scholarly journals Interaction of phenylthiolato-(2,2′,2′′-terpyridine)platinum(II) cation with DNA

1984 ◽  
Vol 222 (1) ◽  
pp. 203-215 ◽  
Author(s):  
L P G Wakelin ◽  
W D McFadyen ◽  
A Walpole ◽  
I A G Roos
Keyword(s):  
Base Pair ◽  
Equilibrium Dialysis ◽  
Platinum Complexes ◽  
Nucleotide Composition ◽  
Contour Length ◽  
Ligand Molecule ◽  
Experimental Conditions ◽  
Kinetic Measurements ◽  
Binding Isotherms ◽  
Scatchard Plots

The interaction between a novel aromatic thiolato derivative from the family of DNA-intercalating platinum complexes, phenylthiolato-(2,2′,2″-terpyridine)platinum(II)-[PhS(ter py)Pt+], and nucleic acids was studied by using viscosity, equilibrium-dialysis and kinetic measurements. Viscosity measurements with sonicated DNA provide direct evidence for intercalation, and show that at binding ratios below 0.2 molecules per base-pair PhS(terpy)Pt+ causes an increase in contour length of 0.2 nm per bound molecule. However, helix extension diminishes at greater extents of binding, indicating the existence of additional, non-intercalated, externally bound forms of the ligand. The ability of PhS(terpy)Pt+ to aggregate in neutral aqueous buffers at a range of ionic strengths and temperatures was assessed by using optical-absorption methods. Scatchard plots for binding to calf thymus DNA at ionic strength 0.01 (corrected for dimerization) are curvilinear, concave upward, providing further evidence for two modes of binding. The association constant decreases at higher ionic strengths, in accord with the expectations of polyelectrolyte theory, although the number of cations released per bound unipositive ligand molecule is substantially greater than 1. Stopped-flow kinetic measurements confirm the complexity of the binding reaction by revealing multiple bound forms of the ligand whose kinetic processes are both fast and closely coupled. Thermal denaturation of DNA radically alters the shapes of binding isotherms and either has little effect on, or enhances, the affinity of potential binding sites, depending on experimental conditions. Scatchard plots for binding to natural DNA species with differing nucleotide composition show that the ligand has a requirement for a single G X C base-pair at the highest-affinity intercalation sites.

scholarly journals The binding of binuclear platinum(II)-terpyridine complexes to DNA

1987 ◽  
Vol 242 (1) ◽  
pp. 177-183 ◽  
Author(s):  
W D McFadyen ◽  
L P Wakelin ◽  
I A G Roos ◽  
B L Hillcoat
Keyword(s):  
Optical Absorption ◽  
Base Pair ◽  
Base Composition ◽  
Association Constant ◽  
Equilibrium Dialysis ◽  
Association Constants ◽  
Ligand Molecule ◽  
Aqueous Buffer ◽  
Scatchard Plots ◽  
Polyelectrolyte Theory

The binding of platinum (II)-terpyridine complexes to DNA was studied by using equilibrium dialysis. Optical absorption methods were used to measure the ability of the ligands to aggregate in aqueous buffer. Scatchard plots for the binding of the monomeric [Pt(terpy)SC4H9]+ cation to DNA at I0.01 are curvilinear, concave upwards, suggesting two modes of binding. The association constant decreases at higher ionic strengths, consistent with polyelectrolyte theory, and 1.1 cations are released per bound ligand molecule. The association constants of the binuclear ligands [Pt(terpy)S[CH2]4S(terpy)Pt]2+ and [Pt(terpy)S[CH2]6S(terpy)Pt]2+ are 8 and 23 times larger respectively than the affinity of the monomer. For the latter binuclear derivative the increase may be ascribed to bifunctional reaction. Differential dialysis experiments with DNAs of differing base composition show that [Pt(terpy)SC4H9]+ has a requirement for a single G X C base-pair at the highest-affinity site. However, in the binuclear ligands chromophore specificity is severely compromised. Similar experiments indicate that 9-aminoacridine and selected methylene-linked diacridines show no significant sequence selectivity.

