Functional diversity of potassium channel voltage-sensing domains.

PubMed

Islas, León D

2016-01-01

Voltage-gated potassium channels or Kv's are membrane proteins with fundamental physiological roles. They are composed of 2 main functional protein domains, the pore domain, which regulates ion permeation, and the voltage-sensing domain, which is in charge of sensing voltage and undergoing a conformational change that is later transduced into pore opening. The voltage-sensing domain or VSD is a highly conserved structural motif found in all voltage-gated ion channels and can also exist as an independent feature, giving rise to voltage sensitive enzymes and also sustaining proton fluxes in proton-permeable channels. In spite of the structural conservation of VSDs in potassium channels, there are several differences in the details of VSD function found across variants of Kvs. These differences are mainly reflected in variations in the electrostatic energy needed to open different potassium channels. In turn, the differences in detailed VSD functioning among voltage-gated potassium channels might have physiological consequences that have not been explored and which might reflect evolutionary adaptations to the different roles played by Kv channels in cell physiology.

Functional diversity of potassium channel voltage-sensing domains

PubMed Central

Islas, León D.

2016-01-01

Abstract Voltage-gated potassium channels or Kv's are membrane proteins with fundamental physiological roles. They are composed of 2 main functional protein domains, the pore domain, which regulates ion permeation, and the voltage-sensing domain, which is in charge of sensing voltage and undergoing a conformational change that is later transduced into pore opening. The voltage-sensing domain or VSD is a highly conserved structural motif found in all voltage-gated ion channels and can also exist as an independent feature, giving rise to voltage sensitive enzymes and also sustaining proton fluxes in proton-permeable channels. In spite of the structural conservation of VSDs in potassium channels, there are several differences in the details of VSD function found across variants of Kvs. These differences are mainly reflected in variations in the electrostatic energy needed to open different potassium channels. In turn, the differences in detailed VSD functioning among voltage-gated potassium channels might have physiological consequences that have not been explored and which might reflect evolutionary adaptations to the different roles played by Kv channels in cell physiology. PMID:26794852

Magneto-optical trapping of potassium isotopes

NASA Astrophysics Data System (ADS)

Williamson, Robert Sylvester, III

1997-12-01

We have demonstrated a magneto-optical trap (scMOT) suitable for capturing radioactive potassium produced on- line with the UW-Madison 12MeV tandem electrostatic accelerator. To do this, we made and characterized the first scMOT for potassium, measured the potassium ultracold collision rate, and developed a numerical trap- loading rate model that makes useful quantitative predictions. We have created a cold beam of collimated potassium atoms using a pyramidal magneto-optical funnel and used it to load a long-lifetime scMOT operating at ultrahigh vacuum. We have also built a target that produces a beam of radioactive 37K and 38K and coupled it to the magneto-optical funnel and trap. Once a trap of radioactive 38K has been demonstrated, the primary goal of this project is to measure the beta-asymmetry parameter in the decay of 38K, performing a sensitive test of the Standard Model of weak interactions.

A solid with a hierarchical tetramodal micro-meso-macro pore size distribution

PubMed Central

Ren, Yu; Ma, Zhen; Morris, Russell E.; Liu, Zheng; Jiao, Feng; Dai, Sheng; Bruce, Peter G.

2013-01-01

Porous solids have an important role in addressing some of the major energy-related problems facing society. Here we describe a porous solid, α-MnO2, with a hierarchical tetramodal pore size distribution spanning the micro-, meso- and macro pore range, centred at 0.48, 4.0, 18 and 70 nm. The hierarchical tetramodal structure is generated by the presence of potassium ions in the precursor solution within the channels of the porous silica template; the size of the potassium ion templates the microporosity of α-MnO2, whereas their reactivity with silica leads to larger mesopores and macroporosity, without destroying the mesostructure of the template. The hierarchical tetramodal pore size distribution influences the properties of α-MnO2 as a cathode in lithium batteries and as a catalyst, changing the behaviour, compared with its counterparts with only micropores or bimodal micro/mesopores. The approach has been extended to the preparation of LiMn2O4 with a hierarchical pore structure. PMID:23764887

The distribution and mechanism of pore formation in copper foams fabricated by Lost Carbonate Sintering method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shahzeydi, Mohammad Hosein; Parvanian, Amir Masoud; Panjepour, Masoud, E-mail: panjepour@cc.iut.ac.ir

2016-01-15

In this research, utilizing X-ray computed tomography (XCT), geometrical characterization, and pore formation mechanisms of highly porous copper foams manufactured by powder metallurgical (PM) process are investigated. Open-cell copper foams with porosity percentages of 60% and 80% and with a pore size within the range of 300–600 μm were manufactured by using potassium carbonate as a space holder agent via the Lost Carbonate Sintering (LCS) technique. XCT and SEM were also employed to investigate the three-dimensional structure of foams and to find the effect of the parameters of the space holders on the structural properties of copper foams. The resultmore » showed an excellent correlation between the structural properties of the foams including the size and shape of the pores, porosity percentage, volume percentage, particle size, and the shape of the sacrificial agent used. Also, the advanced image analysis of XCT images indicated fluctuations up to ± 10% in porosity distribution across different cross-sections of the foams. Simultaneous thermal analysis (STA: DTA–TG) was also used to study the thermal history of the powders used during the manufacturing process of the foams. The results indicated that the melting and thermal decomposition of the potassium carbonate occurred simultaneously at 920 °C and created the porous structure of the foams. By combining the STA result with the result of the tension analysis of cell walls, the mechanisms of open-pore formation were suggested. In fact, most open pores in the samples were formed due to the direct contact of potassium carbonate particles with each other in green compact. Also, it was found that the thermal decomposition of potassium carbonate particles into gaseous CO{sub 2} led to the production of gas pressure inside the closed pores, which eventually caused the creation of cracks on the cell walls and the opening of the pores in foam's structure. - Highlights: • Structural characterization of

Performance analysis of a potassium-base AMTEC cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, C.; Hendricks, T.J.; Hunt, T.K.

1998-07-01

Sodium-BASE Alkali-Metal-Thermal-to-Electric-Conversion (AMTEC) cells have been receiving increased attention and funding from the Department of Energy, NASA and the United States Air Force. Recently, sodium-BASE (Na-BASE) AMTEC cells were selected for the Advanced Radioisotope Power System (ARPS) program for the next generation of deep-space missions and spacecraft. Potassium-BASE (K-BASE) AMTEC cells have not received as much attention to date, even though the vapor pressure of potassium is higher than that of sodium at the same temperature. So that, K-BASE AMTEC cells with potentially higher open circuit voltage and higher power output than Na-BASE AMTEC cells are possible. Because the surfacemore » tension of potassium is about half of the surface tension of sodium at the same temperature, the artery and evaporator design in a potassium AMTEC cell has much more challenging pore size requirements than designs using sodium. This paper uses a flexible thermal/fluid/electrical model to predict the performance of a K-BASE AMTEC cell. Pore sizes in the artery of K-BASE AMTEC cells must be smaller by an order of magnitude than in Na-BASE AMTEC cells. The performance of a K-BASE AMTEC cell was higher than a Na-BASE AMTEC cell at low voltages/high currents. K-BASE AMTEC cells also have the potential of much better electrode performance, thereby creating another avenue for potentially better performance in K-BASE AMTEC cells.« less

Potassium channels in brain mitochondria.

PubMed

Bednarczyk, Piotr

2009-01-01

Potassium channels are the most widely distributed class of ion channels. These channels are transmembrane proteins known to play important roles in both normal and pathophysiological functions in all cell types. Various potassium channels are recognised as potential therapeutic targets in the treatment of Parkinson's disease, Alzheimer's disease, brain/spinal cord ischaemia and sepsis. In addition to their importance as therapeutic targets, certain potassium channels are known for their beneficial roles in anaesthesia, cardioprotection and neuroprotection. Some types of potassium channels present in the plasma membrane of various cells have been found in the inner mitochondrial membrane as well. Potassium channels have been proposed to regulate mitochondrial membrane potential, respiration, matrix volume and Ca(+) ion homeostasis. It has been proposed that mitochondrial potassium channels mediate ischaemic preconditioning in various tissues. However, the specificity of a pharmacological agents and the mechanisms underlying their effects on ischaemic preconditioning remain controversial. The following potassium channels from various tissues have been identified in the inner mitochondrial membrane: ATP-regulated (mitoK(ATP)) channel, large conductance Ca(2+)-regulated (mitoBK(Ca)) channel, intermediate conductance Ca(2+)-regulated (mitoIK(Ca)) channel, voltage-gated (mitoKv1.3 type) channel, and twin-pore domain (mitoTASK-3) channel. It has been shown that increased potassium flux into brain mitochondria induced by either the mitoK(ATP) channel or mitoBK(Ca) channel affects the beneficial effects on neuronal cell survival under pathological conditions. Recently, differential distribution of mitoBK(Ca) channels has been observed in neuronal mitochondria. These findings may suggest a neuroprotective role for the mitoBK(Ca) channel in specific brain structures. This minireview summarises current data on brain mitochondrial potassium channels and the efforts to identify

Pore size matters for potassium channel conductance

PubMed Central

Moldenhauer, Hans; Pincuntureo, Matías

2016-01-01

Ion channels are membrane proteins that mediate efficient ion transport across the hydrophobic core of cell membranes, an unlikely process in their absence. K+ channels discriminate K+ over cations with similar radii with extraordinary selectivity and display a wide diversity of ion transport rates, covering differences of two orders of magnitude in unitary conductance. The pore domains of large- and small-conductance K+ channels share a general architectural design comprising a conserved narrow selectivity filter, which forms intimate interactions with permeant ions, flanked by two wider vestibules toward the internal and external openings. In large-conductance K+ channels, the inner vestibule is wide, whereas in small-conductance channels it is narrow. Here we raise the idea that the physical dimensions of the hydrophobic internal vestibule limit ion transport in K+ channels, accounting for their diversity in unitary conductance. PMID:27619418

Sodium and potassium competition in potassium-selective and non-selective channels

NASA Astrophysics Data System (ADS)

Sauer, David B.; Zeng, Weizhong; Canty, John; Lam, Yeeling; Jiang, Youxing

2013-11-01

Potassium channels selectively conduct K+, primarily to the exclusion of Na+, despite the fact that both ions can bind within the selectivity filter. Here we perform crystallographic titration and single-channel electrophysiology to examine the competition of Na+ and K+ binding within the filter of two NaK channel mutants; one is the potassium-selective NaK2K mutant and the other is the non-selective NaK2CNG, a CNG channel pore mimic. With high-resolution structures of these engineered NaK channel constructs, we explicitly describe the changes in K+ occupancy within the filter upon Na+ competition by anomalous diffraction. Our results demonstrate that the non-selective NaK2CNG still retains a K+-selective site at equilibrium, whereas the NaK2K channel filter maintains two high-affinity K+ sites. A double-barrier mechanism is proposed to explain K+ channel selectivity at low K+ concentrations.

Side Fenestrations Provide an "Anchor" for a Stable Binding of A1899 to the Pore of TASK-1 Potassium Channels.

PubMed

Ramírez, David; Arévalo, Bárbara; Martínez, Gonzalo; Rinné, Susanne; Sepúlveda, Francisco V; Decher, Niels; González, Wendy

2017-07-03

A1899 is a potent and selective inhibitor of the two-pore domain potassium (K 2P ) channel TASK-1. It was previously reported that A1899 acts as an open-channel blocker and binds to residues of the P1 and P2 regions, the M2 and M4 segments, and the halothane response element. The recently described crystal structures of K 2P channels together with the newly identified side fenestrations indicate that residues relevant for TASK-1 inhibition are not purely facing the central cavity as initially proposed. Accordingly, the TASK-1 binding site and the mechanism of inhibition might need a re-evaluation. We have used TASK-1 homology models based on recently crystallized K 2P channels and molecular dynamics simulation to demonstrate that the highly potent TASK-1 blocker A1899 requires binding to residues located in the side fenestrations. Unexpectedly, most of the previously described residues that interfere with TASK-1 blockade by A1899 project their side chains toward the fenestration lumina, underlining the relevance of these structures for drug binding in K 2P channels. Despite its hydrophobicity, A1899 does not seem to use the fenestrations to gain access to the central cavity from the lipid bilayer. In contrast, binding of A1899 to residues of the side fenestrations might provide a physical "anchor", reflecting an energetically favorable binding mode that after pore occlusion stabilizes the closed state of the channels.

In vivo Expression of a Light-activatable Potassium Channel Using Unnatural Amino Acids

PubMed Central

Kang, Ji-Yong; Kawaguchi, Daichi; Coin, Irene; Xiang, Zheng; O’Leary, Dennis D. M.; Slesinger, Paul A.; Wang, Lei

2013-01-01

SUMMARY Optical control of protein function provides excellent spatial-temporal resolution for studying proteins in situ. Although light-sensitive exogenous proteins and ligands have been employed to manipulate neuronal activity, a method for optical control of neuronal proteins using unnatural amino acids (Uaa) in vivo is lacking. Here, we describe the genetic incorporation of a photoreactive Uaa into the pore of an inwardly-rectifying potassium channel Kir2.1. The Uaa occluded the pore, rendering the channel non-conducting, and upon brief light illumination, was released to permit outward K+ current. Expression of this photo-inducible inwardly rectifying potassium (PIRK) channel in rat hippocampal neurons created a light-activatable PIRK switch for suppressing neuronal firing. We also expressed PIRK channels in embryonic mouse neocortex in vivo and demonstrated a light-activated PIRK current in cortical neurons. The principles applied here to a potassium channel could be generally expanded to other proteins expressed in the brain to enable optical regulation. PMID:24139041

Reverse weathering in marine sediments and the geochemical cycle of potassium in seawater: Insights from the K isotopic composition (41K/39K) of deep-sea pore-fluids

USGS Publications Warehouse

Santiago Ramos, Danielle P.; Morgan, Leah; Lloyd, Nicholas S.; Higgins, John A.

2018-01-01

In situ Al-silicate formation, also known as “reverse weathering,” is an important sink of many of the major and minor cations in seawater (e.g. Mg, K, and Li). However, the importance of this sink in global geochemical cycles and isotopic budgets of these elements remains poorly constrained. Here, we report on the potassium isotopic composition (41">41K/39">39K) of deep-sea sediment pore-fluids from four (Integrated) Ocean Drilling Program sites (1052, U1378, U1395 and U1403) to characterize potassium isotopic fractionation associated with the formation of authigenic Al-silicate minerals in marine sediments and its role in elevating the 41">41K/39">39K of seawater relative to bulk silicate Earth. Isotopic ratios are obtained by high-resolution multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) in cold plasma conditions with a long-term external reproducibility of ca. 0.17‰. We find that, although all sites are characterized by pore-fluid K concentrations that decline with increasing depth, their K isotopic profiles vary systematically from site-to-site; at sites characterized by rapid sedimentation rates, pore-fluid profiles of 41">41K/39">39K are relatively invariant whereas at sites characterized by slow sedimentation rates, 41">41K/39">39K declines with depth by up to 1.8‰. Results from 1-D diffusion-advection-reaction models suggest that these differences may result from a complex interplay between sedimentation rate and fractionation of K isotopes during diffusion, Al-silicate authigenesis, and ion exchange. Model simulations suggest fractionation factors between 0.9980 and 1.0000 for reverse weathering reactions in deep-sea sediments. Although deep-sea sites do not constitute major sinks of K in seawater, some of the processes responsible for K isotopic fractionation at these sites (diffusion and Al-silicate authigenesis) likely play a role in determining the 41">41K/39">39K of seawater.

Pore Helices Play a Dynamic Role as Integrators of Domain Motion during Kv11.1 Channel Inactivation Gating*

PubMed Central

Perry, Matthew D.; Ng, Chai Ann; Vandenberg, Jamie I.

2013-01-01

Proteins that form ion-selective pores in the membrane of cells are integral to many rapid signaling processes, including regulating the rhythm of the heartbeat. In potassium channels, the selectivity filter is critical for both endowing an exquisite selectivity for potassium ions, as well as for controlling the flow of ions through the pore. Subtle rearrangements in the complex hydrogen-bond network that link the selectivity filter to the surrounding pore helices differentiate conducting (open) from nonconducting (inactivated) conformations of the channel. Recent studies suggest that beyond the selectivity filter, inactivation involves widespread rearrangements of the channel protein. Here, we use rate equilibrium free energy relationship analysis to probe the structural changes that occur during selectivity filter gating in Kv11.1 channels, at near atomic resolution. We show that the pore helix plays a crucial dynamic role as a bidirectional interface during selectivity filter gating. We also define the molecular bases of the energetic coupling between the pore helix and outer helix of the pore domain that occurs early in the transition from open to inactivated states, as well as the coupling between the pore helix and inner helix late in the transition. Our data demonstrate that the pore helices are more than just static structural elements supporting the integrity of the selectivity filter; instead they play a crucial dynamic role during selectivity filter gating. PMID:23471968

Analysis of intracellular and extracellular microcystin variants in sediments and pore waters by accelerated solvent extraction and high performance liquid chromatography-tandem mass spectrometry.

PubMed

Zastepa, Arthur; Pick, Frances R; Blais, Jules M; Saleem, Ammar

2015-05-04

The fate and persistence of microcystin cyanotoxins in aquatic ecosystems remains poorly understood in part due to the lack of analytical methods for microcystins in sediments. Existing methods have been limited to the extraction of a few extracellular microcystins of similar chemistry. We developed a single analytical method, consisting of accelerated solvent extraction, hydrophilic-lipophilic balance solid phase extraction, and reversed phase high performance liquid chromatography-tandem mass spectrometry, suitable for the extraction and quantitation of both intracellular and extracellular cyanotoxins in sediments as well as pore waters. Recoveries of nine microcystins, representing the chemical diversity of microcystins, and nodularin (a marine analogue) ranged between 75 and 98% with one, microcystin-RR (MC-RR), at 50%. Chromatographic separation of these analytes was achieved within 7.5 min and the method detection limits were between 1.1 and 2.5 ng g(-1) dry weight (dw). The robustness of the method was demonstrated on sediment cores collected from seven Canadian lakes of diverse geography and trophic states. Individual microcystin variants reached a maximum concentration of 829 ng g(-1) dw on sediment particles and 132 ng mL(-1) in pore waters and could be detected in sediments as deep as 41 cm (>100 years in age). MC-LR, -RR, and -LA were more often detected while MC-YR, -LY, -LF, and -LW were less common. The analytical method enabled us to estimate sediment-pore water distribution coefficients (K(d)), MC-RR had the highest affinity for sediment particles (log K(d)=1.3) while MC-LA had the lowest affinity (log K(d)=-0.4), partitioning mainly into pore waters. Our findings confirm that sediments serve as a reservoir for microcystins but suggest that some variants may diffuse into overlying water thereby constituting a new route of exposure following the dissipation of toxic blooms. The method is well suited to determine the fate and persistence of different

Voltage Sensor Inactivation in Potassium Channels

PubMed Central

Bähring, Robert; Barghaan, Jan; Westermeier, Regina; Wollberg, Jessica

2012-01-01

In voltage-gated potassium (Kv) channels membrane depolarization causes movement of a voltage sensor domain. This conformational change of the protein is transmitted to the pore domain and eventually leads to pore opening. However, the voltage sensor domain may interact with two distinct gates in the pore domain: the activation gate (A-gate), involving the cytoplasmic S6 bundle crossing, and the pore gate (P-gate), located externally in the selectivity filter. How the voltage sensor moves and how tightly it interacts with these two gates on its way to adopt a relaxed conformation when the membrane is depolarized may critically determine the mode of Kv channel inactivation. In certain Kv channels, voltage sensor movement leads to a tight interaction with the P-gate, which may cause conformational changes that render the selectivity filter non-conductive (“P/C-type inactivation”). Other Kv channels may preferably undergo inactivation from pre-open closed-states during voltage sensor movement, because the voltage sensor temporarily uncouples from the A-gate. For this behavior, known as “preferential” closed-state inactivation, we introduce the term “A/C-type inactivation”. Mechanistically, P/C- and A/C-type inactivation represent two forms of “voltage sensor inactivation.” PMID:22654758

Solution structure and function of the "tandem inactivation domain" of the neuronal A-type potassium channel Kv1.4.

PubMed

Wissmann, Ralph; Bildl, Wolfgang; Oliver, Dominik; Beyermann, Michael; Kalbitzer, Hans-Robert; Bentrop, Detlef; Fakler, Bernd

2003-05-02

Cumulative inactivation of voltage-gated (Kv) K(+) channels shapes the presynaptic action potential and determines timing and strength of synaptic transmission. Kv1.4 channels exhibit rapid "ball-and-chain"-type inactivation gating. Different from all other Kvalpha subunits, Kv1.4 harbors two inactivation domains at its N terminus. Here we report the solution structure and function of this "tandem inactivation domain" using NMR spectroscopy and patch clamp recordings. Inactivation domain 1 (ID1, residues 1-38) consists of a flexible N terminus anchored at a 5-turn helix, whereas ID2 (residues 40-50) is a 2.5-turn helix made up of small hydrophobic amino acids. Functional analysis suggests that only ID1 may work as a pore-occluding ball domain, whereas ID2 most likely acts as a "docking domain" that attaches ID1 to the cytoplasmic face of the channel. Deletion of ID2 slows inactivation considerably and largely impairs cumulative inactivation. Together, the concerted action of ID1 and ID2 may promote rapid inactivation of Kv1.4 that is crucial for the channel function in short term plasticity.

The voltage-sensing domain of a phosphatase gates the pore of a potassium channel.

PubMed

Arrigoni, Cristina; Schroeder, Indra; Romani, Giulia; Van Etten, James L; Thiel, Gerhard; Moroni, Anna

2013-03-01

The modular architecture of voltage-gated K(+) (Kv) channels suggests that they resulted from the fusion of a voltage-sensing domain (VSD) to a pore module. Here, we show that the VSD of Ciona intestinalis phosphatase (Ci-VSP) fused to the viral channel Kcv creates Kv(Synth1), a functional voltage-gated, outwardly rectifying K(+) channel. Kv(Synth1) displays the summed features of its individual components: pore properties of Kcv (selectivity and filter gating) and voltage dependence of Ci-VSP (V(1/2) = +56 mV; z of ~1), including the depolarization-induced mode shift. The degree of outward rectification of the channel is critically dependent on the length of the linker more than on its amino acid composition. This highlights a mechanistic role of the linker in transmitting the movement of the sensor to the pore and shows that electromechanical coupling can occur without coevolution of the two domains.

Inter-subunit interactions across the upper voltage sensing-pore domain interface contribute to the concerted pore opening transition of Kv channels.

PubMed

Shem-Ad, Tzilhav; Irit, Orr; Yifrach, Ofer

2013-01-01

The tight electro-mechanical coupling between the voltage-sensing and pore domains of Kv channels lies at the heart of their fundamental roles in electrical signaling. Structural data have identified two voltage sensor pore inter-domain interaction surfaces, thus providing a framework to explain the molecular basis for the tight coupling of these domains. While the contribution of the intra-subunit lower domain interface to the electro-mechanical coupling that underlies channel opening is relatively well understood, the contribution of the inter-subunit upper interface to channel gating is not yet clear. Relying on energy perturbation and thermodynamic coupling analyses of tandem-dimeric Shaker Kv channels, we show that mutation of upper interface residues from both sides of the voltage sensor-pore domain interface stabilizes the closed channel state. These mutations, however, do not affect slow inactivation gating. We, moreover, find that upper interface residues form a network of state-dependent interactions that stabilize the open channel state. Finally, we note that the observed residue interaction network does not change during slow inactivation gating. The upper voltage sensing-pore interaction surface thus only undergoes conformational rearrangements during channel activation gating. We suggest that inter-subunit interactions across the upper domain interface mediate allosteric communication between channel subunits that contributes to the concerted nature of the late pore opening transition of Kv channels.

Enterocin P Causes Potassium Ion Efflux from Enterococcus faecium T136 Cells

PubMed Central

Herranz, Carmen; Cintas, Luis M.; Hernández, Pablo E.; Moll, Gert N.; Driessen, Arnold J. M.

2001-01-01

Enterocin P is a bacteriocin produced by Enterococcus faecium P13. We studied the mechanism of its bactericidal action using enterocin-P-sensitive E. faecium T136 cells. The bacteriocin is incapable of dissipating the transmembrane pH gradient. On the other hand, depending on the buffer used, enterocin P dissipates the transmembrane potential. Enterocin P efficiently elicits efflux of potassium ions, but not of intracellularly accumulated anions like phosphate and glutamate. Taken together, these data demonstrate that enterocin P forms specific, potassium ion-conducting pores in the cytoplasmic membrane of target cells. PMID:11181377

The voltage-sensing domain of a phosphatase gates the pore of a potassium channel

PubMed Central

Arrigoni, Cristina; Schroeder, Indra; Romani, Giulia; Van Etten, James L.; Thiel, Gerhard

2013-01-01

The modular architecture of voltage-gated K+ (Kv) channels suggests that they resulted from the fusion of a voltage-sensing domain (VSD) to a pore module. Here, we show that the VSD of Ciona intestinalis phosphatase (Ci-VSP) fused to the viral channel Kcv creates KvSynth1, a functional voltage-gated, outwardly rectifying K+ channel. KvSynth1 displays the summed features of its individual components: pore properties of Kcv (selectivity and filter gating) and voltage dependence of Ci-VSP (V1/2 = +56 mV; z of ∼1), including the depolarization-induced mode shift. The degree of outward rectification of the channel is critically dependent on the length of the linker more than on its amino acid composition. This highlights a mechanistic role of the linker in transmitting the movement of the sensor to the pore and shows that electromechanical coupling can occur without coevolution of the two domains. PMID:23440279

Mechanism of Electromechanical Coupling in Voltage-Gated Potassium Channels

PubMed Central

Blunck, Rikard; Batulan, Zarah

2012-01-01

Voltage-gated ion channels play a central role in the generation of action potentials in the nervous system. They are selective for one type of ion – sodium, calcium, or potassium. Voltage-gated ion channels are composed of a central pore that allows ions to pass through the membrane and four peripheral voltage sensing domains that respond to changes in the membrane potential. Upon depolarization, voltage sensors in voltage-gated potassium channels (Kv) undergo conformational changes driven by positive charges in the S4 segment and aided by pairwise electrostatic interactions with the surrounding voltage sensor. Structure-function relations of Kv channels have been investigated in detail, and the resulting models on the movement of the voltage sensors now converge to a consensus; the S4 segment undergoes a combined movement of rotation, tilt, and vertical displacement in order to bring 3–4e+ each through the electric field focused in this region. Nevertheless, the mechanism by which the voltage sensor movement leads to pore opening, the electromechanical coupling, is still not fully understood. Thus, recently, electromechanical coupling in different Kv channels has been investigated with a multitude of techniques including electrophysiology, 3D crystal structures, fluorescence spectroscopy, and molecular dynamics simulations. Evidently, the S4–S5 linker, the covalent link between the voltage sensor and pore, plays a crucial role. The linker transfers the energy from the voltage sensor movement to the pore domain via an interaction with the S6 C-termini, which are pulled open during gating. In addition, other contact regions have been proposed. This review aims to provide (i) an in-depth comparison of the molecular mechanisms of electromechanical coupling in different Kv channels; (ii) insight as to how the voltage sensor and pore domain influence one another; and (iii) theoretical predictions on the movement of the cytosolic face of the Kv channels during

Corrosion mechanism of carbon brick in the blast furnace hearth by potassium

NASA Astrophysics Data System (ADS)

Jiao, Ke-xin; Zhang, Jian-liang; Liu, Zheng-jian; Liu, Zhuang-zhuang; Deng, Yong; Fan, Xiaoyue

2017-11-01

Alkali plays a significant role in the formation of brittle layer of carbon brick in the blast furnace hearth. The brittle layer in a commercial blast furnace hearth was investigated. Large amounts of potassium compounds were found in the brittle layer. Subsequently, the carbon bricks which reacted with potassium in the simulation of blast furnace hearth under different contents of potassium in the brick (0.25, 0.5, 1.0 and 2.0 wt.%) during various reaction times (0.5, 1, 2 and 4 h) were experimentally studied. Finally, the formation mechanism of the brittle layer in carbon brick was clarified. The investigation results show that a large number of cracks are present in the brittle layer. The average potassium content in the brittle layer is 1 wt.%. According to the experimental results, cracks in the carbon brick can be formed by the attack of potassium. The reason for the formation of the brittle layer in the carbon brick is that the liquid potassium permeates into the carbon brick through the pores and cracks, and then reacts with SiO2 and Al2O3 in CO atmosphere. The generated potassium compounds nepheline and leucite lead to the volume expansion and the damage of the carbon brick.

Pore Polarity and Charge Determine Differential Block of Kir1.1 and Kir7.1 Potassium Channels by Small-Molecule Inhibitor VU590.

PubMed

Kharade, Sujay V; Sheehan, Jonathan H; Figueroa, Eric E; Meiler, Jens; Denton, Jerod S

2017-09-01

VU590 was the first publicly disclosed, submicromolar-affinity (IC 50 = 0.2 μ M), small-molecule inhibitor of the inward rectifier potassium (Kir) channel and diuretic target, Kir1.1. VU590 also inhibits Kir7.1 (IC 50 ∼ 8 μ M), and has been used to reveal new roles for Kir7.1 in regulation of myometrial contractility and melanocortin signaling. Here, we employed molecular modeling, mutagenesis, and patch clamp electrophysiology to elucidate the molecular mechanisms underlying VU590 inhibition of Kir1.1 and Kir7.1. Block of both channels is voltage- and K + -dependent, suggesting the VU590 binding site is located within the pore. Mutagenesis analysis in Kir1.1 revealed that asparagine 171 (N171) is the only pore-lining residue required for high-affinity block, and that substituting negatively charged residues (N171D, N171E) at this position dramatically weakens block. In contrast, substituting a negatively charged residue at the equivalent position in Kir7.1 enhances block by VU590, suggesting the VU590 binding mode is different. Interestingly, mutations of threonine 153 (T153) in Kir7.1 that reduce constrained polarity at this site (T153C, T153V, T153S) make wild-type and binding-site mutants (E149Q, A150S) more sensitive to block by VU590. The Kir7.1-T153C mutation enhances block by the structurally unrelated inhibitor VU714 but not by a higher-affinity analog ML418, suggesting that the polar side chain of T153 creates a barrier to low-affinity ligands that interact with E149 and A150. Reverse mutations in Kir1.1 suggest that this mechanism is conserved in other Kir channels. This study reveals a previously unappreciated role of membrane pore polarity in determination of Kir channel inhibitor pharmacology. Copyright © 2017 by The American Society for Pharmacology and Experimental Therapeutics.

Potassium sensing histidine kinase in Bacillus subtilis.

PubMed

López, Daniel; Gontang, Erin A; Kolter, Roberto

2010-01-01

The soil-dwelling organism Bacillus subtilis is able to form multicellular aggregates known as biofilms. It was recently reported that the process of biofilm formation is activated in response to the presence of various, structurally diverse small-molecule natural products. All of these small-molecule natural products made pores in the membrane of the bacterium, causing the leakage of potassium cations from the cytoplasm of the cell. The potassium cation leakage was sensed by the membrane histidine kinase KinC, triggering the genetic pathway to the production of the extracellular matrix that holds cells within the biofilm. This chapter presents the methodology used to characterize the leakage of cytoplasmic potassium as the signal that induces biofilm formation in B. subtilis via activation of KinC. Development of novel techniques to monitor activation of gene expression in microbial populations led us to discover the differentiation of a subpopulation of cells specialized to produce the matrix that holds all cells together within the biofilm. This phenomenon of cell differentiation was previously missed by conventional techniques used to monitor transcriptional gene expression. Copyright © 2010 Elsevier Inc. All rights reserved.

A High-Energy-Density Potassium Battery with a Polymer-Gel Electrolyte and a Polyaniline Cathode.

PubMed

Gao, Hongcai; Xue, Leigang; Xin, Sen; Goodenough, John B

2018-05-04

A safe, rechargeable potassium battery of high energy density and excellent cycling stability has been developed. The anion component of the electrolyte salt is inserted into a polyaniline cathode upon charging and extracted from it during discharging while the K + ion of the KPF 6 salt is plated/stripped on the potassium-metal anode. The use of a p-type polymer cathode increases the cell voltage. By replacing the organic-liquid electrolyte in a glass-fiber separator with a polymer-gel electrolyte of cross-linked poly(methyl methacrylate), a dendrite-free potassium anode can be plated/stripped, and the electrode/electrolyte interface is stabilized. The potassium anode wets the polymer, and the cross-linked architecture provides small pores of adjustable sizes to stabilize a solid-electrolyte interphase formed at the anode/electrolyte interface. This alternative electrolyte/cathode strategy offers a promising new approach to low-cost potassium batteries for the stationary storage of electric power. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preparation of activated carbons from corn cob catalyzed by potassium salts and subsequent gasification with CO2.

PubMed

Tsai, W T; Chang, C Y; Wang, S Y; Chang, C F; Chien, S F; Sun, H F

2001-06-01

In the present study, granular activated carbons were prepared from agricultural waste corn cob by chemical activation with potassium salts and/or physical activation with CO2. Under the experimental conditions investigated, potassium hydroxide (KOH) and potassium carbonate (K2CO3) were effective activating agents for chemical activation during a ramping period of 10 degrees C/min and subsequent gasification (i.e., physical activation) at a soaking period of 800 degrees C. Large BET surface areas (>1,600 m2/g) of activated carbons were thus obtained by the combined activation. In addition, this study clearly showed that the porosity created in the acid-unwashed carbon products is substantially lower than that of acid-washed carbon products due to potassium salts left in the pore structure.

Poring over two-pore channel pore mutants

PubMed Central

Penny, Christopher J.; Patel, Sandip

2016-01-01

Two-pore channels are members of the voltage-gated ion channel superfamily. They localise to the endolysosomal system and are likely targets for the Ca2+ mobilising messenger NAADP. In this brief review, we relate mutagenesis of the TPC pore to a recently published homology model and discuss how pore mutants are informing us of TPC function. Molecular physiology of these ubiquitous proteins is thus emerging. PMID:27226934

Degradation of progestagens by oxidation with potassium permanganate in wastewater effluents.

PubMed

Fayad, Paul B; Zamyadi, Arash; Broseus, Romain; Prévost, Michèle; Sauvé, Sébastien

2013-01-01

This study investigated the oxidation of selected progestagenic steroid hormones by potassium permanganate at pH 6.0 and 8.0 in ultrapure water and wastewater effluents, using bench-scale assays. Second order rate constants for the reaction of potassium permanganate with progestagens (levonorgestrel, medroxyprogesterone, norethindrone and progesterone) was determined as a function of pH, presence of natural organic matter and temperature. This work also illustrates the advantages of using a novel analytical method, the laser diode thermal desorption (LDTD-APCI) interface coupled to tandem mass spectrometry apparatus, allowing for the quick determination of oxidation rate constants and increasing sample throughput. The second-order rate constants for progestagens with permanganate determined in bench-scale experiments ranged from 23 to 368 M(-1) sec(-1) in both wastewater and ultrapure waters with pH values of 6.0 and 8.0. Two pairs of progestagens exhibited similar reaction rate constants, i.e. progesterone and medroxyprogesterone (23 to 80 M(-1) sec(-1) in ultrapure water and 26 to 149 M(-1) sec(-1) in wastewaters, at pH 6.0 and 8.0) and levonorgestrel and norethindrone (179 to 224 M(-1) sec(-1) in ultrapure water and 180 to 368 M(-1) sec(-1) in wastewaters, at pH 6.0 and 8.0). The presence of dissolved natural organic matter and the pH conditions improved the oxidation rate constants for progestagens with potassium permanganate only at alkaline pH. Reaction rates measured in Milli-Q water could therefore be used to provide conservative estimates for the oxidation rates of the four selected progestagens in wastewaters when exposed to potassium permanganate. The progestagen removal efficiencies was lower for progesterone and medroxyprogesterone (48 to 87 %) than for levonorgestrel and norethindrone (78 to 97%) in Milli-Q and wastewaters at pH 6.0-8.2 using potassium permanganate dosages of 1 to 5 mg L(-1) after contact times of 10 to 60 min. This

Degradation of progestagens by oxidation with potassium permanganate in wastewater effluents

PubMed Central

2013-01-01

Background This study investigated the oxidation of selected progestagenic steroid hormones by potassium permanganate at pH 6.0 and 8.0 in ultrapure water and wastewater effluents, using bench-scale assays. Second order rate constants for the reaction of potassium permanganate with progestagens (levonorgestrel, medroxyprogesterone, norethindrone and progesterone) was determined as a function of pH, presence of natural organic matter and temperature. This work also illustrates the advantages of using a novel analytical method, the laser diode thermal desorption (LDTD-APCI) interface coupled to tandem mass spectrometry apparatus, allowing for the quick determination of oxidation rate constants and increasing sample throughput. Results The second-order rate constants for progestagens with permanganate determined in bench-scale experiments ranged from 23 to 368 M-1 sec-1 in both wastewater and ultrapure waters with pH values of 6.0 and 8.0. Two pairs of progestagens exhibited similar reaction rate constants, i.e. progesterone and medroxyprogesterone (23 to 80 M-1 sec-1 in ultrapure water and 26 to 149 M-1 sec-1 in wastewaters, at pH 6.0 and 8.0) and levonorgestrel and norethindrone (179 to 224 M-1 sec-1 in ultrapure water and 180 to 368 M-1 sec-1 in wastewaters, at pH 6.0 and 8.0). The presence of dissolved natural organic matter and the pH conditions improved the oxidation rate constants for progestagens with potassium permanganate only at alkaline pH. Reaction rates measured in Milli-Q water could therefore be used to provide conservative estimates for the oxidation rates of the four selected progestagens in wastewaters when exposed to potassium permanganate. The progestagen removal efficiencies was lower for progesterone and medroxyprogesterone (48 to 87 %) than for levonorgestrel and norethindrone (78 to 97%) in Milli-Q and wastewaters at pH 6.0-8.2 using potassium permanganate dosages of 1 to 5 mg L-1 after contact times of 10 to 60�

Differences in Purinergic Amplification of Osmotic Cell Lysis by the Pore-Forming RTX Toxins Bordetella pertussis CyaA and Actinobacillus pleuropneumoniae ApxIA: the Role of Pore Size

PubMed Central

Fiser, Radovan; Linhartova, Irena; Osicka, Radim; Bumba, Ladislav; Hewlett, Erik L.; Benz, Roland; Sebo, Peter

2013-01-01

A large subgroup of the repeat in toxin (RTX) family of leukotoxins of Gram-negative pathogens consists of pore-forming hemolysins. These can permeabilize mammalian erythrocytes (RBCs) and provoke their colloid osmotic lysis (hemolytic activity). Recently, ATP leakage through pannexin channels and P2X receptor-mediated opening of cellular calcium and potassium channels were implicated in cell permeabilization by pore-forming toxins. In the study described here, we examined the role played by purinergic signaling in the cytolytic action of two RTX toxins that form pores of different sizes. The cytolytic potency of ApxIA hemolysin of Actinobacillus pleuropneumoniae, which forms pores about 2.4 nm wide, was clearly reduced in the presence of P2X7 receptor antagonists or an ATP scavenger, such as pyridoxalphosphate-6-azophenyl-2′,4′-disulfonic acid (PPADS), Brilliant Blue G, ATP oxidized sodium salt, or hexokinase. In contrast, antagonists of purinergic signaling had no impact on the hemolytic potency of the adenylate cyclase toxin-hemolysin (CyaA) of Bordetella pertussis, which forms pores of 0.6 to 0.8 nm in diameter. Moreover, the conductance of pores formed by ApxIA increased with the toxin concentration, while the conductance of the CyaA single pore units was constant at various toxin concentrations. However, the P2X7 receptor antagonist PPADS inhibited in a concentration-dependent manner the exacerbated hemolytic activity of a CyaA-ΔN489 construct (lacking 489 N-terminal residues of CyaA), which exhibited a strongly enhanced pore-forming propensity (>20-fold) and also formed severalfold larger conductance units in planar lipid bilayers than intact CyaA. These results point to a pore size threshold of purinergic amplification involvement in cell permeabilization by pore-forming RTX toxins. PMID:24082076

A new pH-sensitive rectifying potassium channel in mitochondria from the embryonic rat hippocampus.

PubMed

Kajma, Anna; Szewczyk, Adam

2012-10-01

Patch-clamp single-channel studies on mitochondria isolated from embryonic rat hippocampus revealed the presence of two different potassium ion channels: a large-conductance (288±4pS) calcium-activated potassium channel and second potassium channel with outwardly rectifying activity under symmetric conditions (150/150mM KCl). At positive voltages, this channel displayed a conductance of 67.84pS and a strong voltage dependence at holding potentials from -80mV to +80mV. The open probability was higher at positive than at negative voltages. Patch-clamp studies at the mitoplast-attached mode showed that the channel was not sensitive to activators and inhibitors of mitochondrial potassium channels but was regulated by pH. Moreover, we demonstrated that the channel activity was not affected by the application of lidocaine, an inhibitor of two-pore domain potassium channels, or by tertiapin, an inhibitor of inwardly rectifying potassium channels. In summary, based on the single-channel recordings, we characterised for the first time mitochondrial pH-sensitive ion channel that is selective for cations, permeable to potassium ions, displays voltage sensitivity and does not correspond to any previously described potassium ion channels in the inner mitochondrial membrane. This article is part of a Special Issue entitled: 17th European Bioenergetics Conference (EBEC 2012). Copyright © 2012 Elsevier B.V. All rights reserved.

Potassium dynamics and seizures: Why is potassium ictogenic?

PubMed

de Curtis, Marco; Uva, Laura; Gnatkovsky, Vadym; Librizzi, Laura

2018-07-01

Potassium channels dysfunction and altered genes encoding for molecules involved in potassium homeostasis have been associated with human epilepsy. These observations are in agreement with a control role of extracellular potassium on neuronal excitability and seizure generation. Epileptiform activity, in turn, regulates potassium homeostasis through mechanisms that are still not well established. We review here how potassium-associated processes are regulated in the brain and examine the mechanisms that support the role of potassium in triggering epileptiform activities. Copyright © 2018 Elsevier B.V. All rights reserved.

Potassium

MedlinePlus

... disease with vomiting and diarrhea) and drugs, especially diuretics ('water pills'), remove potassium from the body. Potassium ... captopril (Capoten), enalapril (Vasotec),and lisinopril (Prinivil, Zestril); diuretics ('water pills'); and vitamins. Do not take potassium ...

Permeation of protons, potassium ions, and small polar molecules through phospholipid bilayers as a function of membrane thickness.

PubMed Central

Paula, S; Volkov, A G; Van Hoek, A N; Haines, T H; Deamer, D W

1996-01-01

Two mechanisms have been proposed to account for solute permeation of lipid bilayers. Partitioning into the hydrophobic phase of the bilayer, followed by diffusion, is accepted by many for the permeation of water and other small neutral solutes, but transient pores have also been proposed to account for both water and ionic solute permeation. These two mechanisms make distinctively different predictions about the permeability coefficient as a function of bilayer thickness. Whereas the solubility-diffusion mechanism predicts only a modest variation related to bilayer thickness, the pore model predicts an exponential relationship. To test these models, we measured the permeability of phospholipid bilayers to protons, potassium ions, water, urea, and glycerol. Bilayers were prepared as liposomes, and thickness was varied systematically by using unsaturated lipids with chain lengths ranging from 14 to 24 carbon atoms. The permeability coefficient of water and neutral polar solutes displayed a modest dependence on bilayer thickness, with an approximately linear fivefold decrease as the carbon number varied from 14 to 24 atoms. In contrast, the permeability to protons and potassium ions decreased sharply by two orders of magnitude between 14 and 18 carbon atoms, and leveled off, when the chain length was further extended to 24 carbon atoms. The results for water and the neutral permeating solutes are best explained by the solubility-diffusion mechanism. The results for protons and potassium ions in shorter-chain lipids are consistent with the transient pore model, but better fit the theoretical line predicted by the solubility-diffusion model at longer chain lengths. PMID:8770210

Permeation of protons, potassium ions, and small polar molecules through phospholipid bilayers as a function of membrane thickness

NASA Technical Reports Server (NTRS)

Paula, S.; Volkov, A. G.; Van Hoek, A. N.; Haines, T. H.; Deamer, D. W.

