Protein sliding contacts

FIGURE 10.37 Gap Juoctioos consist of hexameric arrays of cylindrical protein subunits in the plasma membrane. The subunit cylinders are tilted with respect to the axis running through the center of the gap Junction. A gap Junction between cells is formed when two hexameric arrays of subunits in separate cells contact each other and form a pore through which cellular contents may pass. Gap Junctions close by means of a twisting, sliding motion in which the subunits decrease their tilt with respect to the central axis. Closure of the gap Junction is Ca -dependent. 

In order to spread on a water surface and form a stable film a substance has to have hydrophilic and hydrophobic groups in it. The bottom side of a spread film of protein must be predominantly hydrophilic, while the side directed towards the air must be predominantly hydrophobic, otherwise a protein monolayer would not be stable on the water surface. That the air side of a protein monolayer is predominantly hydrophobic is shown by the experiments of Bull (70) who deposited single monolayers of egg albumin at various pressures on glass slides and measured the contact angle between water and the deposited film. The film deposited at 15 dynes pressure showed an adhesion tension of about 100 ergs per sq. cm. The adhesion tension of a pure hydro-... 

All protein arrays were printed by contact printing, based on capillary action, using the robotic microarrayer. The micro-machined pins consistently delivered samples of approximately 1 nL onto the gold slides at designated locations. Typically, circular spots with diameters ranging from 150 to 250 pm with pitches of about 250-300 pm were produced. The printing was performed at a relative humidity of 65% and a temperature of 25°C. After spotting, the protein immobilized slides were kept in a humid environment (65% relative humidity. 

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