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https://www.readbyqxmd.com/read/28719188/phage-selection-of-cyclic-peptides-for-application-in-research-and-drug-development
#1
Kaycie Deyle, Xu-Dong Kong, Christian Heinis
Cyclic peptides can bind to protein targets with high affinities and selectivities, which makes them an attractive modality for the development of research reagents and therapeutics. Additional properties, including low inherent toxicity, efficient chemical synthesis, and facile modification with labels or immobilization reagents, increase their attractiveness. Cyclic peptide ligands against a wide range of protein targets have been isolated from natural sources such as bacteria, fungi, plants, and animals...
July 18, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28715095/a-self-sacrificing-n-methyltransferase-is-the-precursor-of-the-fungal-natural-product-omphalotin
#2
Sascha Ramm, Bartlomiej Krawczyk, Agnes Mühlenweg, Annette Poch, Eva Mösker, Roderich D Süssmuth
Research on ribosomally synthesized and posttranslationally modified peptides (RiPPs) has led to an increasing understanding of biosynthetic mechanisms, mostly drawn from bacterial examples. In contrast, reports on RiPPs from fungal producers, apart from the amanitins and phalloidins, are still scarce. The fungal cyclopeptide omphalotin A carries multiple N-methylations on the peptide backbone, a modification previously known only from nonribosomal peptides. Mining the genome of the omphalotin-producing fungus for a precursor peptide led to the identification of two biosynthesis genes, one encoding a methyltransferase OphMA that catalyzes the automethylation of its C-terminus, which is then released and cyclized by the protease OphP...
July 17, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28715083/macroevolution-a-new-method-for-the-rapid-generation-of-novel-scaffold-diverse-macrocyclic-libraries
#3
Kunz Oliver, Jörn Saupe, Haustedt Ole Lars, Sven Jakupovic, Christian Mang
Macrocycles are a structural class bearing great promise for future challenges in medicinal chemistry. Nevertheless there are few flexible approaches for the rapid generation of structurally diverse macrocyclic compound collections. We have developed an efficient method for the generation of novel macrocyclic peptide-based scaffolds. The process, called MacroEvoLution is based on a cyclization screening approach which gives reliable access to novel macrocyclic architectures. Classification of building blocks into specific pools ensures that scaffolds with orthogonally addressable functionalities are generated which can easily be used for the generation of structurally diverse compound libraries...
July 17, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28704057/peptide-macrocyclization-assisted-by-traceless-turn-inducers-derived-from-ugi-peptide-ligation-with-cleavable-and-resin-linked-amines
#4
Alfredo R Puentes, Micjel C Morejón, Daniel G Rivera, Ludger A Wessjohann
A multicomponent approach enabling the installation of turn-inducing moieties that facilitate the macrocyclization of short and medium-size oligopeptides is described. The strategy comprises the Ugi ligation of peptide carboxylic acids and isocyanopeptides in the presence of aldehydes and acid or photolabile amines followed by cyclization and cleavage of the backbone N-substituents to render canonical cyclopeptides. Implementing the approach on solid phase with the use of Rink amide resins led to a new class of backbone amide linker strategy...
July 13, 2017: Organic Letters
https://www.readbyqxmd.com/read/28699792/novel-approaches-to-the-design-of-bioavailable-melanotropins
#5
Yang Zhou, Minying Cai
The melanocortin system is a primordial and critical system for survival, involved in a wide variety of physiological functions. It includes melanocortin receptors (MCRs) and melanotropin ligands (MCLs). MCRs are important drug targets that can regulate several key physiological processes. Extensive efforts have been made to develop peptide and peptidomimetics targeting melanocortin receptors including MC1R, MC3R, MC4R and MC5R. Most research is focused on developing potent and selective melanotropins. However, developing bioavailable melanotropins remains challenging...
July 12, 2017: Expert Opinion on Drug Discovery
https://www.readbyqxmd.com/read/28699496/up-scaling-strategies-to-improve-the-industrial-production-of-bacitracin-at-largescale
#6
Chandra Kant Sharma, Monika Sharma
Bacitracin was discovered and named after a 7 year old American girl, Margaret Tracey in 1943 as Bacillus was isolated from her wounds. Bacillus licheniformis is usually present in soil and bird feathers. This bacterium is most commonly present around back plumage and chest of birds. There are different types of bacitracin but the one most potent is Bacitracin A. Bacitracin induced proteins are localized in bacterial membrane. Production of antibiotic initially stopped, resumed by induction of bacitracin induced protein but after few mitotic divisions microbes reverted to their vulnerable state...