1996-01-01

Two mechanisms have been proposed to account for solute permeation of lipid bilayers. Partitioning into the hydrophobic phase of the bilayer, followed by diffusion, is accepted by many for the permeation of water and other small neutral solutes, but transient pores have also been proposed to account for both water and ionic solute permeation. These two mechanisms make distinctively different predictions about the permeability coefficient as a function of bilayer thickness. Whereas the solubility-diffusion mechanism predicts only a modest variation related to bilayer thickness, the pore model predicts an exponential relationship. To test these models, we measured the permeability of phospholipid bilayers to protons, potassium ions, water, urea, and glycerol. Bilayers were prepared as liposomes, and thickness was varied systematically by using unsaturated lipids with chain lengths ranging from 14 to 24 carbon atoms. The permeability coefficient of water and neutral polar solutes displayed a modest dependence on bilayer thickness, with an approximately linear fivefold decrease as the carbon number varied from 14 to 24 atoms. In contrast, the permeability to protons and potassium ions decreased sharply by two orders of magnitude between 14 and 18 carbon atoms, and leveled off, when the chain length was further extended to 24 carbon atoms. The results for water and the neutral permeating solutes are best explained by the solubility-diffusion mechanism. The results for protons and potassium ions in shorter-chain lipids are consistent with the transient pore model, but better fit the theoretical line predicted by the solubility-diffusion model at longer chain lengths.

Claudin-2-mediated cation and water transport share a common pore

PubMed Central

Rosenthal, Rita; Günzel, Dorothee; Krug, Susanne M.; Schulzke, Jörg-Dieter; Fromm, Michael; Yu, Alan S.L.

2016-01-01

Aim Claudin-2 is a tight junction protein typically located in “leaky” epithelia exhibiting large paracellular permeabilities like small intestine and proximal kidney tubule. Former studies revealed that claudin-2 forms paracellular channels for small cations like sodium and potassium and also paracellular channels for water. This study analyzes whether the diffusive transport of sodium and water occurs through a common pore of the claudin-2 channel. Methods Wild-type claudin-2 and different claudin-2 mutants were expressed in MDCK I kidney tubule cells using an inducible system. Ion and water permeability and the effect of blocking reagents on both were investigated on different clones of the mutants. Results Neutralization of a negatively charged cation interaction site in the pore with the mutation, D65N, decreased both, sodium permeability and water permeability. Claudin-2 mutants (I66C and S68C) with substitution of the pore-lining amino acids with cysteine were used to test the effect of steric blocking of the claudin-2 pore by thiol-reactive reagents. Addition of thiol-reactive reagents to these mutants simultaneously decreased conductance and water permeability. Remarkably, all experimental perturbations caused parallel changes in ion conductance and water permeability, disproving different or independent passage pathways. Conclusion Our results indicate that claudin-2-mediated cation and water transport are frictionally coupled and share a common pore. This pore is lined and determined in permeability by amino acid residues of the first extracellular loop of claudin-2. PMID:27359349

Enhanced water transport and salt rejection through hydrophobic zeolite pores.

PubMed

Humplik, Thomas; Lee, Jongho; O'Hern, Sean; Laoui, Tahar; Karnik, Rohit; Wang, Evelyn N

2017-12-15

The potential of improvements to reverse osmosis (RO) desalination by incorporating porous nanostructured materials such as zeolites into the selective layer in the membrane has spurred substantial research efforts over the past decade. However, because of the lack of methods to probe transport across these materials, it is still unclear which pore size or internal surface chemistry is optimal for maximizing permeability and salt rejection. We developed a platform to measure the transport of water and salt across a single layer of zeolite crystals, elucidating the effects of internal wettability on water and salt transport through the ≈5.5 Å pores of MFI zeolites. MFI zeolites with a more hydrophobic (i.e., less attractive) internal surface chemistry facilitated an approximately order of magnitude increase in water permeability compared to more hydrophilic MFI zeolites, while simultaneously fully rejecting both potassium and chlorine ions. However, our results also demonstrated approximately two orders of magnitude lower permeability compared to molecular simulations. This decreased performance suggests that additional transport resistances (such as surface barriers, pore collapse or blockages due to contamination) may be limiting the performance of experimental nanostructured membranes. Nevertheless, the inclusion of hydrophobic sub-nanometer pores into the active layer of RO membranes should improve both the water permeability and salt rejection of future RO membranes (Fasano et al 2016 Nat. Commun. 7 12762).

Enhanced water transport and salt rejection through hydrophobic zeolite pores

NASA Astrophysics Data System (ADS)

Humplik, Thomas; Lee, Jongho; O'Hern, Sean; Laoui, Tahar; Karnik, Rohit; Wang, Evelyn N.

2017-12-01

The potential of improvements to reverse osmosis (RO) desalination by incorporating porous nanostructured materials such as zeolites into the selective layer in the membrane has spurred substantial research efforts over the past decade. However, because of the lack of methods to probe transport across these materials, it is still unclear which pore size or internal surface chemistry is optimal for maximizing permeability and salt rejection. We developed a platform to measure the transport of water and salt across a single layer of zeolite crystals, elucidating the effects of internal wettability on water and salt transport through the ≈5.5 Å pores of MFI zeolites. MFI zeolites with a more hydrophobic (i.e., less attractive) internal surface chemistry facilitated an approximately order of magnitude increase in water permeability compared to more hydrophilic MFI zeolites, while simultaneously fully rejecting both potassium and chlorine ions. However, our results also demonstrated approximately two orders of magnitude lower permeability compared to molecular simulations. This decreased performance suggests that additional transport resistances (such as surface barriers, pore collapse or blockages due to contamination) may be limiting the performance of experimental nanostructured membranes. Nevertheless, the inclusion of hydrophobic sub-nanometer pores into the active layer of RO membranes should improve both the water permeability and salt rejection of future RO membranes (Fasano et al 2016 Nat. Commun. 7 12762).

The exocytotic fusion pore modeled as a lipidic pore.

PubMed Central

Nanavati, C; Markin, V S; Oberhauser, A F; Fernandez, J M

1992-01-01

Freeze-fracture electron micrographs from degranulating cells show that the lumen of the secretory granule is connected to the extracellular compartment via large (20 to 150 nm diameter) aqueous pores. These exocytotic fusion pores appear to be made up of a highly curved bilayer that spans the plasma and granule membranes. Conductance measurements, using the patch-clamp technique, have been used to study the fusion pore from the instant it conducts ions. These measurements reveal the presence of early fusion pores that are much smaller than those observed in electron micrographs. Early fusion pores open abruptly, fluctuate, and then either expand irreversibly or close. The molecular structure of these early fusion pores is unknown. In the simplest extremes, these early fusion pores could be either ion channel like protein pores or lipidic pores. Here, we explored the latter possibility, namely that of the early exocytotic fusion pore modeled as a lipid-lined pore whose free energy was composed of curvature elastic energy and work done by tension. Like early exocytotic fusion pores, we found that these lipidic pores could open abruptly, fluctuate, and expand irreversibly. Closure of these lipidic pores could be caused by slight changes in lipid composition. Conductance distributions for stable lipidic pores matched those of exocytotic fusion pores. These findings demonstrate that lipidic pores can exhibit the properties of exocytotic fusion pores, thus providing an alternate framework with which to understand and interpret exocytotic fusion pore data. PMID:1420930

Voltage-Gated Potassium Channels: A Structural Examination of Selectivity and Gating

PubMed Central

Kim, Dorothy M.; Nimigean, Crina M.

2016-01-01

Voltage-gated potassium channels play a fundamental role in the generation and propagation of the action potential. The discovery of these channels began with predictions made by early pioneers, and has culminated in their extensive functional and structural characterization by electrophysiological, spectroscopic, and crystallographic studies. With the aid of a variety of crystal structures of these channels, a highly detailed picture emerges of how the voltage-sensing domain reports changes in the membrane electric field and couples this to conformational changes in the activation gate. In addition, high-resolution structural and functional studies of K+ channel pores, such as KcsA and MthK, offer a comprehensive picture on how selectivity is achieved in K+ channels. Here, we illustrate the remarkable features of voltage-gated potassium channels and explain the mechanisms used by these machines with experimental data. PMID:27141052

47 CFR 69.111 - Tandem-switched transport and tandem charge.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 3 2011-10-01 2011-10-01 false Tandem-switched transport and tandem charge. 69... SERVICES (CONTINUED) ACCESS CHARGES Computation of Charges § 69.111 Tandem-switched transport and tandem...-switched transport shall consist of two rate elements, a transmission charge and a tandem switching charge...

Plasma potassium and diurnal cyclic potassium excretion in the rat.

PubMed

Rabinowitz, L; Berlin, R; Yamauchi, H

1987-12-01

The relation of the plasma potassium concentration to the daily cyclic variation in potassium excretion was examined in undisturbed, unanesthetized male Sprague-Dawley rats maintained on a liquid diet in a 12-h light-dark environment. Potassium excretion increased from a light-phase minimum of 16 mu eq/h to a peak of 256 mu eq/h 3 h after the beginning of the dark phase. Plasma potassium concentration in arterial blood, sampled in rats at 90-min intervals during these changes in potassium excretion, showed no significant change and was in the range 4.50-4.99 meq/liter. In adrenalectomized rats receiving aldosterone and dexamethasone at constant basal rates by implanted pumps, the daily cycle of potassium excretion was the same as in the intact rats, and plasma potassium was not significantly different when measured at the time of minimum and maximum rates of potassium excretion (4.79 +/- 0.42 vs 5.16 +/- 0.47 meq/liter, mean +/- SD). These results indicate that plasma potassium concentration is not the efferent factor controlling diurnal cyclic changes in potassium excretion in adrenal intact rats and may not be the only significant factor in adrenalectomized-steroid replaced rats.

Lactococcin G is a potassium ion-conducting, two-component bacteriocin.

PubMed

Moll, G; Ubbink-Kok, T; Hildeng-Hauge, H; Nissen-Meyer, J; Nes, I F; Konings, W N; Driessen, A J

1996-02-01

Lactococcin G is a novel lactococcal bacteriocin whose activity depends on the complementary action of two peptides, termed alpha and beta. Peptide synthesis of the alpha and beta peptides yielded biologically active lactococcin G, which was used in mode-of-action studies on sensitive cells of Lactococcus lactis. Approximately equivalent amounts of both peptides were required for optimal bactericidal effect. No effect was observed with either the alpha or beta peptide in the absence of the complementary peptide. The combination of alpha and beta peptides (lactococcin G) dissipates the membrane potential (delta omega), and as a consequence cells release alpha-aminoisobutyrate, a non-metabolizable alanine analog that is accumulated through a proton motive-force dependent mechanism. In addition, the cellular ATP level is dramatically reduced, which results in a drastic decrease of the ATP-driven glutamate uptake. Lactococcin G does not form a proton-conducting pore, as it has no effect on the transmembrane pH gradient. Dissipation of the membrane potential by uncouplers causes a slow release of potassium (rubidium) ions. However, rapid release of potassium was observed in the presence of lactococcin G. These data suggest that the bactericidal effect of lactococcin G is due to the formation of potassium-selective channels by the alpha and beta peptides in the target bacterial membrane.

Study of the interaction of potassium ion channel protein with micelle by molecular dynamics simulation

NASA Astrophysics Data System (ADS)

Shantappa, Anil; Talukdar, Keka

2018-04-01

Ion channels are proteins forming pore inside the body of all living organisms. This potassium ion channel known as KcsA channel and it is found in the each cell and nervous system. Flow of various ions is regulated by the function of the ion channels. The nerve ion channel protein with protein data bank entry 1BL8, which is basically an ion channel protein in Streptomyces Lividans and which is taken up to form micelle-protein system and the system is analyzed by using molecular dynamics simulation. Firstly, ion channel pore is engineered by CHARMM potential and then Micelle-protein system is subjected to molecular dynamics simulation. For some specific micelle concentration, the protein unfolding is observed.

Soil transport parameters of potassium under a tropical saline soil condition using STANMOD

NASA Astrophysics Data System (ADS)

Suzanye da Silva Santos, Rafaelly; Honorio de Miranda, Jarbas; Previatello da Silva, Livia

2015-04-01

Environmental responsibility and concerning about the final destination of solutes in soil, so more studies allow a better understanding about the solutes behaviour in soil. Potassium is a macronutrient that is required in high concentrations, been an extremely important nutrient for all agricultural crops. It plays essential roles in physiological processes vital for plant growth, from protein synthesis to maintenance of plant water balance, and is available to plants dissolved in soil water while exchangeable K is loosely held on the exchange sites on the surface of clay particles. K will tend to be adsorbed onto the surface of negatively charged soil particles. Potassium uptake is vital for plant growth but in saline soils sodium competes with potassium for uptake across the plasma membrane of plant cells. This can result in high Na+:K+ ratios that reduce plant growth and eventually become toxic. This study aimed to obtain soil transport parameters of potassium in saline soil, such as: pore water velocity in soil (v), retardation factor (R), dispersivity (λ) and dispersion coefficient (D), in a disturbed sandy soil with different concentrations of potassium chlorate solution (KCl), which is one of the most common form of potassium fertilizer. The experiment was carried out using soil samples collected in a depth of 0 to 20 cm, applying potassium chlorate solution containing 28.6, 100, 200 and 500 mg L-1 of K. To obtain transport parameters, the data were adjusted with the software STANMOD. At low concentrations, interaction between potassium and soil occur more efficiently. It was observed that only the breakthrough curve prepared with solution of 500 mg L-1 reached the applied concentration, and the solution of 28.6 mg L-1 overestimated the parameters values. The STANMOD proved to be efficient in obtaining potassium transport parameters; KCl solution to be applied should be greater than 500 mg L-1; solutions with low concentrations tend to overestimate

Potassium Counts.

ERIC Educational Resources Information Center

Gipps, John

1995-01-01

Presents an activity to determine whether the radioactivity of a pure potassium salt is directly proportional to the amount of potassium in it and whether this could be used as a method of analysis for potassium in a solid. (MKR)

Potassium Secondary Batteries.

PubMed

Eftekhari, Ali; Jian, Zelang; Ji, Xiulei

2017-02-08

Potassium may exhibit advantages over lithium or sodium as a charge carrier in rechargeable batteries. Analogues of Prussian blue can provide millions of cyclic voltammetric cycles in aqueous electrolyte. Potassium intercalation chemistry has recently been demonstrated compatible with both graphite and nongraphitic carbons. In addition to potassium-ion batteries, potassium-O 2 (or -air) and potassium-sulfur batteries are emerging. Additionally, aqueous potassium-ion batteries also exhibit high reversibility and long cycling life. Because of potentially low cost, availability of basic materials, and intriguing electrochemical behaviors, this new class of secondary batteries is attracting much attention. This mini-review summarizes the current status, opportunities, and future challenges of potassium secondary batteries.

Potassium in diet

MedlinePlus

... the diet; Hypokalemia - potassium in the diet; Chronic kidney disease - potassium in diet; Kidney failure - potassium in diet ... are also excellent sources of potassium. People with kidney problems, especially those on dialysis, should not eat ...

Low Potassium (Hypokalemia)

MedlinePlus

Symptoms Low potassium (hypokalemia) By Mayo Clinic Staff Low potassium (hypokalemia) refers to a lower than normal potassium level ... 2 millimoles per liter (mmol/L). A very low potassium level (less than 2.5 mmol/L) ...

Serum potassium level and dietary potassium intake as risk factors for stroke.

PubMed

Green, D M; Ropper, A H; Kronmal, R A; Psaty, B M; Burke, G L

2002-08-13

Numerous studies have found that low potassium intake and low serum potassium are associated with increased stroke mortality, but data regarding stroke incidence have been limited. Serum potassium levels, dietary potassium intake, and diuretic use in relation to risk for stroke in a prospectively studied cohort were investigated. The study comprised 5,600 men and women older than 65 years who were free of stroke at enrollment. Baseline data included serum potassium level, dietary potassium intake, and diuretic use. Participants were followed for 4 to 8 years, and the incidence and types of strokes were recorded. Low serum potassium was defined as less than 4.1 mEq/L, and low potassium intake as less than 2.4 g/d. Among diuretic users, there was an increased risk for stroke associated with lower serum potassium (relative risk [RR]: 2.5, p < 0.0001). Among individuals not taking diuretics, there was an increased risk for stroke associated with low dietary potassium intake (RR: 1.5, p < 0.005). The small number of diuretic users with lower serum potassium and atrial fibrillation had a 10-fold greater risk for stroke compared with those with higher serum potassium and normal sinus rhythm. A lower serum potassium level in diuretic users, and low potassium intake in those not taking diuretics were associated with increased stroke incidence among older individuals. Lower serum potassium was associated with a particularly high risk for stroke in the small number of diuretic users with atrial fibrillation. Further study is required to determine if modification of these factors would prevent strokes.

Potassium

MedlinePlus

... Guidelines for Americans and the U.S. Department of Agriculture’s MyPlate . Where can I find out more about ... on food sources of potassium: U.S. Department of Agriculture’s (USDA) National Nutrient Database Nutrient List for potassium ( ...

Sediment-pore water interactions controlling cementation in the NanTroSEIZE drilling transects

NASA Astrophysics Data System (ADS)

Hong, W.; Spinelli, G. A.; Torres, M. E.

2012-12-01

One goal of the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) is to understand how changes in subducting sediment control the transition from aseismic to seismogenic behavior in subduction zones. In the sediment entering the Nankai subduction zone, dramatic changes in physical and chemical properties occur across a diagenetic boundary; they are thought to affect sediment strength and deformation. The dissolution of disseminated volcanic ash and precipitation of silica cement may be responsible for these changes in physical properties, but the mechanism controlling cementation was unclear (Spinelli et al., 2007). In this study, we used CrunchFlow (Steefel, 2009) to simulate chemical reactions and fluid flow through 1-D sediment columns at Integrated Ocean Drilling Program (IODP) sites on the incoming plate in Nankai Trough. The simulations include the thermodynamics and kinetics of sediment-water interactions, advection of pore water and sediment due to compaction, and multi-component diffusion in an accumulating sediment column. Key reactions in the simulations are: ash dissolution, amorphous silica precipitation and dissolution, and zeolite precipitation. The rate of ash decomposition was constrained using Sr isotope data of Joseph et al. (2012). Our model reproduces the distinct diagenetic boundary observed in sediment and pore water chemistry, which defines two zones. Above this boundary (zone 1), dissolved and amorphous silicate contents are high and the potassium concentration remains near seawater values or gradually decreases toward the boundary. Below the boundary, both dissolved and amorphous silicate content drop rapidly, concomitant with a decrease in dissolved potassium. Our model shows that these changes in the system are driven by formation of clinoptilolite in response to changes in pore fluid pH. The low pH values (<7.6) above the diagenetic boundary accelerate ash decomposition and maintain clinoptilolite slightly undersaturated. The

Potassium Beta-Alumina/Molybdenum/Potassium Electrochemical Cells

NASA Technical Reports Server (NTRS)

Williams, R.; Kisor, A.; Ryan, M.; Nakamura, B.; Kikert, S.; O'Connor, D.

1994-01-01

potassium alkali metal thermal-to-electric converter (K-AMTEC) cells utilizing potassium beta alumina solid electrolyte (K-BASE) are predicted to have improved properties for thermal to electric conversion at somewhat lower temperatures than sodium AMTEC's.

Potassium vapor assisted preparation of highly graphitized hierarchical porous carbon for high rate performance supercapacitors

NASA Astrophysics Data System (ADS)

Liu, Zheng; Zeng, Ying; Tang, Qunli; Hu, Aiping; Xiao, Kuikui; Zhang, Shiying; Deng, Weina; Fan, Binbin; Zhu, Yanfei; Chen, Xiaohua

2017-09-01

Ultrahigh graphitized carbon microspheres with rich hierarchical pores (AGHPCM-1) have been successfully synthesized through the one-step activation-carbonization strategy (OACS) with porous sulfonated poly-divinylbenzene as the carbon precursor, iron as the hard template and catalyst, and potassium hydroxide (KOH) as activation agent. Through the XRD, TEM, Raman and BET analysis, AGHPCM-1 shows very high graphitization degree and rich micro-, meso- and macro-pores. More importantly, the mechanism for KOH to improve the graphitization degree of carbon materials in OACS has been illustrated by the thermodynamical theory. The tremendous heat releasing from the reaction between the catalyst precursor of Fe2O3 and potassium vapor plays a key role in the formation of graphitized carbon. It may provide a general direction to prepare highly graphitized porous carbon at a moderate temperature. Integrating the advantages of high graphitization degree and rich hierarchical porous structure, the AGHPCM-1 exhibits an excellent rate performance with a response to up to the high current density of 150 A g-1 and high scan rate of 2000 mV s-1. No obvious capacitance decay can be observed after 10000 charge/discharge cycles even at the high current density of 20 A g-1.

Neutralization of a single arginine residue gates open a two-pore domain, alkali-activated K+ channel

PubMed Central

Niemeyer, María Isabel; González-Nilo, Fernando D.; Zúñiga, Leandro; González, Wendy; Cid, L. Pablo; Sepúlveda, Francisco V.

2007-01-01

Potassium channels share a common selectivity filter that determines the conduction characteristics of the pore. Diversity in K+ channels is given by how they are gated open. TASK-2, TALK-1, and TALK-2 are two-pore region (2P) KCNK K+ channels gated open by extracellular alkalinization. We have explored the mechanism for this alkalinization-dependent gating using molecular simulation and site-directed mutagenesis followed by functional assay. We show that the side chain of a single arginine residue (R224) near the pore senses pH in TASK-2 with an unusual pKa of 8.0, a shift likely due to its hydrophobic environment. R224 would block the channel through an electrostatic effect on the pore, a situation relieved by its deprotonation by alkalinization. A lysine residue in TALK-2 fulfills the same role but with a largely unchanged pKa, which correlates with an environment that stabilizes its positive charge. In addition to suggesting unified alkaline pH-gating mechanisms within the TALK subfamily of channels, our results illustrate in a physiological context the principle that hydrophobic environment can drastically modulate the pKa of charged amino acids within a protein. PMID:17197424

MR-Tandem: parallel X!Tandem using Hadoop MapReduce on Amazon Web Services.

PubMed

Pratt, Brian; Howbert, J Jeffry; Tasman, Natalie I; Nilsson, Erik J

2012-01-01

MR-Tandem adapts the popular X!Tandem peptide search engine to work with Hadoop MapReduce for reliable parallel execution of large searches. MR-Tandem runs on any Hadoop cluster but offers special support for Amazon Web Services for creating inexpensive on-demand Hadoop clusters, enabling search volumes that might not otherwise be feasible with the compute resources a researcher has at hand. MR-Tandem is designed to drop in wherever X!Tandem is already in use and requires no modification to existing X!Tandem parameter files, and only minimal modification to X!Tandem-based workflows. MR-Tandem is implemented as a lightly modified X!Tandem C++ executable and a Python script that drives Hadoop clusters including Amazon Web Services (AWS) Elastic Map Reduce (EMR), using the modified X!Tandem program as a Hadoop Streaming mapper and reducer. The modified X!Tandem C++ source code is Artistic licensed, supports pluggable scoring, and is available as part of the Sashimi project at http://sashimi.svn.sourceforge.net/viewvc/sashimi/trunk/trans_proteomic_pipeline/extern/xtandem/. The MR-Tandem Python script is Apache licensed and available as part of the Insilicos Cloud Army project at http://ica.svn.sourceforge.net/viewvc/ica/trunk/mr-tandem/. Full documentation and a windows installer that configures MR-Tandem, Python and all necessary packages are available at this same URL. brian.pratt@insilicos.com

MR-Tandem: parallel X!Tandem using Hadoop MapReduce on Amazon Web Services

PubMed Central

Pratt, Brian; Howbert, J. Jeffry; Tasman, Natalie I.; Nilsson, Erik J.

2012-01-01

Summary: MR-Tandem adapts the popular X!Tandem peptide search engine to work with Hadoop MapReduce for reliable parallel execution of large searches. MR-Tandem runs on any Hadoop cluster but offers special support for Amazon Web Services for creating inexpensive on-demand Hadoop clusters, enabling search volumes that might not otherwise be feasible with the compute resources a researcher has at hand. MR-Tandem is designed to drop in wherever X!Tandem is already in use and requires no modification to existing X!Tandem parameter files, and only minimal modification to X!Tandem-based workflows. Availability and implementation: MR-Tandem is implemented as a lightly modified X!Tandem C++ executable and a Python script that drives Hadoop clusters including Amazon Web Services (AWS) Elastic Map Reduce (EMR), using the modified X!Tandem program as a Hadoop Streaming mapper and reducer. The modified X!Tandem C++ source code is Artistic licensed, supports pluggable scoring, and is available as part of the Sashimi project at http://sashimi.svn.sourceforge.net/viewvc/sashimi/trunk/trans_proteomic_pipeline/extern/xtandem/. The MR-Tandem Python script is Apache licensed and available as part of the Insilicos Cloud Army project at http://ica.svn.sourceforge.net/viewvc/ica/trunk/mr-tandem/. Full documentation and a windows installer that configures MR-Tandem, Python and all necessary packages are available at this same URL. Contact: brian.pratt@insilicos.com PMID:22072385

Cadmium-cysteine coordination in the BK inner pore region and its structural and functional implications.

PubMed

Zhou, Yu; Xia, Xiao-Ming; Lingle, Christopher J

2015-04-21

To probe structure and gating-associated conformational changes in BK-type potassium (BK) channels, we examined consequences of Cd(2+) coordination with cysteines introduced at two positions in the BK inner pore. At V319C, the equivalent of valine in the conserved Kv proline-valine-proline (PVP) motif, Cd(2+) forms intrasubunit coordination with a native glutamate E321, which would place the side chains of V319C and E321 much closer together than observed in voltage-dependent K(+) (Kv) channel structures, requiring that the proline between V319C and E321 introduces a kink in the BK S6 inner helix sharper than that observed in Kv channel structures. At inner pore position A316C, Cd(2+) binds with modest state dependence, suggesting the absence of an ion permeation gate at the cytosolic side of BK channel. These results highlight fundamental structural differences between BK and Kv channels in their inner pore region, which likely underlie differences in voltage-dependent gating between these channels.

The pungent substances piperine, capsaicin, 6-gingerol and polygodial inhibit the human two-pore domain potassium channels TASK-1, TASK-3 and TRESK

PubMed Central

Beltrán, Leopoldo R.; Dawid, Corinna; Beltrán, Madeline; Gisselmann, Guenter; Degenhardt, Katharina; Mathie, Klaus; Hofmann, Thomas; Hatt, Hanns

2013-01-01

For a long time, the focus of trigeminal chemoperception has rested almost exclusively on TRP channels. However, two-pore domain (K2P) potassium channels have recently been identified as targets for substances associated with typical trigeminal sensations, such as numbing and tingling. In addition, they have been shown to be modulated by several TRP agonists. We investigated whether the pungent substances piperine, capsaicin, 6-gingerol and polygodial have an effect on human K2P channels. For this purpose, we evaluated the effects of these pungent substances on both wild-type and mutant K2P channels by means of two-electrode voltage-clamp experiments using Xenopus laevis oocytes. All four pungent substances were found to inhibit the basal activity of TASK-1 (K2P 3.1), TASK-3 (K2P 9.1), and TRESK (K2P 18.1) channels. This inhibitory effect was dose-dependent and, with the exception of polygodial on TASK-1, fully reversible. However, only piperine exhibited an IC50 similar to its reported EC50 on TRP channels. Finally, we observed for TASK-3 that mutating H98 to E markedly decreased the inhibition induced by piperine, capsaicin, and 6-gingerol, but not by polygodial. Our data contribute to the relatively sparse knowledge concerning the pharmacology of K2P channels and also raise the question of whether K2P channels could be involved in the pungency perception of piperine. PMID:24302912

Closure of mitochondrial potassium channels favors opening of the Tl(+)-induced permeability transition pore in Ca(2+)-loaded rat liver mitochondria.

PubMed

Korotkov, Sergey M; Brailovskaya, Irina V; Shumakov, Anton R; Emelyanova, Larisa V

2015-06-01

It is known that a closure of ATP sensitive (mitoKATP) or BK-type Ca(2+) activated (mitoKCa) potassium channels triggers opening of the mitochondrial permeability transition pore (MPTP) in cells and isolated mitochondria. We found earlier that the Tl(+)-induced MPTP opening in Ca(2+)-loaded rat liver mitochondria was accompanied by a decrease of 2,4-dinitrophenol-uncoupled respiration and increase of mitochondrial swelling and ΔΨmito dissipation in the medium containing TlNO3 and KNO3. On the other hand, our study showed that the mitoKATP inhibitor, 5-hydroxydecanoate favored the Tl(+)-induced MPTP opening in the inner membrane of Ca(2+)-loaded rat heart mitochondria (Korotkov et al. 2013). Here we showed that 5-hydroxydecanoate increased the Tl(+)-induced MPTP opening in the membrane of rat liver mitochondria regardless of the presence of mitoKATP modulators (diazoxide and pinacidil). This manifested in more pronounced decrease in the uncoupled respiration and acceleration of both the swelling and the ΔΨmito dissipation in isolated rat liver mitochondria, incubated in the medium containing TlNO3, KNO3, and Ca(2+). A slight delay in Ca(2+)-induced swelling of the mitochondria exposed to diazoxide could be result of an inhibition of succinate oxidation by the mitoKATP modulator. Mitochondrial calcium retention capacity (CRC) was markedly decreased in the presence of the mitoKATP inhibitor (5-hydroxydecanoate) or the mitoKCa inhibitor (paxilline). We suggest that the closure of mitoKATP or mitoKCa in calcium loaded mitochondria favors opening of the Tl(+)-induced MPTP in the inner mitochondrial membrane.

Mechanism of Cd2+-coordination during Slow Inactivation in Potassium Channels

PubMed Central

Raghuraman, H.; Cordero-Morales, Julio F.; Jogini, Vishwanath; Pan, Albert C.; Kollewe, Astrid; Roux, Benoît; Perozo, Eduardo

2013-01-01

Summary In K+ channels, rearrangements of the pore outer-vestibule have been associated with C-type inactivation gating. Paradoxically, the crystal structure of Open/C-type inactivated KcsA suggest these movements to be modest in magnitude. Here, we show that under physiological conditions, the KcsA outer-vestibule undergoes relatively large dynamic rearrangements upon inactivation. External Cd2+ enhances the rate of C-type inactivation in an outer-vestibule cysteine mutant (Y82C) via metal-bridge formation. This effect is not present in a non-inactivating mutant (E71A/Y82C). Tandem dimer and tandem tetramer constructs of equivalent cysteine mutants in KcsA and Shaker K+ channels demonstrate that these Cd2+ metal bridges are formed only between adjacent subunits. This is well supported by molecular dynamics simulations. Based on the crystal structure of Cd2+-bound Y82C-KcsA in the closed state, together with EPR distance measurements in the KcsA outer-vestibule, we suggest that subunits must dynamically come in close proximity as the channels undergo inactivation. PMID:22771214

External Barium Affects the Gating of KCNQ1 Potassium Channels and Produces a Pore Block via Two Discrete Sites

PubMed Central

Gibor, Gilad; Yakubovich, Daniel; Peretz, Asher; Attali, Bernard

2004-01-01

The pore properties and the reciprocal interactions between permeant ions and the gating of KCNQ channels are poorly understood. Here we used external barium to investigate the permeation characteristics of homomeric KCNQ1 channels. We assessed the Ba2+ binding kinetics and the concentration and voltage dependence of Ba2+ steady-state block. Our results indicate that extracellular Ba2+ exerts a series of complex effects, including a voltage-dependent pore blockade as well as unique gating alterations. External barium interacts with the permeation pathway of KCNQ1 at two discrete and nonsequential sites. (a) A slow deep Ba2+ site that occludes the channel pore and could be simulated by a model of voltage-dependent block. (b) A fast superficial Ba2+ site that barely contributes to channel block and mostly affects channel gating by shifting rightward the voltage dependence of activation, slowing activation, speeding up deactivation kinetics, and inhibiting channel inactivation. A model of voltage-dependent block cannot predict the complex impact of Ba2+ on channel gating in low external K+ solutions. Ba2+ binding to this superficial site likely modifies the gating transitions states of KCNQ1. Both sites appear to reside in the permeation pathway as high external K+ attenuates Ba2+ inhibition of channel conductance and abolishes its impact on channel gating. Our data suggest that despite the high degree of homology of the pore region among the various K+ channels, KCNQ1 channels display significant structural and functional uniqueness. PMID:15226366

Potassium toxicity at low serum potassium levels with refeeding syndrome.

PubMed

Vemula, Praveen; Abela, Oliver G; Narisetty, Keerthy; Rhine, David; Abela, George S

2015-01-01

Refeeding syndrome is a life-threatening condition occurring in severely malnourished patients after initiating feeding. Severe hypophosphatemia with reduced adenosine triphosphate production has been implicated, but little data are available regarding electrolyte abnormalities. In this case, we report electrocardiographic changes consistent with hyperkalemia during potassium replacement after a serum level increase from 1.9 to 2.9 mEq/L. This was reversed by lowering serum potassium back to 2.0 mEq/L. In conclusion, the patient with prolonged malnutrition became adapted to low potassium levels and developed potassium toxicity with replacement. Copyright © 2015 Elsevier Inc. All rights reserved.

The structure of the lipid-embedded potassium channel voltage sensor determined by double-electron–electron resonance spectroscopy

PubMed Central

Vamvouka, Magdalini; Cieslak, John; Van Eps, Ned; Hubbell, Wayne; Gross, Adrian

2008-01-01

A four-pulse electron paramagnetic resonance experiment was used to measure long-range inter-subunit distances in reconstituted KvAP, a voltage-dependent potassium (Kv) channel. The measurements have allowed us to reach the following five conclusions about the native structure of the voltage sensor of KvAP. First, the S1 helix of the voltage sensor engages in a helix packing interaction with the pore domain. Second, the crystallographically observed antiparallel helix-turn-helix motif of the voltage-sensing paddle is retained in the membrane-embedded voltage sensor. Third, the paddle is oriented in such a way as to expose one face to the pore domain and the opposite face to the membrane. Fourth, the paddle and the pore domain appear to be separated by a gap that is sufficiently wide for lipids to penetrate between the two domains. Fifth, the critical voltage-sensing arginine residues on the paddle appear to be lipid exposed. These results demonstrate the importance of the membrane for the native structure of Kv channels, suggest that lipids are an integral part of their native structure, and place the voltage-sensing machinery into a complex lipid environment near the pore domain. PMID:18287283

Development of potassium ion conducting hollow glass fibers. [potassium sulfur battery

NASA Technical Reports Server (NTRS)

Tsang, F. Y.

1974-01-01

Potassium ion conducting glasses, chemically resistant to potassium, potassium sulfide and sulfur, were made and their possible utility as the membrane material for a potassium/sulfur battery was evaluated. At least one satisfactory candidate was found. It possesses an electrical resistance which makes it usable as a membrane in the form of a fine hollow fiber. It's chemical and electrochemical resistances are excellent. The other aspects of the possible potassium sulfur battery utilizing such fine hollow fibers, including the header (or tube sheet) and a cathode current collector were studied. Several cathode materials were found to be satisfactory. None of the tube sheet materials studied possessed all the desired properties. Multi-fiber cells had very limited life-time due to physical failure of fibers at the fiber/tube sheet junctions.

Dynamics of internal pore opening in KV channels probed by a fluorescent unnatural amino acid

PubMed Central

Kalstrup, Tanja; Blunck, Rikard

2013-01-01

Atomic-scale models on the gating mechanism of voltage-gated potassium channels (Kv) are based on linear interpolations between static structures of their initial and final state derived from crystallography and molecular dynamics simulations, and, thus, lack dynamic structural information. The lack of information on dynamics and intermediate states makes it difficult to associate the structural with the dynamic functional data obtained with electrophysiology. Although voltage-clamp fluorometry fills this gap, it is limited to sites extracellularly accessible, when the key region for gating is located at the cytosolic side of the channels. Here, we solved this problem by performing voltage-clamp fluorometry with a fluorescent unnatural amino acid. By using an orthogonal tRNA-synthetase pair, the fluorescent unnatural amino acid was incorporated in the Shaker voltage-gated potassium channel at key regions that were previously inaccessible. Thus, we defined which parts act independently and which parts act cooperatively and found pore opening to occur in two sequential transitions. PMID:23630265

Isolated pores dissected from human two-pore channel 2 are functional

PubMed Central

Penny, Christopher J.; Rahman, Taufiq; Sula, Altin; Miles, Andrew J.; Wallace, B. A.; Patel, Sandip

2016-01-01

Multi-domain voltage-gated ion channels appear to have evolved through sequential rounds of intragenic duplication from a primordial one-domain precursor. Whereas modularity within one-domain symmetrical channels is established, little is known about the roles of individual regions within more complex asymmetrical channels where the domains have undergone substantial divergence. Here we isolated and characterised both of the divergent pore regions from human TPC2, a two-domain channel that holds a key intermediate position in the evolution of voltage-gated ion channels. In HeLa cells, each pore localised to the ER and caused Ca2+ depletion, whereas an ER-targeted pore mutated at a residue that inactivates full-length TPC2 did not. Additionally, one of the pores expressed at high levels in E. coli. When purified, it formed a stable, folded tetramer. Liposomes reconstituted with the pore supported Ca2+ and Na+ uptake that was inhibited by known blockers of full-length channels. Computational modelling of the pore corroborated cationic permeability and drug interaction. Therefore, despite divergence, both pores are constitutively active in the absence of their partners and retain several properties of the wild-type pore. Such symmetrical ‘pore-only’ proteins derived from divergent channel domains may therefore provide tractable tools for probing the functional architecture of complex ion channels. PMID:27941820

Isolated pores dissected from human two-pore channel 2 are functional.

PubMed

Penny, Christopher J; Rahman, Taufiq; Sula, Altin; Miles, Andrew J; Wallace, B A; Patel, Sandip

2016-12-12

Multi-domain voltage-gated ion channels appear to have evolved through sequential rounds of intragenic duplication from a primordial one-domain precursor. Whereas modularity within one-domain symmetrical channels is established, little is known about the roles of individual regions within more complex asymmetrical channels where the domains have undergone substantial divergence. Here we isolated and characterised both of the divergent pore regions from human TPC2, a two-domain channel that holds a key intermediate position in the evolution of voltage-gated ion channels. In HeLa cells, each pore localised to the ER and caused Ca 2+ depletion, whereas an ER-targeted pore mutated at a residue that inactivates full-length TPC2 did not. Additionally, one of the pores expressed at high levels in E. coli. When purified, it formed a stable, folded tetramer. Liposomes reconstituted with the pore supported Ca 2+ and Na + uptake that was inhibited by known blockers of full-length channels. Computational modelling of the pore corroborated cationic permeability and drug interaction. Therefore, despite divergence, both pores are constitutively active in the absence of their partners and retain several properties of the wild-type pore. Such symmetrical 'pore-only' proteins derived from divergent channel domains may therefore provide tractable tools for probing the functional architecture of complex ion channels.

Comparative Efficacy of Potassium Levulinate with/without Potassium Diacetate and Potassium Propionate vs Potassium Lactate and Sodium Diacetate for Control of Listeria monocytogenes on commercially prepared uncured t.breast

USDA-ARS?s Scientific Manuscript database

We evaluated the efficacy of potassium levulinate, potassium diacetate, and potassium propionate to inhibit Listeria monocytogenes on commercially-prepared, uncured turkey breast during refrigerated storage. Whole muscle, uncured turkey breast chubs (ca. 5 kg each) were formulated with or without po...

The inhibitory effects of potassium chloride versus potassium silicate application on (137)Cs uptake by rice.

PubMed

Fujimura, Shigeto; Yoshioka, Kunio; Ota, Takeshi; Ishikawa, Tetsuya; Sato, Makoto; Satou, Mutsuto

2016-03-01

After the accident at the Fukushima Dai-ichi Nuclear Power Plant owned by the Tokyo Electric Power Company on 11 March 2011, potassium fertilizer was applied to agricultural fields in the southern Tohoku and northern Kanto regions of Japan to reduce the uptake of radiocesium by crops. In this study, we examined the effects of two types of potassium fertilizers, potassium chloride (a readily available potassium fertilizer) and potassium silicate (a slow-release potassium fertilizer), as well as a split application of potassium, on the accumulation of (137)Cs by rice plants in two pot experiments. The (137)Cs concentrations in the brown rice and in the above-ground plants were significantly lower after potassium chloride application than after potassium silicate application. The potassium ion (K(+)) concentrations in soil solutions sampled 9 and 21 d after transplanting were significantly higher for the potassium chloride application than for the potassium silicate application. The K(+) concentrations in soil solutions observed in the application of potassium silicate were similar to those in the treatment when no potassium was applied. This finding indicates that the application of potassium silicate did not sufficiently increase the available K(+) for rice plants in the soil, which led to a greater uptake of (137)Cs after the potassium silicate application than after the application of potassium chloride. The (137)Cs concentration in brown rice was higher in the split application of potassium fertilizer with the second application at the full heading stage than that without split application and the split application with the second application before heading. Copyright © 2016 Elsevier Ltd. All rights reserved.

Potassium and Health123

PubMed Central

Weaver, Connie M.

