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Diabetes is a metabolic disorder caused by the body's inability to produce or use insulin. Considering the figures projected by the World Health Organization, research on insulin therapy is crucial. Hence, we present a soft biointerface based on a thiol-yne poly(ethylene glycol) (PEG) click-hydrogel as an advanced treatment option to administrate insulin. Most importantly, the device is rendered electroactive by incorporating biocompatible poly(3,4-ethylenedioxythiophene) nanoparticles (PEDOT NPs) as conductive moieties to precisely control the release of insulin over an extended period through electrochemical stimulation (ES). The device has been carefully optimized on account of: (i) the main interactions established between PEDOT- and PEG-based moieties, which have been studied by density functional theory calculations, and reveal the choice of 4-arm PEG precursors as most suitable cross-linkers; and (ii) the concentration of PEDOT NPs in the device, which has been determined considering minimal interference with the gelation process, as well as the resulting morphological, mechanical, electrochemical, and cytocompatible properties of the PEG-based click-hydrogels. Finally, the management over insulin delivery through ES is verified in vitro, with released insulin being detected by high-performance liquid chromatography. Overall, our hydrogel-based device establishes a method for controlled insulin delivery with the potential for translation to other relevant bioelectronic applications., Competing Interests: The authors declare no competing financial interest., (© 2024 American Chemical Society.)

The influence of stereochemistry on the self-assembly of phenylalanine (Phe) dipeptides bearing aromatic fluorenyl groups at both the N- and C-termini (Fmoc, OFm) has been investigated. For this purpose, Fmoc-d-Phe-l-Phe-OFm and Fmoc-l-Phe-l-Phe-OFm have been examined considering a wide variety of solvents, which differ in dielectric constant and volatility. Results reveal that replacement of l-Phe by d-Phe has a major impact on the self-assembly propensities, restricting drastically the structural diversity and polymorphism shown by the homochiral dipeptide. Thus, the analogous heterochiral dipeptide shows a great propensity to form micro/nanofibers, independently of the environmental conditions. Theoretical calculations revealed that the stability of antiparallel disposition is much higher (a factor of ca. 15) for Fmoc-d-Phe-l-Phe-OFm than that for Fmoc-l-Phe-l-Phe-OFm, which has been attributed to the hydrophobic core formed in the former. Overall, results suggest that control of the backbone chirality is a potent and versatile strategy to drive and finely tune the self-assembly propensities of highly aromatic peptides.

Microstructures from small phenylalanine-based peptides have attracted great attention lately because these compounds are considered to be a new class of tunable materials. In spite of the extensive studies on uncapped diphenylalanine and tetraphenylalanine peptides, studies on the self-assembly of uncapped triphenylananine (FFF) are very scarce and nonsystematic. In this work, we demonstrate that FFF assemblies can organize in a wide number of well-defined supramolecular structures, which include laminated helical-ribbons, leaflike dendrimers, doughnut-, needle-, and flower-shapes. These organizations are produced by the attractive or repulsive interactions between already formed assemblies and therefore can be controlled through the choice of solvents used as the incubation medium. Thus, the formation of the desired supramolecular structures is regulated through the protonation/deprotonation of the terminal groups, the polarity of the incubation medium, which affects both peptide···solvent interactions and the cavity solvation energy (i.e., solvent···solvent interactions), and the steric interactions between own assemblies that act as building blocks. Finally, the β-sheet disposition in the latter structural motifs has been examined using both theoretical calculations and Fourier transform infrared spectroscopy. Results indicate that FFF molecules can adopt both parallel and antiparallel β-sheets. However, the former one is the most energetically favored because of the formation of π-π stacking interactions between the aromatic rings of hydrogen-bonded strands.

The pseudorotational motions of highly hydroxylated pentafuranose sugars in the free state and tethered to hydroxyapatite have been compared. The conformation pentafuranose ring remains restricted at the North region of the pseudorotational wheel, which is the one typically observed for nucleosides and nucleotides in the double helix A-RNA, when the phosphate-bearing sugar is anchored to the mineral surface. Results indicate that the severe restrictions imposed by the mineral are responsible of the double helix preservation when DNA and RNA are encapsulated in crystalline nanorods.

