ORCID Profile
0000-0002-0080-6878
Current Organisations
Chemistry Explained
,
UDEMY
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Publisher: IOP Publishing
Date: 24-02-2016
DOI: 10.1088/0957-4484/27/13/135606
Abstract: β(3)-amino acid based polypeptides offer a unique starting material for the design of self-assembled nanostructures such as fibres and hierarchical dendritic assemblies, due to their well-defined helical geometry in which the peptide side chains align at 120° due to the 3.0-3.1 residue pitch of the helix. In a previous work we have described the head-to-tail self-assembly of N-terminal acetylated β(3)-peptides into infinite helical nanorods that was achieved by designing a bioinspired supramolecular self-assembly motif. Here we describe the effect of consecutively more polar side chains on the self-assembly characteristics of β(3)-tetrapeptides Ac-β (3)Ala-β(3)Leu-β(3)Ile-β(3)Ala (Ac-β(3)[ALIA]), Ac-β(3)Ser-β(3)Leu-β(3)Ile-β(3)Ala (Ac-β(3)[SLIA]) and Ac-β (3)Lys-β (3)Leu-β(3)Ile-β (3)Glu (Ac-β(3)[KLIE]). β(3)-tetrapeptides complete 1 1/3 turns of the helix: thus in the oligomeric form the side chain positions shift 120° with each added monomer, forming a regular periodic pattern along the nanorod. Dynamic light scattering (DLS) measurements confirmed that these peptides self-assemble even in highly polar solvents such as water and DMSO, while diffusion-ordered NMR spectroscopy revealed the presence of a substantial monomeric population. Temperature dependence of the size distribution in DLS measurements suggests a dynamic equilibrium between monomers and oligomers. Solution casting produced distinct fibrillar deposits after evaporating the solvent. In the case of the apolar Ac-β(3)[ALIA] the longitudinal helix morphology gives rise to geometrically defined (∼70°) junctions between fibres, forming a mesh that opens up possibilities for applications e.g. in tissue scaffolding. The deposits of polar Ac-β(3)[SLIA] and Ac-β(3)[KLIE] exhibit fibres in regular parallel alignment over surface areas in the order of 10 μm.
Publisher: Wiley
Date: 19-09-2011
DOI: 10.1002/APP.35072
Publisher: Springer Science and Business Media LLC
Date: 25-02-2012
Publisher: Elsevier BV
Date: 02-2014
DOI: 10.1016/J.IJBIOMAC.2013.10.044
Abstract: Three novel thiosemicarbazone O-carboxymethyl chitosan derivatives were obtained via a condensation reaction of thiosemicarbazide O-carboxymethyl chitosan with o-hydroxybenzaldehyde, p-methoxybenzaldehyde, and p- chlorobenzaldehyde respectively. Their structures were characterized by elemental analysis, FTIR, (13)C NMR and X-ray diffraction. The antimicrobial behaviors of the prepared derivatives against three types of bacteria Staphylococcus aureus (S. aureus, RCMBA 2004), Bacillus subtilis (B. subtilis, RCMBA 6005), and Escherichia coli (E. Coli, RCMBA 5003) and three crops-threatening pathogenic fungi Aspergillus fumigatus (A. fumigatus, RCMBA 06002), Geotrichum candidum (G. candidum, RCMB 05098), and Candida albicans (C. albicans, RCMB 05035) were investigated. The results indicated that the antibacterial and antifungal activities of the investigated derivatives are much higher than those of the parent O-carboxymethyl chitosan. They were more potent in case of Gram-positive bacteria than Gram-negative bacteria. The presence of electron withdrawing chlorine atom on the aryl moiety of the aldehyde portion improved greatly antimicrobial activity to be nearly equivalent to the used standard drugs.
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C4NJ01926A
Abstract: Varying the solvent offers a simple way to control superstructure polymorphism of a tri-β 3 -peptide-based supramolecular system.
Publisher: Wiley
Date: 11-10-2014
DOI: 10.1002/ADV.21479
Publisher: Walter de Gruyter GmbH
Date: 08-09-2015
Abstract: Peptides based on unnatural β 3 -amino acids offer a versatile platform for the design of self-assembling nanostructures due to the folding stability of the 14-helix and the high symmetry of the side chains inherent in this geometry. We have previously described that N-terminal acetylation (Ac-) forms a supramolecular self-assembly motif that allows β 3 -peptides to assemble head-to-tail into a helical nanorod which then further bundles into hierarchical superstructures. Here we investigate the effect of the topography of the 14-helical nanorod on lateral self-assembly. Specifically, we report on the variations in the superstructure of three isomeric peptides comprising the same three β 3 -amino acid residues: β 3 -leucine (L), β 3 -isoleucine (I) β 3 -alanine (A) to give peptides Ac-β 3 [LIA], Ac-β 3 [IAL] and Ac-β 3 [ALI]. AFM imaging shows markedly different superstructures for the three peptides. Well defined synchrotron far-infrared spectra reveal uniform geometries with a high degree of similarity between the isomeric peptides in the amide modes of the 400–650 wavenumber range. Far-IR also confirms that the C-terminal carboxyl group is free in the assemblies, thus it is solvated in the dispersant. Hence, the differences in the superstructures formed by the fibers are defined primarily by van der Waals energy minimization between the varied cross sectional morphologies of the core nanorods.
No related grants have been discovered for Dr. Rania S. Seoudi.