scholarly journals High affinity divalent cation exchange on actin. Association rate measurements support the simple competitive model.

1991 ◽  
Vol 266 (1) ◽  
pp. 76-82 ◽  
Author(s):  
L C Gershman ◽  
L A Selden ◽  
J E Estes
Keyword(s):  
Cation Exchange ◽  
Divalent Cation ◽  
Association Rate ◽  
High Affinity ◽  
Competitive Model

scholarly journals High Affinity Divalent Cation Binding to Actin

1989 ◽  
Vol 264 (16) ◽  
pp. 9271-9277 ◽  
Author(s):  
L A Selden ◽  
J E Estes ◽  
L C Gershman
Keyword(s):  
Divalent Cation ◽  
Cation Binding ◽  
High Affinity

Phosphorus sorption and nitrogen transformation in two soils treated with piggery wastewater

Soil Research ◽  
2002 ◽  
Vol 40 (2) ◽  
pp. 335 ◽  
Author(s):  
I. R. Phillips
Keyword(s):  
Cation Exchange ◽  
Root Zone ◽  
Sandy Loam ◽  
Sorption Kinetics ◽  
Land Application ◽  
Piggery Wastewater ◽  
Wastewater Disposal ◽  
P Sorption ◽  
High Affinity ◽  
Irrigated Soils

Land application of piggery wastewater has the potential to contaminate receiving water bodies due to the presence of elevated concentrations of nitrogen (N) and phosphorus (P). This paper investigates P sorption and N transformation using soil from 2 wastewater disposal sites in south-east Queensland. Soil from Site 1 was classified as a clay (Vertosol) and soil from Site 2 was classified as a sandy loam (Sodosol). Soil was collected from wastewater disposal (irrigated) and non-disposal (non-irrigated) areas of each site. Nutrient sorption kinetics and transformation were studied by reacting each soil with either wastewater or an inorganic salt solution over a period of 21 days. Solution P concentrations decreased with time for all soils. These changes were greatest during the early stage of the study (<10 days), after which time solution P concentrations remained relatively stable. Concentrations of solution P tended to remain higher in irrigated than non-irrigated soils. This was attributed to a loss of high-affinity sorption sites due to past wastewater additions. Cation exchange (for times <3 days) and nitrification (for times >3 days) were found to be the primary mechanisms responsible for decreases in solution ammonium (NH4-N) over the 21-day period. Phosphorus and NH4-N sorption isotherms were determined using a leaching procedure, and the data were adequately described (r2 >0.95) by the Freundlich equation. Irrigated samples generally sorbed less P than non-irrigated soils. This was attributed to the loss of high-affinity P sorption sites due to previous wastewater additions. Cation exchange and competition between added and resident cations for the exchange sites was found to govern NH4-N sorption by these soils. Results from this study suggest that long-term land application of piggery wastewater may encourage leaching of N and P from the plant root-zone in soils with limited capacity to retain these nutrients. Appropriate management strategies to minimise these losses need to be developed to avoid degradation of the receiving soil and/or water environments. sorption kinetics, nitrification, ammonium, nitrate.

Equilibrium Partitioning of Monovalent/Divalent Cation-Salt Mixtures in Nafion Cation-Exchange Membranes

1995 ◽  
Vol 99 (34) ◽  
pp. 12915-12924 ◽  
Author(s):  
P. N. Pintauro ◽  
R. Tandon ◽  
L. Chao ◽  
W. Xu ◽  
R. Evilia
Keyword(s):  
Cation Exchange ◽  
Divalent Cation ◽  
Equilibrium Partitioning ◽  
Salt Mixtures

scholarly journals Effect of heparin on the glia-derived-nexin-thrombin interaction

1989 ◽  
Vol 257 (1) ◽  
pp. 191-196 ◽  
Author(s):  
A Wallace ◽  
G Rovelli ◽  
J Hofsteenge ◽  
S R Stone
Keyword(s):  
Rate Constants ◽  
Antithrombin Iii ◽  
Kinetic Properties ◽  
Association Rate ◽  
High Affinity ◽  
Diffusion Controlled ◽  
Different Types ◽  
Human Thrombin ◽  
Alpha Beta ◽  
Association Rate Constants

