小分子靶标的核酸适配体筛选的研究进展

核酸适配体(aptamer)是通过指数富集配体系统进化(SELEX)技术筛选得到的核糖核酸(RNA)或单链脱氧核糖核酸(ssDNA)。核酸适配体通过高亲和力特异性地识别小分子、蛋白质、细胞、微生物等多种靶标,在生物、医药、食品和环境检测等领域的应用日渐增多。但目前实际可用的核酸适配体有限,其筛选过程复杂,筛选难度大,制约了其应用。与生物大分子、细胞和微生物等靶标不同,小分子靶标与核酸分子的结合位点少、亲和力弱,且靶标通常需要固定在载体上。此外,小分子靶标结合核酸形成的复合物与核酸自身的大小、质量、电荷性质等方面差异较小,二者的分离难度大。故小分子靶标的核酸适配体筛选过程与大分子和细胞等复合靶标相比有明显差异,筛选难度更大。因此需要根据其自身结构特点和核酸适配体的应用目的选定靶标或核酸库的固定方法,优化靶标核酸复合物的分离方法。本文介绍了不同类型小分子(具有基团差异的单分子、含相同基团分子和手性分子等)靶标的选择及其核酸适配体的筛选方法,并对核酸库的设计、与靶标结合的核酸的分离方法和亲和作用表征方法进行了介绍,列出了自2008年以来报道的40余种小分子靶标的核酸适配体序列和复合物的平衡解离常数(K_d)。     

Matrix pre-coated MALDI MS targets for small molecule imaging in tissues

A new sample preparation method for MALDI tissue imaging has been developed for the analysis of low molecular weight compounds that employs matrix pre-coated MALDI targets. Tissue sections need only to be transferred onto the pre-coated target before analysis for fast and easy sample preparation. Pre-coated targets have a homogenous matrix coating with uniform crystals of approximately 1–2 μm and do not require solvents that may lead to analyte delocalization within a tissue section. We report here the use of matrix pre-coated targets for imaging of lipids, peptides, and pharmaceuticals in tissues.     

Programmable self-assembly of antibody-oligonucleotide conjugates as small molecule and protein carriers

Dihydrofolate reductase single-chain variable fragment (scFv) fusion proteins can be used for the targeted cellular delivery of oligonucleotides, conjugated small molecules, and proteins via labeling of oligonucleotides by bis-methotrexate.     

Quorum-sensing systems in staphylococci as therapeutic targets

The staphylococci are an ever-present threat in our world, capable of causing a wide range of infections, and are a persistent presence in the clinical environment. As the number of antimicrobial compounds effective against staphylococci decreases, because of the acquisition and spread of antibiotic resistance, there is a growing need for novel therapeutic molecules. Intra and inter-species communication (quorum sensing) is a biologically significant phenomenon that has been associated with virulence, intracellular survival, and biofilm formation. Quorum sensing molecules of staphylococci and other species (e.g. Pseudomonas aeruginosa) can inhibit virulence factor production and/or growth of staphylococci, leading to the possibility that interference with staphylococcal quorum-sensing systems could be a way of controlling the diverse infections caused by the staphylococci. In this article, we discuss the potential of quorum-sensing systems of staphylococci as therapeutic targets.     

A three-hybrid approach to scanning the proteome for targets of small molecule kinase inhibitors

In this study, we explored the application of a yeast three-hybrid (Y3H)-based compound/protein display system to scanning the proteome for targets of kinase inhibitors. Various known cyclin-dependent kinase (CDK) inhibitors, including purine and indenopyrazole analogs, were displayed in the form of methotrexate-based hybrid ligands and deployed in cDNA library or yeast cell array-based screening formats. For all inhibitors, known cell cycle CDKs as well as novel candidate CDK-like and/or CDK-unrelated kinase targets could be identified, many of which were independently confirmed using secondary enzyme assays and affinity chromatography. The Y3H system described here may prove generally useful in the discovery of candidate drug targets.     

Switching heterotrimeric G protein subunits with a chemical dimerizer

The selective manipulation of single intracellular-signaling events remains one of the key tasks when studying signaling networks. Here, we demonstrate for the first time the stimulation of FKBP fusions of various subunits of heterotrimeric G proteins by the simple addition of the chemical dimerizer rapamycin. Activation of constitutively active Gα(q), but not its GDP-bound form, leads to sustained oscillations of intracellular calcium and myo-inositol 1,4,5-trisphosphate (InsP(3)) levels in HEK cells, independent of the activation of endogenous Gα(q), in full agreement with the InsP(3)-Ca(2+) cross-coupling model of calcium oscillations. Rapamycin-induced translocation of wild-type Gα(s) to the plasma membrane results in elevated cAMP levels. Activation of rapamycin-inducible Gα(s) or Gβ(1)γ(2) evokes extensive modulation of ATP-induced calcium transients. The results demonstrate that inducible heterotrimeric G protein subunits will provide ways for dissecting G protein-coupled receptor signaling.     

