scholarly journals Interactions of calcium and other metal ions with caldolysin, the thermostable proteinase from Thermus aquaticus strain T351

1984 ◽  
Vol 221 (2) ◽  
pp. 407-413 ◽  
Author(s):  
T C Khoo ◽  
D A Cowan ◽  
R M Daniel ◽  
H W Morgan
Keyword(s):  
Metal Ions ◽  
Binding Sites ◽  
Binding Free Energy ◽  
Binding Constants ◽  
Lanthanide Ions ◽  
Extreme Thermophile ◽  
Extracellular Proteinase ◽  
Thermus Aquaticus ◽  
Different Types ◽  
Thermostable Proteinase

Caldolysin, the extracellular proteinase from the extreme thermophile Thermus aquaticus strain T351, is stabilized by Ca2+. A variety of metal ions were able to substitute for Ca2+. Most were unable to confer as much stability as Ca2+, with the exception of the lanthanide ions, which increased the half-life at 95 degrees C from 1 h to more than 4 h. Results from a variety of separation methods indicated that caldolysin binds 6 Ca2+ ions/molecule of enzyme. The presence of non-linear Ca2+ titration plots, and the removal of 4 Ca2+ ions/molecule by treatment with a cationic ion-exchange gel suggested that caldolysin possesses at least two different types of Ca2+-binding sites, with different affinities. Average binding constants of the two types of binding sites were 2.8×10(4)M-1 (for the low-affinity sites) and 7.5×10(5) M-1 (for the high-affinity sites). The total Ca2+-binding free energy for caldolysin was shown to be greater than for either thermolysin or Bacillus subtilis neutral proteinase. It appears that the higher thermostability of caldolysin is due to the presence of 6 Ca2+ ions rather than 4 Ca2+ ions/molecule.

scholarly journals The binding of cupric ions to bovine pancreatic ribonuclease studied with diligand metal-ion buffers

1967 ◽  
Vol 105 (1) ◽  
pp. 107-115 ◽  
Author(s):  
R. H. Saundry ◽  
W D Stein
Keyword(s):  
Enzyme Activity ◽  
Metal Ions ◽  
Binding Sites ◽  
Metal Ion ◽  
Equilibrium Dialysis ◽  
Binding Constants ◽  
Pancreatic Ribonuclease ◽  
Dialysis Technique

A procedure has been developed for the use of metal-ion buffers that depends on the formation of 2:1 complexes between suitable chelators and metal ions. β-Alanine has been used as the chelator for Cu2+ ions in a study of Cu2+ binding by bovine pancreatic ribonuclease by the equilibrium-dialysis technique at pH7·0, 6·1 and 5·2. The results indicated the presence of two avid binding sites, the more avid group being implicated in the inhibition of enzyme activity by Cu2+ ions. The binding constants of the more avid site were 2·97×107, 7·97×105 and 1·25×104 at pH7·0, 6·1 and 5·2 respectively, and the binding constants of the less avid site were 5·27×106 and 1·71×105 at pH7·0 and 6·1 respectively. The data show that the Cu2+ is chelated to the protein through at least two ligand groups on the ribonuclease molecule.

Titration Simulations for Understanding of the Binding Equilibrium

2020 ◽  
Author(s):  
Dae Hyup Sohn
Keyword(s):  
Equilibrium Model ◽  
Binding Sites ◽  
Binding Constants ◽  
Reliability Evaluation ◽  
Binding Isotherm ◽  
Guest Chemistry

<p>The reliability evaluation of the predicted binding constants in numerous models is also a challenge for supramolecular host-guest chemistry. Here, I briefly formulate binding isotherm with the derivation of the multivalent equilibrium model for the chemist who wants to determine the binding constants of their compounds. This article gives an in-depth understanding of the stoichiometry of binding equilibrium to take divalent binding equilibria bearing two structurally identical binding sites as an example. The stoichiometry of binding equilibrium is affected by (1) the cooperativity of complex, (2) the concentration of titration media, and (3) the equivalents of guests. The simulations were conducted with simple Python codes.</p>