scholarly journals Investigations of ternary complexes of Co(II) and Ni(II) with thiodiacetate anion and 1,10-phenanthroline or 2,2’-bipyridine in aqueous solutions

2014 ◽  
Vol 13 (1) ◽  
Author(s):  
Dariusz Wyrzykowski ◽  
Joanna Pranczk ◽  
Dagmara Jacewicz ◽  
Aleksandra Tesmar ◽  
Bogusław Pilarski ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Substitution Reactions ◽  
Experimental Conditions ◽  
Kinetic Measurements ◽  
Hydroxo Complexes ◽  
Binary Complexes ◽  
Vis Spectroscopy ◽  
Potentiometric Titration Method ◽  
The Stability ◽  
Ph Range

AbstractA potentiometric titration method (PT) and a stopped-flow kinetic technique monitored by a UV−Vis spectroscopy have been used to characterize the stability of series of Co(II)- and Ni(II)-thiodiacetato complexes, M(TDA), in the presence of 1,10-phenanthroline (phen) or 2,2’-bipyridine (bipy) in aqueous solutions. The stability constants of the binary (1:1), ternary (1:1:1) as well as the resulting hydroxo complexes were evaluated and compared to the corresponding oxydiacetate complexes. Based on the species distribution as a function of pH the relative predominance of the species in the system over a pH range was discussed. Furthermore, the kinetic measurements of the substitution reactions of the aqua ligands to phen or bipy in the coordination sphere of the binary complexes M(TDA) were performed in the 288–303 K temperature range, at a constant concentration of phen or bipy and at seven different concentrations of the binary complexes (0.2–0.5 mM). The kinetic stability of the M(TDA) complexes was discussed in relation to the experimental conditions and the kind of the auxiliary ligands (phen/bipy). Moreover, the influence of the type of primary ligand (thiodiacetate/oxydiacetate) on the substitution rate of the auxiliary ligands was also compared.

Regulation of inositol 1,4,5-trisphosphate-induced Ca2+ release. I. Effect of Mg2+

1990 ◽  
Vol 258 (6) ◽  
pp. C1077-C1085 ◽  
Author(s):  
P. Volpe ◽  
B. H. Alderson-Lang ◽  
G. A. Nickols
Keyword(s):  
Dependent Manner ◽  
Differential Centrifugation ◽  
Michaelis Constant ◽  
Experimental Conditions ◽  
Concentration Dependent Manner ◽  
Apparent Affinity ◽  
Inositol 1,4,5 Trisphosphate ◽  
Noncompetitive Inhibitor ◽  
Scatchard Plots ◽  
Microsomal Pellet

Canine cerebellar membranes were fractionated by differential centrifugation into a crude mitochondrial pellet (P2) and a crude microsomal pellet (P3). The effect of Mg2+ on inositol 1,4,5-trisphosphate (IP3)-induced Ca2+ release and [3H]IP3 binding was assessed. Mg2+ inhibited IP3-induced Ca2+ release in a concentration-dependent manner. Mg2+ influenced both the extent of IP3-induced Ca2+ release and the apparent affinity for IP3. A 10-fold change of free Mg2+ (from approximately 30 to approximately 300 microM) reduced the extent of Ca2+ release by two- to threefold and shifted the apparent Michaelis constant from approximately 0.5 to approximately 0.9 microM IP3. Thus Mg2+ seemed to be noncompetitive inhibitor of IP3-induced Ca2+ release. Mg2+ also inhibited Ca2+ release elicited by glycerophosphoinositol 4,5-bisphosphate, a poorly metabolized analogue of IP3. Mg2+ and heparin sodium were shown to be additive inhibitors of IP3-induced Ca2+ release. Mg2+ inhibited [3H]IP3 binding under experimental conditions designed to minimize IP3 hydrolysis. Scatchard plots indicated that 0.5 mM free Mg2+ reduced maximum binding from 10.9 to 3.5 pmol IP3 bound/mg protein and increased the dissociation constant from 136 to 227 nM. The modulation of [3H]IP3 binding and IP3-induced Ca2+ release by Mg2+ could be physiologically relevant.

