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Helical cyclic peptide

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https://www.readbyqxmd.com/read/27804871/the-sam-domain-of-epha2-receptor-and-its-relevance-to-cancer-a-novel-challenge-for-drug-discovery
#1
Flavia Mercurio, Marilisa Leone
BACKGROUND: Eph receptors play important functions in developmental processes and diseases and among them EphA2 is well known for its controversial role in cancer. Drug discovery strategies are mainly centered on EphA2 extracellular ligand-binding domain however, the receptor also contains a largely unexplored cytosolic Sam (Sterile alpha motif) domain at the C-terminus. EphA2-Sam binds the Sam domain from the lipid phosphatase Ship2 and the first Sam domain of Odin. Sam-Sam interactions may be important to regulate ligand-induced receptor endocytosis and degradation i...
November 1, 2016: Current Medicinal Chemistry
https://www.readbyqxmd.com/read/27589588/one-dimensional-supramolecular-nanoplatforms-for-theranostics-based-on-co-assembly-of-peptide-amphiphiles
#2
Inhye Kim, Eun Hee Han, Jooyeon Ryu, Jin-Young Min, Hyungju Ahn, Young-Ho Chung, Eunji Lee
We report a simple and facile strategy for the preparation of multifunctional nanoparticles with programmable properties using self-assembly of precisely designed block amphiphiles in an aqueous solution-state. Versatile, supramolecular nanoplatform for personalized needs, particularly-theranostics, was fabricated by coassembly of peptide amphiphiles (PAs) in aqueous solution, replacing time-consuming and inaccessible chemical synthesis. Fibrils, driven by the assembly of hydrophobic β-sheet-forming peptide block, were utilized as a nanotemplate for drug loading within their robust core...
October 10, 2016: Biomacromolecules
https://www.readbyqxmd.com/read/27539268/homooligomeric-%C3%AE-3-r-valine-peptides-transformation-between-c14-and-c12-helical-structures-induced-by-a-guest-aib-residue
#3
Basavalingappa Vasantha, Gijo George, Srinivasarao Raghothama, Padmanabhan Balaram
Novel helical, structures unprecedented in the chemistry of α-polypeptides, may be found in polypeptides containing β and γ amino acids. The structural characterization of C12 and C14 -helices in oligo β-peptides was originally achieved using conformationally constrained cyclic β-residues. This study explores the conformational characteristics of proteinogenic β(3) residues in homooligomeric sequences and addresses the issue of inducing a transition between C14 and C12 helices by the introduction of a guest α-residue...
August 19, 2016: Biopolymers
https://www.readbyqxmd.com/read/27529788/impact-of-%C3%AE-amino-acid-residue-preorganization-on-%C3%AE-%C3%AE-peptide-foldamer-helicity-in-aqueous-solution
#4
Brian F Fisher, Samuel H Gellman
α/γ-Peptide foldamers containing either γ(4)-amino acid residues or ring-constrained γ-amino acid residues have been reported to adopt 12-helical secondary structure in nonpolar solvents and in the solid state. These observations have engendered speculation that the seemingly flexible γ(4) residues have a high intrinsic helical propensity and that residue-based preorganization may not significantly stabilize the 12-helical conformation. However, the prior studies were conducted in environments that favor intramolecular H-bond formation...
August 31, 2016: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/27384597/helical-peptide-catalyzed-enantioselective-michael-addition-reactions-and-their-mechanistic-insights
#5
Atsushi Ueda, Tomohiro Umeno, Mitsunobu Doi, Kengo Akagawa, Kazuaki Kudo, Masakazu Tanaka
Helical peptide foldamer catalyzed Michael addition reactions of nitroalkane or dialkyl malonate to α,β-unsaturated ketones are reported along with the mechanistic considerations of the enantio-induction. A wide variety of α,β-unsaturated ketones, including β-aryl, β-alkyl enones, and cyclic enones, were found to be catalyzed by the helical peptide to give Michael adducts with high enantioselectivities (up to 99%). On the basis of X-ray crystallographic analysis and depsipeptide study, the amide protons, N(2)-H and N(3)-H, at the N terminus in the α-helical peptide catalyst were crucial for activating Michael donors, while the N-terminal primary amine activated Michael acceptors through the formation of iminium ion intermediates...
