keyword
MENU ▼
Read by QxMD icon Read
search

cyclization peptides

keyword
https://www.readbyqxmd.com/read/28444893/catalytic-reductive-synthesis-and-direct-derivatization-of-unprotected-aminoindoles-aminopyrroles-and-iminoindolines
#1
Leonardus H Leijendekker, Jens Weweler, Tobias M Leuther, Jan Streuff
A titanium(III)-catalyzed radical cyclization to unprotected 3-aminoindoles, 3-aminopyrroles, or 3-iminoindolines is reported. The reaction is non-hazardous, scalable, and allows facile isolation of the free products by extraction. The method is demonstrated on a large substrate scope and it further allows the direct installation of various nitrogen protecting groups or the synthesis of building blocks for peptide chemistry in a single sequence. Fused bisindoles can be directly accessed from the cyclization products...
April 26, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28428776/mapping-and-identification-of-antifungal-peptides-in-the-putative-antifungal-protein-afpb-from-the-filamentous-fungus-penicillium-digitatum
#2
Sandra Garrigues, Mónica Gandía, Attila Borics, Florentine Marx, Paloma Manzanares, Jose F Marcos
Antifungal proteins (AFPs) from Ascomycetes are small cysteine-rich proteins that are abundantly secreted and show antifungal activity against non-producer fungi. A gene coding for a class B AFP (AfpB) was previously identified in the genome of the plant pathogen Penicillium digitatum. However, previous attempts to detect the AfpB protein were not successful despite the high expression of the corresponding afpB gene. In this work, the structure of the putative AfpB was modeled. Based on this model, four synthetic cysteine-containing peptides, PAF109, PAF112, PAF118, and PAF119, were designed and their antimicrobial activity was tested and characterized...
2017: Frontiers in Microbiology
https://www.readbyqxmd.com/read/28406518/a-multicomponent-macrocyclization-strategy-to-natural-product-like-cyclic-lipopeptides-synthesis-and-anticancer-evaluation-of-surfactin-and-mycosubtilin-analogues
#3
Micjel C Morejón, Annegret Laub, Goran N Kaluđerović, Alfredo R Puentes, Ali N Hmedat, Anselmo J Otero-González, Daniel G Rivera, Ludger A Wessjohann
A multicomponent macrocyclization strategy towards cyclic lipopeptides is described. The approach relies on the utilization of the Ugi and Passerini multicomponent reactions for the cyclization of peptides and oxo-peptides, and here it is employed for the construction of a small library of analogues of the natural products mycosubtilin and surfactin A. A key feature of this method is the simultaneous incorporation of either one or two exocyclic lipid tails along with the macrocyclic ring closure, which is only possible due to the multicomponent nature of the macrocyclization step...
April 13, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28395122/cu-%C3%B0-mediated-denitrogenative-macrocyclization-for-the-synthesis-of-cyclic-%C3%AE-3%C3%AE-tetrapeptide-analogs
#4
Chun-Chi Chen, Sheng-Fu Wang, Yung-Yu Su, Yuya A Lin, Po-Chiao Lin
A copper(I)-mediated denitrogenative reaction has been successfully developed in the preparation of cyclic tetrapeptides. A key reactive intermediate, ketenimine, triggers the key intramolecular cyclization by the terminal amine group and therefore generates an internal β-amino acid with an amidine linkage. The chemistry developed here provides a new synthetic route for the preparation of cyclic α3β-tetrapeptide analogs which are rich in information to the conformational study of macrocycles as well as important biologically active peptides...
April 10, 2017: Chemistry, An Asian Journal
https://www.readbyqxmd.com/read/28387471/arrangement-of-proteinogenic-%C3%AE-amino-acids-on-a-cyclic-peptide-comprising-alternate-biphenyl-cored-%C3%AE-amino-acids
#5
Shohei Tashiro, Masayuki Chiba, Mitsuhiko Shionoya
Aiming at precisely arranging several proteinogenic α-amino acids on a folded scaffold, we have developed a cyclic hexapeptide comprising an alternate sequence of biphenyl-cored ζ-amino acids and proteinogenic α-amino acids such as l-leucine. The amino acids were connected by typical peptide synthesis, and the resultant linear hexapeptide was intramolecularly cyclized to form a target cyclic peptide. Theoretical analyses and NMR spectroscopy suggested that the cyclic peptide was folded into an unsymmetrical conformation, and the structure was likely to be flexible in CHCl3 ...
