Methyl torsional state analysis of the jet-cooled microwave spectrum of N-acetylglycine

Lovas, Francis J.; Lavrich, Richard J.; Plusquellic, David F.

doi:10.1016/j.jms.2004.04.005

Cited by 11 publications

(8 citation statements)

References 26 publications

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“…The molecules considered in this study are shown in Figure . Each of the structures contains one or more methyl groups attached to one or more peptide bonds and includes (i) the trans form of N -methyl-acetamide (MA t ), (ii) the planar form of N -acetyl-glycine (AG I ), (iii) the planar and nonplanar forms of ethylacetamidoacetate (EAA I and EAA II ), (iv) the C 7 eq form of alanine dipeptide (AD 7eq ), and (v) the trans down-puckered ring form of proline dipeptide (PD tCd ) . For these five model systems, torsional barriers have been determined for all nine of the methyl groups attached to the N- and C-termini of the peptide bonds.…”

Section: Microwave and Ab Initio Resultsmentioning

confidence: 99%

Probing the Electronic Structure of Peptide Bonds Using Methyl Groups

Plusquellic

Pratt

2007

J. Phys. Chem. A

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The observed V3 torsional barriers measured by microwave spectroscopy for nine methyl groups attached alpha to peptide bond linkages in five gas-phase biomimetics have been found to differ considerably from one molecule to the next and even depend on the position of substitution, being sensitive to structural changes at the other end of the peptide bond. In the search for an explanation for these results, ab initio calculations have been performed at the HF/6-311++G(d,p) level of theory and interpreted in terms of the natural bond orbitals and resonance structures of the peptide bond. These calculations reveal that resonance delocalization in peptide bonds is influenced by methyl conformation through the coupling of vicinal sigma to sigma* orbital interactions with the n to pi*. Thus, CN double-bond character increases (and CO double-bond character decreases) as the methyl group is rotated from the syn to the anti position. A quasilinear correlation exists between the barriers to internal rotation of attached methyl groups and the relative importance of the two principal resonance structures that contribute to the peptide bond.

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Section: Microwave and Ab Initio Resultsmentioning

confidence: 99%

Probing the Electronic Structure of Peptide Bonds Using Methyl Groups

Plusquellic

Pratt

2007

J. Phys. Chem. A

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“…[34] These methyl torsional barriers vary due to the energetic differences in the Lewis and non-Lewis or hyperconjugative delocalization interactions between the occupied σ orbitals of the methyl group and the σ and π bonding and antibonding orbitals of the neighboring CÀ N and C=O bonds at the minima and maxima values on the V 3 potential surface. [32,[35][36][37] When comparing the conformers like Trans-I, Ac-Ser-NH 2 [38] has the lowest V 3 barrier with a value of 97.2 cm À 1 , followed by Ac-Ala-N-methyl amide [33] with V 3 = 98.5 cm À 1 , then Ac-Cys-NH 2 [25] showing a value of V 3 = 100.32 cm À 1 , with the highest value being for Trans-I in this work with V 3 = 123.87 cm À 1 . This is interesting as there is a clear correlation between the strength of the intramolecular hydrogen bond with the carbonyl in the acetyl group, that changes the V 3 barrier height of the methyl group.…”

Section: Methyl Internal Rotationmentioning

confidence: 99%

Impact of the Acetyl Group on Cysteine: A Study of N‐Acetyl‐Cysteine through Rotational Spectroscopy

Mato,

Municio,

Alonso

et al. 2024

ChemPhysChem

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Herein, we report a spectroscopic study of N‐acetyl‐L‐cysteine, an important antioxidant drug, using Fourier‐transform microwave techniques and in isolated conditions. Two conformers are observed, where most stable structure adopts a cis disposition, and the second conformer has a lower abundance and adopts a trans disposition. The rotational constants and the barriers to methyl internal rotation are determined for each conformer, allowing a precise conformation identification. The results show that the cis form adopts an identical structure in the crystal, solution, and gas phases. Additionally, the structures are contrasted against those of cysteine

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“…Each minimum along the PES corresponds to a particular conformation of Nacetylglycine. In contrast to the previous studies of the Nacetylglycine conformation structure, 27,28 we identified a full set of conformers, comprised of 15 structures. An analysis of the relative energies (MP2/aug-cc-pVTZ) and relative Gibbs free energies (CCSD(T)/CBS) has shown that at evaporation temperature only three conformers have populations in excess of 1%.…”

Section: Conformer Population In Ftir Spectra Of N-acetylglycine In Amentioning

confidence: 99%

“…An analysis of the relative energies (MP2/aug-cc-pVTZ) and relative Gibbs free energies (CCSD(T)/CBS) has shown that at evaporation temperature only three conformers have populations in excess of 1%. The main conformer-NAG1 (we used the standard notations for N-acetylglycine conformers 27,28 ) is stabilized by the strong intramolecular hydrogen bond C c ¼ O•••H-N and has a flat frame of heavy atoms (Fig. 1).…”

Section: Conformer Population In Ftir Spectra Of N-acetylglycine In Amentioning

confidence: 99%

Effect of low-temperature argon matrices on the IR spectra and structure of flexible N-acetylglycine molecules

Stepanian

Ivanov

Adamowicz³

2016

Low Temperature Physics

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A study of how the matrix environment impacts the structure and IR spectra of N-acetylglycine conformers. The conformational composition of this compound is determined according to an analysis of the FTIR spectra of N-acetylglycine isolated in low temperature argon matrices. Bands of three N-acetylglycine conformers are identified based on the spectra: one major and two minor. The structure of all observed conformers is stabilized by different intramolecular hydrogen bonds. The Gibbs free energies of the conformers were calculated (CCSD(T)/CBS method), and these energy values were used to calculate conformer population at a temperature of 360 K, of which 85.3% belonged to the main conformer, and 9.6% and 5.1% to the minor conformers. We also determined the size and shape of the cavities that form when the N-acetylglycine conformers are embedded in the argon crystal during matrix deposition. It is established that the most energetically favorable cavity for the planar main conformer is the cavity that forms when 7 argon atoms are replaced. At the same time, bulky minor conformers were embedded into cavities that correspond to 8 removed argon atoms. We calculated the complexation energy between argon clusters and conformers, and the deformation energy of the argon crystal and the N-acetylglycine conformers. The matrix-induced shifts to the conformer oscillation frequency are calculated.

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Methyl torsional state analysis of the jet-cooled microwave spectrum of N-acetylglycine

Cited by 11 publications

References 26 publications

Probing the Electronic Structure of Peptide Bonds Using Methyl Groups

Probing the Electronic Structure of Peptide Bonds Using Methyl Groups

Impact of the Acetyl Group on Cysteine: A Study of N‐Acetyl‐Cysteine through Rotational Spectroscopy

Effect of low-temperature argon matrices on the IR spectra and structure of flexible N-acetylglycine molecules

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