{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,28]],"date-time":"2026-09-28T20:24:44Z","timestamp":1790627084937,"version":"4.1.0"},"reference-count":41,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2025,1,13]],"date-time":"2025-01-13T00:00:00Z","timestamp":1736726400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Chapman University School of Pharmacy"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Antibiotics"],"abstract":"<jats:p>Background. We have previously reported peptides composed of sequential arginine (R) residues paired with tryptophan (W) or 3,3-diphenyl-L-alanine residues (Dip), such as cyclic peptides [R4W4] and [R4(Dip)3], as antibacterial agents. Results. Herein, we report antibacterial and antifungal activities of five linear peptides, namely ((DipR)4(WR)), ((DipR)3(WR)2), ((DipR)2(WR)3), ((DipR)(WR)4), and (DipR)4R, and five cyclic peptides [(DipR)4(WR)], [(DipR)3(WR)2], [(DipR)2(WR)3], [(DipR)(WR)4], and [DipR]5, containing alternate positively charged R and hydrophobic W and Dip residues against fungal, Gram-positive, and Gram-negative bacterial pathogens. The minimum inhibitory concentrations (MICs) of all peptides were determined by the micro-broth dilution method against Methicillin-Resistant Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Enterococcus faecium, Enterococcus faecalis, Streptococcus pneumoniae, and Bacillus subtilis. Fungal organisms were Candida albicans, Candida parapsilosis, and Aspergillus fumigatus. [DipR]5 and ((DipR)2(WR)3) showed MIC values of 0.39\u201325 \u00b5M and 0.78\u201312.5 \u00b5M against Gram-positive and Gram-negative bacteria strains, respectively. The highest activity was observed against S. pneumoniae with MIC values of 0.39\u20130.78 \u00b5M among tested compounds. [DipR]5 demonstrated MIC values of 6.6 \u00b5M against C. parapsilosis and 1.6 \u00b5M against A. fumigatus, whereas fluconazole showed MIC values of 3.3 \u00b5M and &gt;209 \u00b5M, respectively. Conclusions. These findings highlight the potential of these peptides as broad-spectrum antimicrobial agents.<\/jats:p>","DOI":"10.3390\/antibiotics14010082","type":"journal-article","created":{"date-parts":[[2025,1,13]],"date-time":"2025-01-13T11:31:31Z","timestamp":1736767891000},"page":"82","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":8,"title":["Antibacterial and Antifungal Activities of Linear and Cyclic Peptides Containing Arginine, Tryptophan, and Diphenylalanine"],"prefix":"10.3390","volume":"14","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-1933-0179","authenticated-orcid":false,"given":"David","family":"Salehi","sequence":"first","affiliation":[{"name":"Center for Targeted Drug Delivery, Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Harry and Diane Rinker Health Science Campus, Irvine, CA 92618, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0988-014X","authenticated-orcid":false,"given":"Eman H. M.","family":"Mohammed","sequence":"additional","affiliation":[{"name":"Center for Targeted Drug Delivery, Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Harry and Diane Rinker Health Science Campus, Irvine, CA 92618, USA"},{"name":"Chemistry Department, Faculty of Science, Menoufia University, Shebin El-Koam 51132, Egypt"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Naiera M.","family":"Helmy","sequence":"additional","affiliation":[{"name":"Center for Targeted Drug Delivery, Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Harry and Diane Rinker Health Science Campus, Irvine, CA 92618, USA"},{"name":"Microbial Biotechnology Department, Biotechnology Research Institute, National Research Centre, Giza 12622, Egypt"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8600-0893","authenticated-orcid":false,"given":"Keykavous","family":"Parang","sequence":"additional","affiliation":[{"name":"Center for Targeted Drug Delivery, Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Harry and Diane Rinker Health Science Campus, Irvine, CA 92618, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,1,13]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Raphael, E., and Riley, L.W. 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