2013-01-01

Potassium was identified as a shortfall nutrient by the Dietary Guidelines for Americans 2010 Advisory Committee. The committee concluded that there was a moderate body of evidence of the association between potassium intake and blood pressure reduction in adults, which in turn influences the risk of stroke and coronary heart disease. Evidence is also accumulating of the protective effect of adequate dietary potassium on age-related bone loss and reduction of kidney stones. These benefits depend on organic anions associated with potassium as occurs in foods such as fruits and vegetables, in contrast to similar blood pressure-lowering benefits of potassium chloride. Benefits to blood pressure and bone health may occur at levels below current recommendations for potassium intake, especially from diet, but dose-response trials are needed to confirm this. Nevertheless, intakes considerably above current levels are needed for optimal health, and studies evaluating small increases in fruit and vegetable intake on bone and heart outcomes for short periods have had disappointing results. In modern societies, Western diets have led to a decrease in potassium intake with reduced consumption of fruits and vegetables with a concomitant increase in sodium consumption through increased consumption of processed foods. Consumption of white vegetables is associated with decreased risk of stroke, possibly related to their high potassium content. Potatoes are the highest source of dietary potassium, but the addition of salt should be limited. Low potassium-to-sodium intake ratios are more strongly related to cardiovascular disease risk than either nutrient alone. This relationship deserves further attention for multiple target tissue endpoints. PMID:23674806

Pore size distribution and accessible pore size distribution in bituminous coals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sakurovs, Richard; He, Lilin; Melnichenko, Yuri B

2012-01-01

The porosity and pore size distribution of coals determine many of their properties, from gas release to their behavior on carbonization, and yet most methods of determining pore size distribution can only examine a restricted size range. Even then, only accessible pores can be investigated with these methods. Small-angle neutron scattering (SANS) and ultra small-angle neutron scattering (USANS) are increasingly used to characterize the size distribution of all of the pores non-destructively. Here we have used USANS/SANS to examine 24 well-characterized bituminous and subbituminous coals: three from the eastern US, two from Poland, one from New Zealand and the restmore » from the Sydney and Bowen Basins in Eastern Australia, and determined the relationships of the scattering intensity corresponding to different pore sizes with other coal properties. The range of pore radii examinable with these techniques is 2.5 nm to 7 {micro}m. We confirm that there is a wide range of pore sizes in coal. The pore size distribution was found to be strongly affected by both rank and type (expressed as either hydrogen or vitrinite content) in the size range 250 nm to 7 {micro}m and 5 to 10 nm, but weakly in intermediate regions. The results suggest that different mechanisms control coal porosity on different scales. Contrast-matching USANS and SANS were also used to determine the size distribution of the fraction of the pores in these coals that are inaccessible to deuterated methane, CD{sub 4}, at ambient temperature. In some coals most of the small ({approx} 10 nm) pores were found to be inaccessible to CD{sub 4} on the time scale of the measurement ({approx} 30 min - 16 h). This inaccessibility suggests that in these coals a considerable fraction of inherent methane may be trapped for extended periods of time, thus reducing the effectiveness of methane release from (or sorption by) these coals. Although the number of small pores was less in higher rank coals, the fraction of

Effective pore size and radius of capture for K+ ions in K-channels

PubMed Central

Moldenhauer, Hans; Díaz-Franulic, Ignacio; González-Nilo, Fernando; Naranjo, David

2016-01-01

Reconciling protein functional data with crystal structure is arduous because rare conformations or crystallization artifacts occur. Here we present a tool to validate the dimensions of open pore structures of potassium-selective ion channels. We used freely available algorithms to calculate the molecular contour of the pore to determine the effective internal pore radius (rE) in several K-channel crystal structures. rE was operationally defined as the radius of the biggest sphere able to enter the pore from the cytosolic side. We obtained consistent rE estimates for MthK and Kv1.2/2.1 structures, with rE = 5.3–5.9 Å and rE = 4.5–5.2 Å, respectively. We compared these structural estimates with functional assessments of the internal mouth radii of capture (rC) for two electrophysiological counterparts, the large conductance calcium activated K-channel (rC = 2.2 Å) and the Shaker Kv-channel (rC = 0.8 Å), for MthK and Kv1.2/2.1 structures, respectively. Calculating the difference between rE and rC, produced consistent size radii of 3.1–3.7 Å and 3.6–4.4 Å for hydrated K+ ions. These hydrated K+ estimates harmonize with others obtained with diverse experimental and theoretical methods. Thus, these findings validate MthK and the Kv1.2/2.1 structures as templates for open BK and Kv-channels, respectively. PMID:26831782

Effective pore size and radius of capture for K(+) ions in K-channels.

PubMed

Moldenhauer, Hans; Díaz-Franulic, Ignacio; González-Nilo, Fernando; Naranjo, David

2016-02-02

Reconciling protein functional data with crystal structure is arduous because rare conformations or crystallization artifacts occur. Here we present a tool to validate the dimensions of open pore structures of potassium-selective ion channels. We used freely available algorithms to calculate the molecular contour of the pore to determine the effective internal pore radius (r(E)) in several K-channel crystal structures. r(E) was operationally defined as the radius of the biggest sphere able to enter the pore from the cytosolic side. We obtained consistent r(E) estimates for MthK and Kv1.2/2.1 structures, with r(E) = 5.3-5.9 Å and r(E) = 4.5-5.2 Å, respectively. We compared these structural estimates with functional assessments of the internal mouth radii of capture (r(C)) for two electrophysiological counterparts, the large conductance calcium activated K-channel (r(C) = 2.2 Å) and the Shaker Kv-channel (r(C) = 0.8 Å), for MthK and Kv1.2/2.1 structures, respectively. Calculating the difference between r(E) and r(C), produced consistent size radii of 3.1-3.7 Å and 3.6-4.4 Å for hydrated K(+) ions. These hydrated K(+) estimates harmonize with others obtained with diverse experimental and theoretical methods. Thus, these findings validate MthK and the Kv1.2/2.1 structures as templates for open BK and Kv-channels, respectively.

Amino acid residues involved in membrane insertion and pore formation of Clostridium botulinum C2 toxin.

PubMed

Lang, Alexander E; Neumeyer, Tobias; Sun, Jianjun; Collier, R John; Benz, Roland; Aktories, Klaus

2008-08-12

The actin-ADP-ribosylating Clostridium botulinum C2 toxin consists of the enzymatic component C2I and the binding component C2II. C2II forms heptameric channels involved in translocation of the enzymatic component into the target cell. On the basis of the heptameric toxin channel, we studied functional consequences of mutagenesis of amino acid residues probably lining the lumen of the toxin channel. Substitution of glutamate-399 of C2II with alanine blocked channel formation and cytotoxicity of the holotoxin. Although cytotoxicity and rounding up of cells by C2I were completely blocked by exchange of phenylalanine-428 with alanine, the mutation increased potassium conductance caused by C2II in artificial membranes by about 2-3-fold over that of wild-type toxin. In contrast to its effects on single-channel potassium conductance in artificial membranes, the F428A mutation delayed the kinetics of pore formation in lipid vesicles and inhibited the activity of C2II in promoting (86)Rb (+) release from preloaded intact cells after pH shift of the medium. Moreover, F428A C2II exhibited delayed and diminished formation of C2II aggregates at low pH, indicating major changes of the biophysical properties of the toxin. The data indicate that phenylalanine-428 of C2II plays a major role in conformational changes occurring during pore formation of the binding component of C2II.

Pore network extraction from pore space images of various porous media systems

NASA Astrophysics Data System (ADS)

Yi, Zhixing; Lin, Mian; Jiang, Wenbin; Zhang, Zhaobin; Li, Haishan; Gao, Jian

2017-04-01

Pore network extraction, which is defined as the transformation from irregular pore space to a simplified network in the form of pores connected by throats, is significant to microstructure analysis and network modeling. A physically realistic pore network is not only a representation of the pore space in the sense of topology and morphology, but also a good tool for predicting transport properties accurately. We present a method to extract pore network by employing the centrally located medial axis to guide the construction of maximal-balls-like skeleton where the pores and throats are defined and parameterized. To validate our method, various rock samples including sand pack, sandstones, and carbonates were used to extract pore networks. The pore structures were compared quantitatively with the structures extracted by medial axis method or maximal ball method. The predicted absolute permeability and formation factor were verified against the theoretical solutions obtained by lattice Boltzmann method and finite volume method, respectively. The two-phase flow was simulated through the networks extracted from homogeneous sandstones, and the generated relative permeability curves were compared with the data obtained from experimental method and other numerical models. The results show that the accuracy of our network is higher than that of other networks for predicting transport properties, so the presented method is more reliable for extracting physically realistic pore network.

Bioavailability of potassium from potatoes and potassium gluconate: a randomized dose response trial.

PubMed

Macdonald-Clarke, Claire J; Martin, Berdine R; McCabe, Linda D; McCabe, George P; Lachcik, Pamela J; Wastney, Meryl; Weaver, Connie M

2016-08-01

The bioavailability of potassium should be considered in setting requirements, but to our knowledge, the bioavailability from individual foods has not been determined. Potatoes provide 19-20% of potassium in the American diet. We compared the bioavailability and dose response of potassium from nonfried white potatoes with skin [targeted at 20, 40, and 60 milliequivalents (mEq) K] and French fries (40 mEq K) with potassium gluconate at the same doses when added to a basal diet that contained ∼60 mEq K. Thirty-five healthy, normotensive men and women with a mean ± SD age of 29.7 ± 11.2 y and body mass index (in kg/m(2)) of 24.3 ± 4.4 were enrolled in a single-blind, crossover, randomized controlled trial. Participants were partially randomly assigned to the order of testing for nine 5-d interventions of additional potassium as follows: 0 (control; repeated at phases 1 and 5), 20, 40, and 60 mEq K/d consumed as a potassium gluconate supplement or as unfried potato or 40 mEq K from French fries completed at phase 9. The bioavailability of potassium was determined from the area under the curve (AUC) of serial blood draws and cumulative urinary excretion during a 24-h period and from a kinetic analysis. The effects of the potassium source and dose on the change in blood pressure and augmentation index (AIx) were determined. The serum potassium AUC increased with the dose (P < 0.0001) and did not differ because of the source (P = 0.53). Cumulative 24-h urinary potassium also increased with the dose (P < 0.0001) and was greater with the potato than with the supplement (P < 0.0001). The kinetic analysis showed the absorption efficiency was high across all interventions (>94% ± 12%). There were no significant differences in the change in blood pressure or AIx with the treatment source or dose. The bioavailability of potassium is as high from potatoes as from potassium gluconate supplements. Future studies that measure the effect of dietary potassium on blood pressure

Oral potassium supplementation in surgical patients.

PubMed

Hainsworth, Alison J; Gatenby, Piers A

2008-08-01

Hospital inpatients are frequently hypokalaemic. Low plasma potassium levels may cause life threatening complications, such as cardiac arrhythmias. Potassium supplementation may be administered parenterally or enterally. Oral potassium supplements have been associated with oesophageal ulceration, strictures and gastritis. An alternative to potassium salt tablets or solution is dietary modification with potassium rich food stuffs, which has been proven to be a safe and effective method for potassium supplementation. The potassium content of one medium banana is equivalent to a 12 mmol potassium salt tablet. Potassium supplementation by dietary modification has been shown to be equally efficacious to oral potassium salt supplementation and is preferred by the majority of patients. Subsequently, it is our practice to replace potassium using dietary modification, particularly in surgical patients having undergone oesophagogastrectomy or in those with peptic ulcer disease.

The Role of the Two-Pore Domain Potassium Channel TREK-1 in the Therapeutic Effects of Escitalopram in a Rat Model of Poststroke Depression.

PubMed

Lin, Dai-Hua; Zhang, Xiang-Rong; Ye, Dong-Qing; Xi, Guang-Jun; Hui, Jiao-Jie; Liu, Shan-Shan; Li, Lin-Jiang; Zhang, Zhi-Jun

2015-06-01

Poststroke depression (PSD) is one of the most common neuropsychiatric complications after stroke. TREK-1, a two-pore-domain potassium channel, has been implicated in the pathogenesis of stroke and depression. The aim of this study was to investigate whether TREK-1 plays a role in the therapeutic effects of the selective serotonin reuptake inhibitor (SSRI) escitalopram in a rat PSD model. The whole-cell patch-clamp technique was performed to assess the effect of escitalopram on recombinant TREK-1 currents in HEK293 cells. The expression of TREK-1 mRNA and protein was measured in the hippocampus and prefrontal cortex (PFC), and neural stem cell (NSC) proliferation was detected in the hippocampal dentate gyrus (DG) in PSD rats after 3 weeks of escitalopram administration. Escitalopram reversibly inhibited TREK-1 currents in a concentration-dependent manner. Chronic treatment with escitalopram significantly reversed the reductions in weight gain, locomotor activity, and sucrose preference in PSD rats. The expressions of TREK-1 mRNA and protein were significantly increased in hippocampal CA1, CA3, DG, and PFC in PSD rats, with the exception of TREK-1 mRNA in hippocampal CA1. NSC proliferation was significantly decreased in hippocampal DG of PSD rats. Escitalopram significantly reversed the regional increases of TREK-1 expression and the reduction of hippocampal NSC proliferation in PSD rats. TREK-1 plays an important role in the therapeutic effects of the SSRI escitalopram in PSD model, making TREK-1 an attractive candidate molecule for further understanding the pathophysiology and treatment of PSD. © 2015 John Wiley & Sons Ltd.

Adsorption of pharmaceuticals to microporous activated carbon treated with potassium hydroxide, carbon dioxide, and steam.

PubMed

Fu, Heyun; Yang, Liuyan; Wan, Yuqiu; Xu, Zhaoyi; Zhu, Dongqiang

2011-01-01

Adsorption of sulfapyridine, tetracycline, and tylosin to a commercial microporous activated carbon (AC) and its potassium hydroxide (KOH)-, CO-, and steam-treated counterparts (prepared by heating at 850°C) was studied to explore efficient adsorbents for the removal of selected pharmaceuticals from water. Phenol and nitrobenzene were included as additional adsorbates, and nonporous graphite was included as a model adsorbent. The activation treatments markedly increased the specific surface area and enlarged the pore sizes of the mesopores of AC (with the strongest effects shown on the KOH-treated AC). Adsorption of large-size tetracycline and tylosin was greatly enhanced, especially for the KOH-treated AC (more than one order of magnitude), probably due to the alleviated size-exclusion effect. However, the treatments had little effect on adsorption of low-size phenol and nitrobenzene due to the predominance of micropore-filling effect in adsorption and the nearly unaffected content of small micropores causative to such effect. These hypothesized mechanisms on pore-size dependent adsorption were further tested by comparing surface area-normalized adsorption data and adsorbent pore size distributions with and without the presence of adsorbed antibiotics. The findings indicate that efficient adsorption of bulky pharmaceuticals to AC can be achieved by enlarging the adsorbent pore size through suitable activation treatments. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Physiology and pathophysiology of potassium homeostasis.

PubMed

Palmer, Biff F; Clegg, Deborah J

2016-12-01

Total body potassium content and proper distribution of potassium across the cell membrane is of critical importance for normal cellular function. Potassium homeostasis is maintained by several different methods. In the kidney, total body potassium content is achieved by alterations in renal excretion of potassium in response to variations in intake. Insulin and beta-adrenergic tone play critical roles in maintaining the internal distribution of potassium under normal conditions. Despite homeostatic pathways designed to maintain potassium levels within the normal range, disorders of altered potassium homeostasis are common. The clinical approach to designing effective treatments relies on understanding the pathophysiology and regulatory influences which govern the internal distribution and external balance of potassium. Here we provide an overview of the key regulatory aspects of normal potassium physiology. This review is designed to provide an overview of potassium homeostasis as well as provide references of seminal papers to guide the reader into a more in depth discussion of the importance of potassium balance. This review is designed to be a resource for educators and well-informed clinicians who are teaching trainees about the importance of potassium balance. Copyright © 2016 the American Physiological Society.

Pore-Scale Modeling of Pore Structure Effects on P-Wave Scattering Attenuation in Dry Rocks

PubMed Central

Li, Tianyang; Qiu, Hao; Wang, Feifei

2015-01-01

Underground rocks usually have complex pore system with a variety of pore types and a wide range of pore size. The effects of pore structure on elastic wave attenuation cannot be neglected. We investigated the pore structure effects on P-wave scattering attenuation in dry rocks by pore-scale modeling based on the wave theory and the similarity principle. Our modeling results indicate that pore size, pore shape (such as aspect ratio), and pore density are important factors influencing P-wave scattering attenuation in porous rocks, and can explain the variation of scattering attenuation at the same porosity. From the perspective of scattering attenuation, porous rocks can safely suit to the long wavelength assumption when the ratio of wavelength to pore size is larger than 15. Under the long wavelength condition, the scattering attenuation coefficient increases as a power function as the pore density increases, and it increases exponentially with the increase in aspect ratio. For a certain porosity, rocks with smaller aspect ratio and/or larger pore size have stronger scattering attenuation. When the pore aspect ratio is larger than 0.5, the variation of scattering attenuation at the same porosity is dominantly caused by pore size and almost independent of the pore aspect ratio. These results lay a foundation for pore structure inversion from elastic wave responses in porous rocks. PMID:25961729

Potassium: friend or foe?

PubMed

Rodan, Aylin R

2017-07-01

The kidney plays an essential role in maintaining homeostasis of ion concentrations in the blood. Because the concentration gradient of potassium across the cell membrane is a key determinant of the membrane potential of cells, even small deviations in serum potassium level from the normal setpoint can lead to severe muscle dysfunction, resulting in respiratory failure and cardiac arrest. Less severe hypo- and hyperkalemia are also associated with morbidity and mortality across various patient populations. In addition, deficiencies in potassium intake have been associated with hypertension and adverse cardiovascular and renal outcomes, likely due in part to the interrelated handling of sodium and potassium by the kidney. Here, data on the beneficial effects of potassium on blood pressure and cardiovascular and renal outcomes will be reviewed, along with the physiological basis for these effects. In some patient populations, however, potassium excess is deleterious. Risk factors for the development of hyperkalemia will be reviewed, as well as the risks and benefits of existing and emerging therapies for hyperkalemia.

Drug release through liposome pores.

PubMed

Dan, Nily

2015-02-01

Electrical, ultrasound and other types of external fields are known to induce the formation of pores in cellular and model membranes. This paper examines drug release through field induced liposome pores using Monte Carlo simulations. We find that drug release rates vary as a function of pore size and spacing, as well as the overall fraction of surface area covered by pores: The rate of release from liposomes is found to increase rapidly with pore surface coverage, approaching that of the fully ruptured liposome at fractional pore areas. For a given pore surface coverage, the pore size affects the release rate in the limit of low coverage, but not when the pores cover a relatively high fraction of the liposome surface area. On the other hand, for a given pore size and surface coverage, the distribution of pores significantly affects the release in the limit of high surface coverage: The rate of release from a liposome covered with a regularly spaced array of pores is, in this limit, higher than the release rate from (most) systems where the pores are distributed randomly on the liposome surface. In contrast, there is little effect of the pore distribution on release when the pore surface coverage is low. The simulation results are in good agreement with the predictions of detailed diffusion models. Copyright © 2014 Elsevier B.V. All rights reserved.

Chronic potassium depletion increases adrenal progesterone production that is necessary for efficient renal retention of potassium.

PubMed

Elabida, Boutaïna; Edwards, Aurélie; Salhi, Amel; Azroyan, Anie; Fodstad, Heidi; Meneton, Pierre; Doucet, Alain; Bloch-Faure, May; Crambert, Gilles

2011-08-01

Modern dietary habits are characterized by high-sodium and low-potassium intakes, each of which was correlated with a higher risk for hypertension. In this study, we examined whether long-term variations in the intake of sodium and potassium induce lasting changes in the plasma concentration of circulating steroids by developing a mathematical model of steroidogenesis in mice. One finding of this model was that mice increase their plasma progesterone levels specifically in response to potassium depletion. This prediction was confirmed by measurements in both male mice and men. Further investigation showed that progesterone regulates renal potassium handling both in males and females under potassium restriction, independent of its role in reproduction. The increase in progesterone production by male mice was time dependent and correlated with decreased urinary potassium content. The progesterone-dependent ability to efficiently retain potassium was because of an RU486 (a progesterone receptor antagonist)-sensitive stimulation of the colonic hydrogen, potassium-ATPase (known as the non-gastric or hydrogen, potassium-ATPase type 2) in the kidney. Thus, in males, a specific progesterone concentration profile induced by chronic potassium restriction regulates potassium balance.

Covalently Linked Tandem Lesions in DNA

PubMed Central

Patrzyc, Helen B.; Dawidzik, Jean B.; Budzinski, Edwin E.; Freund, Harold G.; Wilton, John H.; Box, Harold C.

2013-01-01

Reactive oxygen species (ROS) generate a type of DNA damage called tandem lesions, two adjacent nucleotides both modified. A subcategory of tandem lesions consists of adjacent nucleotides linked by a covalent bond. Covalently linked tandem lesions generate highly characteristic liquid chromotography-tandem mass spectrometry (LC-MS/MS) elution profiles. We have used this property to comprehensively survey X-irradiated DNA for covalently linked tandem lesions. A total of 15 tandem lesions were detected in DNA irradiated in deoxygenated aqueous solution, five tandem lesions were detected in DNA that was irradiated in oxygenated solution. PMID:23106212

Time to Consider Use of the Sodium-to-Potassium Ratio for Practical Sodium Reduction and Potassium Increase

PubMed Central

Miura, Katsuyuki; Ueshima, Hirotsugu

2017-01-01

Pathogenetic studies have demonstrated that the interdependency of sodium and potassium affects blood pressure. Emerging evidences on the sodium-to-potassium ratio show benefits for a reduction in sodium and an increase in potassium compared to sodium and potassium separately. As presently there is no known review, this article examined the practical use of the sodium-to-potassium ratio in daily practice. Epidemiological studies suggest that the urinary sodium-to-potassium ratio may be a superior metric as compared to separate sodium and potassium values for determining the relation to blood pressure and cardiovascular disease risks. Higher correlations and better agreements are seen for the casual urine sodium-to-potassium ratio than for casual urine sodium or potassium alone when compared with the 24-h urine values. Repeated measurements of the casual urine provide reliable estimates of the 7-day 24-h urine value with less bias for the sodium-to-potassium ratio as compared to the common formulas used for estimating the single 24-h urine from the casual urine for sodium and potassium separately. Self-monitoring devices for the urinary sodium-to-potassium ratio measurement makes it possible to provide prompt onsite feedback. Although these devices have been evaluated with a view to support an individual approach for sodium reduction and potassium increase, there has yet to be an accepted recommended guideline for the sodium-to-potassium ratio. This review concludes with a look at the practical use of the sodium-to-potassium ratio for assistance in practical sodium reduction and potassium increase. PMID:28678188

Voltage-Dependent Gating of hERG Potassium Channels

PubMed Central

Cheng, Yen May; Claydon, Tom W.

2012-01-01

The mechanisms by which voltage-gated channels sense changes in membrane voltage and energetically couple this with opening of the ion conducting pore has been the source of significant interest. In voltage-gated potassium (Kv) channels, much of our knowledge in this area comes from Shaker-type channels, for which voltage-dependent gating is quite rapid. In these channels, activation and deactivation are associated with rapid reconfiguration of the voltage-sensing domain unit that is electromechanically coupled, via the S4–S5 linker helix, to the rate-limiting opening of an intracellular pore gate. However, fast voltage-dependent gating kinetics are not typical of all Kv channels, such as Kv11.1 (human ether-à-go-go related gene, hERG), which activates and deactivates very slowly. Compared to Shaker channels, our understanding of the mechanisms underlying slow hERG gating is much poorer. Here, we present a comparative review of the structure–function relationships underlying activation and deactivation gating in Shaker and hERG channels, with a focus on the roles of the voltage-sensing domain and the S4–S5 linker that couples voltage sensor movements to the pore. Measurements of gating current kinetics and fluorimetric analysis of voltage sensor movement are consistent with models suggesting that the hERG activation pathway contains a voltage independent step, which limits voltage sensor transitions. Constraints upon hERG voltage sensor movement may result from loose packing of the S4 helices and additional intra-voltage sensor counter-charge interactions. More recent data suggest that key amino acid differences in the hERG voltage-sensing unit and S4–S5 linker, relative to fast activating Shaker-type Kv channels, may also contribute to the increased stability of the resting state of the voltage sensor. PMID:22586397

Lattice density functional theory investigation of pore shape effects. I. Adsorption in single nonperiodic pores.

PubMed

Malanoski, A P; van Swol, Frank

2002-10-01

A fully explicit in three dimensions lattice density functional theory is used to investigate adsorption in single nonperiodic pores. The effect of varying pore shape from the slits and cylinders that are normally simulated was our primary interest. A secondary concern was the results for pores with very large diameters. The shapes investigated were square pores with or without surface roughness, cylinders, right triangle pores, and trapezoidal pores. It was found that pores with very similar shape factors gave similar results but that the introduction of acute angled corners or very large side ratio lengths in rectangular pores gave results that were significantly different. Further, a rectangular pore going towards the limit of infinite side ratio does not approach the results of a slit pore. In all of these cases, the importance of features that are present for only a small portion of the pore is demonstrated.

Low potassium level

MedlinePlus

... of low potassium level include: Medicines, such as diuretics (water pills), certain antibiotics Diarrhea or vomiting Using ... potassium through a vein (IV). If you need diuretics, your provider may: Switch you to a form ...

Penicillin V Potassium

MedlinePlus

Penicillin V potassium is used to treat certain infections caused by bacteria such as pneumonia and other ... heart valves and other symptoms) from coming back. Penicillin V potassium is in a class of medications ...

21 CFR 184.1613 - Potassium bicarbonate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Potassium bicarbonate. 184.1613 Section 184.1613... Listing of Specific Substances Affirmed as GRAS § 184.1613 Potassium bicarbonate. (a) Potassium... potassium hydroxide with carbon dioxide; (2) By treating a solution of potassium carbonate with carbon...

21 CFR 184.1619 - Potassium carbonate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Potassium carbonate. 184.1619 Section 184.1619... Listing of Specific Substances Affirmed as GRAS § 184.1619 Potassium carbonate. (a) Potassium carbonate... of potassium chloride followed by exposing the resultant potassium to carbon dioxide; (2) By treating...

21 CFR 184.1619 - Potassium carbonate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Potassium carbonate. 184.1619 Section 184.1619... Listing of Specific Substances Affirmed as GRAS § 184.1619 Potassium carbonate. (a) Potassium carbonate... of potassium chloride followed by exposing the resultant potassium to carbon dioxide; (2) By treating...

21 CFR 184.1613 - Potassium bicarbonate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Potassium bicarbonate. 184.1613 Section 184.1613... Listing of Specific Substances Affirmed as GRAS § 184.1613 Potassium bicarbonate. (a) Potassium... potassium hydroxide with carbon dioxide; (2) By treating a solution of potassium carbonate with carbon...

21 CFR 184.1619 - Potassium carbonate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Potassium carbonate. 184.1619 Section 184.1619... Listing of Specific Substances Affirmed as GRAS § 184.1619 Potassium carbonate. (a) Potassium carbonate... of potassium chloride followed by exposing the resultant potassium to carbon dioxide; (2) By treating...

21 CFR 184.1613 - Potassium bicarbonate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Potassium bicarbonate. 184.1613 Section 184.1613... Listing of Specific Substances Affirmed as GRAS § 184.1613 Potassium bicarbonate. (a) Potassium... potassium hydroxide with carbon dioxide; (2) By treating a solution of potassium carbonate with carbon...

21 CFR 184.1613 - Potassium bicarbonate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Potassium bicarbonate. 184.1613 Section 184.1613... Listing of Specific Substances Affirmed as GRAS § 184.1613 Potassium bicarbonate. (a) Potassium... potassium hydroxide with carbon dioxide; (2) By treating a solution of potassium carbonate with carbon...

21 CFR 184.1631 - Potassium hydroxide.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Potassium hydroxide. 184.1631 Section 184.1631... GRAS § 184.1631 Potassium hydroxide. (a) Potassium hydroxide (KOH, CAS Reg. No. 1310-58-3) is also... powders. Potassium hydroxide is obtained commercially from the electrolysis of potassium chloride solution...

21 CFR 172.800 - Acesulfame potassium.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Acesulfame potassium. 172.800 Section 172.800 Food... Multipurpose Additives § 172.800 Acesulfame potassium. Acesulfame potassium (CAS Reg. No. 55589-62-3), also... not preclude such use, under the following conditions: (a) Acesulfame potassium is the potassium salt...

21 CFR 172.800 - Acesulfame potassium.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Acesulfame potassium. 172.800 Section 172.800 Food... Multipurpose Additives § 172.800 Acesulfame potassium. Acesulfame potassium (CAS Reg. No. 55589-62-3), also... not preclude such use, under the following conditions: (a) Acesulfame potassium is the potassium salt...

21 CFR 172.800 - Acesulfame potassium.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Acesulfame potassium. 172.800 Section 172.800 Food... Multipurpose Additives § 172.800 Acesulfame potassium. Acesulfame potassium (CAS Reg. No. 55589-62-3), also... not preclude such use, under the following conditions: (a) Acesulfame potassium is the potassium salt...

21 CFR 172.800 - Acesulfame potassium.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Acesulfame potassium. 172.800 Section 172.800 Food... Multipurpose Additives § 172.800 Acesulfame potassium. Acesulfame potassium (CAS Reg. No. 55589-62-3), also... not preclude such use, under the following conditions: (a) Acesulfame potassium is the potassium salt...

Potassium intake modulates the thiazide-sensitive sodium-chloride cotransporter (NCC) activity via the Kir4.1 potassium channel.

PubMed

Wang, Ming-Xiao; Cuevas, Catherina A; Su, Xiao-Tong; Wu, Peng; Gao, Zhong-Xiuzi; Lin, Dao-Hong; McCormick, James A; Yang, Chao-Ling; Wang, Wen-Hui; Ellison, David H

2018-04-01

Kir4.1 in the distal convoluted tubule plays a key role in sensing plasma potassium and in modulating the thiazide-sensitive sodium-chloride cotransporter (NCC). Here we tested whether dietary potassium intake modulates Kir4.1 and whether this is essential for mediating the effect of potassium diet on NCC. High potassium intake inhibited the basolateral 40 pS potassium channel (a Kir4.1/5.1 heterotetramer) in the distal convoluted tubule, decreased basolateral potassium conductance, and depolarized the distal convoluted tubule membrane in Kcnj10flox/flox mice, herein referred to as control mice. In contrast, low potassium intake activated Kir4.1, increased potassium currents, and hyperpolarized the distal convoluted tubule membrane. These effects of dietary potassium intake on the basolateral potassium conductance and membrane potential in the distal convoluted tubule were completely absent in inducible kidney-specific Kir4.1 knockout mice. Furthermore, high potassium intake decreased, whereas low potassium intake increased the abundance of NCC expression only in the control but not in kidney-specific Kir4.1 knockout mice. Renal clearance studies demonstrated that low potassium augmented, while high potassium diminished, hydrochlorothiazide-induced natriuresis in control mice. Disruption of Kir4.1 significantly increased basal urinary sodium excretion but it abolished the natriuretic effect of hydrochlorothiazide. Finally, hypokalemia and metabolic alkalosis in kidney-specific Kir4.1 knockout mice were exacerbated by potassium restriction and only partially corrected by a high-potassium diet. Thus, Kir4.1 plays an essential role in mediating the effect of dietary potassium intake on NCC activity and potassium homeostasis. Copyright © 2017 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.

Potassium supplements for oral diarrhoea regimens.

PubMed

Clements, M L; Levine, M M; Black, R E; Hughes, T P; Rust, J; Tome, F C

1980-10-18

A study is proposed for supplementing potassium loss from diarrhea in rehydration therapies with fresh fruit and other naturally potassium-rich foods. Bananas contain .1 mol of potassium per gm. Freshly squeezed lemon or orange juices were tested for potassium and sodium content and found to have very low potassium concentration. Therefore, the banana was chosen for an upcoming study that will determine if infants and children suffering from diarrhea can ingest the amounts of the fruit necessary to elevate the potassium level sufficiently. Bananas as the potassium source are thought to be well-accepted in developing areas.

21 CFR 184.1619 - Potassium carbonate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Potassium carbonate. 184.1619 Section 184.1619 Food... Specific Substances Affirmed as GRAS § 184.1619 Potassium carbonate. (a) Potassium carbonate (K2CO3, CAS... potassium chloride followed by exposing the resultant potassium to carbon dioxide; (2) By treating a...

21 CFR 184.1634 - Potassium iodide.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Potassium iodide. 184.1634 Section 184.1634 Food... GRAS § 184.1634 Potassium iodide. (a) Potassium iodide (KI, CAS Reg. No. 7681-11-0) is the potassium... reacting hydriodic acid (HI) with potassium bicarbonate (KHCO3). (b) The ingredient meets the...

21 CFR 184.1610 - Potassium alginate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Potassium alginate. 184.1610 Section 184.1610 Food... GRAS § 184.1610 Potassium alginate. (a) Potassium alginate (CAS Reg. No. 9005-36-1) is the potassium salt of alginic acid, a natural polyuronide constituent of certain brown algae. Potassium alginate is...

Pore formation and pore closure in poly(D,L-lactide-co-glycolide) films.

PubMed

Fredenberg, Susanne; Wahlgren, Marie; Reslow, Mats; Axelsson, Anders

2011-03-10

Pore formation and pore closure in poly(D,L-lactide-co-glycolide)-based drug delivery systems are two important processes as they control the release of the encapsulated drug. The phenomenon pore closure was investigated by studying the effects of the pH and the temperature of the release medium, and the properties of the polymer. Poly(D,L-lactide-co-glycolide) (PLG) films were subjected to a pore forming pre-treatment, and then pore closure was observed simultaneously with changes in glass transition temperature, wettability (contact angle), water absorption and mass remaining. To further understand the effect of pH, combined pore formation and pore closure were studied at different pH values. Pore closure was increased in a release medium with low pH, with a low-molecular-weight PLG of relatively low degree of hydrophobicity, or at high temperature. Pore closure occurred by two different mechanisms, one based on polymer-polymer interactions and one on polymer-water interactions. The mobility of the PLG chains also played an important role. The surface of the PLG films were more porous at pH 5-6 than at lower or higher pH, as pore formation was relatively fast and pore closure were less pronounced in this pH range. The pH had a significant impact on the porous structure, which should be kept in mind when evaluating experimental results, as the pH may be significantly decreased in vitro, in vivo and in situ. The results also show that the initial porosity is very important when using a high-molecular-weight PLG. Copyright © 2010 Elsevier B.V. All rights reserved.

21 CFR 184.1643 - Potassium sulfate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Potassium sulfate. 184.1643 Section 184.1643 Food... GRAS § 184.1643 Potassium sulfate. (a) Potassium sulfate (K2SO4, CAS Reg. No. 7778-80-5) occurs.... It is prepared by the neutralization of sulfuric acid with potassium hydroxide or potassium carbonate...

Hyperkalemia (High Potassium)

MedlinePlus

Symptoms High potassium (hyperkalemia) By Mayo Clinic Staff Hyperkalemia is the medical term that describes a potassium level in your blood that's higher ... medications or dialysis. If you have symptoms of hyperkalemia, particularly if you have kidney disease or are ...

Big Potassium (BK) ion channels in biology, disease and possible targets for cancer immunotherapy

PubMed Central

Ge, Lisheng; Hoa, Neil T.; Wilson, Zechariah; Arismendi-Morillo, Gabriel; Kong, Xia-Tang; Tajhya, Rajeev B.; Beeton, Christine; Jadus, Martin R.

2017-01-01

The Big Potassium (BK) ion channel is commonly known by a variety of names (Maxi-K, KCNMA1, slo, Stretch-activated potassium channels, KCa1.1). Each name reflects a different physical property displayed by this single ion channel. This transmembrane channel is found on nearly every cell type of the body and has its own distinctive roles for that tissue type. The BKα channel contains the pore that releases potassium ions from intracellular stores. This ion channel is found on the cell membrane, endoplasmic reticulum, Golgi and mitochondria. Complex splicing pathways produce different isoforms. The BKα channels can be phosphorylated, palmitoylated and myristylated. BK is composed of a homo-tetramer that interacts with β and γ chains. These accessory proteins provide a further modulating effect on the functions of BKα channels. BK channels play important roles in cell division and migration. In this review, we will focus on the biology of BK channels, especially its role, and that it has in the immune response towards cancer. Recent proteomic studies have linked BK channels with various proteins. Some of these interactions offer further insight into the role that BK channels have with cancers, especially with brain tumors. This review shows that BK channels have a complex interplay with intracellular components of cancer cells and still have plenty of secrets to be discovered. PMID:25027630

21 CFR 172.800 - Acesulfame potassium.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Acesulfame potassium. 172.800 Section 172.800 Food... Acesulfame potassium. Acesulfame potassium (CAS Reg. No. 55589-62-3), also known as acesulfame K, may be... following conditions: (a) Acesulfame potassium is the potassium salt of 6-methyl-1,2,3-oxathiazine-4(3H)-one...

Electrochemically-Driven Insertion of Biological Nanodiscs into Solid State Membrane Pores as a Basis for "Pore-In-Pore" Membranes.

PubMed

Farajollahi, Farid; Seidenstücker, Axel; Altintoprak, Klara; Walther, Paul; Ziemann, Paul; Plettl, Alfred; Marti, Othmar; Wege, Christina; Gliemann, Hartmut

2018-04-13

Nanoporous membranes are of increasing interest for many applications, such as molecular filters, biosensors, nanofluidic logic and energy conversion devices. To meet high-quality standards, e.g., in molecular separation processes, membranes with well-defined pores in terms of pore diameter and chemical properties are required. However, the preparation of membranes with narrow pore diameter distributions is still challenging. In the work presented here, we demonstrate a strategy, a "pore-in-pore" approach, where the conical pores of a solid state membrane produced by a multi-step top-down lithography procedure are used as a template to insert precisely-formed biomolecular nanodiscs with exactly defined inner and outer diameters. These nanodiscs, which are the building blocks of tobacco mosaic virus-deduced particles, consist of coat proteins, which self-assemble under defined experimental conditions with a stabilizing short RNA. We demonstrate that the insertion of the nanodiscs can be driven either by diffusion due to a concentration gradient or by applying an electric field along the cross-section of the solid state membrane. It is found that the electrophoresis-driven insertion is significantly more effective than the insertion via the concentration gradient.

Quasi-specific access of the potassium channel inactivation gate

PubMed Central

Venkataraman, Gaurav; Srikumar, Deepa; Holmgren, Miguel

2014-01-01

Many voltage-gated potassium channels open in response to membrane depolarization and then inactivate within milliseconds. Neurons use these channels to tune their excitability. In Shaker K+ channels, inactivation is caused by the cytoplasmic amino terminus, termed the inactivation gate. Despite having four such gates, inactivation is caused by the movement of a single gate into a position that occludes ion permeation. The pathway that this single inactivation gate takes into its inactivating position remains unknown. Here we show that a single gate threads through the intracellular entryway of its own subunit, but the tip of the gate has sufficient freedom to interact with all four subunits deep in the pore, and does so with equal probability. This pathway demonstrates that flexibility afforded by the inactivation peptide segment at the tip of the N-terminus is used to mediate function. PMID:24909510

Effect of polacrilin potassium as disintegrant on bioavailability of diclofenac potassium in tablets : a technical note.

PubMed

Bele, Mrudula H; Derle, Diliprao V

2012-09-01

Polacrilin potassium is an ion exchange resin used in oral pharmaceutical formulations as a tablet disintegrant. It is a weakly acidic cation exchange resin. Chemically, it is a partial potassium salt of a copolymer of methacrylic acid with divinyl benzene. It ionizes to an anionic polymer chain and potassium cations. It was hypothesized that polacrilin potassium may be able to improve the permeability of anionic drugs according to the Donnan membrane phenomenon. The effect of polacrilin potassium on the permeability of diclofenac potassium, used as a model anionic drug, was tested in vitro using diffusion cells and in vivo by monitoring serum levels in rats. The amount of drug permeated across a dialysis membrane in vitro was significantly more in the presence of polacrilin potassium. Significant improvement was found in the extent of drug absorption in vivo. It could be concluded that polacrilin potassium may be used as a high-functionality excipient for improving the bioavailability of anionic drugs having poor gastrointestinal permeability.

21 CFR 184.1625 - Potassium citrate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Potassium citrate. 184.1625 Section 184.1625 Food... GRAS § 184.1625 Potassium citrate. (a) Potassium citrate (C6H5K3O7·H2O, CAS Reg. No. 006100-0905-096) is the potassium salt of citric acid. It is prepared by neutralizing citric acid with potassium...

Orthogonal tandem catalysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lohr, Tracy L.; Marks, Tobin J.

2015-05-20

Tandem catalysis is a growing field that is beginning to yield important scientific and technological advances toward new and more efficient catalytic processes. 'One-pot' tandem reactions, where multiple catalysts and reagents, combined in a single reaction vessel undergo a sequence of precisely staged catalytic steps, are highly attractive from the standpoint of reducing both waste and time. Orthogonal tandem catalysis is a subset of one-pot reactions in which more than one catalyst is used to promote two or more mechanistically distinct reaction steps. This Perspective summarizes and analyses some of the recent developments and successes in orthogonal tandem catalysis, withmore » particular focus on recent strategies to address catalyst incompatibility. We also highlight the concept of thermodynamic leveraging by coupling multiple catalyst cycles to effect challenging transformations not observed in single-step processes, and to encourage application of this technique to energetically unfavourable or demanding reactions.« less

The two-pore domain potassium channel, TWIK-1, has a role in the regulation of heart rate and atrial size.

PubMed

Christensen, Alex Hørby; Chatelain, Franck C; Huttner, Inken G; Olesen, Morten Salling; Soka, Magdalena; Feliciangeli, Sylvain; Horvat, Claire; Santiago, Celine F; Vandenberg, Jamie I; Schmitt, Nicole; Olesen, Søren-Peter; Lesage, Florian; Fatkin, Diane

2016-08-01

The two-pore domain potassium (K(+)) channel TWIK-1 (or K2P1.1) contributes to background K(+) conductance in diverse cell types. TWIK-1, encoded by the KCNK1 gene, is present in the human heart with robust expression in the atria, however its physiological significance is unknown. To evaluate the cardiac effects of TWIK-1 deficiency, we studied zebrafish embryos after knockdown of the two KCNK1 orthologues, kcnk1a and kcnk1b. Knockdown of kcnk1a or kcnk1b individually caused bradycardia and atrial dilation (p<0.001 vs. controls), while ventricular stroke volume was preserved. Combined knockdown of both kcnk1a and kcnk1b resulted in a more severe phenotype, which was partially reversed by co-injection of wild-type human KCNK1 mRNA, but not by a dominant negative variant of human KCNK1 mRNA. To determine whether genetic variants in KCNK1 might cause atrial fibrillation (AF), we sequenced protein-coding regions in two independent cohorts of patients (373 subjects) and identified three non-synonymous variants, p.R171H, p.I198M and p.G236S, that were all located in highly conserved amino acid residues. In transfected mammalian cells, zebrafish and wild-type human TWIK-1 channels had a similar cellular distribution with predominant localization in the endosomal compartment. Two-electrode voltage-clamp experiments using Xenopus oocytes showed that both zebrafish and wild-type human TWIK-1 channels produced K(+) currents that are sensitive to external K(+) concentration as well as acidic pH. There were no effects of the three KCNK1 variants on cellular localization, current amplitude or reversal potential at pH7.4 or pH6. Our data indicate that TWIK-1 has a highly conserved role in cardiac function and is required for normal heart rate and atrial morphology. Despite the functional importance of TWIK-1 in the atrium, genetic variation in KCNK1 is not a common primary cause of human AF. Copyright © 2016 Elsevier Ltd. All rights reserved.

The potassium channel FaTPK1 plays a critical role in fruit quality formation in strawberry (Fragaria × ananassa).

PubMed

Wang, Shufang; Song, Miaoyu; Guo, Jiaxuan; Huang, Yun; Zhang, Fangfang; Xu, Cheng; Xiao, Yinghui; Zhang, Lusheng

2018-03-01

Potassium (K + ), an abundant cation in plant cells, is important in fruit development and plant resistance. However, how cellular K + is directed by potassium channels in fruit development and quality formation of strawberry (Fragaria × ananassa) is not yet fully clear. Here, a two-pore K + (TPK) channel gene in strawberry, FaTPK1, was cloned using reverse transcription-PCR. A green fluorescent protein subcellular localization analysis showed that FaTPK1 localized in the vacuole membrane. A transcription analysis indicated that the mRNA expression level of FaTPK1 increased rapidly and was maintained at a high level in ripened fruit, which was coupled with the fruit's red colour development, suggesting that FaTPK1 is related to fruit quality formation. The down- and up-regulation of the FaTPK1 mRNA expression levels using RNA interference and overexpression, respectively, inhibited and promoted fruit ripening, respectively, as demonstrated by consistent changes in firmness and the contents of soluble sugars, anthocyanin and abscisic acid, as well as the transcript levels of ripening-regulated genes PG1 (polygalacturonase), GAL6 (beta-galactosidase), XYL2 (D-xylulose reductase), SUT1 (sucrose transporter), CHS (chalcone synthase) and CHI (chalcone flavanone isomerase). Additionally, the regulatory changes influenced fruit resistance to Botrytis cinerea. An isothermal calorimetry analysis showed that the Escherichia coli-expressed FaTPK1 recombinant protein could bind K + with a binding constant of 2.1 × 10 -3  m -1 and a dissociation constant of 476 μm. Thus, the strawberry TPK1 is a ubiquitously expressed, tonoplast-localized two-pore potassium channel that plays important roles in fruit ripening and quality formation. © 2017 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.

Functional interactions at the interface between voltage-sensing and pore domains in the Shaker K(v) channel.

