scholarly journals The interaction of copper(II) and glycyl-l-histidyl-l-lysine, a growth-modulating tripeptide from plasma

1981 ◽  
Vol 199 (3) ◽  
pp. 649-656 ◽  
Author(s):  
S J Lau ◽  
B Sarkar
Keyword(s):  
Stability Constants ◽  
Equilibrium Dialysis ◽  
Physiological Role ◽  
Ternary Complexes ◽  
Low Molecular Weight ◽  
Visible Absorption ◽  
Multiple Species ◽  
The Stability ◽  
Ph Range

The interaction between Cu(II) and the growth-modulating tripeptide glycyl-L-histidyl-L-lysine in the presence and absence of L-histidine was investigated by potentiometric titration and visible-absorption spectrophotometry at 25 degrees C in 0.15 M-NaCl. Analyses of the results in the pH range 3.5--10.6 indicated the presence of multiple species in solution in the binary system and extensive amounts of the ternary complexes in the ternary system. The species distribution and the stability constants, as well as the visible-absorption spectra of the species, were evaluated. The combined results were used to propose the structure of some of the complexes. The influence of the epsilon-amino group of the peptide in the enhancement of the stability constants was reflected prominently when compared with those complexes formed by either glycyl-L-histidine or glycyl-L-histidylglycine. The results obtained from the equilibrium-dialysis experiments showed that this tripeptide was able to compete with albumin for Cu(II) at pH 7.5 and 6 degrees C. At equimolar concentrations of albumin and the peptide, about 42% of the Cu(II) was bound to the peptide. At the physiologically relevant concentrations of Cu(II), albumin, L-histidine and this peptide, about 6% of the Cu(II) was associated with the low-molecular-weight components. This distribution could be due to the binary as well as the ternary complexes. The possible physiological role of these complexes in the transportation of Cu(II) from blood to tissues is discussed.

Equilibria of the Simultaneously Existing Multiple Species in the Copper(II)–L-Histidine System

1973 ◽  
Vol 51 (21) ◽  
pp. 3549-3554 ◽  
Author(s):  
Theo P. A. Kruck ◽  
Bibudhendra Sarkar
Keyword(s):  
Statistical Analysis ◽  
Standard Deviation ◽  
Stability Constants ◽  
Individual Values ◽  
Complex Species ◽  
Molar Ratios ◽  
Multiple Species ◽  
The Stability ◽  
Ph Range ◽  
The Individual

The complete species distribution and the stability constants of the complex species in the Cu(II)–L-histidine system have been worked out for the pH range 2–11. The method of "analytical potentiometry" has been applied successfully to this system having excess ligand with respect to Cu(II) ion. The equilibria of three systems of Cu(II) (M) and L-histidine (H3A) in molar ratios of 1:2, 1:4, and 1:8 were investigated by this technique in 0.15 M NaCl at 25°. The following species were detected in this system: MHA, MA, MH2A2, MHA2, MA2, MH−1A2, MH−1A, and M2H−2A2. Statistical analysis on the numerical results has been performed and is given as standard deviation together with the individual values for the stability constants.

scholarly journals Stability Studies of Transition Metal Chelates of 5-Bromosalicylidene-4-methoxyaniline andSalicylidene-2,3-dimethylaniline as Ligands

2011 ◽  
Vol 8 (4) ◽  
pp. 1911-1915
Author(s):  
N. G. Nadkarni ◽  
K. V. Mangaonkar
Keyword(s):  
Ionic Strength ◽  
Transition Metal ◽  
Stability Constants ◽  
Metal Chelates ◽  
Ternary Complexes ◽  
Water Medium ◽  
Stability Studies ◽  
Binary And Ternary Complexes ◽  
Transition Metal Chelates ◽  
The Stability

Binary and ternary complexes of the type M-Y and M-X-Y [M = Mn(II), Ni(II), Cu(II) and Zn(II); X = 5-bromosalicylidene-4-methoxyaniline and Y = salicylidene-2,3-dimethylaniline] have been examined pH-metrically at 27±0.5°C and at constant ionic strength, μ = 0.1 M (KCl) in 75 : 25(v/v) 1,4-dioxne-water medium. The stability constants for binary (M-Y) and ternary (M-X-Y) systems were calculated.

