1,720,971 research outputs found
Sintesi di derivati perilenici funzionalizzati con amminoacidi come nuovi ligandi del DNA G-quadruplex
No full textPEPTIDES WITH REGULAR ENANTIOMERIC SEQUENCES: A WIDE CLASS OF MODULAR SELF ASSEMBLING ARCHITECTURES
No full textOrganic trans-annular assemblies constitute an expanding class of structures with promising applications
for the design of nanotechnological devices. Among the strategies developed for the engineering
of organic nanotubes, those characterized by regular alternating enantiomeric amino acid
sequences have been proven particularly useful. In fact, cyclic peptides with an even number of
regularly alternating D- and L-amino acids have the tendency to adopt local -conformation that
are capable of forming trans-annular self-assembling architectures, hydrogen bond directed. The
formation of such structures is the result of the conformational equivalence of the monomer units,
a general principle that associates stereo-chemical to chemical equivalence in a polymer chain.
For configurationally alternating sequences the conformational equivalence produces cyclic structures,
where a monomer unit is related to the adjacent along the chain by a roto-reflection axis,
Sn. A slight relaxation of the conformational equivalence can formally transform a cyclic structure
into a conformationally quasi-equivalent helical structures characterized by the presence of polar
inner channels, which allow the transient binding for an activated flow of specific ions. To prove our
early predictions, we synthesized different alternating polypeptide and the corresponding linear and
cyclic oligopeptides and investigated their conformations by NMR and CD spectroscopy as well as
the formation of self-assembling structures by increasing the concentration in solution. Moreover,
their predicted ability to behave as an ion-channel across bilayer membranes are investigated and
experimental evidence of single molecule conducting events are reported. Finally, the possibility
is suggested to obtain self-assembled trans-annular structures by chemically bridging the amino
acid side chains stabilized using different strategies. A complex construct with good perspective for
nano-technological applications is proposed in which cyclic DL-lysine side chains are bridged by
the formation of salycilaldimmine metal chelates
Stereoselective Synthesis of 4,5-Epoxy-1,2-Oxazin-6-ones via Reaction of beta-Lithiated Oxazolinyloxiranes with Nitrones
No full textAn Organocatalytic Approach to the Synthesis of Six-Membered Heterocycles
No full textIn the last few years, the new era of organocatalysis opened up an effective and efficient way to high yielding metal free, enantio- and diastereoselective reactions leading to six-membered heterocycles. This review provides an overview of the current achievements in the organocatalytic synthesis of these crucial building blocks. Ranging from hetero-Diels-Alder to cycloadditions, from one step cyclizations to cascade reactions, recent results offer new powerful tools to obtain six membered heterocycles with facile procedures in high yields and stereoselection, often leading to many new stereogenic centres in a single reaction. The total syntheses of natural products having heterocyclic ring formation as crucial stage, are also reported. When available, alternative supported organocatalysts have been examined
Stereoselective Synthesis of Novel 4,5-Epoxy-1,2-Oxazin-6-ones and α,β-Epoxy-γ-amino Acids from β-Lithiated Oxazolinyloxiranes and Nitrones
No full textA stereoselective synthesis of 9,10-epoxy-1,6-dioxa-4,7-diazaspiro[4,5] decanes has been developed on the basis of the addition of beta-lithiated oxazolinyloxiranes to nitrones. Conversion of these spirocyclic derivatives into 4,5-epoxy-1,2-oxazin-6-ones and successively into alpha,beta-epoxy-amino gamma- acids, alpha-hydroxy-gamma-amino acids, and gamma-butyrolactams is described
Sintesi e studio di ciclopeptidi con sequenze enantiomeriche alternanti per architetture molecolari transanulari
No full textSelf-assembling octapeptide-polymer conjugates as promising candidates for drug delivery
No full textSoft biomaterials based on peptide-polymer conjugates open new horizons for nanomedicine. They are able to self-assemble into nanostructures useful for drug delivery, the properties of which can be finely tuned at nanometer scale. Among the strategies developed for peptide engineering, those characterized by regularly alternating enantiomeric sequences are particularly attractive, since they provide low-pitch helices that self-assemble in stacks directed and stabilized by hydrogen bonds where the peripheral side chains, are available to be functionalized with various molecules, such as polymers. When the peptide and polymer are suitably chosen in order to achieve core-shell morphology, these conjugates are able to self-assemble in water in stable nanoparticles (NPs) with enhanced circulation half-life. Herein, the self-assembling properties of the hybrid conjugates Cbz-(L-Ala-D-Val)4-NH-(CH2-CH2-O)45-CH3 (Pep8-PEG) and For-(D-Phe-L-Cys(Acm))4-NH-(CH2-CH2-O)45-CH3 (Pep8Phe-PEG) are investigated and compared. The structural properties of NPs formed for self-assembling of the conjugates were assessed by NMR, CD and fluorescence spectroscopies, DLS, and TEM microscopies
Cyclopeptides with regular enantiomeric sequences: a wide class of modular architectures for nanotechnological applications
No full textSelf-assembling peptide-polymer conjugates as promising candidates for drug delivery and imaging
No full textSoft biomaterials based on peptide-polymer conjugates open new horizons for nanomedicine. They are able to self-assemble into nanostructures useful for drug delivery and imaging, the properties of which can be finely tuned at nanometer scale. Among the strategies developed for peptide engineering, those characterized by regularly alternating enantiomeric sequences are particularly attractive, since they provide low-pitch helices that self-assemble in stacks directed and stabilized by hydrogen bonds where the peripheral side chains are available to be functionalized with various molecules, such as polymers. When the peptide and polymer are suitably chosen in order to achieve core-shell morphology, these conjugates are able to self-assemble in water in stable nanoparticles (NPs) with enhanced circulation half-life. Herein, the self-assembling properties of the hybrid conjugates Cbz-(L-Ala-D-Val)2-NH-(CH2-CH2-O)45-CH3 (Pep4-PEG), Cbz-(L-Ala-D-Val)3-NH-(CH2-CH2-O)45-CH3 (Pep6-PEG) and Cbz-(l-Ala-d-Val)4-NH-(CH2-CH2-O)45-CH3 (Pep8-PEG) are investigated and compared. They were obtained end-linking the proper linear peptide, synthesized via solid-phase peptide synthesis, to a poly(ethylene glycol) chain. The conformational properties of the conjugates and their self-assembling capability were assessed by NMR, CD and fluorescence spectroscopies, DLS, SEM, AFM and TEM microscopies. Finally, the ability of the NPs to encapsulate hydrophobic drugs was evaluated by using curcumin
D,L peptides as strong inhibitors of HIV-1 GP120.
No full textSome linear D,L-peptides with regular enantiomeric sequences that act as potential ligands to the glycan portion of HIV-1 gp120 are identified. The aim of this work is to improve the binding affinity and specificity of such structures as well as their pharmacokinetic properties through medicinal chemistry efforts, using an effective and very versatile method of synthesis that gives easy access to the proposed structures which may also be subjected to further modifications
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