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+.

Fluorescence Analysis of Cu(II), Pb(II) and Hg(II) Ion Binding to Humic and Fulvic Acids

2016 ◽  
Vol 851 ◽  
pp. 135-140 ◽  
Author(s):  
Vojtěch Enev ◽  
Irena Türkeová ◽  
Jana Szewieczková ◽  
Leos Doskocil ◽  
Martina Klučáková
Keyword(s):  
Humic Substances ◽  
Stability Constants ◽  
Metal Ion ◽  
Fluorescence Analysis ◽  
Fulvic Acids ◽  
Ion Binding ◽  
Conditional Stability ◽  
Metal Ion Binding ◽  
The Stability ◽  
Conditional Stability Constants

Abstract. The aim of this work was to study molecular and quantitative aspects of metal ion binding to humic substances (HS). The object of our study was characterization of two standards of humic substances (Elliott Soil standard HA 1S102H and Elliott Soil standard FA 2S102F). All samples of IHSS standards HS were characterized by elemental analysis (EA), ultraviolet-visible spectroscopy (UV/Vis), Fourier transform infrared spectroscopy (FTIR) and steady-state fluorescence spectroscopy. Chemical parameters on the complexation of Cu (II), Pb(II) and Hg(II), including the conditional stability constants and the percentage of fluorophores participating in the complexation, were estimated by the modified Stern–Volmer equation. The stability constants (log Ka) of Me(II)–ESHS complexes range from 3.70 to 5.15 in the order: Hg–ESHA>Cu–ESHA>Pb–ESHA>Cu–ESFA>Pb–ESFA. With respect to the ESHA, ESFA, which showed the smallest contents of O-containing functional groups (e.g. hydroxyl, carbonyl, ester, especially carboxyl groups on the aromatic ring) and the lowest humification degree, the ESFA was characterized by much smaller stability constants. Our findings suggest that soil HS belongs to class of important organic ligands for complexation with heavy metal ions and may significantly affect the chemical forms, mobility, bioavailability and ecotoxicity of heavy metals in the soil environment.

scholarly journals Metal Ion-Binding Properties of the Diphosphate Ester Analogue, Methylphosphonylphosphate, in Aqueous Solution

1999 ◽  
Vol 6 (6) ◽  
pp. 321-328 ◽  
Author(s):  
Bin Song ◽  
Jing Zhao ◽  
Fridrich Gregáň ◽  
Nadja Prónayová ◽  
S. Ali A. Sajadi ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Metal Ion ◽  
Minor Role ◽  
Ion Binding ◽  
Metal Ion Binding ◽  
Ph Titration ◽  
Role Based ◽  
The Stability ◽  
A Minor ◽  
Complex Stabilities

The stability constants of the 1:1 complexes formed between methylphosphonylphosphate (MePP3-), CH3P(O)2--O-PO32- , and Mg2+, Ca2+, Sr2+, Ba2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+,​ or Cd2+ (M2+) were determined by potentiometric pH titration in aqueous solution (25 C° ; l = 0.1 M, NaNO3 ). Monoprotonated M(H;MePP) complexes play only a minor role. Based on previously established correlations for M2+ -diphosphate monoester complex-stabilities and diphosphate monoester β-group. basicities, it is shown that the M(Mepp)- complexes for Mg2+ and the ions of the second half of the 3d series, including Zn2+ and Cd2+, are on average by about 0.15 log unit more stable than is expected based on the basicity of the terminal phosphate group in MePP3-. In contrast, Ba(Mepp)- and Sr(Mepp)- are slightly less stable, whereas the stability for Ca(Mepp)- is as expected, based on the mentioned correlation. The indicated increased stabilities are explained by an increased basicity of the phosphonyl group compared to that of a phosphoryl one. For the complexes of the alkaline earth ions, especially for Ba2+, it is suggested that outersphere complexation occurs to some extent. However, overall the M(Mepp)- complexes behave rather as expected for a diphosphate monoester ligand.

Metal ion catalysis of the decomposition of transient 2-carboxy-2,5-cyclohexadienones in aqueous solution

1988 ◽  
Vol 66 (5) ◽  
pp. 1194-1198 ◽  
Author(s):  
Oswald S. Tee ◽  
N. Rani Iyengar
Keyword(s):  
Aqueous Solution ◽  
Carboxylic Acid ◽  
Metal Ion ◽  
Hydrogen Ion ◽  
Ion Binding ◽  
Metal Ion Binding ◽  
Ferric Ions ◽  
Bromide Ion ◽  
Metal Ion Catalysis ◽  
The Stability

Bromide ion induced debromination of the anion of 4-bromo-4-methyl-2,5-cyclohexadienone-2-carboxylic acid (1) is catalyzed by cupric ions and ferric ions. Similarly, the enolization of the anion of the benzocyclohexadienone 3, which is formed during the bromination of 1-naphthol-2-carboxylic acid, is catalyzed by some metal ions. The origin of the catalysis in these reactions is strong metal ion binding to the incipient dianion products that are of the salicylate type. Evidence for this is that the efficiency of the metal (and hydrogen) ion catalysis parallels the stability of the analogous complexes with the salicylate dianion.

