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@INPROCEEDINGS{Shen:398542,
      author       = {Shen, Chen and de la Serna, Jorge and Struth, Bernd and
                      Kloesgen, Beate},
      title        = {{T}he additional phase transition of {DPPC} monolayers at
                      high surface pressure confirmed by {GIXD} study},
      reportid     = {PUBDB-2017-14112},
      year         = {2016},
      note         = {The poster won the "Best Poster Award - Second Place" at
                      the conference.},
      abstract     = {Pulmonary surfactant forms the alveolar monolayer at the
                      air/aqueous interface within the lung. During the breathing
                      process, the surface pressure periodically varies from
                      ~40mN/m up to ~70mN/m. The film is mechanically stable
                      during this rapid and reversible expansion. The monolayer
                      consists of $~90\%$ of lipid with $10\%$ integrated
                      proteins. Among its lipid compounds, di-
                      palmitoyl-phosphatidylcholine (DPPC) dominates $(~45wt\%).$
                      No other lipid but DPPC was so far reported to be
                      compressible to very high surface pressure (~70mN/m [1])
                      before its monolayer collapsed. Its
                      liquid-expanded/liquid-condensed (LE/LC) phase transition at
                      ~10mN/m is well known [2].Here we present results from
                      Langmuir isotherm measurements that evidence a so far not
                      documented second phase transition at elevated surface
                      pressure Π (~50mN/m). The varying lateral structures of the
                      monolayer at 8mN/m, 20mN/m, 30mN/m, 40mN/m, 50mN/m, 60mN/m,
                      70mN/m were investigated by grazing incidence X-ray
                      diffraction (GIXD). The results report on the 2D packing
                      lattice with the inter-chain distance dxy. Moreover, the
                      tilt angle of the palmitoyl chains was calculated combining
                      the lattice parameters and the geometrical boundary
                      conditions. The course of the inter-chain distance versus
                      surface pressure exhibits three regimes, separated by the
                      LE/LC transition and the second phase transition at the
                      higher pressure. This feature may assign a functional task
                      to DPPC in the lung surfactant since it contributes to the
                      mechanical stability of the alveolae monolayer and at the
                      same time allows reduction of the interfacial tension to
                      ~0mN/m.References:[1] G. Ma and H. C. Allen, Langmuir 22
                      (12), 5341 (2006).[2] K. Y. C. Lee, A. Gopal, A. von Nahmen,
                      J. A. Zasadzinski, J. Majewski, G. S. Smith, P. B. Howes,
                      and K. Kjaer, Journal of Chemical Physics 116 (2), 774
                      (2002).},
      month         = {Jun},
      date          = {2016-06-15},
      organization  = {5th Iberian Biophysics Congress, Porto
                       (Portugal), 15 Jun 2016 - 17 Jun 2016},
      cin          = {DOOR / FS-DO},
      cid          = {I:(DE-H253)HAS-User-20120731 / I:(DE-H253)FS-DO-20120731},
      pnm          = {6215 - Soft Matter, Health and Life Sciences (POF3-621)},
      pid          = {G:(DE-HGF)POF3-6215},
      experiment   = {EXP:(DE-H253)D-BW1-20150101},
      typ          = {PUB:(DE-HGF)24},
      doi          = {10.3204/PUBDB-2017-14112},
      url          = {https://bib-pubdb1.desy.de/record/398542},
}