Pyridinium-functionalized metalloporphyrins as bifunctional catalysts for cycloaddition of epoxides and carbon dioxide

New pyridinium-functionalized metalloporphyrins MEtPpBr₄ (M = Zn²⁺, Co²⁺, Ni²⁺, Cu²⁺; EtPp = 5, 10, 15, 20-tetra(4-(3-(N-ethyl-4-pyridyl)pyrazolyl)phenyl)porphyrin) were synthesized as bifunctional catalysts for the cycloaddition reactions of epoxides and CO₂. The effects of catalyst loading, CO₂ pressure, reaction temperature and time on catalytic activity were investigated. ZnEtPpBr₄ ( 1 ) and CoEtPpBr₄ ( 2 ) exhibited efficient activities in the cycloaddition reactions of various epoxides with CO₂ as at 120 °C under 2 MPa of CO₂ pressure without solvent. Most of corresponding cyclic carbonates could be obtained in almost quantitative yields and > 99.9% selectivity with molar ratio of epoxide/catalyst 2222 after 8 hr of reaction.     

共振瑞利散射法对普萘洛尔特效适配体系的手性分析

本文提出了对于手性药物普萘洛尔手性识别和手性分析的新方法。 该方法引用基于氧化石墨烯的指数富集配体系统进化筛选技术(GO-SELEX),经过10轮优化筛选出对心血管药物普萘洛尔有高度亲和力的特效适配体。 然后通过共振瑞利散射光谱法(RRS)对反应体系进行特效性检测,实验表明S-普萘洛尔和R-普萘洛尔有迥然不同的光谱差异,S-普萘洛尔与特效适配体结合后的RRS显著增强,而R-普萘洛尔与适配体结合后的RRS几乎没有变化。 据此可以对心血管药物手性普萘洛尔进行有效的手性识别。 在考察反应体系和实验条件的基础上,可对S-普萘洛尔进行实验检测,同时对外消旋体中的R-普萘洛尔进行计算分析。 实验对S-普萘洛尔的线性范围为5~275 nmol/L,检测限为0.5 nmol/L。 方法应用于外消旋药片的分析检测,结果令人满意。 实验表明,RRS检测特效适配体结合的手性靶标体系会彰显不同的光谱差异,从而可对手性对映体进行手性识别,尤其是可利用其光谱差异实现同时测定的手性分析,方法可在特殊情形下不经分离而同时测定手性对映体,具有推广应用价值。     

基于单-和双-三唑衍生物的三个Cu（Ⅱ）和Cu（Ⅰ）多金属氧簇基配合物的水热合成及光催化性能

在水热条件下,利用多齿的单-和双-三唑衍生物,制备了3种基于多金属氧簇基（POM）的Cu（Ⅱ）和Cu（Ⅰ）杂化材料,即{[Cu（L¹）₂（Mo₄O₁₃）]·2H₂O}_n（1）,{[Cu_1.5（L²）（HL₂）（H₂O）（Mo₄O₁₃）]·2H₂O}_n（2）,{[Cu₂（L₃）_1.5（Mo₄O₁₃）]·H₂O}_n（3）（L₁=4-pyridine-2-1,2,4-triazole,HL₂=3-（4H-1,2,4-triazol-4-yl）benzoic acid,L₃=trans-4,4''-azo-1,2,4-triazole）。通过单晶X射线衍射、傅里叶变换红外光谱和粉末X射线衍射分析确定了它们的结构。在1中,Mo₄O₁₃^2-阴离子和Cu（Ⅱ）中心通过双齿L₁相互连接,最终形成了二维（2D）POMs基的Cu（Ⅱ）杂化金属-有机骨架。在2中,Mo₄O₁₃^2-阴离子和Cu（Ⅱ）中心通过桥接水原子（O18）,双齿HL₂和三齿L₂^-相互连接,最终形成了三维（3D）POMs基的Cu（Ⅱ）微孔金属-有机骨架。在3中,L₃配体桥接相邻的Cu（Ⅰ）中心和Mo₄O₁₃^2-阴离子,最终形成独特的双重穿插结构的3DPOMs基的Cu（Ⅰ）杂化配位框架。光催化实验研究表明,样品1~3对于不同有机染料罗丹明B（RhB）、亚甲基蓝（MB）和甲基橙（MO）都具有很好的光催化降解能力。     

黄芩素室温磷光传感器的构建及应用

黄芩素可通过电子转移效应猝灭聚乙烯亚胺(PEI)包覆的锰(Mn)掺杂硫化锌(Zn S)量子点(PEIMn/Zn S QDs)的室温磷光。基于上述原理,建立了一种简单、快速测定黄芩素含量的室温磷光检测方法,PEI-Mn/Zn S QDs以水相共沉淀法获得。结果表明:当pH=8.0,反应时间为10 min时,量子点的磷光猝灭程度与黄芩素浓度呈良好的线性关系,线性范围为0.07~0.60 mg·L~(-1),方法检出限为0.039 mg·L~(-1),相关系数(r)为0.997,相对标准偏差为4.1%,实际样品的检测回收率为96.0%~100.7%。所建立的方法可有效避免常见离子和氨基酸等的干扰,适用于黄芩饮片及血清中黄芩素含量的快速测定,有望应用于医药行业中黄芩素含量的测定分析,也为其他药物基于量子点电子转移机制的检测提供了技术依据。     

