选择性识别平行性G-四联体的方酸类近红外荧光探针的研究

G-四联体是抗肿瘤药物筛选的一个重要靶点.开发针对某些拓扑结构的G-四联体荧光探针对于研究其结构和生物学功能具有十分重要的意义.设计、合成了四个方酸类花菁荧光染料即CSTS,CSBE,CSEM和CSBM,并检测了其对不同类型DNA的选择性识别作用.结果表明,所合成的四个化合物在缓冲溶液中几乎没有荧光发射,加入正平行G-四联体之后荧光增强大约1 000倍;而加入反平行G-四链体或单双链DNA荧光仅仅增强几十倍,说明其可以特异性识别平行G-四联体.但流式实验结果显示,CSTS不能透过细胞膜,同时存在高荧光背景的缺点,因此无法应用于活体分析.而另外三个不带阴离子侧链的衍生物则容易进入细胞,进入细胞的难易顺序为CSBECSEMCSBMCSTS.高选择性、低背景荧光和易进入细胞等优点使CSBE具有作为近红外荧光探针检测生物样品中正平行G-四联体的潜力.     

原癌基因c-myc G-四链体配体甲基蓝衍生物的设计、合成及其活性研究

采用计算机辅助药物设计方法,将以甲基蓝为先导化合物设计的配体分子与端粒DNA、原癌基因cmyc、c-kit2等形成的G-四链体三维结构进行分子对接模拟,发现目标化合物选择性靶向c-myc G-四链体,其对接分值为7.74。以吩噻嗪为起始原料合成出目标化合物,其结构经~1H-NMR、~(13)C-NMR和HRMS等确证。采用圆二色光谱实验测试了化合物与端粒、原癌基因c-myc和c-kit2等DNA的相互作用,结果表明目标化合物选择性诱导c-myc DNA形成G-四链体。     

用于监测G-四联体结构变化及K^＋定量检测的荧光探针研究

有望形成G-四联体的基因序列广泛分布于真核细胞基因组中的许多重要区域。考虑到某些基因的生理功能可能与其采取的G-四联体结构密切相关,因此发展一种G-四联体结构探针用以区分不同结构的G-四联体就显得尤为必要。结晶紫是一种三苯甲烷类染料,其自身的荧光强度很弱,但当其与G-四联体结合后荧光强度大幅提升。究其原因,除了G-四联体与结晶紫的结合作用限制了染料分子的自由运动,使分子的平面性增强以外,G-四联体的环部结构对结合在G-四联体末端的染料分子的保护作用也是一个重要因素。     

DNA G-四链体识别探针研究进展

G-四链体是一种由富含鸟嘌呤核酸序列形成的独特的二级结构,广泛分布于真核生物基因组,如端粒DNA、r DNA和一系列基因中的启动子区域。G-四链体结构对很多重要的生理过程如基因的转录、复制、重组以及保持染色体的稳定性方面具有重要作用。G-四链体的特异、高灵敏检测将为进一步了解G-四链体结构在人类细胞基因组中的分布、功能和机制奠定基础,也可能为靶向G-四链体的肿瘤治疗方法提供新的思路。因而过去几十年人们一直致力于开发设计具有高选择性和高灵敏度的G-四链体识别探针,这些探针已经广泛应用于溶液中G-四链体的识别,而且具有良好的选择性。目前也有少数探针能够直接用于检测活体G-四链体结构。本文综述了一些常见的靶向G-四链体的小分子配体,以及它们在染色体和活体细胞G-四链体检测中的应用。笔者希冀本文能为设计识别G-四链体的高性能探针,进一步实现活细胞内G-四链体的检测提供借鉴。     

G-四链体DNA稳定剂的研究进展

人体端粒由富含鸟嘌呤(G)的DNA重复序列组成,该序列在一定的条件下可以形成G-四链体DNA的结构.小分子化合物诱导该结构的形成并使之稳定,不但可以抑制端粒酶的活性或降低癌基因的转录表达而达到抗肿瘤的目的,还可以作为G-四链体DNA的探针,辅助G-四链体DNA生物功能的研究及与之相关疾病的诊断.因此,G-四链体DNA稳定剂的设计是近年来化学生物学的重要前沿领域之一.到目前为止,G-四链体DNA稳定剂主要可分为有机小分子化合物和金属配合物.本文重点综述这两方面特别是后者的最新研究进展.     

基于G-四联体的纳米探针比色检测铅离子

基于纳米探针和G-四联体建立了简便快速检测铅离子的方法. 纳米探针采用金纳米粒子自组装修饰富G寡核苷酸制得, 在铅离子存在下, 纳米探针上的富G寡核苷酸形成G-四联体, 导致纳米探针凝聚变色. 在优化条件下, 比色检测铅离子的线性范围为48~480 nmol/L, 检出限为20 nmol/L; 大多数金属离子无明显干扰, 而有明显干扰的汞离子可采用与之特异结合的寡核苷酸有效消除. 将该法成功用于环境水样中铅离子的检测, 重现性(RSD<3.0%)与回收率(98.4%~101.5%)良好.     

高选择性端粒G-四链体稳定性配体:9-O-多胺取代小檗碱衍生物的合成及活性评价

设计合成了3个多胺取代的小檗碱衍生物5a~5c, 并利用圆二色(CD)光谱、 荧光共振能量转移(FRET)熔点实验、 荧光光谱和聚合酶链反应(PCR)终止实验等手段研究了小檗碱衍生物5a~5c与端粒DNA的相互作用. 结果表明, 小檗碱衍生物5a~5c可以诱导端粒DNA序列形成反平行结构G-四链体, 显著地提高了端粒G-四链体的稳定性, 有效地抑制了端粒的扩增; 而与双链DNA的相互作用则很小, 是高选择性的端粒G-四链体配体.     

