Clamping phenomenon

The inhibitory potencies of three of these molecules agreed with published values for murine Kv 3 (Table 4.1). The one exception was ShK that appeared to be 10-fold less potent than both published values and our own in-house values obtained by manual patch-clamp methods. It has been reported that ShK has a slow on-rate (t= 20 min) for block of Kv 3 (Middleton et al. 2003). This phenomenon may contribute to the reduced potency of ShK in our automated electrophysiology assay, because our protocol included a compound incubation time of only 5 to 10 min. Longer compound incubation times may improve the potency of ShK but would be associated with greater run-down in the K+ current amplitude. We also tested the A LI-selective blocker, dendrotoxin, and not surprisingly it did not inhibit the Kv. 3 current at concentrations up to 167 nM, which is well above its IC50 value for Kv 1.1 in our hands (17 pM data not shown). 

It was subsequendy suggested that the phenomenon might alternatively be explained by the existence in parallel of two types of channel with different characteristics. But studies by Correa Bezanilla (1994) in patch-clamped squid... 

Due to the abrasive grains striking the adherend surfaces with high energy by means of compressed air, surface densification with ensuing development of tension may occur, entailing a deflection, especially in the case of thin adherends (sheet metal up to 2 mm thick). This phenomenon may be avoided by clamping... 

Plastics will sometimes thin out at an insert or parting line. With resins such as LDPE, this phenomenon is of little importance, but with HDPE and similar resins, it can be a serious problem. When inserts are used, they should be fitted tightly. The parting line miter should be as close as possible, and sufficient clamping force should be provided to prevent partial opening... 

Lynch and Shelby (1984) examined the reasons for the high dielectric properties of lead titanate glass-ceramics. They defined the matrix phase around the ferroelectric crystals. They also determined a special effect they called clamping. This phenomenon occurs when the glass matrix contracts and produces compressive stress within the ferroelectric particles, causing paraelectric-to-ferroelectric phase transition. As a result, the crystal size must be controlled for electro-optic applications. The crj tals should preferably be smaller than 0.1 pm. 

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