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  1. 1. DPPA research By Gefei Wang
  2. 2. 2 Foil cover of waste liquid beaker: One of the major liquid used in lab is ethanol, which is volatile and inflammable. So it is important to cover the beaker to prevent ethanol gas from flowing out. And when you find the foil has holes or cannot cover the beaker, please make a new cover, it only takes 1min . Lab safety
  3. 3. 3 Aspirator: When aspirator fall on the floor, its tip may touch the dirt on the floor. And the contaminated tip will affect the experiment results. Once you finish using aspirator, please put it to clean area, like the top of the black box, or the board.
  4. 4. 4 1,Work in the lab under instruction of Ting 2,Learn basic knowledge about surface lipid interaction 3,Practice technique of measuring surface pressure What I do this semester
  5. 5. 5 WHAT I’VE LEARNED…
  6. 6. 6 Introduction Aerosols play an important role in climate change, so it is necessary to understand the its property and behavior. The majority of aerosols come from ocean, and ocean surface is covered by SSML which affect the formation of aerosols and interact with the aerosol surface. To study aerosol surface, DPPA is selected as model system.
  7. 7. 7 DPPA (dipalmitoyl-phosphatidic acid): -has two 16 C chains -strong intermolecular force -contains phosphate group Model system DPPA
  8. 8. 8 Why DPPA? First • SSML contain plenty of fatty acid, and the most abundant is C16 fatty acid, palmitic acid(PA) • PA is component of DPPA Second • DPPA itself is intermediate phospholipid • Study DPPA held understand more complex lipid molecule Third • DPPA contains no moieties on its phosphate • So it is simple and easy to study
  9. 9. 9 Instrument Langmuir trough: used to compress monolayers of molecules on the surface of a given sub phase (usually water), During compressing, density of the monolayer changes. This results in surface pressure change, which can be sensed by the tensiometer. Lab technique
  10. 10. 10 Method: Langmuir-Wilhelmy balance (LWB) -Used to measure the surface tension -the compression of barrier changes the distance between molecule in monolayer -so the surface pressure change, and is detect by Wilhelmy plate. 𝜋 = 𝛾 𝑤 − 𝛾𝑠 Surface tension of subphase Surface tension of subphase with monolayer
  11. 11. 11 𝜋 = 𝛾 𝑤 − 𝛾𝑠 𝜋 = − 𝐹 2(𝑇+𝑊)𝑐𝑜𝑠(𝜃) =-- 𝑚𝑔 2𝑊 net force -F width -W, and thickness-T, the contact angle-θ Assume plate is thin enough, and is completely wetted to ensure a contact angle of 0°, so cos (0°) = 1
  12. 12. 12 Surface tension: the surface tension of a liquid results from cohesive forces between surface molecules. Surface tension is an intensive property. Surface pressure: the difference between surface tension of different substance. Surface pressure is an extensive property. BASIC KNOWLEDGE
  13. 13. 13 Spreading: Spread the solution of surfactant molecule on surface of sub phase dropwise. Procedure: 1,Clean the trough with deionized water three times 2, Soak the filer paper 3, Clean the barriers with water and ethanol 4, Fill the trough with water and place barriers on trough and hang the paper on hook 5, Test the degree of clean of the trough(<0.1) 6, If trough is clean, calculate the amount of solution of molecule of interest needed 7, Spread the molecule dropwise 8, After all of solvent vaporize, the barriers begin compressing 9, When compression stop, collect data from computer Skill and procedure
  14. 14. 14 Two dimensional phase change Gaseous phase • molecules in a Langmuir monolayers are very far apart, little intermolecular force. Liquid phase • closer and stronger lateral interaction • the liquid-expanded (LE) and liquid-condensed (LC) phase. • In LE transition, the isotherms display a considerable curvature at liftoff from = 0 mN/m. • During LC phase, the compressibility of monolayer decreases, and the interaction between tail part of molecule increases. Solid phase • Headgroups of molecule are dehydrate, tail parts are tightly packed. Strong intermolecular interaction. Collapse Phase At this point, monolayer cannot be compressed, and further compression will disrupt the film.
  15. 15. 15 Collapse phase
  16. 16. 16 trans-DPPA cis-DPPA with guache between hydrogen and alkyl group, and between alkyl group
  17. 17. 17 Experiment data
  18. 18. 18 Early data
  19. 19. 19
  20. 20. 20 DPPA data
  21. 21. 21 DPPA on salt sub phase Data obtained:3/22/2016
  22. 22. 22 Future work -Practice spreading DPPA on salt water to get reproducible data -Test the DPPA on salt solution with different concentration -Study DPPA behavior under different pH environment
  23. 23. 23 Reference Langmuir. Digital image. Surface Pressure/molecular Area Isotherms Measured by the Langmuir Method – a Nanoscience Approach to Study Films at the Water-air Interface. Web. <http://nano.uib.no/Langmuir.php> Notter, Robert H. Lung Surfactants: Basic Science and Clinical Applications. New York: Marcel Dekker, 2000. Print. DPPA - Structural Formula Illustration. Digital image. Web. <http://www.rxlist.com/definity-drug.htm>.

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