August 5, 2016: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27356149/recent-advances-in-self-assembled-peptides-implications-for-targeted-drug-delivery-and-vaccine-engineering
#6
Sharareh Eskandari, Thalia Guerin, Istvan Toth, Rachel J Stephenson
Self-assembled peptides have shown outstanding characteristics for vaccine delivery and drug targeting. Peptide molecules can be rationally designed to self-assemble into specific nanoarchitectures in response to changes in their assembly environment including: pH, temperature, ionic strength, and interactions between host (drug) and guest molecules. The resulting supramolecular nanostructures include nanovesicles, nanofibers, nanotubes, nanoribbons, and hydrogels and have a diverse range of mechanical and physicochemical properties...
June 26, 2016: Advanced Drug Delivery Reviews
https://www.readbyqxmd.com/read/27237543/the-side-chain-hydroxy-groups-of-a-cyclic-%C3%AE-%C3%AE-disubstituted-%C3%AE-amino-acid-promote-oligopeptide-310-helix-packing-in-the-crystalline-state
#7
Yosuke Demizu, Mitsunobu Doi, Hiroko Yamashita, Takashi Misawa, Makoto Oba, Masaaki Kurihara, Hiroshi Suemune, Masakazu Tanaka
A single chiral cyclic α,α-disubstituted amino acid with side-chain methoxymethyl (MOM) protecting groups, (3S,4S)-1-amino-(3,4-dimethoxymethoxy)cyclopentanecarboxylic acid [(S, S)-Ac5 c(dOMOM) ], or side-chain hydroxy groups, (3S,4S)-1-amino-(3,4-dihydroxy)cyclopentanecarboxylic acid [(S, S)-Ac5 c(dOH) ], was attached to the N-terminal or C-terminal position of α-aminoisobutyric acid (Aib) tetrapeptide segments; i.e., we designed and synthesized four pentapeptides, Cbz-[(S, S)-Ac5 c(dOMOM) ]-(Aib)4 -OEt (1), Cbz-[(S, S)-Ac5 c(dOH) ]-(Aib)4 -OEt (2), Cbz-(Aib)4 -[(S, S)-Ac5 c(dOMOM) ]-OMe (3), and Cbz-(Aib)4 -[(S, S)-Ac5 c(dOH) ]-OMe (4)...
September 2016: Biopolymers
https://www.readbyqxmd.com/read/27226426/helix-nucleation-by-the-smallest-known-%C3%AE-helix-in-water
#8
Huy N Hoang, Russell W Driver, Renée L Beyer, Timothy A Hill, Aline D de Araujo, Fabien Plisson, Rosemary S Harrison, Lena Goedecke, Nicholas E Shepherd, David P Fairlie
Cyclic pentapeptides (e.g. Ac-(cyclo-1,5)-[KAXAD]-NH2 ; X=Ala, 1; Arg, 2) in water adopt one α-helical turn defined by three hydrogen bonds. NMR structure analysis reveals a slight distortion from α-helicity at the C-terminal aspartate caused by torsional restraints imposed by the K(i)-D(i+4) lactam bridge. To investigate this effect on helix nucleation, the more water-soluble 2 was appended to N-, C-, or both termini of a palindromic peptide ARAARAARA (≤5 % helicity), resulting in 67, 92, or 100 % relative α-helicity, as calculated from CD spectra...
July 11, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27171550/effects-of-single-%C3%AE-to-%C3%AE-residue-replacements-on-structure-and-stability-in-a-small-protein-insights-from-quasiracemic-crystallization
#9
Dale F Kreitler, David E Mortenson, Katrina T Forest, Samuel H Gellman
Synthetic peptides that contain backbone modifications but nevertheless adopt folded structures similar to those of natural polypeptides are of fundamental interest and may provide a basis for biomedical applications. Such molecules can, for example, mimic the ability of natural prototypes to bind to specific target macromolecules but resist degradation by proteases. We have previously shown that oligomers containing mixtures of α- and β-amino acid residues ("α/β-peptides") can mimic the α-helix secondary structure, and that properly designed α/β-peptides can bind to proteins that evolved to bind to α-helical partners...
May 25, 2016: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/27165406/anionic-host-defence-peptides-from-the-plant-kingdom-their-anticancer-activity-and-mechanisms-of-action
#10
Frederick Harris, Saurabh Prabhu, Sarah R Dennison, Timothy J Snape, Robert Lea, Manuela Mura, David A Phoenix
It is becoming increasingly clear that plants ranging across the plant kingdom produce anionic host defence peptides (AHDPs) with potent activity against a wide variety of human cancers cells. In general, this activity involves membrane partitioning by AHDPs, which leads to membranolysis and / or internalization to attack intracellular targets such as DNA. Several models have been proposed to describe these events including: the toroidal pore and Shai-Matsuzaki-Huang mechanisms but, in general, the mechanisms underpinning the membrane interactions and anticancer activity of these peptides are poorly understood...
