When the incident light interacts with the vibration mode of the molecule, it will result in the inelastic scattering of photons and cause the frequency of the emitted light to change relative to the incident light, which is also called Raman activity. The spectrum formed based on this scattering is called Raman spectrum. For some molecules, when the incident light is circularly polarized light, the scattering intensity of left and right circularly polarized light will be different. The difference between these two intensities is defined as Raman optical activity (ROA). The sensitivity of ROA spectra to stereochemistry provides a wealth of detailed information about both structure and conformational dynamics, such as tertiary folding, secondary structure and even the orientation of individual residues in proteins and nucleic acids. In addition, ROA can directly monitor the stereochemistry of chiral molecules and is now used as an incisive probe of biomolecular structure.
Figure 1. Raman optical activity (ROA) in a silver trimer of C2v symmetry. (Chuntonov, L.; Haran, G. 2013)
Our ROA Prediction Process
Alfa Chemistry has created an optimized and validated process for ROA prediction:
- Structural optimization and frequency calculation
First, we optimize the molecular structure including the structure of its enantiomers, and calculate the frequency at the same time. We also save the check file (that is, the .chk file).
- ROA calculation
Then we use the structure and wave function in the check file of the previous step as the initial structure and initial assumption of the wave function, respectively. A larger basis set is applied to calculate the Raman optical activity.
- Result analysis
Raman optical activity can provide various information about the molecular chiral center, such as vibration intensity and Raman scattering intensity at different frequencies, which allows us to determine the absolute structure of the molecule by comparing the Raman optical activity measured by calculation and experiment.
- For flexible molecules, we conduct a comprehensive conformation search and the calculation results are Boltzmann averaged.
- In order to accurately predict the Raman optical activity spectrum, we use a basis set with a dispersion function.
- Our scientist fully consider the influence of the solvent to obtain a reliable results of the measurement in the solvent.
ROA prediction provides detailed information about both structure and conformational dynamics. Our ROA 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!
- Chuntonov, L.; Haran, G. Optical activity in single-molecule surface-enhanced Raman scattering: Role of symmetry. Mrs Bulletin. 2013, 38(8): 642-647.