H101G Mutation in Rat Lens αB-Crystallin Alters Chaperone Activity and Divalent Metal Ion Binding

2021 ◽  
Vol 22 ◽  
Author(s):  
Yi-Ying Wu ◽  
Naveen Kumar Reddy Desu ◽  
Shou-Yun Lu ◽  
Bi-Yu Yu ◽  
Ramya Kumar ◽  
...  
Keyword(s):  
Binding Site ◽  
Metal Ion ◽  
Divalent Metal ◽  
Chaperone Activity ◽  
Ion Binding ◽  
Metal Ion Binding ◽  
Functional Changes ◽  
Αb Crystallin ◽  
Divalent Metal Ion ◽  
The Stability

Background: The molecular chaperone function of αB-crystallins is heavily involved in maintaining lens transparency and the development of cataracts. Objective: To study whether divalent metal ion binding improves the stability and αB-crystallin chaperone activity. Results: Substitution of His101 with glycine resulted in structural and functional changes. Spectral analysis and chaperone-like activity assays showed that substitution of glycine resulted in a higher percentage of random coils, increased hydrophobicity, and 22±2% higher chaperone-like activity. Whereas in the presence of the Cu2+ ion, H101G exhibited 32±1% less chaperone-like activity compared to the wild type. Conclusion: Cu2+ has been reported to enhance the chaperone-like activity of lens α-crystallin. Our results indicate that H101 is the predominant Cu2binding site, and the mutation resulted in a partial unfolding that impaired the binding of Cu2+ to H101 residue. In conclusion, this study further helps to understand the important binding site for Cu2+ to αB-crystallin.

scholarly journals Controlling the redox properties of a pyrroloquinolinequinone (PQQ) derivative in a ruthenium(ii) coordination sphere

2015 ◽  
Vol 44 (7) ◽  
pp. 3151-3158 ◽  
Author(s):  
Hiroumi Mitome ◽  
Tomoya Ishizuka ◽  
Yoshihito Shiota ◽  
Kazunari Yoshizawa ◽  
Takahiko Kojima
Keyword(s):  
Coordination Sphere ◽  
Metal Ion ◽  
Reduction Potential ◽  
Reduction Process ◽  
Redox Properties ◽  
Ion Binding ◽  
Metal Ion Binding ◽  
Coordination Modes ◽  
Redox Active ◽  
The Stability

Difference in the coordination modes of pyrroloquinolinequinone (PQQ), a redox-active heteroaromatic cofactor, in ruthenium(ii) complexes, drastically affects the stability of the metal coordination and the reversibility of the reduction process of the PQQ ligand. Additional metal-ion binding to the PQQ ligand largely raises its 1e−-reduction potential.

Metal Ion-Binding Properties in Aqueous Solution of the Nucleoside Analogue, 5,6-Dichloro-1-(β-ᴅ-ribofuranosyl)benzimidazole (DRB)

1998 ◽  
Vol 53 (8) ◽  
pp. 903-908 ◽  
Author(s):  
Larisa E. Kapinos ◽  
Bin Song ◽  
Helmut Sigel
Keyword(s):  
Aqueous Solution ◽  
Metal Ion ◽  
Ion Binding ◽  
Acidity Constant ◽  
Metal Ion Binding ◽  
Binding Properties ◽  
Straight Line ◽  
Data Points ◽  
The Stability ◽  
Straight Lines

Abstract The stability constants of the 1:1 complexes formed between Mg2+, Ca2+, Sr2+, Ba2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+ or Cd2+ (= M2+) and 5,6-dichloro-l-(β-ᴅ-ribofuranosyl)benzim idazole (DRB) were determined by potentiom etric pH titrations in aqueous solution (25 °C; I = 0.5м, NaNO3). The acidity constant of H(DRB)+, the proton being at N3, was measured by the same method and the result was confirmed via spectrophotometry. Based on previously established [L. E. Kapinos, B. Song, H. Sigel, Inorg. Chim . Acta 280, in press (1998)] logммʟ versus Kʜʜʟ straight-line plots for complexes of imidazole-type ligands it is shown for the Mn(DRB)2+ and Zn (DRB)2+ complexes, as examples, that the benzene ring of the benzim idazole residue exerts a steric inhibition for metal ion binding at N3; i.e., the data points for the M(DRB)2+ complexes fall clearly below the straight lines defined by the imidazole- type ligands.

