Membranes dynamic measurements

Schneckenburger, H., Wagner, M., Kretzschmar, M., Strauss, W. S. and Sailer, R. (2004b). Laser-assisted fluorescence microscopy for measuring cell membrane dynamics. Photochem. Photobiol. Sci. 3, 817-22. 

In order to determine the thermal time constant of the microhotplate in dynamic measurements, a square-shape voltage pulse was applied to the heater. The pulse frequency was 5 Hz for uncoated and 2.5 Hz for coated membranes. The amplitude of the pulse was adjusted to produce a temperature rise of 50 °C. The temperature sensor was fed from a constant-current source, and the voltage drop across the temperature sensor was amplified with an operational amplifier. The dynamic response of the temperature sensor was recorded by an oscilloscope. The thermal time constant was calculated from these data with a curve fit using Eq. (3.29). As already mentioned in the context of Eq. (3.37), self-heating occurs with a resistive heater, so that the thermal time constant has to be determined during the cooHng cycle. 

Szollosi, J., Damjanovich, S., Mulhem, S. A., and Tron, L. (1987) Fluorescence energy transfer and membrane potential measurements monitor dynamic properties of cell membranes a critical review. Prog. Biophys. Mol. Biol. 49, 65-87. 

The dynamics of proton binding to the extra cellular and the cytoplasmic surfaces of the purple membranes were measured by the pH jump methods [125], The purple membranes selectively labeled by fluorescein Lys-129 of bacteri-orhodopsin were pulsed by protons released in the aqueous bulk from excited pyranine and the reaction of the protons with the indicators was measured. Kinetic analysis of the data implied that the two faces of the membrane differ in then-buffer capacities and in their rates of interaction with bulk protons. The extracellular surfaces of the purple membrane contains one anionic proton binding site per protein molecule with pA" 5.1. This site is within a Coulomb cage radius from Lys-129. The cytoplasmic surface of the purple membrane bears four to five pro-tonable moieties that, due to close proximity, function as a common proton binding site. The reaction of the proton with this cluster is at a very fast rate (3 X 1010 M-1 sec ). The proximity between the elements is sufficiently high that even in 100 mM NaCl, they still function as a cluster. Extraction of the chromophore retinal from the protein has a marked effect on the carboxylates of the cytoplasmic surface, and two to three of them assume positions that almost bar their reaction with bulk protons. Quantitative evaluation of the dynamics of proton transfer from photoactivated bacteriorhodopsin to the bulk has been done by using numerical... 

Frojmovic MM, Wong T, van de Ven T. Dynamic measurements of the platelet membrane glycoprotrin... 

Figure 5. Time-resolved fluorescence of pyranine at the wavelength of maximum

TRES have been extensively used to study membrane dynamics. While not intuitively obvious, FD data can also be used to detennine TRES. This is shown for Patman-labeled DPFC vesicles in Hgure 7.9. Patman is also a Plodan derivative, in this case desipied to bind to membranes (Chapter 6, Hgure 6.27). As fiir the ID measate-meots, the ID data ate measured for various wavelengths across the emission spectrum. In Hguie 7 S, the phase and... 

Pauls KP, MacKay AL, Soderman O, Bloom M, Taneja AK, Hodges RS (1985) Dynamic properties of the backbone of an integral membrane polypeptide measured by H-NMR. Eur Biophys J 12(1) 1 11... 

An ionometric system for the analysis of electrolyte solutions has been developed Planar chip structures of ion sensitive field effect tansistors (ISFET s) and ion selective electrodes (ISE s) are used as sensors Their layout allows an easy preparation of the ion sensitive membrane and also a very simple electrical contacting The sensor chips can be clipped to small volume flow-through cells for dynamic measurements An advanced electronic device was developed for measuring both, the ISFET and the ISE signals This system is usefial for basic investigations of ion sensitive materials and can be integrated comfortably into electroanalytical sensor/actuator microsystems... 

Characterization of membranes used in filtration processes (microfiltration, ultrafiltration, nanofiltration, reverse osmosis) is usually carried out by hydro-dynamic measurements (hydraulic permeability, retention) [5-10], but electrical measurements such as streaming potential (SP or electroosmotic flow) and membrane potential (MP) are used for characterizing, respectively, the mem-brane/solution interface (zeta potential, surface charge density) and the effective membrane fixed charge and ion transport numbers in the membrane [11-27]. Moreover, great and rapid development of membranes for fuel cells... 

Overviews of experimental methods in optical spectroscopy and microscopy have recently been given [17,47]. Applications of these methods have been concentrated on mitochondrial energy metabolism [8,9,45], cell membrane dynamics [48], as well as studies on cellular location and photodynamic efficacy of photosensitzers [49]. A main topic in view of in vitro diagnostics, pharmacology and cell aging includes measurements of membrane parameters as a function of temperature and cholesterol [50]. Those membrane parameters may also play a key role in laser assisted optoporation, a method which has been developed and optimized [51] in view of an increased cellular uptake of molecules or small beads, as used e.g. for cell transfection. 

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