An in vitro model to investigate the interactions between antimicrobial peptides and the outer membrane of gram-negative pathogens

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dc.contributor.authorHan, MLen_AU
dc.contributor.authorShen, HHen_AU
dc.contributor.authorZhu, Yen_AU
dc.contributor.authorLe Brun, APen_AU
dc.contributor.authorHolt, SAen_AU
dc.contributor.authorRoberts, Ken_AU
dc.contributor.authorSong, JNen_AU
dc.contributor.authorCooper, MAen_AU
dc.contributor.authorMoskowitz, SMen_AU
dc.contributor.authorVelkov, Ten_AU
dc.contributor.authorLi, Jen_AU
dc.date.accessioned2021-10-26T23:18:02Zen_AU
dc.date.available2021-10-26T23:18:02Zen_AU
dc.date.issued2016-11-29en_AU
dc.date.statistics2021-09-12en_AU
dc.description.abstractIncreasing antibiotic resistance in Gram-negative bacteria led to polymyxins as the last therapy. Polymyxins present their antimicrobial activity through an initial electronical interaction with lipid A in the outer membrane (OM) of GNB, and the most common mechanism of polymyxin resistance is through modifications of lipid A with positively charged groups, such as 4-amino-L-arabinose (L-Aar4N) or phosphoethanolamine (pEtN). However, it is notable that Gram-negative bacteria employ a combination of charge-charge repulsion mechanism and the modification to fatty acyl chains of lipid A to obtain high-level polymyxin resistance. Hence, we designed hydrophobic polymyxin-related lipopeptides in order to overcome modified lipid A to insert into the outer membrane of Gram-negative bacteria. In this study, we employed neutron reflectometry (NR) study to investigate the interactions between lipid A and polymyxins. Lipid A was extracted from polymyxin-susceptible and -resistant pseudomonas aeruginosa strains, and analysed using ESI-MS in the negative ion mode. The asymmetric lipid A: deuterated DPPC bilayers were deposited on SiO2 surfaces by combined Langmuir-Blodgett and Langmuir-Schaefer disposition methods, and characterised by neutron reflectometer. Our results showed L-Ara4N modified lipid A was observed in polymyxin-resistant PAKpmrB6 strain, but not in the wild-type PAK strain. The NR data obtained from unmodified lipid A: DPPC bilayer was fitted into a five-layer model. Whereas, a six-layer model containing an extra outer headgroup was established for L-Ara4N modified lipid A: d-DPPC bilayer. Our results showed a dense of PMB (volume fraction of >20%) bound to the surface of both unmodified and modified lipid A: DPPC bilayers. While it is notable that the significant changes in NR profiles obtained from H2O contrast indicated about 15.8% and 6.1% of PMB penetrated into the wild-type lipid A headgroup and fatty acyl chains, respectively, but without penetration into L-Ara4N-lipid A: d-DPPC bilayer. However, the employment of octpeptin A3 induced higher hydrophobic interactions with L-Ara4N-lipid A: d-DPPC bilayer. Our study provides an in vitro model to investigate the interactions of polymyxins with OM bilayers in GNB, and confirmed that lipid A modification with L-Ara4N was certainly to reduce the penetration of PMB into bacterial membranes. Remarkably, the higher binding affinity between octapeptin A3 and L-Ara4N modified lipid A indicated its potential to be the new generation antibiotics for the therapy of infections caused by multi-drug resistant Gram negative bacteria.en_AU
dc.identifier.citationHan, M.-L., Shen, H.-H., Zhu, Y., Le Brun, A. P., Holt, S. A., Roberts, K., Song, J.-N., Cooper, M. A., Moskowitz, S. M., Velkov, T., & Li, J. (2016). An in vitro model to investigate the interactions between antimicrobial peptides and the outer membrane of gram-negative pathogens. Paper presented at 13th AINSE-ANBUG Neutron Scattering Symposium, Sydney, NSW, Australia, 29-30 November 2016.en_AU
dc.identifier.conferenceenddate30 November 2016en_AU
dc.identifier.conferencename13th AINSE-ANBUG Neutron Scattering Symposiumen_AU
dc.identifier.conferenceplaceSydney, NSW, Australiaen_AU
dc.identifier.conferencestartdate29 November 2016en_AU
dc.identifier.urihttps://apo.ansto.gov.au/dspace/handle/10238/12113en_AU
dc.language.isoenen_AU
dc.publisherAustralian Institute of Nuclear Science and Engineeringen_AU
dc.subjectAntibioticsen_AU
dc.subjectBacteriaen_AU
dc.subjectAntimicrobial agentsen_AU
dc.subjectLipidsen_AU
dc.subjectPeptidesen_AU
dc.subjectDrugsen_AU
dc.titleAn in vitro model to investigate the interactions between antimicrobial peptides and the outer membrane of gram-negative pathogensen_AU
dc.typeConference Abstracten_AU
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