THE DISSOCIATION OF α- AND β-LIPOVITELLIN IN AQUEOUS SOLUTION: PART II. INFLUENCE OF PROTEIN PHOSPHATE GROUPS, SULPHYDRYL GROUPS, AND RELATED FACTORS

1962 ◽  
Vol 40 (3) ◽  
pp. 373-379 ◽  
Author(s):  
R. W. Burley ◽  
W. H. Cook
Keyword(s):  
Aqueous Solution ◽  
Complex Formation ◽  
Calcium Ions ◽  
Chromatographic Behavior ◽  
Related Factors ◽  
Sulphydryl Group ◽  
Ph Changes ◽  
Ph Values ◽  
Sulphydryl Groups ◽  
Phosphate Groups

Removal of protein phosphate groups from α- and β-lipovitellin by means of a phosphatase has shown that these groups do not take part in the dissociation–association process. They appear, however, to be responsible for a difference in their ease of complex formation with calcium ions, and also for their different chromatographic behavior on columns of hydroxyapatite.Both lipovitellins contain about 26 μmoles/g of sulphydryl groups. Sulphydryl group reagents had no effect on the dissociation of α-lipovitellin but markedly changed the behavior of β-lipovitellin. N-Ethylmaleimide and p-chloromercuribenzoate displaced the equilibrium towards the associated form at all pH values below pH 10, but iodoacetamide tended to stabilize the dissociated form against pH changes. The different behavior of these reagents indicates that the sulphydryl groups are not directly involved in the dissociation but their substitution probably causes other changes in β-lipovitellin that affect its dissociation.

THE DISSOCIATION OF α- AND β-LIPOVITELLIN IN AQUEOUS SOLUTION: PART II. INFLUENCE OF PROTEIN PHOSPHATE GROUPS, SULPHYDRYL GROUPS, AND RELATED FACTORS

1962 ◽  
Vol 40 (1) ◽  
pp. 373-379 ◽  
Author(s):  
R. W. Burley ◽  
W. H. Cook
Keyword(s):  
Aqueous Solution ◽  
Complex Formation ◽  
Calcium Ions ◽  
Chromatographic Behavior ◽  
Related Factors ◽  
Sulphydryl Group ◽  
Ph Changes ◽  
Ph Values ◽  
Sulphydryl Groups ◽  
Phosphate Groups

Removal of protein phosphate groups from α- and β-lipovitellin by means of a phosphatase has shown that these groups do not take part in the dissociation–association process. They appear, however, to be responsible for a difference in their ease of complex formation with calcium ions, and also for their different chromatographic behavior on columns of hydroxyapatite.Both lipovitellins contain about 26 μmoles/g of sulphydryl groups. Sulphydryl group reagents had no effect on the dissociation of α-lipovitellin but markedly changed the behavior of β-lipovitellin. N-Ethylmaleimide and p-chloromercuribenzoate displaced the equilibrium towards the associated form at all pH values below pH 10, but iodoacetamide tended to stabilize the dissociated form against pH changes. The different behavior of these reagents indicates that the sulphydryl groups are not directly involved in the dissociation but their substitution probably causes other changes in β-lipovitellin that affect its dissociation.

Calculation by computer of individual concentrations in a simulated milk salt solution. I

1981 ◽  
Vol 48 (1) ◽  
pp. 77-83 ◽  
Author(s):  
Geoffrey B. Wood ◽  
David S. Reid ◽  
Roger Elvin
Keyword(s):  
Ionic Strength ◽  
Complex Formation ◽  
Computer Program ◽  
Calcium Ions ◽  
Salt Solution ◽  
Salt Solutions ◽  
Ph Values ◽  
Phosphoric Acids

SummaryA modegl is proposed for the equilibria between the components of the salts in milk. The model includes complex formation between calcium ions and the various ionized forms of citric, lactic and phosphoric acids, and makes allowance for the effect of ionic strength. A computer program has been written to calculate the pH of the milk salt solutions and the concentration of each of the complexes formed. Calculated pH values agree with observed values for solutions of known composition.

scholarly journals Short Strong Hydrogen Bonds can Hinder Complex Formation: A Stability and Structure Study of Copper(II) Alkyl-N-iminodiacetic Acid Complexes in Aqueous Systems and Solid State

2021 ◽  
Author(s):  
Leif Häggman ◽  
Anders Cassel ◽  
Ingmar Persson
Keyword(s):  
Aqueous Solution ◽  
Coordination Chemistry ◽  
Solid State ◽  
Carboxylic Acid ◽  
Complex Formation ◽  
Hydrogen Bonds ◽  
Iminodiacetic Acid ◽  
Lewis Base ◽  
Polar Head ◽  
Ph Values