The intrinsic conformational properties of the N-acetyl-N'-methylamide derivatives of d-C(α)-ethylglycine (Abu), d-C(α)-methyl-C(α)-ethylglycine (Iva), and C(α,α)-diethylglycine (Deg) have been investigated using quantum mechanical calculations in the gas phase and in chloroform, dichloromethane and aqueous solutions. Although the large number of flexible dihedral angles results in many minimum energy conformations, only a few of them are energetically representative because of the repulsive interactions between the ethyl groups and the backbone atoms. The conformational restrictions imposed by such repulsions increase as follows: Abu < Iva < Deg. The most important characteristics of the investigated residues are as follows: (i) the conformation tendencies of Abu resemble those of standard residues with similar constitution (e.g., Val or Leu); (ii) the properties of Iva are relatively similar to those of C(α,α)-dimethylglycine, which is the simplest C(α,α)-dialkylated α-amino acid, even though the former is more restricted than the latter; (iii) the conformational flexibility of Deg is even lower than that of C(α,α)-dialkylated residues with bulkier side groups (e.g., C(α,α)-diphenylglycine and C(α,α)-dibenzylglycine).

Interactions, in terms of both binding energies and microscopic organization, of water molecules absorbed by hydrophilic polyaniline emeraldine base have been investigated using quantum mechanical calculations, molecular dynamics simulation, FTIR spectroscopy, and (1)H NMR. From an enthalpic point of view, water molecules interact more favorably with imine nitrogen atoms than with amine ones, even though the latter are entropically favored with respect to the former because of their two binding sites. Quantum mechanical results show that interaction energies of water molecules reversibly absorbed but organized individually around a binding site range from 3.0 to 6.3 kcal/mol, which is in good agreement with activation energies of 3-5 kcal/mol previously determined by thermodynamic measurements. The irreversible absorption of water to produce C-OH groups in rings of diimine units has been examined considering a three steps process in which water molecules act as both acidic and nucleophilic reagent. Although calculations predict that the whole process is disfavored by 5-8 kcal/mol only, FTIR and (1)H NMR detected the existence of reversibly absorbed water but not of C-OH groups. Both the binding energies and the structural information provided by molecular dynamics simulations have been used to interpret the existence of two types of physisorbed water molecules: (i) those that interact individually with polymer chains and (ii) those immersed in nanodrops that are contained within the polymeric matrix. The binding energies calculated for these two types of water molecules are fully consistent with the thermodynamic activation energies previously reported.

The interaction of polyaniline with alkylsulfonate dopants have been investigated at the atomic level using quantum mechanical methods. Calculations have been performed on complexes formed by dopant molecules with an alkyl group ranging from methyl to nonyl and model oligoanilines of different sizes. The stabilization provided by the formation of the alkylsulfonate...oligoaniline complexes (70-90 kcal/mol) is significantly higher than that found for conventional hydrogen bonds (5-12 kcal/mol) but lower than that obtained for methylsulfate...alkylammonium and methylsulfate...Na(+) systems (120-135 kcal/mol). On the other hand, the influence of size of the alkyl group contained in the dopant on the interaction is practically negligible, whereas, in opposition, the number of aniline units used to represent polyaniline significantly affects the energetics of the interaction. Specifically, the interaction energy of an alkyl-dopant molecule and an infinite polyaniline chain has been predicted to be around -65 kcal/mol. The overall results allow the conclusion that the interaction between alkylsulfonate dopants and polyaniline is a very local phenomenon.