July 11, 2017: Mini Reviews in Medicinal Chemistry
https://www.readbyqxmd.com/read/28691252/peptide-backbone-circularization-enhances-antifreeze-protein-thermostability
#7
Corey A Stevens, Joanna Semrau, Dragos Chiriac, Morgan Litschko, Robert L Campbell, David N Langelaan, Steven P Smith, Peter L Davies, John S Allingham
Antifreeze proteins (AFPs) are a class of ice-binding proteins that promote survival of a variety of cold-adapted organisms by decreasing the freezing temperature of bodily fluids. A growing number of biomedical, agricultural and commercial products, such as organs, foods, and industrial fluids, have benefited from the ability of AFPs to control ice crystal growth and prevent ice recrystallization at subzero temperatures. One limitation of AFP use in these latter contexts is their tendency to denature and irreversibly lose activity at the elevated temperatures of certain industrial processing or large-scale AFP production...
July 10, 2017: Protein Science: a Publication of the Protein Society
https://www.readbyqxmd.com/read/28679557/identification-and-characterization-of-daurichromenic-acid-synthase-active-in-anti-hiv-biosynthesis
#8
Miu Iijima, Ryosuke Munakata, Hironobu Takahashi, Hiromichi Kenmoku, Ryuichi Nakagawa, Takeshi Kodama, Yoshinori Asakawa, Ikuro Abe, Kazufumi Yazaki, Fumiya Kurosaki, Futoshi Taura
Daurichromenic acid (DCA) synthase catalyzes the oxidative cyclization of grifolic acid to produce DCA, an anti-HIV meroterpenoid isolated from Rhododendron dauricum. We identified a novel cDNA encoding DCA synthase by transcriptome-based screening from young leaves of R. dauricum. The gene coded for a 533-amino acid polypeptide with moderate homologies to FAD oxidases from other plants. The primary structure contained an N-terminal signal peptide, and conserved amino acid residues to form bicovalent linkage to FAD isoalloxazine ring at His112 and Cys175...
July 5, 2017: Plant Physiology
https://www.readbyqxmd.com/read/28665757/functional-epitopes-for-anti-aquaporin-5-antibodies-in-sj%C3%A3-gren-syndrome
#9
J Alam, J H Koh, S-K Kwok, S-H Park, K Park, Y Choi
We recently reported the presence of anti-aquaporin 5 (AQP5) immunoglobulin G (IgG) in patients with primary Sjögren syndrome (SS) with a sensitivity of 0.73 and a specificity of 0.68. The aim of this study was to identify functional epitopes for the anti-AQP5 autoantibodies detected in control subjects and patients with SS. Recognition of epitopes by anti-AQP5 autoantibodies in sera ( n = 13 for control and n = 24 for SS) or purified IgG ( n = 1 for control and n = 3 for SS) was evaluated by indirect immunofluorescence (IIF) assay performed in the presence or absence of peptides corresponding to the second transmembrane helix and extracellular loops A, C, and E of AQP5...
June 1, 2017: Journal of Dental Research
https://www.readbyqxmd.com/read/28644007/cyclotides-as-tools-in-chemical-biology
#10
Simon J de Veer, Joachim Weidmann, David J Craik
Among the various molecules that plants produce for defense against pests and pathogens, cyclotides stand out as exceptionally stable and structurally unique. These ribosomally synthesized peptides are around 30 amino acids in size, and are stabilized by a head-to-tail cyclic peptide backbone and three disulfide bonds that form a cystine knot. They occur in certain plants of the Rubiaceae, Violaceae, Cucurbitaceae, Fabaceae, and Solanaceae families, with an individual plant producing up to hundreds of different cyclotides...
