| 1. |
- Buchanan, Claire, et al.
(författare)
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C-amidation of substituted β 3oligoamides yields novel supramolecular assembly motif
- 2022
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 33:2
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Tidskriftsartikel (refereegranskat)abstract
- N-acylated substituted β 3 oligoamides are known to form unique supramolecular nanorods based on a 3-point hydrogen bond self-assembly motif. This motif is an intermolecular extension of the hydrogen bonding network that stabilizes the 14-helix secondary structure unique to β 3 oligoamides. Acetylation of the N-terminus of the molecule provides the necessary third hydrogen bond pair of the motif. Here, the possibility of introducing the third hydrogen bond pair via amidation of the C terminus is investigated. While similar in purpose, this modification introduces a chemically distinct new self-assembly motif, also removing the bulky carboxyl group that does not fold into the 14 helix positioning instead as a side chain. Three substituted β 3 oligoamide variants with the base sequence LIA (where the letters denote β 3 residues with side chains analogous to α amino acids) were compared: N-acylated Ac-β 3[LIA] as a reference, C-amidated β 3[LIA]-CONH2, and β 3[LIA] with free unmodified N and C termini as a negative control. The three variants were dissolved in water to promote self-assembly. The self-assembly was characterised using mid- and far-infrared spectroscopy, small angle x-ray scattering (SAXS) and atomic force microscopy (AFM). IR measurements confirmed that all three samples were in a similar conformation, consistent with pseudo 14-helical secondary structures. Far-infrared spectroscopy measurements of β 3[LIA]-CONH2 showed distinct peaks consistent with highly organised skeletal modes, i.e. regular supramolecular assembly, that was largely absent from the other two oligoamides. Modelling of SAXS data is consistent with elliptical cylinder structures resulting from nanorod bundling for both β 3[LIA]-CONH2 and Ac-β 3[LIA], but not in the unmodified sample. Consistently, AFM imaging showed large nanorod bundling structures in β 3[LIA]-CONH2, varied bundling structures in Ac-β 3[LIA], and only aggregation in β 3[LIA]. Amidation showed much more organised and robust assembly compared to acetylation, providing a new, easy to synthesize self-assembly motif for helical nanorod assembly that is similar but distinct to N-acylation
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| 2. |
- Wang, Guang, et al.
(författare)
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Controlling phase and rheological behaviours of hexagonal lyotropic liquid crystalline templates for nanostructural administration and retention
- 2022
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier. - 0021-9797 .- 1095-7103. ; 607, s. 816-825
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Tidskriftsartikel (refereegranskat)abstract
- Introducing polymerizable monomers into a binary hexagonal lyotropic liquid crystalline (LLC) template is a straightforward way for retaining the nanostructure but will decrease attractive intra-and inter aggregate interactions. It is therefore crucial to understand the interfacial interactions at nanoscale after introducing the monomers but prior to polymerization. Herein, active species, poly (ethylene glycol) diacrylate (PEGDA) and 2-hydroxyethyl methacrylate (HEMA), were introduced into hexagonal LLC of dodecyl trimethylammonium bromide and water to explore the structural variables, dimensional stabil-ity, and dynamic property. At a proper volume ratio of PEGDA/HEMA (1/4), the system presents excellent homogeneity with a higher dimensional stability and lower dynamic property from rheological assess-ments, thereby achieving robust, free-standing, and transparent membranes after photo -polymerization. The unique property of the system also lies in the much lower order-disorder transition temperature (45 degrees C) that facilitates the reorientation of mesochannels. They are in contrast inaccessible for the ternary system only with PEGDA, though the nanostructure for both systems could be retained. An insight into subtle variations in these parameters allows us to prepare a polymerizable template possess-ing higher dimensional stability and suitable flexibility via molecular design, thereby enabling simulta-neous structural alignment and retention for the development of functional nanomaterials. (c) 2021 Elsevier Inc. All rights reserved.
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