April 7, 2017: Chemistry, An Asian Journal
https://www.readbyqxmd.com/read/28382155/preclinical-melanoma-imaging-with-68-ga-labeled-%C3%AE-melanocyte-stimulating-hormone-derivatives-using-pet
#6
Chengcheng Zhang, Zhengxing Zhang, Kuo-Shyan Lin, Jinhe Pan, Iulia Dude, Navjit Hundal-Jabal, Nadine Colpo, François Bénard
It is estimated that melanoma accounted for 76,380 new cases and 10,130 deaths in the United States in 2016. The melanocortin 1 receptor (MC1R) is highly expressed in the vast majority of melanomas, which makes it an attractive target for molecular imaging and radionuclide therapy. Lactam bridge-cyclized α-melanocyte-stimulating hormone (Ac-Nle(4)-cyclo[Asp(5)-His-D-Phe(7)-Arg-Trp-Lys(10)]-NH2, or Nle-CycMSHhex) analogues have been successfully developed and studied for MC1R-targeted imaging, predominantly with single-photon emission computed tomography (SPECT)...
2017: Theranostics
https://www.readbyqxmd.com/read/28378889/the-prebiotic-c-terminal-elongation-of-peptides-can-be-initiated-by-n-carbamoyl-amino-acids
#7
Ninette Abou Mrad, Ghinwa Ajram, Jean-Christophe Rossi, Laurent Boiteau, Fabrice Duvernay, Robert Pascal, Gregoire Danger
The formation of peptides upon EDC promoted activation of N-carbamoylamino acids (CAA), was considered in the scope of our recent works on carbodiimide promoted C-terminus elongation of peptides in a prebiotic context. Thus EDC promoted activation of CAA derivatives of Tyr(Me) or Ala in dilute aqueous medium pH 5.5-6.5 in the presence of excess of AA, resulted in peptide formation via C-terminus activation / elongation. Kinetic results similar to those of EDC-mediated activation of N-acyl-AA lead us to postulate the formation of a 2-amino-5(4H)-oxazolone intermediate by cyclization of the activated CAA, in spite of the absence of epimerization occurred at CAA residues...
April 5, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28377579/vlp-based-vaccine-induces-immune-control-of-staphylococcus-aureus-virulence-regulation
#8
Seth M Daly, Jason A Joyner, Kathleen D Triplett, Bradley O Elmore, Srijana Pokhrel, Kathryn M Frietze, David S Peabody, Bryce Chackerian, Pamela R Hall
Staphylococcus aureus is the leading cause of skin and soft tissue infections (SSTIs) and mounting antibiotic resistance requires innovative treatment strategies. S. aureus uses secreted cyclic autoinducing peptides (AIPs) and the accessory gene regulator (agr) operon to coordinate expression of virulence factors required for invasive infection. Of the four agr alleles (agr types I-IV and corresponding AIPs1-4), agr type I isolates are most frequently associated with invasive infection. Cyclization via a thiolactone bond is essential for AIP function; therefore, recognition of the cyclic form of AIP1 may be necessary for antibody-mediated neutralization...
April 4, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28370688/impact-of-the-amino-acid-sequence-on-the-conformation-of-side-chain-lactam-bridged-octapeptides
#9
Saskia Neukirchen, Viktoria Krieger, Cornelia Roschger, Mario Schubert, Brigitta Elsässer, Chiara Cabrele
Synthetic helical peptides are valuable scaffolds for the development of modulators of protein-protein interactions involving helical motifs. Backbone-to-side chain or side chain-to-side chain constraints have been and still are intensively exploited to stabilize short α-helices. Very often, these constraints have been combined with backbone modifications induced by Cα-tetrasubstituted, β-, or γ-amino acids, which facilitate the α-peptide or α/β/γ-peptide adopting an α-helical conformation. In this work, we investigated the helical character of octapeptides that were cyclized by a Lys-Asp-(i,i + 4)-lactam bridge...
