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Squeeze-out and re-uptake of pulmonary surfactant components

Abstract

Replacement surfactant therapy containing Phosphorylated and 1% weight hydrophobic surfactant proteins (SP-B and SP-C) from animal source has been proven clinically to stabilize patients with respiratory distress syndrome (RDS) due to its ability to spread rapidly and lower surface tension to near zero values at rates required to prevent lung collapse. A new generation of synthetic lung surfactant is being developed based on peptide analogs and peptoids of SP-B and SP-C to address the cost of the treatment. For the effective design of this new synthetic surfactant a detailed study must be carried-out, to address, three essential properties whose mechanism is not well understood for these surfactants. First, the squeeze-out of unsaturated or unordered structures to prevent lung collapse. Secondly, re-uptake essential for stabilizing the lung after expiration (squeeze-out). Thirdly, is the role of the hydrophobic protein SP-C during squeeze-out and re-uptake. These experiments would naturally be followed by the evaluation of several synthetic peptides and peptoid mimics proposed for the design of the synthetic surfactant. The synthetic peptides and peptoids must have similar properties to that of SP-C found to be essential in natural exogenous surfactant preparations.

We propose that SP-C enhances the rate of squeeze-out of unsaturated or unordered components to prevent lung collapse. For this, we will study model binary and ternary mixtures of phospholipid and SP-C, peptide analogs, and peptoids using IRRAS, ATR-FT-IR, PM-IRRAS, AFM, epifluorescence spectroscopies, bubble surfactometry and computational simulations.

Our aims are:

  • To simulate the squeeze-out and re-uptake process for binary and ternary mixtures of phos-pholip i ds.
  • To study via IRRAS the effect of SP-C on the squeeze-out and re-uptake of phopholipids.
  • To study via computational techniques the effect of SP-C on the squeeze-out and re-uptake of phospholipids.
  • To compare the secondary structure of SP-C with the peptide analogs using FT-IR spectroscopy.
  • To study the lipid-peptide inter-actions using ATR-FT-IR and transmission FT-IR spectroscopy.
  • To study the lipid peptide interactions at the A/W interface by IRRAS and determine if these peptides and peptoids enhance squeeze-out and re-uptake.
  • To study the surfactant film properties by several biophysical techniques.
  • To simulate the peptides at an A/W interface using the experimental results obtained.
This interdisciplinary approach towards the study of this vital substance will provide a molecular level understanding of the dynamics that occur at or near the A/W interface and explore several synthetic peptides that may be used for the design of a new exogenous surfactant.

Publications

V. Ortiz , Y. M. López-Álvarez , G. E. López.
"Phase diagrams and capillarity condensation of methane confined in single- and multi-layer nanotubes". Molecular Physics, Taylor & Francis, Volume 103, Number 19 / 10 October 2005, 2587 - 2592.

Johnny R. Maury-Evertsz,L. Antonio Estevez, and Gustavo E. Lopez.
"Effect of branching and confinement on star-branched polymeric systems". The Journal of Chemical Physics, 2004, V 121, N 17, pp. 8652-8657.

Leslie Villalobos, Yania M. López-Álvarez, Belinda Pastrana-Ríos, and Gustavo E. López
"Thermodynamics of the liquid states of Langmuir monolayers". The Journal of Chemical Physics, March 2005. 122, 104701 (2005).

Eunice Ramirez, Alberto Santana, Anthony Cruz, Ines Plasencia and Gustavo E Lopez.
"Molecular dynamics of surfactant protein C (SP-C): From single molecule to heptameric aggregates". Biophys. J. BioFAST: First Published January 27, 2006. doi:10.1529/biophys j.105.073270

V. Ortiz , G. E. López.
"Studies on the behavior of nanoconfined homopolymers with cyclic chain architecture."J. Chem. Phys. 123, 054903 (2005) (8 pages)




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