In order to determine the specificity of the interaction between thrombin and glia-derived nexin (GdN), the inactivation of proteolytically modified human thrombin species by GdN has been studied. The second-order rate constants for the inactivation of alpha-, beta T-, gamma T- and epsilon-thrombin by GdN were 1.41, 0.63, 0.33 and 1.91 microM-1.s-1 respectively. The kinetic properties of gdN were also investigated in the presence of different types of heparin, fractionated according to antithrombin III-binding affinity. Association rate constants of both gdN and antithrombin III with alpha-thrombin were obtained using unfractionated, low- and high-affinity heparin types. The different heparin types gave optimal rates of inhibition at similar heparin concentrations for both inhibitors. At optimal heparin concentrations, the rate of inactivation of alpha-thrombin by GdN was 0.5-1.2 nM-1.s-1, which suggests that, under these conditions, the interaction is diffusion-controlled.

scholarly journals Synaptotagmin VII Is Targeted to Secretory Organelles in PC12 Cells, Where It Functions as a High-Affinity Calcium Sensor

2005 ◽  
Vol 25 (19) ◽  
pp. 8693-8702 ◽  
Author(s):  
Ping Wang ◽  
Michael C. Chicka ◽  
Akhil Bhalla ◽  
David A. Richards ◽  
Edwin R. Chapman
Keyword(s):  
Rna Interference ◽  
Pc12 Cells ◽  
Divalent Cation ◽  
Calcium Sensor ◽  
Concomitant Increase ◽  
Apparent Affinity ◽  
Metal Affinity ◽  
High Affinity ◽  
Large Dense Core Vesicles ◽  
A Cell

ABSTRACT Synaptotagmin (syt) I is thought to act as a Ca2+ sensor that regulates neuronal exocytosis. Fifteen additional isoforms of syt have been identified, but their functions are less well understood. Here, we used PC12 cells to test the idea that different isoforms of syt impart cells with distinct metal (i.e., Ca2+, Ba2+, and Sr2+) requirements for secretion. These cells express syt's I and IX (syt IX sometimes referred to as syt V), which have low apparent metal affinities, at much higher levels than syt VII, which we show has a relatively high apparent affinity for metals. We found that syt I and VII partially colocalize on large dense core vesicles and that upregulation of syt VII produces a concomitant increase in the divalent cation sensitivity of catecholamine release from PC12 cells. Furthermore, RNA interference-mediated knockdown of endogenous syt VII reduced the metal sensitivity of release. These data support the hypothesis that the complement of syt's expressed by a cell, in conjunction with their metal affinity, determines the divalent cation sensitivity of exocytosis.

Influence of the High Affinity Divalent Cation on Actin Tryptophan Fluorescence

1994 ◽  
pp. 51-57 ◽  
Author(s):  
Lynn A. Selden ◽  
Henry J. Kinosian ◽  
James E. Estes ◽  
Lewis C. Gershman
Keyword(s):  
Divalent Cation ◽  
Tryptophan Fluorescence ◽  
High Affinity

scholarly journals Luminal Ca2+ content regulates intracellular Ca2+ release in subepicardial myocytes of intact beating mouse hearts: effect of exogenous buffers

2010 ◽  
Vol 298 (6) ◽  
pp. H2138-H2153 ◽  
Author(s):  
Dmytro Kornyeyev ◽  
Mariano Reyes ◽  
Ariel L. Escobar
Keyword(s):  
Frequency Dependence ◽  
Ventricular Myocytes ◽  
Heart Beat ◽  
Association Rate ◽  
Intact Mouse ◽  
High Affinity ◽  
Pathological Conditions ◽  
Epicardial Layer ◽  
Major Factors

Ca+-induced Ca2+ release tightly controls the function of ventricular cardiac myocytes under normal and pathological conditions. Two major factors contributing to the regulation of Ca2+ release are the cytosolic free Ca2+ concentration and sarcoplasmic reticulum (SR) Ca2+ content. We hypothesized that the amount of Ca2+ released from the SR during each heart beat strongly defines the refractoriness of Ca2+ release. To test this hypothesis, EGTA AM, a high-affinity, slow-association rate Ca2+ chelator, was used as a tool to modify luminal SR Ca2+ content. An analysis of the cytosolic and luminal SR Ca2+ dynamics recorded from the epicardial layer of intact mouse hearts indicated that the presence of EGTA reduced the diastolic SR free Ca2+ concentration and fraction of SR Ca2+ depletion during each beat. In addition, this maneuver shortened the refractory period and accelerated the restitution of Ca2+ release. As a consequence of the accelerated restitution, the frequency dependence of Ca2+ alternans was significantly shifted toward higher heart rates, suggesting a role of luminal SR Ca2+ in the genesis of this highly arrhythmogenic phenomenon. Thus, intra-SR Ca2+ dynamics set the refractoriness and frequency dependence of Ca2+ transients in subepicardial ventricular myocytes.

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