(Thio)Urea-Functionalized Cavitands as Excellent Receptors for Organic Anions in Polar Media

2004 ◽  
Vol 69 (5) ◽  
pp. 1137-1148 ◽  
Author(s):  
Gennady V. Oshovsky ◽  
Willem Verboom ◽  
David N. Reinhoudt
Keyword(s):  
Binding Sites ◽  
Binding Constants ◽  
Organic Anions ◽  
Isothermal Microcalorimetry ◽  
Polar Media

Ureidocavitand 1 and thioureidocavitand 2 bind in CH3CN organic anions such as acetate, propionate, butyrate, etc. with K values of 2-8 × 105 l mol-1 and 2-9 × 106 l mol-1, respectively, as was determined with isothermal microcalorimetry (ITC). Bringing together four (thio)urea binding sites on a molecular platform gives rise to about 2000 times higher binding constants, compared with those of the corresponding single binding sites. Glucose- and galactose-containing thioureidocavitands 5 and 6 bind acetate in 1:1 CH3CN/water with a K-value of 2.15 × 103 l mol-1.

Movement of Calcium Ions and their Role in the Activation of Platelets

1978 ◽  
Vol 40 (02) ◽  
pp. 212-218 ◽  
Author(s):  
P Massini ◽  
R Käser-Glanzmann ◽  
E F Lüscher
Keyword(s):  
Plasma Membrane ◽  
Platelet Activation ◽  
Calcium Ions ◽  
Binding Sites ◽  
Shape Change ◽  
Release Reaction ◽  
Dense Bodies ◽  
Activated Platelets ◽  
Different Types ◽  
Ca Ions

SummaryThe increase of the cytoplasmic Ca-concentration plays a central role in the initiation of platelet activation. Four kinds of movements of Ca-ions are presumed to occur during this process: a) Ca-ions liberated from membranes induce the rapid shape change, b) Vesicular organelles release Ca-ions into the cytoplasm which initiate the release reaction, c) The storage organelles called dense bodies, secrete their contents including Ca-ions to the outside during the release reaction, d) At the same time a rearrangement of the plasma membrane occurs, resulting in an increase in its permeability for Ca-ions as well as in an increase in the number of Ca-binding sites.Since most processes occurring during platelet activation are reversible, the platelet must be equipped with a mechanism which removes Ca-ions from the cytoplasm. A vesicular fraction obtained from homogenized platelets indeed accumulates Ca actively. This Ca- pump is stimulated by cyclic AMP and protein kinase; it may be involved in the recovery of platelets after activation.It becomes increasingly clear that the various manifestations of platelet activation are triggered by a rise in the cytoplasmic Ca2+-concentration. The evidence for this and possible mechanisms involved are discussed in some detail in the contributions by Detwiler et al. and by Gerrard and White to this symposium. In this article we shall discuss four different types of mobilization of Ca-ions which occur in the course of the activation of platelets. In addition, at least one transport step involved in the removal of Ca2+ must occur during relaxation of activated platelets.

The influence of metal-ion binding on the structure and surface composition of Sonic Hedgehog: a combined classical and hybrid QM/MM MD study

2016 ◽  
Vol 18 (32) ◽  
pp. 22254-22265 ◽  
Author(s):  
Manuel Hitzenberger ◽  
Thomas S. Hofer
Keyword(s):  
Metal Ions ◽  
Sonic Hedgehog ◽  
Binding Sites ◽  
Metal Ion ◽  
Surface Composition ◽  
Quantum Mechanical ◽  
Ion Binding ◽  
Metal Ion Binding ◽  
Structural Impact

The interaction of metal ions with Shh binding-sites and their structural impact are assessed via classical and quantum mechanical simulations.