Physicochemical investigation on thiomalate complexes of nickel

1968 ◽  
Vol 21 (3) ◽  
pp. 641 ◽  
Author(s):  
RS Saxena ◽  
KC Gupta ◽  
ML Mittal
Keyword(s):  
Aqueous Medium ◽  
Stability Constants ◽  
Alternative Methods ◽  
Acid System ◽  
Kcal Mole ◽  
Physicochemical Investigation ◽  
Different Temperatures ◽  
The Stability ◽  
Ph Range ◽  
Deep Violet

Potentiometric and conductometric studies of the nickel-thiomalic acid system, in aqueous medium of 0. lM KNO3, reveal the formation of two complexes; one light violet 1 : 1 predominating at pH 6.5-7.5 and another deep violet 1 : 2 in the pH range 8.5-10.0. The stability constants of the complexes formed have been determined by applying Calvin and Melchior's extension of Bjerrum's method at three different temperatures and were further refined by using alternative methods. The logK values (final) for 1 : 1 and 1 : 2 complexes at 20, 25, and 30� have been found to be 7.86, 7.87, 7.96, and 6.24, 6.31, 6.39 respectively. The values of the overall changes in ΔG, ΔH, and ΔS accompanying the reaction have also been evaluated at 25� and found to be -19.31 kcal/mole, -8.77 kcal/mole, and +35.36 cal/deg respectively.

Transferrin binding of Al3+ and Fe3+.

1987 ◽  
Vol 33 (3) ◽  
pp. 405-407 ◽  
Author(s):  
R B Martin ◽  
J Savory ◽  
S Brown ◽  
R L Bertholf ◽  
M R Wills
Keyword(s):  
Stability Constant ◽  
Blood Plasma ◽  
Stability Constants ◽  
Metal Ion ◽  
Equilibrium Dialysis ◽  
Ion Binding ◽  
Metal Ion Binding ◽  
Quantitative Studies ◽  
Intensity Changes ◽  
The Stability

Abstract An understanding of Al3+-induced diseases requires identification of the blood carrier of Al3+ to the tissues where Al3+ exerts a toxic action. Quantitative studies demonstrate that the protein transferrin (iron-free) is the strongest Al3+ binder in blood plasma. Under plasma conditions of pH 7.4 and [HCO3-]27 mmol/L, the successive stability constant values for Al3+ binding to transferrin are log K1 = 12.9 and log K2 = 12.3. When the concentration of total Al3+ in plasma is 1 mumol/L, the free Al3+ concentration permitted by transferrin is 10(-14.6) mol/L, less than that allowed by insoluble Al(OH)3, by Al(OH)2H2PO4, or by complexing with citrate. Thus transferrin is the ultimate carrier of Al3+ in the blood. We also used intensity changes produced by metal ion binding to determine the stability constants for Fe3+ binding to transferrin: log K1 = 22.7 and log K2 = 22.1. These constants agree closely with a revision of the reported values obtained by equilibrium dialysis. By comparison with Fe3+ binding, the Al3+ stability constants are weaker than expected; this suggests that the significantly smaller Al3+ ions cannot coordinate to all the transferrin donor atoms available to Fe3+.

Ternary Complexes in Solution, XII. Models for Biological Mixed-Ligand Complexes: 2,2′-Bipyridyl-Cu2+-Oligoglycine Systems

1972 ◽  
Vol 27 (4) ◽  
pp. 353-364 ◽  
Author(s):  
Helmut Sigel ◽  
Rolf Griesser ◽  
Bernhard Prijs
Keyword(s):  
Coordination Sphere ◽  
Ternary Complexes ◽  
Mixed Ligand ◽  
Amide Group ◽  
Amide Proton ◽  
Mixed Ligand Complexes ◽  
Apical Position ◽  
Binary Complexes ◽  
The Stability ◽  
Ph Range

The stability constants of the binary Cu2+ complexes of glycine amide, diglycine, diglycine amide, triglycine, and tetraglycine were determined, as were those of the mixed-ligand Cu2+ systems containing 2,2′-bipyridyl and one of the mentioned oligoglycines. The results evidence that all these complexes have the same structure and, therefore, the binding sites of the ligands have to be the terminal amino group and the oxygen of the neighbored amide group. The stability differences between the ternary and the binary complexes are in agreement with this interpretation. It is of interest to note that these ternary complexes are significantly more stable than expected on statistical reasons. With increasing pH, the amide groups in the binary complexes are successively deprotonated. Thus, with tetraglycine finally all three amide protons are displaced, and the amide nitrogens are bound to the square-planar coordination sphere of Cu2+. As in the Cu2+-2,2′-bipyridyl 1 : 1 complex, only two coordination positions are left for the binding of the oligoglycine, in the tenary complexes, only one amide group can be deprotonated. An increase in pH with deprotonation of other amide groups leads to a displacement of 2,2′-bipyridyl, i. e. the simple binary complexes result. No evidence could be observed for the coordination of a deprotonated amide group to an apical position of the coordination sphere of Cu2+. Additionally, while the displacement of the first amide proton in the several binary Cu2+ oligoglycine complexes occurs over a large pH range (4 to 7), the deprotonation in all the mixed-ligand complexes takes place at pH approximately 8.

scholarly journals Drinking and Water Handling in the Medaka Intestine: A Possible Role of Claudin-15 in Paracellular Absorption?