Molecular Weight and the Dodecyl Sulphate Binding of a Thylakoid Membrane Polypeptide Involved in a Reaction on the Oxygen-Evolving Side of Photosystem II

1977 ◽  
Vol 32 (5-6) ◽  
pp. 384-391 ◽  
Author(s):  
Hans Craubner ◽  
Friederike Koenig
Keyword(s):  
Molecular Weight ◽  
Thylakoid Membrane ◽  
Phosphate Buffer ◽  
Equilibrium Dialysis ◽  
Sodium Dodecyl ◽  
Spherical Shape ◽  
Apparent Molecular Weight ◽  
Partial Specific Volume ◽  
Experimental Conditions ◽  
Sodium Phosphate Buffer

Abstract The molecular weight of a thylakoid membrane polypeptide with the apparent molecular weight 11 000 was determined by measurement of the sedimentation velocity, the diffusion and the ef­fective partial specific volume. The molecular weight was found to be 6300 and that of the poly-peptide-dodecyl sulphate micelle was found to be 11 200. The frictional ratio was 1.35. In ad­dition, we determined the binding of dodecyl sulphate onto the polypeptide by equilibrium dialysis. We found that 1 g polypeptide binds 0.77 g sodium dodecyl sulphate which corresponds to 17 molecules dodecyl sulphate bound per polypeptide chain. In the absence of dodecyl sulphate the polypeptide aggregates. The molecular weights of the aggregates are in 0.01 м sodium phosphate buffer pH 7.2 150 000 and in a 1 :1 mixture of 0.01 м phosphate buffer and 96% ethanol 365 000. The frictional ratios were 1.07 and 1.16 respectively which points at a spherical shape. The experimental conditions for the determination of the dodecyl sulphate binding were critically scrutinised.

Rate constants for reactions of horseradish peroxidase compounds I and II with 4-substituted arylboronic acids

1994 ◽  
Vol 72 (10) ◽  
pp. 2159-2162 ◽  
Author(s):  
Weimei Sun ◽  
Xiaoying Ji ◽  
Larry J. Kricka ◽  
H. Brian Dunford
Keyword(s):  
Horseradish Peroxidase ◽  
Rate Constants ◽  
Compound I ◽  
Arylboronic Acid ◽  
Experimental Conditions ◽  
Kinetic Measurements ◽  
Arylboronic Acids ◽  
Total Ionic Strength ◽  
Compound Ii ◽  
Catalyzed Oxidation

The rate constants for the reactions of horseradish peroxidase compound I (k1) and compound II (k2) with three 4-substituted arylboronic acids, which enhance chemiluminescence in the horseradish peroxidase catalyzed oxidation of luminol by hydrogen peroxide, were determined at pH 8.6, total ionic strength 0.11 M, using stopped-flow kinetic measurements. For comparison, the rate constants of the reactions of 4-iodophenol with compounds I and II were also determined under the same experimental conditions. The three arylboronic acid derivatives and their rate constants are: 4-biphenylboronic acid, k1 = (1.21 ± 0.08) × 106 M−1 s−1, k2 = (4.6 ± 0.2) × 105 M−1 s−1; 4-bromophenylboronic acid, k1 = (5.5 ± 0.2) × 104 M−1 s−1, k2 = (3.6 ± 0.2) × 104 M−1 s−1; and 4-iodophenylboronic acid, k1 = (1.1 ± 0.2) × 105 M−1 s−1, k2 = (1.3 ± 0.1) × 104 M−1 s−1. 4-Biphenylboronic acid, which shows comparable luminescent enhancement to 4-iodophenol, has the highest reactivity in the reduction of both compounds I and II among the three arylboronic acid derivatives tested.

