scholarly journals Modification of glyceraldehyde 3-phosphate dehydrogenase activity by adsorption on phospholipid vesicles

1976 ◽  
Vol 159 (3) ◽  
pp. 627-631 ◽  
Author(s):  
M S Wooster ◽  
J M Wrigglesworth
Keyword(s):  
Ionic Strength ◽  
Dehydrogenase Activity ◽  
Association Constant ◽  
Phospholipid Vesicles ◽  
Kinetic Properties ◽  
Km Value ◽  
Triton X ◽  
Positively Charged ◽  
Apparent Association ◽  
Apparent Association Constant

1. The adsorption of [14C]carboxymethylated glyceraldehyde 3-phosphate dehydrogenase to negatively charged liposomes of phsphatidic acid/phosphatidylcholine (3:7, w/w) was investigated. The apparent association constant at I/2 = 60, pH 7.6, was 0.4 × 10(6)M-1. Adsorption decreased as ionic strength and pH were increased. 2. In the presence of negatively charged liposomes, the Km value for glyceraldehyde 3-phosphate of glyceraldehyde 3-phosphate dehydrogenase was increased and Vmax. decreased. In the presence of positively charged liposomes, the Km value for glyceraldehyde 3-phosphate decreased and there was no significant change in Vmax. Addition of Triton X-100 abolished the effect of both positively and negatively charged liposomes on the kinetic properties of the enzyme.

scholarly journals Synthesis and surface grafting of a β-cyclodextrin dimer facilitating cooperative inclusion of 2,6-ANS

2015 ◽  
Vol 11 ◽  
pp. 514-523 ◽  
Author(s):  
Lars W Städe ◽  
Thorbjørn T Nielsen ◽  
Laurent Duroux ◽  
Reinhard Wimmer ◽  
Kyoko Shimizu ◽  
...  
Keyword(s):  
Fluorescence Spectroscopy ◽  
Sulfonic Acid ◽  
Total Internal Reflection ◽  
Association Constant ◽  
Guest Molecule ◽  
Solid Surfaces ◽  
Surface Grafting ◽  
Cyclodextrin Dimer ◽  
Apparent Association ◽  
Apparent Association Constant

A novel β-cyclodextrin (β-CD) dimer was synthesized and surface-grafted by click chemistry onto azide-functionalized quartz surfaces in order to introduce the cooperative features of the β-CD dimer to solid surfaces. Using NMR and fluorescence spectroscopy, it is shown that the free β-CD dimer forms a 1:1 complex with the fluorescent guest molecule, 2-anilinonaphthalene-6-sulfonic acid (otherwise known not to form 1:2 complexes with parent β-CD), with an apparent association constant of 7300 M−1. Further, it is shown using total internal reflection fluorescence spectroscopy that the inclusion of the fluorescent guest into both cavities of the β-CD dimer is maintained when grafted onto a solid surface.

scholarly journals Effects of pH and ionic strength on the binding of l-tri-iodothyronine to the solubilized nuclear receptor

1985 ◽  
Vol 232 (3) ◽  
pp. 663-667 ◽  
Author(s):  
B D Wilson ◽  
W L Gent
Keyword(s):  
Ionic Strength ◽  
Nuclear Receptor ◽  
Conformational Changes ◽  
Association Constant ◽  
Receptor Site ◽  
Receptor Protein ◽  
Acidic Group ◽  
Receptor Concentration ◽  
Effects Of Ph ◽  
Apparent Association

K'A (apparent association constant) and Bmax. (total receptor concentration) describing the interaction of tri-iodothyronine (T3) and its solubilized rat liver nuclear receptor (R) are found to be moderately consistent in successive preparations, but both quantities diminished after a few days. To achieve comparability in the effects of ionic strength (I) and of pH on K'A and Bmax, appropriate measurements have been made simultaneously on single preparations. K'A and Bmax. were found to be effectively unchanged over the range I0.05-0.60. Both parameters have been measured over the range pH 6.4-9.0 and the values of K'A analysed in terms of the 4′-OH ionization of T3 and that of a cationic acidic group, shown to require pK' = 7.6. This group could be identified either with the terminal alpha-NH3+ of T3 or with a group (RH+) in the receptor site. On the balance of evidence the first possibility is the more likely, in which case the variation of Bmax. with pH is ascribed to conformational changes in the receptor protein.

scholarly journals Thiol-dependent changes in the properties of rat liver sulphotransferases

1971 ◽  
Vol 123 (3) ◽  
pp. 427-434 ◽  
Author(s):  
D. J. Barford ◽  
J. G. Jones
Keyword(s):  
Ionic Strength ◽  
Methyl Ester ◽  
Molecular Size ◽  
Degree Of Polymerization ◽  
Prolonged Storage ◽  
Kinetic Properties ◽  
Female Rat ◽  
Km Value ◽  
Low Ionic Strength ◽  
Rat Livers