PubMed

Soler-Llavina, Gilberto J; Chang, Tsg-Hui; Swartz, Kenton J

2006-11-22

Voltage-activated potassium (K(v)) channels contain a central pore domain that is partially surrounded by four voltage-sensing domains. Recent X-ray structures suggest that the two domains lack extensive protein-protein contacts within presumed transmembrane regions, but whether this is the case for functional channels embedded in lipid membranes remains to be tested. We investigated domain interactions in the Shaker K(v) channel by systematically mutating the pore domain and assessing tolerance by examining channel maturation, S4 gating charge movement, and channel opening. When mapped onto the X-ray structure of the K(v)1.2 channel the large number of permissive mutations support the notion of relatively independent domains, consistent with crystallographic studies. Inspection of the maps also identifies portions of the interface where residues are sensitive to mutation, an external cluster where mutations hinder voltage sensor activation, and an internal cluster where domain interactions between S4 and S5 helices from adjacent subunits appear crucial for the concerted opening transition.

Studies of potassium-promoted nickel catalysts for methane steam reforming: Effect of surface potassium location

NASA Astrophysics Data System (ADS)

Borowiecki, Tadeusz; Denis, Andrzej; Rawski, Michał; Gołębiowski, Andrzej; Stołecki, Kazimierz; Dmytrzyk, Jaromir; Kotarba, Andrzej

2014-05-01

The effect of potassium addition to the Ni/Al2O3 steam reforming catalyst has been investigated on several model systems, including K/Al2O3 with various amounts of alkali promoters (1-4 wt% of K2O), a model catalyst 90%NiO-10%Al2O3 promoted with potassium and a commercial catalyst. The potassium surface state and stability were investigated by means of the Species Resolved Thermal Alkali Desorption method (SR-TAD). The activity of the catalysts in the steam reforming of methane and their coking-resistance were also evaluated. The results reveal that the beneficial effect of potassium addition is strongly related to its location in the catalysts. The catalyst surface should be promoted with potassium in order to obtain high coking-resistant catalysts. Moreover, the catalyst preparation procedure should ensure a direct interaction of potassium with the Al2O3 support surface. Due to the low stability of potassium on θ-Al2O3 this phase is undesirable during the preparation of a stable steam reforming catalyst.

The Effect of the Pore Entrance on Particle Motion in Slit Pores: Implications for Ultrathin Membranes

PubMed Central

Delavari, Armin; Baltus, Ruth

2017-01-01

Membrane rejection models generally neglect the effect of the pore entrance on intrapore particle transport. However, entrance effects are expected to be particularly important with ultrathin membranes, where membrane thickness is typically comparable to pore size. In this work, a 2D model was developed to simulate particle motion for spherical particles moving at small Re and infinite Pe from the reservoir outside the pore into a slit pore. Using a finite element method, particles were tracked as they accelerated across the pore entrance until they reached a steady velocity in the pore. The axial position in the pore where particle motion becomes steady is defined as the particle entrance length (PEL). PELs were found to be comparable to the fluid entrance length, larger than the pore size and larger than the thickness typical of many ultrathin membranes. Results also show that, in the absence of particle diffusion, hydrodynamic particle–membrane interactions at the pore mouth result in particle “funneling” in the pore, yielding cross-pore particle concentration profiles focused at the pore centerline. The implications of these phenomena on rejection from ultrathin membranes are examined. PMID:28796197

Pore dynamics in lipid membranes

NASA Astrophysics Data System (ADS)

Gozen, I.; Dommersnes, P.

2014-09-01

Transient circular pores can open in plasma membrane of cells due to mechanical stress, and failure to repair such pores lead to cell death. Similar pores in the form of defects also exist among smectic membranes, such as in myelin sheaths or mitochondrial membranes. The formation and growth of membrane defects are associated with diseases, for example multiple sclerosis. A deeper understanding of membrane pore dynamics can provide a more refined picture of membrane integrity-related disease development, and possibly also treatment options and strategies. Pore dynamics is also of great importance regarding healthcare applications such as drug delivery, gene or as recently been implied, cancer therapy. The dynamics of pores significantly differ in stacks which are confined in 2D compared to those in cells or vesicles. In this short review, we will summarize the dynamics of different types of pores that can be observed in biological membranes, which include circular transient, fusion and hemi-fusion pores. We will dedicate a section to floral and fractal pores which were discovered a few years ago and have highly peculiar characteristics. Finally, we will discuss the repair mechanisms of large area pores in conjunction with the current cell membrane repair hypotheses.

21 CFR 184.1631 - Potassium hydroxide.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Potassium hydroxide. 184.1631 Section 184.1631... Listing of Specific Substances Affirmed as GRAS § 184.1631 Potassium hydroxide. (a) Potassium hydroxide..., including pellets, flakes, sticks, lumps, and powders. Potassium hydroxide is obtained commercially from the...

21 CFR 184.1631 - Potassium hydroxide.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Potassium hydroxide. 184.1631 Section 184.1631... Listing of Specific Substances Affirmed as GRAS § 184.1631 Potassium hydroxide. (a) Potassium hydroxide..., including pellets, flakes, sticks, lumps, and powders. Potassium hydroxide is obtained commercially from the...

21 CFR 184.1622 - Potassium chloride.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Potassium chloride. 184.1622 Section 184.1622 Food... Specific Substances Affirmed as GRAS § 184.1622 Potassium chloride. (a) Potassium chloride (KCl, CAS Reg... levels not to exceed current good manufacturing practice. Potassium chloride may be used in infant...

21 CFR 184.1622 - Potassium chloride.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Potassium chloride. 184.1622 Section 184.1622 Food... Specific Substances Affirmed as GRAS § 184.1622 Potassium chloride. (a) Potassium chloride (KCl, CAS Reg... levels not to exceed current good manufacturing practice. Potassium chloride may be used in infant...

21 CFR 184.1610 - Potassium alginate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Potassium alginate. 184.1610 Section 184.1610 Food... Specific Substances Affirmed as GRAS § 184.1610 Potassium alginate. (a) Potassium alginate (CAS Reg. No. 9005-36-1) is the potassium salt of alginic acid, a natural polyuronide constituent of certain brown...

21 CFR 172.375 - Potassium iodide.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Potassium iodide. 172.375 Section 172.375 Food and... Dietary and Nutritional Additives § 172.375 Potassium iodide. The food additive potassium iodide may be safely used in accordance with the following prescribed conditions: (a) Potassium iodide may be safely...

21 CFR 184.1610 - Potassium alginate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Potassium alginate. 184.1610 Section 184.1610 Food... Specific Substances Affirmed as GRAS § 184.1610 Potassium alginate. (a) Potassium alginate (CAS Reg. No. 9005-36-1) is the potassium salt of alginic acid, a natural polyuronide constituent of certain brown...

A new HF-resistant tandem spray chamber for improved determination of trace elements and Pb isotopes using inductively coupled plasma-mass spectrometry

NASA Astrophysics Data System (ADS)

Krachler, Michael; Rausch, Nicole; Feuerbacher, Helmut; Klemens, Patrick

2005-07-01

The use of a new HF-resistant tandem spray chamber arrangement consisting of a cyclonic spray chamber and a Scott-type spray chamber made from PFA and PEEK provides a straightforward approach for improving the performance of inductively coupled-mass spectrometry (ICP-MS). The characteristics of the tandem spray chamber were critically evaluated against a PEEK cyclonic and a PFA Scott-type spray chamber, respectively. Sensitivity across the entire mass range was increased by about three times compared to the conventional setup utilizing only one spray chamber. Precision of the results, especially at low signal intensities, improved by 160% and 31% compared to the cyclonic and Scott-type spray chamber, respectively. Using the tandem spray chamber, the oxide formation rate was lowered by about 50%. Signals as low as 30 counts could be determined under routine measurement conditions with a RSD of 2.4% thus allowing to precisely quantify small concentration differences at the ng l - 1 concentration level. The excellent precision (0.02-0.07%) of 206Pb / 207Pb and 206Pb / 208Pb ratios determined in pore water samples was rather limited by the instrumental capabilities of the single collector ICP-MS instrument than by the performance of the tandem spray chamber.

21 CFR 184.1643 - Potassium sulfate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Potassium sulfate. 184.1643 Section 184.1643 Food... Specific Substances Affirmed as GRAS § 184.1643 Potassium sulfate. (a) Potassium sulfate (K2SO4, CAS Reg... having a bitter, saline taste. It is prepared by the neutralization of sulfuric acid with potassium...

21 CFR 184.1619 - Potassium carbonate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Potassium carbonate. 184.1619 Section 184.1619... GRAS § 184.1619 Potassium carbonate. (a) Potassium carbonate (K2CO3, CAS Reg. No. 584-08-7) is produced by the following methods of manufacture: (1) By electrolysis of potassium chloride followed by...

21 CFR 184.1613 - Potassium bicarbonate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Potassium bicarbonate. 184.1613 Section 184.1613... GRAS § 184.1613 Potassium bicarbonate. (a) Potassium bicarbonate (KHCO3, CAS Reg. No. 298-14-6) is made by the following processes: (1) By treating a solution of potassium hydroxide with carbon dioxide; (2...

21 CFR 184.1643 - Potassium sulfate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Potassium sulfate. 184.1643 Section 184.1643 Food... Specific Substances Affirmed as GRAS § 184.1643 Potassium sulfate. (a) Potassium sulfate (K2SO4, CAS Reg... having a bitter, saline taste. It is prepared by the neutralization of sulfuric acid with potassium...

21 CFR 184.1643 - Potassium sulfate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Potassium sulfate. 184.1643 Section 184.1643 Food... Specific Substances Affirmed as GRAS § 184.1643 Potassium sulfate. (a) Potassium sulfate (K2SO4, CAS Reg... having a bitter, saline taste. It is prepared by the neutralization of sulfuric acid with potassium...

21 CFR 184.1643 - Potassium sulfate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Potassium sulfate. 184.1643 Section 184.1643 Food... Specific Substances Affirmed as GRAS § 184.1643 Potassium sulfate. (a) Potassium sulfate (K2SO4, CAS Reg... having a bitter, saline taste. It is prepared by the neutralization of sulfuric acid with potassium...

21 CFR 184.1634 - Potassium iodide.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Potassium iodide. 184.1634 Section 184.1634 Food... Specific Substances Affirmed as GRAS § 184.1634 Potassium iodide. (a) Potassium iodide (KI, CAS Reg. No. 7681-11-0) is the potassium salt of hydriodic acid. It occurs naturally in sea water and in salt...

21 CFR 184.1634 - Potassium iodide.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Potassium iodide. 184.1634 Section 184.1634 Food... Specific Substances Affirmed as GRAS § 184.1634 Potassium iodide. (a) Potassium iodide (KI, CAS Reg. No. 7681-11-0) is the potassium salt of hydriodic acid. It occurs naturally in sea water and in salt...

21 CFR 184.1635 - Potassium iodate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Potassium iodate. 184.1635 Section 184.1635 Food... Specific Substances Affirmed as GRAS § 184.1635 Potassium iodate. (a) Potassium iodate (KIO3, CAS Reg. No. 7758-05-6) does not occur naturally but can be prepared by reacting iodine with potassium hydroxide. (b...

21 CFR 184.1635 - Potassium iodate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Potassium iodate. 184.1635 Section 184.1635 Food... Specific Substances Affirmed as GRAS § 184.1635 Potassium iodate. (a) Potassium iodate (KIO3, CAS Reg. No. 7758-05-6) does not occur naturally but can be prepared by reacting iodine with potassium hydroxide. (b...

21 CFR 184.1635 - Potassium iodate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Potassium iodate. 184.1635 Section 184.1635 Food... Specific Substances Affirmed as GRAS § 184.1635 Potassium iodate. (a) Potassium iodate (KIO3, CAS Reg. No. 7758-05-6) does not occur naturally but can be prepared by reacting iodine with potassium hydroxide. (b...

21 CFR 184.1634 - Potassium iodide.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Potassium iodide. 184.1634 Section 184.1634 Food... Specific Substances Affirmed as GRAS § 184.1634 Potassium iodide. (a) Potassium iodide (KI, CAS Reg. No. 7681-11-0) is the potassium salt of hydriodic acid. It occurs naturally in sea water and in salt...

21 CFR 184.1634 - Potassium iodide.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Potassium iodide. 184.1634 Section 184.1634 Food... Specific Substances Affirmed as GRAS § 184.1634 Potassium iodide. (a) Potassium iodide (KI, CAS Reg. No. 7681-11-0) is the potassium salt of hydriodic acid. It occurs naturally in sea water and in salt...

21 CFR 184.1635 - Potassium iodate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Potassium iodate. 184.1635 Section 184.1635 Food... Specific Substances Affirmed as GRAS § 184.1635 Potassium iodate. (a) Potassium iodate (KIO3, CAS Reg. No. 7758-05-6) does not occur naturally but can be prepared by reacting iodine with potassium hydroxide. (b...

21 CFR 184.1622 - Potassium chloride.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Potassium chloride. 184.1622 Section 184.1622 Food... GRAS § 184.1622 Potassium chloride. (a) Potassium chloride (KCl, CAS Reg. No. 7447-40-7) is a white... manufacturing practice. Potassium chloride may be used in infant formula in accordance with section 412(g) of...

21 CFR 184.1635 - Potassium iodate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Potassium iodate. 184.1635 Section 184.1635 Food... GRAS § 184.1635 Potassium iodate. (a) Potassium iodate (KIO3, CAS Reg. No. 7758-05-6) does not occur naturally but can be prepared by reacting iodine with potassium hydroxide. (b) The ingredient meets the...

Estimating Sodium and Potassium Intakes and Their Ratio in the American Diet: Data from the 2011-2012 NHANES.

PubMed

Bailey, Regan L; Parker, Elizabeth A; Rhodes, Donna G; Goldman, Joseph D; Clemens, John C; Moshfegh, Alanna J; Thuppal, Sowmyanarayanan V; Weaver, Connie M

2016-03-09

The dietary sodium-to-potassium ratio (Na:K) is shown to be more strongly associated with an increased risk of cardiovascular disease (CVD) and CVD-related mortality than either sodium or potassium intake alone. The aim was to estimate the Na:K in the diet of US adults. Among US adults from the 2011-2012 NHANES (≥20 y; 2393 men and 2337 women), the National Cancer Institute method was used to estimate sodium and potassium intakes, Na:K, and the percentage of individuals with Na:K <1.0 utilizing the complex, stratified, multistage probability cluster sampling design. Overall, women had a significantly lower Na:K than men (mean ± SE: 1.32 ± 0.02 compared with 1.45 ± 0.02). Non-Hispanic whites had a significantly lower Na:K than non-Hispanic blacks and non-Hispanic Asians (1.34 ± 0.02 compared with 1.54 ± 0.03 and 1.49 ± 0.04, respectively). Only 12.2% ± 1.5% of US adults had a Na:K < 1.0. The Na:K decreased linearly as age increased. Most adults (90% ± 0.8%) had sodium intakes >2300 mg/d, whereas <3% had potassium intakes >4700 mg/d. Grains and vegetables were among the highest contributors to sodium intakes for adults with Na:K < 1.0, compared with protein foods and grains for those with Na:K ≥ 1.0. Vegetables and milk and dairy products constituted the primary dietary sources of potassium for individuals with Na:K < 1.0, whereas mixed dishes and protein foods contributed the most potassium for individuals with ratios ≥1.0. Individuals with a Na:K < 1.0 were less likely to consume mixed dishes and condiments and were more likely to consume vegetables, milk and dairy products, and fruit than those with a Na:K ≥ 1.0. Only about one-tenth of US adults have a Na:K consistent with the WHO guidelines for reduced risk of mortality. Continued efforts to reduce sodium intake in tandem with novel strategies to increase potassium intake are warranted. © 2016 American Society for Nutrition.

Achieving 15% Tandem Polymer Solar Cells

DTIC Science & Technology

2015-06-23

solar cell structures – both polymer only and hybrid tandem cells to constantly pushing the envelope of solution processed solar cell ...performance – 11.6% polymer tandem cell , 7% transparent tandem polymer cell , and over 10% PCE hybrid tandem solar cells were achieved. In addition, AFOSR’s...final support also enabled us to explore novel hybrid perovskite solar cells in depth. For example, single junction cell efficiency

Differences in soluble organic carbon chemistry in pore waters sampled from different pore size domains

DOE PAGES

Bailey, Vanessa L.; Smith, A. P.; Tfaily, Malak; ...

2017-01-11

Spatial isolation of soil organic carbon (SOC) in different sized pores may be a mechanism by which otherwise labile carbon (C) could be protected in soils. When soil water content increases, the hydrologic connectivity of soil pores also increases, allowing greater transport of SOC and other resources from protected locations, to microbially colonized locations more favorable to decomposition. The heterogeneous distribution of specialized decomposers, C, and other resources throughout the soil indicates that the metabolism or persistence of soil C compounds is highly dependent on short-distance transport processes. The objective of this research was to characterize the complexity of Cmore » in pore waters held at weak and strong water tensions (effectively soil solution held behind coarse- and fine-pore throats, respectively) and evaluate the microbial decomposability of these pore waters. We saturated intact soil cores and extracted pore waters with increasing suction pressures to sequentially sample pore waters from increasingly fine pore domains. Ultrahigh resolution mass spectrometry of the SOC was used to profile the major biochemical classes (i.e., lipids, proteins, lignin, carbohydrates, and condensed aromatics) of compounds present in the pore waters; some of these samples were then used as substrates for growth of Cellvibrio japonicus (DSMZ 16018), Streptomyces cellulosae (ATCC ® 25439™), and Trichoderma reseei (QM6a) in 7 day incubations. The soluble C in finer pores was more complex than the soluble C in coarser pores, and the incubations revealed that the more complex C in these fine pores is not recalcitrant. The decomposition of this complex C led to greater losses of C through respiration than the simpler C from coarser pore waters. Our research suggests that soils that experience repeated cycles of drying and wetting may be accompanied by repeated cycles of increased CO 2 fluxes that are driven by i) the transport of C from protected pools

Differences in soluble organic carbon chemistry in pore waters sampled from different pore size domains

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bailey, Vanessa L.; Smith, A. P.; Tfaily, Malak

Spatial isolation of soil organic carbon (SOC) in different sized pores may be a mechanism by which otherwise labile carbon (C) could be protected in soils. When soil water content increases, the hydrologic connectivity of soil pores also increases, allowing greater transport of SOC and other resources from protected locations, to microbially colonized locations more favorable to decomposition. The heterogeneous distribution of specialized decomposers, C, and other resources throughout the soil indicates that the metabolism or persistence of soil C compounds is highly dependent on short-distance transport processes. The objective of this research was to characterize the complexity of Cmore » in pore waters held at weak and strong water tensions (effectively soil solution held behind coarse- and fine-pore throats, respectively) and evaluate the microbial decomposability of these pore waters. We saturated intact soil cores and extracted pore waters with increasing suction pressures to sequentially sample pore waters from increasingly fine pore domains. Ultrahigh resolution mass spectrometry of the SOC was used to profile the major biochemical classes (i.e., lipids, proteins, lignin, carbohydrates, and condensed aromatics) of compounds present in the pore waters; some of these samples were then used as substrates for growth of Cellvibrio japonicus (DSMZ 16018), Streptomyces cellulosae (ATCC ® 25439™), and Trichoderma reseei (QM6a) in 7 day incubations. The soluble C in finer pores was more complex than the soluble C in coarser pores, and the incubations revealed that the more complex C in these fine pores is not recalcitrant. The decomposition of this complex C led to greater losses of C through respiration than the simpler C from coarser pore waters. Our research suggests that soils that experience repeated cycles of drying and wetting may be accompanied by repeated cycles of increased CO 2 fluxes that are driven by i) the transport of C from protected pools

Active pore space utilization in nanoporous carbon-based supercapacitors: Effects of conductivity and pore accessibility

NASA Astrophysics Data System (ADS)

Seredych, Mykola; Koscinski, Mikolaj; Sliwinska-Bartkowiak, Malgorzata; Bandosz, Teresa J.

2012-12-01

Composites of commercial graphene and nanoporous sodium-salt-polymer-derived carbons were prepared with 5 or 20 weight% graphene. The materials were characterized using the adsorption of nitrogen, SEM/EDX, thermal analysis, Raman spectroscopy and potentiometric titration. The samples' conductivity was also measured. The performance of the carbon composites in energy storage was linked to their porosity and electronic conductivity. The small pores (<0.7) were found as very active for double layer capacitance. It was demonstrated that when double layer capacitance is a predominant mechanism of charge storage, the degree of the pore space utilization for that storage can be increased by increasing the conductivity of the carbons. That active pore space utilization is defined as gravimetric capacitance per unit pore volume in pores smaller than 0.7 nm. Its magnitude is affected by conductivity of the carbon materials. The functional groups, besides pseudocapacitive contribution, increased the wettability and thus the degree of the pore space utilization. Graphene phase, owing to its conductivity, also took part in an insitu increase of the small pore accessibility and thus the capacitance of the composites via enhancing an electron transfer to small pores and thus imposing the reduction of groups blocking the pores for electrolyte ions.

The heart and potassium: a banana republic.

PubMed

Khan, Ehsan; Spiers, Christine; Khan, Maria

2013-03-01

The importance of potassium in maintaining stable cardiac function is a clinically understood phenomenon. Physiologically the importance of potassium in cardiac function is described by the large number of different kinds of potassium ions channels found in the heart compared to channels and membrane transport mechanisms for other ions such as sodium and calcium. Potassium is important in physiological homeostatic control of cardiac function, but is also of relevance to the diseased state, as potassium-related effects may stabilize or destabilize cardiac function. This article aims to provide a detailed understanding of potassium-mediated cardiac function. This will help the clinical practitioner evaluate how modulation of potassium ion channels by disease and pharmacological manipulation affect the cardiac patient, thus aiding in decision making when faced with clinical problems related to potassium.

Disulfide mapping the voltage-sensing mechanism of a voltage-dependent potassium channel.

PubMed

Nozaki, Tomohiro; Ozawa, Shin-Ichiro; Harada, Hitomi; Kimura, Tomomi; Osawa, Masanori; Shimada, Ichio

2016-11-17

Voltage-dependent potassium (Kv) channels allow for the selective permeability of potassium ions in a membrane potential dependent manner, playing crucial roles in neurotransmission and muscle contraction. Kv channel is a tetramer, in which each subunit possesses a voltage-sensing domain (VSD) and a pore domain (PD). Although several lines of evidence indicated that membrane depolarization is sensed as the movement of helix S4 of the VSD, the detailed voltage-sensing mechanism remained elusive, due to the difficulty of structural analyses at resting potential. In this study, we conducted a comprehensive disulfide locking analysis of the VSD using 36 double Cys mutants, in order to identify the proximal residue pairs of the VSD in the presence or absence of a membrane potential. An intramolecular SS-bond was formed between 6 Cys pairs under both polarized and depolarized environment, and one pair only under depolarized environment. The multiple conformations captured by the SS-bond can be divided by two states, up and down, where S4 lies on the extracellular and intracellular sides of the membrane, respectively, with axial rotation of 180°. The transition between these two states is caused by the S4 translocation of 12 Å, enabling allosteric regulation of the gating at the PD.

Toxin-induced conformational changes in a potassium channel revealed by solid-state NMR

NASA Astrophysics Data System (ADS)

Lange, Adam; Giller, Karin; Hornig, Sönke; Martin-Eauclaire, Marie-France; Pongs, Olaf; Becker, Stefan; Baldus, Marc

2006-04-01

The active site of potassium (K+) channels catalyses the transport of K+ ions across the plasma membrane-similar to the catalytic function of the active site of an enzyme-and is inhibited by toxins from scorpion venom. On the basis of the conserved structures of K+ pore regions and scorpion toxins, detailed structures for the K+ channel-scorpion toxin binding interface have been proposed. In these models and in previous solution-state nuclear magnetic resonance (NMR) studies using detergent-solubilized membrane proteins, scorpion toxins were docked to the extracellular entrance of the K+ channel pore assuming rigid, preformed binding sites. Using high-resolution solid-state NMR spectroscopy, here we show that high-affinity binding of the scorpion toxin kaliotoxin to a chimaeric K+ channel (KcsA-Kv1.3) is associated with significant structural rearrangements in both molecules. Our approach involves a combined analysis of chemical shifts and proton-proton distances and demonstrates that solid-state NMR is a sensitive method for analysing the structure of a membrane protein-inhibitor complex. We propose that structural flexibility of the K+ channel and the toxin represents an important determinant for the high specificity of toxin-K+ channel interactions.

21 CFR 184.1625 - Potassium citrate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Potassium citrate. 184.1625 Section 184.1625 Food... Specific Substances Affirmed as GRAS § 184.1625 Potassium citrate. (a) Potassium citrate (C6H5K3O7·H2O, CAS Reg. No. 006100-0905-096) is the potassium salt of citric acid. It is prepared by neutralizing citric...

21 CFR 184.1625 - Potassium citrate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Potassium citrate. 184.1625 Section 184.1625 Food... Specific Substances Affirmed as GRAS § 184.1625 Potassium citrate. (a) Potassium citrate (C6H5K3O7·H2O, CAS Reg. No. 006100-0905-096) is the potassium salt of citric acid. It is prepared by neutralizing citric...

21 CFR 184.1625 - Potassium citrate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Potassium citrate. 184.1625 Section 184.1625 Food... Specific Substances Affirmed as GRAS § 184.1625 Potassium citrate. (a) Potassium citrate (C6H5K3O7·H2O, CAS Reg. No. 006100-0905-096) is the potassium salt of citric acid. It is prepared by neutralizing citric...

21 CFR 184.1625 - Potassium citrate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Potassium citrate. 184.1625 Section 184.1625 Food... Specific Substances Affirmed as GRAS § 184.1625 Potassium citrate. (a) Potassium citrate (C6H5K3O7·H2O, CAS Reg. No. 006100-0905-096) is the potassium salt of citric acid. It is prepared by neutralizing citric...

A ditopic fluorescent sensor for potassium fluoride.

PubMed

Koskela, Suvi J M; Fyles, Thomas M; James, Tony D

2005-02-21

The addition of potassium fluoride 'switches on' the fluorescence of sensors and while potassium chloride and bromide cause no fluorescence change; the fluorescence can be 'switched off' by removing the potassium cation from the benzocrown ether receptors of sensors and through the addition of [2.2.2]-cryptand and restored by the addition of the potassium cation as potassium chloride.

21 CFR 184.1077 - Potassium acid tartrate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Potassium acid tartrate. 184.1077 Section 184.1077... GRAS § 184.1077 Potassium acid tartrate. (a) Potassium acid tartrate (C4H5KO6, CAS Reg. No. 868-14-4) is the potassium acid salt of l−(+)−tartaric acid and is also called potassium bitartrate or cream of...

Genetics Home Reference: potassium-aggravated myotonia

MedlinePlus

... Facebook Twitter Home Health Conditions Potassium-aggravated myotonia Potassium-aggravated myotonia Printable PDF Open All Close All ... Javascript to view the expand/collapse boxes. Description Potassium-aggravated myotonia is a disorder that affects muscles ...

Can Diuretics Decrease Your Potassium Level?

MedlinePlus

... of low potassium? Can diuretics decrease your potassium level? Answers from Sheldon G. Sheps, M.D. Yes, ... your urine. This can lead to low potassium levels in your blood (hypokalemia). Signs and symptoms of ...

A Green Approach to High-Performance Supercapacitor Electrodes: The Chemical Activation of Hydrochar with Potassium Bicarbonate.

PubMed

Sevilla, Marta; Fuertes, Antonio B

2016-07-21

Sustainable synthesis schemes for the production of porous carbons with appropriate textural properties for use as supercapacitor electrodes are in high demand. In this work a greener option to the widely used but corrosive KOH is proposed for the production of highly porous carbons. Hydrochar products are used as carbon precursors. It is demonstrated that a mild alkaline potassium salt such as potassium bicarbonate is very effective to generate porosity in hydrochar to lead to materials with large surface areas (> 2000 m(2)  g(-1) ) and a tunable pore size distribution. Furthermore, the use of KHCO3 instead of KOH gives rise to a significant 10 % increase in the yield of activated carbon, and the spherical morphology of hydrochar is retained, which translates into better packing properties and reduced ion diffusion distances. These features lead to a supercapacitor performance that can compete with, and even surpass, that of KOH-activated hydrochar in a variety of electrolytes. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Extracellular Potassium Homeostasis: Insights from Hypokalemic Periodic Paralysis

PubMed Central

Cheng, Chih-Jen; Kuo, Elizabeth; Huang, Chou-Long

2014-01-01

The extracellular potassium makes up only about 2% of the total body potassium store. The majority of the body potassium is distributed in the intracellular space, and of which about 80% is in skeletal muscle. Movement of potassium in and out of skeletal muscle thus plays a pivotal role in extracellular potassium homeostasis. The exchange of potassium between the extracellular space and skeletal muscle is mediated by specific membrane transporters. These include potassium uptake by Na+, K+-ATPase and release by inward rectifier K+ channels. These processes are regulated by circulating hormones, peptides, ions, and by physical activity of muscle as well as dietary potassium intake. Pharmaceutical agents, poisons and disease conditions also affect the exchange and alter extracellular potassium concentration. Here, we review extracellular potassium homeostasis focusing on factors and conditions that influence the balance of potassium movement in skeletal muscle. Recent findings that mutations of a skeletal muscle-specific inward rectifier K+ channel cause hypokalemic periodic paralysis provide interesting insights into the role of skeletal muscle in extracellular potassium homeostasis. These recent findings will be reviewed. PMID:23953801

Role of Circadian Rhythms in Potassium Homeostasis

PubMed Central

Gumz, Michelle L.; Rabinowitz, Lawrence

2013-01-01

It has been known for decades that urinary potassium excretion varies with a circadian pattern. In this review, we consider the historical evidence for this phenomenon and present an overview of recent developments in the field. Extensive evidence from the latter part of the last century clearly demonstrates that circadian potassium excretion does not depend on endogenous aldosterone. Of note is the recent discovery that the expression of several renal potassium transporters varies with a circadian pattern that appears to be consistent with substantial clinical data regarding daily fluctuations in urinary potassium levels. We propose the circadian clock mechanism as a key regulator of renal potassium transporters, and consequently renal potassium excretion. Further investigation into the mechanism of regulation of renal potassium transport by the circadian clock is warranted in order to increase our understanding of the clinical relevance of circadian rhythms to potassium homeostasis. PMID:23953800

TANDEM: matching proteins with tandem mass spectra.

PubMed

Craig, Robertson; Beavis, Ronald C

2004-06-12

Tandem mass spectra obtained from fragmenting peptide ions contain some peptide sequence specific information, but often there is not enough information to sequence the original peptide completely. Several proprietary software applications have been developed to attempt to match the spectra with a list of protein sequences that may contain the sequence of the peptide. The application TANDEM was written to provide the proteomics research community with a set of components that can be used to test new methods and algorithms for performing this type of sequence-to-data matching. The source code and binaries for this software are available at http://www.proteome.ca/opensource.html, for Windows, Linux and Macintosh OSX. The source code is made available under the Artistic License, from the authors.

Preventing Mesh Pore Collapse by Designing Mesh Pores With Auxetic Geometries: A Comprehensive Evaluation Via Computational Modeling.

PubMed

Knight, Katrina M; Moalli, Pamela A; Abramowitch, Steven D

2018-05-01

Pelvic organ prolapse (POP) meshes are exposed to predominately tensile loading conditions in vivo that can lead to pore collapse by 70-90%, decreasing overall porosity and providing a plausible mechanism for the contraction/shrinkage of mesh observed following implantation. To prevent pore collapse, we proposed to design synthetic meshes with a macrostructure that results in auxetic behavior, the pores expand laterally, instead of contracting when loaded. Such behavior can be achieved with a range of auxetic structures/geometries. This study utilized finite element analysis (FEA) to assess the behavior of mesh models with eight auxetic pore geometries subjected to uniaxial loading to evaluate their potential to allow for pore expansion while simultaneously providing resistance to tensile loading. Overall, substituting auxetic geometries for standard pore geometries yielded more pore expansion, but often at the expense of increased model elongation, with two of the eight auxetics not able to maintain pore expansion at higher levels of tension. Meshes with stable pore geometries that remain open with loading will afford the ingrowth of host tissue into the pores and improved integration of the mesh. Given the demonstrated ability of auxetic geometries to allow for pore size maintenance (and pore expansion), auxetically designed meshes have the potential to significantly impact surgical outcomes and decrease the likelihood of major mesh-related complications.

Antera 3D capabilities for pore measurements.

PubMed

Messaraa, C; Metois, A; Walsh, M; Flynn, J; Doyle, L; Robertson, N; Mansfield, A; O'Connor, C; Mavon, A

2018-04-29

The cause of enlarged pores remains obscure but still remains of concern for women. To complement subjective methods, bioengineered methods are needed for quantification of pores visibility following treatments. The study objective was to demonstrate the suitability of pore measurements from the Antera 3D. Pore measurements were collected on 22 female volunteers aged 18-65 years with the Antera 3D, the DermaTOP and image analysis on photographs. Additionally, 4 raters graded pore size on photographs on a scale 0-5. Repeatability of Antera 3D parameters was ascertained and the benefit of a pore minimizer product on the cheek was assessed on a sub panel of seven female volunteers. Pore parameters using the Antera were shown to depict pore severity similar to raters on photographs, except for Max Depth. Mean pore volume, mean pore area and count were moderately correlated with DermaTOP parameters (up to r = .50). No relationship was seen between the Antera 3D and pore visibility analysis on photographs. The most repeatable parameters were found to be mean pore volume, mean pore area and max depth, especially for the small and medium filters. The benefits of a pore minimizer product were the most striking for mean pore volume and mean pore area when using the small filter for analysis, rather than the medium/large ones. Pore measurements with the Antera 3D represent a reliable tool for efficacy and field studies, with an emphasis of the small filter for analysis for the mean pore volume/mean pore area parameters. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

21 CFR 182.3637 - Potassium metabisulfite.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Potassium metabisulfite. 182.3637 Section 182.3637...) SUBSTANCES GENERALLY RECOGNIZED AS SAFE Chemical Preservatives § 182.3637 Potassium metabisulfite. (a) Product. Potassium metabisulfite. (b) [Reserved] (c) Limitations, restrictions, or explanation. This...

Physicochemical action of potassium-magnesium citrate in nephrolithiasis

NASA Technical Reports Server (NTRS)

Pak, C. Y.; Koenig, K.; Khan, R.; Haynes, S.; Padalino, P.

1992-01-01

Effect of potassium-magnesium citrate on urinary biochemistry and crystallization of stone-forming salts was compared with that of potassium citrate at same dose of potassium in five normal subjects and five patients with calcium nephrolithiasis. Compared to the placebo phase, urinary pH rose significantly from 6.06 +/- 0.27 to 6.48 +/- 0.36 (mean +/- SD, p less than 0.0167) during treatment with potassium citrate (50 mEq/day for 7 days) and to 6.68 +/- 0.31 during therapy with potassium-magnesium citrate (containing 49 mEq K, 24.5 mEq Mg, and 73.5 mEq citrate per day). Urinary pH was significantly higher during potassium-magnesium citrate than during potassium citrate therapy. Thus, the amount of undissociated uric acid declined from 118 +/- 61 mg/day during the placebo phase to 68 +/- 54 mg/day during potassium citrate treatment and, more prominently, to 41 +/- 46 mg/day during potassium-magnesium citrate therapy. Urinary magnesium rose significantly from 102 +/- 25 to 146 +/- 37 mg/day during potassium-magnesium citrate therapy but not during potassium citrate therapy. Urinary citrate rose more prominently during potassium-magnesium citrate therapy (to 1027 +/- 478 mg/day from 638 +/- 252 mg/day) than during potassium citrate treatment (to 932 +/- 297 mg/day). Consequently, urinary saturation (activity product) of calcium oxalate declined significantly (from 1.49 x 10(-8) to 1.03 x 10(-8) M2) during potassium-magnesium citrate therapy and marginally (to 1.14 x 10(-8) M2) during potassium citrate therapy.(ABSTRACT TRUNCATED AT 250 WORDS).

Visualization of Membrane Pore in Live Cells Reveals a Dynamic-Pore Theory Governing Fusion and Endocytosis.

PubMed

Shin, Wonchul; Ge, Lihao; Arpino, Gianvito; Villarreal, Seth A; Hamid, Edaeni; Liu, Huisheng; Zhao, Wei-Dong; Wen, Peter J; Chiang, Hsueh-Cheng; Wu, Ling-Gang

2018-05-03

Fusion is thought to open a pore to release vesicular cargoes vital for many biological processes, including exocytosis, intracellular trafficking, fertilization, and viral entry. However, fusion pores have not been observed and thus proved in live cells. Its regulatory mechanisms and functions remain poorly understood. With super-resolution STED microscopy, we observed dynamic fusion pore behaviors in live (neuroendocrine) cells, including opening, expansion, constriction, and closure, where pore size may vary between 0 and 490 nm within 26 milliseconds to seconds (vesicle size: 180-720 nm). These pore dynamics crucially determine the efficiency of vesicular cargo release and vesicle retrieval. They are generated by competition between pore expansion and constriction. Pharmacology and mutation experiments suggest that expansion and constriction are mediated by F-actin-dependent membrane tension and calcium/dynamin, respectively. These findings provide the missing live-cell evidence, proving the fusion-pore hypothesis, and establish a live-cell dynamic-pore theory accounting for fusion, fission, and their regulation. Published by Elsevier Inc.

21 CFR 182.3616 - Potassium bisulfite.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Potassium bisulfite. 182.3616 Section 182.3616 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD....3616 Potassium bisulfite. (a) Product. Potassium bisulfite. (b) [Reserved] (c) Limitations...

21 CFR 182.3637 - Potassium metabisulfite.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Potassium metabisulfite. 182.3637 Section 182.3637 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD....3637 Potassium metabisulfite. (a) Product. Potassium metabisulfite. (b) [Reserved] (c) Limitations...

21 CFR 182.3637 - Potassium metabisulfite.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Potassium metabisulfite. 182.3637 Section 182.3637 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD....3637 Potassium metabisulfite. (a) Product. Potassium metabisulfite. (b) [Reserved] (c) Limitations...

21 CFR 582.3637 - Potassium metabisulfite.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Potassium metabisulfite. 582.3637 Section 582.3637 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL....3637 Potassium metabisulfite. (a) Product. Potassium metabisulfite. (b) [Reserved] (c) Limitations...

21 CFR 182.3616 - Potassium bisulfite.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Potassium bisulfite. 182.3616 Section 182.3616 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD....3616 Potassium bisulfite. (a) Product. Potassium bisulfite. (b) [Reserved] (c) Limitations...

21 CFR 582.3616 - Potassium bisulfite.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Potassium bisulfite. 582.3616 Section 582.3616 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL....3616 Potassium bisulfite. (a) Product. Potassium bisulfite. (b) [Reserved] (c) Limitations...

21 CFR 182.3616 - Potassium bisulfite.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Potassium bisulfite. 182.3616 Section 182.3616 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD....3616 Potassium bisulfite. (a) Product. Potassium bisulfite. (b) [Reserved] (c) Limitations...

21 CFR 182.3637 - Potassium metabisulfite.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Potassium metabisulfite. 182.3637 Section 182.3637 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD....3637 Potassium metabisulfite. (a) Product. Potassium metabisulfite. (b) [Reserved] (c) Limitations...

21 CFR 582.3637 - Potassium metabisulfite.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Potassium metabisulfite. 582.3637 Section 582.3637 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL....3637 Potassium metabisulfite. (a) Product. Potassium metabisulfite. (b) [Reserved] (c) Limitations...

21 CFR 582.3616 - Potassium bisulfite.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Potassium bisulfite. 582.3616 Section 582.3616 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL....3616 Potassium bisulfite. (a) Product. Potassium bisulfite. (b) [Reserved] (c) Limitations...

21 CFR 582.3637 - Potassium metabisulfite.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Potassium metabisulfite. 582.3637 Section 582.3637 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL....3637 Potassium metabisulfite. (a) Product. Potassium metabisulfite. (b) [Reserved] (c) Limitations...

21 CFR 582.3616 - Potassium bisulfite.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Potassium bisulfite. 582.3616 Section 582.3616 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL....3616 Potassium bisulfite. (a) Product. Potassium bisulfite. (b) [Reserved] (c) Limitations...

21 CFR 582.3637 - Potassium metabisulfite.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Potassium metabisulfite. 582.3637 Section 582.3637 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL....3637 Potassium metabisulfite. (a) Product. Potassium metabisulfite. (b) [Reserved] (c) Limitations...

21 CFR 582.3637 - Potassium metabisulfite.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Potassium metabisulfite. 582.3637 Section 582.3637 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL....3637 Potassium metabisulfite. (a) Product. Potassium metabisulfite. (b) [Reserved] (c) Limitations...

21 CFR 182.3616 - Potassium bisulfite.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Potassium bisulfite. 182.3616 Section 182.3616...) SUBSTANCES GENERALLY RECOGNIZED AS SAFE Chemical Preservatives § 182.3616 Potassium bisulfite. (a) Product. Potassium bisulfite. (b) [Reserved] (c) Limitations, restrictions, or explanation. This substance is...

21 CFR 182.3637 - Potassium metabisulfite.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Potassium metabisulfite. 182.3637 Section 182.3637 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD....3637 Potassium metabisulfite. (a) Product. Potassium metabisulfite. (b) [Reserved] (c) Limitations...

21 CFR 582.3616 - Potassium bisulfite.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Potassium bisulfite. 582.3616 Section 582.3616 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL....3616 Potassium bisulfite. (a) Product. Potassium bisulfite. (b) [Reserved] (c) Limitations...

21 CFR 582.3616 - Potassium bisulfite.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Potassium bisulfite. 582.3616 Section 582.3616 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL....3616 Potassium bisulfite. (a) Product. Potassium bisulfite. (b) [Reserved] (c) Limitations...

Systematic review and meta-analysis of randomised controlled trials on the effects of potassium supplements on serum potassium and creatinine.

PubMed

Cappuccio, Francesco P; Buchanan, Laura A; Ji, Chen; Siani, Alfonso; Miller, Michelle A

2016-08-26

High potassium intake could prevent stroke, but supplementation is considered hazardous. We assessed the effect of oral potassium supplementation on serum or plasma potassium levels and renal function. We updated a systematic review of the effects of potassium supplementation in randomised clinical trials carried out worldwide, published in 2013, extending it to July 2015. We followed the PRISMA guidelines. Any individual taking part in a potassium supplementation randomised clinical trial. Studies included met the following criteria: randomised clinical trials, potassium supplement given and circulating potassium levels reported. Oral potassium supplementation. Serum or plasma potassium and serum or plasma creatinine. A total of 20 trials (21 independent groups) were included (1216 participants from 12 different countries). All but 2 were controlled (placebo n=16, control n=2). Of these trials, 15 were crossover, 4 had a parallel group and 1 was sequential. The duration of supplementation varied from 2 to 24 weeks and the amount of potassium given from 22 to 140 mmol/day. In the pooled analysis, potassium supplementation caused a small but significant increase in circulating potassium levels (weighted mean difference (WMD) 0.14 mmol/L, 95% CI 0.09 to 0.19, p<1×10(-5)), not associated with dose or duration of treatment. The average increase in urinary potassium excretion was 45.75 mmol/24 hours, 95% CI 38.81 to 53.69, p<1×10(-5). Potassium supplementation did not cause any change in circulating creatinine levels (WMD 0.30 µmol/L, 95% CI -1.19 to 1.78, p=0.70). In short-term studies of relatively healthy persons, a moderate oral potassium supplement resulted in a small increase in circulating potassium levels and no change in renal function. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Detecting long tandem duplications in genomic sequences.

