The property that a molecule and its mirror image cannot overlap is called molecular chirality. Natural molecules often exist as one of two enantiomers, such as natural L-type amino acids and D-type sugars. Since drug targets in the human body (such as various receptors, enzymes, proteins, etc.) are composed of L-type amino acids which are inherently chiral, and chiral drug molecules must have corresponding selectivity when they interact with them to produce pharmacological effects. Therefore, enantiomers often produce different or even opposite pharmacological activities in the human body, such as thalidomide and ibuprofen. The determination of the absolute configuration of chiral molecules will inevitably become an extremely important and long-standing subject. Circular dichroism (CD) is commonly used to confirm the stereochemical structure of compounds. As a new method for measuring the circular dichroism of molecules in the infrared wavelength region, VCD has greatly expanded the application range of circular dichroism. Scientists use it to accurately predict chirality through conformational search and quantum chemical calculations, and the chromatogram of the vibrational circular dichroism of the molecule is compared with the measured spectrum to determine its absolute configuration.
Figure 1. Conformational analysis of cationic antimicrobial peptides using VCD. (Kocourková, L.; et al. 2016)
Application of VCD Spectrum Prediction
- Protein folding/conformation studies
- Purity detection of optically active substances
- Qualitative/quantitative analysis of chiral drugs
- Nanomaterials and supramolecular self-assembly research
- Characterization of solid chiral materials
- Chiral molecular structure analysis
- Metal complex/polymer chemistry
- Natural organic chemistry and stereo organic chemistry
- Physical chemistry/biochemistry and macromolecules
Our VCD Spectrum Prediction Workflow
Alfa Chemistry has established a validated process for VCD spectrum prediction.
1. Conformation search
CONFLEX is used for conformation search and preliminary sorting, and Gibbs free energy is calculated according to the MMFF94 force field of CONFLEX.
- Adopt exhaustive conformation search strategy
- Consider the entropy change
- Consider the solvent effect
2. VCD calculation
We apply GaussView 6 to read the CONFLEX conformation search result file and select the optimal conformations with the lowest energy for VCD calculation.
- Perform precise conformation optimization and VCD spectrum calculation for different conformations of a molecule
- Perform optimization and frequency calculations
- Use density functional theory for calculation at the theoretical level of APFD/6-311g(2d,p).
3. Generate Boltzmann weighted average VCD map
Our Services
- In addition to CONFLEX and GMMX, Forge and Torch can also be used to search for conformation, providing a variety of strategies for conformation search.
- Alfa Chemistry delivers the calculated optimized structures, frequencies, and rotational strengths.
Our vibration circular dichroism (VCD) spectrum prediction services remarkably reduce the cost, promote further experiments, and enhance the understanding of chemical process for customers worldwide. Our personalized and all-around services will satisfy your innovative study demands. If you are interested in our services, please don't hesitate to contact us. We are glad to cooperate with you and witness your success!
Reference
- Kocourková, L.; et al. Vibrational and electronic circular dichroism as powerful tools for the conformational analysis of cationic antimicrobial peptides. Monatshefte für Chemie-Chemical Monthly. 2016, 147(8): 1-7.