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This review provides a fresh overview of non-canonical amino acids and their applications in the design of peptidomimetics. Non-canonical amino acids appear widely distributed in nature and are known to enhance the stability of specific secondary structures and/or biological function. Contrary to the ubiquitous DNA-encoded amino acids, the structure and function of these residues are not fully understood. Here, results from experimental and molecular modelling approaches are gathered to classify several classes of non-canonical amino acids according to their ability to induce specific secondary structures yielding different biological functions and improved stability. Regarding side-chain modifications, symmetrical and asymmetrical α,α-dialkyl glycines, Cα to Cα cyclized amino acids, proline analogues, β-substituted amino acids, and α,β-dehydro amino acids are some of the non-canonical representatives addressed. Backbone modifications were also examined, especially those that result in retro-inverso peptidomimetics and depsipeptides. All this knowledge has an important application in the field of peptidomimetics, which is in continuous progress and promises to deliver new biologically active molecules and new materials in the near future., This research was funding by the following projects: UIBD/04469/2020, LA/P/0029/2020, IF/00894/2015, UIDB/50011/2020, UIDP/50011/2020, LA/P/0006/2020, UID/QUI/00686/2019 and NORTE-07-0162-FEDER-000086., Castro and Cavaco-Paulo thank the support received from the Portuguese Foundation for Science and Technology (FCT) through the strategic funding of UIDB/04469/2020 unit and by LABBELS—Associate Laboratory in Biotechnology, Bioengineering, and Microelectromechanical Systems, LA/P/0029/2020. Melle-Franco would like to acknowledge support through the project IF/00894/2015 and within the scope of the project CICECO-Aveiro Institute of Materials,UIDB/50011/2020, UIDP/50011/2020, and LA/P/0006/2020, financed by national funds through the FCT/MEC (PIDDAC). Marcos acknowledges the Portuguese Foundation for Science and Technology(FCT) for financial support through the Centre of Chemistry of the University of Minho (CQ-UM) (project UID/QUI/00686/2019). Access to computing resources funded by the Project “Search-ON2: Revitalization of HPC infrastructure of UMinho” (NORTE-07-0162-FEDER-000086), cofounded by the North Portugal Regional Operational Programme (ON.2 –O Novo Norte), under the National Strategic Reference Framework (NSRF), through the European Regional Development Fund (ERDF), is also gratefully acknowledged., info:eu-repo/semantics/publishedVersion

Self-assembled peptide-based hydrogels are archetypical nanostructured materials with a plethora of foreseeable applications in nanomedicine and as biomaterials. N-protected di- and tri-peptides are effective minimalist (molecular) hydrogelators. Independent variation of the capping group, peptide sequence and side chain modifications allows a wide chemical space to be explored and hydrogel properties to be tuned. In this work, we report the synthesis of a focused library of dehydrodipeptides N-protected with 1-naphthoyl and 2-naphthylacetyl groups. The 2-naphthylacetyl group was extensively reported for preparation of peptide-based self-assembled hydrogels, whereas the 1-naphthaloyl group was largely overlooked, owing presumably to the lack of a methylene linker between the naphthalene aromatic ring and the peptide backbone. Interestingly, dehydrodipeptides N-capped with the 1-naphthyl moiety afford stronger gels, at lower concentrations, than the 2-naphthylacetyl-capped dehydrodipeptides. Fluorescence and circular dichroism spectroscopy showed that the self-assembly of the dehydrodipeptides is driven by intermolecular aromatic π–π stacking interactions. Molecular dynamics simulations revealed that the 1-naphthoyl group allows higher order aromatic π–π stacking of the peptide molecules than the 2-naphthylacetyl group, together with hydrogen bonding of the peptide scaffold. The nanostructure of the gel networks was studied by TEM and STEM microscopy and was found to correlate well with the elasticity of the gels. This study contributes to understanding the interplay between peptide and capping group structure on the formation of self-assembled low-molecular-weight peptide hydrogels. Moreover, the results presented here add the 1-naphthoyl group to the palette of capping groups available for the preparation of efficacious low-molecular-weight peptide-based hydrogels., This work was funded by National Funds through FCT-Portuguese Foundation for Science and Technology under the Project PTDC/QUI-QOR/29015/2017, CQ/UM UID/QUI/00686/2013 and UID/QUI/0686/2016, UID/CTM/50025/2019 and CF-UM-UP (UIDB/04650/2020). The NMR spectrometers are part of the National NMR Network (PTNMR) and are partially supported by Infrastructure Project No 022161 (co-financed by FEDER through COMPETE 2020, POCI and PORL and FCT through PIDDAC)., For computing resources: Search-ON2: Revitalization of HPC infrastructure of UMinho, (NORTE-07-0162-FEDER-000086), co-funded by the North Portugal Regional Oper ational Programme (ON.2-O Novo Norte), under the National Strategic Reference Framework (NSRF), through the European Regional Development Fund (ERDF). Norte (ON.2) through the project Matepro—Optimizing Materials and Processes, with reference NORTE-07-0124-FEDER-000037 FEDER COMPETE is also acknowledged. T. Castro thanks the senior position funded by the European Union through the European Regional Development Fund (ERDF) under the Competitiveness Opera tional Program (BioCell-NanoART = Novel Bio-inspired Cellular Nano-architectures, POC-A1.1.4-E 2015 nr. 30/01.09.2016). M. Melle-Franco acknowledges support by the FCT through the programs Ciência 2008, the project IF/00894/2015 and within the Projects Scope: UID/CEC/00319/2013 and UIDB/50011/2020 and UIDP/5 0011/2020 (CICECO-Aveiro Institute of Materials). FCT Investigator Programme through grant IF/00606/2014 to L. Hilliou, is acknowledged. IWH was supported by EPSRC grant EP/L020599/1., info:eu-repo/semantics/publishedVersion

