13C═18O/15N Isotope Dependence of the Amide-I/II 2D IR Cross Peaks for the Fully Extended Peptides

Maekawa, Hiroaki; Ballano, Gema; Formaggio, Fernando; Toniolo, Claudio; Ge, Nien‐Hui

doi:10.1021/jp5091679

Cited by 18 publications

(19 citation statements)

References 57 publications

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“…The molecular structure of GSH with the corresponding isotope-substituted atoms, denoted by asterisks, is shown in the inset of Figure 5. We noted that despite the presence of several additional heavy isotopes, the shift in the cysteine amide-I transition frequency is mostly affected by the carbonyl 13 C substitution, whereas modifications of the remaining atoms do not perturb the amide-I modes significantly, 78 as confirmed by the normal mode analysis of the geometry-optimized 79 peptide structures that we conducted.…”

Section: Agsupporting

confidence: 60%

“…The 2DIR spectrum in Figure a shows that in the case of 13 C-labeled GSH molecules free in solution, the amide-I transitions appear at excitation frequencies of ω ex = 1643 cm –1 and ω ex = 1616 cm –1 , indicating that the assignment proposed previously both by Qian and Krimm and in ref should be reversed: the 1643 cm –1 transition should be assigned to the ω E transition of the amide-I mode of the unmodified γ-glutamyl (E), which is now sufficiently separated from amide-I in the cysteine. The corresponding red-shift by 2 cm –1 from the proposed frequency for its original local mode at ω loc, E = 1645 cm –1 is probably because of the 15 N substitution on the cysteine precursor that was used in the peptide synthesis . The second amide-I transition is assigned to the cysteine (C), such that the frequency shift upon the 13 C labeling of the carbonyl is 45 cm –1 , from the ω C = 1661 cm –1 in the non-labeled GSH to the ω C* = 1616 cm –1 in the labeled case.…”

Section: Resultsmentioning

confidence: 98%

“…The corresponding red-shift by 2 cm −1 from the proposed frequency for its original local mode at ω loc, E = 1645 cm −1 is probably because of the 15 N substitution on the cysteine precursor that was used in the peptide synthesis. 78 The second amide-I transition is assigned to the cysteine (C), such that the frequency shift upon the 13 C labeling of the carbonyl is 45 cm −1 , from the ω C = 1661 cm −1 in the nonlabeled GSH to the ω C* = 1616 cm −1 in the labeled case.…”

Section: Agmentioning

confidence: 99%

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Glutathione Self-Assembles into a Shell of Hydrogen-Bonded Intermolecular Aggregates on “Naked” Silver Nanoparticles

2021

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A detailed understanding of the molecular structure in nanoparticle ligand capping layers is crucial for their efficient incorporation into modern scientific and technological applications. Peptide ligands render the nanoparticles as biocompatible materials. Glutathione, a γ-ECG tripeptide, self-assembles into aggregates on the surface of ligand-free silver nanoparticles through intermolecular hydrogen bonding and forms a few nanometer-thick shells. Two-dimensional nonlinear infrared (2DIR) spectroscopy suggests that aggregates adopt a conformation resembling the β-sheet secondary structure. The shell thickness was evaluated with localized surface plasmon resonance spectroscopy and X-ray photoelectron spectroscopy. The amount of glutathione on the surface was obtained with spectrophotometry of a thiol-reactive probe. Our results suggest that the shell consists of ∼15 stacked molecular layers. These values correspond to the inter-sheet distances, which are significantly shorter than those in amyloid fibrils with relatively bulky side chains, but are comparable to glycine-rich silk fibrils, where the side chains are compact. The tight packing of the glutathione layers can be facilitated by hydrogen-bonded carboxylic acid dimers of glycine and the intermolecular salt bridges between the zwitterionic γ-glutamyl groups. The structure of the glutathione aggregates was studied by 2DIR spectroscopy of the amide-I vibrational modes using 13C isotope labeling of the cysteine carbonyl. Isotope dilution experiments revealed the coupling of modes forming vibrational excitons along the cysteine chain. The coupling along the γ-glutamyl exciton chain was estimated from these values. The obtained coupling strengths are slightly lower than those of native β-sheets, yet they appear large enough to point onto an ordered conformation of the peptides within the aggregate. Analysis of the excitons’ anharmonicities and the strength of the transition dipole moments generally is in agreement with these observations.