Inhibitory G proteins and their receptors: emerging therapeutic targets for obesity and diabetes

The worldwide prevalence of obesity is steadily increasing, nearly doubling between 1980 and 2008. Obesity is often associated with insulin resistance, a major risk factor for type 2 diabetes mellitus (T2DM): a costly chronic disease and serious public health problem. The underlying cause of T2DM is a failure of the beta cells of the pancreas to continue to produce enough insulin to counteract insulin resistance. Most current T2DM therapeutics do not prevent continued loss of insulin secretion capacity, and those that do have the potential to preserve beta cell mass and function are not effective in all patients. Therefore, developing new methods for preventing and treating obesity and T2DM is very timely and of great significance. There is now considerable literature demonstrating a link between inhibitory guanine nucleotide-binding protein (G protein) and G protein-coupled receptor (GPCR) signaling in insulin-responsive tissues and the pathogenesis of obesity and T2DM. These studies are suggesting new and emerging therapeutic targets for these conditions. In this review, we will discuss inhibitory G proteins and GPCRs that have primary actions in the beta cell and other peripheral sites as therapeutic targets for obesity and T2DM, improving satiety, insulin resistance and/or beta cell biology.     

Radiolabeled small molecule protein kinase inhibitors for imaging with PET or SPECT

Imaging protein kinase expression with radiolabeled small molecule inhibitors has been actively pursued to monitor the clinical potential of targeted therapeutics and treatments as well as to determine kinase receptor density changes related to disease progression. The goal of the present review is to provide an overview of the breadth of radiolabeled small molecules that have been synthesized to target intracellular protein kinases, not only for imaging in oncology, but also for other areas of interest, particularly the central nervous system. Considerable radiotracer development has focused on imaging receptor tyrosine kinases of growth factors, protein kinases A, B and C, and glycogen synthase kinase-3?. Design considerations, structural attributes and relevant biological results are summarized.     

Terminal protection of small molecule-linked ssDNA-SWNT nanoassembly for sensitive detection of small molecule and protein interaction

The interactions between small molecules and proteins constitute a critical regulatory mechanism in many fundamental biological processes.A novel biosensing strategy has been developed for sensitive and selective detection of small molecule and protein interaction on the basis of terminal protection of small molecule-linked ssDNA-SWNT nanoassembly.The developed strategy is demonstrated using folate and its binding protein folate receptor(FR) as a model case.The results reveal the developed technique displays superb resistance to non-specific binding,very low detection limit as low as subnanomolar,and a wide dynamic range from 100 pmol/L to 500 nmol/L of FR.Thus,it may offer a simple,cost-effective,highly selective and sensitive platform for homogeneous fluorescence detection of small molecule-protein interaction and related biochemical studies.     

Bacterial beta-ketoacyl-acyl carrier protein synthases as targets for antibacterial agents

As a result of increasing drug resistance in pathogenic bacteria, there is a critical need for novel broad-spectrum antibacterial agents. As fatty acid synthesis (FAS) in bacteria is an essential process for cell survival, the enzymes involved in the FAS pathway have emerged as promising targets for antimicrobial agents. Several lines of evidence have indicated that bacterial condensing enzymes are central to the initiation and elongation steps in bacterial fatty acid synthesis and play a pivotal role in the regulation of the entire fatty acid synthesis pathway. beta-ketoacyl-acyl carrier protein (ACP) synthases (KAS) from various bacterial species have been cloned, expressed and purified in large quantities for detailed enzymological, structural and screening studies. Availability of purified KAS from a variety of bacteria, along with a combination of techniques, including combinatorial chemistry, high-throughput screening, and rational drug design based on crystal structures, will undoubtedly aid in the discovery and development of much needed potent and broad-spectrum antibacterial agents. In this review we summarize the biochemical, biophysical and inhibition properties of beta-ketoacyl-ACP synthases from a variety of bacterial species.     

A simple small molecule as the acceptor for fullerene-free organic solar cells

A simple small molecule named DICTiF was designed,synthesized and used as the acceptor for solution processed bulk-heterojunction solar cells with polymer PBDB-T as the donor.A power conversion efficiency of 7.11%was obtained.     