1. Two enzymes (A and B) which catalyse the sulphation of p-nitrophenol and l-tyrosine methyl ester have been isolated from female rat livers. One of these enzymes (A) also catalyses the sulphation of dehydroepiandrosterone. 2. The Km values for the sulphation of p-nitrophenol and l-tyrosine methyl ester by enzyme B at pH7.5 are 1.5μm and 2.9mm respectively. 3. Enzyme B is oxidized on keeping at 0°C when the Km and Vmax. values for the sulphation of p-nitrophenol are increased approx. 200-fold and fourfold respectively. This oxidized preparation of enzyme B fails to catalyse the sulphation of l-tyrosine methyl ester. 4. When the oxidized form of enzyme B is kept at 0°C and low ionic strength then further forms of p-nitrophenol sulphotransferase are produced having even lower affinities for the sulphate acceptor. 5. The Km value for adenosine 3′-phosphate 5′[35S]-sulphatophosphate is not affected during storage of the enzyme under these conditions. 6. Prolonged storage of enzyme B at low ionic strength leads to a considerable degree of polymerization of p-nitrophenol sulphotransferase and l-tyrosine methyl ester sulphotransferase. 7. The changes in the kinetic properties and molecular size of enzyme B during storage are reversed by dithiothreitol.

BINDING OF 5α-ANDROSTANE-3α,17β-DIOL TO HUMAN PLASMA PROTEINS

1973 ◽  
Vol 57 (2) ◽  
pp. 289-298 ◽  
Author(s):  
A. F. CLARK ◽  
C. E. BIRD
Keyword(s):  
Human Plasma ◽  
Plasma Proteins ◽  
Association Constant ◽  
Equilibrium Dialysis ◽  
Paper Electrophoresis ◽  
Mean Value ◽  
Albumin Fraction ◽  
The Mean ◽  
Apparent Association ◽  
Apparent Association Constant

SUMMARY The binding of 5α-androstane-3α,17β-diol to human plasma proteins was studied by equilibrium dialysis. The mean value of 96·6% for men was significantly less than that of 97·5% for women. These values are higher than those found for 5α-dihydrotestosterone (95·0 and 97·3%, respectively) and for testosterone (92·4 and 95·3%, respectively). When the distribution of labelled steroid in the different protein fractions was studied by paper electrophoresis, male plasma showed a larger fraction of 5α-androstane-3α,17β-diol radioactivity in the albumin fraction and less in the β-globulin area than did female plasma. Similar finding were made when 5α-dihydrotestosterone was studied. No inter-α-globulin peak of radioactivity was found for 5α-androstane-3α,17β-diol and 5α-dihydrotestosterone as occurs for testosterone. Albumin binds more 5α-androstane-3α,17β-diol than 5α-dihydrotestosterone or testosterone when studied by equilibrium dialysis and this is due to a higher apparent association constant between albumin and the dihydroxysteroid.

scholarly journals Photosensitization of Colloidal SnO2Semiconductor Nanoparticles with Xanthene Dyes

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
N. Nagarajan ◽  
G. Paramaguru ◽  
G. Vanitha ◽  
R. Renganathan
Keyword(s):  
Electron Transfer ◽  
Association Constant ◽  
Strong Association ◽  
Xanthene Dyes ◽  
Time Resolved ◽  
Electron Transfer Mechanism ◽  
Fluorescence Measurements ◽  
Uv Visible ◽  
Apparent Association ◽  
Apparent Association Constant

The photochemical behavior of xanthene dyes (fluorescein, erythrosine, and eosin) with colloidal SnO2nanoparticles was probed by UV-visible, steady state, and time resolved fluorescence measurements. The prepared SnO2nanoparticles were characterized by using UV-visible and powder XRD measurements. The xanthene dyes were adsorbed on the surface of colloidal SnO2nanoparticles through electrostatic interaction. Apparent association constant (Kapp) was calculated from the relevant fluorescence data. The larger value of apparent association constant indicates a strong association between xanthene dyes and SnO2nanoparticles. The fluorescence quenching is mainly attributed to electron transfer from the excited state xanthenes to the conduction band of colloidal SnO2. The electron transfer mechanism was explained based on the Rehm-Weller equation as well as the energy level diagram.

INVERSE EFFECTS OF CORTICOSTERONE AND THYROXINE ON GLUCOCORTICOID BINDING SITES IN THE ANTERIOR PITUITARY GLAND

1978 ◽  
Vol 88 (1) ◽  
pp. 29-37 ◽  
Author(s):  
B. Koch ◽  
B. Lutz-Bucher ◽  
B. Briaud ◽  
C. Mialhe
Keyword(s):  
Thyroid Hormones ◽  
Pituitary Gland ◽  
Binding Sites ◽  
Anterior Pituitary ◽  
Association Constant ◽  
Hormonal Control ◽  
Antagonistic Effects ◽  
Striking Parallelism ◽  
Apparent Association ◽  
Apparent Association Constant

ABSTRACT The aim of this study was to determine whether pituitary glucocorticoid binding sites are under hormonal control. It was shown that corticosterone and thyroxine exerted antagonistic effects on both the transcortin-like component and true receptor present in the hypophysis: thyroid hormones, in contrast to glucocorticoids which exhibited opposite influence, increased maximum binding without affecting significantly the apparent association constant. Thus, it seems that the concentration of glucocorticoid binding sites is regulated by the glucocorticoid ligands, as well as by a different hormone. Moreover, a striking parallelism was found between plasma transcortin and pituitary transcortin-like capacity, argueing in favour of a plasma origin for this pituitary binder.

