‐sheet structure in the gas phase. Recently, we studied the competition between intra‐ and intermolecular interactions upon dimer formation of alanine‐containing peptides …”

“…The ester C=O groups are not involved in any hydrogen bonding. The individual peptides present in the parallel β‐sheet dimer retain their monomeric structures: the linear and the γ‐turn conformer are both present in the dimer, in which their weak intramolecular hydrogen bonds (C5 hydrogen bond and NH–π bond) are replaced by stronger intermolecular hydrogen bonds . The calculated IR spectrum of an antiparallel dimer is also compared with the recorded IR spectrum in Figure a.…”

Formation of Neutral Peptide Aggregates Studied by Mass Selective IR Action Spectroscopy

“…Theindividual peptides present in the parallel b-sheet dimer retain their monomeric structures:t he linear and the g-turn conformer are both present in the dimer,inwhich their weak intramolecular hydrogen bonds (C5 hydrogen bond and NHp bond) are replaced by stronger intermolecular hydrogen bonds. [14,17] Thec alculated IR spectrum of an antiparallel dimer is also compared with the recorded IR spectrum in Figure 4a.This structure,like the parallel dimer,has no ester C=Og roups involved in hydrogen bonding;h owever, was discarded as ar esult of am ismatch in the amide II region together with its high energy.…”

“…Thet hird peptide can aggregate on both sides of the dimer:a tt he C7 g-turn intramolecularly or weaker C5 intramolecularly hydrogen bonded side.O nt he basis of energetics and spatial orientation, it is expected that the weaker C5 hydrogen bond is broken to favor the formation of strong intermolecular b-sheet interactions. [14] Tw o b-sheetcontaining structures remain possible:a na ll-parallel structure and astructure in which the third monomer is attached in an antiparallel fashion to the dimer.T he added monomer peptide adopts either the observed linear conformer (for the all-parallel structure; Figure 4b,left) or the g-turn conformer for the antiparallel structure (Figure 4b,r ight). Thea ntiparallel structure shows ab etter overlap in the region around 1200 cm À1 ;h owever, the all-parallel structure has considerably (17 kJ mol À1 )l ower energy and reproduces the double peak in the amide II region better.O verall, the structure of .…”

“…[13] They showed that the charge on the lysine prevents the formation of extended peptide backbone segments as observed in amyloid fibrils.I nc ontrast, the studied neutral dimer did form a bsheet structure in the gas phase.R ecently,w es tudied the competition between intra-and intermolecular interactions upon dimer formation of alanine-containing peptides. [14] Here,for the first time,wedemonstrate the formation of stable higher-order clusters of neutral peptides in the gas phase using laser desorption (the experiment is described in the Experimental Section and Supporting Information). The peptide used in our experiments is the capped dipeptide Ac-Ala-Ala-OBn (BioMatik, > 95 %purity,molecular weight of 292.31 amu).…”