2016: Protein and Peptide Letters
https://www.readbyqxmd.com/read/26900964/%C3%AE-aapeptides-design-structure-and-applications
#11
Yan Shi, Peng Teng, Peng Sang, Fengyu She, Lulu Wei, Jianfeng Cai
The development of sequence-specific peptidomimetics has led to a variety of fascinating discoveries in chemical biology. Many peptidomimetics can mimic primary, secondary, and even tertiary structure of peptides and proteins, and because of their unnatural backbones, they also possess significantly enhanced resistance to enzymatic hydrolysis, improved bioavailability, and chemodiversity. It is known that peptide nucleic acids (PNAs) are peptidic sequences developed for the mimicry of nucleic acids; however, their unique backbone as the molecular scaffold of peptidomimetics to mimic structure and function of bioactive peptides has not been investigated systematically...
March 15, 2016: Accounts of Chemical Research
https://www.readbyqxmd.com/read/26800011/conformational-studies-on-peptides-having-dipropylglycine-dpg-or-1-aminocycloheptanecarboxylic-acid-ac7-c-within-the-sequence-of-l-leucine-leu-residues
#12
Makoto Oba, Hikaru Nonaka, Mitsunobu Doi, Masakazu Tanaka
A conformational analysis of peptides having dipropylglycine (Dpg) or 1-aminocycloheptanecarboxylic acid (Ac7 c) within L-leucine (Leu) residues was conducted in solution and in a crystal state. Dpg and Ac7 c had similar structures with acyclic and cyclic side chains, respectively. FT-IR, (1) H NMR, and CD spectra measurements revealed that the preferred conformations of Dpg- and Ac7 c-containing L-Leu peptides in solution were similar; both had a right-handed (P) 310 -helix. The Dpg-containing octapeptide adopted a right-handed (P) α-helix in the crystal state...
January 22, 2016: Biopolymers
https://www.readbyqxmd.com/read/26560998/a-helix-stabilized-cell-penetrating-peptide-as-an-intracellular-delivery-tool
#13
Hiroko Yamashita, Makoto Oba, Takashi Misawa, Masakazu Tanaka, Takayuki Hattori, Mikihiko Naito, Masaaki Kurihara, Yosuke Demizu
Two types of cationic cyclic α,α-disubstituted α-amino acids: ApiC2NH2 (which possesses a lysine mimic side chain) and Api(C2Gu) (which possesses an arginine mimic side chain), were developed. These amino acids were incorporated into an arginine-based peptide sequence [(L-Arg-L-Arg-dAA)3: dAA=ApiC2NH2 or Api(C2Gu)], and the relationship between the secondary structures of the resulting peptides and their ability to pass through cell membranes was investigated. The peptide containing Api(C2Gu) formed a stable α-helical structure and was more effective at penetrating cells than the nonhelical Arg nonapeptide (R9)...
January 2016: Chembiochem: a European Journal of Chemical Biology
https://www.readbyqxmd.com/read/26522088/interactions-of-a-potent-cyclic-peptide-inhibitor-with-the-light-chain-of-botulinum-neurotoxin-a-insights-from-x-ray-crystallography
#14
Desigan Kumaran, Michael Adler, Matthew Levit, Michael Krebs, Richard Sweeney, Subramanyam Swaminathan
The seven antigenically distinct serotypes (A-G) of botulinum neurotoxin (BoNT) are responsible for the deadly disease botulism. BoNT serotype A (BoNT/A) exerts its lethal action by cleaving the SNARE protein SNAP-25, leading to inhibition of neurotransmitter release, flaccid paralysis and autonomic dysfunction. BoNTs are dichain proteins consisting of a ∼ 100 kDa heavy chain and a ∼ 50 kDa light chain; the former is responsible for neurospecific binding, internalization and translocation, and the latter for cleavage of neuronal SNARE proteins...
