RESUMO
The possibility of introducing various functionalities on peptides with relative ease allows them to be used for molecular applications. However, oligopeptides prepared entirely from proteinogenic amino acids seldom assemble as ordered structures on surfaces. Therefore, sidechain modifications of peptides that can increase the intermolecular interactions without altering the constitution of a given peptide become an attractive route to self-assembling them on surfaces. We find that replacing phenylalanine residues with unusual amino acids that have phenylcarbonyl sidechains in oligopeptides increases the formation of ordered self-assembly on a highly ordered pyrolytic graphite surface. Peptides containing the modified amino acids provided extended long-range ordered assemblies, while the analogous peptides containing phenylalanine residues failed to form long-range assemblies. X-ray crystallographic analysis of the bulk structures of these peptides and the analogous peptides containing phenylalanine residues reveal that such modifications do not alter the secondary structure in crystals. It also reveals that the secondary hydrogen bonding interaction through phenylcarbonyl sidechains facilitates extended growth of the peptides on graphite.
RESUMO
BACKGROUND: Diabetic foot ulcer (DFU) is a serious health issue of diabetes mellitus that affects innumerable people worldwide. Management and treatment of this complication are challenging, especially for those whose immune system is weak. AIM: To discuss the plants and their parts used to heal DFU, along with the mode of their administration in diabetic patients. METHODS: The original articles on "the plants for the treatment of DFU" studied in clinical cases only were obtained from various bibliographic databases using different keywords. RESULTS: The search resulted in 22 clinical cases records with 20 medicinal plants belonging to 17 families on 1553 subjects. The fruits and leaves were the most preferentially used parts for DFU treatment, regardless of whether they were being administered orally or applied topically. Of the 20 medicinal plants, 19 reported their effectiveness in increasing angiogenesis, epithelialization, and granulation, thus hastening the wound-healing process. The efficacy of these botanicals might be attributed to their major bioactive compounds, such as actinidin and ascorbic acid (in Actinidia deliciosa), 7-O-(ß-D-glucopyranosyl)-galactin (in Ageratina pichinchensis), omega-3-fatty acid (in Linum usitatissimum), isoquercetin (in Melilotus officinalis), anthocyanins (in Myrtus communis), and plantamajoside (in Plantago major). CONCLUSION: The validation of mechanisms of action underlying these phytocompounds contributing to the management of DFU can aid in our better understanding of creating efficient treatment options for DFU and its associated problems.
RESUMO
An isolated uncharged hydrogen bond acceptor such as the carbonyl functionality of an aldehyde or a keto group is absent in natural amino acids. Although glutamine and asparagine are known to hydrogen bond through the amide carbonyl group in their side chains, they also possess the amide NH2 group, which can act as a hydrogen bond donor. This makes the structural study of peptides containing an oxo residue, with an isolated carbonyl group in the side chain, interesting. Here, we report the synthesis of δ- and ε-oxo amino acids and their incorporation into oligopeptides as the N-terminal residue. The resultant oxo peptides were extensively studied using X-ray crystallography to understand the interactions offered by the oxo group in peptide crystals. We find that the oxo groups are capable of providing additional hydrogen bonding opportunities to the peptides, resulting in increased intermolecular interactions in crystals. The study thus offers avenues for the utilization of oxo residues to introduce intermolecular interactions in synthetic peptides.
