glycosides

糖苷
  • 文章类型: Journal Article
    真菌,如红色毛癣菌(T.红花)和小孢子犬BodinAnamorph(M.犬BodinAnamorph)是皮肤病的主要病原体。根据古书记载,RumexjaponicusHoutt.(RJH)对皮肤病的治疗具有奇迹般的效果。揭示抗真菌(T.rubrum和M.canisBodinAnamorph)的成分及其机制。食醋提取和酒精沉淀,采用HPLC和核磁共振波谱(NMR)分析RJH的化学成分;研究了体外抗真菌实验,包括测试最低抑菌浓度(MIC)和最低杀菌浓度(MFC)。孢子发芽率,核酸,蛋白质渗漏率,生物膜结构,以及RJH中抗真菌和抗真菌生物膜的机制。本研究分别获得了7个蒽醌及其糖苷类化合物,比如大黄酚,physcion,芦荟大黄素,大黄素,rhein,大黄素-8-O-β-D-葡萄糖苷和大黄酚-8-O-β-D-葡萄糖苷。体外抗真菌实验结果表明,RJH提取物对皮肤癣菌具有良好的抗真菌活性。其中,大黄酸的MIC,大黄素和芦荟大黄素对红毛虫为1.9微克/毫升,3.9微克/毫升和15.6微克/毫升,大黄素和芦荟大黄素对犬科动物的MIC分别为7.8µg/ml和62.5µg/ml,分别。此外,其活性成分能抑制真菌孢子的萌发和芽管的形成,改变细胞膜通透性,防止菌丝生长,破坏生物膜结构,并下调生物膜生长粘附期凝集素样序列家族1的表达。研究表明RJH具有一定的杀真菌作用。
    Fungi, such as Trichophyton rubrum (T. rubrum) and Microsporum canis Bodin Anamorph (M. canis Bodin Anamorph) are the main pathogens of dermatophysis. According to ancient books records, Rumex japonicus Houtt. (RJH) has a miraculous effect on the treatment of dermatophysis. To reveal the anti-fungi (T. rubrum and M. canis Bodin Anamorph) components and its mechanism of the Rumex japonicus Houtt. The vinegar extraction and alcohol precipitation, HPLC and nuclear magnetic resonance spectroscopy (NMR) were employed for analyzing the chemical compositions of RJH; in vitro anti-fungal experiment was investigated including test the minimum inhibitory concentration (MIC) and the minimum fungicidal concentration (MFC), spore germination rate, nucleic acid, protein leakage rate, biofilm structure, and the mechanism of anti-fungal and anti-fungal biofilms in RJH. Seven anthraquinones and their glycoside compounds were obtained in this study respectively, such as chrysophanol, physcion, aloe-emodin, emodin, rhein, emodin-8-O-β-D-glucoside and chrysophanol-8-O-β-D-glucoside. In vitro anti-fungal experiment results showed that RJH extracts have good anti-fungal activity for dermatophytic fungi. Among them, the MIC of the rhein, emodin and aloe-emodin against T. rubrum are 1.9 µg/ml, 3.9 µg/ml and 15.6 µg/ml, respectively; the MIC of emodin and aloe-emodin against M. canis Bodin Anamorph are 7.8 µg/ml and 62.5 µg/ml, respectively. In addition, its active components can inhibit fungal spore germination and the formation of bud tube, change cell membrane permeability, prevent hyphal growth, destroy biofilm structure, and down-regulate the expression of agglutinin-like sequence family 1 of the adhesion phase of biofilm growth. The study shows that RJH play a fungicidal role.
    导出