Correction of proton and Ca association constants of EGTA for temperature and ionic strength

1989 ◽  
Vol 256 (6) ◽  
pp. C1250-C1256 ◽  
Author(s):  
S. M. Harrison ◽  
D. M. Bers
Keyword(s):  
New York ◽  
Ionic Strength ◽  
Association Constant ◽  
Association Constants ◽  
Tetraacetic Acid ◽  
Critical Stability ◽  
Skinned Muscle ◽  
Skinned Muscle Fibers ◽  
Complex Solutions ◽  
Apparent Association

The association constants of ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) for protons and Ca can be used to calculate the apparent association constant of EGTA for Ca (K'CaEGTA). This value is often used in calculating the free [Ca2+] of complex solutions such as those used to determine the Ca sensitivity of skinned muscle fibers. As association constants are usually measured at 0.1 M ionic strength and between 20 and 25 degrees C, these constants must first be adjusted for conditions different from those at which they were measured, before calculation of K'CaEGTA. The proton and Ca association constants (and their delta H values) from A. E. Martell and R. M. Smith (Critical Stability Constants, New York: Plenum, vol. 1, 1974) adjusted for ionic strength and temperature using a semiempirical Debye-Huckel formalism and Van't Hoff isochore, respectively, closely describe the influence of both ionic strength and temperature on K'CaEGTA. Errors in the adjustment or calculation of association constants can dramatically affect the calculated value of K'CaEGTA and hence the calculated free [Ca2+] of complex solutions, such as those used to mimic the intracellular environment.

scholarly journals Association Constant of Acetic Acid in 1.02 m NaCl Aqueous Medium at Elevated Temperatures and Pressures

1987 ◽  
Vol 42 (8) ◽  
pp. 849-852
Author(s):  
P. Becker ◽  
B. A. Bilal
Keyword(s):  
Aqueous Solution ◽  
Acetic Acid ◽  
Association Constant ◽  
Elevated Temperatures ◽  
Concentration Cell ◽  
Pressure Concentration ◽  
Increasing Temperature ◽  
Apparent Association ◽  
High Temperature High Pressure ◽  
Apparent Association Constant

The association constant of acetic acid in 1.02 m (NaCl) aqueous solution has been determined potentiometrically at temperatures up to 260 °C and pressures up to 1005 bar. A high-temperature high-pressure concentration cell having two hydrogen electrodes has been used for the measurement. The apparent association constant Q′HAC increases with increasing temperature but decreases with increasing pressure: (Q′HAC)25 ° C, 108 bar = 2.86 · 104, (Q′HAC)25 ° C , 500bar = 2.7 · 104, (Q′HAC)200 °C, 500 bar = 4.65 · 104, (Q′HAC)26O °C, 1005 bar = 6.57 · 104 m−1.

scholarly journals Characterization of a Solvent-Tolerant Amidohydrolase Involved in Natural Product Heterocycle Formation

Catalysts ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 892
Author(s):  
Lea Winand ◽  
Dustin Joshua Vollmann ◽  
Jacqueline Hentschel ◽  
Markus Nett
Keyword(s):  
Natural Product ◽  
Metal Ion ◽  
Building Blocks ◽  
Maximal Activity ◽  
Kinetic Properties ◽  
Pharmaceutical Drugs ◽  
Highly Active ◽  
Km Value ◽  
Amidohydrolase Superfamily ◽  
Solvent Tolerant

Heterocycles are important building blocks in pharmaceutical drugs and their enzymatic synthesis is attracting increasing interest. In recent years, various enzymes of the amidohydrolase superfamily were reported to catalyze heterocycle-forming condensation reactions. One of these enzymes, MxcM, is biochemically and kinetically characterized in this study. MxcM generates an imidazoline moiety in the biosynthesis of the natural product pseudochelin A, which features potent anti-inflammatory properties. The enzyme shows maximal activity at 50 °C and pH 10 as well as a kcat/Km value of 22,932 s−1 M−1 at its temperature optimum. Experimental data suggest that the activity of MxcM does not depend on a catalytic metal ion, which is uncommon among amidohydrolases. MxcM is highly active in diverse organic solvents and concentrated salt solutions. Furthermore, we show that MxcM is also capable to introduce imidazoline rings into derivatives of its natural substrate myxochelin B. Overall, MxcM is a solvent-stable, halotolerant enzyme with promising biochemical and kinetic properties and, in future, might become a valuable biocatalyst for the manufacturing of pharmaceutical drugs.

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