Arabinogalactan (AG) and sulphated arabinogalactans which are products of chemical modification of arabinogalactan polysaccharide with anticoagulant properties were studied by experimental infrared (IR) spectroscopy combined with density functional theory simulations. Mutual analysis of experimental and theoretical IR frequencies indicates that the discrepancies between experiment and theory is caused by the influence of –OH groups, which led to the energy shift and broadening of the absorption IR bands. It was found that theoretical and experimental spectra correspond well within the 3000–4000 cm⁻¹ spectral region. Addition of sulphur group in AG structure causes hydroxyl group to become accessible for further sulphation. The difference between experimental and theoretical IR frequencies of sulphated AG derivatives is greater than that of the parent arabinogalactan due to the increase in the number of possible isomers and conformers.

中文翻译：

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DFT理论解释生物活性阿拉伯半乳聚糖硫酸盐衍生物的红外光谱

通过实验红外（IR）光谱结合密度泛函理论模拟研究了阿拉伯半乳聚糖（AG）和硫酸化的阿拉伯半乳聚糖，它们是具有抗凝血特性的化学修饰的阿拉伯半乳聚糖多糖。对实验和理论IR频率的相互分析表明，实验和理论之间的差异是由–OH基团的影响引起的，这导致了能量转移和吸收IR谱带的变宽。发现理论光谱和实验光谱在3000–4000 cm ^-1范围内很好地对应光谱区域。在AG结构中添加硫基团使得羟基变得可用于进一步硫酸化。由于可能的异构体和构象异构体数量的增加，硫酸化AG衍生物的实验和理论IR频率之间的差异大于母体阿拉伯半乳聚糖的差异。