AbstractIn the present study the solution and coordination chemistry of copper(II)–alkyl-N-iminodiacetate systems are studied in aqueous solution by potentiometry, using ion selective copper and pH electrodes, EXAFS (extended X-ray absorption fine structure) and dye probe molecular absorption spectrophotometry. Alkyl-N-iminodiacetates with varying alkyl chain length, methyl (CH3–), n-hexyl (C6H13–), n-dodecyl (C12H25–) and n-octadecyl (C18H37–) were used to tune the amphiphilic properties of the ligands. The polar head groups have both oxygen (hard Lewis base) and nitrogen donor (border-line Lewis base) atoms. This means that metal ions with different bonding characteristics may bind these ligands differently. Furthermore, the chelating properties of the polar head group may be regulated by pH as the acid–base properties of the imine and carboxylic acid groups are different. Copper(II) forms two stable complexes with alkyl-N-iminodiacetates with short alkyl chains, present as monomers in aqueous solution, log10β1 = 11.10(2), log10β2 = 19.5(2) for methyl-N-iminodiacetate, and log10β1 = 12.22(4), log10β2 = 21.9(2) for n-hexyl-N-iminodiacetate. n-Octadecyl-N-iminodiacetic acid, present as large aggregates in acidic aqueous solution, has short strong hydrogen bonds between carboxylic acid and carboxylate groups in the surface of the aggregates, which hinder complex formation at pH values below 4, obstructs it in the pH region 4–7, while the complex formation behaves as for short-chained alkyl-N-iminodiacetates at pH > 7. The structure around copper in copper(II)–alkyl-N-iminodiacetate complexes in aqueous solution and solid state formed at different pH values and copper(II):alkyl-N-iminodiacetate ratios has been determined by EXAFS. The coordination chemistry of copper(II) shows four strong bonds in the equatorial plane, and two different Cu–O/N bond distances, ca. 0.2 Å apart, in the axial positions of a non-centrosymmetric tetragonally elongated octahedron.

scholarly journals Wechselwirkung des Vanadyl(IV)-Kations mit Nucleotiden in wäßriger Lösung / Interaction of the Vanadyl(IV) Cation with Nucleotides in Aqueous Solution

1987 ◽  
Vol 42 (12) ◽  
pp. 1537-1542 ◽  
Author(s):  
G. Urretavizcaya ◽  
E. J. Baran
Keyword(s):  
Aqueous Solution ◽  
Coordination Sphere ◽  
Oh Groups ◽  
High Ph ◽  
Preferential Interaction ◽  
Ph Values ◽  
Direct Measurements ◽  
Phosphate Groups

AbstractThe interaction of VO2+ with mono-, di- and trinucleotides and with some of the related nucleosides and bases, was investigated spectrophotometrically at pH = 4.9. The results point to a preferential interaction of the cation with the phosphate groups of all the nucleotides whereas no interaction with the nucleosides and bases was detected. The vanadyl coordination sphere shows some distortive effects in the case of mononucleotides whereas it appears more regular in the case of di- and trinucleotides. At high pH-values the cation interacts with the deprotonated OH-groups of the ribose moieties. This type of interaction was confirmed by direct measurements with pure ribose and ribose-5′-phosphate, and it was absent in the case of thymidine nucleotides, in which ribose is replaced by 2′-deoxyribose.

A novel nanogel-based fluorescent probe for ratiometric detection of intracellular pH values

2014 ◽  
Vol 50 (63) ◽  
pp. 8787-8790 ◽  
Author(s):  
Lixia Cao ◽  
Xiaoyan Li ◽  
Shuangqing Wang ◽  
Shayu Li ◽  
Yi Li ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Fluorescent Probe ◽  
Intracellular Ph ◽  
Living Cells ◽  
Fluorescent Detection ◽  
Hypsochromic Shift ◽  
Ph Changes ◽  
Ph Values ◽  
Ratiometric Detection ◽  
Cytosol Ph

A new nanogel indicator (NGI) for ratiometric fluorescent detection of intracellular pH values has been reported. In aqueous solution, the NGI can be used for ratiometric sensing of pH changes with a large hypsochromic shift of 100 nm in the green–red region and reversible. Furthermore, the NGI has been used to calibrate the cytosol pH in living cells.

