Dithiolane quartets: thiol-mediated uptake enables cytosolic delivery in deep tissue

The cytosolic delivery of various substrates in 3D multicellular spheroids by thiol-mediated uptake is reported. This is important because most orthodox systems, including polycationic cell-penetrating peptides, fail to deliver efficiently into deep tissue. The grand principles of supramolecular chemistry, that is the pH dependence of dynamic covalent disulfide exchange with known thiols on the transferrin receptor, are proposed to account for transcytosis into deep tissue, while the known but elusive exchange cascades along the same or other partners assure cytosolic delivery in kinetic competition. For quantitative detection in the cytosol, the 2D chloroalkane penetration assay (CAPA) is translated to 3D deep tissue. The targeted delivery of quantum dots, otherwise already troublesome in 2D culture, and the controlled release of mechanophores are realized to exemplify the power of thiol-mediated uptake into spheroids. As transporters, dithiolane quartets on streptavidin templates are introduced as modular motifs. Built from two amino acids only, the varied stereochemistry and peptide sequence are shown to cover maximal functional space with minimal structural change, i.e., constitutional isomers. Reviving a classic in peptide chemistry, this templated assembly of β quartets promises to expand streptavidin biotechnology in new directions, while the discovery of general cytosolic delivery in deep tissue as an intrinsic advantage further enhances the significance and usefulness of thiol-mediated uptake.

Cytosolic delivery in multicellular 3D spheroids is shown to be an intrinsic advantage of thiol-mediated uptake, which is compatible with proteins and QDs, achieving targeting and controlled release.     

Model studies for the thiol-mediated methyl transfer to corrinoids

The thiol-dependent methylation of heptamethyl cob(II)yrinate 8r with methyl iodide and methyl tosylate was explored under a variety of conditions. The interaction of the heptamethyl cob(II)yrinate with a variety of thiols was monitored prior to the addition of the methylating agent, and the formation of the Co(I) complex was only apparent in the reaction with hexane thiol. Nevertheless, thiol-mediated methylation of the Co(II) complex 8r takes place with methyl iodide under most conditions. The Co-methylation with methyl tosylate showed a different reactivity, was inhibited by pyridine or N-methylimidazole, and was strongly dependent on the the acidity of the thiol used. Mechanistic aspects are discussed.     

A thiol-mediated active membrane transport of selenium by erythroid anion exchanger 1 protein

In this paper, we describe a thiol-mediated and energy-dependent membrane transport of selenium by erythroid anion exchanger 1 (AE1, also known as band 3 protein). The AE1 is the most abundant integral protein of red cell membranes and plays a critical role in the carbon dioxide transport system in which carbon dioxide is carried as bicarbonate in the plasma. This protein mediates the membrane transport of selenium, an essential antioxidant micronutrient, from red cells to the plasma in a manner that is distinct from the already known anion exchange mechanism. In this pathway, selenium bound to the cysteine 93 of the hemoglobin β chain (Hb-Cysβ93) is transported by the relay mechanism to the Cys317 of the amino-terminal cytoplasmic domain of the AE1 on the basis of the intrinsic interaction between the two proteins and is subsequently exported to the plasma via the Cys843 of the membrane-spanning domain. The selenium export did not occur in plain isotonic buffer solutions and required thiols, such as albumin, in the outer medium. Such a membrane transport mechanism would also participate in the export pathways of the nitric oxide vasodilator activity and other thiol-reactive substances bound to the Hb-Cysβ93 from red cells to the plasma and/or peripherals.     

Stereoselective formal synthesis of (+)-allokainic acid via thiol-mediated acyl radical cyclization

Stereoselective formal synthesis of (+)-allokainic acid was accomplished starting from L-glutamate by using a thiol-mediated acyl radical cyclization as a key step. The cyclization of a formylalkenoate proceeded in a highly diastereoselective manner to give trans-4,5-disubstituted pyrrolidin-3-one without the production of the cis-isomer. The pyrrolidinone was then converted into the established synthetic intermediate of (+)-allokainic acid via the iron-catalyzed coupling reaction with an isopropenyl Grignard reagent.     

