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Journal Articles

Permanent URI for this collectionhttps://repository.unesco.gov.ph/handle/123456789/50

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    Synthesis and biological evaluation of cyanobacterial-inspired peptides
    Casanova, Jannelle R.; Villaraza, Aaron Joseph L.; Salvador-Reyes, Lilibeth (Philippine-American Academy of Science and Engineering, 2024-03-18)
    Cyanobacteria are known producers of structurally diverse and potent natural products; the majority are peptides with unique modifications. Yet, there remains a huge underexplored chemodiversity from cyanobacteria. Here, we designed a linear octapeptide as a product of combinatorial peptide design inspired by the natural products from the filamentous cyanobacteria Hapalosiphon welwitschii and Leptolyngbya sp. The target peptide was synthesized via solid-phase peptide synthesis (SPPS) using fluorenylmethyloxycarbonyl-protecting group (Fmoc) strategy. Structural diversity was expanded by the substitution of unnatural amino acids to yield five analogues. The structure and sequence of the synthesized peptides were confirmed using nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS). Biological activity evaluation was done; with none of the peptides showing antimicrobial or cytotoxic activities against microbial pathogens and mammalian cells, respectively. To our knowledge, this study is the first to report a combinatorial peptide design inspired by a natural product and a predicted biosynthetic product. This strategy of peptide design expands the chemistry of a known bioactive natural product with the aid of unexplored cyanobacterial biosynthetic gene clusters.
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    Using constellation pharmacology to characterize a novel α-conotoxin from Conus ateralbus
    Neves, Jorge L. B.; Urcino, Cristoval; Chase, Kevin; Dowell, Cheryl; Hone, Arik J.; Morgenstern, David; Chua, Victor M.; Ramiro, Iris Bea L.; Imperial, Julita S.; Leavitt, Lee S.; Phan, Jasmine; Fisher, Fernando A.; Watkins, Maren; Raghuraman, Shrinivasan; Tun, Jortan O.; Ueberheide, Beatrix M.; McIntosh, J. Michael; Vasconcelos, Vitor; Olivera, Baldomero M.; Gajewiak, Joanna (MDPI, 2024-02-29)
    The venom of cone snails has been proven to be a rich source of bioactive peptides that target a variety of ion channels and receptors. α-Conotoxins (αCtx) interact with nicotinic acetylcholine receptors (nAChRs) and are powerful tools for investigating the structure and function of the various nAChR subtypes. By studying how conotoxins interact with nAChRs, we can improve our understanding of these receptors, leading to new insights into neurological diseases associated with nAChRs. Here, we describe the discovery and characterization of a novel conotoxin from Conus ateralbus, αCtx-AtIA, which has an amino acid sequence homologous to the well-described αCtx-PeIA, but with a different selectivity profile towards nAChRs. We tested the synthetic αCtx-AtIA using the calcium imaging-based Constellation Pharmacology assay on mouse DRG neurons and found that αCtx-AtIA significantly inhibited ACh-induced calcium influx in the presence of an α7 positive allosteric modulator, PNU-120596 (PNU). However, αCtx-AtIA did not display any activity in the absence of PNU. These findings were further validated using two-electrode voltage clamp electrophysiology performed on oocytes overexpressing mouse α3β4, α6/α3β4 and α7 nAChRs subtypes. We observed that αCtx-AtIA displayed no or low potency in blocking α3β4 and α6/α3β4 receptors, respectively, but improved potency and selectivity to block α7 nAChRs when compared with αCtx-PeIA. Through the synthesis of two additional analogs of αCtx-AtIA and subsequent characterization using Constellation Pharmacology, we were able to identify residue Trp18 as a major contributor to the activity of the peptide.
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    Genomics and metabolomics-based assessment of the biosynthetic potential of the sponge-associated microorganism Streptomyces cacaoi strain R2A-843A from the Philippines
    Malto, Zabrina Bernice L.; Reyes, Joeriggo M.; Lo, Bernard Isaiah; Davis, Kevin Bossie S.; Concepcion, Gisela; Salvador-Reyes, Lilibeth A. (Philippine-American Academy of Science and Engineering, 2023-10-20)
    The biosynthetic machinery of the sponge-associated Streptomyces cacaoi strain R2A-843A was assessed using a combined genomics and metabolomics approach. Whole genome sequencing and molecular networking showed the high biosynthetic potential of this actinomycete. A significant proportion of the genome is dedicated to secondary metabolite production, with biosynthetic gene clusters for nonribosomal peptides, polyketides, and terpenes being the most represented. Seven cyclic pentapeptides, including a putative new analogue, and a glycosylated lanthipeptide were identified using HRMS and untargeted MS/MS analysis. To validate our genome and metabolome analysis, we undertook a mass spectrometry-guided purification and confirmed the production of the known peptides BE-18257A (1) and BE-18257B (2). The production of 1 and 2 and the growth of the microorganism were monitored for eight days. Compound 2 was produced at a higher concentration, starting at 48 h post-incubation. Both compounds were noncytotoxic against colorectal and breast cancer cell lines.
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    Physicochemical and biochemical characterization of collagen from Stichopus cf. horrens tissues for use as stimuli-responsive thin films
    Sisican, Kim Marie D.; Torreno, Vicenzo Paolo M.; Yu, Eizadora T.; Conato, Marlon T. (American Chemical Society, 2023-09-20)
    The mutable collagenous tissue (MCT) of sea cucumber, with its ability to rapidly change its stiffness and extensibility in response to different environmental stress conditions, serves as inspiration for the design of new smart functional biomaterials. Collagen, extracted from the body wall of Stichopus cf. horrens, a species commonly found in the Philippines, was characterized for its suitability as stimuli-responsive films. Protein BLAST search showed the presence of sequences commonly found in type VII and IX collagen, suggesting that Stichopus horrens collagen is heterotypic. The maximum transition temperature recorded was 56.0 ± 2 °C, which is higher than those of other known sources of marine collagen. This suggests that S. horrens collagen has better thermal stability and durability. Collagen-based thin films were then prepared, and atomic force microscopy (AFM) imaging showed the visible collagen network comprising the films. The thin films were subjected to thermomechanical analysis with degradation starting at >175 °C. At 100–150 °C, the collagen-based films apparently lose their translucency due to the removal of moisture. Upon exposure to ambient temperature, instead of degrading, the films were able to revert to the original state due to the readsorption of moisture. This study is a demonstration of a smart biomaterial developed from S. cf. horrens collagen with potential applications in food, pharmaceutical, biomedical, and other collagen-based research.