    更多引用

    收藏

    翻译标题摘要

    我要上传

    求助全文

  • 文章类型: Journal Article
    SHPL-49是一种创新的糖苷衍生物,通过红景天苷的结构修饰合成,在临床前实验中证明了对缺血动物模型的治疗作用。第一阶段,单中心,随机化,双盲,安慰剂对照,在健康的中国志愿者中进行了SHPL-49的单剂量和多剂量给药研究。在单次递增剂量(SAD)研究中,32名受试者随机分为6:2,接受SHPL-49(30mg,75毫克,150毫克,300mg)或安慰剂,输注30分钟。在多次递增剂量(MAD)研究中,受试者随机分为6:2,接受SHPL-49(75mg,150毫克,300mg)或安慰剂,每8小时输注30分钟,持续7天。在整个研究中进行安全性评价。检测SHPL-49的血浆和尿液浓度并鉴定其代谢物。使用非房室方法计算药代动力学参数。SHPL-49在单次递增剂量(30-300mg)和多次递增剂量(75-300mg)下通常是安全且耐受性良好的。所有不良事件均为轻度,无需任何干预即可解决。未报告严重不良事件。在SAD研究中,SHPL-49表现出与剂量成正比的血浆药代动力学,峰值血浆浓度(Cmax)范围为673.83至6275.00ng/mL,血浆浓度-时间曲线下面积(AUC0-t)范围为338.57至3732.67h·ng/mL,消除半衰期(t1/2)为0.49至0.67h。在MAD中,暴露量也与剂量成比例,多次给药后无显著累积.在尿液和血浆中鉴定出四种代谢物。SHPL-49显示出良好的药代动力学,安全,在这项研究中,健康的中国志愿者在单剂量和多剂量上升给药后的耐受性情况。对于未来的治疗研究,建议以8小时间隔静脉注射SHPL-49,剂量范围为150~300mg.
    SHPL-49 is an innovative glycoside derivative that is synthesized by structural modifications of salidroside,demonstrating therapeutic effects on animal models of ischemia in pre-clinical experiments. A phase I, single-center, randomized, double-blind, placebo-controlled, single and multiple dose administration study of SHPL-49 was conducted in healthy Chinese volunteers. In single-ascending-dose (SAD) study, 32 subjects randomized 6:2 to receive SHPL-49 (30 mg, 75 mg, 150 mg, 300 mg) or placebo with 30 minutes infusion. In multiple-ascending-dose (MAD) study, subjects were randomized 6:2 to receive SHPL-49 (75 mg, 150 mg, 300 mg) or placebo with 30 minutes infusion every 8 h for 7 days. Safety evaluations were conducted throughout the studies. Plasma and urine concentrations of SHPL-49 were detected and its metabolites were identified. Pharmacokinetic parameters were calculated using noncompartmental methods. SHPL-49 was generally safe and well-tolerated at single ascending doses (30-300 mg) and multiple ascending doses (75-300 mg). All adverse events were mild and resolved without any intervention. No serious adverse events were reported. In the SAD study, SHPL-49 exhibited dose-proportional plasma pharmacokinetics, with peak plasma concentration (Cmax) ranging from 673.83 to 6275.00 ng/mL, area under the plasma concentration-time curve (AUC0-t) ranging from 338.57 to 3732.67 h·ng/mL, and elimination half-life (t1/2) ranging from 0.49 to 0.67 h. In the MAD, the exposure was also dose-proportional and there was no significant accumulation following multiple dosing. Four metabolites were identified in urine and plasma. SHPL-49 shows a favorable pharmacokinetic, safety, and tolerability profile in healthy Chinese volunteers following a single- and multiple-ascending- dose administration in this study. For future therapeutic investigations, it is recommended to administer SHPL-49 intravenously at 8-hour intervals with a dosage range of 150-300 mg.
    导出

