title: Self-Assembly of Tetraphenylalanine Peptides.
abstract: Three different tetraphenylalanine (FFFF) based peptides that differ at the N- and C-termini have been synthesized by using standard procedures to study their ability to form different nanoassemblies under a variety of conditions. The FFFF peptide assembles into nanotubes that show more structural imperfections at the surface than those formed by the diphenylalanine (FF) peptide under the same conditions. Periodic DFT calculations (M06L functional) were used to propose a model that consists of three FFFF molecules defining a ring through head-to-tail NH3(+)⋅⋅⋅(-)OOC interactions, which in turn stack to produce deformed channels with internal diameters between 12 and 16 Å. Depending on the experimental conditions used for the peptide incubation, N-fluorenylmethoxycarbonyl (Fmoc) protected FFFF self-assembles into a variety of polymorphs: ultra-thin nanoplates, fibrils, and star-like submicrometric aggregates. DFT calculations indicate that Fmoc-FFFF prefers a parallel rather than an antiparallel β-sheet assembly. Finally, coexisting multiple assemblies (up to three) were observed for Fmoc-FFFF-OBzl (OBzl = benzyl ester), which incorporates aromatic protecting groups at the two peptide terminals. This unusual and noticeable feature is attributed to the fact that the assemblies obtained by combining the Fmoc and OBzl groups contained in the peptide are isoenergetic.
authors.affiliation: Department of Chemical Engineering, ETSEIB, Universitat Politècnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain).|Center for Research in Nano-Engineering, Universitat Politècnica de Catalunya, Campus Sud, Edifici C', C/Pasqual i Vila s/n, 08028 Barcelona (Spain).
authors.forename: Enric
authors.initials: E
authors.lastname: Mayans
authors.affiliation: Departamento de Química Orgánica, Instituto de Síntesis Química y Catálisis Homogénea-ISQCH, CSIC-Universidad de Zaragoza, C/ Pedro Cerbuna, 12, 50009 Zaragoza (Spain).
authors.forename: Gema
authors.initials: G
authors.lastname: Ballano
authors.affiliation: Department of Chemistry, Escola Politècnica Superior, Universitat de Lleida, C/Jaume II no 69, 25001 Lleida (Spain).
authors.forename: Jordi
authors.initials: J
authors.lastname: Casanovas
authors.affiliation: Department of Chemical Engineering, ETSEIB, Universitat Politècnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain).|Center for Research in Nano-Engineering, Universitat Politècnica de Catalunya, Campus Sud, Edifici C', C/Pasqual i Vila s/n, 08028 Barcelona (Spain).
authors.forename: Angélica
authors.initials: A
authors.lastname: Díaz
authors.affiliation: Department of Chemical Engineering, ETSEIB, Universitat Politècnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain).|Center for Research in Nano-Engineering, Universitat Politècnica de Catalunya, Campus Sud, Edifici C', C/Pasqual i Vila s/n, 08028 Barcelona (Spain).
authors.forename: Maria M
authors.initials: MM
authors.lastname: Pérez-Madrigal
authors.affiliation: Department of Chemical Engineering, EUETIB, Universitat Politècnica de Catalunya, Comte d'Urgell 187, 08036 Barcelona (Spain).
authors.forename: Francesc
authors.initials: F
authors.lastname: Estrany
authors.affiliation: Department of Chemical Engineering, ETSEIB, Universitat Politècnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain). jordi.puiggali@upc.edu.|Center for Research in Nano-Engineering, Universitat Politècnica de Catalunya, Campus Sud, Edifici C', C/Pasqual i Vila s/n, 08028 Barcelona (Spain). jordi.puiggali@upc.edu.
authors.forename: Jordi
authors.initials: J
authors.lastname: Puiggalí
authors.affiliation: Departamento de Química Orgánica, Instituto de Síntesis Química y Catálisis Homogénea-ISQCH, CSIC-Universidad de Zaragoza, C/ Pedro Cerbuna, 12, 50009 Zaragoza (Spain). cativiela@unizar.es.
authors.forename: Carlos
authors.initials: C
authors.lastname: Cativiela
authors.affiliation: Department of Chemical Engineering, ETSEIB, Universitat Politècnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain). carlos.aleman@upc.edu.|Center for Research in Nano-Engineering, Universitat Politècnica de Catalunya, Campus Sud, Edifici C', C/Pasqual i Vila s/n, 08028 Barcelona (Spain). carlos.aleman@upc.edu.
authors.forename: Carlos
authors.initials: C
authors.lastname: Alemán
mesh_terms: D004151:Dipeptides; D005449:Fluorenes / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D043942:Nanotubes / Q000737:chemistry*; D010455:Peptides / Q000138:chemical synthesis* / Q000737:chemistry*; D010649:Phenylalanine / Q000031:analogs & derivatives* / Q000138:chemical synthesis* / Q000737:chemistry*
chemical_list: D004151:Dipeptides; D005449:Fluorenes; D010455:Peptides; C026650:phenylalanylphenylalanine; D010649:Phenylalanine
keywords: beta sheet; hydrogen bonds; nanotubes; phenylalanine; pi interactions