Giant pores

Ferey G, Serre C, Mellot-Draznieks C, Millange F, Surble S, Dutour J, Margiolaki I. A hybrid solid with giant pores prepared by a combination of targeted chemistry, simulation, and powder diffraction, Angew. Chem. Int. Ed. 2004, 43, 6296-6301. 

Vimont A, Goupil J-M, Lavalley J-C, Daturi M, Surble S, Serre C, Millange F, Ferey, G, Audebrand N. Investigation of acid sites in a zeotypic giant pores chromium(lll) carboxylate, J. Am. Chem. Soc. 2006, 128, 3218-3227. 

Ferey G Mellot-Draznjeks C Serre C Millange F, Crystallized frameworks with giant pores Are there limits to the possible , Acc. Chem. Res., 2005, 38, 217-225. 

Supramolecular chemists without BLM-workstation can approximate the inner diameter of synthetic ion channels and pores by size exclusion experiments in LUVs. Differences in activity between the HPTS assay - compatible with all diameters - and the ANTS/DPX assay reserved for pores with diameter larger than 5 A and the CF assay for pores with larger than 10A can differentiate between ion channels and pores (Fig. 11.5). Larger fluorescent probes like CF-dextrans are available to identify giant pores or defects [26]. However, we caution... 

Sonnauer A, Hoffmann F, Frdba M, Kienle L, Duppel V, Thommes M, et al. Giant pores in a chromium naphthalene-2,6-dicarboxylate open-framework structure with MIL-101 topology. Angew Chem Int Ed 2009 48 3791-4. 

There has been extensive recent use of track-etched membranes as templates. As will be discussed in detail below, these membranes are ideal for producing parallel arrays of metal nanowires or nanotubules. This is usually done via electroless metal deposition [25], but many metals have also been deposited electrochemically [26]. For example, several groups have used track-etched templates for deposition of nanowires and segmented nanowires, which they then examined for giant magnetoresistance [27-29]. Other materials templated in the pores of track etch membranes include conducting polymers [30] and polymer-metal composites [31]. 

During the fusion process the relative surface area decreases with increasing volume indicating a loss of membrane material (about 22% in Fig. 51). In analogy to the fusion process of protoplasts it can be assumed that the excess lipid is removed in form of small, submicroscopic vesicles (Fig. 52). The electric breakdown in the membrane contact zone leads to the formation of several pores in which lipid molecules are randomly oriented (Fig. 52 b). The molecules reorient forming submicroscopic vesicles and the new membrane of the fused vesicle (Fig. 52c). Thus, fused giant liposomes should contain small, submicroscopic vesicles. This could possibly be proven by using fluorescence-labelled lipids for liposome fusion. 

Fig. 52a-c. Scheme of the fusion process of giant liposomes and the formation of small unilamellar vesicles (SUV) at the interface, a) lipid bilayers in contact b) pores generated by electric breakdown and lipid reorientation forming SUVs c) reconstitution of lipid membranes formation of a fused giant liposome and SUVs . 

It is also possible to electrodeposit multilayers in cylindrical pores of a suitable etched polymer membrane. Typically, wires with diameters of about 100 nm and length of 5-10 fim can be obtained. The deposition cycles are similar to the ones described above. Magnetoresistance [this is a term describing the relative decrease (increase) in electrical resistance of a material when subjected to a magnetic field longitudinally (transversely) to the current flow] measurements with the current perpendicular to the planes are possible. In addition, giant magnetoresistance (GMR defined below) effects may be observed as well. 

DGM visualises the porous medium as a collection of giant spherical molecules (dust particles) kept in space by external force. The movement of gas molecules in the space between dust particles is described by the kinetic theory of gases. Formally, the MTPM transport parameters and qr can be used also in DGM. The third DGM transport parameter characterises the viscous (Poiseuille) gas flow in pores. 

As discussed in Section 7.2, strong electric pulses applied to single-component giant vesicles made of zwitterionic lipids like PCs induce the formahon of pores, which reseal within tens of milliseconds. When negatively charged lipids, like phosphatidylglycerol (PC) or phosphatidylserine, are present in a membrane a very different response of the vesicles can be observed, partially influenced by the medium conditions [142]. 

Zhelev, D.V. and Needham, D. (1993) Tension-stabilized pores in giant vesicles-determination of pore-size and pore line tension. Biochimica et Biophysica Acta, 1147 (1), 89-104. 

Rodriguez, N., Cribier, S., and Pincet, F. (2006) Transition from long- to short-lived transient pores in giant vesicles in an aqueous medium. Physical Review E, 74 (6), 061902. 

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