PubMed

Audemard, Eric; Schiex, Thomas; Faraut, Thomas

2012-05-08

Detecting duplication segments within completely sequenced genomes provides valuable information to address genome evolution and in particular the important question of the emergence of novel functions. The usual approach to gene duplication detection, based on all-pairs protein gene comparisons, provides only a restricted view of duplication. In this paper, we introduce ReD Tandem, a software using a flow based chaining algorithm targeted at detecting tandem duplication arrays of moderate to longer length regions, with possibly locally weak similarities, directly at the DNA level. On the A. thaliana genome, using a reference set of tandem duplicated genes built using TAIR,(a) we show that ReD Tandem is able to predict a large fraction of recently duplicated genes (dS  <  1) and that it is also able to predict tandem duplications involving non coding elements such as pseudo-genes or RNA genes. ReD Tandem allows to identify large tandem duplications without any annotation, leading to agnostic identification of tandem duplications. This approach nicely complements the usual protein gene based which ignores duplications involving non coding regions. It is however inherently restricted to relatively recent duplications. By recovering otherwise ignored events, ReD Tandem gives a more comprehensive view of existing evolutionary processes and may also allow to improve existing annotations.

Laboratory characterization of shale pores

NASA Astrophysics Data System (ADS)

Nur Listiyowati, Lina

2018-02-01

To estimate the potential of shale gas reservoir, one needs to understand the characteristics of pore structures. Characterization of shale gas reservoir microstructure is still a challenge due to ultra-fine grained micro-fabric and micro level heterogeneity of these sedimentary rocks. The sample used in the analysis is a small portion of any reservoir. Thus, each measurement technique has a different result. It raises the question which methods are suitable for characterizing pore shale. The goal of this paper is to summarize some of the microstructure analysis tools of shale rock to get near-real results. The two analyzing pore structure methods are indirect measurement (MIP, He, NMR, LTNA) and direct observation (SEM, TEM, Xray CT). Shale rocks have a high heterogeneity; thus, it needs multiscale quantification techniques to understand their pore structures. To describe the complex pore system of shale, several measurement techniques are needed to characterize the surface area and pore size distribution (LTNA, MIP), shapes, size and distribution of pore (FIB-SEM, TEM, Xray CT), and total porosity (He pycnometer, NMR). The choice of techniques and methods should take into account the purpose of the analysis and also the time and budget.

Potassium Intake, Bioavailability, Hypertension, and Glucose Control

PubMed Central

Stone, Michael S.; Martyn, Lisa; Weaver, Connie M.

2016-01-01

Potassium is an essential nutrient. It is the most abundant cation in intracellular fluid where it plays a key role in maintaining cell function. The gradient of potassium across the cell membrane determines cellular membrane potential, which is maintained in large part by the ubiquitous ion channel the sodium-potassium (Na+-K+) ATPase pump. Approximately 90% of potassium consumed (60–100 mEq) is lost in the urine, with the other 10% excreted in the stool, and a very small amount lost in sweat. Little is known about the bioavailability of potassium, especially from dietary sources. Less is understood on how bioavailability may affect health outcomes. Hypertension (HTN) is the leading cause of cardiovascular disease (CVD) and a major financial burden ($50.6 billion) to the US public health system, and has a significant impact on all-cause morbidity and mortality worldwide. The relationship between increased potassium supplementation and a decrease in HTN is relatively well understood, but the effect of increased potassium intake from dietary sources on blood pressure overall is less clear. In addition, treatment options for hypertensive individuals (e.g., thiazide diuretics) may further compound chronic disease risk via impairments in potassium utilization and glucose control. Understanding potassium bioavailability from various sources may help to reveal how specific compounds and tissues influence potassium movement, and further the understanding of its role in health. PMID:27455317

Potassium Intake, Bioavailability, Hypertension, and Glucose Control.

PubMed

Stone, Michael S; Martyn, Lisa; Weaver, Connie M

2016-07-22

Potassium is an essential nutrient. It is the most abundant cation in intracellular fluid where it plays a key role in maintaining cell function. The gradient of potassium across the cell membrane determines cellular membrane potential, which is maintained in large part by the ubiquitous ion channel the sodium-potassium (Na+-K+) ATPase pump. Approximately 90% of potassium consumed (60-100 mEq) is lost in the urine, with the other 10% excreted in the stool, and a very small amount lost in sweat. Little is known about the bioavailability of potassium, especially from dietary sources. Less is understood on how bioavailability may affect health outcomes. Hypertension (HTN) is the leading cause of cardiovascular disease (CVD) and a major financial burden ($50.6 billion) to the US public health system, and has a significant impact on all-cause morbidity and mortality worldwide. The relationship between increased potassium supplementation and a decrease in HTN is relatively well understood, but the effect of increased potassium intake from dietary sources on blood pressure overall is less clear. In addition, treatment options for hypertensive individuals (e.g., thiazide diuretics) may further compound chronic disease risk via impairments in potassium utilization and glucose control. Understanding potassium bioavailability from various sources may help to reveal how specific compounds and tissues influence potassium movement, and further the understanding of its role in health.

Non-equivalent role of TM2 gating hinges in heteromeric Kir4.1/Kir5.1 potassium channels.

PubMed

Shang, Lijun; Tucker, Stephen J

2008-02-01

Comparison of the crystal structures of the KcsA and MthK potassium channels suggests that the process of opening a K(+) channel involves pivoted bending of the inner pore-lining helices at a highly conserved glycine residue. This bending motion is proposed to splay the transmembrane domains outwards to widen the gate at the "helix-bundle crossing". However, in the inwardly rectifying (Kir) potassium channel family, the role of this "hinge" residue in the second transmembrane domain (TM2) and that of another putative glycine gating hinge at the base of TM2 remain controversial. We investigated the role of these two positions in heteromeric Kir4.1/Kir5.1 channels, which are unique amongst Kir channels in that both subunits lack a conserved glycine at the upper hinge position. Contrary to the effect seen in other channels, increasing the potential flexibility of TM2 by glycine substitutions at the upper hinge position decreases channel opening. Furthermore, the contribution of the Kir4.1 subunit to this process is dominant compared to Kir5.1, demonstrating a non-equivalent contribution of these two subunits to the gating process. A homology model of heteromeric Kir4.1/Kir5.1 shows that these upper "hinge" residues are in close contact with the base of the pore alpha-helix that supports the selectivity filter. Our results also indicate that the highly conserved glycine at the "lower" gating hinge position is required for tight packing of the TM2 helices at the helix-bundle crossing, rather than acting as a hinge residue.

21 CFR 182.3616 - Potassium bisulfite.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Potassium bisulfite. 182.3616 Section 182.3616 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Potassium bisulfite. (a) Product. Potassium bisulfite. (b) [Reserved] (c) Limitations, restrictions, or...

21 CFR 582.5628 - Potassium glycerophosphate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Potassium glycerophosphate. 582.5628 Section 582.5628 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Dietary Supplements 1 § 582.5628 Potassium glycerophosphate. (a) Product. Potassium glycerophosphate. (b...

21 CFR 582.5628 - Potassium glycerophosphate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Potassium glycerophosphate. 582.5628 Section 582.5628 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Dietary Supplements 1 § 582.5628 Potassium glycerophosphate. (a) Product. Potassium glycerophosphate. (b...

21 CFR 582.5628 - Potassium glycerophosphate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Potassium glycerophosphate. 582.5628 Section 582.5628 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Dietary Supplements 1 § 582.5628 Potassium glycerophosphate. (a) Product. Potassium glycerophosphate. (b...

21 CFR 582.5628 - Potassium glycerophosphate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Potassium glycerophosphate. 582.5628 Section 582.5628 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Dietary Supplements 1 § 582.5628 Potassium glycerophosphate. (a) Product. Potassium glycerophosphate. (b...

21 CFR 582.5628 - Potassium glycerophosphate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Potassium glycerophosphate. 582.5628 Section 582.5628 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Dietary Supplements 1 § 582.5628 Potassium glycerophosphate. (a) Product. Potassium glycerophosphate. (b...

21 CFR 862.1600 - Potassium test system.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Potassium test system. 862.1600 Section 862.1600....1600 Potassium test system. (a) Identification. A potassium test system is a device intended to measure potassium in serum, plasma, and urine. Measurements obtained by this device are used to monitor electrolyte...

21 CFR 862.1600 - Potassium test system.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Potassium test system. 862.1600 Section 862.1600....1600 Potassium test system. (a) Identification. A potassium test system is a device intended to measure potassium in serum, plasma, and urine. Measurements obtained by this device are used to monitor electrolyte...

21 CFR 862.1600 - Potassium test system.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Potassium test system. 862.1600 Section 862.1600....1600 Potassium test system. (a) Identification. A potassium test system is a device intended to measure potassium in serum, plasma, and urine. Measurements obtained by this device are used to monitor electrolyte...

21 CFR 862.1600 - Potassium test system.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Potassium test system. 862.1600 Section 862.1600....1600 Potassium test system. (a) Identification. A potassium test system is a device intended to measure potassium in serum, plasma, and urine. Measurements obtained by this device are used to monitor electrolyte...

21 CFR 862.1600 - Potassium test system.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Potassium test system. 862.1600 Section 862.1600....1600 Potassium test system. (a) Identification. A potassium test system is a device intended to measure potassium in serum, plasma, and urine. Measurements obtained by this device are used to monitor electrolyte...

INFRARED SPECTRUM OF POTASSIUM-CATIONIZED TRIETHYLPHOSPHATE GENERATED USING TANDEM MASS SPECTROMETRY AND INFRARED MULTIPLE PHOTON DISSOCIATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gary S. Groenewold; Christopher M. Leavitt; Ryan P. Dain

2009-09-01

Tandem mass spectrometry and wavelength selective infrared photodissociation was used to generate an infrared spectrum of gas-phase triethylphosphate cationized by attachment of K+. Prominent absorptions were observed in the region of 900 to 1300 cm-1 that are characteristic of phosphate P=O and P-O-R stretches. The relative positions and intensities of the IR absorptions were reproduced well by density functional theory (DFT) calculations performed using the B3LYP functional and the 6-31+g(d), 6-311+g(d,p) and 6-311++G(3df,2pd) basis sets. Because of good correspondence between experiment and theory for the cation, DFT was then used to generate a theoretical spectrum for neutral triethylphosphate, which inmore » turn accurately reproduces the IR spectrum of the neat liquid when solvent effects are included in the calculations.« less

21 CFR 582.1613 - Potassium bicarbonate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Potassium bicarbonate. 582.1613 Section 582.1613 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1613 Potassium bicarbonate. (a) Product. Potassium bicarbonate. (b) Conditions of use. This...

21 CFR 582.7610 - Potassium alginate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Potassium alginate. 582.7610 Section 582.7610 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Potassium alginate. (a) Product. Potassium alginate. (b) Conditions of use. This substance is generally...

21 CFR 582.1619 - Potassium carbonate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Potassium carbonate. 582.1619 Section 582.1619 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1619 Potassium carbonate. (a) Product. Potassium carbonate. (b) Conditions of use. This...

21 CFR 582.1643 - Potassium sulfate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Potassium sulfate. 582.1643 Section 582.1643 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1643 Potassium sulfate. (a) Product. Potassium sulfate. (b) Conditions of use. This...

21 CFR 582.6625 - Potassium citrate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Potassium citrate. 582.6625 Section 582.6625 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Potassium citrate. (a) Product. Potassium citrate. (b) Conditions of use. This substance is generally...

21 CFR 582.3640 - Potassium sorbate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Potassium sorbate. 582.3640 Section 582.3640 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL....3640 Potassium sorbate. (a) Product. Potassium sorbate. (b) Conditions of use. This substance is...

21 CFR 582.1619 - Potassium carbonate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Potassium carbonate. 582.1619 Section 582.1619 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1619 Potassium carbonate. (a) Product. Potassium carbonate. (b) Conditions of use. This...

21 CFR 182.3640 - Potassium sorbate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Potassium sorbate. 182.3640 Section 182.3640 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Potassium sorbate. (a) Product. Potassium sorbate. (b) Conditions of use. This substance is generally...

21 CFR 582.3640 - Potassium sorbate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Potassium sorbate. 582.3640 Section 582.3640 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL....3640 Potassium sorbate. (a) Product. Potassium sorbate. (b) Conditions of use. This substance is...

21 CFR 582.1631 - Potassium hydroxide.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Potassium hydroxide. 582.1631 Section 582.1631 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1631 Potassium hydroxide. (a) Product. Potassium hydroxide. (b) Conditions of use. This...

21 CFR 582.1631 - Potassium hydroxide.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Potassium hydroxide. 582.1631 Section 582.1631 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1631 Potassium hydroxide. (a) Product. Potassium hydroxide. (b) Conditions of use. This...

21 CFR 582.1619 - Potassium carbonate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Potassium carbonate. 582.1619 Section 582.1619 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1619 Potassium carbonate. (a) Product. Potassium carbonate. (b) Conditions of use. This...

21 CFR 582.1619 - Potassium carbonate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Potassium carbonate. 582.1619 Section 582.1619 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1619 Potassium carbonate. (a) Product. Potassium carbonate. (b) Conditions of use. This...

21 CFR 582.1631 - Potassium hydroxide.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Potassium hydroxide. 582.1631 Section 582.1631 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1631 Potassium hydroxide. (a) Product. Potassium hydroxide. (b) Conditions of use. This...

21 CFR 582.3640 - Potassium sorbate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Potassium sorbate. 582.3640 Section 582.3640 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL....3640 Potassium sorbate. (a) Product. Potassium sorbate. (b) Conditions of use. This substance is...

21 CFR 582.1625 - Potassium citrate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Potassium citrate. 582.1625 Section 582.1625 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1625 Potassium citrate. (a) Product. Potassium citrate. (b) Conditions of use. This...

21 CFR 582.1613 - Potassium bicarbonate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Potassium bicarbonate. 582.1613 Section 582.1613 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1613 Potassium bicarbonate. (a) Product. Potassium bicarbonate. (b) Conditions of use. This...

21 CFR 582.1613 - Potassium bicarbonate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Potassium bicarbonate. 582.1613 Section 582.1613 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1613 Potassium bicarbonate. (a) Product. Potassium bicarbonate. (b) Conditions of use. This...

21 CFR 182.3640 - Potassium sorbate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Potassium sorbate. 182.3640 Section 182.3640 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Potassium sorbate. (a) Product. Potassium sorbate. (b) Conditions of use. This substance is generally...

21 CFR 582.1625 - Potassium citrate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Potassium citrate. 582.1625 Section 582.1625 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1625 Potassium citrate. (a) Product. Potassium citrate. (b) Conditions of use. This...

21 CFR 182.3640 - Potassium sorbate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Potassium sorbate. 182.3640 Section 182.3640 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Potassium sorbate. (a) Product. Potassium sorbate. (b) Conditions of use. This substance is generally...

21 CFR 582.1613 - Potassium bicarbonate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Potassium bicarbonate. 582.1613 Section 582.1613 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1613 Potassium bicarbonate. (a) Product. Potassium bicarbonate. (b) Conditions of use. This...

21 CFR 582.1625 - Potassium citrate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Potassium citrate. 582.1625 Section 582.1625 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1625 Potassium citrate. (a) Product. Potassium citrate. (b) Conditions of use. This...

21 CFR 582.7610 - Potassium alginate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Potassium alginate. 582.7610 Section 582.7610 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Potassium alginate. (a) Product. Potassium alginate. (b) Conditions of use. This substance is generally...

21 CFR 582.1643 - Potassium sulfate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Potassium sulfate. 582.1643 Section 582.1643 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1643 Potassium sulfate. (a) Product. Potassium sulfate. (b) Conditions of use. This...

21 CFR 582.1625 - Potassium citrate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Potassium citrate. 582.1625 Section 582.1625 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1625 Potassium citrate. (a) Product. Potassium citrate. (b) Conditions of use. This...

21 CFR 182.3640 - Potassium sorbate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Potassium sorbate. 182.3640 Section 182.3640 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Potassium sorbate. (a) Product. Potassium sorbate. (b) Conditions of use. This substance is generally...

21 CFR 582.6625 - Potassium citrate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Potassium citrate. 582.6625 Section 582.6625 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Potassium citrate. (a) Product. Potassium citrate. (b) Conditions of use. This substance is generally...

21 CFR 582.6625 - Potassium citrate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Potassium citrate. 582.6625 Section 582.6625 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Potassium citrate. (a) Product. Potassium citrate. (b) Conditions of use. This substance is generally...

21 CFR 582.1631 - Potassium hydroxide.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Potassium hydroxide. 582.1631 Section 582.1631 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1631 Potassium hydroxide. (a) Product. Potassium hydroxide. (b) Conditions of use. This...

21 CFR 582.1631 - Potassium hydroxide.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Potassium hydroxide. 582.1631 Section 582.1631 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1631 Potassium hydroxide. (a) Product. Potassium hydroxide. (b) Conditions of use. This...

21 CFR 582.6625 - Potassium citrate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Potassium citrate. 582.6625 Section 582.6625 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Potassium citrate. (a) Product. Potassium citrate. (b) Conditions of use. This substance is generally...

21 CFR 582.1643 - Potassium sulfate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Potassium sulfate. 582.1643 Section 582.1643 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1643 Potassium sulfate. (a) Product. Potassium sulfate. (b) Conditions of use. This...

21 CFR 582.3640 - Potassium sorbate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Potassium sorbate. 582.3640 Section 582.3640 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL....3640 Potassium sorbate. (a) Product. Potassium sorbate. (b) Conditions of use. This substance is...

21 CFR 182.3640 - Potassium sorbate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Potassium sorbate. 182.3640 Section 182.3640 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) SUBSTANCES GENERALLY RECOGNIZED AS SAFE Chemical Preservatives § 182.3640 Potassium sorbate. (a) Product. Potassium...

21 CFR 582.1613 - Potassium bicarbonate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Potassium bicarbonate. 582.1613 Section 582.1613 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1613 Potassium bicarbonate. (a) Product. Potassium bicarbonate. (b) Conditions of use. This...

21 CFR 582.1625 - Potassium citrate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Potassium citrate. 582.1625 Section 582.1625 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1625 Potassium citrate. (a) Product. Potassium citrate. (b) Conditions of use. This...

21 CFR 582.1619 - Potassium carbonate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Potassium carbonate. 582.1619 Section 582.1619 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1619 Potassium carbonate. (a) Product. Potassium carbonate. (b) Conditions of use. This...

21 CFR 582.6625 - Potassium citrate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Potassium citrate. 582.6625 Section 582.6625 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Potassium citrate. (a) Product. Potassium citrate. (b) Conditions of use. This substance is generally...

21 CFR 582.7610 - Potassium alginate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Potassium alginate. 582.7610 Section 582.7610 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Potassium alginate. (a) Product. Potassium alginate. (b) Conditions of use. This substance is generally...

21 CFR 582.3640 - Potassium sorbate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Potassium sorbate. 582.3640 Section 582.3640 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL....3640 Potassium sorbate. (a) Product. Potassium sorbate. (b) Conditions of use. This substance is...

21 CFR 582.1643 - Potassium sulfate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Potassium sulfate. 582.1643 Section 582.1643 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1643 Potassium sulfate. (a) Product. Potassium sulfate. (b) Conditions of use. This...

21 CFR 582.1643 - Potassium sulfate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Potassium sulfate. 582.1643 Section 582.1643 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1643 Potassium sulfate. (a) Product. Potassium sulfate. (b) Conditions of use. This...

Potassium in hypertension and cardiovascular disease.

PubMed

Castro, Hector; Raij, Leopoldo

2013-05-01

The increased prevalence of hypertension and cardiovascular disease in industrialized societies undoubtedly is associated with the modern high-sodium/low-potassium diet. Extensive experimental and clinical data strongly link potassium intake to cardiovascular outcome. Most studies suggest that the sodium-to-potassium intake ratio is a better predictor of cardiovascular outcome than either nutrient individually. A high-sodium/low-potassium environment results in significant abnormalities in central hemodynamics, leading to potential target organ damage. Altered renal sodium handling, impaired endothelium-dependent vasodilatation, and increased oxidative stress are important mediators of this effect. It remains of paramount importance to reinforce consumption of a low-sodium/high-potassium diet as a critical strategy for prevention and treatment of hypertension and cardiovascular disease. Published by Elsevier Inc.

Estimating Sodium and Potassium Intakes and Their Ratio in the American Diet: Data from the 2011–2012 NHANES1234

PubMed Central

Bailey, Regan L; Parker, Elizabeth A; Rhodes, Donna G; Goldman, Joseph D; Clemens, John C; Moshfegh, Alanna J; Thuppal, Sowmyanarayanan V; Weaver, Connie M

2016-01-01

Background: The dietary sodium-to-potassium ratio (Na:K) is shown to be more strongly associated with an increased risk of cardiovascular disease (CVD) and CVD-related mortality than either sodium or potassium intake alone. Objective: The aim was to estimate the Na:K in the diet of US adults. Methods: Among US adults from the 2011–2012 NHANES (≥20 y; 2393 men and 2337 women), the National Cancer Institute method was used to estimate sodium and potassium intakes, Na:K, and the percentage of individuals with Na:K <1.0 utilizing the complex, stratified, multistage probability cluster sampling design. Results: Overall, women had a significantly lower Na:K than men (mean ± SE: 1.32 ± 0.02 compared with 1.45 ± 0.02). Non-Hispanic whites had a significantly lower Na:K than non-Hispanic blacks and non-Hispanic Asians (1.34 ± 0.02 compared with 1.54 ± 0.03 and 1.49 ± 0.04, respectively). Only 12.2% ± 1.5% of US adults had a Na:K < 1.0. The Na:K decreased linearly as age increased. Most adults (90% ± 0.8%) had sodium intakes >2300 mg/d, whereas <3% had potassium intakes >4700 mg/d. Grains and vegetables were among the highest contributors to sodium intakes for adults with Na:K < 1.0, compared with protein foods and grains for those with Na:K ≥ 1.0. Vegetables and milk and dairy products constituted the primary dietary sources of potassium for individuals with Na:K < 1.0, whereas mixed dishes and protein foods contributed the most potassium for individuals with ratios ≥1.0. Individuals with a Na:K < 1.0 were less likely to consume mixed dishes and condiments and were more likely to consume vegetables, milk and dairy products, and fruit than those with a Na:K ≥ 1.0. Conclusion: Only about one-tenth of US adults have a Na:K consistent with the WHO guidelines for reduced risk of mortality. Continued efforts to reduce sodium intake in tandem with novel strategies to increase potassium intake are warranted. PMID:26962185

21 CFR 582.5634 - Potassium iodide.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Potassium iodide. 582.5634 Section 582.5634 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Supplements 1 § 582.5634 Potassium iodide. (a) Product. Potassium iodide. (b) Tolerance. 0.01 percent. (c...

21 CFR 172.730 - Potassium bromate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Potassium bromate. 172.730 Section 172.730 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Other Specific Usage Additives § 172.730 Potassium bromate. The food additive potassium bromate may be...

21 CFR 172.160 - Potassium nitrate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Potassium nitrate. 172.160 Section 172.160 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Food Preservatives § 172.160 Potassium nitrate. The food additive potassium nitrate may be safely used...

21 CFR 582.5634 - Potassium iodide.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Potassium iodide. 582.5634 Section 582.5634 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Supplements 1 § 582.5634 Potassium iodide. (a) Product. Potassium iodide. (b) Tolerance. 0.01 percent. (c...

21 CFR 172.160 - Potassium nitrate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Potassium nitrate. 172.160 Section 172.160 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Food Preservatives § 172.160 Potassium nitrate. The food additive potassium nitrate may be safely used...

21 CFR 172.160 - Potassium nitrate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Potassium nitrate. 172.160 Section 172.160 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Food Preservatives § 172.160 Potassium nitrate. The food additive potassium nitrate may be safely used...

High Temperature Stability of Potassium Beta Alumina

NASA Technical Reports Server (NTRS)

Williams, R. M.; Kisor, A.; Ryan, M. A.

1996-01-01

None. From Objectives section: Evaluate the stability of potassium beta alumina under potassium AMTEC operating conditions. Evaluate the stability regime in which potassium beta alumina can be fabricated.

21 CFR 201.72 - Potassium labeling.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 4 2013-04-01 2013-04-01 false Potassium labeling. 201.72 Section 201.72 Food and... LABELING Labeling Requirements for Over-the-Counter Drugs § 201.72 Potassium labeling. (a) The labeling of over-the-counter (OTC) drug products intended for oral ingestion shall contain the potassium content...

21 CFR 201.72 - Potassium labeling.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 4 2014-04-01 2014-04-01 false Potassium labeling. 201.72 Section 201.72 Food and... LABELING Labeling Requirements for Over-the-Counter Drugs § 201.72 Potassium labeling. (a) The labeling of over-the-counter (OTC) drug products intended for oral ingestion shall contain the potassium content...

21 CFR 201.72 - Potassium labeling.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 4 2012-04-01 2012-04-01 false Potassium labeling. 201.72 Section 201.72 Food and... LABELING Labeling Requirements for Over-the-Counter Drugs § 201.72 Potassium labeling. (a) The labeling of over-the-counter (OTC) drug products intended for oral ingestion shall contain the potassium content...

Agreement of arterial sodium and arterial potassium levels with venous sodium and venous potassium in patients admitted to intensive care unit.

PubMed

Nanda, Sunil Kumar; Ray, Lopamudra; Dinakaran, Asha

2015-02-01

Electrolyte abnormalities are one of the common causes of morbidity and mortality in critically ill patients. The turnaround time for electrolyte reporting should be as low as possible. Electrolytes are measured conventionally in serum obtained from venous blood by electrolyte analyser which takes 20 to 30 min. Point of care analysers are now available where in electrolytes can be measured in arterial blood within 5 min. This study was done to study the agreement of arterial sodium and arterial potassium with venous sodium and venous potassium levels. Venous sodium and venous potassium levels and arterial sodium and arterial potassium levels were analysed on 206 patient samples admitted to Intensive Care Unit (ICU). The venous values were compared with the arterial values for correlation. Venous sodium was compared with arterial sodium by spearman correlation. Venous potassium was compared with arterial potassium by pearson correlation. The mean value of arterial sodium was 134 and venous sodium was 137. The mean value of arterial potassium was 3.6 and venous potassium was 4.1. The correlation coefficient obtained for sodium was 0.787 and correlation coefficient obtained for potassium was 0.701. There was positive correlation of arterial sodium and arterial potassium with venous sodium and venous potassium indicating agreement between the parameters. Arterial sodium and arterial potassium can be used instead of venous sodium and venous potassium levels in management of critically ill patients.

21 CFR 184.1077 - Potassium acid tartrate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Potassium acid tartrate. 184.1077 Section 184.1077... Listing of Specific Substances Affirmed as GRAS § 184.1077 Potassium acid tartrate. (a) Potassium acid tartrate (C4H5KO6, CAS Reg. No. 868-14-4) is the potassium acid salt of l−(+)−tartaric acid and is also...

21 CFR 184.1077 - Potassium acid tartrate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Potassium acid tartrate. 184.1077 Section 184.1077... Listing of Specific Substances Affirmed as GRAS § 184.1077 Potassium acid tartrate. (a) Potassium acid tartrate (C4H5KO6, CAS Reg. No. 868-14-4) is the potassium acid salt of l−(+)−tartaric acid and is also...

Recipe for potassium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Izutani, Natsuko

2012-11-12

I investigate favorable conditions for producing potassium (K). Observations show [K/Fe] > 0 at low metallicities, while zero-metal supernova models show low [K/Fe] (< 0). Theoretically, it is natural that the odd-Z element, potassium decreases with lower metallicity, and thus, the observation should imply new and unknown sites for potassium. In this proceedings, I calculate proton-rich nucleosynthesis with three parameters, the initial Y{sub e} (from 0.51 to 0.60), the initial density {rho}{sub max} (10{sup 7}, 10{sup 8}, and 10{sup 9} [g/cm{sup 3}]), and the e-fold time {tau} for the density (0.01, 0.1, and 1.0 [sec]). Among 90 models I havemore » calculated, only 26 models show [K/Fe] > 0, and they all have {rho}{sub max} = 10{sup 9}[g/cm{sup 3}]. I discuss parameter dependence of [K/Fe].« less

Web interface for Brownian dynamics simulation of ion transport and its applications to beta-barrel pores.

PubMed

Lee, Kyu Il; Jo, Sunhwan; Rui, Huan; Egwolf, Bernhard; Roux, Benoît; Pastor, Richard W; Im, Wonpil

2012-01-30

Brownian dynamics (BD) based on accurate potential of mean force is an efficient and accurate method for simulating ion transport through wide ion channels. Here, a web-based graphical user interface (GUI) is presented for carrying out grand canonical Monte Carlo (GCMC) BD simulations of channel proteins: http://www.charmm-gui.org/input/gcmcbd. The webserver is designed to help users avoid most of the technical difficulties and issues encountered in setting up and simulating complex pore systems. GCMC/BD simulation results for three proteins, the voltage dependent anion channel (VDAC), α-Hemolysin (α-HL), and the protective antigen pore of the anthrax toxin (PA), are presented to illustrate the system setup, input preparation, and typical output (conductance, ion density profile, ion selectivity, and ion asymmetry). Two models for the input diffusion constants for potassium and chloride ions in the pore are compared: scaling of the bulk diffusion constants by 0.5, as deduced from previous all-atom molecular dynamics simulations of VDAC, and a hydrodynamics based model (HD) of diffusion through a tube. The HD model yields excellent agreement with experimental conductances for VDAC and α-HL, while scaling bulk diffusion constants by 0.5 leads to underestimates of 10-20%. For PA, simulated ion conduction values overestimate experimental values by a factor of 1.5-7 (depending on His protonation state and the transmembrane potential), implying that the currently available computational model of this protein requires further structural refinement. Copyright © 2011 Wiley Periodicals, Inc.

Web Interface for Brownian Dynamics Simulation of Ion Transport and Its Applications to Beta-Barrel Pores

PubMed Central

Lee, Kyu Il; Jo, Sunhwan; Rui, Huan; Egwolf, Bernhard; Roux, Benoît; Pastor, Richard W.; Im, Wonpil

2011-01-01

Brownian dynamics (BD) in a suitably constructed potential of mean force is an efficient and accurate method for simulating ion transport through wide ion channels. Here, a web-based graphical user interface (GUI) is presented for grand canonical Monte Carlo (GCMC) BD simulations of channel proteins: http://www.charmm-gui.org/input/gcmcbd. The webserver is designed to help users avoid most of the technical difficulties and issues encountered in setting up and simulating complex pore systems. GCMC/BD simulation results for three proteins, the voltage dependent anion channel (VDAC), α-Hemolysin, and the protective antigen pore of the anthrax toxin (PA), are presented to illustrate system setup, input preparation, and typical output (conductance, ion density profile, ion selectivity, and ion asymmetry). Two models for the input diffusion constants for potassium and chloride ions in the pore are compared: scaling of the bulk diffusion constants by 0.5, as deduced from previous all-atom molecular dynamics simulations of VDAC; and a hydrodynamics based model (HD) of diffusion through a tube. The HD model yields excellent agreement with experimental conductances for VDAC and α-Hemolysin, while scaling bulk diffusion constants by 0.5 leads to underestimates of 10–20%. For PA, simulated ion conduction values overestimate experimental values by a factor of 1.5 to 7 (depending on His protonation state and the transmembrane potential), implying that the currently available computational model of this protein requires further structural refinement. PMID:22102176

21 CFR 172.160 - Potassium nitrate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Potassium nitrate. 172.160 Section 172.160 Food... ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Food Preservatives § 172.160 Potassium nitrate. The food additive potassium nitrate may be safely used as a curing agent in the processing of cod...

21 CFR 172.160 - Potassium nitrate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Potassium nitrate. 172.160 Section 172.160 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Preservatives § 172.160 Potassium nitrate. The food additive potassium nitrate may be safely used as a curing...

21 CFR 184.1804 - Sodium potassium tartrate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Sodium potassium tartrate. 184.1804 Section 184... Listing of Specific Substances Affirmed as GRAS § 184.1804 Sodium potassium tartrate. (a) Sodium potassium tartrate (C4H4KNaO6·4H2O, CAS Reg. No. 304-59-6) is the sodium potassium salt of l−(+)−tartaric acid and is...

21 CFR 184.1804 - Sodium potassium tartrate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Sodium potassium tartrate. 184.1804 Section 184... as GRAS § 184.1804 Sodium potassium tartrate. (a) Sodium potassium tartrate (C4H4KNaO6·4H2O, CAS Reg. No. 304-59-6) is the sodium potassium salt of l−(+)−tartaric acid and is also called the Rochelle...

21 CFR 184.1804 - Sodium potassium tartrate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Sodium potassium tartrate. 184.1804 Section 184... Listing of Specific Substances Affirmed as GRAS § 184.1804 Sodium potassium tartrate. (a) Sodium potassium tartrate (C4H4KNaO6·4H2O, CAS Reg. No. 304-59-6) is the sodium potassium salt of l−(+)−tartaric acid and is...

21 CFR 184.1804 - Sodium potassium tartrate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Sodium potassium tartrate. 184.1804 Section 184... Listing of Specific Substances Affirmed as GRAS § 184.1804 Sodium potassium tartrate. (a) Sodium potassium tartrate (C4H4KNaO6·4H2O, CAS Reg. No. 304-59-6) is the sodium potassium salt of l−(+)−tartaric acid and is...

Potassium test

MedlinePlus

High levels of potassium ( hyperkalemia ) may be due to: Addison disease (rare) Blood transfusion Certain medicines Crushed tissue injury Hyperkalemic periodic paralysis Hypoaldosteronism (very rare) ...

Daily potassium intake and sodium-to-potassium ratio in the reduction of blood pressure: a meta-analysis of randomized controlled trials.

PubMed

Binia, Aristea; Jaeger, Jonathan; Hu, Youyou; Singh, Anurag; Zimmermann, Diane

2015-08-01

To evaluate the efficacy of daily potassium intake on decreasing blood pressure in non-medicated normotensive or hypertensive patients, and to determine the relationship between potassium intake, sodium-to-potassium ratio and reduction in blood pressure. Mixed-effect meta-analyses and meta-regression models. Medline and the references of previous meta-analyses. Randomized controlled trials with potassium supplementation, with blood pressure as the primary outcome, in non-medicated patients. Fifteen randomized controlled trials of potassium supplementation in patients without antihypertensive medication were selected for the meta-analyses (917 patients). Potassium supplementation resulted in reduction of SBP by 4.7 mmHg [95% confidence interval (CI) 2.4-7.0] and DBP by 3.5 mmHg (95% CI 1.3-5.7) in all patients. The effect was found to be greater in hypertensive patients, with a reduction of SBP by 6.8 mmHg (95% CI 4.3-9.3) and DBP by 4.6 mmHg (95% CI 1.8-7.5). Meta-regression analysis showed that both increased daily potassium excretion and decreased sodium-to-potassium ratio were associated with blood pressure reduction (P < 0.05). Increased total daily potassium urinary excretion from 60 to 100 mmol/day and decrease of sodium-to-potassium ratio were shown to be necessary to explain the estimated effect. Potassium supplementation is associated with reduction of blood pressure in patients who are not on antihypertensive medication, and the effect is significant in hypertensive patients. The reduction in blood pressure significantly correlates with decreased daily urinary sodium-to-potassium ratio and increased urinary potassium. Patients with elevated blood pressure may benefit from increased potassium intake along with controlled or decreased sodium intake.

[Determination of biurea in flour and its products by liquid chromatography-tandem mass spectrometry].

PubMed

Wang, Ya; Wang, Junsu; Xiang, Lu; Xi, Cunxian; Chen, Dongdong; Peng, Tao; Wang, Guomin; Mu, Zhaode

2014-05-01

A novel method was established for the determination and identification of biurea in flour and its products using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The biurea was extracted with water and oxidized to azodicarbonamide by potassium permanganate. The azodicarbonamide was then derivatized using sodium p-toluene sulfinate solution. The separation was performed on a Shimpak XR-ODS II column (150 mm x 2.0 mm, 2.2 microm) using the mobile phase composed of acetonitrile and 2 mmol/L ammonium acetate aqueous solution (containing 0.2% (v/v) formic acid) with a gradient elution program. Tandem mass spectrometric detection was performed in multiple reaction monitoring (MRM) scan mode with a positive electrospray ionization (ESI(+)) source. The method used stable isotope internal standard quantitation. The calibration curve showed good linearity over the range of 1-20 000 microg/kg (R2 = 0.999 9). The limit of quantification was 5 microg/kg for biurea spiked in flour and its products. At the spiking levels of 5.0, 10.0 and 50.0 microg/kg in different matrices, the average recovery o biurea was 78.3%-108.0% with the relative standard deviations (RSDs) < or = 5.73%. The method developed is novel, reliable and sensitive with wide linear range, and can be used to determine the biurea in flour and its products.

Altered Methylation in Tandem Repeat Element and Elemental Component Levels in Inhalable Air Particles

PubMed Central

Hou, Lifang; Zhang, Xiao; Zheng, Yinan; Wang, Sheng; Dou, Chang; Guo, Liqiong; Byun, Hyang-Min; Motta, Valeria; McCracken, John; Díaz, Anaité; Kang, Choong-Min; Koutrakis, Petros; Bertazzi, Pier Alberto; Li, Jingyun; Schwartz, Joel; Baccarelli, Andrea A.

2014-01-01

Exposure to particulate matter (PM) has been associated with lung cancer risk in epidemiology investigations. Elemental components of PM have been suggested to have critical roles in PM toxicity, but the molecular mechanisms underlying their association with cancer risks remain poorly understood. DNA methylation has emerged as a promising biomarker for environmental-related diseases, including lung cancer. In this study, we evaluated the effects of PM elemental components on methylation of three tandem repeats in a highly-exposed population in Beijing, China. The Beijing Truck Driver Air Pollution Study was conducted shortly before the 2008 Beijing Olympic Games (June 15-July 27, 2008) and included 60 truck drivers and 60 office workers. On two days separated by 1-2 weeks, we measured blood DNA methylation of SATα, NBL2, D4Z4, and personal exposure to eight elemental components in PM2.5, including aluminum (Al), silicon (Si), sulfur (S), potassium (K), calcium (Ca) titanium (Ti), iron (Fe), and zinc (Zn). We estimated the associations of individual elemental component with each tandem repeat methylation in generalized estimating equations (GEE) models adjusted for PM2.5 mass and other covariates. Out of the eight examined elements, NBL2 methylation was positively associated with concentrations of Si (0.121, 95%CI: 0.030; 0.212, FDR=0.047) and Ca (0.065, 95%CI: 0.014; 0.115, FDR=0.047) in truck drivers. In office workers, SATα methylation was positively associated with concentrations of S (0.115, 95%CI: 0.034; 0.196, FDR=0.042). PM-associated differences in blood tandem-repeat methylation may help detect biological effects of the exposure and identify individuals who may eventually experience higher lung cancer risk. PMID:24273195

NMR-based diffusion pore imaging.

PubMed

Laun, Frederik Bernd; Kuder, Tristan Anselm; Wetscherek, Andreas; Stieltjes, Bram; Semmler, Wolfhard

2012-08-01

Nuclear magnetic resonance (NMR) diffusion experiments offer a unique opportunity to study boundaries restricting the diffusion process. In a recent Letter [Phys. Rev. Lett. 107, 048102 (2011)], we introduced the idea and concept that such diffusion experiments can be interpreted as NMR imaging experiments. Consequently, images of closed pores, in which the spins diffuse, can be acquired. In the work presented here, an in-depth description of the diffusion pore imaging technique is provided. Image artifacts due to gradient profiles of finite duration, field inhomogeneities, and surface relaxation are considered. Gradients of finite duration lead to image blurring and edge enhancement artifacts. Field inhomogeneities have benign effects on diffusion pore images, and surface relaxation can lead to a shrinkage and shift of the pore image. The relation between boundary structure and the imaginary part of the diffusion weighted signal is analyzed, and it is shown that information on pore coherence can be obtained without the need to measure the phase of the diffusion weighted signal. Moreover, it is shown that quite arbitrary gradient profiles can be used for diffusion pore imaging. The matrices required for numerical calculations are stated and provided as supplemental material.

A statistical image analysis framework for pore-free islands derived from heterogeneity distribution of nuclear pore complexes.

PubMed

Mimura, Yasuhiro; Takemoto, Satoko; Tachibana, Taro; Ogawa, Yutaka; Nishimura, Masaomi; Yokota, Hideo; Imamoto, Naoko

2017-11-24

Nuclear pore complexes (NPCs) maintain cellular homeostasis by mediating nucleocytoplasmic transport. Although cyclin-dependent kinases (CDKs) regulate NPC assembly in interphase, the location of NPC assembly on the nuclear envelope is not clear. CDKs also regulate the disappearance of pore-free islands, which are nuclear envelope subdomains; this subdomain gradually disappears with increase in homogeneity of the NPC in response to CDK activity. However, a causal relationship between pore-free islands and NPC assembly remains unclear. Here, we elucidated mechanisms underlying NPC assembly from a new perspective by focusing on pore-free islands. We proposed a novel framework for image-based analysis to automatically determine the detailed 'landscape' of pore-free islands from a large quantity of images, leading to the identification of NPC intermediates that appear in pore-free islands with increased frequency in response to CDK activity. Comparison of the spatial distribution between simulated and the observed NPC intermediates within pore-free islands showed that their distribution was spatially biased. These results suggested that the disappearance of pore-free islands is highly related to de novo NPC assembly and indicated the existence of specific regulatory mechanisms for the spatial arrangement of NPC assembly on nuclear envelopes.

Investigating Hydrophilic Pores in Model Lipid Bilayers using Molecular Simulations: Correlating Bilayer Properties with Pore Formation Thermodynamics

PubMed Central

Hu, Yuan; Sinha, Sudipta Kumar

2015-01-01

Cell-penetrating and antimicrobial peptides show remarkable ability to translocate across physiological membranes. Along with factors such as electric potential induced-perturbations of membrane structure and surface tension effects, experiments invoke pore-like membrane configurations during the solute transfer process into vesicles and cells. The initiation and formation of pores are associated with a non-trivial free energy cost, thus necessitating consideration of the factors associated with pore formation and attendant free energetics. Due to experimental and modeling challenges related to the long timescales of the translocation process, we use umbrella-sampling molecular dynamics simulations with a lipid-density based order parameter to investigate membrane pore-formation free energy employing Martini coarse-grained models. We investigate structure and thermodynamic features of the pore in 18 lipids spanning a range of head-groups, charge states, acyl chain lengths and saturation. We probe the dependence of pore-formation barriers on area per lipid, lipid bilayer thickness, membrane bending rigidities in three different lipid classes. The pore formation free energy in pure bilayers and peptide translocating scenarios are significantly coupled with bilayer thickness. Thicker bilayers require more reversible work to create pores. Pore formation free energy is higher in peptide-lipid systems relative to the peptide-free lipid systems due to penalties to maintain solvation of charged hydrophilic solutes within the membrane environment. PMID:25614183

Potassium-doped n-type bilayer graphene

NASA Astrophysics Data System (ADS)

Yamada, Takatoshi; Okigawa, Yuki; Hasegawa, Masataka

2018-01-01

Potassium-doped n-type bilayer graphene was obtained. Chemical vapor deposited bilayer and single layer graphene on copper (Cu) foils were used. After etching of Cu foils, graphene was dipped in potassium hydroxide aqueous solutions to dope potassium. Graphene on silicon oxide was characterized by X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), and Raman spectroscopy. Both XPS and EDX spectra indicated potassium incorporation into the bilayer graphene via intercalation between the graphene sheets. The downward shift of the 2D peak position of bilayer graphene after the potassium hydroxide (KOH) treatment was confirmed in Raman spectra, indicating that the KOH-treated bilayer graphene was doped with electrons. Electrical properties were measured using Hall bar structures. The Dirac points of bilayer graphene were shifted from positive to negative by the KOH treatment, indicating that the KOH-treated bilayer graphene was n-type conduction. For single layer graphene after the KOH treatment, although electron doping was confirmed from Raman spectra, the peak of potassium in the X-ray photoelectron spectroscopy (XPS) spectrum was not detected. The Dirac points of single layer graphene with and without the KOH treatment showed positive.

