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Pseudopeptides are a versatile class of organic building blocks having potential applications in a wide range of domains. In the current study, N and C termini protected l-alanine based short pseudopeptide was synthesized, where 5-aminoisophthalic acid (5-AIA), a rigid non-proteogenic γ-amino butyric acid was incorporated as C-terminal residue. The single crystal X-ray analysis revealed that the l-Ala residue of the aforesaid peptide adopts ϕ and ψ values characteristic of polyproline II conformation. Self-assembly of the pseudopeptide seems to represent a supramolecular helical architecture via NH⋯O, CH⋯O hydrogen bonding and π–π interactions. [ABSTRACT FROM AUTHOR]

N-(N-benzoyl glycinyl)-N,N′-dicyclohexylurea was synthesised by conjugating N-benzoyl glycine and dicyclohexylcarbodiimide (DCC) using triethylamine as base catalyst. A single crystal X-ray diffraction study reveals that the compound self-assembles into a supramolecular sheet structure by intermolecular N–H · · · O, C–H · · · O hydrogen bonding and non-bonding van der Waals interactions. A high resolution transmission electronic microscopic (HR-TEM) image of the compound exhibits formation of fibrils in the solid state. [ABSTRACT FROM AUTHOR]

Single crystal X-ray diffraction studies show that the three designed tripeptides Boc-Leu-Aib-m-NA-NO2 (I), Boc-Phe-Aib-m-NA-NO2 (II) and Boc-Pro-Aib-m-ABA-OMe (III) (Aib, α-aminoisobutyric acid; m-NA, m-nitroaniline; m-ABA, m-aminobenzoic acid; Boc, t-butyloxycarbonyl) containing aromatic rings in the backbones adopt β-turn structures that are self-assembled through intermolecular hydrogen bonds and van der Waals interactions to create layers of β-sheets. Solvent-dependent NMR titration and CD studies show that the β-turn structures of the peptides also exist in the solution phase. The field emission scanning electron microscopic and transmission electron microscopic images of the peptides in the solid state reveal fibrillar structures of flat morphology that are formed through β-sheet mediated self-assembly of the preorganised β-turn building blocks. [ABSTRACT FROM AUTHOR]

Abstract: Single crystal X-ray diffraction studies reveal that the incorporation of meta-amino benzoic acid in the middle of a helix forming hexapeptide sequence such as in peptide I Boc-Ile(1)-Aib(2)-Val(3)-m-ABA(4)-Ile(5)-Aib(6)-Leu(7)-OMe (Aib: α-amino isobutyric acid; m-ABA: meta-amino benzoic acid) breaks the helix propagation to produce a turn-linker-turn (T-L-T) foldamer in the solid state. In the crystalline state two conformational isomers of peptide I self-assemble in antiparallel fashion through intermolecular hydrogen bonds and aromatic π–π interactions to form a molecular duplex. The duplexes are further interconnected through intermolecular hydrogen bonds to form a layer of peptides. The layers are stacked one on top of the other through van der Waals interactions to form hydrophilic channels filled with solvent methanol. [Copyright &y& Elsevier]

Abstract: Single crystal X-ray diffraction study reveals that the water soluble tetrapeptide H2N–Ile–Aib–Leu–m-ABA–CO2H, containing non-coded Aib (α-amino isobutyric acid) and m-ABA (meta-amino benzoic acid), crystallizes with two smallest possible diastereomeric β-hairpin molecules in the asymmetric unit. Although in both of the molecules the chiralities at Ile(1) and Leu(3) are S, a conformational reversal in the back bone chain is observed to produce the β-hairpins with β-turn conformations of type II and II′. Interestingly Aib which is known to adopt helical conformation, adopts unusual semi-extended conformation with : −49.5(5)°, ψ: 135.2(5)° in type II and : 50.6(6)°, ψ: −137.0(4)° in type II′ for occupying the i +1 position of the β-turns. The two hairpin molecules are further interlocked through intermolecular hydrogen bonds and electrostatic interactions between – and −+NH3 groups to form dimeric supramolecular β-hairpin aggregate in the crystal state. The CD measurement and 2D NMR study of the peptide in aqueous medium support the existence of β-hairpin structure in water. [Copyright &y& Elsevier]

Abstract: Single crystal X-ray diffraction studies and solvent dependent NMR titration reveal that the designed peptides I and II, Boc-Xx(1)-Aib(2)-Yy(3)-NH(CH2)2NH-Yy(3)-Aib(2)-Xx(1)-Boc, where Xx and Yy are Ile and Leu in peptide I and Leu and Val in peptide II, respectively, fold into a turn-linker-turn (T-L-T) conformation both in the solid state and in solution. In the crystalline state the T-L-T foldamers of peptide I and II self-assemble to form a three-dimensional framework of channels. The insides of the channels are hydrophilic and found to contain solvent CHCl3 hydrogen bonded to exposed Clocated at the turn regions. [Copyright &y& Elsevier]

Single crystal X-ray diffraction studies show that the β-turn structure of tetrapeptide I, Boc-Gly-Phe-Aib-Leu-OMe (Aib: α-amino isobutyric acid) self-assembles to a supramolecular helix through intermolecular hydrogen bonding along the crystallographic a axis. By contrast the β-turn structure of an isomeric tetrapeptide II, Boc-Gly-Leu-Aib-Phe-OMe self-assembles to a supramolecular β-sheet-like structure via a two-dimensional (a, b axis) intermolecular hydrogen bonding network and π-π interactions. FT-IR studies of the peptides revealed that both of them form intermolecularly hydrogen bonded supramolecular structures in the solid state. Field emission scanning electron micrographs (FE-SEM) of the dried fibrous materials of the peptides show different morphologies, non-twisted filaments in case of peptide I and non-twisted filaments and ribbon-like structures in case of peptide II. [ABSTRACT FROM AUTHOR]

• Potential of ninhydrin derivatives for tailoring diverse supramolecular architectures is unveiled. • Solid state structures of ninhydrin-acetamide adduct, ninhydrin- p -cresol adduct and N-inserted ninhydrin derivative are analyzed. • First cocrystal of ninhydrin family with 2-aminopyridine is disclosed. • SEM images indicate the surface morphology is greatly influenced by substitution of ninhydrin core. The present work discloses the self-assembly behaviour of differently substituted ninhydrin-based compounds in the solid state for the first time. Ninhydrin core with tunable functionalities generates varied noncovalent interactions leading to different supramolecular assembly. Single crystal X-ray diffraction study revealed that, ninhydrin-acetamide adduct 1 self-assembled to form corrugated sheet structure, whereas ninhydrin- p -cresol adduct 2 (cis dihydroxy hemiketal) containing water of crystallization was found to form water-mediated supramolecular helical architecture. On the other hand, easily achievable N-inserted ninhydrin derivative 3 derived from adduct 2 and o -aminophenol adopted helical arrangement in the crystalline state. Interestingly, novel cocrystal 4 obtained from adduct 2 was found to display helical motif through well directed hydrogen bonding with 2-aminopyridine. The supramolecular diversity arising due to the change in substitution of ninhydrin core structure was also reflected in scanning electron microscopy images. Image, graphical abstract [ABSTRACT FROM AUTHOR]