PHYSICAL CHEMISTRY CHEMICAL PHYSICS
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2022
·Vol. 24
·期 39
·24535-24541
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IF 3.945
Lu Qian,Xin Guo,Kai Zhang,Miao Yu
Water is essential in the evolution of life and plays an important role in the structure and function of the basic substances of life, such as protein and DNA. However, the specific details of the role of water with respect to chitin, the most abundant biomacromolecule on Earth after cellulose, remain unclear. In this study, atomic force microscopy (AFM)-based single-molecule force spectroscopy (SMFS) was used to explore the effects of hydrogen bonds (H-bonds) on the single-molecule mechanics of chitin. Comparative experiments showed that a single chitin chain exhibited the same single-chain natural elasticity as cellulose in nonane, indicating that a single chitin chain can form strong intrachain H-bonds in nonane. Moreover, the single-chain elasticity of chitin obtained in dimethyl sulfoxide (DMSO) was consistent with that of cellulose, and both superposed well with the theoretical model (QM-FJC) to show the single-chain elasticity of the chitin/cellulose backbone, indicating that DMSO can eliminate almost all the intrachain H-bonds of single chitin chains. However, when water was introduced as the surrounding environment, the intrachain H-bonds of chitin were found to be weaker than those of cellulose, which is supported by the AFM mapping results. Single-molecule studies reveal that water is a unique solvent for chitin, and the nanomechanics and hydrophobicity of chitin can be influenced by an external solvent (water in this work) through regulation of the intrachain H-bonds. The present study casts new insight into the role of H-bonds and water in the structures and functions of polysaccharides.
研究领域:
生物物理学
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分子生物学
✓ 已验证
DOI
高影响因子
POLYMER
·
2025
·
IF 4.5
Yifan Chen,Wentao Yuan,Yingxin Zhang,Hu-jun Qian,Zhong-yuan Lu,Shuxun Cui
According to the principle of polymer science, the gelation process of κ-carrageenan should start with polymer chains in a disordered coil conformation. However, the coil-helix model has been challenged by recent studies, which pointed out that in deionized water, κ-carrageenan exists in single-helix conformation rather than random coil. Here, we employ single-molecule force spectroscopy (SMFS) to investigate its conformation under different conditions at the single-chain level. Direct evidence for the existence of random coil state is obtained. In addition, it is found that coil-single helix transition can be induced by external Na + ions, which can screen the charges of the sulfated groups in κ-carrageenan. Thus, the mechanism of the first step of κ-carrageenan gelation is revealed, which lays a solid foundation for better understanding of the entire gelation process.
研究领域:
高分子科学
·
生物物理学
·
食品科学
✓ 已验证
产品关联
DOI
高影响因子
Journal of Physical Chemistry Letters
·
2023
·
IF 5.7
Tianyu Cai,Jiaqing Zhang,Jingjing Deng,Qinman Tian,Ruoqi Zhang,Haokai Geng,Yuedong Liu,Keding Zhong,Liting Wen,Chunxiang Liu,Xun Hu,Yuehui Li,Zhipeng Li,Shipeng Hao,Kai Yang,Huizhong Xu
DNA alkylating agents are widely used in anticancer pharmacology. Although shown to induce cross-linking and/or methylation of DNA, how they affect the mechanical properties of DNA and activity of DNA enzymes remains to be elucidated. Here, we perform single-molecule optical tweezer experiments on DNA treated with alkylating agents, including melphalan, cisplatin, and dacarbazine. While all three drugs induce a significant increase of overstretching force and a reduction of hysteresis, suggesting stabilization of DNA against shearing forces, their effects on elasticity of DNA were quite different, with the largest change in persistence length induced by cisplatin. Furthermore, we find that these alkylating-agent-induced changes on DNA have different effects on processivity of DNA polymerase, with melphalan and cisplatin showing significantly reduced activity and dacarbazine showing little effect. Overall, our results provide new insights into the effects for these alkylating agents, which could potentially facilitate a better design of related drugs.
研究领域:
生物化学
·
生物物理
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分子生物学
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药理学
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癌症研究
✓ 已验证
DOI
高影响因子
Catalysis Science & Technology
·
2024
·
IF 4.4
Mengsha Li,Cai You,Fei Guo,Qingfang Han,Xixian Xie,Lijuan Ma,Shengying Li,Lei Du,Xiang Sheng,Hao Su
Uridine diphosphate glucosyltransferase (UGT) from Rhodiola rosea shows high selectivity towards the phenolic hydroxyl group in the glucosylation of p-hydroxybenzyl alcohol (HBA). However, the detailed catalytic mechanism, including the substrate binding mechanism and the origins of the regioselectivity remain unclear. In this work, we solved the crystal structure of the enzyme and elucidated the molecular basis of the catalytic mechanism using site-directed mutagenesis and multiscale computational studies. Our results indicate that the conformational change of a loop region from the “open” to the “closed” state is crucial for the formation of the active enzyme-substrates ternary complex, and the loop conformation change is favored by the substrate binding. The quantum mechanical/molecular mechanical (QM/MM) and quantum chemical calculation results suggest that the catalytic power of RrUGT3 is mainly originated from the preorganized protein environment that stabilizes the catalytically active state of the sugar donor uridine-5'-diphosphate-glucose (UDPG). Moreover, the favored substrate binding and lower activation barrier of the phenolic glycosylation dictate the regiopreference of the enzyme. These results expand our knowledge on the catalytic mechanism of UGTs, and will facilitate the rational modification and design of highly active and regioselective UGT variants for the practical production of glycosides.
研究领域:
生物化学
·
分子生物学
·
酶学
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计算化学
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）