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Solvation and the secondary structure of a proline-containing dipeptide: insights from VCD spectroscopy.
Phys Chem Chem Phys. 2020 Jul 21; 22(27):15640-15648.PC

Abstract

In this study we investigate the IR and VCD spectra of the diastereomeric dipeptide Boc-Pro-Phe-(n-propyl) 1 in chloroform-d1 (CDCl3) and the strongly hydrogen bonding solvent dimethylsulfoxide-d6 (DMSO-d6). From comparison of the experimental spectra, the amide II spectral region is identified as marker signature for the stereochemistry of the dipeptide: the homochiral LL-1 features a (+/-)-pattern in the amide II region of the VCD spectrum, while the amide II signature of the diastereomer LD-1 is inverted. Computational analysis of the IR and VCD spectra of LL-1 reveals that the experimentally observed amide II signature is characteristic for a βI-turn structure of the peptide. Likewise, the inverted pattern found for LD-1 arises from a βII-turn structure of the dipeptide. Following a micro-solvation approach, the experimental spectra recorded in DMSO-d6 are computationally well reproduced by considering only a single solvent molecule in a hydrogen bond with N-H groups. Considering a second solvent molecule, which would lead to a cleavage of intramolecular hydrogen bonds in 1, is found to give a significantly worse match with the experiment. Hence, the detailed computational analysis of the spectra of LL- and LD-1 recorded in DMSO-d6 confirms that the intramolecular hydrogen bonding pattern, that stabilizes the β-turns and other conformations of LL- and LD-1 in apolar solvents, remains intact. Our findings also show that it is essential to consider solvation explicitly in the analysis of the IR and VCD spectra of dipeptides in strongly hydrogen bonding solvents. As the solute-solvent interactions affect both conformational preferences and spectral signatures, it is also demonstrated that this inclusion of solvent molecules cannot be circumvented by applying fitting procedures to non-solvated structures.

Authors+Show Affiliations

Ruhr-Universität Bochum, Fakultät für Chemie und Biochemie, Organische Chemie II, Universitätsstraβe 150, 44801 Bochum, Germany. christian.merten@ruhr-uni-bochum.de.No affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

32617548

Citation

Vermeyen, Tom, and Christian Merten. "Solvation and the Secondary Structure of a Proline-containing Dipeptide: Insights From VCD Spectroscopy." Physical Chemistry Chemical Physics : PCCP, vol. 22, no. 27, 2020, pp. 15640-15648.
Vermeyen T, Merten C. Solvation and the secondary structure of a proline-containing dipeptide: insights from VCD spectroscopy. Phys Chem Chem Phys. 2020;22(27):15640-15648.
Vermeyen, T., & Merten, C. (2020). Solvation and the secondary structure of a proline-containing dipeptide: insights from VCD spectroscopy. Physical Chemistry Chemical Physics : PCCP, 22(27), 15640-15648. https://doi.org/10.1039/d0cp02283g
Vermeyen T, Merten C. Solvation and the Secondary Structure of a Proline-containing Dipeptide: Insights From VCD Spectroscopy. Phys Chem Chem Phys. 2020 Jul 21;22(27):15640-15648. PubMed PMID: 32617548.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Solvation and the secondary structure of a proline-containing dipeptide: insights from VCD spectroscopy. AU - Vermeyen,Tom, AU - Merten,Christian, Y1 - 2020/07/03/ PY - 2020/7/4/pubmed PY - 2020/7/4/medline PY - 2020/7/4/entrez SP - 15640 EP - 15648 JF - Physical chemistry chemical physics : PCCP JO - Phys Chem Chem Phys VL - 22 IS - 27 N2 - In this study we investigate the IR and VCD spectra of the diastereomeric dipeptide Boc-Pro-Phe-(n-propyl) 1 in chloroform-d1 (CDCl3) and the strongly hydrogen bonding solvent dimethylsulfoxide-d6 (DMSO-d6). From comparison of the experimental spectra, the amide II spectral region is identified as marker signature for the stereochemistry of the dipeptide: the homochiral LL-1 features a (+/-)-pattern in the amide II region of the VCD spectrum, while the amide II signature of the diastereomer LD-1 is inverted. Computational analysis of the IR and VCD spectra of LL-1 reveals that the experimentally observed amide II signature is characteristic for a βI-turn structure of the peptide. Likewise, the inverted pattern found for LD-1 arises from a βII-turn structure of the dipeptide. Following a micro-solvation approach, the experimental spectra recorded in DMSO-d6 are computationally well reproduced by considering only a single solvent molecule in a hydrogen bond with N-H groups. Considering a second solvent molecule, which would lead to a cleavage of intramolecular hydrogen bonds in 1, is found to give a significantly worse match with the experiment. Hence, the detailed computational analysis of the spectra of LL- and LD-1 recorded in DMSO-d6 confirms that the intramolecular hydrogen bonding pattern, that stabilizes the β-turns and other conformations of LL- and LD-1 in apolar solvents, remains intact. Our findings also show that it is essential to consider solvation explicitly in the analysis of the IR and VCD spectra of dipeptides in strongly hydrogen bonding solvents. As the solute-solvent interactions affect both conformational preferences and spectral signatures, it is also demonstrated that this inclusion of solvent molecules cannot be circumvented by applying fitting procedures to non-solvated structures. SN - 1463-9084 UR - https://www.unboundmedicine.com/medline/citation/32617548/Solvation_and_the_secondary_structure_of_a_proline-containing_dipeptide:_insights_from_VCD_spectroscopy L2 - https://doi.org/10.1039/d0cp02283g DB - PRIME DP - Unbound Medicine ER -
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