Relationship between Kir2.1/Kir2.3 activity and their distributions between cholesterol-rich and cholesterol-poor membrane domains

2007 ◽  
Vol 293 (1) ◽  
pp. C440-C450 ◽  
Author(s):  
Saloni Tikku ◽  
Yulia Epshtein ◽  
Heidi Collins ◽  
Alexander J. Travis ◽  
George H. Rothblat ◽  
...  
Keyword(s):  
Opposite Effect ◽  
Membrane Rafts ◽  
Cholesterol Depletion ◽  
Membrane Domains ◽  
Double Peak ◽  
Cellular Cholesterol ◽  
Different Types ◽  
Lipid Environment ◽  
Kinetics Of

Our earlier studies have shown that Kir2.x channels are suppressed by an increase in the level of cellular cholesterol, whereas cholesterol depletion enhances the activity of the channels. In this study, we show that Kir2.1 and Kir2.3 channels have double-peak distributions between cholesterol-rich (raft) and cholesterol-poor (non-raft) membrane fractions, indicating that the channels exist in two different types of lipid environment. We also show that whereas methyl-β-cyclodextrin-induced cholesterol depletion removes cholesterol from both raft and non-raft membrane fractions, cholesterol enrichment results in cholesterol increase exclusively in the raft fractions. Kinetics of both depletion-induced Kir2.1 enhancement and enrichment-induced Kir2.1 suppression correlate with the changes in the level of raft cholesterol. Furthermore, we show not only that cholesterol depletion shifts the distribution of the channels from cholesterol-rich to cholesterol-poor membrane fractions but also that cholesterol enrichment has the opposite effect. These observations suggest that change in the level of raft cholesterol alone is sufficient to suppress Kir2 activity and to facilitate partitioning of the channels to cholesterol-rich domains. Therefore, we suggest that partitioning to membrane rafts plays an important role in the sensitivity of Kir2 channels to cholesterol.

Membrane–cytoskeleton interactions in cholesterol-dependent domain formation

2015 ◽  
Vol 57 ◽  
pp. 177-187 ◽  
Author(s):  
Jennifer N. Byrum ◽  
William Rodgers
Keyword(s):  
Biological Properties ◽  
Membrane Rafts ◽  
Membrane Domains ◽  
Biological Functions ◽  
Membrane Cytoskeleton ◽  
Heterogeneous Structures ◽  
Integral Role ◽  
Model Cell ◽  
Actomyosin Cytoskeleton ◽  
Dependent Domain

Since the inception of the fluid mosaic model, cell membranes have come to be recognized as heterogeneous structures composed of discrete protein and lipid domains of various dimensions and biological functions. The structural and biological properties of membrane domains are represented by CDM (cholesterol-dependent membrane) domains, frequently referred to as membrane ‘rafts’. Biological functions attributed to CDMs include signal transduction. In T-cells, CDMs function in the regulation of the Src family kinase Lck (p56lck) by sequestering Lck from its activator CD45. Despite evidence of discrete CDM domains with specific functions, the mechanism by which they form and are maintained within a fluid and dynamic lipid bilayer is not completely understood. In the present chapter, we discuss recent advances showing that the actomyosin cytoskeleton has an integral role in the formation of CDM domains. Using Lck as a model, we also discuss recent findings regarding cytoskeleton-dependent CDM domain functions in protein regulation.

Studies on the Behavior Some Paints in Electro-insulating Fluid Based on Vegetable Esters

2018 ◽  
Vol 69 (5) ◽  
pp. 1139-1144
Author(s):  
Iosif Lingvay ◽  
Adriana Mariana Bors ◽  
Livia Carmen Ungureanu ◽  
Valerica Stanoi ◽  
Traian Rus
Keyword(s):  
Structural Changes ◽  
Oxidation Processes ◽  
High Oleic ◽  
Painting Materials ◽  
Insulating Paper ◽  
Different Types ◽  
Mechanism And Kinetics ◽  
Kinetics Of ◽  
Natural Ester