November 15, 2015: Bioorganic & Medicinal Chemistry
https://www.readbyqxmd.com/read/26274368/peptide-flatlandia-a-new-concept-peptide-for-positioning-of-electroactive-probes-in-proximity-to-a-metal-surface
#15
Edoardo Longo, Karen Wright, Mario Caruso, Emanuela Gatto, Antonio Palleschi, Manuela Scarselli, Maurizio De Crescenzi, Marco Crisma, Fernando Formaggio, Claudio Toniolo, Mariano Venanzi
A helical hexapeptide was designed to link in a rigid parallel orientation to a gold surface. The peptide sequence of the newly synthesized compound is characterized by the presence of two 4-amino-1,2-dithiolane-4-carboxylic acid (Adt) residues (positions 1 and 4) to promote a bidentate interaction with the gold surface, two L-Ala residues (positions 2 and 5) and two-aminoisobutyric acid (Aib) residues (positions 3 and 6) to favor a high population of the 310-helix conformation. Furthermore, a ferrocenoyl (Fc) probe was inserted at the N-terminus to investigate the electronic conduction properties of the peptide...
October 7, 2015: Nanoscale
https://www.readbyqxmd.com/read/26219086/modular-design-of-self-assembling-peptide-based-nanotubes
#16
Natasha C Burgess, Thomas H Sharp, Franziska Thomas, Christopher W Wood, Andrew R Thomson, Nathan R Zaccai, R Leo Brady, Louise C Serpell, Derek N Woolfson
An ability to design peptide-based nanotubes (PNTs) rationally with defined and mutable internal channels would advance understanding of peptide self-assembly, and present new biomaterials for nanotechnology and medicine. PNTs have been made from Fmoc dipeptides, cyclic peptides, and lock-washer helical bundles. Here we show that blunt-ended α-helical barrels, that is, preassembled bundles of α-helices with central channels, can be used as building blocks for PNTs. This approach is general and systematic, and uses a set of de novo helical bundles as standards...
August 26, 2015: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/26212593/fine-tuning-of-%C3%AE-peptide-foldamers-a-single-atom-replacement-holds-back-the-switch-from-an-8-helix-to-a-12-helix
#17
Amandine Altmayer-Henzien, Valérie Declerck, Jonathan Farjon, Denis Merlet, Régis Guillot, David J Aitken
Cyclic homologated amino acids are important building blocks for the construction of helical foldamers. N-aminoazetidine-2-carboxylic acid (AAzC), an aza analogue of trans-2-aminocyclobutanecarboxylic acid (tACBC), displays a strong hydrazino turn conformational feature, which is proposed to act as an 8-helix primer. tACBC oligomers bearing a single N-terminal AAzC residue were studied to evaluate the ability of AAzC to induce and support an 8-helix along the oligopeptide length. While tACBC homooligomers assume a dominant 12-helix conformation, the aza-primed oligomers preferentially adopt a stabilized 8-helix conformation for an oligomer length up to 6 residues...
September 7, 2015: Angewandte Chemie
https://www.readbyqxmd.com/read/26196513/snake-cathelicidin-na-cath-and-smaller-helical-antimicrobial-peptides-are-effective-against-burkholderia-thailandensis
#18
Ryan J Blower, Stephanie M Barksdale, Monique L van Hoek
Burkholderia thailandensis is a Gram-negative soil bacterium used as a model organism for B. pseudomallei, the causative agent of melioidosis and an organism classified category B priority pathogen and a Tier 1 select agent for its potential use as a biological weapon. Burkholderia species are reportedly "highly resistant" to antimicrobial agents, including cyclic peptide antibiotics, due to multiple resistance systems, a hypothesis we decided to test using antimicrobial (host defense) peptides. In this study, a number of cationic antimicrobial peptides (CAMPs) were tested in vitro against B...
2015: PLoS Neglected Tropical Diseases
https://www.readbyqxmd.com/read/26176689/%C3%AE-peptoid-foldamers-at-last
#19
Jonas S Laursen, Jens Engel-Andreasen, Christian A Olsen
For a long time, peptides were considered unsuitable for drug development due to their inherently poor pharmacokinetic properties and proteolytic susceptibility. However, this paradigm has changed significantly in the past decade with the approval of numerous antibodies and proteins as drugs. In parallel, research in the field of synthetic molecules that are able to mimic or complement folding patterns exhibited by biopolymers, but are not recognized by proteases, have received considerable attention as well...
October 20, 2015: Accounts of Chemical Research
https://www.readbyqxmd.com/read/26033954/a-short-helix-formed-by-cyclic-%C3%AE-2-3-aminoxy-peptides-in-protic-solvents
#20
Yu Hao, Ke An, Dan-Wei Zhang, Dan Yang
Water-soluble cyclic β(2,3)-aminoxy peptides have been successfully prepared and characterized in polar organic solvents and aqueous media. The monomeric and oligomeric peptides exhibit unique β N-O turns and helical conformations, with extraordinary stability toward a wide range of pH values and temperatures.
October 2015: Chemistry, An Asian Journal
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