不同结构扩孔分子筛催化MTP反应行为及表面积炭物种表征

采用TEAOH溶液处理MFI结构ZSM-5分子筛、MWW结构MCM-22分子筛,NaOH溶液处理TON结构ZSM-22分子筛、CHA结构SSZ-13分子筛得到四种结构的扩孔分子筛。在反应温度480℃、反应压力0.1 MPa、甲醇与水质量比1∶1、甲醇质量空速1.5 h~(-1)的条件下,考察了四种扩孔分子筛的甲醇制丙烯(MTP)催化性能,并采用XRD、N_2吸附-脱附、NH_3-TPD、TG、UV-Raman和GC-M S等方法表征催化剂的物化性质及M TP反应2 h后的分子筛积炭性质。结果表明,四种分子筛扩孔改性后均出现介孔,其中,T-ZSM-5分子筛在MTP反应中寿命最长;T-MCM-22分子筛寿命次之且失活速率慢;而一维孔道结构N-ZSM-22分子筛和八元环尺寸较小的N-SSZ-13分子筛均失活迅速。受拓扑结构和孔道扩散的影响,MTP反应2 h后,分子筛积炭量增加的顺序为T-ZSM-5N-ZSM-22T-MCM-22N-SSZ-13且可溶焦分子质量随积炭量增加而增重,即从五甲基苯增重到菲、芘等多环芳烃。     

The mechanism of the adsorption of dsDNA on citrate-stabilized gold nanoparticles and a colorimetric and visual method for detecting the V600E point mutation of the BRAF gene

A study is presented on the binding kinetics and mechanism of the adsorption of dsDNA on citrate-capped gold nanoparticles (AuNPs). Methods include fluorescence titration, isothermal calorimetry (ITC) titration, dynamic light scattering and gel electrophoresis. It is found that the fluorescence of probe DNA (labeled with Rhodamine Green and measured at excitation/emission peaks of 498/531 nm) is quenched by addition of AuNPs. The Stern-Volmer quenching constant (Ksv) is 1.67?×?10^{^}9 L·mol^?1 at 308 K and drops with increasing temperature. The quenching mechanism is mainly static. The results of both fluorescence titrations and ITC show negative values for ΔH and ΔS values. This shows ion-induced dipole-dipole interaction to be the main attractive forces between dsDNA and AuNPs, while electrostatic interactions result in repulsion. The repulsive forces lead to a lower affinity between dsDNA and AuNPs (compared to single-strand DNA). It is also found that dsDNA can prevent the aggregation of AuNPs which is accompanied by a color change from red into blue. The visual detection limit with bare eyes for dsDNA₁ is 36 pM. Based on these findings, a colorimetric method was developed to detect the proto-oncogene of serine/threonine-protein kinase B-Raf V600E point mutation in HT29, Ec109, A549, Huh-7 and SW480 cell lines.

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Graphical abstract Schematic of the salt-induced aggregation of uncapped gold nanoparticles (AuNPs) which leads to a color change from red to blue. If the AuNPs are coated with dsDNA, aggregation is suppressed.

     

Lymphatic targeting of hematoporphyrin monomethyl ether using poly (butyl-cyanoacrylate) based nanoparticle drug delivery system

The traditional treatment has inevitable drawbacks of nonspecific lymph targeting, poor therapeutic efficiency and residual metastatic for advanced cancer patients with lymph node metastases. To overcome these shortcomings, we prepare a nano-carrier drug delivery system. Photosensitizer hematoporphyrin monomethyl ether (HMME)-loaded poly (n-butylcyanoacrylate) nanoparticles (PBCA-NPs) was prepared successfully. The particle size was approximately 160 nm, the envelopment rate was 87.9%, and the drug loading rate was about 13.4%. The drug release study in vitro showed that the cumulative release rates of HMME-PBCA-NPs group was much less than free HMME group. The drug distribution in different tissues showed that the peak-reach time was 3 h in free HMME group and 6 h in nanoparticles group. All of these results confirmed the slow release characteristic of nanoparticles. In lymph node tissues, the HMME concentrations in HMME-PBCA-NPs group were much higher than those of the free HMME group at any time points we tested, in which the maximum difference concentration of HMME appeared at 6 h (1.2884?±?0.04695 vs. 0.0438?±?0.00558 µg/mg) after drug delivery. The mesenteric lymph nodes of rabbits were enlarged obviously in the NP group than in free HMME group at 6 h after drug delivery. All of these results confirmed the slow release characteristic and the lymphatic targeting characteristic of nanoparticles. In summary, we developed a lymphatic targeting nanoparticles drug delivery system successfully, which showed perfect lymph targeting and has the potential to be a new therapy strategy for advanced cancer patients with lymph node metastasis.     

Maximizing the Number of Interfacial Sites in Single‐Atom Catalysts for the Highly Selective,Solvent‐Free Oxidation of Primary Alcohols

The solvent‐free selective oxidation of alcohols to aldehydes with molecular oxygen is highly attractive yet challenging. Interfacial sites between a metal and an oxide support are crucial in determining the activity and selectivity of such heterogeneous catalysts. Herein, we demonstrate that the use of supported single‐atom catalysts (SACs) leads to high activity and selectivity in this reaction. The significantly increased number of interfacial sites, resulting from the presence of individually dispersed metal atoms on the support, renders SACs one or two orders of magnitude more active than the corresponding nanoparticle (NP) catalysts. Lattice oxygen atoms activated at interfacial sites were found to be more selective than O₂ activated on metal NPs in oxidizing the alcohol substrate. This work demonstrates for the first time that the number of interfacial sites is maximized in SACs, providing a new avenue for improving catalytic performance by developing appropriate SACs for alcohol oxidation and other reactions occurring at metal–support interfacial sites.