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Section: Agsupporting

confidence: 60%

Section: Resultsmentioning

confidence: 98%

Section: Agmentioning

confidence: 99%

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Glutathione Self-Assembles into a Shell of Hydrogen-Bonded Intermolecular Aggregates on “Naked” Silver Nanoparticles

2021

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“…In general, α(or 3 10 )‐helical peptides display the amide I band at about 1665 cm −1 and a less intense amide II band at about 1530 cm −1 [18] . On the other hand, in peptides adopting the fully‐extended conformation (i) the intensity of the amide II band (∼1500 cm −1 ) is higher than that of the amide I (∼1660 cm −1 ) and (ii) the amide II band falls below 1500 cm −1 [9g–j] . These features are clearly observed in the IR spectra of peptides 1 – 4 .…”

Section: Resultsmentioning

confidence: 95%

Flat, C^α,β‐Didehydroalanine Foldamers with Ferrocene Pendants: Assessing the Role of α‐Peptide Dipolar Moments

et al. 2021

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The foldamer field is continuously expanding as it allows to produce molecules endowed with 3D-structures and functions never observed in nature. We synthesized flat foldamers based on the natural, but non-coded, C α,β -didehydroalanine α-amino acid, and covalently linked to them two ferrocene (Fc) moieties, as redox probes. These conjugates retain the flat and extended conformation of the 2.0 5 -helix, both in solution and in the crystal state (X-ray diffraction). Cyclic voltammetry measure-ments agree with the adoption of the 2.0 5 -helix, characterized by a negligible dipole moment. Thus, elongated α-peptide stretches of this type are insulators rather than charge conductors, the latter being constituted by peptide α-helices. Also, our homo-tetrapeptide has a N-to-C length of about 18.2 Å, almost double than that (9.7 Å) of an α-helical αtetrapeptide.

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“…Diagonal peak suppression was widely implemented in 2D spectroscopy ( 18 , 22 , 23 , 28 – 38 ) until pump-probe beam geometries began replacing the four-wave mixing geometry. The most common pump-probe implementation of 2D spectroscopy is using a pulse shaper to create the two pump pulses ( 39 , 40 ).…”

mentioning

confidence: 99%

A polarization scheme that resolves cross-peaks with transient absorption and eliminates diagonal peaks in 2D spectroscopy

Farrell

Yang

Zanni

2022

Proc. Natl. Acad. Sci. U.S.A.

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Significance Observation of cross-peaks is one of the hallmark advantages of multidimensional spectroscopy. Often times, cross-peaks overlap with strong diagonal peak features, obfuscating information that is useful for determining molecular structure. Here, we present a polarization scheme that eliminates diagonal peaks, revealing the weaker cross-peak features. This polarization scheme can be applied to one-dimensional transient absorption spectroscopy. As a result, transient absorption spectroscopy can now access information that previously required two-dimensional spectroscopies.

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¹³C═¹⁸O/¹⁵N Isotope Dependence of the Amide-I/II 2D IR Cross Peaks for the Fully Extended Peptides

Cited by 18 publications

References 57 publications

Glutathione Self-Assembles into a Shell of Hydrogen-Bonded Intermolecular Aggregates on “Naked” Silver Nanoparticles

Glutathione Self-Assembles into a Shell of Hydrogen-Bonded Intermolecular Aggregates on “Naked” Silver Nanoparticles

Flat, C^α,β‐Didehydroalanine Foldamers with Ferrocene Pendants: Assessing the Role of α‐Peptide Dipolar Moments

A polarization scheme that resolves cross-peaks with transient absorption and eliminates diagonal peaks in 2D spectroscopy

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13C═18O/15N Isotope Dependence of the Amide-I/II 2D IR Cross Peaks for the Fully Extended Peptides

Cited by 18 publications

References 57 publications

Glutathione Self-Assembles into a Shell of Hydrogen-Bonded Intermolecular Aggregates on “Naked” Silver Nanoparticles

Glutathione Self-Assembles into a Shell of Hydrogen-Bonded Intermolecular Aggregates on “Naked” Silver Nanoparticles

Flat, Cα,β‐Didehydroalanine Foldamers with Ferrocene Pendants: Assessing the Role of α‐Peptide Dipolar Moments

A polarization scheme that resolves cross-peaks with transient absorption and eliminates diagonal peaks in 2D spectroscopy

Contact Info

Product

Resources

About

¹³C═¹⁸O/¹⁵N Isotope Dependence of the Amide-I/II 2D IR Cross Peaks for the Fully Extended Peptides

Flat, C^α,β‐Didehydroalanine Foldamers with Ferrocene Pendants: Assessing the Role of α‐Peptide Dipolar Moments