Drug-induced abnormalities of potassium metabolism.

PubMed

Kokot, Franciszek; Hyla-Klekot, Lidia

2008-01-01

Pharmacotherapy has progressed rapidly over the last 20 years with the result that general practioners more and more often use drugs which may influence potassium metabolism at the kidney or gastrointestinal level, or the transmembrane transport of potassium at the cellular level. Potassium abnormalities may result in life-theatening clinical conditions. Hypokalemia is most frequently caused by renal loss of this electrolyte (thiazide, thiazide-like and loop diuretics, glucocorticoids) and the gastrointestinal tract (laxatives, diarrhea, vomiting, external fistula), and may be the result of an increased intracellular potassium influx induced by sympathicomimetics used mostly by patients with asthma, or by insulin overdosage in diabetic subjects. The leading symptoms of hypokalemia are skeletal and smooth muscle weakness and cardiac arrhythmias. Hyperkalemia may be caused by acute or end-stage renal failure, impaired tubular excretion of potassium (blockers of the renin-angiotensin-aldosterone system, nonsteroidal anti-inflammatory drugs, cyclosporine, antifungal drugs, potassium sparing diuretics), acidemia, and severe cellular injury (tumor lysis syndrome). Hyperkalemia may be the cause of severe injury of both skeletal and smooth muscle cells. The specific treatment counteracting hyperkalemia is a bolus injection of calcium salts and, when necessary, hemodialysis.

Race, Serum Potassium, and Associations With ESRD and Mortality.

PubMed

Chen, Yan; Sang, Yingying; Ballew, Shoshana H; Tin, Adrienne; Chang, Alex R; Matsushita, Kunihiro; Coresh, Josef; Kalantar-Zadeh, Kamyar; Molnar, Miklos Z; Grams, Morgan E

2017-08-01

Recent studies suggest that potassium levels may differ by race. The basis for these differences and whether associations between potassium levels and adverse outcomes differ by race are unknown. Observational study. Associations between race and potassium level and the interaction of race and potassium level with outcomes were investigated in the Racial and Cardiovascular Risk Anomalies in Chronic Kidney Disease (RCAV) Study, a cohort of US veterans (N=2,662,462). Associations between African ancestry and potassium level were investigated in African Americans in the Atherosclerosis Risk in Communities (ARIC) Study (N=3,450). Race (African American vs non-African American and percent African ancestry) for cross-sectional analysis; serum potassium level for longitudinal analysis. Potassium level for cross-sectional analysis; mortality and end-stage renal disease for longitudinal analysis. The RCAV cohort was 18% African American (N=470,985). Potassium levels on average were 0.162mmol/L lower in African Americans compared with non-African Americans, with differences persisting after adjustment for demographics, comorbid conditions, and potassium-altering medication use. In the ARIC Study, higher African ancestry was related to lower potassium levels (-0.027mmol/L per each 10% African ancestry). In both race groups, higher and lower potassium levels were associated with mortality. Compared to potassium level of 4.2mmol/L, mortality risk associated with lower potassium levels was lower in African Americans versus non-African Americans, whereas mortality risk associated with higher levels was slightly greater. Risk relationships between potassium and end-stage renal disease were weaker, with no difference by race. No data for potassium intake. African Americans had slightly lower serum potassium levels than non-African Americans. Consistent associations between potassium levels and percent African ancestry may suggest a genetic component to these differences. Higher and

Freezing and melting of water in a single cylindrical pore: The pore-size dependence of freezing and melting behavior

NASA Astrophysics Data System (ADS)

Morishige, Kunimitsu; Kawano, Keiji

1999-03-01

In order to clarify the origin of the hysteresis between freezing and melting of pore water, we performed x-ray diffraction measurements of water confined inside the cylindrical pores of seven kinds of siliceous MCM-41 (a member of ordered mesoporous materials denoted by Mobil Oil researchers) with different pore radii (1.2-2.9 nm) and the interconnected pores of Vycor glass as a function of temperature. The hysteresis effect depends markedly on the size of the cylindrical pores: the hysteresis is negligibly small in smaller pores and becomes remarkable in larger pores. This strongly suggests that the hysteresis is arisen from size-dependent supercooling of water confined to the mesopores. For the water confined to the mesopores with pore radius of 1.2 nm, a continuous transition between a liquid and a solid precedes the first-order freezing transition of the pore water which would occur by the same mechanism as in bulk water.

Short Tandem Repeat DNA Internet Database

National Institute of Standards and Technology Data Gateway

SRD 130 Short Tandem Repeat DNA Internet Database (Web, free access)   Short Tandem Repeat DNA Internet Database is intended to benefit research and application of short tandem repeat DNA markers for human identity testing. Facts and sequence information on each STR system, population data, commonly used multiplex STR systems, PCR primers and conditions, and a review of various technologies for analysis of STR alleles have been included.

Equatorial potassium currents in lenses.

PubMed

Wind, B E; Walsh, S; Patterson, J W

1988-02-01

Earlier work with the vibrating probe demonstrated the existence of outward potassium currents at the equator and inward sodium currents at the optical poles of the lens. By adding microelectrodes to the system, it is possible to relate steady currents (J) to the potential difference (PD) measured with a microelectrode. By injecting an outward current (I), it is possible to determine resistances and also the PD at which the steady outward potassium current becomes zero (PDJ = 0). At this PD the concentration gradient for potassium efflux and the electrical gradient for potassium influx are balanced so that there is no net flow of potassium across the membranes associated with the production of J. The PDJ = 0 for 18 rat lenses was 86 mV and that for 12 frogs lenses was -95 mV. This agrees with the potassium equilibrium potential and provides strong evidence to support the view that the outward equatorial current, J, is a potassium current. With the injection of outward current, I, the PD becomes more negative, the outward equatorial current, J, decreases, and the inward current at the optical poles increases. This suggests that there are separate electrical loops for K+ and Na+ that are partially linked by the Na, K-pump. Using Ohm's law, it is possible to calculate the input resistance (R = delta PD/I), the resistance related to the production of J (RJ = delta PD/delta J), and the effect of the combined resistances (delta J/I). The driving force for J can be estimated (PDJ = 0-PD). The relationships among currents, voltages and resistance can be used to determine the characteristics of the membranes that are associated with the outward potassium current observed at the equator. The effects of graded deformation of the lens were determined. The effects were reversible. The sites of inward and outward currents were not altered. Following deformation, the equatorial current, J, increased, and the PD became less negative. The PDJ = 0 remains the same so the ratio of K

Measuring kinetic drivers of pneumolysin pore structure.

PubMed

Gilbert, Robert J C; Sonnen, Andreas F-P

2016-05-01

Most membrane attack complex-perforin/cholesterol-dependent cytolysin (MACPF/CDC) proteins are thought to form pores in target membranes by assembling into pre-pore oligomers before undergoing a pre-pore to pore transition. Assembly during pore formation is into both full rings of subunits and incomplete rings (arcs). The balance between arcs and full rings is determined by a mechanism dependent on protein concentration in which arc pores arise due to kinetic trapping of the pre-pore forms by the depletion of free protein subunits during oligomerization. Here we describe the use of a kinetic assay to study pore formation in red blood cells by the MACPF/CDC pneumolysin from Streptococcus pneumoniae. We show that cell lysis displays two kinds of dependence on protein concentration. At lower concentrations, it is dependent on the pre-pore to pore transition of arc oligomers, which we show to be a cooperative process. At higher concentrations, it is dependent on the amount of pneumolysin bound to the membrane and reflects the affinity of the protein for its receptor, cholesterol. A lag occurs before cell lysis begins; this is dependent on oligomerization of pneumolysin. Kinetic dissection of cell lysis by pneumolysin demonstrates the capacity of MACPF/CDCs to generate pore-forming oligomeric structures of variable size with, most likely, different functional roles in biology.

Non-equivalent role of TM2 gating hinges in heteromeric Kir4.1/Kir5.1 potassium channels

PubMed Central

Shang, Lijun

2007-01-01

Comparison of the crystal structures of the KcsA and MthK potassium channels suggests that the process of opening a K+ channel involves pivoted bending of the inner pore-lining helices at a highly conserved glycine residue. This bending motion is proposed to splay the transmembrane domains outwards to widen the gate at the “helix-bundle crossing”. However, in the inwardly rectifying (Kir) potassium channel family, the role of this “hinge” residue in the second transmembrane domain (TM2) and that of another putative glycine gating hinge at the base of TM2 remain controversial. We investigated the role of these two positions in heteromeric Kir4.1/Kir5.1 channels, which are unique amongst Kir channels in that both subunits lack a conserved glycine at the upper hinge position. Contrary to the effect seen in other channels, increasing the potential flexibility of TM2 by glycine substitutions at the upper hinge position decreases channel opening. Furthermore, the contribution of the Kir4.1 subunit to this process is dominant compared to Kir5.1, demonstrating a non-equivalent contribution of these two subunits to the gating process. A homology model of heteromeric Kir4.1/Kir5.1 shows that these upper “hinge” residues are in close contact with the base of the pore α-helix that supports the selectivity filter. Our results also indicate that the highly conserved glycine at the “lower” gating hinge position is required for tight packing of the TM2 helices at the helix-bundle crossing, rather than acting as a hinge residue. PMID:17657484

Dialysate Potassium and Mortality in a Prospective Hemodialysis Cohort.

PubMed

Ferrey, Antoney; You, Amy S; Kovesdy, Csaba P; Nakata, Tracy; Veliz, Mary; Nguyen, Danh V; Kalantar-Zadeh, Kamyar; Rhee, Connie M

2018-06-07

Studies examining the association of dialysate potassium concentration and mortality in hemodialysis patients show conflicting findings. We hypothesized that low dialysate potassium concentrations are associated with higher mortality, particularly in patients with high pre-dialysis serum potassium concentrations. We evaluated 624 hemodialysis patients from the prospective Malnutrition, Diet, and Racial Disparities in Kidney Disease study recruited from 16 outpatient dialysis facilities over 2011-2015 who underwent protocolized collection of dialysis treatment characteristics every 6 months. We examined the association of dialysate potassium concentration, categorized as 1, 2, and 3 mEq/L, with all-cause mortality risk in the -overall cohort, and stratified by pre-dialysis serum potassium (< 5 vs. ≥5 mEq/L) using case-mix adjusted Cox models. In baseline analyses, dialysate potassium concentrations of 1 mEq/L were associated with higher mortality, whereas concentrations of 3 mEq/L were associated with similar mortality in the overall cohort (reference: 2 mEq/L): adjusted hazard ratios (aHRs; 95% CI) 1.70 (1.01-2.88) and 0.95 (0.64-1.39), respectively. In analyses stratified by serum potassium, baseline dialysate potassium concentrations of 1 mEq/L were associated with higher mortality in patients with serum potassium ≥5 mEq/L but not in those with serum potassium < 5 mEq/L: aHRs (95% CI) 2.87 (1.51-5.46) and 0.74 (0.27-2.07), respectively (p interaction = 0.04). These findings were robust with incremental adjustment for serum potassium, potassium-binding resins, and potassium-modifying medications. Low (1 mEq/L) dialysate potassium -concentrations were associated with higher mortality, particularly in hemodialysis patients with high pre-dialysis serum potassium. Further studies are needed to identify therapeutic strategies that mitigate inter-dialytic serum potassium accumulation and subsequent high dialysate serum potassium gradients in this population. �

Simultaneous recovery of phosphorus and potassium as magnesium potassium phosphate from synthetic sewage sludge effluent.

PubMed

Nakao, Satoshi; Nishio, Takayuki; Kanjo, Yoshinori

2017-10-01

Bench-scale experiments were performed to investigate simultaneous recovery of phosphorus and potassium from synthetic sewage sludge effluent as crystals of magnesium potassium phosphate (MPP or struvite-(K), MgKPO 4 ·6H 2 O). The optimal pH of MPP formation was 11.5. A phosphorus level of at least 3 mM and K:P molar ratio over 3 were necessary to form MPP, which showed higher content rate of phosphorus and potassium in precipitate. MPP crystallization was confirmed by analysing the precipitates using a scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX) apparatus and an X-ray Diffractometer (XRD). Inhibition of MPP crystallization by iron and aluminium was confirmed by precipitation experiments and SEM-EDX analysis. Potassium ratio against magnesium in precipitate decreased for iron concentrations greater than over 0.2 mM and aluminium concentrations over 0.05 mM.

Dietary potassium regulates vascular calcification and arterial stiffness.

PubMed

Sun, Yong; Byon, Chang Hyun; Yang, Youfeng; Bradley, Wayne E; Dell'Italia, Louis J; Sanders, Paul W; Agarwal, Anupam; Wu, Hui; Chen, Yabing

2017-10-05

Vascular calcification is a risk factor that predicts adverse cardiovascular complications of several diseases including atherosclerosis. Reduced dietary potassium intake has been linked to cardiovascular diseases such as hypertension and incidental stroke, although the underlying molecular mechanisms remain largely unknown. Using the ApoE-deficient mouse model, we demonstrated for the first time to our knowledge that reduced dietary potassium (0.3%) promoted atherosclerotic vascular calcification and increased aortic stiffness, compared with normal (0.7%) potassium-fed mice. In contrast, increased dietary potassium (2.1%) attenuated vascular calcification and aortic stiffness. Mechanistically, reduction in the potassium concentration to the lower limit of the physiological range increased intracellular calcium, which activated a cAMP response element-binding protein (CREB) signal that subsequently enhanced autophagy and promoted vascular smooth muscle cell (VSMC) calcification. Inhibition of calcium signals and knockdown of either CREB or ATG7, an autophagy regulator, attenuated VSMC calcification induced by low potassium. Consistently, elevated autophagy and CREB signaling were demonstrated in the calcified arteries from low potassium diet-fed mice as well as aortic arteries exposed to low potassium ex vivo. These studies established a potentially novel causative role of dietary potassium intake in regulating atherosclerotic vascular calcification and stiffness, and uncovered mechanisms that offer opportunities to develop therapeutic strategies to control vascular disease.

Temperature and Pressure from Collapsing Pores in HMX

NASA Astrophysics Data System (ADS)

Hardin, D. Barrett

2017-06-01

The thermal and mechanical response of collapsing voids in HMX is analyzed. In this work, the focus is simulating the temperature and pressure fields arising from isolated, idealized pores as they collapse in the presence of a shock. HMX slabs are numerically generated which contain a single pore, isolated from the boundaries to remove all wave reflections. In order to understand the primary pore characteristics leading to temperature rise, a series of 2D, plane strain simulations are conducted on HMX slabs containing both cylindrical and elliptical pores of constant size equal to the area of a circular pore with a 1 micron diameter. Each of these pore types is then subjected to shock pressures ranging from a weak shock that is unable to fully collapse the pore to a strong shock which overwhelms the tendency for localization. Results indicate that as shock strength increases, pore collapse phenomenology for a cylindrical pore transitions from a mode dominated by localized melt cracking to an idealized hydrodynamic pore collapse. For the case of elliptical pores, the orientation causing maximum temperature and pressure rise is found. The relative heating in elliptical pores is then quantified as a function of pore orientation and aspect ratio for a pore of a given area. Distribution A: Distribution unlimited. (96TW 2017-0036).

21 CFR 582.1804 - Sodium potassium tartrate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Sodium potassium tartrate. 582.1804 Section 582.1804 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Additives § 582.1804 Sodium potassium tartrate. (a) Product. Sodium potassium tartrate. (b) Conditions of...

21 CFR 582.1804 - Sodium potassium tartrate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Sodium potassium tartrate. 582.1804 Section 582.1804 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Additives § 582.1804 Sodium potassium tartrate. (a) Product. Sodium potassium tartrate. (b) Conditions of...

21 CFR 182.1129 - Aluminum potassium sulfate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Aluminum potassium sulfate. 182.1129 Section 182.1129 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Food Substances § 182.1129 Aluminum potassium sulfate. (a) Product. Aluminum potassium sulfate. (b...

21 CFR 582.1129 - Aluminum potassium sulfate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Aluminum potassium sulfate. 582.1129 Section 582.1129 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Additives § 582.1129 Aluminum potassium sulfate. (a) Product. Aluminum potassium sulfate. (b) Conditions of...

21 CFR 582.6804 - Sodium potassium tartrate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Sodium potassium tartrate. 582.6804 Section 582.6804 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....6804 Sodium potassium tartrate. (a) Product. Sodium potassium tartrate. (b) Conditions of use. This...

21 CFR 582.1129 - Aluminum potassium sulfate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Aluminum potassium sulfate. 582.1129 Section 582.1129 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Additives § 582.1129 Aluminum potassium sulfate. (a) Product. Aluminum potassium sulfate. (b) Conditions of...

21 CFR 582.1804 - Sodium potassium tartrate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Sodium potassium tartrate. 582.1804 Section 582.1804 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Additives § 582.1804 Sodium potassium tartrate. (a) Product. Sodium potassium tartrate. (b) Conditions of...

21 CFR 182.1129 - Aluminum potassium sulfate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Aluminum potassium sulfate. 182.1129 Section 182.1129 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Food Substances § 182.1129 Aluminum potassium sulfate. (a) Product. Aluminum potassium sulfate. (b...

21 CFR 582.6804 - Sodium potassium tartrate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Sodium potassium tartrate. 582.6804 Section 582.6804 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....6804 Sodium potassium tartrate. (a) Product. Sodium potassium tartrate. (b) Conditions of use. This...

21 CFR 582.1129 - Aluminum potassium sulfate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Aluminum potassium sulfate. 582.1129 Section 582.1129 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Additives § 582.1129 Aluminum potassium sulfate. (a) Product. Aluminum potassium sulfate. (b) Conditions of...

21 CFR 582.1804 - Sodium potassium tartrate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Sodium potassium tartrate. 582.1804 Section 582.1804 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Additives § 582.1804 Sodium potassium tartrate. (a) Product. Sodium potassium tartrate. (b) Conditions of...

21 CFR 582.6804 - Sodium potassium tartrate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Sodium potassium tartrate. 582.6804 Section 582.6804 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....6804 Sodium potassium tartrate. (a) Product. Sodium potassium tartrate. (b) Conditions of use. This...

21 CFR 182.1129 - Aluminum potassium sulfate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Aluminum potassium sulfate. 182.1129 Section 182.1129 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Food Substances § 182.1129 Aluminum potassium sulfate. (a) Product. Aluminum potassium sulfate. (b...

21 CFR 582.1804 - Sodium potassium tartrate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Sodium potassium tartrate. 582.1804 Section 582.1804 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Additives § 582.1804 Sodium potassium tartrate. (a) Product. Sodium potassium tartrate. (b) Conditions of...

21 CFR 182.1129 - Aluminum potassium sulfate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Aluminum potassium sulfate. 182.1129 Section 182.1129 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Food Substances § 182.1129 Aluminum potassium sulfate. (a) Product. Aluminum potassium sulfate. (b...

21 CFR 582.6804 - Sodium potassium tartrate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Sodium potassium tartrate. 582.6804 Section 582.6804 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....6804 Sodium potassium tartrate. (a) Product. Sodium potassium tartrate. (b) Conditions of use. This...

21 CFR 582.1129 - Aluminum potassium sulfate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Aluminum potassium sulfate. 582.1129 Section 582.1129 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Additives § 582.1129 Aluminum potassium sulfate. (a) Product. Aluminum potassium sulfate. (b) Conditions of...

21 CFR 182.1129 - Aluminum potassium sulfate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Aluminum potassium sulfate. 182.1129 Section 182...) SUBSTANCES GENERALLY RECOGNIZED AS SAFE Multiple Purpose GRAS Food Substances § 182.1129 Aluminum potassium sulfate. (a) Product. Aluminum potassium sulfate. (b) Conditions of use. This substance is generally...

21 CFR 582.6804 - Sodium potassium tartrate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Sodium potassium tartrate. 582.6804 Section 582.6804 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....6804 Sodium potassium tartrate. (a) Product. Sodium potassium tartrate. (b) Conditions of use. This...

Mapping Potassium

NASA Image and Video Library

2015-04-16

During the first year of NASA MESSENGER orbital mission, the spacecraft GRS instrument measured the elemental composition of Mercury surface materials. mong the most important discoveries from the GRS was the observation of higher abundances of the moderately volatile elements potassium, sodium, and chlorine than expected from previous scientific models and theories. Particularly high concentrations of these elements were observed at high northern latitudes, as illustrated in this potassium abundance map, which provides a view of the surface centered at 60° N latitude and 120° E longitude. This map was the first elemental map ever made of Mercury's surface and is to-date the only map to report absolute elemental concentrations, in comparison to element ratios. Prior to MESSENGER's arrival at Mercury, scientists expected that the planet would be depleted in moderately volatile elements, as is the case for our Moon. The unexpectedly high abundances observed with the GRS have forced a reevaluation of our understanding of the formation and evolution of Mercury. In addition, the K map provided the first evidence for distinct geochemical terranes on Mercury, as the high-potassium region was later found to also be distinct in its low Mg/Si, Ca/Si, S/Si, and high Na/Si and Cl/Si abundances. Instrument: Gamma-Ray Spectrometer (GRS) http://photojournal.jpl.nasa.gov/catalog/PIA19414

Can ash clog soil pores?

NASA Astrophysics Data System (ADS)

Stoof, Cathelijne; Stoof, Cathelijne; Gevaert, Anouk; Gevaert, Anouk; Baver, Christine; Baver, Christine; Hassanpour, Bahareh; Hassanpour, Bahareh; Morales, Veronica; Morales, Veronica; Zhang, Wei; Zhang, Wei; Martin, Deborah; Martin, Deborah; Steenhuis, Tammo; Steenhuis, Tammo

2015-04-01

Wildfire can greatly increase a landscape's vulnerability to flooding and erosion events, and ash is thought to play a large role in controlling runoff and erosion processes after wildfire. Although ash can store rainfall and thereby reduce runoff and erosion for a limited period after wildfires, it has also been hypothesized to clog soil pores and reduce infiltration. Several researchers have attributed the commonly observed increase in runoff and erosion after fire to the potential pore-clogging effect of ash. Evidence is however incomplete, as to date, research has solely focused on identifying the presence of ash in the soil, with the actual flow processes associated with the infiltration and pore-clogging of ash remaining a major unknown. In several laboratory experiments, we tested the hypothesis that ash causes pore clogging to the point that infiltration is hampered and ponding occurs. We first visualized and quantified pore-scale infiltration of water and ash in sand of a range of textures and at various infiltration rates, using a digital bright field microscope capturing both photo and video. While these visualization experiments confirm field and lab observation of ash washing into soil pores, we did not observe any clogging of pores, and have not been able to create conditions for which this does occur. Additional electrochemical analysis and measurement of saturated hydraulic conductivity indicate that pore clogging by ash is not plausible. Electrochemical analysis showed that ash and sand are both negatively charged, showing that attachment of ash to sand and any resulting clogging is unlikely. Ash also had quite high saturated conductivity, and systems where ash was mixed in or lying on top of sand had similarly high hydraulic conductivity. Based on these various experiments, we cannot confirm the hypothesis that pore clogging by ash contributes to the frequently observed increase in post-fire runoff, at least for the medium to coarse sands

Voltage-dependent gating of KCNH potassium channels lacking a covalent link between voltage-sensing and pore domains

PubMed Central

Lörinczi, Éva; Gómez-Posada, Juan Camilo; de la Peña, Pilar; Tomczak, Adam P.; Fernández-Trillo, Jorge; Leipscher, Ulrike; Stühmer, Walter; Barros, Francisco; Pardo, Luis A.

2015-01-01

Voltage-gated channels open paths for ion permeation upon changes in membrane potential, but how voltage changes are coupled to gating is not entirely understood. Two modules can be recognized in voltage-gated potassium channels, one responsible for voltage sensing (transmembrane segments S1 to S4), the other for permeation (S5 and S6). It is generally assumed that the conversion of a conformational change in the voltage sensor into channel gating occurs through the intracellular S4–S5 linker that provides physical continuity between the two regions. Using the pathophysiologically relevant KCNH family, we show that truncated proteins interrupted at, or lacking the S4–S5 linker produce voltage-gated channels in a heterologous model that recapitulate both the voltage-sensing and permeation properties of the complete protein. These observations indicate that voltage sensing by the S4 segment is transduced to the channel gate in the absence of physical continuity between the modules. PMID:25818916

Voltage-dependent gating of KCNH potassium channels lacking a covalent link between voltage-sensing and pore domains.

PubMed

Lörinczi, Éva; Gómez-Posada, Juan Camilo; de la Peña, Pilar; Tomczak, Adam P; Fernández-Trillo, Jorge; Leipscher, Ulrike; Stühmer, Walter; Barros, Francisco; Pardo, Luis A

2015-03-30

Voltage-gated channels open paths for ion permeation upon changes in membrane potential, but how voltage changes are coupled to gating is not entirely understood. Two modules can be recognized in voltage-gated potassium channels, one responsible for voltage sensing (transmembrane segments S1 to S4), the other for permeation (S5 and S6). It is generally assumed that the conversion of a conformational change in the voltage sensor into channel gating occurs through the intracellular S4-S5 linker that provides physical continuity between the two regions. Using the pathophysiologically relevant KCNH family, we show that truncated proteins interrupted at, or lacking the S4-S5 linker produce voltage-gated channels in a heterologous model that recapitulate both the voltage-sensing and permeation properties of the complete protein. These observations indicate that voltage sensing by the S4 segment is transduced to the channel gate in the absence of physical continuity between the modules.

Voltage-dependent gating of KCNH potassium channels lacking a covalent link between voltage-sensing and pore domains

NASA Astrophysics Data System (ADS)

Lörinczi, Éva; Gómez-Posada, Juan Camilo; de La Peña, Pilar; Tomczak, Adam P.; Fernández-Trillo, Jorge; Leipscher, Ulrike; Stühmer, Walter; Barros, Francisco; Pardo, Luis A.

2015-03-01

Voltage-gated channels open paths for ion permeation upon changes in membrane potential, but how voltage changes are coupled to gating is not entirely understood. Two modules can be recognized in voltage-gated potassium channels, one responsible for voltage sensing (transmembrane segments S1 to S4), the other for permeation (S5 and S6). It is generally assumed that the conversion of a conformational change in the voltage sensor into channel gating occurs through the intracellular S4-S5 linker that provides physical continuity between the two regions. Using the pathophysiologically relevant KCNH family, we show that truncated proteins interrupted at, or lacking the S4-S5 linker produce voltage-gated channels in a heterologous model that recapitulate both the voltage-sensing and permeation properties of the complete protein. These observations indicate that voltage sensing by the S4 segment is transduced to the channel gate in the absence of physical continuity between the modules.

21 CFR 582.1077 - Potassium acid tartrate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Potassium acid tartrate. 582.1077 Section 582.1077 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1077 Potassium acid tartrate. (a) Product. Potassium acid tartrate. (b) Conditions of use...

21 CFR 582.1077 - Potassium acid tartrate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Potassium acid tartrate. 582.1077 Section 582.1077 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1077 Potassium acid tartrate. (a) Product. Potassium acid tartrate. (b) Conditions of use...

21 CFR 582.1077 - Potassium acid tartrate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Potassium acid tartrate. 582.1077 Section 582.1077 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1077 Potassium acid tartrate. (a) Product. Potassium acid tartrate. (b) Conditions of use...

40 CFR 721.10553 - Potassium titanium oxide.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Potassium titanium oxide. 721.10553... Substances § 721.10553 Potassium titanium oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as potassium titanium oxide (PMN P-06-149; CAS No. 12673-69...

40 CFR 721.10553 - Potassium titanium oxide.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Potassium titanium oxide. 721.10553... Substances § 721.10553 Potassium titanium oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as potassium titanium oxide (PMN P-06-149; CAS No. 12673-69...

21 CFR 582.1077 - Potassium acid tartrate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Potassium acid tartrate. 582.1077 Section 582.1077 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1077 Potassium acid tartrate. (a) Product. Potassium acid tartrate. (b) Conditions of use...

Investigating Hydrophilic Pores in Model Lipid Bilayers Using Molecular Simulations: Correlating Bilayer Properties with Pore-Formation Thermodynamics.

PubMed

Hu, Yuan; Sinha, Sudipta Kumar; Patel, Sandeep

2015-06-23

Cell-penetrating and antimicrobial peptides show a remarkable ability to translocate across physiological membranes. Along with factors such as electric-potential-induced perturbations of membrane structure and surface tension effects, experiments invoke porelike membrane configurations during the solute transfer process into vesicles and cells. The initiation and formation of pores are associated with a nontrivial free-energy cost, thus necessitating a consideration of the factors associated with pore formation and the attendant free energies. Because of experimental and modeling challenges related to the long time scales of the translocation process, we use umbrella sampling molecular dynamics simulations with a lipid-density-based order parameter to investigate membrane-pore-formation free energy employing Martini coarse-grained models. We investigate structure and thermodynamic features of the pore in 18 lipids spanning a range of headgroups, charge states, acyl chain lengths, and saturation. We probe the dependence of pore-formation barriers on the area per lipid, lipid bilayer thickness, and membrane bending rigidities in three different lipid classes. The pore-formation free energy in pure bilayers and peptide translocating scenarios are significantly coupled with bilayer thickness. Thicker bilayers require more reversible work to create pores. The pore-formation free energy is higher in peptide-lipid systems than in peptide-free lipid systems due to penalties to maintain the solvation of charged hydrophilic solutes within the membrane environment.

Mechanism of inhibition of mouse Slo3 (KCa 5.1) potassium channels by quinine, quinidine and barium.

PubMed

Wrighton, David C; Muench, Stephen P; Lippiat, Jonathan D

2015-09-01

The Slo3 (KCa 5.1) channel is a major component of mammalian KSper (sperm potassium conductance) channels and inhibition of these channels by quinine and barium alters sperm motility. The aim of this investigation was to determine the mechanism by which these drugs inhibit Slo3 channels. Mouse (m) Slo3 (KCa 5.1) channels or mutant forms were expressed in Xenopus oocytes and currents recorded with 2-electrode voltage-clamp. Gain-of-function mSlo3 mutations were used to explore the state-dependence of the inhibition. The interaction between quinidine and mSlo3 channels was modelled by in silico docking. Several drugs known to block KSper also affected mSlo3 channels with similar levels of inhibition. The inhibition induced by extracellular barium was prevented by increasing the extracellular potassium concentration. R196Q and F304Y mutations in the mSlo3 voltage sensor and pore, respectively, both increased channel activity. The F304Y mutation did not alter the effects of barium, but increased the potency of inhibition by both quinine and quinidine approximately 10-fold; this effect was not observed with the R196Q mutation. Block of mSlo3 channels by quinine, quinidine and barium is not state-dependent. Barium inhibits mSlo3 outside the cell by interacting with the selectivity filter, whereas quinine and quinidine act from the inside, by binding in a hydrophobic pocket formed by the S6 segment of each subunit. Furthermore, we propose that the Slo3 channel activation gate lies deep within the pore between F304 in the S6 segment and the selectivity filter. © 2015 The Authors. British Journal of Pharmacology published by John Wiley & Sons Ltd on behalf of The British Pharmacological Society.

21 CFR 582.5622 - Potassium chloride.

Code of Federal Regulations, 2012 CFR

2012-04-01

... DRUGS, FEEDS, AND RELATED PRODUCTS SUBSTANCES GENERALLY RECOGNIZED AS SAFE Nutrients and/or Dietary Supplements 1 § 582.5622 Potassium chloride. (a) Product. Potassium chloride. (b) Conditions of use. This...

21 CFR 582.5622 - Potassium chloride.

Code of Federal Regulations, 2014 CFR

2014-04-01

... DRUGS, FEEDS, AND RELATED PRODUCTS SUBSTANCES GENERALLY RECOGNIZED AS SAFE Nutrients and/or Dietary Supplements 1 § 582.5622 Potassium chloride. (a) Product. Potassium chloride. (b) Conditions of use. This...

21 CFR 582.5622 - Potassium chloride.

Code of Federal Regulations, 2013 CFR

2013-04-01

... DRUGS, FEEDS, AND RELATED PRODUCTS SUBSTANCES GENERALLY RECOGNIZED AS SAFE Nutrients and/or Dietary Supplements 1 § 582.5622 Potassium chloride. (a) Product. Potassium chloride. (b) Conditions of use. This...

21 CFR 582.5622 - Potassium chloride.

Code of Federal Regulations, 2011 CFR

2011-04-01

... DRUGS, FEEDS, AND RELATED PRODUCTS SUBSTANCES GENERALLY RECOGNIZED AS SAFE Nutrients and/or Dietary Supplements 1 § 582.5622 Potassium chloride. (a) Product. Potassium chloride. (b) Conditions of use. This...

21 CFR 582.5622 - Potassium chloride.

Code of Federal Regulations, 2010 CFR

2010-04-01

... DRUGS, FEEDS, AND RELATED PRODUCTS SUBSTANCES GENERALLY RECOGNIZED AS SAFE Nutrients and/or Dietary Supplements 1 § 582.5622 Potassium chloride. (a) Product. Potassium chloride. (b) Conditions of use. This...

Potassium acetate and potassium lactate enhance the microbiological and physical properties of marinated catfish fillets

USDA-ARS?s Scientific Manuscript database

Sodium or potassium salts such as lactate and acetate can be used to inhibit the growth of spoilage bacteria and food-borne pathogens, and thereby prolong the shelf-life of refrigerated seafood. However, minimal information is available regarding the combined effects of potassium salts (acetate and ...

Maximizing and stabilizing luminescence from halide perovskites with potassium passivation

NASA Astrophysics Data System (ADS)

Abdi-Jalebi, Mojtaba; Andaji-Garmaroudi, Zahra; Cacovich, Stefania; Stavrakas, Camille; Philippe, Bertrand; Richter, Johannes M.; Alsari, Mejd; Booker, Edward P.; Hutter, Eline M.; Pearson, Andrew J.; Lilliu, Samuele; Savenije, Tom J.; Rensmo, Håkan; Divitini, Giorgio; Ducati, Caterina; Friend, Richard H.; Stranks, Samuel D.

2018-03-01

Metal halide perovskites are of great interest for various high-performance optoelectronic applications. The ability to tune the perovskite bandgap continuously by modifying the chemical composition opens up applications for perovskites as coloured emitters, in building-integrated photovoltaics, and as components of tandem photovoltaics to increase the power conversion efficiency. Nevertheless, performance is limited by non-radiative losses, with luminescence yields in state-of-the-art perovskite solar cells still far from 100 per cent under standard solar illumination conditions. Furthermore, in mixed halide perovskite systems designed for continuous bandgap tunability (bandgaps of approximately 1.7 to 1.9 electronvolts), photoinduced ion segregation leads to bandgap instabilities. Here we demonstrate substantial mitigation of both non-radiative losses and photoinduced ion migration in perovskite films and interfaces by decorating the surfaces and grain boundaries with passivating potassium halide layers. We demonstrate external photoluminescence quantum yields of 66 per cent, which translate to internal yields that exceed 95 per cent. The high luminescence yields are achieved while maintaining high mobilities of more than 40 square centimetres per volt per second, providing the elusive combination of both high luminescence and excellent charge transport. When interfaced with electrodes in a solar cell device stack, the external luminescence yield—a quantity that must be maximized to obtain high efficiency—remains as high as 15 per cent, indicating very clean interfaces. We also demonstrate the inhibition of transient photoinduced ion-migration processes across a wide range of mixed halide perovskite bandgaps in materials that exhibit bandgap instabilities when unpassivated. We validate these results in fully operating solar cells. Our work represents an important advance in the construction of tunable metal halide perovskite films and interfaces that can

Maximizing and stabilizing luminescence from halide perovskites with potassium passivation.

PubMed

Abdi-Jalebi, Mojtaba; Andaji-Garmaroudi, Zahra; Cacovich, Stefania; Stavrakas, Camille; Philippe, Bertrand; Richter, Johannes M; Alsari, Mejd; Booker, Edward P; Hutter, Eline M; Pearson, Andrew J; Lilliu, Samuele; Savenije, Tom J; Rensmo, Håkan; Divitini, Giorgio; Ducati, Caterina; Friend, Richard H; Stranks, Samuel D

2018-03-21

Metal halide perovskites are of great interest for various high-performance optoelectronic applications. The ability to tune the perovskite bandgap continuously by modifying the chemical composition opens up applications for perovskites as coloured emitters, in building-integrated photovoltaics, and as components of tandem photovoltaics to increase the power conversion efficiency. Nevertheless, performance is limited by non-radiative losses, with luminescence yields in state-of-the-art perovskite solar cells still far from 100 per cent under standard solar illumination conditions. Furthermore, in mixed halide perovskite systems designed for continuous bandgap tunability (bandgaps of approximately 1.7 to 1.9 electronvolts), photoinduced ion segregation leads to bandgap instabilities. Here we demonstrate substantial mitigation of both non-radiative losses and photoinduced ion migration in perovskite films and interfaces by decorating the surfaces and grain boundaries with passivating potassium halide layers. We demonstrate external photoluminescence quantum yields of 66 per cent, which translate to internal yields that exceed 95 per cent. The high luminescence yields are achieved while maintaining high mobilities of more than 40 square centimetres per volt per second, providing the elusive combination of both high luminescence and excellent charge transport. When interfaced with electrodes in a solar cell device stack, the external luminescence yield-a quantity that must be maximized to obtain high efficiency-remains as high as 15 per cent, indicating very clean interfaces. We also demonstrate the inhibition of transient photoinduced ion-migration processes across a wide range of mixed halide perovskite bandgaps in materials that exhibit bandgap instabilities when unpassivated. We validate these results in fully operating solar cells. Our work represents an important advance in the construction of tunable metal halide perovskite films and interfaces that can approach

Tandem Organic Light-Emitting Diodes.

PubMed

Fung, Man-Keung; Li, Yan-Qing; Liao, Liang-Sheng

2016-12-01

A tandem organic light-emitting diode (OLED) is an organic optoelectronic device that has two or more electroluminescence (EL) units connected electrically in series with unique intermediate connectors within the device. Researchers have studied this new OLED architecture with growing interest and have found that the current efficiency of a tandem OLED containing N EL units (N > 1) should be N times that of a conventional OLED containing only a single EL unit. Therefore, this new architecture is potentially useful for constructing high-efficiency, high-luminance, and long-lifetime OLED displays and organic solid-state lighting sources. In a tandem OLED, the intermediate connector plays a crucial role in determining the effectiveness of the stacked EL units. The interfaces in the connector control the inner charge generation and charge injection into the adjacent EL units. Meanwhile, the transparency and the thickness of the connector affect the light output of the device. Therefore, the intermediate connector should be made to meet both the electrical and optical requirements for achieving optimal performance. Here, recent advances in the research of the tandem OLEDs is discussed, with the main focus on material selection and interface studies in the intermediate connectors, as well as the optical design of the tandem OLEDs. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Butanolysis: Comparison of potassium hydroxide and potassium tert-butoxide as catalyst for biodiesel preparing from rapeseed oil.

PubMed

Musil, Martin; Skopal, Frantisek; Hájek, Martin; Vavra, Ales

2018-07-15

Biodiesel is a mixture of esters of fatty acids (most often palmitic, stearic and oleic) and lower alcohols (in our work butanol) produced by transesterification. It is a renewable source of energy, prepared from triacylglycerides, which are contained in vegetable oils and animal fats. This work focuses on alkaline catalyzed transesterification of rapeseed oil with butanol and comparison of two catalysts (potassium hydroxide and potassium tert-butoxide). In industry is usually transesterification of rapeseed oil carried out like reaction catalyzed by potassium hydroxide. Potassium hydroxide have high content of K 2 CO 3 , KHCO 3 and water. Moreover water is formed by neutralization of potassium hydroxide with free fatty acids contained in oil. In cause of tert-butoxide catalyzed reaction, it is not possible because tert-butoxide have not a OH - aniont, which is needed for water forming. The influence of various conditions (addition of water, temperature of separation, intensity of stirring and type of catalyst) on butanolysis process was studied for both catalysts. For both catalysts dependence of conversions on time were plotted. When tert-butoxide was used, satisfactory phase separation was not achieved. The only way was separation of hot crude reaction mixture without adding water. Ester formed by this method had high content of free glycerol and soaps, but reached higher conversion. The best results were obtained with KOH and subsequent separation of cold crude reaction mixture with the addition of water and slow stirring. The difference between reactions catalyzed by potassium hydroxide and potassium tert-butoxide was described. Copyright © 2018 Elsevier Ltd. All rights reserved.

Dissolution at porous interfaces VI: Multiple pore systems.

PubMed

Grijseels, H; Crommelin, D J; De Blaey, C J

1984-12-01

With the aid of rapidly dissolving sodium chloride particles, cubic pores were made in the surface of a theophylline tablet. The influence of the pores on the dissolution rate of the surface was investigated in a rotating disk apparatus. Like the drilled pores used in earlier studies, downstream on the surface they caused a turbulent flow regimen with the development of a trough due to enhanced erosion. The phenomenon of a critical pore diameter, discovered with single, drilled pores, seems to be applicable to the cubic pores investigated in this study, although a higher degree of surface coverage with pores caused complications, probably due to particles bordering one another and forming larger pores. The behavior of the porous surfaces at different rotation speeds was studied. Due to the presence of pores the laminar character of the boundary layer flow changes to turbulent, which induces locally an increased dissolution flux in the wake of a pore.

Analysis of inter-residue contacts reveals folding stabilizers in P-loops of potassium, sodium, and TRPV channels.

PubMed

Korkosh, V S; Zhorov, B S; Tikhonov, D B

2016-05-01

The family of P-loop channels includes potassium, sodium, calcium, cyclic nucleotide-gated and TRPV channels, as well as ionotropic glutamate receptors. Despite vastly different physiological and pharmacological properties, the channels have structurally conserved folding of the pore domain. Furthermore, crystallographic data demonstrate surprisingly similar mutual disposition of transmembrane and membrane-diving helices. To understand determinants of this conservation, here we have compared available high-resolution structures of sodium, potassium, and TRPV1 channels. We found that some residues, which are in matching positions of the sequence alignment, occur in different positions in the 3D alignment. Surprisingly, we found 3D mismatches in well-packed P-helices. Analysis of energetics of individual residues in Monte Carlo minimized structures revealed cyclic patterns of energetically favorable inter- and intra-subunit contacts of P-helices with S6 helices. The inter-subunit contacts are rather conserved in all the channels, whereas the intra-subunit contacts are specific for particular types of the channels. Our results suggest that these residue-residue contacts contribute to the folding stabilization. Analysis of such contacts is important for structural and phylogenetic studies of homologous proteins.

The amiodarone derivative KB130015 activates hERG1 potassium channels via a novel mechanism

PubMed Central

Gessner, Guido; Macianskiene, Regina; Starkus, John G.; Schönherr, Roland; Heinemann, Stefan H.

2010-01-01

Human ether à go-go related gene (hERG1) potassium channels underlie the repolarizing IKr current in the heart. Since they are targets of various drugs with cardiac side effects we tested whether the amiodarone derivative 2-methyl-3-(3,5-diiodo-4-carboxymethoxybenzyl)benzofuran (KB130015) blocks hERG1 channels like its parent compound. Using patch-clamp and two-electrode voltage-clamp techniques we found that KB130015 blocks native and recombinant hERG1 channels at high voltages, but it activates them at low voltages. The activating effect has an apparent EC50 value of 12 μM and is brought about by an about 4-fold acceleration of activation kinetics and a shift in voltage-dependent activation by −16 mV. Channel activation was not use-dependent and was independent of inactivation gating. KB130015 presumably binds to the hERG1 pore from the cytosolic side and functionally competes with hERG1 block by amiodarone, E4031 (N-[4-[[1-[2-(6-methyl-2-pyridinyl)ethyl] -4-piperidinyl] carbonyl] phenyl] methanesulfonamide dihydrochloride), and sertindole. Vice versa, amiodarone attenuates hERG1 activation by KB130015. Based on synergic channel activation by mallotoxin and KB130015 we conclude that the hERG1 pore contains at least two sites for activators that are functionally coupled among each other and to the cavity-blocker site. KB130015 and amiodarone may serve as lead structures for the identification of hERG1 pore-interacting drugs favoring channel activation vs. block. PMID:20097192

Potassium Loss during Galvanotaxis of Slime Mold

PubMed Central

Anderson, John D.