Examination of the potential of copper during its dissolution in sodium hydroxide

1981 ◽  
Vol 46 (12) ◽  
pp. 3057-3062 ◽  
Author(s):  
Petr Sušinka ◽  
Milica Miadoková
Keyword(s):  
Quantitative Determination ◽  
Sodium Hydroxide ◽  
Oxygen Electrode ◽  
Quantitative Relation ◽  
Experimental Conditions ◽  
Kinetic Measurements ◽  
Crystallographic Planes ◽  
The Given ◽  
Spontaneous Reaction

Parallel to kinetic measurements, the potential of copper was monitored on the (100), (110), and (111) crystallographic planes during its spontaneous reaction in sodium hydroxide in oxygen atmosphere. A quantitative relation was obtained for the potential in dependence on the experimental conditions, indicating that unless a passivating layer of copper(II) oxide is formed on the surface, the metal does not act as an oxygen electrode. The potential change in the given medium was found to depend only on the amount of copper(I) oxide formed, obeying the relation E = (RT/nF) ln (mCu2O) + K; use was made of this relation for a quantitative determination of the growth of the copper(I) oxide layer.

Binding of Ca++ to Human Prothrombin

1975 ◽  
Author(s):  
R. Benarous ◽  
J. Elion
Keyword(s):  
Binding Sites ◽  
Equilibrium Dialysis ◽  
Specific Property ◽  
Binding Properties ◽  
Binding Ability ◽  
Ph Variation ◽  
Maximum Value ◽  
Number Of Binding Sites ◽  
Scatchard Plots

The Ca++ binding properties of human prothrombin were studied by equilibrium dialysis using 45 calcium chloride at +4° C with prothrombin concentration of about 1 mg/ml equilibrated in 0.025 M Tris HCl, 0.12 M NaCl buffer pH 7.4. Scatchard plots obtained were similar to those described by Steenflo (1973) for bovine prothrombin, suggesting a positive cooperativity in the binding of Ca++ with a maximum ratio of bound Ca++/free Ca++ of 3 moles of Ca++ bound per mole of protein.The total number of binding sites was found to be at about 7, less than 10 to 12 found for bovine prothrombin. Ca++ binding was dependent on pH variation of the buffer with a maximum value for pH 8.5. Chemical modifications of carboxyl groups of prothrombin according to Hoare and Koshland (1967) abolished the Ca++ binding ability of the molecule confirming the essential role of these residues in this specific property of prothrombin.

scholarly journals Binding of glutathione and an inhibitor to microsomal glutathione transferase

1997 ◽  
Vol 326 (1) ◽  
pp. 193-196 ◽  
Author(s):  
Tie-Hua SUN ◽  
Ralf MORGENSTERN
Keyword(s):  
Glutathione Transferase ◽  
Equilibrium Dialysis ◽  
Kinetic Studies ◽  
Phase System ◽  
Liver Protein ◽  
Two Phase ◽  
Equilibrium Partition ◽  
Binding Isotherms ◽  
Equilibrium Binding Constant ◽  
Microsomal Glutathione

Microsomal glutathione transferase is an abundant liver protein that can be activated by thiol reagents. It is not known whether the activation is associated with changed binding properties of the enzyme. Therefore the binding of GSH and an inhibitor to rat liver microsomal glutathione transferase was studied by use of equilibrium dialysis and equilibrium partition in a two-phase system. The radioactive substrate glutathione and an inhibitor (glutathione sulphonate) give hyperbolic binding isotherms with a stoichiometry of 1 mol per mol of enzyme (i.e. 1 molecule per homotrimer). Glutathione had an equilibrium binding constant of 18 μM. Competition experiments involving glutathione sulphonate showed that it could effectively displace GSH. These and kinetic studies showed that the Kd and Ki for glutathione sulphonic acid are close to 10 μM. No change in these parameters was obtained after N-ethylmaleimide activation of the enzyme. Thus activation does not result from changes in binding affinity to GSH.