March 29, 2017: Journal of Peptide Science: An Official Publication of the European Peptide Society
https://www.readbyqxmd.com/read/28333237/new-paenibacillus-strain-produces-a-family-of-linear-and-cyclic-antimicrobial-lipopeptides-cyclization-is-not-essential-for-their-antimicrobial-activity
#10
En Huang, Xu Yang, Liwen Zhang, Sun Hee Moon, Ahmed E Yousef
A new bacterial isolate, Paenibacillus sp. OSY-N, showed potent antimicrobial activity against Gram-negative and Gram-positive bacteria. Antimicrobials produced by this strain were purified by reverse-phase high performance liquid chromatography (HPLC). Structural analysis, using mass spectrometry (MS), of a single active HPLC fraction revealed two known cyclic lipopeptides, BMY-28160 and permetin A, a new cyclic lipopeptide, and the linear counterparts of these cyclic compounds. The latter were designated as paenipeptin A, B and C, respectively...
February 25, 2017: FEMS Microbiology Letters
https://www.readbyqxmd.com/read/28326777/peptide-macrocyclization-inspired-by-non-ribosomal-imine-natural-products
#11
Lara R Malins, Justine N deGruyter, Kevin J Robbins, Paul M Scola, Martin D Eastgate, M Reza Ghadiri, Phil S Baran
A thermodynamic approach to peptide macrocyclization inspired by the cyclization of non-ribosomal peptide aldehydes is presented. The method provides access to structurally diverse macrocycles by exploiting the reactivity of transient macrocyclic peptide imines toward inter- and intramolecular nucleophiles. Reactions are performed in aqueous media, in the absence of side chain protecting groups, and are tolerant of all proteinogenic functional groups. Macrocyclic products bearing non-native and rigidifying structural motifs, isotopic labels, and a variety of bioorthogonal handles are prepared, along with analogues of four distinct natural products...
March 31, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28318942/cyclic-mu-opioid-receptor-ligands-containing-multiple-n-methylated-amino-acid-residues
#12
Anna Adamska-Bartłomiejczyk, Anna Janecka, Márton Richárd Szabó, Maria Camilla Cerlesi, Girolamo Calo, Alicja Kluczyk, Csaba Tömböly, Attila Borics
In this study we report the in vitro activities of four cyclic opioid peptides with various sequence length/macrocycle size and N-methylamino acid residue content. N-Methylated amino acids were incorporated and cyclization was employed to enhance conformational rigidity to various extent. The effect of such modifications on ligand structure and binding properties were studied. The pentapeptide containing one endocyclic and one exocyclic N-methylated amino acid displayed the highest affinity to the mu-opioid receptor...
March 7, 2017: Bioorganic & Medicinal Chemistry Letters
https://www.readbyqxmd.com/read/28302013/multicyclic-peptides-as-scaffolds-for-the-development-of-tumor-targeting-agents
#13
Anastasia Loktev, Uwe Haberkorn, Walter Mier
The lack of specificity of traditional cytotoxic drugs triggers the development of anticancer agents with high selectivity to tumor-specific proteins. The unveiling of target structures such as EGFR or Her2 allows the focused development of novel therapies and has strongly advanced tumor treatment. Tumor-specific high-affinity ligands can be identified by using display techniques such as phage, yeast surface, ribosome and mRNA display. These techniques enable the screening of huge libraries, consequently providing a valuable alternative to rational drug development...
March 16, 2017: Current Medicinal Chemistry
https://www.readbyqxmd.com/read/28298600/dengue-virus-ns2b-ns3-protease-inhibitors-exploiting-the-prime-side
#14
Kuan-Hung Lin, Akbar Ali, Linah Rusere, Djade I Soumana, Nese Kurt Yilmaz, Celia A Schiffer
The mosquito-transmitted dengue virus (DENV) infects millions of people in tropical and sub-tropical regions. Maturation of DENV particles requires proper cleavage of the viral polyprotein, including processing 8 of the 13 substrate cleavage sites by dengue NS2B-S3 protease. With no available direct-acting antiviral targeting DENV, NS2-S3 protease is a promising target for inhibitor design. Current design efforts focus on the nonprime side of the DENV protease active site, resulting in highly hydrophilic and nonspecific scaffolds...
March 15, 2017: Journal of Virology
https://www.readbyqxmd.com/read/28273421/a-mechanistic-model-for-the-aziridine-aldehyde-driven-macrocyclization-of-peptides
#15
Lee Belding, Serge Zaretsky, Andrei K Yudin, Travis Dudding
Aziridine aldehyde-driven macrocyclization of peptides is a powerful tool for the construction of biologically active macrocycles. While this process has been used to generate diverse collections of cyclic molecules, its mechanistic underpinnings have remained unclear. To enable progress in this area we have carried out a mechanistic study, which suggests that the cyclization owes its efficiency to a combination of electrostatic attraction between termini of a discrete nitrilium ion intermediate and intramolecular hydrogen bonding...