    更多引用

    收藏

    翻译标题摘要

    我要上传

    求助全文

  • 文章类型: Journal Article
    轻度认知障碍对中老年人群构成了越来越大的挑战。已提出传统中草药如管乐肉桂和银杏叶(CG)作为改善认知和记忆功能的潜在药物。本研究以100名中国中老年人为研究对象,研究了CG对神经退行性疾病风险个体认知功能的潜在协同作用。超过90天,CG组和安慰剂组每天服用两片,每对CG片剂含有72毫克松果苷和27毫克黄酮醇苷。使用多种量表评估认知功能,并在基线时确定血液生物标志物,第45天,第90天。CG组的迷你精神状态检查得分显着改善(基线时26.5与第90天27.1,p<0.001),蒙特利尔认知评估(基线时23.4与在第90天25.3,p<0.001),和世界卫生组织生活质量(基线时81.6与第90天的84.2,p<0.001),安慰剂组得分均超过对照组。值得注意的是,Cognitrax矩阵测试和韦克斯勒记忆量表-修订版都展示了增强的记忆功能,包括长期和延迟记忆,CG干预后。此外,认知相关的血液生物标志物,包括总tau,pT181、pS199、pT231、pS396和促甲状腺激素,显著下降,而三碘甲状腺原氨酸和游离三碘甲状腺原氨酸显著增加。未报告与治疗相关的不良事件,血常规和尿常规检查保持稳定。这些发现表明,补充CG可能是增强认知和记忆功能的有效补充解决方案。
    Mild cognitive impairment poses an increasing challenge to middle-aged and elderly populations. Traditional Chinese medicinal herbs like Cistanche tubulosa and Ginkgo biloba (CG) have been proposed as potential agents to improve cognitive and memory functions. A randomized controlled trial involving 100 Chinese middle-aged and elderly participants was conducted to investigate the potential synergistic effects of CG on cognitive function in individuals at risk of neurodegenerative diseases. Over 90 days, both CG group and placebo group received two tablets daily, with each pair of CG tablets containing 72 mg echinacoside and 27 mg flavonol glycosides. Cognitive functions were assessed using multiple scales and blood biomarkers were determined at baseline, Day 45, and Day 90. The CG group exhibited significant improvements in the scores of Mini-Mental State Examination (26.5 at baseline vs. 27.1 at Day 90, p < 0.001), Montreal Cognitive Assessment (23.4 at baseline vs. 25.3 at Day 90, p < 0.001), and World Health Organization Quality of Life (81.6 at baseline vs. 84.2 at Day 90, p < 0.001), all surpassing scores in placebo group. Notably, both the Cognitrax matrix test and the Wechsler Memory Scale-Revised demonstrated enhanced memory functions, including long-term and delayed memory, after CG intervention. Moreover, cognitive-related blood biomarkers, including total tau, pT181, pS199, pT231, pS396, and thyroid-stimulating hormone, significantly decreased, whereas triiodothyronine and free triiodothyronine significantly increased. No treatment-related adverse events were reported, and routine blood and urine tests remained stable. These findings indicated that CG supplementation could potentially serve as an effective supplementary solution for enhancing cognitive and memory functions.
    导出