1962-01-01

The posterior reticulated regions of the plasmodia of the slime mold, Physarum polycephalum, whose migration has been oriented by direct current (3.0 to 5.0 µa/mm2 in the agar substrate), contain 30 per cent less potassium than the advancing non-reticulated region. The anterior regions have the same potassium concentration as that of the controls, approximately 32 meq/kg wet weight. Differences in potassium concentration between anterior and posterior regions of control plasmodia, not oriented by electric current, are less than 5 per cent. Sodium, in contrast to potassium, is generally less concentrated in the anterior than in the posterior regions of electrically oriented plasmodia, but sodium concentrations are extremely variable. No significant difference in protein concentration was found between oriented and control plasmodia. Thirty-five per cent of the total potassium, but none of the sodium, is found in acidified ethanol precipitates from plasmodial homogenates. Potassium, but not sodium, appears to be closely associated with processes which differentiate anterior from posterior in an oriented plasmodium. PMID:13861244

Potassium Blood Test: MedlinePlus Lab Test Information

MedlinePlus

... https://medlineplus.gov/labtests/potassiumbloodtest.html Potassium Blood Test To use the sharing features on this page, please enable JavaScript. What is a Potassium Blood Test? A potassium blood test measures the amount of ...

High voltage series connected tandem junction solar battery

DOEpatents

Hanak, Joseph J.

1982-01-01

A high voltage series connected tandem junction solar battery which comprises a plurality of strips of tandem junction solar cells of hydrogenated amorphous silicon having one optical path and electrically interconnected by a tunnel junction. The layers of hydrogenated amorphous silicon, arranged in a tandem configuration, can have the same bandgap or differing bandgaps. The tandem junction strip solar cells are series connected to produce a solar battery of any desired voltage.

Suicidal ingestion of potassium permanganate crystals: a rare encounter.

PubMed

Karthik, Ravikanti; Veerendranath, Hari Prasad Kanakapura; Wali, Siddraj; Mohan, Murali N T; Kumar, Praveen A C; Trimurty, Gaganam

2014-01-01

Potassium permanganate poisoning is not common. Although Symptoms of potassium permanganate ingestion are gastrointestinal and Complications due to ingestion of potassium permanganate include cardiovascular depression, hepatic and renal damage, upper airway obstruction, bleeding tendency and methemoglobinemia. Gastric damage due to potassium permanganate has rarely been reported previously. We are reporting a 34-year old female patient who presented to our Emergency Department after suicidal ingestion of potassium permanganate crystals. After treatment, the patient was discharged home on the 8(th) day after admission. So we conclude that Emergency endoscopy has a significant role in diagnosis and management of potassium permanganate ingestion.

Suicidal Ingestion of Potassium Permanganate Crystals: A Rare Encounter

PubMed Central

Karthik, Ravikanti; Veerendranath, Hari Prasad Kanakapura; Wali, Siddraj; Mohan, Murali N T; Kumar, Praveen A. C.; Trimurty, Gaganam

2014-01-01

Potassium permanganate poisoning is not common. Although Symptoms of potassium permanganate ingestion are gastrointestinal and Complications due to ingestion of potassium permanganate include cardiovascular depression, hepatic and renal damage, upper airway obstruction, bleeding tendency and methemoglobinemia. Gastric damage due to potassium permanganate has rarely been reported previously. We are reporting a 34-year old female patient who presented to our Emergency Department after suicidal ingestion of potassium permanganate crystals. After treatment, the patient was discharged home on the 8th day after admission. So we conclude that Emergency endoscopy has a significant role in diagnosis and management of potassium permanganate ingestion. PMID:25948978

Hygroscopic properties of potassium chloride and its internal mixtures with organic compounds relevant to biomass burning aerosol particles

PubMed Central

Jing, Bo; Peng, Chao; Wang, Yidan; Liu, Qifan; Tong, Shengrui; Zhang, Yunhong; Ge, Maofa

2017-01-01

While water uptake of aerosols exerts considerable impacts on climate, the effects of aerosol composition and potential interactions between species on hygroscopicity of atmospheric particles have not been fully characterized. The water uptake behaviors of potassium chloride and its internal mixtures with water soluble organic compounds (WSOCs) related to biomass burning aerosols including oxalic acid, levoglucosan and humic acid at different mass ratios were investigated using a hygroscopicity tandem differential mobility analyzer (HTDMA). Deliquescence points of KCl/organic mixtures were observed to occur at lower RH values and over a broader RH range eventually disappearing at high organic mass fractions. This leads to substantial under-prediction of water uptake at intermediate RH. Large discrepancies for water content between model predictions and measurements were observed for KCl aerosols with 75 wt% oxalic acid content, which is likely due to the formation of less hygroscopic potassium oxalate from interactions between KCl and oxalic acid without taken into account in the model methods. Our results also indicate strong influence of levoglucosan on hygroscopic behaviors of multicomponent mixed particles. These findings are important in further understanding the role of interactions between WSOCs and inorganic salt on hygroscopic behaviors and environmental effects of atmospheric particles. PMID:28240258

Hygroscopic properties of potassium chloride and its internal mixtures with organic compounds relevant to biomass burning aerosol particles.

PubMed

Jing, Bo; Peng, Chao; Wang, Yidan; Liu, Qifan; Tong, Shengrui; Zhang, Yunhong; Ge, Maofa

2017-02-27

While water uptake of aerosols exerts considerable impacts on climate, the effects of aerosol composition and potential interactions between species on hygroscopicity of atmospheric particles have not been fully characterized. The water uptake behaviors of potassium chloride and its internal mixtures with water soluble organic compounds (WSOCs) related to biomass burning aerosols including oxalic acid, levoglucosan and humic acid at different mass ratios were investigated using a hygroscopicity tandem differential mobility analyzer (HTDMA). Deliquescence points of KCl/organic mixtures were observed to occur at lower RH values and over a broader RH range eventually disappearing at high organic mass fractions. This leads to substantial under-prediction of water uptake at intermediate RH. Large discrepancies for water content between model predictions and measurements were observed for KCl aerosols with 75 wt% oxalic acid content, which is likely due to the formation of less hygroscopic potassium oxalate from interactions between KCl and oxalic acid without taken into account in the model methods. Our results also indicate strong influence of levoglucosan on hygroscopic behaviors of multicomponent mixed particles. These findings are important in further understanding the role of interactions between WSOCs and inorganic salt on hygroscopic behaviors and environmental effects of atmospheric particles.

Hygroscopic properties of potassium chloride and its internal mixtures with organic compounds relevant to biomass burning aerosol particles

NASA Astrophysics Data System (ADS)

Jing, Bo; Peng, Chao; Wang, Yidan; Liu, Qifan; Tong, Shengrui; Zhang, Yunhong; Ge, Maofa

2017-02-01

While water uptake of aerosols exerts considerable impacts on climate, the effects of aerosol composition and potential interactions between species on hygroscopicity of atmospheric particles have not been fully characterized. The water uptake behaviors of potassium chloride and its internal mixtures with water soluble organic compounds (WSOCs) related to biomass burning aerosols including oxalic acid, levoglucosan and humic acid at different mass ratios were investigated using a hygroscopicity tandem differential mobility analyzer (HTDMA). Deliquescence points of KCl/organic mixtures were observed to occur at lower RH values and over a broader RH range eventually disappearing at high organic mass fractions. This leads to substantial under-prediction of water uptake at intermediate RH. Large discrepancies for water content between model predictions and measurements were observed for KCl aerosols with 75 wt% oxalic acid content, which is likely due to the formation of less hygroscopic potassium oxalate from interactions between KCl and oxalic acid without taken into account in the model methods. Our results also indicate strong influence of levoglucosan on hygroscopic behaviors of multicomponent mixed particles. These findings are important in further understanding the role of interactions between WSOCs and inorganic salt on hygroscopic behaviors and environmental effects of atmospheric particles.

Hydrogen Sorption Properties of Potassium Alanate

NASA Astrophysics Data System (ADS)

Matysina, Z. A.; Zaginaichenko, S. Yu.; Schur, D. V.; Zolotarenko, Al. D.; Zolotarenko, An. D.; Gabdulin, M. T.

2018-06-01

Molecular kinetic representations were used to develop the statistical theory of phase transformations of thermal decomposition of KAlH4 potassium alanate with formation of a more complex K3AlH6 alanate and KH potassium hydride and subsequent dehydrogenation of the latter accompanied with free hydrogen, pure potassium and aluminum yield. Temperature dependence of the emitted free hydrogen was established. Isotherms and isopleths were built. The possibility of hysteresis effect manifestation was established. The results of calculations were compared to the experimental data.

Potassium in the atmosphere of Mercury

NASA Technical Reports Server (NTRS)

Potter, A. E.; Morgan, T. H.

1986-01-01

Spectral data are reported from a search for potassium in the Mercury atmosphere. The data were collected with instrumentation at Kitt Peak (7699 A) and at McDonald Observatory (7698.98 and 7664.86 A). The equivalent mean widths of the potassium emission lines observed are tabulated, along with the estimated abundances, which are compared with sodium abundances as determined by resonance lines. The average column abundance of potassium is projected to be 1 billion atoms/sq cm, about 1 percent the column abundance of sodium.

A thermodynamic approach to alamethicin pore formation.

PubMed

Rahaman, Asif; Lazaridis, Themis

2014-01-01

The structure and energetics of alamethicin Rf30 monomer to nonamer in cylindrical pores of 5 to 11Å radius are investigated using molecular dynamics simulations in an implicit membrane model that includes the free energy cost of acyl chain hydrophobic area exposure. Stable, low energy pores are obtained for certain combinations of radius and oligomeric number. The trimer and the tetramer formed 6Å pores that appear closed while the larger oligomers formed open pores at their optimal radius. The hexamer in an 8Å pore and the octamer in an 11Å pore give the lowest effective energy per monomer. However, all oligomers beyond the pentamer have comparable energies, consistent with the observation of multiple conductance levels. The results are consistent with the widely accepted "barrel-stave" model. The N terminal portion of the molecule exhibits smaller tilt with respect to the membrane normal than the C terminal portion, resulting in a pore shape that is a hybrid between a funnel and an hourglass. Transmembrane voltage has little effect on the structure of the oligomers but enhances or decreases their stability depending on its orientation. Antiparallel bundles are lower in energy than the commonly accepted parallel ones and could be present under certain experimental conditions. Dry aggregates (without an aqueous pore) have lower average effective energy than the corresponding aggregates in a pore, suggesting that alamethicin pores may be excited states that are stabilized in part by voltage and in part by the ion flow itself. © 2013.

Molecular and functional characterization of Anopheles gambiae inward rectifier potassium (Kir1) channels: a novel role in egg production.

PubMed

Raphemot, Rene; Estévez-Lao, Tania Y; Rouhier, Matthew F; Piermarini, Peter M; Denton, Jerod S; Hillyer, Julián F

2014-08-01

Inward rectifier potassium (Kir) channels play essential roles in regulating diverse physiological processes. Although Kir channels are encoded in mosquito genomes, their functions remain largely unknown. In this study, we identified the members of the Anopheles gambiae Kir gene family and began to investigate their function. Notably, we sequenced the A. gambiae Kir1 (AgKir1) gene and showed that it encodes all the canonical features of a Kir channel: an ion pore that is composed of a pore helix and a selectivity filter, two transmembrane domains that flank the ion pore, and the so-called G-loop. Heterologous expression of AgKir1 in Xenopus oocytes revealed that this gene encodes a functional, barium-sensitive Kir channel. Quantitative RT-PCR experiments then showed that relative AgKir1 mRNA levels are highest in the pupal stage, and that AgKir1 mRNA is enriched in the adult ovaries. Gene silencing of AgKir1 by RNA interference did not affect the survival of female mosquitoes following a blood meal, but decreased their egg output. These data provide evidence for a new role of Kir channels in mosquito fecundity, and further validates them as promising molecular targets for the development of a new class of mosquitocides to be used in vector control. Copyright © 2014 Elsevier Ltd. All rights reserved.

Nanoscale Pore Imaging and Pore Scale Fluid Flow Modeling in Chalk

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tomutsa, Liviu; Silin, Dmitriy

2004-08-19

For many rocks of high economic interest such as chalk, diatomite, tight gas sands or coal, nanometer scale resolution is needed to resolve the 3D-pore structure, which controls the flow and trapping of fluids in the rocks. Such resolutions cannot be achieved with existing tomographic technologies. A new 3D imaging method, based on serial sectioning and using the Focused Ion Beam (FIB) technology has been developed. FIB allows for the milling of layers as thin as 10 nanometers by using accelerated Ga+ ions to sputter atoms from the sample surface. After each milling step, as a new surface is exposed,more » a 2D image of this surface is generated. Next, the 2D images are stacked to reconstruct the 3D pore or grain structure. Resolutions as high as 10 nm are achievable using such a technique. A new robust method of pore-scale fluid flow modeling has been developed and applied to sandstone and chalk samples. The method uses direct morphological analysis of the pore space to characterize the petrophysical properties of diverse formations. Not only petrophysical properties (porosity, permeability, relative permeability and capillary pressures) can be computed but also flow processes, such as those encountered in various IOR approaches, can be simulated. Petrophysical properties computed with the new method using the new FIB data will be presented. Present study is a part of the development of an Electronic Core Laboratory at LBNL/UCB.« less

Pore-formation by adenylate cyclase toxoid activates dendritic cells to prime CD8+ and CD4+ T cells.

PubMed

Svedova, Martina; Masin, Jiri; Fiser, Radovan; Cerny, Ondrej; Tomala, Jakub; Freudenberg, Marina; Tuckova, Ludmila; Kovar, Marek; Dadaglio, Gilles; Adkins, Irena; Sebo, Peter

2016-04-01

The adenylate cyclase toxin-hemolysin (CyaA) of Bordetella pertussis is a bi-functional leukotoxin. It penetrates myeloid phagocytes expressing the complement receptor 3 and delivers into their cytosol its N-terminal adenylate cyclase enzyme domain (~400 residues). In parallel, ~1300 residue-long RTX hemolysin moiety of CyaA forms cation-selective pores and permeabilizes target cell membrane for efflux of cytosolic potassium ions. The non-enzymatic CyaA-AC(-) toxoid, has repeatedly been successfully exploited as an antigen delivery tool for stimulation of adaptive T-cell immune responses. We show that the pore-forming activity confers on the CyaA-AC(-) toxoid a capacity to trigger Toll-like receptor and inflammasome signaling-independent maturation of CD11b-expressing dendritic cells (DC). The DC maturation-inducing potency of mutant toxoid variants in vitro reflected their specifically enhanced or reduced pore-forming activity and K(+) efflux. The toxoid-induced in vitro phenotypic maturation of DC involved the activity of mitogen activated protein kinases p38 and JNK and comprised increased expression of maturation markers, interleukin 6, chemokines KC and LIX and granulocyte-colony-stimulating factor secretion, prostaglandin E2 production and enhancement of chemotactic migration of DC. Moreover, i.v. injected toxoids induced maturation of splenic DC in function of their cell-permeabilizing capacity. Similarly, the capacity of DC to stimulate CD8(+) and CD4(+) T-cell responses in vitro and in vivo was dependent on the pore-forming activity of CyaA-AC(-). This reveals a novel self-adjuvanting capacity of the CyaA-AC(-) toxoid that is currently under clinical evaluation as a tool for delivery of immunotherapeutic anti-cancer CD8(+) T-cell vaccines into DC.

21 CFR 181.33 - Sodium nitrate and potassium nitrate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Sodium nitrate and potassium nitrate. 181.33...-Sanctioned Food Ingredients § 181.33 Sodium nitrate and potassium nitrate. Sodium nitrate and potassium... nitrite, with or without sodium or potassium nitrite, in the production of cured red meat products and...

21 CFR 181.34 - Sodium nitrite and potassium nitrite.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Sodium nitrite and potassium nitrite. 181.34...-Sanctioned Food Ingredients § 181.34 Sodium nitrite and potassium nitrite. Sodium nitrite and potassium... fixatives and preservative agents, with or without sodium or potassium nitrate, in the curing of red meat...

21 CFR 181.33 - Sodium nitrate and potassium nitrate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Sodium nitrate and potassium nitrate. 181.33...-Sanctioned Food Ingredients § 181.33 Sodium nitrate and potassium nitrate. Sodium nitrate and potassium... nitrite, with or without sodium or potassium nitrite, in the production of cured red meat products and...

21 CFR 181.34 - Sodium nitrite and potassium nitrite.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Sodium nitrite and potassium nitrite. 181.34...-Sanctioned Food Ingredients § 181.34 Sodium nitrite and potassium nitrite. Sodium nitrite and potassium... fixatives and preservative agents, with or without sodium or potassium nitrate, in the curing of red meat...

Pore-scale modeling of capillary trapping in water-wet porous media: A new cooperative pore-body filling model

NASA Astrophysics Data System (ADS)

Ruspini, L. C.; Farokhpoor, R.; Øren, P. E.

2017-10-01

We present a pore-network model study of capillary trapping in water-wet porous media. The amount and distribution of trapped non-wetting phase is determined by the competition between two trapping mechanisms - snap-off and cooperative pore-body filling. We develop a new model to describe the pore-body filling mechanism in geologically realistic pore-networks. The model accounts for the geometrical characteristics of the pore, the spatial location of the connecting throats and the local fluid topology at the time of the displacement. We validate the model by comparing computed capillary trapping curves with published data for four different water-wet rocks. Computations are performed on pore-networks extracted from micro-CT images and process-based reconstructions of the actual rocks used in the experiments. Compared with commonly used stochastic models, the new model describes more accurately the experimental measurements, especially for well connected porous systems where trapping is controlled by subtleties of the pore structure. The new model successfully predicts relative permeabilities and residual saturation for Bentheimer sandstone using in-situ measured contact angles as input to the simulations. The simulated trapped cluster size distributions are compared with predictions from percolation theory.

Recent advances in distal tubular potassium handling

PubMed Central

Rodan, Aylin R.; Cheng, Chih-Jen

2011-01-01

It is well known that sodium reabsorption and aldosterone play important roles in potassium secretion by the aldosterone-sensitive distal nephron. Sodium- and aldosterone-independent mechanisms also exist. This review focuses on some recent studies that provide novel insights into the sodium- and aldosterone-independent potassium secretion by the aldosterone-sensitive distal nephron. In addition, we discuss a study reporting on the regulation of the mammalian potassium kidney channel ROMK by intracellular and extracellular magnesium, which may be important in the pathogenesis of persistent hypokalemia in patients with concomitant potassium and magnesium deficiency. We also discuss outstanding questions and propose working models for future investigation. PMID:21270092

47 CFR 69.129 - Signalling for tandem switching.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 3 2011-10-01 2011-10-01 false Signalling for tandem switching. 69.129 Section... (CONTINUED) ACCESS CHARGES Computation of Charges § 69.129 Signalling for tandem switching. A charge that is... provision of signalling for tandem switching. [59 FR 32930, June 27, 1994] ...

47 CFR 69.129 - Signalling for tandem switching.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 3 2010-10-01 2010-10-01 false Signalling for tandem switching. 69.129 Section... (CONTINUED) ACCESS CHARGES Computation of Charges § 69.129 Signalling for tandem switching. A charge that is... provision of signalling for tandem switching. [59 FR 32930, June 27, 1994] ...

47 CFR 69.129 - Signalling for tandem switching.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 3 2013-10-01 2013-10-01 false Signalling for tandem switching. 69.129 Section... (CONTINUED) ACCESS CHARGES Computation of Charges § 69.129 Signalling for tandem switching. A charge that is... provision of signalling for tandem switching. [59 FR 32930, June 27, 1994] ...

47 CFR 69.129 - Signalling for tandem switching.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 3 2012-10-01 2012-10-01 false Signalling for tandem switching. 69.129 Section... (CONTINUED) ACCESS CHARGES Computation of Charges § 69.129 Signalling for tandem switching. A charge that is... provision of signalling for tandem switching. [59 FR 32930, June 27, 1994] ...

Potassium Iodide

MedlinePlus

... iodide you should take or give to your child depends on your age or your child's age. If potassium iodide is taken by a ... you should take yourself or give to your child. Ask your doctor, pharmacist, or public official if ...

21 CFR 181.33 - Sodium nitrate and potassium nitrate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Sodium nitrate and potassium nitrate. 181.33... nitrate and potassium nitrate. Sodium nitrate and potassium nitrate are subject to prior sanctions issued... potassium nitrite, in the production of cured red meat products and cured poultry products. [48 FR 1705, Jan...

21 CFR 181.34 - Sodium nitrite and potassium nitrite.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Sodium nitrite and potassium nitrite. 181.34... nitrite and potassium nitrite. Sodium nitrite and potassium nitrite are subject to prior sanctions issued... without sodium or potassium nitrate, in the curing of red meat and poultry products. [48 FR 1705, Jan. 14...

Cavitation and pore blocking in nanoporous glasses.

PubMed

Reichenbach, C; Kalies, G; Enke, D; Klank, D

2011-09-06

In gas adsorption studies, porous glasses are frequently referred to as model materials for highly disordered mesopore systems. Numerous works suggest that an accurate interpretation of physisorption isotherms requires a complete understanding of network effects upon adsorption and desorption, respectively. The present article deals with nitrogen and argon adsorption at different temperatures (77 and 87 K) performed on a series of novel nanoporous glasses (NPG) with different mean pore widths. NPG samples contain smaller mesopores and significantly higher microporosity than porous Vycor glass or controlled pore glass. Since the mean pore width of NPG can be tuned sensitively, the evolution of adsorption characteristics with respect to a broadening pore network can be investigated starting from the narrowest nanopore width. With an increasing mean pore width, a H2-type hysteresis develops gradually which finally transforms into a H1-type. In this connection, a transition from a cavitation-induced desorption toward desorption controlled by pore blocking can be observed. Furthermore, we find concrete hints for a pore size dependence of the relative pressure of cavitation in highly disordered pore systems. By comparing nitrogen and argon adsorption, a comprehensive insight into adsorption mechanisms in novel disordered materials is provided. © 2011 American Chemical Society

40 CFR 721.10021 - Magnesium potassium titanium oxide.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Magnesium potassium titanium oxide... Specific Chemical Substances § 721.10021 Magnesium potassium titanium oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as magnesium potassium...

40 CFR 721.10021 - Magnesium potassium titanium oxide.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Magnesium potassium titanium oxide... Specific Chemical Substances § 721.10021 Magnesium potassium titanium oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as magnesium potassium...

40 CFR 721.10021 - Magnesium potassium titanium oxide.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Magnesium potassium titanium oxide... Specific Chemical Substances § 721.10021 Magnesium potassium titanium oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as magnesium potassium...

40 CFR 721.10021 - Magnesium potassium titanium oxide.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Magnesium potassium titanium oxide... Specific Chemical Substances § 721.10021 Magnesium potassium titanium oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as magnesium potassium...

Dietary potassium regulates vascular calcification and arterial stiffness

PubMed Central

Sun, Yong; Byon, Chang Hyun; Yang, Youfeng; Bradley, Wayne E.; Dell’Italia, Louis J.; Agarwal, Anupam; Wu, Hui

2017-01-01

Vascular calcification is a risk factor that predicts adverse cardiovascular complications of several diseases including atherosclerosis. Reduced dietary potassium intake has been linked to cardiovascular diseases such as hypertension and incidental stroke, although the underlying molecular mechanisms remain largely unknown. Using the ApoE-deficient mouse model, we demonstrated for the first time to our knowledge that reduced dietary potassium (0.3%) promoted atherosclerotic vascular calcification and increased aortic stiffness, compared with normal (0.7%) potassium–fed mice. In contrast, increased dietary potassium (2.1%) attenuated vascular calcification and aortic stiffness. Mechanistically, reduction in the potassium concentration to the lower limit of the physiological range increased intracellular calcium, which activated a cAMP response element–binding protein (CREB) signal that subsequently enhanced autophagy and promoted vascular smooth muscle cell (VSMC) calcification. Inhibition of calcium signals and knockdown of either CREB or ATG7, an autophagy regulator, attenuated VSMC calcification induced by low potassium. Consistently, elevated autophagy and CREB signaling were demonstrated in the calcified arteries from low potassium diet–fed mice as well as aortic arteries exposed to low potassium ex vivo. These studies established a potentially novel causative role of dietary potassium intake in regulating atherosclerotic vascular calcification and stiffness, and uncovered mechanisms that offer opportunities to develop therapeutic strategies to control vascular disease. PMID:28978809

The relationship between uric acid and potassium in normal subjects.

PubMed Central

Kennedy, A C; Boddy, K; King, P C; Brennan, J; Anderson, J A; Buchanan, W W

1978-01-01

The serum uric acid concentration in normal healthy subjects has been studied in relation to sex, height, weight, lean body mass measured from total body potassium and predicted from the Hume-Weyers formula (1971), total body potassium, plasma potassium and urea, and packed cell volume. The strongest correlation was found with sex, but height, weight, total body potassium, lean body mass (measured and predicted) also correlated significantly with serum uric acid concentration. However, when the sex variable was removed, the other factors lost their significant correlation. Finally, total red blood cell and plasma volumes were predicted (Hume and Goldberg, 1964) and from these an estimate of total plasma uric acid, total plasma potassium, and total red blood cell potassium obtained. Measured total body potassium was found to correlate well with total plasma potassium and total red blood cell potassium independent of sex. Total plasma uric acid correlated well with measured total body potassium when both sexes were considered and when separated into male and female groups the males retained a significant correlation as did the female group. PMID:686865

The role of dietary potassium in hypertension and diabetes.

PubMed

Ekmekcioglu, Cem; Elmadfa, Ibrahim; Meyer, Alexa L; Moeslinger, Thomas

2016-03-01

Potassium is an essential mineral which plays major roles for the resting membrane potential and the intracellular osmolarity. In addition, for several years, it has been known that potassium also affects endothelial and vascular smooth muscle functions and it has been repeatedly shown that an increase in potassium intake shifts blood pressure to a more preferable level. Meanwhile, the blood pressure lowering effects of potassium were presented in several intervention trials and summarized in a handful of meta-analyses. Furthermore, accumulating epidemiological evidence from, especially, the last decade relates low dietary potassium intake or serum potassium levels to an increased risk for insulin resistance or diabetes. However, intervention trials are required to confirm this association. So, in addition to reduction of sodium intake, increasing dietary potassium intake may positively affect blood pressure and possibly also glucose metabolism in many populations. This concise review not only summarizes the studies linking potassium to blood pressure and diabetes but also discusses potential mechanisms involved, like vascular smooth muscle relaxation and endothelium-dependent vasodilation or stimulation of insulin secretion in pancreatic β-cells, respectively.

Interaction of KCNE subunits with the KCNQ1 K+ channel pore

PubMed Central

Panaghie, Gianina; Tai, Kwok-Keung; Abbott, Geoffrey W

2006-01-01

KCNQ1 α subunits form functionally distinct potassium channels by coassembling with KCNE ancillary subunits MinK and MiRP2. MinK-KCNQ1 channels generate the slowly activating, voltage-dependent cardiac IKs current. MiRP2-KCNQ1 channels form a constitutively active current in the colon. The structural basis for these contrasting channel properties, and the mechanisms of α subunit modulation by KCNE subunits, are not fully understood. Here, scanning mutagenesis located a tryptophan-tolerant region at positions 338–340 within the KCNQ1 pore-lining S6 domain, suggesting an exposed region possibly amenable to interaction with transmembrane ancillary subunits. This hypothesis was tested using concomitant mutagenesis in KCNQ1 and in the membrane-localized ‘activation triplet’ regions of MinK and MiRP2 to identify pairs of residues that interact to control KCNQ1 activation. Three pairs of mutations exerted dramatic effects, ablating channel function or either removing or restoring control of KCNQ1 activation. The results place KCNE subunits close to the KCNQ1 pore, indicating interaction of MiRP2-72 with KCNQ1-338; and MinK-59,58 with KCNQ1-339, 340. These data are consistent either with perturbation of the S6 domain by MinK or MiRP2, dissimilar positioning of MinK and MiRP2 within the channel complex, or both. Further, the results suggest specifically that two of the interactions, MiRP2-72/KCNQ1-338 and MinK-58/KCNQ1-340, are required for the contrasting gating effects of MinK and MiRP2. PMID:16308347

Pore surface engineering in covalent organic frameworks.

PubMed

Nagai, Atsushi; Guo, Zhaoqi; Feng, Xiao; Jin, Shangbin; Chen, Xiong; Ding, Xuesong; Jiang, Donglin

2011-11-15

Covalent organic frameworks (COFs) are a class of important porous materials that allow atomically precise integration of building blocks to achieve pre-designable pore size and geometry; however, pore surface engineering in COFs remains challenging. Here we introduce pore surface engineering to COF chemistry, which allows the controlled functionalization of COF pore walls with organic groups. This functionalization is made possible by the use of azide-appended building blocks for the synthesis of COFs with walls to which a designable content of azide units is anchored. The azide units can then undergo a quantitative click reaction with alkynes to produce pore surfaces with desired groups and preferred densities. The diversity of click reactions performed shows that the protocol is compatible with the development of various specific surfaces in COFs. Therefore, this methodology constitutes a step in the pore surface engineering of COFs to realize pre-designed compositions, components and functions.

40 CFR 721.10031 - Lithium potassium titanium oxide.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Lithium potassium titanium oxide. 721... Substances § 721.10031 Lithium potassium titanium oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as lithium potassium titanium oxide (PMN P-02...

40 CFR 721.10031 - Lithium potassium titanium oxide.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Lithium potassium titanium oxide. 721... Substances § 721.10031 Lithium potassium titanium oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as lithium potassium titanium oxide (PMN P-02...

40 CFR 721.10031 - Lithium potassium titanium oxide.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Lithium potassium titanium oxide. 721... Substances § 721.10031 Lithium potassium titanium oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as lithium potassium titanium oxide (PMN P-02...

40 CFR 721.10031 - Lithium potassium titanium oxide.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Lithium potassium titanium oxide. 721... Substances § 721.10031 Lithium potassium titanium oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as lithium potassium titanium oxide (PMN P-02...

40 CFR 721.10031 - Lithium potassium titanium oxide.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Lithium potassium titanium oxide. 721... Substances § 721.10031 Lithium potassium titanium oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as lithium potassium titanium oxide (PMN P-02...

Aromatic–aromatic interactions between residues in KCa3.1 pore helix and S5 transmembrane segment control the channel gating process

PubMed Central

Garneau, Line; Klein, Hélène; Lavoie, Marie-France; Brochiero, Emmanuelle; Parent, Lucie

2014-01-01

The Ca2+-activated potassium channel KCa3.1 is emerging as a therapeutic target for a large variety of health disorders. One distinguishing feature of KCa3.1 is that the channel open probability at saturating Ca2+ concentrations (Pomax) is low, typically 0.1–0.2 for KCa3.1 wild type. This observation argues for the binding of Ca2+ to the calmodulin (CaM)–KCa3.1 complex, promoting the formation of a preopen closed-state configuration leading to channel opening. We have previously shown that the KCa3.1 active gate is most likely located at the level of the selectivity filter. As Ca2+-dependent gating of KCa3.1 originates from the binding of Ca2+ to CaM in the C terminus, the hypothesis of a gate located at the level of the selectivity filter requires that the conformational change initiated in the C terminus be transmitted to the S5 and S6 transmembrane helices, with a resulting effect on the channel pore helix directly connected to the selectivity filter. A study was thus undertaken to determine to what extent the interactions between the channel pore helix with the S5 and S6 transmembrane segments contribute to KCa3.1 gating. Molecular dynamics simulations first revealed that the largest contact area between the pore helix and the S5 plus S6 transmembrane helices involves residue F248 at the C-terminal end of the pore helix. Unitary current recordings next confirmed that modulating aromatic–aromatic interactions between F248 and W216 of the S5 transmembrane helical segment and/or perturbing the interactions between F248 and residues in S6 surrounding the glycine hinge G274 cause important changes in Pomax. This work thus provides the first evidence for a key contribution of the pore helix in setting Pomax by stabilizing the channel closed configuration through aromatic–aromatic interactions involving F248 of the pore helix. We propose that the interface pore helix/S5 constitutes a promising site for designing KCa3.1 potentiators. PMID:24470490

21 CFR 172.375 - Potassium iodide.

Code of Federal Regulations, 2010 CFR

2010-04-01

... Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Special Dietary and Nutritional Additives § 172.375 Potassium iodide. The food additive potassium iodide may be...

Reversible Self-Actuated Thermo-Responsive Pore Membrane

PubMed Central

Park, Younggeun; Gutierrez, Maria Paz; Lee, Luke P.

2016-01-01

Smart membranes, which can selectively control the transfer of light, air, humidity and temperature, are important to achieve indoor climate regulation. Even though reversible self-actuation of smart membranes is desirable in large-scale, reversible self-regulation remains challenging. Specifically, reversible 100% opening/closing of pore actuation showing accurate responsiveness, reproducibility and structural flexibility, including uniform structure assembly, is currently very difficult. Here, we report a reversible, thermo-responsive self-activated pore membrane that achieves opening and closing of pores. The reversible, self-actuated thermo-responsive pore membrane was fabricated with hybrid materials of poly (N-isopropylacrylamide), (PNIPAM) within polytetrafluoroethylene (PTFE) to form a multi-dimensional pore array. Using Multiphysics simulation of heat transfer and structural mechanics based on finite element analysis, we demonstrated that pore opening and closing dynamics can be self-activated at environmentally relevant temperatures. Temperature cycle characterizations of the pore structure revealed 100% opening ratio at T = 40 °C and 0% opening ratio at T = 20 °C. The flexibility of the membrane showed an accurate temperature-responsive function at a maximum bending angle of 45°. Addressing the importance of self-regulation, this reversible self-actuated thermo-responsive pore membrane will advance the development of future large-scale smart membranes needed for sustainable indoor climate control. PMID:27991563

Reversible Self-Actuated Thermo-Responsive Pore Membrane

NASA Astrophysics Data System (ADS)

Park, Younggeun; Gutierrez, Maria Paz; Lee, Luke P.

2016-12-01

Smart membranes, which can selectively control the transfer of light, air, humidity and temperature, are important to achieve indoor climate regulation. Even though reversible self-actuation of smart membranes is desirable in large-scale, reversible self-regulation remains challenging. Specifically, reversible 100% opening/closing of pore actuation showing accurate responsiveness, reproducibility and structural flexibility, including uniform structure assembly, is currently very difficult. Here, we report a reversible, thermo-responsive self-activated pore membrane that achieves opening and closing of pores. The reversible, self-actuated thermo-responsive pore membrane was fabricated with hybrid materials of poly (N-isopropylacrylamide), (PNIPAM) within polytetrafluoroethylene (PTFE) to form a multi-dimensional pore array. Using Multiphysics simulation of heat transfer and structural mechanics based on finite element analysis, we demonstrated that pore opening and closing dynamics can be self-activated at environmentally relevant temperatures. Temperature cycle characterizations of the pore structure revealed 100% opening ratio at T = 40 °C and 0% opening ratio at T = 20 °C. The flexibility of the membrane showed an accurate temperature-responsive function at a maximum bending angle of 45°. Addressing the importance of self-regulation, this reversible self-actuated thermo-responsive pore membrane will advance the development of future large-scale smart membranes needed for sustainable indoor climate control.

Benefit and risk assessment of increasing potassium intake by replacement of sodium chloride with potassium chloride in industrial food products in Norway.

PubMed

Steffensen, Inger-Lise; Frølich, Wenche; Dahl, Knut Helkås; Iversen, Per Ole; Lyche, Jan Ludvig; Lillegaard, Inger Therese Laugsand; Alexander, Jan

2018-01-01

High sodium chloride (NaCl) intake is associated with health risks. NaCl may be replaced by potassium chloride (KCl) to decrease sodium intake. However, increased potassium may also have negative health effects. We conducted a benefit and risk assessment of increasing potassium by ratios of 30:70, 50:50, 70:30 (weight % K + : weight % Na + ) in children, adolescents and adults in Norway, using intake data from national food consumption surveys and available literature on potassium health effects. An intake of at least 3.5 g/day of potassium decreases risk of stroke and hypertension, and this level was used in the benefit assessment of the healthy population. Three g/day of potassium added to mean food intake is assumed safe, and these levels were used in the risk assessment. Not all persons reached the protective level of potassium, and increasing numbers exceeded the safe levels, in these scenarios. In addition, elderly above 85 years and infants below one year of age, as well as several patient groups and medication users, are particularly vulnerable to hyperkalemia. In conclusion, the number of Norwegians facing increased risk is far greater than the number likely to benefit from this replacement of sodium with potassium in industrially produced food. Copyright © 2017 Elsevier Ltd. All rights reserved.

Lack of genotoxicity of potassium iodate in the alkaline comet assay and in the cytokinesis-block micronucleus test. Comparison to potassium bromate.

PubMed

Poul, J M; Huet, S; Godard, T; Sanders, P

2004-02-01

Iodine could be added to the diet of human population in the form of iodide or iodate but iodate had not been adequately tested for genotoxicity and carcinogenicity. In the present study, genotoxic effects of potassium iodate were evaluated in vitro using the alkaline comet assay and the cytokinesis-block micronucleus assay on CHO cells and compared to halogenate salt analogues potassium bromate and chlorate and also to their respective reduced forms (potassium iodide, bromide and chloride). The results showed that the comet assay failed to detect the presence of DNA damage after a treatment of cells by potassium iodate for concentrations up to 10 mM. This absence of primary DNA damage was confirmed in the cytokinesis-block micronucleus assay. In the same way, results showed that potassium chlorate as well as potassium iodide, bromide and chloride did not induced DNA damage in the alkaline comet assay for doses up to 10 mM. By contrast, potassium bromate exposure led to an increase in both DNA damage and frequency of micronucleated cells. The repair of bromate-induced DNA damage was incomplete 24 h after the end of treatment. These results seem to indicate that potassium bromate would induce DNA damage by several mechanisms besides oxidative stress.

21 CFR 582.5634 - Potassium iodide.

Code of Federal Regulations, 2011 CFR

2011-04-01

... DRUGS, FEEDS, AND RELATED PRODUCTS SUBSTANCES GENERALLY RECOGNIZED AS SAFE Nutrients and/or Dietary Supplements 1 § 582.5634 Potassium iodide. (a) Product. Potassium iodide. (b) Tolerance. 0.01 percent. (c... salt as a source of dietary iodine in accordance with good manufacturing or feeding practice. ...

21 CFR 582.5634 - Potassium iodide.

Code of Federal Regulations, 2013 CFR

2013-04-01

... DRUGS, FEEDS, AND RELATED PRODUCTS SUBSTANCES GENERALLY RECOGNIZED AS SAFE Nutrients and/or Dietary Supplements 1 § 582.5634 Potassium iodide. (a) Product. Potassium iodide. (b) Tolerance. 0.01 percent. (c... salt as a source of dietary iodine in accordance with good manufacturing or feeding practice. ...

21 CFR 582.5634 - Potassium iodide.

Code of Federal Regulations, 2010 CFR

2010-04-01

... DRUGS, FEEDS, AND RELATED PRODUCTS SUBSTANCES GENERALLY RECOGNIZED AS SAFE Nutrients and/or Dietary Supplements 1 § 582.5634 Potassium iodide. (a) Product. Potassium iodide. (b) Tolerance. 0.01 percent. (c... salt as a source of dietary iodine in accordance with good manufacturing or feeding practice. ...

21 CFR 172.375 - Potassium iodide.

Code of Federal Regulations, 2014 CFR

2014-04-01

... Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Special Dietary and Nutritional Additives § 172.375 Potassium iodide. The food additive potassium iodide may be safely used in accordance with the...

Multimegawatt potassium Rankine power for nuclear electric power

NASA Technical Reports Server (NTRS)

Rovang, Richard D.; Mills, Joseph C.; Baumeister, Ernie B.

1991-01-01

A cermet fueled potassium rankine power system concept has been developed for various power ranges and operating lifetimes. This concept utilizes a single primary lithium loop to transport thermal energy from the reactor to the boiler. Multiple, independent potassium loops are employed to achieve the required reliability of 99 percent. The potassium loops are two phase systems which expand heated potassium vapor through multistage turboalternators to produce a 10-kV dc electrical output. Condensation occurs by-way-of a shear-flow condenser, producing a 100 percent liquid potassium stream which is pumped back to the boiler. Waste heat is rejected by an advanced carbon-carbon radiator at approximately 1000 K. Overall system efficiencies of 19.3 percent to 20.5 percent were calculated depending on mission life and power level.

Modeling the interaction of ultrasound with pores

NASA Technical Reports Server (NTRS)

Lu, Yichi; Wadley, Haydn N. G.; Parthasarathi, Sanjai

1991-01-01

Factors that affect ultrasonic velocity sensing of density during consolidation of metal powders are examined. A comparison is made between experimental results obtained during the final stage of densification and the predictions of models that assume either a spherical or a spheroidal pore shape. It is found that for measurements made at low frequencies during the final stage of densification, relative density (pore fraction) and pore shape are the two most important factors determining the ultrasonic velocity, the effect of pore size is negligible.

Tandem Translation Classroom: A Case Study

ERIC Educational Resources Information Center

Kim, Dohun; Koh, Taejin

2018-01-01

The transition to student-centred learning, advances in teleconferencing tools, and active international student exchange programmes have stimulated tandem learning in many parts of the world. This pedagogical model is based on a mutual language exchange between tandem partners, where each student is a native speaker in the language the…

Proton Diffusion through Bilayer Pores

DOE PAGES

McDaniel, Jesse G.; Yethiraj, Arun

2017-09-26

The transport of protons through channels in complex environments is important in biology and materials science. In this work, we use multistate empirical valence bond simulations to study proton transport within a well-defined bilayer pore in a lamellar L β phase lyotropic liquid crystal (LLC). The LLC is formed from the self-assembly of dicarboxylate gemini surfactants in water, and a bilayer-spanning pore of radius of approximately 3–5 Å results from the uneven partitioning of surfactants between the two leaflets of the lamella. Local proton diffusion within the pore is significantly faster than diffusion at the bilayer surface, which is duemore » to the greater hydrophobicity of the surfactant/water interface within the pore. Proton diffusion proceeds by surface transport along exposed hydrophobic pockets at the surfactant/water interface and depends on the continuity of hydronium–water hydrogen bond networks. At the bilayer surface, there is a reduced fraction of the “Zundel” intermediates that are central to the Grotthuss transport mechanism, whereas the fraction of these species within the bilayer pore is similar to that in bulk water. Our results demonstrate that the chemical nature of the confining interface, in addition to confinement length scale, is an important determiner of local proton transport in nanoconfined aqueous environments.« less

Structural basis of potassium activation in plant asparaginases.