O-GlcNAcase抑制剂

O-连接的N-乙酰葡糖胺糖基化修饰 (O-GlcNAcylation) 是一种存在于蛋白质Ser/Thr上的翻译后修饰。与磷酸化相似,它参与细胞内的信号传递,并与神经退行性疾病、Ⅱ型糖尿病、癌症等许多疾病的发病机理密切相关。O-连接的N-乙酰葡糖胺水解酶 (O-GlcNAcase, OGA) 是生物体内唯一水解蛋白质O-GlcNAc修饰的糖苷酶。因此,研究高效、专一的OGA小分子抑制剂是调节细胞中蛋白质O-GlcNAc水平的有效策略,利于阿尔茨海默病等相关神经退行性疾病新型药物的开发。结合本实验室对OGA抑制剂的研究,本文介绍了OGA的结构、催化机理及目前OGA抑制剂的研究进展,讨论了各种抑制剂的构效关系,并对OGA抑制剂的研究前景进行了展望。     

尿激酶(uPA)化学合成抑制剂

胞外蛋白的水解是恶性肿瘤细胞侵袭和转移的必要条件,各种蛋白酶的水解反应降解细胞外基质,破坏细胞/细胞间的联系以适应细胞的迁移。尿激酶型纤溶酶原激活物(尿激酶,urokinase-type plasminogen activator, uPA)激活不具有丝氨酸蛋白酶活性的纤溶酶原为活性纤溶酶,在保持血流畅通与防止血栓的形成中具有重要的作用。此外,活性尿激酶降解细胞外基质,激活多种基质金属蛋白酶,以适应肿瘤细胞的侵袭、扩散和转移。抑制尿激酶的活性被公认为是抑制癌症转移的有效方法,其中合成小分子uPA抑制剂成为抗癌治疗中的新理念。本文综述了合成uPA抑制剂的研究现状。     

肿瘤血管生成抑制剂*

肿瘤血管生成的药物治疗是当前有关肿瘤的热点研究领域,目前已经有数种肿瘤血管生成抑制剂上市。肿瘤血管生成抑制剂能够抑制肿瘤的生长和转移,甚至使肿瘤消退。此类药物的研究开发可为肿瘤患者提供高效、低毒,并且抗瘤谱更广的药物。本文综述了近年来血管生成抑制剂的研究进展。首先介绍了间接血管生成抑制剂,此类药物中的血管内皮细胞生长因子受体信号通路的药物是目前最成功的一类血管生成抑制剂。其次介绍了直接血管生成抑制剂,使用这类药物更有可能避免间接抑制剂所引起的血管生成援救反应。然后在其他途径肿瘤血管生成抑制剂部分,本文详细介绍了作用机制尚不明确的沙利度胺及其衍生物。最后,本文分析讨论了这类药物的开发所遇到的一些问题,如抗血管生成治疗的新理论的挑战和耐药性等,并指出了未来发展方向。     

嘧啶类酪氨酸激酶抑制剂

酪氨酸激酶在肿瘤的发生、发展过程中起着非常重要的作用,已成为肿瘤治疗的新靶点.嘧啶类化合物是蛋白酪氨酸酶抑制剂(PTKIs)中的一大类,这类化合物在临床前期研究中显示具有很好的抗肿瘤效应,一些已在临床上作为很有前景的抗癌药.本文按其结构类别介绍了近年来报道的嘧啶类酪氨酸激酶抑制剂.     

Inhibitors of Bacterial Swarming Behavior

Bacteria can migrate in groups of flagella-driven cells over semisolid surfaces. This coordinated form of motility is called swarming behavior. Swarming is associated with enhanced virulence and antibiotic resistance of various human pathogens and may be considered as favorable adaptation to the diverse challenges that microbes face in rapidly changing environments. Consequently, the differentiation of motile swarmer cells is tightly regulated and involves multi-layered signaling networks. Controlling swarming behavior is of major interest for the development of novel anti-infective strategies. In addition, compounds that block swarming represent important tools for more detailed insights into the molecular mechanisms of the coordination of bacterial population behavior. Over the past decades, there has been major progress in the discovery of small-molecule modulators and mechanisms that allow selective inhibition of swarming behavior. Herein, an overview of the achievements in the field and future directions and challenges will be presented.     

磺酰脲类乙酰羟基酸合成酶抑制剂Topomer CoMFA研究

磺酰脲类除草剂是一类高选择性、广谱、低毒的化合物,在世界范围内得到了广泛的应用。本文采用易位体-比较分子力场法（Topomer CoMFA）对75个磺酰脲类化合物与植物源野生型拟南芥AHAS酶的离体相互作用进行了三维定量构效关系研究,快速准确地构建了Topomer CoMFA模型,该模型具有较强的预测能力（交叉验证相关系数q2为0.890,非交叉验证相关系数r2为0.967）。此模型对测试集的10个化合物的pKi值进行预测,其预测值与实际值一致。     

纺锤体驱动蛋白抑制剂*

对纺锤体驱动蛋白(kinesin spindle protein,KSP)进行抑制代表着一种新颖的抗肿瘤机制,能避免直接破坏微管的药物所具有的不可避免的神经毒性。自第一个选择性的小分子KSP抑制剂monastrol报道以来,已有多种类型的KSP抑制剂有了文献报道。本文介绍了近年来KSP抑制剂的结构和功能,以及作为一个新颖的靶点在抗肿瘤药物研究中的作用;讨论了该类抑制剂的构效关系,并对该类抑制剂的研究前景进行了展望。