March 8, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28245769/macrocyclic-antimicrobial-peptides-engineered-from-%C3%AF-conotoxin
#16
Xinya Hemu, James Tam
The potent calcium channel blocker ω-conotoxin MVIIA is a linear cystine-knot peptide with multiple basic amino acids at both termini. This work shows that macrocyclization of MVIIA linking two positive-charge terminal clusters as a contiguous segment converts a conotoxin into an antimicrobial peptide. In addition, conversion of disulfide bonds to amino butyric acids improved the antimicrobial activity of the cyclic analogs. Ten macrocyclic analogs, with or without disulfide bonds, were prepared by both Boc and Fmoc chemistry using native chemical ligation...
October 27, 2016: Current Pharmaceutical Design
https://www.readbyqxmd.com/read/28240912/domain-targeted-metabolomics-delineates-the-heterocycle-assembly-steps-of-colibactin-biosynthesis
#17
Eric P Trautman, Alan R Healy, Emilee E Shine, Seth B Herzon, Jason M Crawford
Modular polyketide synthases (PKSs) and nonribosomal peptide synthetases (NRPSs) comprise giant multidomain enzymes responsible for the "assembly line" biosynthesis of many genetically encoded small molecules. Site-directed mutagenesis, protein biochemical, and structural studies have focused on elucidating the catalytic mechanisms of individual multidomain proteins and protein domains within these megasynthases. However, probing their functions at the cellular level typically has invoked the complete deletion (or overexpression) of multidomain-encoding genes or combinations of genes and comparing those mutants with a control pathway...
March 10, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28230996/a-facile-n-mercaptoethoxyglycinamide-mega-linker-approach-to-peptide-thioesterification-and-cyclization
#18
Patrick M M Shelton, Caroline E Weller, Champak Chatterjee
The C-terminal electrophilic activation of peptides by α-thioesterification requires strongly acidic conditions or complex chemical manipulations, which ultimately limit functional group compatibility and broad utility. Herein, we report a readily accessible N-mercaptoethoxyglycinamide (MEGA) solid-phase linker for the facile synthesis of latent peptide α-thioesters. Incubating peptide-MEGA sequences with 2-mercaptoethanesulfonic acid at mildly acidic pH yielded α-thioesters that were directly used in NCL without purification...
March 22, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28222263/reaction-mechanism-of-covalent-modification-of-phosphatidylethanolamine-lipids-by-reactive-aldehydes-4-hydroxy-2-nonenal-and-4-oxo-2-nonenal
#19
Katarina Vazdar, Danijela Vojta, Davor Margetić, Mario Vazdar
4-Hydroxy-2-nonenal (HNE) and 4-oxo-2-nonenal (ONE) are biologically important reactive aldehydes formed during oxidative stress in phospholipid bilayers. They are highly reactive species due to presence of several reaction centers and can react with amino acids in peptides and proteins, as well as phosphoethanolamine (PE) lipids, thus modifying their biological activity. The aim of this work is to study in a molecular detail the reactivity of HNE and ONE toward PE lipids in a simplified system containing only lipids and reactive aldehydes in dichloromethane as an inert solvent...
March 6, 2017: Chemical Research in Toxicology
https://www.readbyqxmd.com/read/28218515/chlorinated-glycopeptide-antibiotic-peptide-precursors-improve-cytochrome-p450-catalyzed-cyclization-cascade-efficiency
#20
Madeleine Peschke, Clara Brieke, Rob J A Goode, Ralf B Schittenhelm, Max J Cryle
The activity of glycopeptide antibiotics (GPAs) depends upon important structural modifications to their precursor heptapeptide backbone: specifically, the cytochrome P450-catalyzed oxidative cross-linking of aromatic side chains as well as the halogenation of specific residues within the peptide. The timing of halogenation and its effect on the cyclization of the peptide are currently unclear. Our results show that chlorination of peptide precursors improves their processing by P450 enzymes in vitro, which provides support for GPA halogenation occurring prior to peptide cyclization during nonribosomal peptide synthesis...
February 24, 2017: Biochemistry
keyword
keyword
58109
1
2
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read
×

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"