Dimeric aluminum-phosphorus compounds as masked frustrated Lewis pairs for small molecule activation

Hydroalumination of aryldialkynylphosphines RP(C≡C-(t)Bu)(2) (R = Ph, Mes) with equimolar quantities of diethylaluminum hydride afforded mixed alkenyl-alkynyl cyclic dimers in which the dative aluminum-phosphorus bonds are geminal to the exocyclic alkenyl groups. Addition of triethylaluminum to isolated 1 (R = Ph) or to the in situ generated species (R = Mes) caused diethylaluminum ethynide elimination to yield the arylethylphosphorus dimers 2 and 3. These possess a chair-like Al(2)C(2)P(2) heterocycle with intermolecular Al-P interactions. The boat conformation (4) was obtained by the reaction of (t)Bu-P(C≡C-(t)Bu)(2) with di(tert-butyl)aluminum hydride. Despite being dimeric, 2 behaves as a frustrated Lewis pair and activates small molecules. The reaction with carbon dioxide gave cis/trans isomeric AlPC(2)O heterocycles that differ only by the configuration of the exocyclic alkenyl unit. Four isomers resulted from the reaction with phenyl isocyanate. This is caused by cis/trans isomerization of the initial C=O adduct and subsequent rearrangement to the AlPC(2)N heterocycle, being the C=N adduct.     

Activators of cylindrical proteases as antimicrobials: identification and development of small molecule activators of ClpP protease

ClpP is a cylindrical serine protease whose ability to degrade proteins is regulated by the unfoldase ATP-dependent chaperones. ClpP on its own can only degrade small peptides. Here, we used ClpP as a target in a high-throughput screen for compounds, which activate the protease and allow it to degrade larger proteins, hence, abolishing the specificity arising from the ATP-dependent chaperones. Our screen resulted in five distinct compounds, which we designate as Activators of Self-Compartmentalizing Proteases 1 to 5 (ACP1 to 5). The compounds are found to stabilize the ClpP double-ring structure. The ACP1 chemical structure was considered to have drug-like characteristics and was further optimized to give analogs with bactericidal activity. Hence, the ACPs represent classes of compounds that can activate ClpP and that can be developed as potential novel antibiotics.     

小分子蛋白酪氨酸激酶抑制剂的合成研究进展

蛋白酪氨酸激酶在肿瘤的形成和增殖中起着关键作用,以蛋白酪氨酸激酶作为肿瘤治疗靶点的研究受到极大关注.本文作者综述了近十年来不同结构的酪氨酸激酶抑制剂的合成以及抗肿瘤活性的研究进展,以期为酪氨酸激酶抑制剂的研究与开发提供参考.     

Recent progress in exploiting small molecule peptides as supramolecular hydrogelators

Small molecule peptides and their derivatives are an emerging class of supramolecular hydrogelators that have attracted rapidly growing interest in the fields of drug delivery and regenerative medicine due to their inherent biodegradability and biocompatibility, as well as versatility in molecular design and ease of synthesis. Built upon the directional, intermolecular interactions such as hydrogen bonding and π-π stacking, peptide-based molecular units can associate in aqueous solution into filamentous assemblies of various sizes and shapes. Under appropriate conditions, these filamentous assemblies can percolate into a 3D network with materials properties tailorable for specific biomedical applications. In this review, we survey the literature published over the past three years in the development of peptide-based hydrogelators for biomedical applications. We highlight several representative examples and center our discussion on the fundamentals of molecular design, assembly, and gelation conditions.     

Cancer cell metabolism: implications for therapeutic targets

Cancer cell metabolism is characterized by an enhanced uptake and utilization of glucose, a phenomenon known as the Warburg effect. The persistent activation of aerobic glycolysis in cancer cells can be linked to activation of oncogenes or loss of tumor suppressors, thereby fundamentally advancing cancer progression. In this respect, inhibition of glycolytic capacity may contribute to an anticancer effect on malignant cells. Understanding the mechanisms of aerobic glycolysis may present a new basis for cancer treatment. Accordingly, interrupting lactate fermentation and/or other cancer-promoting metabolic sites may provide a promising strategy to halt tumor development. In this review, we will discuss dysregulated and reprogrammed cancer metabolism followed by clinical relevance of the metabolic enzymes, such as hexokinase, phosphofructokinase, pyruvate kinase M2, lactate dehydrogenase, pyruvate dehydrogenase kinase and glutaminase. The proper intervention of these metabolic sites may provide a therapeutic advantage that can help overcome resistance to chemotherapy or radiotherapy.