Bio-membranes of the natural living cells are made of bilayers of phospholipids molecules embedded with other constituents, such as cholesterol and membrane proteins, which help to accomplish a broad range of functions. Vesicles made of lipid bilayers can serve as good model systems for bio-membranes. Therefore these systems have been extensively characterized and much is known about their shape, size, porosity and functionality. In this dissertation we report the studies of the effects of the phosoholipid conformation, such as hydrocarbon number and presence of double bond in hydrophobic tails on dynamics of phospholipids bilayers studied by neutron spin echo (NSE) technique. We have investigated how lidocaine, the most medically used local anesthetics (LA), influence the structural and dynamical properties of model bio-membranes by small angle neutron scattering (SANS), NSE and differential scanning calorimetry (DSC).
To investigate the influence of phospholipid conformation on bio-membranes, the bending elasticities κc of seven saturated and monounsaturated phospholipid bilayers were investigated by NSE spectroscopy. κ c of phosphatidylcholines (PCS) in liquid crystalline (L α) phase ranges from 0.38×10-19 J for 1,2-Dimyristoyl- sn-Glycero-3-Phosphocholine (14:0 PC) to 0.64×10-19 J for 1,2-Dieicosenoyl-sn-Glycero-3-Phosphocholine (20:1 PC). It was confirmed that when the area modulus KA varies little with chain unsaturation or length, the elastic ratios (κc/ KA)1/2 of bilayers varies linearly with lipid hydrophobic thickness d.
For the study of the influence of LA on bio-membranes, SANS measurements have been performed on 14:0 PC bilayers with different concentrations of lidocaine to determine the bilayer thickness dL as a function of the lidocaine concentration. NSE has been used to study the influence of lidocaine on the bending elasticity of 14:0 PC bilayers in Lα and ripple gel (Pβ') phases. Our results confirmed that the molecules of lidocaine loosen the packing of the membrane constituent lipids and induce lateral membrane expansion. The intercalation of lodocaine molecules provides more inter-molecular space for the lipid hydrophobic chains and results in a decrease of the bilayer thickness, a decrease of the main transition temperature from Lα to Pβ' phase and a doubling of the bending elasticity in Lα phase.
|Advisor:||Bossev, Dobrin P.|
|Commitee:||Baxter, David V., Setayeshgar, Sima, Snow, Michael W.|
|School Location:||United States -- Indiana|
|Source:||DAI-B 70/12, Dissertation Abstracts International|
|Subjects:||Condensed matter physics|
|Keywords:||Bending elasticity, Biomembranes, Lidocaine, Local anesthetics, Neutron spin echo, Phospholipid bilayers|
Copyright in each Dissertation and Thesis is retained by the author. All Rights Reserved
The supplemental file or files you are about to download were provided to ProQuest by the author as part of a
dissertation or thesis. The supplemental files are provided "AS IS" without warranty. ProQuest is not responsible for the
content, format or impact on the supplemental file(s) on our system. in some cases, the file type may be unknown or
may be a .exe file. We recommend caution as you open such files.
Copyright of the original materials contained in the supplemental file is retained by the author and your access to the
supplemental files is subject to the ProQuest Terms and Conditions of use.
Depending on the size of the file(s) you are downloading, the system may take some time to download them. Please be