Considerable improvements in the electrocatalytic activity of 2D metal phosphorous trichalcogenides (M2 P2 X6 ) have been achieved for water electrolysis, mostly with MII 2 [P2 X6 ]4- as catalysts for hydrogen evolution reaction (HER). Herein, MI MIII P2 S6 (MI = Cu, Ag; MIII = Sc, V, Cr, In) are synthesized and tested for the first time as electrocatalysts in alkaline media, towards oxygen reduction reaction (ORR) and HER. AgScP2 S6 follows a 4 e- pathway for the ORR at 0.74 V versus reversible hydrogen electrode; CuScP2 S6 is active for HER, exhibiting an overpotential of 407 mV and a Tafel slope of 90 mV dec-1 . Density functional theory models reveal that bulk AgScP2 S6 and CuScP2 S6 are both semiconductors with computed bandgaps of 2.42 and 2.23 eV, respectively and overall similar electronic properties. Besides composition, the largest difference in both materials is in their molecular structure, as Ag atoms sit at the midpoint of each layer alongside Sc atoms, while Cu atoms are raised to a similar height to S atoms, in the external segment of the 2D layers. This structural difference probably plays a fundamental role in the different catalytic performances of these materials. These findings show that MI (Cu, Ag) together with Sc(MIII ) leads to promising achievements in MI MIII P2 S6 materials as electrocatalysts. published

Density functional theory calculations with the hybrid Heyd-Scuseria-Ernzerhof (HSE) functional were used to study the electronic structure of polymerized fullerites, ranging from one-dimensional to three-dimensional polymerized structures. We found that the bandgap across these structures decreases with the rise of the number of sp3 carbons until metallic behavior is observed. Further increase of the sp3 carbon content induces a reopening of the bandgap, showing a reentrant semiconducting behavior in this class of materials.

The synthesis of crystalline one-dimensional polymers provides a fundamental understanding about the structure-property relationship in polymeric materials and allows the preparation of materials with enhanced thermal, mechanical, and conducting properties. However, the synthesis of crystalline one-dimensional polymers remains a challenge because polymers tend to adopt amorphous or semicrystalline phases. Herein, we report the synthesis of a crystalline one-dimensional polymer in solution by dynamic covalent chemistry. The structure of the polymer has been unambiguously confirmed by microcrystal electron diffraction that together with charge transport studies and theoretical calculations show how the ?-stacked chains of the polymer generate optimal channels for charge transport.