The Effect of Agonists and Antagonists of Platelet Aggregation on von Willebrand Factor-Mediated Platelet Agglutination

1991 ◽  
Vol 65 (05) ◽  
pp. 573-577 ◽  
Author(s):  
Jean McPherson ◽  
Marjorie B Zucker ◽  
Evelyn A Mauss ◽  
Sandra Brownlea
Keyword(s):  
Receptor Antagonist ◽  
Intracellular Calcium ◽  
Calcium Ions ◽  
Inhibitory Action ◽  
Platelet Rich Plasma ◽  
Cytoskeletal Proteins ◽  
A 23187 ◽  
Sulphydryl Groups ◽  
Affinity Receptor ◽  
Adp Receptor

SummaryRistocetin-induced platelet agglutination (RIPA) in EDTA-treated citrated platelet-rich plasma was reduced to 49 ± 11% by 1.25 ΜM ADP, 41 ± 14% by 1 ΜM A 23187, and 26 ± 7% by 0.1 Μg/ml platelet activating factor (PAF). The effect of 5-110 ΜM epinephrine was not dose-dependent, but varied between donors, with RIPA from 56-100% of the control. The inhibitory effects of these agonists were not altered by prior treatment of platelets with aspirin. Prior addition of 200 ΜM ATP (an ADP receptor antagonist acting at both high and low affinity ADP receptors) prevented the inhibitory action of ADP but not that of A 23187 or PAF, suggesting that the inhibitory actions of the latter are not mediated by released ADP. As 700 ΜM 8-bromoadenosine 5-diphosphate (an ADP receptor antagonist acting mainly at the high affinity receptor) did not prevent ADP-induced inhibition of RIPA, interaction of ADP with the low affinity receptor is presumably responsible for its inhibitory action. As A 23187, but not phorbol myristate acetate (0.1 ΜM) inhibited RIPA, an increase in intracellular calcium ions rather than direct stimulation of protein kinase C appears to mediate agonist-induced inhibition. Cytochalasin B (10.5-21 ΜM), dibucaine (0.5-1 mM), and prostaglandin E1 (25 nM), added before or after the agonist, prevented or reversed ADP-, A23187-, and PAF-induced inhibition of RIPA, suggesting that the state of the platelet cytoskeleton affects inhibition. N-ethylmaleimide (0.25-0.5 mM), an agent that can penetrate cell membranes and block sulphydryl groups, prevented or reversed ADP, A 23187- and PAF-induced inhibition of RIPA, but 0.5 mM dithionitrobisbenzoic acid, a non-penetrating sulphydryl blocker, had no effect. Diamide (0.1-0.5 mM), an agent that can crosslink cytoskeletal proteins by oxidation of sulphydryl groups, reduced RIPA. Thus an increase in intracellular calcium ions with resultant cytoskeletal changes and reorganisation of intracellular sulphydryl groups may mediate the inhibitory action of agonists on RIPA.

Phospholipid-Protein Interactions in the Formation of Prothrombin Activator

1965 ◽  
Vol 14 (03/04) ◽  
pp. 431-444 ◽  
Author(s):  
E. R Cole ◽  
J. L Koppel ◽  
J. H Olwin
Keyword(s):  
Complex Formation ◽  
Protein Interactions ◽  
Calcium Ions ◽  
Fixed Number ◽  
Factor V ◽  
Clotting Factors ◽  
Number Of Binding Sites ◽  
C Complex ◽  
Autoprothrombin C

SummarySince Ac-globulin (factor V) is involved in the formation of prothrombin activator, its ability to complex with phospholipids was studied. Purified bovine Ac-globulin was complexed to asolectin, there being presumably a fixed number of binding sites on the phospholipid micelle for Ac-globulin. In contrast to the requirement for calcium ions in the formation of complexes between asolectin and autoprothrombin C, calcium ions were not required for complex formation between asolectin and Ac-globulin to occur ; in fact, the presence of calcium prevented complex formation occurring, the degree of inhibition being dependent on the calcium concentration. By treating isolated, pre-formed aso- lectin-Ac-globulin complexes with calcium chloride solutions, Ac-globulin could be recovered in a much higher state of purity and essentially free of asolectin.Complete activators were formed by first preparing the asolectin-calcium- autoprothrombin C complex and then reacting the complex with Ac-globulin. A small amount of this product was very effective as an activator of purified prothrombin without further addition of calcium or any other cofactor. If the autoprothrombin C preparation used to prepare the complex was free of traces of prothrombin, the complete activator was stable for several hours at room temperature. Stable preparations of the complete activator were centrifuged, resulting in the sedimentation of most of the activity. Experimental evidence also indicated that activator activity was highest when autoprothrombin C and Ac-globulin were complexed to the same phospholipid micelle, rather than when the two clotting factors were complexed to separate micelles. These data suggested that the in vivo prothrombin activator may be a sedimentable complex composed of a thromboplastic enzyme, calcium, Ac-globulin and phospholipid.

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