Investigating the structure of self assembled monolayers related to biological cell membranes

Author: Ahlam Rayan M Alharbi

Alharbi, Ahlam Rayan M, 2017 Investigating the structure of self assembled monolayers related to biological cell membranes, Flinders University, College of Science and Engineering

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Tethered bilayer lipid membranes (tBLMs) are solid supported membranes, where the solid supported substrate is separated from the artificial lipid bilayer by an anchorlipid such as 2, 3-di-O-phytanyl-glycerol-1-tetraethylene glycol-D,L-lipoic acid ester lipid (DPTL or DPhyTL). Tethered bilayer lipid membranes are based on self-assembled monolayers (SAMs) of anchorlipids. The chemical structure of the tether-segment of the anchorlipids has a significant effect on the properties of the artificial Tethered bilayer lipid membranes such as its fluidity. Therefore, this study focuses on examining the thickness, elemental composition and orientation of DPTL SAMs as well as SAMs of a dilution of 0.16 mg/ml of DPTL with 0.04 mg/ml of mercaptoethanol (ME). The length measurements of the SAMs were obtained from applying neutral impact collision ion scattering spectroscopy (NICISS). The estimated length of the DPTL SAMs was 3.9 nm whereas the estimated thickness of the diluted SAMs of DPTL was 1 nm. X-ray photoelectron spectroscopy (XPS) was applied to the investigated SAMs in order to determine their elemental composition and chemical state of elements. Both SAMs of DPTL and a diluted DPTL composed of four core elements as appeared from XPS measurements Gold4f, Oxygen1s, Carbon1s and Sulphur2p with different relative intensities of elements. The orientation of the molecules forming the monolayer has been examined by means of metastable induced electron spectroscopy (MIES). DPTL SAMs are standing up in a very oriented way and a methyl group are dominating the surface whereas the diluted DPTL SAMs are lying flat and a methylene group are dominating the surface. Additionally, in this study, a case study of two types of SAMs of organic films 11-Mercaptoundecanoic acid (11-MUA) & 1-Dodecanethiol (DDT) have been structurally examined by means of NICISS, XPS and MIES. The investigation of the organic films have been performed due to their simple structure. The SAMs of 11-MUA and DDT have been investigated as preliminary study before analysing the structure of the SAMs formed by the anchorlipids.

Keywords: anchorlipids,self-assembled monolayers, DPTL,mercaptoethanol,cell membranes

Subject: Nanotechnology thesis

Thesis type: Masters
Completed: 2017
School: College of Science and Engineering
Supervisor: Gunther Andersson