Nonconducting state

Using the cell-attached patch clamp technique on frog muscle fibers (79), one can observe only two conditions the open, conducting state of the receptor and a nonconducting state of unknown identity. The transitions behave according to stochastic principles the lifetimes of any particular condition are distributed exponentially. The open state has a mean duration that is the inverse of the rate of channel closing. Because channel open time depends only upon a conformational shift, agonist concentration does not influence the parameter. It is, however, influenced... 

Other Substrates Deposition of cadmium was also studied on Bi, Sn and Pb [303], Ni [304], reticulated vitreous carbon [305], Ti [306], and indium tin oxide [307]. UPD of Cd on tellurium results in CdTe formation [270, 308]. Electrodes coated with conducting polymers were also used to deposit cadmium electrochemi-cally. In the case of polyaniline, the metal reduction potential corresponds to the neutral (nonconducting) state of the polymer, therefore cadmium was found to deposit on the substrate-glassy carbon electrode surface, in the open pores of the polymer film [309, 310]. 

Association-dissociation equilibrium of artificial amphiphiles in either lipid layer may produce ion-conducting and nonconducting states, which may correspond to open and closed states, respectively. 

Charge transfer states (CT) are often found in molecular systems side by side with excitonic states. CT states describe polar nonconducting states bound by coulomb interaction of the electron-hole pairs. CT states may be ionized with localization of the charges on definite molecules. 

Na+ ions are substantially out of equilibrium because, although the plasma membrane does have specific channels for Na+ diffusion, in the resting nerve cell almost all of these channels are in an inactive, nonconducting state. 

Electrical measurements with purified, reconstituted Na+ channels have demonstrated that an individual channel can exist in either conductive or nonconductive states. As shown in figure SI.4, the fraction of time that a channel spends in the conductive state depends strongly on Ai//, increasing abruptly as A iff is made less negative. These results agree well with the notion that a local depolarization of the plasma membrane switches the nearby Na+ channels to their conductive states and thus launches an action potential that propagates down the cell. 

Chemical structures for (SN)X and the nonconducting states of conducting polymers. 

It is important to realize that the conformational change from the Closed to the Open state is a reversible step, but the conversion from the Open to the Inactivated state is irreversible. Thus, upon continuing depolarization, all sodium channels eventually become trapped in the inactivated (nonconducting) state, from which they can only escape to the (also nonconducting) closed state by hyperpolarization (i.e., by restoration of the resting potential). This removal of inactivation is a relatively slow process and determines how quick a neuron can fire a new action potential. Properties of the activation and inactivation processes can be conveniently studied by clamping the membrane potential to... 

Inactivation—Process of ion channel transition from a conductive activated state to an inactivated nonconducting state, which is a separate conformational state of the channel. 

Shown in the reduced (nonconductive) state. These polymers become conductive after oxidation and the incorporation of anions. 

Membrane proteins often contain a-helical sections. We have developed a method called oriented circular dichroism (OCD see reference 1), which can be used to determine the orientation of a-helices with respect to the plane of the membrane. This method is simple and easy to use compared with, for example, the NMR method, which requires isotope labeled samples. Indeed, it is the ease of this method that allowed us to examine alamethicin in many different chemical conditions and that resolved a controversial question about the nonconducting state of alamethicin and subsequently led to the discovery of a new phenomenon of amphiphilic helical peptides (2). 

Since the early 1970s, most investigators agree that alamethicin monomers form a water-filled conducting pore like the staves of a barrel, and this assumption is consistent with most ion conduction data (23-25). However, conduction experiments provided no clues for the nonconduction state, either... 

A selective electrochemical modification of metallic SWNTs that have been wired to electrodes on a surface, has been achieved by Balasubramanian et al. [122]. The authors used, similarly to Strano et al., a diazonium agent to functionalize metallic SWNTs. Here, the reaction is driven by an electrical potential applied between electrodes in contact with tubes and a counter-electrode. The authors found conditions in which primarily metallic SWNTs react, once the semiconducting SWNTs are driven into the nonconducting state by an appropriate gate voltage. An experimental verification of the selective modification is given by transport measurements in which the signature of metallic SWNTs disappears after treatment. 

The failure of a material to return to its nonconductive state prior to the sueeeeding charging sequence will result in a decrease in the maximum charge acceptance of the photoconductor. This phenomenon is addressed as fatigue. It can he avoided by the selection of photoconductive materials having a rapid switching capacity. 

A photon of sufficient energy can be absorbed by the photon detector material to excite an electron from a nonconducting state into a conducting... 

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