无标记筛选G-四链体小分子配体的荧光新方法

能够诱导端粒DNA(GDNA)形成G-四链体结构的小分子化合物具有重大的抗肿瘤意义。本文以天然抗肿瘤药物槲皮素为研究对象,基于N-甲基卟啉二丙酸Ⅸ(NMM)与G-四链体的特异性结合,以及配体加入NMM/GDNA体系前后荧光强度的变化,建立了一种简单快速、无需标记筛选G-四链体配体的新方法,并应用该方法考察了黄酮类化合物、生物碱类和有机酸类化合物对NMM/GDNA体系的影响。结果显示黄酮类化合物容易诱导端粒DNA形成G-四链体结构,而生物碱类和有机酸等比较困难。     

生物小分子巯基化合物荧光探针研究进展

细胞内的小分子巯基化合物在诸多生理过程中扮演重要角色.分子荧光探针具有灵敏度高、选择性好、生物相容性好、实时原位监测等优点.因此,构建可以选择性检测巯基化合物的荧光探针具有重要的生物学和医学意义.根据荧光探针与巯基化合物的反应类型总结了近几年来小分子巯基化合物荧光探针的设计策略和研究进展.     

靶向G-四链体的小分子配体在癌症治疗中应用的研究进展

G-四链体是一类由Hoogsteen氢键维持稳定的,富含鸟嘌呤的DNA或RNA二级结构。人类基因组中存在大量潜在的形成G-四链体的序列,所形成的G-四链体结构能够调控基因组的稳定性、DNA复制和基因表达,其中包括很多与癌症相关基因。因此寻找能够诱导DNA的G富集区域形成G-四链体结构的配体,进而筛选潜在抗癌药物的先导化合物,已成为癌症治疗研究的热点之一。本文对近年来发现和设计的以G-四链体为靶点的小分子配体,按照靶向的G-四链体结构类型和配体的分子结构进行分类,综述了这类化合物在癌症治疗方面的研究进展,分析了相关靶向治疗存在的问题,并对未来的研究方向进行了展望。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Copper catalyzed/mediated synthetic methodology for ebselen and related isoselenazolones

Scope of the copper catalyzed/mediated selenium-nitrogen coupling reaction has been studied for the synthesis of isoselenazolones. It is noticed that the 2-chloro, 2-bromo-, and 2-iodo-aryl amides substrates can be exploited in the selenium-nitrogen coupling reaction by employing 25-100 mol % of CuI/1,10-phenanthroline (L) and potassium carbonate as a base in DMF. Furthermore, electron rich 2-chloro-arylamides also underwent selenium-nitrogen coupling reaction to give biologically important selenium-nitrogen heterocycles. Also, copper-catalyzed selenium-nitrogen coupling reaction has been meticulously applied for the synthesis of diaryl diselenides having methoxy, amine, and amide functionality from respective aryl iodides in the presence of stoichiometric amount of succinimide as an external Se-N coupling partner.     

Knoevenagel condensation catalyzed by novel Nmm-based ionic liquids in water

A series of novel N-methyl morpholine (Nmm) based ionic liquids with 1,2-propanediol group were synthesized and used as catalysts for Knoevenagel condensation at room temperature in water. Under the effect of the catalyst, various aldehydes or aliphatic ketones could react with a wide range of activated methylene compounds well, including malononitrile, alkyl cyanoacetate, cyanoacetamide, β-diketone, barbituric acid, 2-arylacetonitrile and thiazolidinedione. Furthermore, most of the products could be separated just by filtrating and washing with water. Additionally, the catalyst is recyclable and applicable for the large-scale synthesis.     

Construction of polyheterocyclic spirotetrahydrothiophene derivatives via sulfa-Michael/aldol cascade reaction

A series of polyheterocyclic spirotetrahydrothiophene derivatives were obtained in moderate to excellent yields via a catalyst-free sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 under mild conditions. We also present the first asymmetric sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 with moderate to good enantioselectivities catalyzed by readily available chiral phase-transfer catalysts (PTCs).     

Suzuki-Miyaura reactions of the soluble guanylate cyclase inhibitor NS2028: a non-product specific route to C-8 substituted analogues

Both soluble guanylate cyclase (sGC) inhibitors ODQ 1 and NS2028 2 are synthesized via improved protocols. In the former case treating 3,4-dihydroquinoxalin-2(1H)-one oxime 8, which can be prepared in two steps from 1,2-benzenediamine, with 1,1′-carbonyldiimidazole (CDI) gives the dihydro-ODQ 10 that in the presence of KMnO₄ oxidises to give ODQ 1 in an overall yield of 46% starting from 1,2-benzenediamine. In the latter case, the synthesis affords NS2028 2 from 2-amino-4-bromophenol 3 in three steps with an overall yield of 85% and avoids the need for chromatography. Furthermore, Suzuki-Miyaura reaction conditions are described that enable the preparation of 8-aryl and 8-heteroaryl derivatives of NS2028 directly from NS2028 2. Finally, demethylation of the 8-(methoxyphenyl) substituted analogues afforded the 8-(hydroxyphenyl) derivatives 40-42. All new products are fully characterised.