    更多引用

    收藏

    翻译标题摘要

    我要上传

    求助全文

  • 文章类型: Journal Article
    背景:脂质代谢失调是影响糖尿病肾病(DN)进展的关键因素。莫罗尼甙(MOR)是一种从传统中药山茱萸中分离出的主要活性化合物,我们之前的研究发现,它可以改善肾小管上皮细胞的脂质沉积。本研究旨在探讨MOR是否能改善足细胞脂质沉积及其降低DN的作用机制。
    方法:最初,利用网络药理学和生物信息学技术预测MOR与DN的关系。随后,通过分子对接研究了MOR与脂质相关蛋白的结合活性,以确定MOR如何通过这些蛋白发挥作用.在确定MOR的目标之后,进行了动物实验和细胞测试以进行验证。
    结果:使用网络药理学,生物信息学,和分子对接,预测和筛选MOR治疗DN的靶蛋白,包括PGC-1α,LXRs,ABCA1,PPARY,CD36和nephrin。特别注意MOR有效结合PGC-1α,而LXR,ABCA1、PPARY和CD36是PGC-1α的下游分子。沉默PGC-1α基因显著降低MOR的治疗效果。相反,在没有PGC-1α敲除的组中,MOR能够增加PGC-1α的表达水平并影响下游蛋白的表达。此外,通过体内和体外实验,利用脂滴染色等技术,PAS,MASSON染色,免疫荧光,和蛋白质印迹,我们发现MOR有效地提高了足细胞蛋白nephrin和脂质代谢调节蛋白PGC-1α的表达水平,PPARY,和ABCA1,同时显著抑制脂质积累启动子CD36的表达。
    结论:MOR可通过PGC-1α/LXRs/ABCA1信号通路调节足细胞内胆固醇流出,并通过PGC-1α/PPARY/CD36信号通路控制胆固醇摄入,从而改善DN中的脂质沉积。
    BACKGROUND: Dysregulation of lipid metabolism is a key factor influencing the progression of diabetic nephropathy (DN). Morroniside (MOR) is a major active compound isolated from the traditional Chinese herb Cornus officinalis, our previous research found that it can improve the lipid deposition of renal tubular epithelial cells. The purpose of this study is to explore whether MOR can improve podocyte lipid deposition and its mechanism of reducing DN.
    METHODS: Initially, we used network pharmacology and bioinformatics techniques to predict the relationship between renal lipid metabolism of MOR and DN. Subsequently, the binding activity of MOR with lipid-related proteins was studied by molecular docking to determine how MOR acts through these proteins. After determining the target of MOR, animal experiments and cell tests were carried out to verify it.
    RESULTS: Using network pharmacology, bioinformatics, and molecular docking, target proteins for MOR treatment of DN were predicted and screened, including PGC-1α, LXRs, ABCA1, PPARY, CD36, and nephrin. It is particularly noted that MOR effectively binds to PGC-1α, while LXRs, ABCA1, PPARY and CD36 are downstream molecules of PGC-1α. Silencing the PGC-1α gene significantly reduced the therapeutic effects of MOR. Conversely, in groups without PGC-1α knockdown, MOR was able to increase the expression levels of PGC-1α and influence the expression of downstream proteins. Furthermore, through in vivo and in vitro experiments, utilizing techniques such as lipid droplet staining, PAS, MASSON staining, immunofluorescence, and Western blot, we found that MOR effectively elevated the expression levels of the podocyte protein nephrin and lipid metabolism-regulating proteins PGC-1α, PPARY, and ABCA1, while significantly inhibiting the expression of the lipid accumulation promoter CD36.
    CONCLUSIONS: MOR can regulate the cholesterol efflux in podocytes via the PGC-1α/LXRs/ABCA1 signaling pathway, and control cholesterol intake via the PGC-1α/PPARY/CD36 signaling pathway, thereby ameliorating lipid deposition in DN.
    导出

    更多引用

    收藏

    翻译标题摘要

    我要上传

    求助全文

  • 文章类型: Journal Article
    杏鲍菇,一种可食用的蘑菇,以其有效的多糖而闻名,对代谢过程具有显著的调节作用。来自杏树的β-葡聚糖(WPEP)因其治疗潜力而受到关注,在用葡聚糖硫酸钠(DSS)治疗的小鼠中,在减轻结肠炎症和重组肠道微生物区系方面表现出显著的益处。本研究旨在利用DSS诱导的结肠炎小鼠来探讨WPEP改善结肠炎的疗效和潜在机制。采用代谢组学方法分析尿液和血清。研究结果表明,WPEP的给药有效地调节了DSS小鼠的代谢失衡,影响嘌呤代谢,戊糖和葡萄糖醛酸的相互转化,氨基酸代谢,初级胆汁酸生物合成,柠檬酸循环,和脂质代谢。此外,WPEP显示出通过调节多种代谢途径来调节结肠炎的能力,因此影响肠屏障的完整性,运动性,炎症,氧化应激,和豁免权。这些见解表明,WPEP是管理炎症性肠病的有前途的食品成分。
    Pleurotus eryngii, an edible mushroom recognized for its potent polysaccharides, demonstrates significant regulatory effects on metabolic processes. β-glucan (WPEP) derived from P. eryngii has been noted for its therapeutic potential, exhibiting notable benefits in alleviating colonic inflammation and restructuring gut microbiota in mice treated with dextran sodium sulfate (DSS). This study focuses on utilizing DSS-induced colitis mice to explore the efficacy and underlying mechanisms of WPEP in ameliorating colitis, employing a metabolomics approach analyzing urine and serum. The findings reveal that WPEP administration effectively regulates metabolic imbalances in DSS mice, impacting purine metabolism, pentose and glucuronic acid interconversion, amino acid metabolism, primary bile acid biosynthesis, citric acid cycle, and lipid metabolism. Furthermore, WPEP demonstrates a capacity to modulate colitis by regulating diverse metabolic pathways, consequently influencing intestinal barrier integrity, motility, inflammation, oxidative stress, and immunity. These insights suggest that WPEP is a promising food component for managing inflammatory bowel diseases.
    导出