June 23, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28608830/a-simple-defined-medium-for-the-production-of-true-diketopiperazines-in-xylella-fastidiosa-and-their-identification-by-ultra-fast-liquid-chromatography-electrospray-ionization-ion-trap-mass-spectrometry
#11
Michelli Massaroli da Silva, Moacir Dos Santos Andrade, Anelize Bauermeister, Marcus Vinícius Merfa, Moacir Rossi Forim, João Batista Fernandes, Paulo Cezar Vieira, Maria Fátima das Graças Fernandes da Silva, Norberto Peporine Lopes, Marcos Antônio Machado, Alessandra Alves de Souza
Diketopiperazines can be generated by non-enzymatic cyclization of linear dipeptides at extreme temperature or pH, and the complex medium used to culture bacteria and fungi including phytone peptone and trypticase peptone, can also produce cyclic peptides by heat sterilization. As a result, it is not always clear if many diketopiperazines reported in the literature are artifacts formed by the different complex media used in microorganism growth. An ideal method for analysis of these compounds should identify whether they are either synthesized de novo from the products of primary metabolism and deliver true diketopiperazines...
June 13, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/28598597/azapeptide-synthesis-methods-for-expanding-side-chain-diversity-for-biomedical-applications
#12
Ramesh Chingle, Caroline Proulx, William D Lubell
Mimicry of bioactive conformations is critical for peptide-based medicinal chemistry because such peptidomimetics may augment stability, enhance affinity, and increase specificity. Azapeptides are peptidomimetics in which the α-carbon(s) of one or more amino acid residues are substituted by nitrogen. The resulting semicarbazide analogues have been shown to reinforce β-turn conformation through the combination of lone pair-lone pair repulsion of the adjacent hydrazine nitrogen and urea planarity. Substitution of a semicarbazide for an amino amide residue in a peptide may retain biological activity and add benefits such as improved metabolic stability...
June 9, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28578648/synthetic-peptide-drugs-for-targeting-skin-cancer-malignant-melanoma-and-melanotic-lesions
#13
Alex Eberle, Bhimsen Rout, Mei Bigliardi Qi, Paul L Bigliardi
Peptides play decisive roles in the skin, ranging from host defense responses to various forms of neuroendocrine regulation of cell and organelle function. Synthetic peptides conjugated to radionuclides or photosensitizers may serve to identify and treat skin tumors and their metastatic forms in other organs of the body. In the introductory part of his review, the role and interplay of the different peptides in the skin is briefly summarized, including their potential application for the management of frequently occurring skin cancers...
June 4, 2017: Current Medicinal Chemistry
https://www.readbyqxmd.com/read/28561582/interplay-of-stereochemistry-conformational-rigidity-and-ease-of-synthesis-for-13-membered-cyclic-peptidomimetics-containing-apc-residues
#14
Dongyue Xin, Andrew Jeffries, Kevin Burgess
As part of a program to design small molecules that bind proteins, we require cyclic peptides (or peptidomimetics) that are severely constrained such that they adopt one predominant conformation in solution. This paper describes syntheses of the 13-membered cyclic tetrapeptides 1 containing aminopyrrolidine carboxyl (APC) residues. A linear precursor was prepared and used to determine optimal conditions for cyclization of that substrate. A special linker was prepared to enable cyclization of similar linear peptidomimetics on a solid phase, and the solution-phase cyclization conditions were shown to be appropriate for this too...
May 31, 2017: ACS Combinatorial Science
https://www.readbyqxmd.com/read/28544675/cyclotides-overview-and-biotechnological-applications
#15
REVIEW
Andrew Gould, Julio A Camarero
Cyclotides are globular microproteins with a unique head-to-tail cyclized backbone, stabilized by three disulfide bonds forming a cystine knot. This unique circular backbone topology and knotted arrangement of three disulfide bonds makes them exceptionally stable to chemical, thermal, and biological degradation compared to other peptides of similar size. In addition, cyclotides have been shown to be highly tolerant to sequence variability, aside from the conserved residues forming the cystine knot. Cyclotides can also cross cellular membranes and are able to modulate intracellular protein-protein interactions, both in vitro and in vivo...