The intrinsic conformational preferences of C (alpha,alpha)-dibenzylglycine, a symmetric alpha,alpha-dialkylated amino acid bearing two benzyl substituents on the alpha-carbon atom, have been determined using quantum chemical calculations at the B3LYP/6-31+G(d,p) level. A total of 46 minimum energy conformations were found for the N-acetyl- N'-methylamide derivative, even though only nine of them showed a relative energy lower than 5.0 kcal/mol. The latter involves C 7, C 5, and alpha' backbone conformations stabilized by intramolecular hydrogen bonds and/or N-H...pi interactions. Calculation of the conformational free energies in different environments (gas-phase, carbon tetrachloride, chloroform, methanol, and water solutions) indicates that four different minima (two C 5 and two C 7) are energetically accessible at room temperature in the gas phase, while in methanol and aqueous solutions one such minimum (C 5) becomes the only significant conformation. Comparison with results recently reported for C (alpha,alpha)-diphenylglycine indicates that substitution of phenyl side groups by benzyl enhances the conformational flexibility leading to (i) a reduction of the strain of the peptide backbone and (ii) alleviating the repulsive interactions between the pi electron density of the phenyl groups and the lone pairs of the carbonyl oxygen atoms.

DFT calculations at the B3LYP/6-311G(d,p) level have been used to investigate the intrinsic conformational preferences of 1-amino-2-phenylcyclopentane-1-carboxylic acid (c5Phe), a constrained analogue of phenylalanine in which the alpha and beta carbons are included in a cyclopentane ring. Specifically, the N-acetyl-N'-methylamide derivatives of the cis and trans stereoisomers, where cis and trans refer to the relative position between the amino group and the phenyl ring, have been calculated. Solvent effects have been examined using a self-consistent reaction field (SCRF) method. Results indicate that the conformational space of the cis stereoisomer is much more restricted than that of the trans derivative both in the gas phase and in solution.

Quantum mechanical calculations at the B3LYP/6-31+G(d,p) level have been used to investigate the intrinsic conformational preferences of alpha,alpha-diphenylglycine, a simple alpha,alpha-dialkylated amino acid bearing two phenyl substituents on the alpha-carbon, in both the gas phase and aqueous solution. Nine minimum energy conformations have been characterized for the N-acetyl-N'-methylamide derivative within a relative energy range of about 9 kcal/mol. The relative stability of these structures is largely influenced by specific backbone...side chain and side chain...side chain interactions that can be attractive (N-H...pi and C-H...pi) or repulsive (C=O...pi). On the other hand, comparison with the minimum energy conformations calculated for alpha-aminoisobutyric acid, in which the two phenyl substituents are replaced by methyl groups, revealed that the bulky aromatic rings of alpha,alpha-diphenylglycine induce strain in the internal geometry of the peptide. Finally, a set of force-field parameters for classical Molecular Mechanics calculations was developed for the investigated amino acid. Molecular Dynamics simulations in aqueous solutions have been carried out to validate the parameters obtained.

Fourier transform (FT) Raman spectroscopy was used to elucidate heat-induced structural changes of albumin, globulins, serum, and plasma protein solutions (15% w/w) as affected by pH (4.5, 6.0, and 7.5). Reduction of alpha-helix and formation of beta-sheet, disulfide bond reactions, and exposure and buriedness of hydrophobic groups and amino acid residues were observed. All of these features contributed to the formation of strong, irreversible heat-induced gels. The application of a dimensionality reducing technique such as principal component analysis proved to be useful to determine the most influential qualities of protein samples, as well as the pH-dependent behavior of some of the attributes of both unheated and heated solutions. Analysis of Raman spectra in terms of differences demonstrated the interactions of albumin and globulins in co-occurrence and the significant role of fibrinogen on the gel's attributes.

Quantum mechanical methods have been used to investigate the intrinsic conformational preferences of 1-amino-2,2-diphenylcyclopropanecarboxylic acid (c(3)Dip), a cyclopropane analogue of phenylalanine bearing two phenyl substituents on the same beta-carbon. Geometries, energies, and frequencies were calculated on the N-acetyl-N'-methylamide derivative at the HF and B3LYP levels using the 6-31G(d), 6-311G(d), and 6-31+G(d,p) basis sets. Four minimum energy conformations were characterized: axial C(7), equatorial C(7), right-handed helix, and polyproline II. Analysis of the whole results, which are fully consistent with available experimental data, indicates that c(3)Dip tends to promote gamma-turn conformations.