SummaryRab11 is known to associate primarily with perinuclear recycling endosomes and regulate recycling of endocytosed proteins. However, the recycling step in which Rab11 participates remains unknown. We show here that, in addition to causing tubulation of recycling endosomes, Rab11 depletion gives rise to accumulation of recycling carriers containing endocytosed transferrin and transferrin receptor beneath the plasma membrane. We also show that the carriers are transported from perinuclear recycling endosomes to the cell periphery along microtubules. Total internal reflection fluorescence microscopy of cells expressing EGFP-tagged transferrin receptor revealed that Rab11 depletion inhibits tethering and fusion of recycling carriers to the plasma membrane. Depletion of Sec15, which interacts with Rab11, or Exo70, both components of the exocyst tethering complex, leads to essentially the same phenotypes as those of Rab11 depletion. Thus, in addition to its role in recycling processes at perinuclear recycling endosomes, Rab11 is transported along microtubules to the cell periphery through association with recycling carriers, and directly regulates vesicle exocytosis at the plasma membrane in concert with the exocyst.

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The penultimate unit effects (PUEs) on the propagation, termination, and reversible addition‐fragmentation chain transfer (RAFT) processes in free radical copolymerization are discussed on the basis of recent publications. The propriety of the implicit and explicit PUE models in propagation and chain transfer processes is commented. The penultimate termination model with the geometric‐mean approximation and the related rate equation are highlighted.

We describe a method to coat fused silica, quartz, or glass electrophoresis tubes with hydrophilic polymers, such as methyl cellulose or dextran, in order to eliminate electroendosmosis and adsorption of solutes onto the tube wall. The coating was not split off upon exposure to a 5% solution of sodium dodecyl sulfate (SDS) at pH around 12 during a period of sixteen days or to 0.5 M HCl (pH 0.3) during 10 days. The high stability of the coating, which is attached to the silica surface via Si-O-Si-C bonds, permits electrophoresis experiments at extreme (besides neutral) pH values and allows short washes of the electrophoresis tubes between the runs with 0.05 M sodium hydroxide (pH 12.7) containing 5% SDS, and with 1 M HCl. These washing solutions release efficiently those solutes which have a tendency to adsorb onto the coating, which is a prerequisite for reproducible runs. The quality of the coating was strongly affected by the surface structure of the commercial fused silica tubing, which may vary from batch to batch. Attempts to standardize the surface structure of any tubing by treatments with NaOH and HCl to obtain a coating, the quality of which is independent of the original surface structure, were not successful. Therefore, it may be necessary to modify certain details of the coating procedure for each new batch of tubing to obtain optimum stability. Alternative coating procedures are therefore described, one of which is of general applicability (see last paragraph in Section 4).

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