A comparison of cobalamin binding by liver and kidney in rat and man

1985 ◽  
Vol 68 (3) ◽  
pp. 357-364 ◽  
Author(s):  
J. S. D. Scott ◽  
E. P. W. Bowman ◽  
W. G. E. Cooksley
Keyword(s):  
Binding Sites ◽  
Plasma Membranes ◽  
Competitive Inhibition ◽  
Rat Kidney ◽  
Binding Constants ◽  
Human Kidney ◽  
Specific Adsorption ◽  
Receptor Protein ◽  
Mean Values ◽  
Liver And Kidney

1. Binding of cobalamin (Cbl) was compared in liver and kidney plasma membranes prepared from rat and human tissues. 2. Single, high-affinity, saturable (200 pmol/l), binding sites for TC II-Cbl were found in all tissues; by contrast no receptors were present for free cobalamin, for which only non-specific adsorption occurred. 3. Binding constants for TC II-CNCbl determined for liver and kidney plasma membranes were of a similar magnitude. Mean values for Ka (litre/nmol) were 16.7 (rat liver), 18.8 (rat kidney), 8.0 (human liver) and 7.5 (human kidney). 4. Results for binding TC II-OHCbl instead of TC II-CNCbl showed no difference in Ka and Bmax. values, although the non-specific adsorption was decreased to a third. 5. Competitive inhibition results showed that the receptors are specific for the TC II molecule and that binding is unaffected either by the cobalamin moiety or by the presence of free cobalamin. Degradation of the receptor protein molecules by trypsin (10 μg/ml) resulted in 90% inhibition of binding. 6. It is concluded that differences between liver and kidney in cobalamin uptake and accumulation cannot be attributed to differences in their TC II receptors.

scholarly journals The structural chemistry of zinc(ii) and nickel(ii) dithiocarbamate complexes

2021 ◽  
Vol 19 (1) ◽  
pp. 974-986
Author(s):  
Tanzimjahan A. Saiyed ◽  
Jerry O. Adeyemi ◽  
Damian C. Onwudiwe
Keyword(s):  
Complex Formation ◽  
Metal Ions ◽  
Structural Properties ◽  
Binding Sites ◽  
Biological Systems ◽  
Structural Chemistry ◽  
Metal Coordination ◽  
Nickel Ions ◽  
Coordination Modes ◽  
Biomedical Fields

Abstract Dithiocarbamate complexes are of immense interest due to their diverse structural properties and extensive application in various areas. They possess two sulfur atoms that often act as the binding sites for metal coordination in a monodentate, bidentate, or anisodentate fashion. These different coordination modes enhance the possibility for complex formation and make them useful in different areas especially in biomedical fields. A synergy exists in the metal ions and dithiocarbamate moieties, which tends to exert better properties than the respective individual components of the complex. These improved properties have also been attributed to the presence of the C–S bonds. Zinc and nickel ions have been majorly found to bind to the dithiocarbamate in bidentate modes, and consequently different geometries have resulted from this interaction. The aim of this review is to present some studies on the synthesis, structural chemistry, and the relevance of zinc and nickel dithiocarbamates complexes especially in biological systems.

A systematic series of fluorescence chemosensors with multiple binding sites for Hg(ii) based on pyrenyl-functionalized cyclotriphosphazenes and their application in live cell imaging

2018 ◽  
Vol 42 (17) ◽  
pp. 14219-14228 ◽  
Author(s):  
Süreyya Oğuz Tümay ◽  
Aylin Uslu ◽  
Hüsniye Ardıç Alidağı ◽  
Hasan Hüseyin Kazan ◽  
Cansu Bayraktar ◽  
...  
Keyword(s):  
Metal Ions ◽  
Binding Sites ◽  
Live Cell Imaging ◽  
Cell Imaging ◽  
Live Cell ◽  
Multiple Binding Sites ◽  
Multiple Binding

A systematic series of fluorescence chemosensors based on cyclotriphosphazene derivatives were designed, synthesized, and evaluated for their sensing behaviors toward metal ions.

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