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Witkowski M, Trzybiński D, Pawlędzio S, Woźniak K, Dzwolak W, Królikowska A. The Structural Characterisation and DFT-Aided Interpretation of Vibrational Spectra for Cyclo(l-Cys-d-Cys) Cyclic Dipeptide in a Solid State. Molecules 2023; 28:5902. [PMID: 37570871 PMCID: PMC10421304 DOI: 10.3390/molecules28155902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 07/25/2023] [Accepted: 08/01/2023] [Indexed: 08/13/2023] Open
Abstract
Cyclic dipeptides with two intramolecular peptide bonds forming a six-membered 2,5-diketopiperazine ring are gaining significant attention due to their biological and chemical properties. Small changes in the local geometry of such molecules (from cis to trans) can lead to significant structural differences. This work presents the results of a study of cyclo(l-Cys-d-Cys), a dipeptide comprising two cysteine molecules in opposite chiral configurations, with the functional groups situated at both sides of the diketopiperazine ring. X-ray diffraction (XRD) experiment revealed that the molecule crystallises in the P-1 space group, which includes the centre of inversion. The IR and Raman vibrational spectra of the molecule were acquired and interpreted in terms of the potential energy distribution (PED) according to the results of density functional theory (DFT) calculations. The DFT-assisted analysis of energy frameworks for the hydrogen bond network within molecular crystals was performed to support the interpretation of X-ray structural data. The optimisation of the computational model based on three-molecule geometry sections from the crystallographic structure, selected to appropriately reflect the intermolecular interactions responsible for the formation of 1D molecular tapes in cyclo(l-Cys-d-Cys) crystal, allowed for better correspondence between theoretical and experimental vibrational spectra. This work can be considered the first complete structural characterisation of cyclo(l-Cys-d-Cys), complemented via vibrational spectroscopy results with full band assignment aided with the use of the DFT method.
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Affiliation(s)
- Marcin Witkowski
- Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warszawa, Poland
| | - Damian Trzybiński
- Biological and Chemical Research Centre, Chemistry Department, University of Warsaw, Żwirki i Wigury 101, 02-089 Warszawa, Poland
| | - Sylwia Pawlędzio
- Biological and Chemical Research Centre, Chemistry Department, University of Warsaw, Żwirki i Wigury 101, 02-089 Warszawa, Poland
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Krzysztof Woźniak
- Biological and Chemical Research Centre, Chemistry Department, University of Warsaw, Żwirki i Wigury 101, 02-089 Warszawa, Poland
| | - Wojciech Dzwolak
- Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warszawa, Poland
- Biological and Chemical Research Centre, Chemistry Department, University of Warsaw, Żwirki i Wigury 101, 02-089 Warszawa, Poland
| | - Agata Królikowska
- Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warszawa, Poland
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Varughese KI, Lu CT, Kartha G. Crystal structure and conformation of cyclo-L-cystine. INTERNATIONAL JOURNAL OF PEPTIDE AND PROTEIN RESEARCH 1981; 18:88-102. [PMID: 7309371 DOI: 10.1111/j.1399-3011.1981.tb02043.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
X-ray crystallographic investigations on cyclo-L-cystine show that the diketopiperazine ring is in a twisted boat form and the C-S-S-C bridge across the C alpha atoms has a negative chirality with chi 3 angle of - 94 degrees, The two peptides are significantly nonplanar with the omega values of - 10 degrees and - 16 degrees. The crystals are orthorhombic, space group P212121 with a = 11.216(4), b = 12.874(4), c = 5.978(3) and Z = 4. The structure was solved by heavy atom method and refined to an R index of 0.065.
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