Metal Ion-Binding Properties of the Nucleotide Analogue 1-[2-(Phosphonomethoxy)ethyl]cytosine (PMEC) in Aqueous Solution

1999 ◽  
Vol 64 (4) ◽  
pp. 613-632 ◽  
Author(s):  
Claudia A. Blindauer ◽  
Antonín Holý ◽  
Helmut Sigel
Keyword(s):  
Aqueous Solution ◽  
Metal Ions ◽  
Metal Ion ◽  
Ion Binding ◽  
Metal Ion Binding ◽  
Binding Properties ◽  
Nucleotide Analogue ◽  
Ether Oxygen ◽  
The Stability ◽  
Isomeric Equilibria

The acidity constants of the twofold protonated nucleotide analogue 1-[2-(phosphonomethoxy)ethyl]cytosine, H2(PMEC)±, as well as the stability constants of the M(H;PMEC)+ and M(PMEC) complexes with the metal ions M2+ = Mg2+, Ca2+, Sr2+, Ba2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, and Cd2+ have been determined by potentiometric pH titrations in aqueous solution at I = 0.1 M (NaNO3) and 25 °C. Comparison with previous results for the nucleobase-free compound (phosphonomethoxy)ethane, PME, and the parent nucleotides cytidine 5'-monophosphate (CMP2-) and 2'-deoxycytidine 5'-monophosphate (dCMP2-) shows that the metal ion-binding properties of PMEC2- resemble closely those of PME2-: This means, the primary binding site is the phosphonate group and with all of the metal ions studied, 5-membered chelates involving the ether oxygen of the -CH2-O-CH2-PO32- chain are formed. The position of the isomeric equilibria between these chelates and the "open" complexes, -PO32-/M2+ is calculated; the degree of formation of the chelates is identical within the error limits for the M(PME) and M(PMEC) systems. Hence, like in M(CMP) and M(dCMP) no interaction occurs with the cytosine residue in the M(PMEC) complexes. However, the monoprotonated M(H;PMEC)+ as well as the M(H;CMP)+ and M(dCMP)+ species carry the metal ion predominantly at the nucleobase, while the proton is at the phosph(on)ate group. The coordinating properties of PMEC2- and CMP2- or dCMP2- differ thus only with respect to the possible formation of the 5-membered chelates involving the ether oxygen in M(PMEC) species, a possibility which does not exist in the complexes of the parent nucleotides. Possible reasons why PMEC is devoid of a significant antiviral activity are shortly discussed.

scholarly journals Adenosine 5'-triphosphate (ATP4-): Aspects of the coordination chemistry of a multitalented biological substrate

2004 ◽  
Vol 76 (2) ◽  
pp. 375-388 ◽  
Author(s):  
H. Sigel
Keyword(s):  
Nucleic Acid ◽  
Metal Ions ◽  
Metal Ion ◽  
Hydrophobic Interactions ◽  
Ion Binding ◽  
Metal Ion Binding ◽  
Chelate Formation ◽  
Stability Of Complexes ◽  
Biological Substrate ◽  
The Stability

Firstly, the self-stacking properties of ATP4- and the effects of metal ions and protons on these properties are described. Some examples involving macrochelate formation between phosphate-coordinated metal ions (M2+) and N7 of the adenine residue in MATP2- are discussed, and this is followed by considerations on mixed ligand complexes consisting of ATP4-, M2+, and amino acid anions with side chains that allow either aromatic-ring stacking or hydrophobic interactions with the adenine moiety; this gives rise to selectivity. Next, the properties of diphosphorylated 9-[2-(phosphonomethoxy)ethyl]adenine (PMEA2-; Adefovir), i.e., of PMEApp4-, are compared with those of (2'-deoxy)ATP4- with regard to their metal ion-binding qualities, and in this way it can be explained why PMEApp2- is initially an excellent substrate for nucleic acid polymerases. Of course, after incorporation of the PMEA residue into the growing nucleic acid chain, this is terminated and this is how PMEA exerts its antiviral properties [its bis(pivaloyloxymethyl)ester, Adefovir dipivoxil, was recently approved for use in hepatitis B therapy]. Finally, the change in free energy connected with (macro)chelate formation or intramolecular stacking interactions and the effect of a reduced dielectric constant of the solvent on the stability of complexes and their structures in solution is considered.