    更多引用

    收藏

    翻译标题摘要

    我要上传

    求助全文

  • 文章类型: Journal Article
    干燥是提高白茶品质的重要阶段。然而,干燥温度对WT中关键味道化合物的影响尚不清楚。在这项研究中,靶向代谢组学,分子对接,并使用模拟反应研究了在60、80和100°C干燥过程中WT中黄酮苷(FGs)的转化机理及其对味道的影响。在三个干燥温度下,WT中存在45个差异FG。与48h的枯萎样品相比,在三个干燥温度下,总FGs含量呈下降趋势,槲皮素-3-O-半乳糖苷和山奈酚-3-O-葡萄糖苷显示出最大的降解。这些结果通过FGs标准的模拟干燥反应得到证实。在80和100°C下干燥有助于类黄酮-C-糖苷的形成,但只观察到痕量的这些化合物。此外,使用超过阈值的剂量值选择了9个关键味觉FGs.这些FGs调节WT的味道,主要通过氢键与味觉受体结合,疏水和静电相互作用。最后,发现在60°C下干燥的WT的味道可接受性最高,因为这种方法可以适当地减少FGs的含量,削弱苦涩和涩,并保留甜味和鲜味。这项研究首次揭示了干燥温度对感官活性FGs转化机理的影响,为WT独特风味形成机理的分析和工艺优化提供了新的视角。
    Drying is an important stage used to improve the quality of white tea (WT). However, the effect of the drying temperature on the key taste compounds in WT remains unclear. In this study, targeted metabolomics, molecular docking, and a simulated reaction were used to investigate the transformation mechanism of flavonoid glycosides (FGs) in WT during drying at 60, 80, and 100 °C and its impact on taste. There were 45 differential FGs in WT at three drying temperatures. Compared with the withering samples for 48 h, the total FGs contents at three drying temperatures showed a decreasing trend, with quercetin-3-O-galactoside and kaempferol-3-O-glucoside showing the most degradation. These results were confirmed via a simulated drying reaction of FGs standards. Drying at 80 and 100 °C contributed to the formation of flavonoid-C-glycosides, but only trace amounts of these compounds were observed. In addition, nine key taste FGs were selected using dose-over-threshold values. These FGs regulated the taste of WT, mainly by binding to taste receptors via hydrogen bond, hydrophobic and electrostatic interactions. Finally, the taste acceptability of WT dried at 60 °C was found to be the highest, as this method could properly reduce the contents of FGs, weaken the bitterness and astringency, and retain the sweet and umami taste. This study revealed for the first time the transformation mechanism of sensory-active FGs affected by drying temperature, which provides a novel perspective for the analysis of the formation mechanism of the unique flavor of WT and the optimization of this process.
    导出