2020 ◽  
Vol 21 (5) ◽  
pp. 1853
Author(s):  
Christian K. Tipsmark ◽  
Andreas M. Nielsen ◽  
Maryline C. Bossus ◽  
Laura V. Ellis ◽  
Christina Baun ◽  
...  
Keyword(s):  
Water Transport ◽  
Physiological Role ◽  
Japanese Medaka ◽  
Apparent Difference ◽  
Drinking Rate ◽  
Functional Changes ◽  
Water Handling ◽  
Paracellular Absorption ◽  
The Stability

When euryhaline fish move between fresh water (FW) and seawater (SW), the intestine undergoes functional changes to handle imbibed SW. In Japanese medaka, the potential transcellular aquaporin-mediated conduits for water are paradoxically downregulated during SW acclimation, suggesting paracellular transport to be of principal importance in hyperosmotic conditions. In mammals, intestinal claudin-15 (CLDN15) forms paracellular channels for small cations and water, which may participate in water transport. Since two cldn15 paralogs, cldn15a and cldn15b, have previously been identified in medaka, we examined the salinity effects on their mRNA expression and immunolocalization in the intestine. In addition, we analyzed the drinking rate and intestinal water handling by adding non-absorbable radiotracers, 51-Cr-EDTA or 99-Tc-DTPA, to the water. The drinking rate was >2-fold higher in SW than FW-acclimated fish, and radiotracer experiments showed anterior accumulation in FW and posterior buildup in SW intestines. Salinity had no effect on expression of cldn15a, while cldn15b was approximately 100-fold higher in FW than SW. Despite differences in transcript dynamics, Cldn15a and Cldn15b proteins were both similarly localized in the apical tight junctions of enterocytes, co-localizing with occludin and with no apparent difference in localization and abundance between FW and SW. The stability of the Cldn15 protein suggests a physiological role in water transport in the medaka intestine.

scholarly journals Complexation of Th(IV) and Eu(III) by α-isosaccharinic acid under alkaline conditions

2001 ◽  
Vol 89 (6) ◽  
Author(s):  
K. Vercammen ◽  
M.A. Glaus ◽  
Luc R. Van Loon
Keyword(s):  
Stability Constants ◽  
Data Sets ◽  
Complexation Reaction ◽  
Sorption Data ◽  
Alkaline Conditions ◽  
The Stability ◽  
Ph Range ◽  
Complexation Reactions ◽  
Best Fit ◽  
Isosaccharinic Acid

The complexation of Th(IV) and Eu(III) by α-isosaccharinic acid (ISA) has been studied in the pH range from 10.7 to 13.3 by batch sorption experiments, and the influence of Ca on the complexation was investigated. Sixteen data sets – each determined at variable ISA concentrations – are used to determine the stoichiometry of the complexation reactions and the stability constants. Based on best-fit analysis of the sorption data, it is postulated that 1:1 Th:ISA complexes are formed in the absence of Ca according to the complexation reaction: Th+ISA↔(ThISA)

Interligand interaction in ternary complexes of Zn(II) and Cd(II) with dipeptides and aminoacids

1994 ◽  
Vol 72 (4) ◽  
pp. 1107-1110 ◽  
Author(s):  
Alexander Varghese Vaidyan ◽  
Pabitra K. Bhattacharya
Keyword(s):  
Ionic Strength ◽  
Aqueous Medium ◽  
Computer System ◽  
Stability Constants ◽  
Ternary Complexes ◽  
Binary And Ternary Complexes ◽  
The Stability ◽  
Interligand Interaction

The stability constants of binary and ternary complexes [MA], [Ma2], and [MAL] (where M = Zn(II) or Cd(II); A = glycylglycine, glycyl L-alanine, glycyl L-leucine; L = α-alanine phenylalanine, tyrosine, tryptophan, or L-histidine) in aqueous medium have been determined potentometrically at 25 °C and an ionic strength of 0.2 M NaClO4 (0.2 mol dm−3) using a computer system. It is observed that Δ log K of MAL complexes has low negative or positive values. Probable reasons have been discussed.

Impact of inorganic buffering ions on the stability of Fe(vi) in aqueous solution: role of the carbonate ion

2016 ◽  
Vol 18 (6) ◽  
pp. 4415-4422 ◽  
Author(s):  
Michal Kolář ◽  
Petr Novák ◽  
Karolína M. Šišková ◽  
Libor Machala ◽  
Ondřej Malina ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Carbonate Ion ◽  
The Stability ◽  
Ph Range

The study presents a systematic kinetics investigation of the decay of ferrate(vi) in the presence of inorganic buffering ions (borate, phosphate, and carbonate) at a pH range from 6.0 to 9.0.

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