scholarly journals Contemplating 1,2,4-Thiadiazole-Inspired Cyclic Peptide Mimics: A Computational Investigation

2019 ◽  
Vol 72 (11) ◽  
pp. 894 ◽  
Author(s):  
Sida Xie ◽  
Paul V. Bernhardt ◽  
Lawrence R. Gahan ◽  
Craig M. Williams
Keyword(s):  
Metal Binding ◽  
Metal Ion ◽  
Cyclic Peptides ◽  
Cyclic Peptide ◽  
Computational Study ◽  
Ion Binding ◽  
Metal Ion Binding ◽  
Binding Studies ◽  
Naturally Occurring ◽  
The Stability

Marine derived cyclic peptides have inspired chemists for decades as the cavitand architecture can be compared with macrocyclic ligands, and hence easily conceived as mediators of metal-ion transport. Lissoclinamide 5 and ascidiacyclamide are two such cyclic peptides that have received much attention both for their metal ion complexation properties and biological activity; the metal ion binding properties of mimics of these two systems have been reported. Reported herein is a computational study aimed at evaluating the stability, and potential for copper(ii) ion binding by lissoclinamide 5 mimics that substitute the naturally occurring 4-carboxy-1,3-thiazole units for novel valine- and phenylalanine-derived 1,2,4-thiadiazole units. Our results suggest that one lissoclinamide 5 mimic, 1,2,4-thiadiazole (TDA)-lissoclinamide 9, may be capable of forming a complex with one CuII ion, [Cu(9-H)(H2O)]+. A complex with two CuII ions, [Cu2(9-H)(μ-OH)]2+, was also considered. These results set the stage for synthetic and experimental metal binding studies.

Properties of the Ternary (Dien)Pt(PMEA-N7) Complex Containing Diethylenetriamine (Dien) and the Antiviral 9-[2-(Phosphonomethoxy)ethyl]adenine (PMEA). Synthesis, Biological Screening, Acid-Base Behaviour, and Metal Ion-Binding in Aqueous Solution

2000 ◽  
Vol 55 (12) ◽  
pp. 1141-1152 ◽  
Author(s):  
Gunnar Kampf ◽  
Marc Sven Lüth ◽  
Jens Müller ◽  
Antonín Holý ◽  
Bernhard Lippert ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Metal Ions ◽  
Metal Ion ◽  
Ion Binding ◽  
Uv Spectrophotometry ◽  
Metal Ion Binding ◽  
Ph Titration ◽  
Complex Species ◽  
Ether Oxygen ◽  
The Stability

The synthesis of (Dien)Pt(PMEA-N7), where Dien = diethylenetriamine and PMEA2- = dianion of 9-[2-(phosphonomethoxy)ethyl]adenine, is described. No useful biological activity could be discovered for this complex which is in contrast to the known antiviral properties of PMEA itself. The acidity constants of the twofold protonated H2[(Dien)Pt(PMEA-N7)]2+ complex were determined (UV spectrophotometry and potentiometric pH titration): The release of the proton from the -P(O)2(OH)- group is only slightly affected by the N7-coordinated (Dien)Pt2+ unit, whereas the acidity of the (N1)H+ site is strongly enhanced. The stability constants of the M[(Dien)Pt(PMEA-N7)]2+ complexes with the metal ions M2+ = Mg2+, Ca2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, and Cd2+ were measured by potentiometric pH titrations in aqueous solution at 25 °C and I = 0.1 M (NaNO3). Application of previously determined straightline plots of log KM(R-PO3)M versus KH(R-PO3)H for simple phosph(on)ate ligands, R-PO32- where R represents a non-inhibiting residue without an affinity for metal ions, proves that the primary binding site of the complex-ligand, (Dien)Pt(PMEA-N7), with all the metal ions studied is the phosphonate group; in most instances the expected stability is actually reduced by about 0.4 log units due to the N7-bound (Dien)Pt2+ unit. Only for the Cu[(Dien)Pt(PMEA-N7)]2+ and the Zn[(Dien)Pt(PMEA-N7)]2+ systems the formation of some 5-membered chelates involving the ether oxygen atom of the -CH2-O-CH2-PO32- residue could be detected; the formation degrees are 52 ± 9% and 32 ± 14%, respectively. The metal ion-binding properties of (Dien)Pt(PMEA-N7) differ considerably from those of PMEA2-, yet they are relatively similar to those of pyrimidine-nucleoside 5'-monophosphates. The structures of the various complex species in solution are discussed and compared.

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