    更多引用

    收藏

    翻译标题摘要

    我要上传

    求助全文

  • 文章类型: Journal Article
    在越南,黑桃属植物Paramignyatrimera的茎和根(Oliv。)Burkill(在当地被称为“Xáotamphn”)被广泛用于治疗病毒性肝炎以及急性和慢性肝硬化等肝脏疾病。为了根据分子对接筛选寻找能够抑制冠状病毒的越南天然化合物,两种新的二聚香豆素糖苷,即顺式-顺式-顺式-顺式-顺式-顺式-顺式-顺式-顺式-顺式-顺式和两种先前确定的香豆素,反式异构体顺二聚肽B(3)和顺二聚肽A(4),从P.trimera的根分离并在体外测试其抗ACE-2抑制性质。发现ACE-2酶被顺式-副分子蛋白B(1)抑制,顺式-paratrimerinA(2),和反式-paratrimerinB(3),IC50值为28.9、68和77μM,分别。对接模拟显示,四种双香豆素糖苷具有良好的结合能(ΔG值范围为-10.6至-14.7kcal/mol),并且大部分与ACE-2蛋白的S1'亚位点结合。这些天然配体的关键相互作用包括与锌离子的金属螯合以及与Ser128,Glu145,His345,Lys363,Thr371,Glu406和Tyr803的多个H键。我们的发现表明,来自三聚体根的双香豆素糖苷以顺式和反式非对映体形式天然存在。双香豆素糖苷Lys363、Thr371、Glu406和Tyr803。我们的发现表明,来自P.trimera根的双香豆素糖苷具有作为预防SARS-CoV-2感染的天然ACE-2抑制剂的进一步研究潜力。
    In Vietnam, the stems and roots of the Rutaceous plant Paramignya trimera (Oliv.) Burkill (known locally as \"Xáo tam phân\") are widely used to treat liver diseases such as viral hepatitis and acute and chronic cirrhosis. In an effort to search for Vietnamese natural compounds capable of inhibiting coronavirus based on molecular docking screening, two new dimeric coumarin glycosides, namely cis-paratrimerin B (1) and cis-paratrimerin A (2), and two previously identified coumarins, the trans-isomers paratrimerin B (3) and paratrimerin A (4), were isolated from the roots of P. trimera and tested for their anti-angiotensin-converting enzyme 2 (ACE-2) inhibitory properties in vitro. It was discovered that ACE-2 enzyme was inhibited by cis-paratrimerin B (1), cis-paratrimerin A (2), and trans-paratrimerin B (3), with IC50 values of 28.9, 68, and 77 µM, respectively. Docking simulations revealed that four biscoumarin glycosides had good binding energies (∆G values ranging from -10.6 to -14.7 kcal/mol) and mostly bound to the S1\' subsite of the ACE-2 protein. The key interactions of these natural ligands include metal chelation with zinc ions and multiple H-bonds with Ser128, Glu145, His345, Lys363, Thr371, Glu406, and Tyr803. Our findings demonstrated that biscoumarin glycosides from P. trimera roots occur naturally in both cis- and trans-diastereomeric forms. The biscoumarin glycosides Lys363, Thr371, Glu406, and Tyr803. Our findings demonstrated that biscoumarin glycosides from P. trimera roots hold potential for further studies as natural ACE-2 inhibitors for preventing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.
    导出

