Sampling of the conformational space of peptides and saccharides with first-principle accuracy is critical as such a database provide a solid base to interpret experimental measurements such as Infrared photo-dissociation (IRPD) spectroscopy, ion mobility spectrometry (IMS), or collision-induced dissociation (CID). The conformational space of both peptides and saccharides are highly flexible, in which the distinct conformers of mono- and di-saccharide is estimated to be in the order of 103 and 106, respectively. To efficiently explore the diverse conformational space of saccharide without losing accuracy, we developed a multi-level sampling scheme integrating semi-empirical models, density function theory (DFT) and neural network potential (NNP) that can be routinely be applied to study di-saccharides and hexa-peptides[1-8]. Preliminary results, shown on the right, demonstrate the decent agreement between experimental IRPD spectra[9] and IR absorption simulated based on low-energy conformers of sodiated Gal-14GlcNAc at DFT. We are optimistic that the combination of theory and gas-phase experimental can provide a new dimension into explore the structures of these bio-molecules.

References

[1] S. Jindal, P-J Hsu, H. T. Phan, P-K Tsou, J-L Kuo, Phys. Chem. Chem. Phys. 24, 27263 (2022)
[2] P-K Tsou, Hai T. Huynh, H. T. Phan, J-L Kuo, Phys. Chem. Chem. Phys. 25, 3332 (2023)
[3] H. T. Phan, P-K Tsou, P-J Hsu, J-L Kuo, Phys. Chem. Chem. Phys. 25, 5817 (2023)
[4] H-T Phan, P-K Tsou, P-J Hsu and J-L Kuo, Phys. Chem. Chem. Phys. 26, 9556 (2024)
[5] H-C Dong, P-J Hsu and J-L Kuo, Phys. Chem. Chem. Phys. 26, 11125 (2024)
[6] P-K Tsou, H. T. Phan, J-L Kuo, Phys. Chem. Chem. Phys. 27, 4355 (2025)
[7] G. Song, H-N Jeon, J-L Kuo and H. Kang, Phys. Chem. Chem. Phys. 27, 14444 (2025)
[8] H-T Phan, P-K Tsou, H-C Dong, P-J Hsu and J-L Kuo, Phys. Chem. Chem. Phys. 27, 11780 (2025)
[9] C. Masellis, N. Khanal, M. Kamrath, D. Clemmer, T. R. Rizzo, J. Am. Soc. Mass Spectrom. 28, 2217 (2017)