scholarly journals Investigations of ternary complexes of Co(II) and Ni(II) with oxydiacetate anion and 1,10-phenanthroline or 2,2′-bipyridine in solutions

2014 ◽  
Vol 12 (1) ◽  
pp. 107-114 ◽  
Author(s):  
Dariusz Wyrzykowski ◽  
Joanna Pranczk ◽  
Dagmara Jacewicz ◽  
Aleksandra Tesmar ◽  
Bogusław Pilarski ◽  
...  
Keyword(s):  
Formation Constants ◽  
Ternary Complexes ◽  
Substitution Reactions ◽  
Constant Concentration ◽  
Experimental Conditions ◽  
Kinetic Measurements ◽  
Binary Complexes ◽  
The Stability ◽  
Kinetics Of ◽  
Complex Formation Process

AbstractPotentiometric (PT) and conductometric (CT) titration methods have been used to determine the stoichiometry and formation constants in water for a series of ternary complexes of Co(II) and Ni(II) involving the oxydiacetate anion (ODA) and 1,10-phenanthroline (phen) or 2,2′-bipyridine (bipy) ligands, namely [Co(ODA)(phen)(H2O)], [Co(ODA)(bpy)(H2O)], [Ni(ODA)(phen)(H2O)] and [Ni(ODA)(bpy)(H2O)]. The ternary complex formation process was found to take place in a stepwise manner in which the oxydiacetate ligand acts as a primary ligand and the phen or bipy ligands act as auxiliary ones. The stability of the ternary complexes formed is discussed in the relation to the corresponding binary ones. Furthermore, the kinetics of the substitution reactions of the aqua ligands in the coordination sphere of the Ni-ODA and Co-ODA complexes to phen or bipy were studied by the stopped-flow method. The kinetic measurements were performed in the 288–303 K temperature range, at a constant concentration of phen or bipy and at seven different concentrations of the binary complexes (4–7 mM). The influence of experimental conditions and the kind of the auxiliary ligands (phen/bipy) on the substitution rate was discussed.

scholarly journals N-Heterocyclic Carbene-Platinum Complexes Featuring an Anthracenyl Moiety: Anti-Cancer Activity and DNA Interaction

2019 ◽  
Vol 20 (17) ◽  
pp. 4198 ◽  
Author(s):  
Sébastien Harlepp ◽  
Edith Chardon ◽  
Mathilde Bouché ◽  
Georges Dahm ◽  
Mounir Maaloum ◽  
...  
Keyword(s):  
Optical Tweezers ◽  
Platinum Complex ◽  
Platinum Complexes ◽  
Dna Interaction ◽  
Contour Length ◽  
State Behavior ◽  
Force Microscopy ◽  
Pt Complex ◽  
Dna Strands

A platinum (II) complex stabilized by a pyridine and an N-heterocyclic carbene ligand featuring an anthracenyl moiety was prepared. The compound was fully characterized and its molecular structure was determined by single-crystal X-ray diffraction. The compound demonstrated high in vitro antiproliferative activities against cancer cell lines with IC50 ranging from 10 to 80 nM. The presence of the anthracenyl moiety on the N-heterocyclic carbene (NHC) Pt complex was used as a luminescent tag to probe the metal interaction with the nucleobases of the DNA through a pyridine-nucleobase ligand exchange. Such interaction of the platinum complex with DNA was corroborated by optical tweezers techniques and liquid phase atomic force microscopy (AFM). The results revealed a two-state interaction between the platinum complex and the DNA strands. This two-state behavior was quantified from the different experiments due to contour length variations. At 24 h incubation, the stretching curves revealed multiple structural breakages, and AFM imaging revealed a highly compact and dense structure of platinum complexes bridging the DNA strands.

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