Reliability of computed signs and intensities for vibrational circular dichroism spectra

Góbi, Sándor; Magyarfalvi, Gábor

doi:10.1039/c1cp21645g

Cited by 57 publications

(84 citation statements)

References 19 publications

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“…The higher of the two thresholds, T E and T C , will be selected to apply to both experimental and calculated DF/CID spectra in calculating the spectral similarity. For example, in measuring the VCD spectra the absolute values of vibrational dissymmetry factor (VDF) less than 10 ‐5 are not routinely measurable and calculated VDF magnitudes, using the criterion of Gobi and Magyarfalvi, less than 4x10 ‐5 may not be reliable . Thus, the use of

|g (\overset{ν}{true})| > 4 \times 10^{- 5}

consistently for both experimental and calculated VDF spectra would satisfy the robustness criteria for VDFs.…”

Section: Spectral Simulations and Analysismentioning

confidence: 99%

Comparison of Experimental and Calculated Chiroptical Spectra for Chiral Molecular Structure Determination

2014

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For three different chiroptical spectroscopic methods, namely, vibrational circular dichroism (VCD), electronic circular dichroism (ECD), and Raman optical activity (ROA), the measures of similarity of the experimental spectra to the corresponding spectra predicted using quantum chemical theories are summarized. In determining the absolute configuration and/or predominant conformations of chiral molecules, these similarity measures provide numerical estimates of agreement between experimental observations and theoretical predictions. Selected applications illustrating the similarity measures for absorption, circular dichroism, and corresponding dissymmetry factor (DF) spectra, in the case of VCD and ECD, and for Raman, ROA, and circular intensity differential (CID) spectra in the case of ROA, are presented. The analysis of similarity in DF or CID spectra is considered to be much more discerning and accurate than that in absorption (or Raman) and circular dichroism (or ROA) spectra, undertaken individually.

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|g (\overset{ν}{true})| > 4 \times 10^{- 5}

consistently for both experimental and calculated VDF spectra would satisfy the robustness criteria for VDFs.…”

Section: Spectral Simulations and Analysismentioning

confidence: 99%

Comparison of Experimental and Calculated Chiroptical Spectra for Chiral Molecular Structure Determination

2014

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“…Since the rotatory strength (i.e., the intensity) of a VCD band is proportional to the scalar product of these values, angles close to 90° were supposed to indicate that even very small structural changes or small external perturbations can result in sign change for these vibrational modes. As shown later by the present authors, and Nicu and Baerends, this angle is gauge‐dependent, and, for example, this can lead to wrong classification of vibrational modes of large molecules, e.g., that of longer peptide chains. To overcome this problem an alternative gauge‐independent measure of the robustness has recently been suggested by some of the present authors, which utilizes the ratio between the rotational and the dipole strength, ζ k = R k /D k .…”

Section: Methods and Computational Detailsmentioning

confidence: 61%

VCD Robustness of the Amide‐I and Amide‐II Vibrational Modes of Small Peptide Models

2015

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The rotational strengths and the robustness values of amide-I and amide-II vibrational modes of For(AA)n NHMe (where AA is Val, Asn, Asp, or Cys, n = 1-5 for Val and Asn; n = 1 for Asp and Cys) model peptides with α-helix and β-sheet backbone conformations were computed by density functional methods. The robustness results verify empirical rules drawn from experiments and from computed rotational strengths linking amide-I and amide-II patterns in the vibrational circular dichroism (VCD) spectra of peptides with their backbone structures. For peptides with at least three residues (n ≥ 3) these characteristic patterns from coupled amide vibrational modes have robust signatures. For shorter peptide models many vibrational modes are nonrobust, and the robust modes can be dependent on the residues or on their side chain conformations in addition to backbone conformations. These robust VCD bands, however, provide information for the detailed structural analysis of these smaller systems.

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“…Meanwhile, the spectrum of (L, L)‐ F1 gel also exhibited a negative signal and a positive signal at 1627 and 1635 cm −1 , thus suggesting the carbonyl groups of (L, D)‐ F1 and (L, L)‐ F1 should stack in a left‐handed manner. The VCD signals appeared in all the investigated region exhibited a vibrational dissymmetry factor (ΔA/A) within the order of 10 −3 to 10 −4 , which satisfied the criterion introduced by Góbi and Magyarfalvi and clearly indicated the reliability of VCD measurement according to the previous study of Zinna and Pescitelli . Overall, VCD study clearly demonstrated that the chirality of alanine at N ‐terminal determined the stacking chirality of carbonyl groups.…”

Section: Resultsmentioning

confidence: 98%

Helicity of perfluoroalkyl chains controlled by the self‐assembly of the Ala‐Ala dipeptides

Zhang

Tong

et al. 2019

Chirality

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Four Ala‐Ala dipeptides with a perfluoroalkyl chain at the N‐terminal were synthesized. They were able to self‐assemble into helical nanofibers and/or twisted nanobelts in a mixture of DMSO/H2O. The handedness of nanofibers and nanobelts was controlled by the chirality of the alanine at the N‐terminal. The stacking handedness of the phenylene groups and the helicity of the perfluoroalkyl chain were studied using circular dichroism spectroscopy and vibrational circular dichroism, respectively. The chirality of the alanine at N‐terminal controlled the stacking handedness of the neighboring phenylene groups. Moreover, due to the low potential barrier between M‐ and P‐helices of the perfluorocarbon chain, the handedness of the organic self‐assemblies eventually controlled the helicity of the perfluorocarbon chain. X‐ray diffraction indicated that a lamellar structure was formed by the dimers of the dipeptides.

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Reliability of computed signs and intensities for vibrational circular dichroism spectra

Cited by 57 publications

References 19 publications

Comparison of Experimental and Calculated Chiroptical Spectra for Chiral Molecular Structure Determination

Comparison of Experimental and Calculated Chiroptical Spectra for Chiral Molecular Structure Determination

VCD Robustness of the Amide‐I and Amide‐II Vibrational Modes of Small Peptide Models

Helicity of perfluoroalkyl chains controlled by the self‐assembly of the Ala‐Ala dipeptides

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