Analysis on the terahertz spectral characteristics of two types of sialic acids in solid state and aqueous solution

In this study, N-acetylneuraminic acid (Neu5Ac) and N-glycolylneuraminic acid (Neu5Gc) were chosen as representative sialic acids to study their terahertz (THz) spectral characteristics in solid and aqueous states. Firstly, the structures of the two sialic acids were determined and analyzed in detail using powder X-ray diffraction (PXRD) laying the foundation for the subsequent simulation calculations. Secondly, the THz time-domain spectroscopy (THz-TDS) system was used to measure their spectral properties in solid state. Thirdly, the molecular structures of the two sialic acids were simulated using Material Studio (MS) software, and their vibrational modes were analyzed using solid-state density functional theory (DFT). Then, to compare the THz spectral characteristics in solid and aqueous states, microfluidic technology was introduced to measure the THz spectra of the sialic acids in aqueous solutions. The results indicate that there are differences in the THz spectra of the two sialic acids in their solid and aqueous solution states. Finally, THz spectroscopy was conducted on a common edible sialic acid powder, revealing that the absorption coefficient spectrum of the powder exhibited characteristic absorption peaks of Neu5Ac. This study provides a reference for the analysis of biomolecules.