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# Experimental Characterization

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• AFM on Membranes
Atomic force microscopy (AFM) is a technique with multiple applications in biology. This method is a member of the broad family of scanning probe microscopy and was initially developed in 1986 by Binnig et al to overcome the disadvantages of the scanning tunneling microscopy (STM).
• Electrospray Ionization (ESI) Mass Spectrometry
• Fluorescence on Membranes
The study of membranes poses a unique challenge in science due to their complex and fluid nature. Until recently, the majority of experiments was conducted in either fixed samples or on population levels that did not give insight into individual events. However, recent advances in fluorescence microscopy techniques have allowed scientists to visualize microscopic perturbations of individual vesicles and have allowed the study of membrane dynamics at higher spatiotemporal resolution than before.
• FTIR on Membranes
Fourier Transform Infrared (FTIR) Spectroscopy is a widespread, relatively cheap technique for studying the structure of compounds through chemical bond vibrations. Since there are already pages dedicated to FTIR and Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) this page will not go into the details of the theory associated with these techniques, but will instead describe these techniques in relation to lipid membranes.
• Mass Analyzer Orbitrap
Mass spectrometry (MS) is an analytic instrument that is used to measure the mass-to-charge ratios (m/z) of samples to obtain qualitative and quantitative information. The development of MS started around 1920 where it was used to study the isotopic abundance of elements. MS capabilities have increased greatly since 1920.
• Mass Analyzer Time of Flight
• Model membranes vs. biological membranes
Model-based studies have proven to be very useful in understanding basic biophysical properties of biological membranes. They provide a foundation upon which new hypotheses can be generated and tested in living cells. A solid foundational understanding of simple synthetic membranes should allow scientists to develop experimental and computational tools to test more complex properties of biological membranes.
• Near-field scanning optical microscopy (NSOM)
Near-field scanning optical microscopy(NSOM), also called scanning near-field optical microscopy(SNOM), is a scanning probe technique that overcomes the diffraction barrier in traditional far-field optical microscopy. Conventional optical microscopy techniques are limited by the diffraction of the light and the resolution is limited to roughly 250 nm, which make it very difficult to resolve the domains or clusters in the cellular membranes.
• Raman Spectroscopy
• Single Molecule Tracking
Single Molecule Tracking (SMT), also known as Single Particle Tracking (SPT) or Single Dye Tracking (SDT), refers to a class of non-invasive techniques that involve direct spatial observation of individual molecular or particle entities as a function of time. This Wiki page offers a broad overview of the some of the working principles, technical aspects, and biophysical applications of SMT.
• SMALP Technology
Styrene maleic acid lipid particles (SMALPs) are disc-shaped lipid assemblies on the nano-scale made from the interaction of membrane bilayers and styrene maleic acid (SMA) copolymer. SMALP technology holds great potential as a biochemical tool as it allows solubilization of membrane bilayers and its embedded constituent into discs without any use of detergents. SMALPs are thought to be superior to other disc-forming techniques.
• Solid-state NMR
The ssNMR studies both isotropic and anisotropic interactions.  One can interpret the spectrum to understand interactions between nuclei and further construct the structure of condensed matter. It can be used as a powerful tool to solve membrane protein structures.
• Supported and Tethered Membranes
Model lipid bilayers or synthetic lipid bilayers are membranes that are created in vitro. In vivo studies of lipid bilayers and the proteins embedded within them can be difficult due to the complexity of the cellular dynamics of membranes. Model bilayers use biological membranes, along with artificial constraints, to investigate the structure and function of lipid bilayers. Supported and tethered membranes are two types of model bilayers frequently used in model studies.

Thumbnail: S. cerevisiae septins revealed with fluorescent microscopy utilizing fluorescent labeling. Image used with permission (Public Domain, Spitfire ch,).