For the purpose of using three different types of painting materials for the inner protection of the transformer vats, their behavior was studied under actual conditions of operation in the transformer (thermal stress in electro-insulating fluid based on the natural ester in contact with copper for electro-technical use and electro-insulating paper). By comparing determination of the content in furans products (HPLC technique) and gases formed (by gas-chromatography) in the electro-insulating fluid (natural ester with high oleic content) thermally aged at 130 �C to 1000 hours in closed glass vessels, it have been found that the presence the investigated painting materials lead to a change in the mechanism and kinetics of the thermo-oxidation processes. These changes are supported by oxygen dissolved in oil, what leads to decrease both to gases formation CO2, CO, H2, CH4, C2H4 and C2H6) and furans products (5-HMF, 2-FOL, 2 -FAL and 2-ACF). The painting materials investigated during the heat treatment applied did not suffer any remarkable structural changes affecting their functionality in the electro-insulating fluid based on vegetable esters.

Kinetics of Ion-Pair Effect of Aquation of Bromopentaammine Cobalt(III) Complex in Different Dicarboxylate Media

2011 ◽  
Vol 324 ◽  
pp. 166-169 ◽  
Author(s):  
Farah Zeitouni ◽  
Gehan El-Subruiti ◽  
Ghassan Younes ◽  
Mohammad Amira
Keyword(s):  
Free Energy ◽  
Solvent Effect ◽  
Compensation Effect ◽  
Ion Pairing ◽  
Reaction Rates ◽  
Ion Pair ◽  
Free Energy Of Activation ◽  
Different Types ◽  
Different Temperatures ◽  
Kinetics Of

The rate of aquation of bromopentaammine cobalt(III) ion in the presence of different types of dicarboxylate solutions containing tert-butanol (40% V/V) have been measured spectrophotometrically at different temperatures (30-600°C) in the light of the effects of ion-pairing on reaction rates and mechanism. The thermodynamic and extrathermodynamic parameters of activation have been calculated and discussed in terms of solvent effect on the ion-pair aquation reaction. The free energy of activation ∆Gip* is more or less linearly varied among the studied dicarboxylate ion-pairing ligands indicating the presence of compensation effect between ∆Hip* and ∆Sip*. Comparing the kip values with respect of different buffers at 40% of ter-butanol is introduced.

Etude par spectrométrie infrarouge de l'action de solvants aprotiques sur l'association ester–eau et ester–Ba2+. Discussion du rôle catalytique du solvant et de l'ion Ba2+ dans l'hydrolyse alcaline du propionate de methyle

1979 ◽  
Vol 57 (4) ◽  
pp. 400-403 ◽  
Author(s):  
Anne Le Narvor ◽  
Pierre Saumagne
Keyword(s):  
Ir Spectra ◽  
Charge Density ◽  
Carbonyl Group ◽  
Alkaline Hydrolysis ◽  
Experimental Results ◽  
Methyl Propionate ◽  
Orbital Control ◽  
Different Types ◽  
Kinetics Of ◽  
Better Than

The ir spectra of mixtures of methyl propionate/water and methyl propionate/Ba2+ in dimethylsulfoxide and in acetonitrile have been recorded in the region of the νCO mode of the ester. Evidence is presented to indicate the presence of different types of complexes; their concentration was determined as a function of the composition of the medium. The spectroscopic results are compared to those from the kinetics of the alkaline hydrolysis in the same conditions. It is demonstrated that the orbital control explains the experimental results better than does the charge density on the carbon of the carbonyl group. [Journal translation]

scholarly journals Enhanced Adsorption of Methanol by Oxidised Nutshell Carbon

2000 ◽  
Vol 18 (3) ◽  
pp. 261-266 ◽  
Author(s):  
Alan Bailey ◽  
Mike Williams ◽  
Lyndsay Dunne ◽  
Lynne Beames
Keyword(s):  
Nitric Acid ◽  
Water Adsorption ◽  
Opposite Effect ◽  
Kinetics Of Adsorption ◽  
Dry Air ◽  
Low Concentrations ◽  
Methanol Vapour ◽  
Adsorption Reduction ◽  
Enhanced Adsorption ◽  
Kinetics Of

