title: Vertical ordering sensitivity of solid supported DPPC membrane to alamethicin and the related loss of cell viability.
abstract: BACKGROUND
  Experimental studies of antimicrobial peptides interacting with lipid membranes recently attracted growing interest due to their numerous biomedical applications. However, the influence 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 alamethicin on biological membranes in vitro as observed by 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-lipid molar ratio clearly appeared at low and high hydration levels, showing intriguing non-linear profiles. Unexpected 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 induce either mechanical or phase changes on dipalmitoyl-phosphatidyl-choline bilayers. Such easily accessible ordering information was well-calibrated to predict the alamethicin doses necessary to trigger cell death through plasma membrane alterations.
  
  
  CONCLUSIONS
  This benchmark combined study may be valuable to predict bioeffects of several antimicrobial peptides of biomedical relevance.
authors.affiliation: Dipartimento di Fisica, Università Sapienza, P.le A. Moro 5, 00185 Roma, Italy; Dipartimento di Scienze e Tecnologie Chimiche, Università di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Roma, Italy. Electronic address: fabiodomenici@gmail.com.
authors.forename: F
authors.initials: F
authors.lastname: Domenici
authors.affiliation: Dipartimento di Scienze e Tecnologie Chimiche, Università di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Roma, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Dell'Unto
authors.affiliation: Dipartimento per l'Innovazione dei sistemi Biologici, Agroalimentari e Forestali, Università degli Studi della Tuscia, Via San Camillo de Lellis s.n.c., 01100 Viterbo, Italy.
authors.forename: D
authors.initials: D
authors.lastname: Triggiani
authors.affiliation: Banca del Germoplasma della Tuscia, Università degli Studi della Tuscia, Largo dell'Università s.n.c., 01100 Viterbo, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Olmati
authors.affiliation: Dipartimento di Chimica, Università degli Studi di Milano, Via Golgi 19, 20133 Milano, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Castellano
authors.affiliation: Dipartimento di Fisica, Università Sapienza, P.le A. Moro 5, 00185 Roma, Italy; CNR-IPCF UOS Roma, Dipartimento di Fisica, Università Sapienza, P.le A. Moro 5, 00185 Roma, Italy; Center for Life Nanoscience@Sapienza, Istituto Italiano di Tecnologia, V.le Regina Elena, 291, 00185 Rome, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Bordi
authors.affiliation: Dipartimento per l'Innovazione dei sistemi Biologici, Agroalimentari e Forestali, Università degli Studi della Tuscia, Via San Camillo de Lellis s.n.c., 01100 Viterbo, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Tiezzi
authors.affiliation: Dipartimento di Fisica, Università Sapienza, P.le A. Moro 5, 00185 Roma, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Congiu
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry*; D000408:Alamethicin / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D006367:HeLa Cells; D006801:Humans; D008051:Lipid Bilayers / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D008051:Lipid Bilayers; D015060:1,2-Dipalmitoylphosphatidylcholine; D000408:Alamethicin
keywords: Alamethicin; DPPC; HeLa cell; Lipid membrane; MTT assay; X-ray diffraction