    更多引用

    收藏

    翻译标题摘要

    我要上传

    求助全文

  • 文章类型: Journal Article
    建立了一种简单、灵敏的LC-串联质谱法测定大鼠血浆中沙己苷的方法,并进行了验证。用乙腈沉淀法制备蛋白沉淀后,使用在水中含有0.1%甲酸和0.1%甲酸的乙腈作为流动相,通过梯度洗脱在WatersHSST3柱上分离Schaftoside和内标物。该方法在0.5-500ng/mL范围内显示出良好的线性,具有可接受的日内和日间精密度,准确度,基体效应,和恢复。稳定性试验表明沙夫糖苷在样品采集期间是稳定的,准备,和存储。该方法用于大鼠沙己苷的药代动力学研究。结果表明,以1mg/kg的剂量静脉给药后,Schaftoside迅速从血浆中消除,消除半衰期为0.58h。口服剂量为5、10和20mg/kg后,Schaftoside迅速吸收到血浆中,并在0.67-1.17h达到45.1-104.99ng/mL的峰值浓度(Cmax)。暴露量(曲线下面积)的增加与剂量的增加呈线性关系。在5-20mg/kg的范围内,口服生物利用度为0.42%-0.71%。
    A simple and sensitive LC-tandem mass spectrometry method was established and validated for the determination of schaftoside in rat plasma. After prepared by protein precipitation with acetonitrile, schaftoside and internal standard were separated on a Waters HSS T3 column using acetonitrile containing 0.1% formic acid and 0.1% formic acid in water as the mobile phase by gradient elution. The method showed excellent linearity over the range of 0.5-500 ng/mL with acceptable intra- and inter-day precision, accuracy, matrix effect, and recovery. The stability assay indicated that schaftoside was stable during the sample acquisition, preparation, and storage. The method was applied to a pharmacokinetic study of schaftoside in rats. The result suggested that after intravenous administration at a dose of 1 mg/kg, schaftoside was quickly eliminated from the plasma with an elimination half-life of 0.58 h. After oral administration at doses of 5, 10, and 20 mg/kg, schaftoside was quickly absorbed into the plasma and reached the peak concentration (Cmax) of 45.1-104.99 ng/mL at 0.67-1.17 h. The increase of exposure (area under the curve) was linear with the increase of dose. The oral bioavailability was 0.42%-0.71% in the range of 5-20 mg/kg.
    导出

    更多引用

    收藏

    翻译标题摘要

    我要上传

    求助全文

  • 文章类型: Journal Article
    胸腺嘧啶DNA糖基化酶(TDG)介导的5-甲酰胞嘧啶和5-羧基胞嘧啶(5-caC)的切除是活性DNA去甲基化的关键步骤。在这里,我们采用组合的量子力学/分子力学方法来研究TDG催化的5-caC的N-糖苷键断裂的反应机理。计算结果表明,TDG催化的5-caC切除遵循协同(SN2)机制,其中糖苷键解离与亲核试剂攻击耦合。5-caC阴离子的质子化有助于N-糖苷键的裂解,其中N3-质子化的两性离子和亚氨基互变异构体比羧基-质子化的氨基互变异构体更有利。这与实验数据一致。此外,我们的结果表明,质子化的5-caC的构型重排过程会降低N-糖苷键的稳定性,并大大降低随后的C1\'-N1键裂解的势垒高度。这应该归因于结构重排导致的离开碱和负磷酸基团之间较小的静电排斥。
    Thymine DNA glycosylase (TDG)-mediated excision of 5-formylcytosine and 5-carboxylcytosine (5-caC) is a critical step in active DNA demethylation. Herein, we employed a combined quantum mechanics/molecular mechanics approach to investigate the reaction mechanism of TDG-catalyzed N-glycosidic bond cleavage of 5-caC. The calculated results show that TDG-catalyzed 5-caC excision follows a concerted (SN2) mechanism in which glycosidic bond dissociation is coupled with nucleophile attack. Protonation of the 5-caC anion contributes to the cleavage of the N-glycoside bond, in which the N3-protonated zwitterion and imino tautomers are more favorable than carboxyl-protonated amino tautomers. This is consistent with the experimental data. Furthermore, our results reveal that the configuration rearrangement process of the protonated 5-caC would lower the stability of the N-glycoside bond and substantially reduce the barrier height for the subsequent C1\'-N1 bond cleavage. This should be attributed to the smaller electrostatic repulsion between the leaving base and the negative phosphate group as a result of the structural rearrangement.
    导出

    更多引用

    收藏

    翻译标题摘要

    我要上传

    求助全文

  • 文章类型: Letter
    暂无摘要。
    导出

    更多引用

    收藏

    翻译标题摘要

    我要上传

    求助全文

公众号