A nutshell charcoal was oxidised and reduced and the effect of the treatments on the water adsorption isotherms and methanol vapour penetration noted. Oxidation with 6 M nitric acid increased the penetration times for methanol vapour in dry air, not by just raising the dynamic capacity at low concentrations but also by improving the kinetics of adsorption. Reduction caused the opposite effect. The improvement in the adsorption kinetics is thought to be due to surface diffusion on to the oxidised surface of the transport pores.

scholarly journals Dye removal abilities of the mesophilic and thermophilic biomass: a kinetics study

2018 ◽  
Vol 20 (2) ◽  
pp. 408-416
Keyword(s):  
Intraparticle Diffusion ◽  
Second Order ◽  
Intraparticle Diffusion Model ◽  
First Order Kinetics ◽  
Different Types ◽  
Pseudo Second Order ◽  
Acidic Conditions ◽  
Red Dye ◽  
Experimental Kinetics ◽  
Kinetics Of

Mesophilic biomass and thermophilic biomass samples were isolated and used to remove Dorasyn Red dye from aqueous solutions. The biosorption kinetics of dye uptake by four different types of biomass at three temperatures (20, 30, and 40 °C) were investigated using pseudo-first order kinetics, pseudo-second order kinetics, intraparticle diffusion, Elovich, and Bangham models. The pseudo-second-order kinetics model and the first stage of the intraparticle diffusion model were effective in describing the experimental kinetics data. The biosorption results showed that the mesophilic biomass samples could be useful for removing dye under acidic conditions.

Kinetics of Aspergillus niger growth at high glucose concentrations in different types of the cultures

1997 ◽  
pp. 49-58 ◽  
Author(s):  
E. Favela-Torres ◽  
M. García-Rivero ◽  
J. Cordova-López ◽  
S. Roussos ◽  
G. Viniegra-González ◽  
...  
Keyword(s):  
Aspergillus Niger ◽  
High Glucose ◽  
Different Types ◽  
Kinetics Of

Bletchley Park’s Sturgeon—The Fish That Laid No Eggs

Colossus ◽  
2006 ◽  
Author(s):  
Frode Weierud
Keyword(s):  
Opposite Effect ◽  
Armed Forces ◽  
Second World War ◽  
World War ◽  
German Armed Forces ◽  
Secretary Of State ◽  
Engineering Problems ◽  
Different Types ◽  
The One ◽  
Second World

This chapter describes the Siemens & Halske T52 cipher machines and explains how Bletchley Park broke them. (See photograph 51.) Many authors have confused the T52 with the Tunny machine, and have erroneously linked the T52 to Colossus. The German armed forces employed three different types of teleprinter cipher machines during the Second World War: the Lorenz SZ40/42a/42b (Tunny), the Siemens & Halske Schlüs-selfernschreibmaschine (SFM—Cipher Teleprinter Machine) T52, and the one-time-tape machine T43, also manufactured by Siemens. The Siemens T52 existed in four functionally distinct models: T52a/b, T52c, T52d, and T52e (there was also the T52ca, a modified version of the T52c). At Bletchley Park all T52 models went under the code name ‘Sturgeon’. The Siemens T43 was probably the unbreakable machine that BP called ‘Thrasher’. (This came into use relatively late in the war, and appears to have been used only on a few selected links.) In 1964 Erik Boheman, the Swedish Under-Secretary of State, first revealed that Sweden had broken the T52 during the Second World War. The Swedish successes against the T52 are the topic of Chapter 26. It was only in 1984 that the British officially acknowledged that Bletchley Park had also enjoyed some success against the T52. Not only did BP intercept traffic enciphered on the T52; it also broke all the different models that it discovered. It was clear from the beginning that the T52 was a very difficult machine to break. Probably it would have remained unbroken had it not been for German security blunders in using the machines. The blame should not be put entirely on the German teleprinter operators, however: the designers of the machines at Siemens, who failed to listen to the advice of the German cryptographic experts, were also responsible. The Siemens engineers seem to have focused more on the engineering problems than on the cryptographic security of the machine. The T52a/b and the original T52c were machines with quite limited security. The T52c is an extraordinary example of how not to go about designing a cryptographic machine. The wheel-combining logic, which was meant to strengthen the machine, had exactly the opposite effect—it eased the task of breaking the machine.

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