Membranes freeze fractured

Although freeze-fracture experiments have demonstrated that monomers are assembled into stable tetramers in the membranes, radiation inactivation studies and, later, expression studies revealed that each monomer is a functional water channel (Fig. lc). 

The dimer chains of Ca -ATPase can also be observed by freeze-fracture electron microscopy [119,165,166,172-174], forming regular arrays of oblique parallel ridges on the concave P fracture faces of the membrane, with complementary grooves or furrows on the convex E fracture faces. Resolution of the surface projections of individual Ca -ATPase molecules within the crystalline arrays has also been achieved on freeze-dried rotary shadowed preparations of vanadate treated rabbit sarcoplasmic reticulum [163,166,173,175]. The unit cell dimensions derived from these preparations are a = 6.5 nm b = 10.7 nm and 7 = 85.5° [175], in reasonable agreement with earlier estimates on negatively stained preparations [88]. 

BJ McLaughlin, RB Caldwell, Y Sasaki, T Wood. (1985). Freeze-fracture quantitative comparison of rabbit corneal epithelial and endothelial membranes. Curr Eye Res 4 951-961. 

Epi-illumination Subcellular imaging structures Freeze fracture Preparation of cellular ultrastructures in frozen-hydrated and living state for electron microscopy macromolecular organization of bilayer membranes... 

Subsequent to possible solubilization of membrane-bound proteins, solubilization must be verified. The criteria listed in Table 2 are relevant in assessing whether solubilization has been accomplished. To ascertain whether the solubilized protein has retained biological activity, membrane reconstitution (28) is attempted subsequent to detergent removal (24). Reconstitution is often visualized by electron microscopy employing either negative staining or freeze fracture. 

The process of infection of lupine nodule cells by Rhizobia was examined by the thin-section electron microscopic technique, as well as the freeze-fracture technique. Different membranes such as infection thread membranes, peribacterioid membranes, plasma membranes, membranes of cytoplasmic vesicles, and membranes of the Golgi bodies and ER were stained with uranium-lead, silver, phosphotungstic acid, and ZIO (31). ZIO stained the membranes of the proximal face of the Golgi bodies and endoplasmic reticulum. ZIO staining has given good contrast in thick sections such as a cotyledon cell, a root cell, and an aleurone layer for ER, dictyosomes cisternae, mitochondria, and nuclear envelopes (17,32-37). 

Landmann L (1986) Epidermal permeability barrier Transformation of lamellar granule-disks into intercellular sheets by a membrane-fusion process, a freeze-fracture study. J Invest Dermatol 87 202-209... 

Figure 25. Freeze fractured replica. P-fracture face of the plasma membrane in 15h aplanospore of Valonia veniricosa. The clustered TC s are shown, suggesting the build-up of new axis for microfibril orientation.

Fig. 13. Freeze-fracture replicas of rhodopsin-polyl5/DOPC membranes in 30% glycerol/water frozen from room temperature. The particles are morphological manifestations of the protein rhodopsin. The nonrandom distribution of particles indicates the presence of enriched domains of lipid and of protein. The particle-free domains constitute about 30% of the surface area.

Frank JS, Beydler S, Mottino G Membrane structure in ultrarapidly frozen, unpretreated, freeze fractured myocardium. Circ Res 1987 61 141-147. 

Conventional freeze-fracture replicas revealed the presence of the two membranes enveloping the hydrogenosomes presenting a different number and distribution of intramembranous particles (Fig. 7a-c) (Benchimol et al. 1996a Benchimol 2001). Four fracture faces were identified two concave faces representing the P faces of the outer and the inner membranes and two con-... 

Diaz JAM, De Souza W (1997) Purification and biochemical characterization of the hydrogenosomes of the flagellate protist Tritrichomonas foetus. Eur J Cell Biol 74 85-91 Diniz JA, Benchimol M (1998) Monocercomonas sp. cytochemistry and fine structure of freeze-fractured membranes. J Eukaryot Microbiol 45 314-322 Embley TM, Horner DA, Hirt RP (1997) Anaerobic eukaryote evolution hydrogenosomes as biochemically modified mitochondria Trends Ecol Evol 12 437-441 Embley TM, van der Gienzen M, Horner DA, Hirt RP, Dyal PL, Bell S, Foster PG (2003) Hydrogenosomes, mitochondria and early eukaryotic evolution. IUBMB Life 55 387-395... 

Fig. 2 a. Elcctronmicrograph of a freeze fractured preparation of isolated sarcoplasmic reticulum vesicles. 9 nm membrane particles are clearly visible on the concave cytoplasmic fracture faces of the vesicular membranes... 

FIGURE 20-30 Rosettes. The outside surface of the plant plasma membrane in a freeze-fractured sample, viewed here with electron microscopy, contains many hexagonal arrays of particles about 10 nm in diameter, believed to be composed of cellulose synthase molecules and associated enzymes. 

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