Uril Research Articles

Molecular dynamics simulation study of the structural features and inclusion capacities of cucurbit[6]uril derivatives in aqueous solutions

Molecular dynamics (MD) simulations were performed for cucurbit[6]uril (CB6) methyl and cyclohexyl derivatives in aqueous solutions. Furthermore, MD simulations have been conducted to study the inclusion complexes between each CB6 derivative with α,ω-pentane diammonium ion (NH3+(CH2)5NH3+) to estimate the binding free energies, the complex geometries and the intermolecular forces responsible for complex formation. Results show a complete inclusion of the guest molecule in the cavity of the host for all complexes. Results also indicate that the guest dynamics inside the cavity of the substituted host is similar to that for the unsubstituted host. This demonstrates that the molecular recognition of the host is not affected by the alkyl substitution at the equator. Also, there is an insignificant conformational change of the macrocyclic structure upon inclusion of the guest. Molecular mechanics/Poisson Boltzmann surface area method was used to estimate the binding free energy of each complex. Results indicat...

Investigation of Excited-State Proton Transfer of 2-(3-Acetamido-2-pyridyl)benzimidazole in the Confined Nanocavity of Cucurbit[7]uril

以荧光发射光谱,1H NMR谱及量子化学计算研究了2-（3-乙酰胺基-2-吡啶基）苯并咪唑（2-3Am2PyBI）质子转移过程及其与七元瓜环超分子（CB7）的包合作用,考察了乙酰基取代基效应及CB7的包合作用对2-3Am2PyBI质子转移过程的影响.结果表明：乙酰基取代促进了质子转移过程;2-3Am2PyBI阳离子构型更易与CB7发生包合作用;在特定溶液pH值条件下,摩尔比法荧光光谱实验表明超分子包合作用抑制了2-3Am2PyBI的激发态质子转移过程;Benesi-Hildebrand方程拟合得到,超分子体系的包合比为1∶1;1H NMR测试进一步表明2-3Am2PyBI以苯环部分进入CB7的空腔,同时,以量化计算与荧光实验结合,从理论与实验方面共同验证了2-3Am2PyBI的质子转移异构体.

葫芦[8]脲的环套环分子组装

以4，4＇-联吡啶鎓、2，6-萘二酚和2，7-萘二酚为基本结构单元，设计合成了2种带有分子内给受体相互作用的大环化合物，并采用紫外光谱和核磁共振等手段研究了其与葫芦[8]脲的键合行为．研究结果表明，在水溶液中大环的2，6-萘二酚和2，7-萘二酚与4，4＇-联吡啶翁之间存在分子内的电荷转移相互作用，而葫芦[8]脲可以键合这2种大环化合物，导致电荷转移吸收峰增强并红移，表明葫芦[8]脲能增强这种分子内的电荷转移相互作用，形成稳定的环套环分子组装体．这种结构是基于葫芦[8]脲的新型拓扑结构．

Interaction of Cucurbit[n=7,8] uril with Ranitidine Hydrochloride and Slow Release Properties

Cucurbit[n]urils(Q[n]) has hydrophobic central cavity and negatively charged carbonyl portals,can bind to a variety of cationic organic guest molecules and neutral species with high affinity,and therefore show great promise as a drug delivery system.In this work,interaction of cucurbiturils with ranitidine hydrochloride(RH) which is a histamine H2 receptor antagonists were investigated by means of 1H NMR and UV-Vis spectroscopy,and the drug slow-release properties of inclusion complexes were observed in vitro.The effect of pH value on the interaction was studied;the inclusion ratio m,formation constant Ka and the drugs cumulative release of inclusion complexes in vitro were determined.The results reveal that RH form a 1∶ 1 complex with the Q[n](n=7,8).Formation constant of Ka was found to be 1.21×104 and 2.06×104 L/mol for Q[7]-RH and Q[8]-RH systems,respectively.RH can both form inclusion complexes with Q[7] and Q[8] in acidic,neutral conditions respectively,but they can't form inclusion complexes in alkaline conditions.The cumulative release rate in vitro of RH,Q[7]-RH and Q[8]-RH in artificial gastric juice(pH=1.2) at 60 min were 89.1%,56.6% and 38.4%,respectively;and in artificial intestinal fluid(pH=6.8) at 60 min were found to be 90.2%,58.7% and 38.0%,respectively.The drug release rates of Q[7]-RH and Q[8]-RH were obviously slower than that of RH.Q[7]-RH and Q[8]-RH had obviously sustained-release in vitro.

Preparation and Properties of Temperature and pH Sensitive Chitosan Supramolecular Gel Based on Host-guest Interaction of Cucurbit[8]uril

壳聚糖侧链改性合成N-（4-二甲氨基苯甲基）壳聚糖（MBCS）,通过葫芦[8]脲（Q[8]）与MBCS侧链之间的主客体作用制得Q[8]/MBCS超分子凝胶.利用红外光谱、紫外光谱、1H NMR、X-射线粉末衍射（XRD）、热重分析（TG）和差示扫描量热（DSC）等技术对改性壳聚糖及凝胶进行表征.以5-氟尿嘧啶（5-Fu）为模型药物,研究载药凝胶在不同pH环境下的释药行为.结果表明Q[8]/MBCS体系在酸性条件下,可组装形成超分子凝胶,该凝胶体系具有温敏性和pH敏感性.扫描电镜（SEM）图显示凝胶具有网状交联结构,1H NMR谱显示,在酸性条件下,Q[8]与MBCS含氮侧链基团间发生主客体包合作用是超分子凝胶形成的主要原因.Q[8]/MBCS载药凝胶在酸性介质中对药物具有明显的缓释作用.