May 24, 2017: Chembiochem: a European Journal of Chemical Biology
https://www.readbyqxmd.com/read/28541045/orally-absorbed-cyclic-peptides
#16
Daniel S Nielsen, Nicholas E Shepherd, Weijun Xu, Andrew J Lucke, Martin J Stoermer, David P Fairlie
Peptides and proteins are not orally bioavailable in mammals, although a few peptides are intestinally absorbed in small amounts. Polypeptides are generally too large and polar to passively diffuse through lipid membranes, while most known active transport mechanisms facilitate cell uptake of only very small peptides. Systematic evaluations of peptides with molecular weights above 500 Da are needed to identify parameters that influence oral bioavailability. Here we describe 125 cyclic peptides containing four to thirty-seven amino acids that are orally absorbed by mammals...
May 25, 2017: Chemical Reviews
https://www.readbyqxmd.com/read/28538738/solid-phase-synthesis-cyclization-and-site-specific-functionalization-of-aziridine-containing-tetrapeptides
#17
Benjamin K W Chung, Christopher J White, Andrei K Yudin
Cyclic tetrapeptides comprise a potent and selective class of molecules with a wide range of biological activities, including the phytotoxic activity of tentoxin and the histone deacetylase (HDAC) inhibitory effects of chlamydocin. The incorporation of a functional aziridine group within cyclic peptides enables their conformational control and allows for late-stage and site-selective functionalization of these molecules, thereby creating the potential for covalent protein labeling. This protocol describes the solid-phase synthesis, cyclization, and site-specific structural modification of aziridine-containing tetrapeptides...
June 2017: Nature Protocols
https://www.readbyqxmd.com/read/28536266/two-proteins-for-the-price-of-one-structural-studies-of-the-dual-destiny-preproalbumin-with-sunflower-trypsin-inhibitor-1
#18
Bastian Franke, Amy M James, Mehdi Mobli, Michelle L Colgrave, Joshua S Mylne, K Johan Rosengren
Seed storage proteins are both an important source of nutrition for humans and essential for seedling establishment. Interestingly, unusual napin-type 2S seed storage albumin precursors in sunflower contain a sequence that is released as a macrocyclic peptide during post-translational processing. The mechanism by which such peptides emerge from linear precursors proteins has received increased attention, however the structural characterization of intact precursor proteins has been limited. Here we report the 3D NMR structure of the Helianthus annuus PreproAlbumin With Sunflower trypsin inhibitor-1 (PawS1), and provide new insights into the processing of this remarkable dual-destiny protein...
May 23, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/28534477/decoding-and-reprogramming-fungal-iterative-nonribosomal-peptide-synthetases
#19
Dayu Yu, Fuchao Xu, Shuwei Zhang, Jixun Zhan
Nonribosomal peptide synthetases (NRPSs) assemble a large group of structurally and functionally diverse natural products. While the iterative catalytic mechanism of bacterial NRPSs is known, it remains unclear how fungal NRPSs create products of desired length. Here we show that fungal iterative NRPSs adopt an alternate incorporation strategy. Beauvericin and bassianolide synthetases have the same C1-A1-T1-C2-A2-MT-T2a-T2b-C3 domain organization. During catalysis, C3 and C2 take turns to incorporate the two biosynthetic precursors into the growing depsipeptide chain that swings between T1 and T2a/T2b with C3 cyclizing the chain when it reaches the full length...
May 23, 2017: Nature Communications
https://www.readbyqxmd.com/read/28520410/proteolytically-stable-cyclic-decapeptide-for-breast-cancer-cell-targeting
#20
Yogita Raghuwanshi, Hashem Etayash, Rania Soudy, Igor Paiva, Afsaneh Lavasanifar, Kamaljit Kaur
Starting with a previously reported linear breast cancer targeting decapeptide WxEAAYQkFL, here we report the synthesis of a novel cyclic peptide analogue cyclic WXEAAYQkFL. The N- to C-terminus amide cyclized peptide with one d-amino acid (k) displayed higher uptake by breast cancer cells, with minimal uptake by the noncancerous cells compared to the linear peptide with two d-amino acids (x and k), and was stable toward proteolytic degradation. When immobilized on gold microcantilever surface, the cyclic peptide was able to capture breast cancer cells specifically and sense samples with ≥25 cancer cells/mL...
June 6, 2017: Journal of Medicinal Chemistry
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