Heterogeneity of external surface charges near sodium channels in the nodal membrane of frog nerve

1984 ◽  
Vol 401 (2) ◽  
pp. 125-131 ◽  
Author(s):  
B. Neumcke ◽  
R. St�mpfli
Keyword(s):  
Sodium Channels ◽  
External Surface ◽  
Surface Charges ◽  
Nodal Membrane

scholarly journals Batrachotoxin-modified sodium channels in planar lipid bilayers. Ion permeation and block.

1987 ◽  
Vol 89 (6) ◽  
pp. 841-872 ◽  
Author(s):  
W N Green ◽  
L B Weiss ◽  
O S Andersen
Keyword(s):  
Lipid Bilayers ◽  
Sodium Channels ◽  
Single Channel ◽  
Divalent Cations ◽  
Cation Binding ◽  
Planar Lipid Bilayers ◽  
Surface Charges ◽  
High Concentrations ◽  
Conductance States ◽  
Single Channel Currents

Batrachotoxin-modified, voltage-dependent sodium channels from canine forebrain were incorporated into planar lipid bilayers. Single-channel conductances were studied for [Na+] ranging between 0.02 and 3.5 M. Typically, the single-channel currents exhibited a simple two-state behavior, with transitions between closed and fully open states. Two other conductance states were observed: a subconductance state, usually seen at [NaCl] greater than or equal to 0.5 M, and a flickery state, usually seen at [NaCl] less than or equal to 0.5 M. The flickery state became more frequent as [NaCl] was decreased below 0.5 M. The K+/Na+ permeability ratio was approximately 0.16 in 0.5 and 2.5 M salt, independent of the Na+ mole fraction, which indicates that there are no interactions among permeant ions in the channels. Impermeant and permeant blocking ions (tetraethylammonium, Ca++, Zn++, and K+) have different effects when added to the extracellular and intracellular solutions, which indicates that the channel is asymmetrical and has at least two cation-binding sites. The conductance vs. [Na+] relation saturated at high concentrations, but could not be described by a Langmuir isotherm, as the conductance at low [NaCl] is higher than predicted from the data at [NaCl] greater than or equal to 1.0 M. At low [NaCl] (less than or equal to 0.1 M), increasing the ionic strength by additions of impermeant monovalent and divalent cations reduced the conductance, as if the magnitude of negative electrostatic potentials at the channel entrances were reduced. The conductances were comparable for channels in bilayers that carry a net negative charge and bilayers that carry no net charge. Together, these results lead to the conclusion that negative charges on the channel protein near the channel entrances increase the conductance, while lipid surface charges are less important.

scholarly journals Effects of external surface charges on the enhanced piezoelectric potential of ZnO and AlN nanowires and nanotubes

AIP Advances ◽  
2012 ◽  
Vol 2 (4) ◽  
pp. 042174 ◽  
Author(s):  
Seong Min Kim ◽  
Hyeok Kim ◽  
Youngmin Nam ◽  
Sungjin Kim
Keyword(s):  
External Surface ◽  
Surface Charges ◽  
Piezoelectric Potential

Scanning and Transmission Microscopy of Nematocyst Batteries in Epitheliomuscular Cells of Hydra

1971 ◽  
Vol 29 ◽  
pp. 410-411 ◽  
Author(s):  
Jane A. Westfall ◽  
S. Yamataka ◽  
Paul D. Enos
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Osmium Tetroxide ◽  
External Surface ◽  
Three Dimensional ◽  
Surface Structures ◽  
Transmission Microscopy ◽  
Transmission Electron ◽  
Freeze Dried ◽  
Scanning Electron

Scanning electron microscopy (SEM) provides three dimensional details of external surface structures and supplements ultrastructural information provided by transmission electron microscopy (TEM). Animals composed of watery jellylike tissues such as hydras and other coelenterates have not been considered suitable for SEM studies because of the difficulty in preserving such organisms in a normal state. This study demonstrates 1) the successful use of SEM on such tissue, and 2) the unique arrangement of batteries of nematocysts within large epitheliomuscular cells on tentacles of Hydra littoralis.Whole specimens of Hydra were prepared for SEM (Figs. 1 and 2) by the fix, freeze-dry, coat technique of Small and Màrszalek. The specimens were fixed in osmium tetroxide and mercuric chloride, freeze-dried in vacuo on a prechilled 1 Kg brass block, and coated with gold-palladium. Tissues for TEM (Figs. 3 and 4) were fixed in glutaraldehyde followed by osmium tetroxide. Scanning micrographs were taken on a Cambridge Stereoscan Mark II A microscope at 10 KV and transmission micrographs were taken on an RCA EMU 3G microscope (Fig. 3) or on a Hitachi HU 11B microscope (Fig. 4).

High-resolution gold labeling

1993 ◽  
Vol 51 ◽  
pp. 330-331
Author(s):  
James F. Hainfeld ◽  
Frederic R. Furuya ◽  
Kyra Carbone ◽  
Martha Simon ◽  
Beth Lin ◽  
...  
Keyword(s):  
Dihydrofolate Reductase ◽  
Polypeptide Chain ◽  
External Surface ◽  
Gold Cluster ◽  
Macromolecular Complex ◽  
Gold Compound ◽  
Central Cavity ◽  
Chain Folding ◽  
E Coli ◽  
Chaperonin Groel

A recently developed 1.4 nm gold cluster has been found to be useful in labeling macromolecular sites to 1-3 nm resolution. The gold compound is organically derivatized to contain a monofunctional arm for covalent linking to biomolecules. This may be used to mark a specific site on a structure, or to first label a component and then reassemble a multicomponent macromolecular complex. Two examples are given here: the chaperonin groEL and ribosomes.Chaperonins are essential oligomeric complexes that mediate nascent polypeptide chain folding to produce active proteins. The E. coli chaperonin, groEL, has two stacked rings with a central hole ∽6 nm in diameter. The protein dihydrofolate reductase (DHFR) is a small protein that has been used in chain folding experiments, and serves as a model substrate for groEL. By labeling the DHFR with gold, its position with respect to the groEL complex can be followed. In particular, it was sought to determine if DHFR refolds on the external surface of the groEL complex, or whether it interacts in the central cavity.

Medullary epithelial sodium channels (ENAC) participate in cerebral blood flow (CBF) autoregulation

2005 ◽  
Vol 25 (1_suppl) ◽  
pp. S190-S190
Author(s):  
Eugene Golanov ◽  
Heather Drummond ◽  
Jasleen Shant ◽  
Benjamin Clower ◽  
Betty Chen
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Sodium Channels ◽  
Epithelial Sodium Channels
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