NMR AND DFT STUDY OF CHONDROITIN SULPHATE

Chondroitin sulphate is a sulphated glycosaminoglycan (GAG), abundantly present in connective tissues, particularly articular cartilage. There, it plays a critical role in maintaining structural integrity and elasticity. As a key component of the extracellular matrix, it is involved in various biological processes, including cellular signalling pathways, tissue hydration, and matrix organisation [1,2]. Furthermore, the therapeutic potential of chondroitin sulphate as an agent in joint-related disorders such as osteoarthritis has been studied due to its anti-inflammatory and cartilage-protective properties [3,4]. The therapeutic potential of chondroitin sulphate lies in its ability to reduce cartilage catabolism by inhibiting extracellular matrix degradation [5].

The combination of NMR spectroscopy and density functional theory (DFT) provides valuable insights into the structure, dynamics, and solubility of glycosaminoglycans [6]. In this study, DFT calculations were performed using the MN15/6-311++G(2d,2p)//SMD approach to determine the 3D structures of chondroitin 6-sulphate and chondroitin 4-sulphate tetrasaccharides. Computed proton–proton and proton–carbon coupling constants revealed that the one-bond proton–carbon coupling constants (¹J_C-H) depend strongly on the substitution position (C-6 vs. C-4). However, substitution also affects the ¹J_C-H and ³J_C-H magnitudes in the neighbouring atoms. The ¹J_C-H values were consistent with the experimental NMR values. The ³J_C-H values also revealed differences in the glycosidic linkages in chondroitin tetrasaccharides. These findings demonstrate that the position of sulphate groups on the chondroitin backbone significantly affects electronic distribution, geometry, and ⁿJ_C-H magnitudes, thereby highlighting the role of hydrogen bonding and ionic interactions in the 3D structure of chondroitin tetrasaccharides.

This work was financially supported by Slovak grant agency VEGA 2/0071/22.

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