Vertical ordering sensitivity of solid supported DPPC membrane to alamethicin and the related loss of cell viability

Background: Experimental studies of antimicrobial peptides interacting with lipid membranes recently attracted growing interest due to their numerous biomedical applications. However, the in fl uence of such peptides on the structural organisation of lipid membranes in connection with the actual cell response still remains an elusive issue. Methods: X-ray diffraction was employed on detecting the sensitivity of the periodical spacing of dipalmitoyl- phosphatidyl-choline stacked as solid-supported bilayers to the presence of varying amounts of the peptide alamethicin in a wide range of peptide-to-lipid molar ratios. These results were then correlated with the effects of alamethicinon biological membranes in vitro asobservedby optical microscopy and microculture tetrazolium assay on the tumour cells HeLa to provide a comprehensive and quantitative analysis of these effects, based on a dose – response relationship. Results: The experiments allowed correlating the periodical spacing and th

Background: Experimental studies of antimicrobial peptides interacting with lipid membranes recently attracted growing interest due to their numerous biomedical applications. However, the in fl uence of such peptides on the structural organisation of lipid membranes in connection with the actual cell response still remains an elusive issue. Methods: X-ray diffraction was employed on detecting the sensitivity of the periodical spacing of dipalmitoyl- phosphatidyl-choline stacked as solid-supported bilayers to the presence of varying amounts of the peptide alamethicin in a wide range of peptide-to-lipid molar ratios. These results were then correlated with the effects of alamethicinon biological membranes in vitro asobservedby optical microscopy and microculture tetrazolium assay on the tumour cells HeLa to provide a comprehensive and quantitative analysis of these effects, based on a dose – response relationship. Results: The experiments allowed correlating the periodical spacing and the peptide-to-lipid molar ratio on alamethicin-dipalmitoyl-phosphatidyl-choline samples. Two different trends of periodical spacing vs .peptide- to-lipidmolarratioclearlyappearedatlowandhighhydrationlevels,showingintriguingnon-linearpro fi les.Un- expected correspondences were observed between the peptide-to-lipid molar ratio range where the changes in dipalmitoyl-phosphatidyl-choline structure occur and the alamethicin doses which alter the viability and the plasma membrane morphology of HeLa . Conclusions: Alamethicin might induceeither mechanical orphasechanges on dipalmitoyl-phosphatidyl-choline bilayers. Such easily accessible ordering information was well-calibrated to predict the alamethicin doses neces- sary to trigger cell death through plasma membrane alterations. General signi fi cance: This benchmark combined study may be valuable to predict bioeffects of several antimicro- bial peptides of biomedical relevance