PubMed

Ajewole, Ebenezer; Santamaria-Kisiel, Liliana; Pajak, Agnieszka; Jaskolski, Mariusz; Marsolais, Frédéric

2018-04-01

l-asparaginases (EC 3.5.1.1) play an important role in nitrogen mobilization in plants. Here, we investigated the biochemical and biophysical properties of potassium-dependent (PvAspG1) and potassium-independent (PvAspG-T2) l-asparaginases from Phaseolus vulgaris. Our previous studies revealed that PvAspG1 requires potassium for catalytic activation and its crystal structure suggested that Ser-118 in the activation loop plays a critical role in coordinating the metal cation. This amino acid residue is replaced by isoleucine in PvAspG-T2. Reciprocal mutants of the enzymes were produced and the effect of the amino acid substitution on the kinetic parameters, allosteric effector binding, secondary structure conformation, and pH profile were studied. Introduction of the serine residue conferred potassium activation in PvAspG-T2. Conversely, the PvAspG1-S118I mutant could no longer be activated by potassium. PvAspG1 and the PvAspG-T2-I117S mutant had a similar half-maximal effective concentration (EC 50 ) value for potassium activation, between 0.1 and 0.3 mm. Potassium binding elicited a similar conformational change in PvAspG1 and PvAspG-T2-I117S, as studied by circular dichroism. However, no change in conformation was observed for PvAspG-T2 and PvAspG1-S118I. Analysis of kinetic parameters in function of pH indicated that potassium activation mediated by Ser-118 influences the ionization of specific functional groups in the enzyme-substrate complex. Together, the results indicate that Ser-118 of PvAspG1 is essential and sufficient for potassium activation in plant l-asparaginases. ENZYME: l-Asparaginase (EC 3.5.1.1). © 2018 Federation of European Biochemical Societies.

21 CFR 582.1077 - Potassium acid tartrate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... Additives § 582.1077 Potassium acid tartrate. (a) Product. Potassium acid tartrate. (b) Conditions of use. This substance is generally recognized as safe when used in accordance with good manufacturing or...

21 CFR 582.1129 - Aluminum potassium sulfate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... Additives § 582.1129 Aluminum potassium sulfate. (a) Product. Aluminum potassium sulfate. (b) Conditions of use. This substance is generally recognized as safe when used in accordance with good manufacturing or...

21 CFR 172.730 - Potassium bromate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... HUMAN CONSUMPTION (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Other Specific Usage Additives § 172.730 Potassium bromate. The food additive potassium bromate may be... intended for use in the malting of barley under conditions whereby the amount of the additive present in...

21 CFR 172.730 - Potassium bromate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... HUMAN CONSUMPTION (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Other Specific Usage Additives § 172.730 Potassium bromate. The food additive potassium bromate may be... intended for use in the malting of barley under conditions whereby the amount of the additive present in...

21 CFR 184.1639 - Potassium lactate.

Code of Federal Regulations, 2011 CFR

2011-04-01

.... No. 996-31-6) is the potassium salt of lactic acid. It is a hydroscopic, white, odorless solid and is prepared commercially by the neutralization of lactic acid with potassium hydroxide. (b) The ingredient... current good manufacturing practice. (d) Prior sanctions for this ingredient different from the uses...

21 CFR 184.1639 - Potassium lactate.

Code of Federal Regulations, 2012 CFR

2012-04-01

.... No. 996-31-6) is the potassium salt of lactic acid. It is a hydroscopic, white, odorless solid and is prepared commercially by the neutralization of lactic acid with potassium hydroxide. (b) The ingredient... current good manufacturing practice. (d) Prior sanctions for this ingredient different from the uses...

21 CFR 184.1639 - Potassium lactate.

Code of Federal Regulations, 2013 CFR

2013-04-01

.... No. 996-31-6) is the potassium salt of lactic acid. It is a hydroscopic, white, odorless solid and is prepared commercially by the neutralization of lactic acid with potassium hydroxide. (b) The ingredient... current good manufacturing practice. (d) Prior sanctions for this ingredient different from the uses...

21 CFR 184.1639 - Potassium lactate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... potassium salt of lactic acid. It is a hydroscopic, white, odorless solid and is prepared commercially by the neutralization of lactic acid with potassium hydroxide. (b) The ingredient must be of a purity.... (d) Prior sanctions for this ingredient different from the uses established in this section do not...

21 CFR 184.1639 - Potassium lactate.

Code of Federal Regulations, 2010 CFR

2010-04-01

.... No. 996-31-6) is the potassium salt of lactic acid. It is a hydroscopic, white, odorless solid and is prepared commercially by the neutralization of lactic acid with potassium hydroxide. (b) The ingredient... current good manufacturing practice. (d) Prior sanctions for this ingredient different from the uses...

Adaptation of Bacillus subtilis to Life at Extreme Potassium Limitation.

PubMed

Gundlach, Jan; Herzberg, Christina; Hertel, Dietrich; Thürmer, Andrea; Daniel, Rolf; Link, Hannes; Stülke, Jörg

2017-07-05

Potassium is the most abundant metal ion in every living cell. This ion is essential due to its requirement for the activity of the ribosome and many enzymes but also because of its role in buffering the negative charge of nucleic acids. As the external concentrations of potassium are usually low, efficient uptake and intracellular enrichment of the ion is necessary. The Gram-positive bacterium Bacillus subtilis possesses three transporters for potassium, KtrAB, KtrCD, and the recently discovered KimA. In the absence of the high-affinity transporters KtrAB and KimA, the bacteria were unable to grow at low potassium concentrations. However, we observed the appearance of suppressor mutants that were able to overcome the potassium limitation. All these suppressor mutations affected amino acid metabolism, particularly arginine biosynthesis. In the mutants, the intracellular levels of ornithine, citrulline, and arginine were strongly increased, suggesting that these amino acids can partially substitute for potassium. This was confirmed by the observation that the supplementation with positively charged amino acids allows growth of B. subtilis even at the extreme potassium limitation that the bacteria experience if no potassium is added to the medium. In addition, a second class of suppressor mutations allowed growth at extreme potassium limitation. These mutations result in increased expression of KtrAB, the potassium transporter with the highest affinity and therefore allow the acquisition and accumulation of the smallest amounts of potassium ions from the environment. IMPORTANCE Potassium is essential for every living cell as it is required for the activity for many enzymes and for maintaining the intracellular pH by buffering the negative charge of the nucleic acids. We have studied the adaptation of the soil bacterium Bacillus subtilis to life at low potassium concentrations. If the major high-affinity transporters are missing, the bacteria are unable to grow

Potassium acceptor doping of ZnO crystals

NASA Astrophysics Data System (ADS)

Parmar, Narendra S.; Corolewski, Caleb D.; McCluskey, Matthew D.; Lynn, K. G.

2015-05-01

ZnO bulk single crystals were doped with potassium by diffusion at 950°C. Positron annihilation spectroscopy confirms the filling of zinc vacancies and a different trapping center for positrons. Secondary ion mass spectroscopy measurements show the diffusion of potassium up to 10 μm with concentration ˜1 × 1016 cm-3. IR measurements show a local vibrational mode (LVM) at 3226 cm-1, at a temperature of 9 K, in a potassium doped sample that was subsequently hydrogenated. The LVM is attributed to an O-H bond-stretching mode adjacent to a potassium acceptor. When deuterium substitutes for hydrogen, a peak is observed at 2378 cm-1. The O-H peak is much broader than the O-D peak, perhaps due to an unusually low vibrational lifetime. The isotopic frequency ratio is similar to values found in other hydrogen complexes. Potassium doping increases the resistivity up to 3 orders of magnitude at room temperature. The doped sample has a donor level at 0.30 eV.

Potassium acceptor doping of ZnO crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parmar, Narendra S., E-mail: nparmar@wsu.edu; Lynn, K. G.; Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164-2814

2015-05-15

ZnO bulk single crystals were doped with potassium by diffusion at 950°C. Positron annihilation spectroscopy confirms the filling of zinc vacancies and a different trapping center for positrons. Secondary ion mass spectroscopy measurements show the diffusion of potassium up to 10 μm with concentration ∼1 × 10{sup 16} cm{sup −3}. IR measurements show a local vibrational mode (LVM) at 3226 cm{sup −1}, at a temperature of 9 K, in a potassium doped sample that was subsequently hydrogenated. The LVM is attributed to an O–H bond-stretching mode adjacent to a potassium acceptor. When deuterium substitutes for hydrogen, a peak is observedmore » at 2378 cm{sup −1}. The O-H peak is much broader than the O-D peak, perhaps due to an unusually low vibrational lifetime. The isotopic frequency ratio is similar to values found in other hydrogen complexes. Potassium doping increases the resistivity up to 3 orders of magnitude at room temperature. The doped sample has a donor level at 0.30 eV.« less

Performance of Small Pore Microchannel Plates

NASA Technical Reports Server (NTRS)

Siegmund, O. H. W.; Gummin, M. A.; Ravinett, T.; Jelinsky, S. R.; Edgar, M.

1995-01-01

Small pore size microchannel plates (MCP's) are needed to satisfy the requirements for future high resolution small and large format detectors for astronomy. MCP's with pore sizes in the range 5 micron to 8 micron are now being manufactured, but they are of limited availability and are of small size. We have obtained sets of Galileo 8 micron and 6.5 micron MCP's, and Philips 6 micron and 7 micron pore MCP's, and compared them to our larger pore MCP Z stacks. We have tested back to back MCP stacks of four of these MCP's and achieved gains greater than 2 x 1O(exp 7) with pulse height distributions of less than 40% FWHM, and background rates of less than 0.3 events sec(exp -1) cm(exp -2). Local counting rates up to approx. 100 events/pore/sec have been attained with little drop of the MCP gain. The bare MCP quantum efficiencies are somewhat lower than those expected, however. Flat field images are characterized by an absence of MCP fixed pattern noise.

Diagnostic value of potassium level in a spot urine sample as an index of 24-hour urinary potassium excretion in unselected patients hospitalized in a hypertension unit

PubMed Central

Symonides, Bartosz; Wojciechowska, Ewa; Gryglas, Adam; Gaciong, Zbigniew

2017-01-01

Background Primary hyperaldosteronism may be associated with elevated 24-hour urinary potassium excretion. We evaluated the diagnostic value of spot urine (SU) potassium as an index of 24-hour urinary potassium excretion. Methods We measured SU and 24-hour urinary collection potassium and creatinine in 382 patients. Correlations between SU and 24-hour collections were assessed for potassium levels and potassium/creatinine ratios. We used the PAHO formula to estimate 24-hour urinary potassium excretion based on SU potassium level. The agreement between estimated and measured 24-hour urinary potassium excretion was evaluated using the Bland-Altman method. To evaluate diagnostic performance of SU potassium, we calculated areas under the curve (AUC) for SU potassium/creatinine ratio and 24-hour urinary potassium excretion estimated using the PAHO formula. Results Strongest correlation between SU and 24-hour collection was found for potassium/creatinine ratio (r = 0.69, P<0.001). The PAHO formula underestimated 24-hour urinary potassium excretion by mean 8.3±18 mmol/d (95% limits of agreement -28 to +44 mmol/d). Diagnostic performance of SU potassium/creatinine ratio was borderline good only if 24-hour urinary potassium excretion was largely elevated (AUC 0.802 for 120 mmol K+/24 h) but poor with lower values (AUC 0.696 for 100 mmol K+/24 h, 0.636 for 80 mmol K+/24 h, 0.675 for 40 mmol K+/24 h). Diagnostic performance of 24-hour urinary potassium excretion estimated by the PAHO formula was excellent with values above 120 mmol/d and good with lower values (AUC 0.941 for 120 mmol K+/24 h, 0.819 for 100 mmol K+/24 h, 0.823 for 80 mmol K+/24 h, 0.836 for 40 mmol K+/24 h). Conclusions Spot urine potassium/creatinine ratio might be a marker of increased 24-hour urinary potassium excretion and a potentially useful screening test when reliable 24-hour urine collection is not available. The PAHO formula allowed estimation of the 24-hour urinary potassium excretion based on SU

Thermodynamic characterization of tandem mismatches found in naturally occurring RNA

PubMed Central

Christiansen, Martha E.; Znosko, Brent M.

2009-01-01

Although all sequence symmetric tandem mismatches and some sequence asymmetric tandem mismatches have been thermodynamically characterized and a model has been proposed to predict the stability of previously unmeasured sequence asymmetric tandem mismatches [Christiansen,M.E. and Znosko,B.M. (2008) Biochemistry, 47, 4329–4336], experimental thermodynamic data for frequently occurring tandem mismatches is lacking. Since experimental data is preferred over a predictive model, the thermodynamic parameters for 25 frequently occurring tandem mismatches were determined. These new experimental values, on average, are 1.0 kcal/mol different from the values predicted for these mismatches using the previous model. The data for the sequence asymmetric tandem mismatches reported here were then combined with the data for 72 sequence asymmetric tandem mismatches that were published previously, and the parameters used to predict the thermodynamics of previously unmeasured sequence asymmetric tandem mismatches were updated. The average absolute difference between the measured values and the values predicted using these updated parameters is 0.5 kcal/mol. This updated model improves the prediction for tandem mismatches that were predicted rather poorly by the previous model. This new experimental data and updated predictive model allow for more accurate calculations of the free energy of RNA duplexes containing tandem mismatches, and, furthermore, should allow for improved prediction of secondary structure from sequence. PMID:19509311

A Simplified Extemporaneously Prepared Potassium Chloride Oral Solution.

PubMed

Tannous, Elias; Tal, Yana; Amarny, Kamal

2016-01-01

Although commercial preparations of oral potassium supplements are usually available, there are times when our Medical Center is faced with situations in which the oral solution of potassium chloride is not available. This solution is necessary for our pediatric outpatients who cannot swallow tablets and need an oral solution. Moreover, there are no studies available which describe an extemporaneously prepared potassium chloride oral solution on which we can rely for assigning a beyond-use date. The aim of this study was to formulate an extemporaneous pediatric oral solution of potassium chloride and to determine the physical and chemical stability of this preparation. We prepared 1 mMoL/mL by withdrawing 25 mL of potassium chloride 14.9%. Ora-Sweet SF was added to 50 mL in a metered flask. The solution was kept refrigerated (2°C to 8°C). Samples were withdrawn to measure potassium concentration, pH, and microbial overgrowth. The test was performed by our biochemical laboratory. The oral solution of potassium chloride 1 mMoL/mL stored at 2°C to 8°C maintained at least 91% of the initial concentration for 28 days. There were no notable changes in pH, and the solution remained physically stable with no visual microbial growth. The oral solution of potassium chloride 1 mMoL/mL prepared in Ora-Sweet and stored at 2°C to 8°C in amber glass bottles is expected to remain stable for 28 days. Copyright© by International Journal of Pharmaceutical Compounding, Inc.

Implementation of a timed, electronic, assessment-driven potassium-replacement protocol.

PubMed

Zielenski, Christopher; Crabtree, Adam; Le, Tien; Marlatt, Alyse; Ng, Dana; Tran, Alan

2017-06-15

The adherence to and effectiveness and safety of a timed, electronic, assessment-driven potassium-replacement protocol (TARP) were compared with an electronic nurse-driven replacement protocol (NRP) are reported. A retrospective observational study was conducted in a community hospital evaluating protocol adherence, effectiveness, and safety for 2 potassium-replacement protocols. All adults on medical units with an order for potassium replacement per protocol during the 3-month trial periods were reviewed. All patients requiring potassium replacement per protocol were included in the analysis. Adherence to the protocol was assessed by evaluating the dose of potassium administered and performance of reassessments. Effectiveness of the protocol was assessed by evaluating the time to achieve target potassium levels. Safety was assessed by evaluating the route of administration and occurrence of hyperkalemia. A total of 300 patients treated using potassium-replacement protocols required potassium replacement during the study period, with 148 patients in the NRP group requiring 491 instances of potassium replacement. In the TARP group a total of 564 instances requiring potassium replacement corresponded to 152 patients. Of the 491 instances requiring replacement in the NRP group, the correct dose was administered and reassessment performed 117 times (23.8%). Overall adherence ( p < 0.05), correct dose given ( p < 0.05), average time from blood draw to potassium replacement ( p < 0.0001), use of oral replacement ( p < 0.05), and time to achieve target potassium level within 12 hours ( p < 0.05) were significantly improved in the TARP group. The TARP improved the effectiveness and safety of potassium-replacement therapy over the traditional NRP without negatively affecting timeliness of care. Copyright © 2017 by the American Society of Health-System Pharmacists, Inc. All rights reserved.

21 CFR 172.375 - Potassium iodide.

Code of Federal Regulations, 2013 CFR

2013-04-01

... CONSUMPTION (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Special Dietary and Nutritional Additives § 172.375 Potassium iodide. The food additive potassium iodide may be..., will not result in daily ingestion of the additive so as to provide a total amount of iodine in excess...

21 CFR 172.375 - Potassium iodide.

Code of Federal Regulations, 2012 CFR

2012-04-01

... CONSUMPTION (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Special Dietary and Nutritional Additives § 172.375 Potassium iodide. The food additive potassium iodide may be..., will not result in daily ingestion of the additive so as to provide a total amount of iodine in excess...

21 CFR 172.730 - Potassium bromate.

Code of Federal Regulations, 2014 CFR

2014-04-01

... ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Other Specific Usage Additives § 172.730 Potassium bromate. The food additive potassium bromate may be safely used in the malting of barley... barley under conditions whereby the amount of the additive present in the malt from the treatment does...

Selecting tandem partners for silicon solar cells [Selecting tandem partners for silicon solar cells using spectral efficiency

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Zhengshan; Leilaeioun, Mehdi; Holman, Zachary

Combining silicon and other materials in tandem solar cells is one approach to enhancing the overall power conversion efficiency of the cells. Here, we argue that top cell partners for silicon tandem solar cells should be selected on the basis of their spectral efficiency — their efficiency resolved by wavelength.

Selecting tandem partners for silicon solar cells [Selecting tandem partners for silicon solar cells using spectral efficiency

DOE PAGES

Yu, Zhengshan; Leilaeioun, Mehdi; Holman, Zachary

2016-09-26

Combining silicon and other materials in tandem solar cells is one approach to enhancing the overall power conversion efficiency of the cells. Here, we argue that top cell partners for silicon tandem solar cells should be selected on the basis of their spectral efficiency — their efficiency resolved by wavelength.

Propagation of a plasma streamer in catalyst pores

NASA Astrophysics Data System (ADS)

Zhang, Quan-Zhi; Bogaerts, Annemie

2018-03-01

Although plasma catalysis is gaining increasing interest for various environmental applications, the underlying mechanisms are still far from understood. For instance, it is not yet clear whether and how plasma streamers can propagate in catalyst pores, and what is the minimum pore size to make this happen. As this is crucial information to ensure good plasma-catalyst interaction, we study here the mechanism of plasma streamer propagation in a catalyst pore, by means of a two-dimensional particle-in-cell/Monte Carlo collision model, for various pore diameters in the nm-range to μm-range. The so-called Debye length is an important criterion for plasma penetration into catalyst pores, i.e. a plasma streamer can penetrate into pores when their diameter is larger than the Debye length. The Debye length is typically in the order of a few 100 nm up to 1 μm at the conditions under study, depending on electron density and temperature in the plasma streamer. For pores in the range of ∼50 nm, plasma can thus only penetrate to some extent and at very short times, i.e. at the beginning of a micro-discharge, before the actual plasma streamer reaches the catalyst surface and a sheath is formed in front of the surface. We can make plasma streamers penetrate into smaller pores (down to ca. 500 nm at the conditions under study) by increasing the applied voltage, which yields a higher plasma density, and thus reduces the Debye length. Our simulations also reveal that the plasma streamers induce surface charging of the catalyst pore sidewalls, causing discharge enhancement inside the pore, depending on pore diameter and depth.

An emerging pore-making strategy: confined swelling-induced pore generation in block copolymer materials.

PubMed

Wang, Yong; Li, Fengbin

2011-05-17

Block copolymers (BCPs) composed of two or more thermodynamically incompatible homopolymers self-assemble into periodic microdomains. Exposing self-assembled BCPs with solvents selective to one block causes a swelling of the domains composed of this block. Strong swelling in the confinement imposed by the matrix of the other glassy block leads to well-defined porous structures via morphology reconstruction. This confined swelling-induced pore-making process has emerged recently as a new strategy to produce porous materials due to synergic advantages that include extreme simplicity, high pore regularity, involvement of no chemical reactions, no weight loss, reversibility of the pore forming process, etc. The mechanism, kinetics, morphology, and governing parameters of the confined swelling-induced pore-making process in BCP thin films are discussed, and the main applications of nanoporous thin films in the fields of template synthesis, surface patterning, and guidance for the areal arrangements of nanomaterials and biomolecules are summarized. Recent, promising results of extending this mechanism to produce BCP nanofibers or nanotubes and bulk materials with well-defined porosity, which makes this strategy also attractive to researchers outside the nanocommunity, are also presented. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Application of real rock pore-threat statistics to a regular pore network model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rakibul, M.; Sarker, H.; McIntyre, D.

2011-01-01

This work reports the application of real rock statistical data to a previously developed regular pore network model in an attempt to produce an accurate simulation tool with low computational overhead. A core plug from the St. Peter Sandstone formation in Indiana was scanned with a high resolution micro CT scanner. The pore-throat statistics of the three-dimensional reconstructed rock were extracted and the distribution of the pore-throat sizes was applied to the regular pore network model. In order to keep the equivalent model regular, only the throat area or the throat radius was varied. Ten realizations of randomly distributed throatmore » sizes were generated to simulate the drainage process and relative permeability was calculated and compared with the experimentally determined values of the original rock sample. The numerical and experimental procedures are explained in detail and the performance of the model in relation to the experimental data is discussed and analyzed. Petrophysical properties such as relative permeability are important in many applied fields such as production of petroleum fluids, enhanced oil recovery, carbon dioxide sequestration, ground water flow, etc. Relative permeability data are used for a wide range of conventional reservoir engineering calculations and in numerical reservoir simulation. Two-phase oil water relative permeability data are generated on the same core plug from both pore network model and experimental procedure. The shape and size of the relative permeability curves were compared and analyzed and good match has been observed for wetting phase relative permeability but for non-wetting phase, simulation results were found to be deviated from the experimental ones. Efforts to determine petrophysical properties of rocks using numerical techniques are to eliminate the necessity of regular core analysis, which can be time consuming and expensive. So a numerical technique is expected to be fast and to produce reliable

Application of real rock pore-throat statistics to a regular pore network model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarker, M.R.; McIntyre, D.; Ferer, M.

2011-01-01

This work reports the application of real rock statistical data to a previously developed regular pore network model in an attempt to produce an accurate simulation tool with low computational overhead. A core plug from the St. Peter Sandstone formation in Indiana was scanned with a high resolution micro CT scanner. The pore-throat statistics of the three-dimensional reconstructed rock were extracted and the distribution of the pore-throat sizes was applied to the regular pore network model. In order to keep the equivalent model regular, only the throat area or the throat radius was varied. Ten realizations of randomly distributed throatmore » sizes were generated to simulate the drainage process and relative permeability was calculated and compared with the experimentally determined values of the original rock sample. The numerical and experimental procedures are explained in detail and the performance of the model in relation to the experimental data is discussed and analyzed. Petrophysical properties such as relative permeability are important in many applied fields such as production of petroleum fluids, enhanced oil recovery, carbon dioxide sequestration, ground water flow, etc. Relative permeability data are used for a wide range of conventional reservoir engineering calculations and in numerical reservoir simulation. Two-phase oil water relative permeability data are generated on the same core plug from both pore network model and experimental procedure. The shape and size of the relative permeability curves were compared and analyzed and good match has been observed for wetting phase relative permeability but for non-wetting phase, simulation results were found to be deviated from the experimental ones. Efforts to determine petrophysical properties of rocks using numerical techniques are to eliminate the necessity of regular core analysis, which can be time consuming and expensive. So a numerical technique is expected to be fast and to produce reliable

Effects of protein-protein interactions and ligand binding on the ion permeation in KCNQ1 potassium channel.

PubMed

Jalily Hasani, Horia; Ganesan, Aravindhan; Ahmed, Marawan; Barakat, Khaled H

2018-01-01

The voltage-gated KCNQ1 potassium ion channel interacts with the type I transmembrane protein minK (KCNE1) to generate the slow delayed rectifier (IKs) current in the heart. Mutations in these transmembrane proteins have been linked with several heart-related issues, including long QT syndromes (LQTS), congenital atrial fibrillation, and short QT syndrome. Off-target interactions of several drugs with that of KCNQ1/KCNE1 ion channel complex have been known to cause fatal cardiac irregularities. Thus, KCNQ1/KCNE1 remains an important avenue for drug-design and discovery research. In this work, we present the structural and mechanistic details of potassium ion permeation through an open KCNQ1 structural model using the combined molecular dynamics and steered molecular dynamics simulations. We discuss the processes and key residues involved in the permeation of a potassium ion through the KCNQ1 ion channel, and how the ion permeation is affected by (i) the KCNQ1-KCNE1 interactions and (ii) the binding of chromanol 293B ligand and its derivatives into the complex. The results reveal that interactions between KCNQ1 with KCNE1 causes a pore constriction in the former, which in-turn forms small energetic barriers in the ion-permeation pathway. These findings correlate with the previous experimental reports that interactions of KCNE1 dramatically slows the activation of KCNQ1. Upon ligand-binding onto the complex, the energy-barriers along ion permeation path are more pronounced, as expected, therefore, requiring higher force in our steered-MD simulations. Nevertheless, pulling the ion when a weak blocker is bound to the channel does not necessitate high force in SMD. This indicates that our SMD simulations have been able to discern between strong and week blockers and reveal their influence on potassium ion permeation. The findings presented here will have some implications in understanding the potential off-target interactions of the drugs with the KCNQ1/KCNE1 channel

Tandem junction amorphous silicon solar cells

DOEpatents

Hanak, Joseph J.

1981-01-01

An amorphous silicon solar cell has an active body with two or a series of layers of hydrogenated amorphous silicon arranged in a tandem stacked configuration with one optical path and electrically interconnected by a tunnel junction. The layers of hydrogenated amorphous silicon arranged in tandem configuration can have the same bandgap or differing bandgaps.

Quantifying similarity of pore-geometry in nanoporous materials

DOE PAGES

Lee, Yongjin; Barthel, Senja D.; Dłotko, Paweł; ...

2017-05-23

In most applications of nanoporous materials the pore structure is as important as the chemical composition as a determinant of performance. For example, one can alter performance in applications like carbon capture or methane storage by orders of magnitude by only modifying the pore structure. For these applications it is therefore important to identify the optimal pore geometry and use this information to find similar materials. But, the mathematical language and tools to identify materials with similar pore structures, but different composition, has been lacking. We develop a pore recognition approach to quantify similarity of pore structures and classify themmore » using topological data analysis. This then allows us to identify materials with similar pore geometries, and to screen for materials that are similar to given top-performing structures. Using methane storage as a case study, we also show that materials can be divided into topologically distinct classes requiring different optimization strategies.« less

40 CFR 721.5970 - Phosphated polyarylphenol ethoxylate, potassium salt.

Code of Federal Regulations, 2012 CFR

2012-07-01

..., potassium salt. 721.5970 Section 721.5970 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.5970 Phosphated polyarylphenol ethoxylate, potassium salt. (a) Chemical... as phosphated polyarylphenol ethoxylate, potassium salt (PMN P-93-1222) is subject to reporting under...

40 CFR 721.5970 - Phosphated polyarylphenol ethoxylate, potassium salt.

Code of Federal Regulations, 2013 CFR

2013-07-01

..., potassium salt. 721.5970 Section 721.5970 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.5970 Phosphated polyarylphenol ethoxylate, potassium salt. (a) Chemical... as phosphated polyarylphenol ethoxylate, potassium salt (PMN P-93-1222) is subject to reporting under...

40 CFR 721.5970 - Phosphated polyarylphenol ethoxylate, potassium salt.

Code of Federal Regulations, 2010 CFR

2010-07-01

..., potassium salt. 721.5970 Section 721.5970 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.5970 Phosphated polyarylphenol ethoxylate, potassium salt. (a) Chemical... as phosphated polyarylphenol ethoxylate, potassium salt (PMN P-93-1222) is subject to reporting under...

40 CFR 721.5970 - Phosphated polyarylphenol ethoxylate, potassium salt.

Code of Federal Regulations, 2011 CFR

2011-07-01

..., potassium salt. 721.5970 Section 721.5970 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.5970 Phosphated polyarylphenol ethoxylate, potassium salt. (a) Chemical... as phosphated polyarylphenol ethoxylate, potassium salt (PMN P-93-1222) is subject to reporting under...

40 CFR 721.5970 - Phosphated polyarylphenol ethoxylate, potassium salt.

Code of Federal Regulations, 2014 CFR

2014-07-01

..., potassium salt. 721.5970 Section 721.5970 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.5970 Phosphated polyarylphenol ethoxylate, potassium salt. (a) Chemical... as phosphated polyarylphenol ethoxylate, potassium salt (PMN P-93-1222) is subject to reporting under...

Multiscale Pores in TBCs for Lower Thermal Conductivity

NASA Astrophysics Data System (ADS)

Zhang, Wei-Wei; Li, Guang-Rong; Zhang, Qiang; Yang, Guan-Jun

2017-08-01

The morphology and pattern (including orientation and aspect ratio) of pores in thermal barrier coatings (TBCs) significantly affect their thermal insulation performance. In this work, finite element analysis was used to comprehensively understand the thermal insulation effect of pores and correlate the effective thermal conductivity with the structure. The results indicated that intersplat pores, and in particular their aspect ratio, dominantly affect the heat transfer in the top coat. The effective thermal conductivity decreased as a function of aspect ratio, since a larger aspect ratio often corresponds to a greater proportion of effective length of the pores. However, in conventional plasma-sprayed TBCs, intersplat pores often fail to maximize thermal insulation due to their distinct lower aspect ratios. Therefore, considering this effect of aspect ratio, a new structure design with multiscale pores is proposed and a corresponding structural model developed to correlate the thermal properties with this pore-rich structure. The predictions of the model are well consistent with experimental data. This study provides comprehensive understanding of the effect of pores on the thermal insulation performance, shedding light on the possibility of structural tailoring to obtain advanced TBCs with lower thermal conductivity.

Tortuous Pore Path Through the Glaucomatous Lamina Cribrosa.

PubMed

Wang, Bo; Lucy, Katie A; Schuman, Joel S; Sigal, Ian A; Bilonick, Richard A; Lu, Chen; Liu, Jonathan; Grulkowski, Ireneusz; Nadler, Zachary; Ishikawa, Hiroshi; Kagemann, Larry; Fujimoto, James G; Wollstein, Gadi

2018-05-08

The lamina cribrosa is a primary site of damage in glaucoma. While mechanical distortion is hypothesized to cause reduction of axoplasmic flow, little is known about how the pores, which contains the retinal ganglion cell axons, traverse the lamina cribrosa. We investigated lamina cribrosa pore paths in vivo to quantify differences in tortuosity of pore paths between healthy and glaucomatous eyes. We imaged 16 healthy, 23 glaucoma suspect and 48 glaucomatous eyes from 70 subjects using a swept source optical coherence tomography system. The lamina cribrosa pores were automatically segmented using a previously described segmentation algorithm. Individual pore paths were automatically tracked through the depth of the lamina cribrosa using custom software. Pore path convergence to the optic nerve center and tortuosity was quantified for each eye. We found that lamina cribrosa pore pathways traverse the lamina cribrosa closer to the optic nerve center along the depth of the lamina cribrosa regardless of disease severity or diagnostic category. In addition, pores of glaucoma eyes take a more tortuous path through the lamina cribrosa compared to those of healthy eyes, suggesting a potential mechanism for reduction of axoplasmic flow in glaucoma.

Experimental study on pore structure and performance of sintered porous wick

NASA Astrophysics Data System (ADS)

He, Da; Wang, Shufan; Liu, Rutie; Wang, Zhubo; Xiong, Xiang; Zou, Jianpeng

2018-02-01

Porous wicks were prepared via powder metallurgy using NH4HCO3 powders as pore-forming agent. The pore-forming agent particle size was varied to control the pore structure and equivalent pore size distribution feature of porous wick. The effect of pore-forming agent particle size on the porosity, pore structures, equivalent pore size distribution and capillary pumping performance were investigated. Results show that with the particle size of pore-forming agent decrease, the green density and the volume shrinkage of the porous wicks gradually increase and the porosity reduces slightly. There are two types of pores inside the porous wick, large-sized prefabricated pores and small-sized gap pores. With the particle size of pore-forming agent decrease, the size of the prefabricated pores becomes smaller and the distribution tends to be uniform. Gap pores and prefabricated pores inside the wick can make up different types of pore channels. The equivalent pore size of wick is closely related to the structure of pore channels. Furthermore, the equivalent pore size distribution of wick shows an obvious double-peak feature when the pore-forming agent particle size is large. With the particle size of pore-forming agent decrease, the two peaks of equivalent pore size distribution approach gradually to each other, resulting in a single-peak feature. Porous wick with single-peak feature equivalent pore size distribution possesses the better capillary pumping performances.

75 FR 16509 - Certain Potassium Phosphate Salts From China

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-01

...)] Certain Potassium Phosphate Salts From China AGENCY: United States International Trade Commission. ACTION... retarded, by reason of subsidized and less-than-fair-value imports from China of certain potassium... ``phosphate salts''). Certain Potassium Phosphate Salts from the People's Republic of China: Preliminary...

Urine Potassium Excretion, Kidney Failure, and Mortality in CKD.

PubMed

Leonberg-Yoo, Amanda K; Tighiouart, Hocine; Levey, Andrew S; Beck, Gerald J; Sarnak, Mark J

2017-03-01

Low urine potassium excretion, as a surrogate for dietary potassium intake, is associated with higher risk for hypertension and cardiovascular disease in a general population. Few studies have investigated the relationship of urine potassium with clinical outcomes in chronic kidney disease (CKD). Longitudinal cohort study. The MDRD (Modification of Diet in Renal Disease) Study was a randomized controlled trial (N = 840) conducted in 1989 to 1993 to examine the effects of blood pressure control and dietary protein restriction on kidney disease progression in adults aged 18 to 70 years with CKD stages 2 to 4. This post hoc analysis included 812 participants. The primary predictor variable was 24-hour urine potassium excretion, measured at baseline and at multiple time points (presented as time-updated average urine potassium excretion). Kidney failure, defined as initiation of dialysis therapy or transplantation, was determined from US Renal Data System data. All-cause mortality was assessed using the National Death Index. Median follow-up for kidney failure was 6.1 (IQR, 3.5-11.7) years, with 9 events/100 patient-years. Median all-cause mortality follow-up was 19.2 (IQR, 10.8-20.6) years, with 3 deaths/100 patient-years. Baseline mean urine potassium excretion was 2.39±0.89 (SD) g/d. Each 1-SD higher baseline urine potassium level was associated with an adjusted HR of 0.95 (95% CI, 0.87-1.04) for kidney failure and 0.83 (95% CI, 0.74-0.94) for all-cause mortality. Results were consistent using time-updated average urine potassium measurements. Analyses were performed using urine potassium excretion as a surrogate for dietary potassium intake. Results are obtained from a primarily young, nondiabetic, and advanced CKD population and may not be generalizable to the general CKD population. Higher urine potassium excretion was associated with lower risk for all-cause mortality, but not kidney failure. Copyright © 2016 National Kidney Foundation, Inc. Published by

Potassium carbonate poisoning

MedlinePlus

... dishwasher soaps Some forms of potash (material from wood ashes that is used in fertilizers) Some home ... several weeks after the potassium carbonate was swallowed. Death from complications may occur up to several months ...

Micromechanics of cataclastic pore collapse in limestone

NASA Astrophysics Data System (ADS)

Zhu, Wei; Baud, Patrick; Wong, Teng-Fong

2010-04-01

The analysis of compactant failure in carbonate formations hinges upon a fundamental understanding of the mechanics of inelastic compaction. Microstructural observations indicate that pore collapse in a limestone initiates at the larger pores, and microcracking dominates the deformation in the periphery of a collapsed pore. To capture these micromechanical processes, we developed a model treating the limestone as a dual porosity medium, with the total porosity partitioned between macroporosity and microporosity. The representative volume element is made up of a large pore which is surrounded by an effective medium containing the microporosity. Cataclastic yielding of this effective medium obeys the Mohr-Coulomb or Drucker-Prager criterion, with failure parameters dependent on porosity and pore size. An analytic approximation was derived for the unconfined compressive strength associated with failure due to the propagation and coalescence of pore-emanated cracks. For hydrostatic loading, identical theoretical results for the pore collapse pressure were obtained using the Mohr-Coulomb or Drucker-Prager criterion. For nonhydrostatic loading, the stress state at the onset of shear-enhanced compaction was predicted to fall on a linear cap according to the Mohr-Coulomb criterion. In contrast, nonlinear caps in qualitative agreement with laboratory data were predicted using the Drucker-Prager criterion. Our micromechanical model implies that the effective medium is significantly stronger and relatively pressure-insensitive in comparison to the bulk sample.

Coupling of activation and inactivation gate in a K+-channel: potassium and ligand sensitivity

PubMed Central

Ader, Christian; Schneider, Robert; Hornig, Sönke; Velisetty, Phanindra; Vardanyan, Vitya; Giller, Karin; Ohmert, Iris; Becker, Stefan; Pongs, Olaf; Baldus, Marc

2009-01-01

Potassium (K+)-channel gating is choreographed by a complex interplay between external stimuli, K+ concentration and lipidic environment. We combined solid-state NMR and electrophysiological experiments on a chimeric KcsA–Kv1.3 channel to delineate K+, pH and blocker effects on channel structure and function in a membrane setting. Our data show that pH-induced activation is correlated with protonation of glutamate residues at or near the activation gate. Moreover, K+ and channel blockers distinctly affect the open probability of both the inactivation gate comprising the selectivity filter of the channel and the activation gate. The results indicate that the two gates are coupled and that effects of the permeant K+ ion on the inactivation gate modulate activation-gate opening. Our data suggest a mechanism for controlling coordinated and sequential opening and closing of activation and inactivation gates in the K+-channel pore. PMID:19661921

ACE inhibitors and potassium foods--nurses' knowledge.

PubMed

Bertrand, Brenda; Livingston-Bowen, Carrie; Duffrin, Christopher; Mann, Amanda

2014-01-01

According to Joint Commission standards, patients should be educated about drug-nutrient interactions. Because nurses are well-suited to educating patients, this paper aims to assess their knowledge of ACE inhibitor drugs, nutrient interactions and high- and low-potassium foods. Licensed nurses from a teaching hospital in the US south eastern Atlantic region completed a self-administered questionnaire (n = 83). Means, standard deviations and 95 percent confidence intervals were calculated for continuous data and frequency and percentage distribution for discrete data. Student's t-test was used to evaluate responses by ACE inhibitor patient load and nursing education. Mean nurse knowledge of ACE inhibitors and potassium was 62 +/- 16 percent and identifying high- and low-potassium foods was 32 +/- 23 percent. Most identified five from 12 high-potassium foods and did not know the designation of six, one from 14 low-potassium foods and did not know the designation of 11. Knowledge scores and identifying high- and low-potassium foods were similar regardless of ACE inhibitor patient load and nursing education. ACE inhibitors are the fourth most commonly used drug class in the USA. Nurses are well positioned to recognize potential drug-nutrient interactions owing to changing or adding a drug, dose delivery method, dietary change or a patient's physical or clinical status that may indicate nutrient deficiency. The findings suggest that the nurses surveyed were proficient in identifying ACE inhibitors pharmacology, but that most were unable to identify foods that increase drug-nutrient interaction risk, and thus this is an area in which additional training might be beneficial. Case menus were used to portray real-life scenarios in which healthcare practitioners can provide patient education about ACE inhibitor drug and dietary potassium interactions.

High-Efficiency Polycrystalline Thin Film Tandem Solar Cells.

PubMed

Kranz, Lukas; Abate, Antonio; Feurer, Thomas; Fu, Fan; Avancini, Enrico; Löckinger, Johannes; Reinhard, Patrick; Zakeeruddin, Shaik M; Grätzel, Michael; Buecheler, Stephan; Tiwari, Ayodhya N

2015-07-16

A promising way to enhance the efficiency of CIGS solar cells is by combining them with perovskite solar cells in tandem devices. However, so far, such tandem devices had limited efficiency due to challenges in developing NIR-transparent perovskite top cells, which allow photons with energy below the perovskite band gap to be transmitted to the bottom cell. Here, a process for the fabrication of NIR-transparent perovskite solar cells is presented, which enables power conversion efficiencies up to 12.1% combined with an average sub-band gap transmission of 71% for photons with wavelength between 800 and 1000 nm. The combination of a NIR-transparent perovskite top cell with a CIGS bottom cell enabled a tandem device with 19.5% efficiency, which is the highest reported efficiency for a polycrystalline thin film tandem solar cell. Future developments of perovskite/CIGS tandem devices are discussed and prospects for devices with efficiency toward and above 27% are given.

Enhancement of plasma generation in catalyst pores with different shapes

NASA Astrophysics Data System (ADS)

Zhang, Yu-Ru; Neyts, Erik C.; Bogaerts, Annemie

2018-05-01

Plasma generation inside catalyst pores is of utmost importance for plasma catalysis, as the existence of plasma species inside the pores affects the active surface area of the catalyst available to the plasma species for catalytic reactions. In this paper, the electric field enhancement, and thus the plasma production inside catalyst pores with different pore shapes is studied with a two-dimensional fluid model. The results indicate that the electric field will be significantly enhanced near tip-like structures. In a conical pore with small opening, the strongest electric field appears at the opening and bottom corners of the pore, giving rise to a prominent ionization rate throughout the pore. For a cylindrical pore, the electric field is only enhanced at the bottom corners of the pore, with lower absolute value, and thus the ionization rate inside the pore is only slightly enhanced. Finally, in a conical pore with large opening, the electric field is characterized by a maximum at the bottom of the pore, yielding a similar behavior for the ionization rate. These results demonstrate that the shape of the pore has a significantly influence on the electric field enhancement, and thus modifies the plasma properties.

Short-lived K2S Molecules in Superionic Potassium Sulfide

NASA Astrophysics Data System (ADS)

Okeya, Yusuke; Tsumuraya, Kazuo

2015-03-01

The first principles molecular dynamics method allows us to elucidate the formation of short-lived K2S molecular states in superionic potassium sulfide. The covalent and the Coulomb bonds exist between the ionized mobile potassiums and the ionized immobile sulfurs. Both the bonds induces indirect covalent and indirect Coulomb attractions between the di-interstitial potassiums on the mid-sulfurs, which forms the short-lived K2S molecular states. The covalent electron density also exists between short-lived potassium dimers. The three attractions reduce Haven's ratios of the potassiums in the conductor. The molecule formation indicates the electronic state of the conductor is intermediate between the ionic and covalent crystals. The absence of the long-lived potassium dimers implies a failure of the caterpillar diffusion model or the Frenkel-Kontorova chain model for the superionic diffusion of the potassiums in the sulfide. The incompletely ionized cations and anions reduce the Coulomb attractions between them which induces the sublattice melting of smaller size of the potassiums than the sulfurs.

Down-state model of the voltage-sensing domain of a potassium channel.

PubMed

Schow, Eric V; Freites, J Alfredo; Gogna, Karun; White, Stephen H; Tobias, Douglas J

2010-06-16

Voltage-sensing domains (VSDs) of voltage-gated potassium (Kv) channels undergo a series of conformational changes upon membrane depolarization, from a down state when the channel is at rest to an up state, all of which lead to the opening of the channel pore. The crystal structures reported to date reveal the pore in an open state and the VSDs in an up state. To gain insights into the structure of the down state, we used a set of experiment-based restraints to generate a model of the down state of the KvAP VSD using molecular-dynamics simulations of the VSD in a lipid bilayer in excess water. The equilibrated VSD configuration is consistent with the biotin-avidin accessibility and internal salt-bridge data used to generate it, and with additional biotin-avidin accessibility data. In the model, both the S3b and S4 segments are displaced approximately 10 A toward the intracellular side with respect to the up-state configuration, but they do not move as a rigid body. Arginine side chains that carry the majority of the gating charge also make large excursions between the up and down states. In both states, arginines interact with water and participate in salt bridges with acidic residues and lipid phosphate groups. An important feature that emerges from the down-state model is that the N-terminal half of the S4 segment adopts a 3(10)-helical conformation, which appears to be necessary to satisfy a complex salt-bridge network. (c) 2010 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Down-State Model of the Voltage-Sensing Domain of a Potassium Channel