Monomer Shift, Dimer Shift and Dimerization Constant for Self-Association Determined Graphically from the NMR Dilution Shift: Pyrrolidone in CDCl3as an Example

Amphotericin B, a polyene antibiotic, self-associates in ethanol. The self-association of antibiotic has characterized by UV-visible spectroscopy. Starting from a simple dimerization model and using different methods described in literature, one determined the molar absorption coefficient of monomer, the molar absorption coefficient of dimer and the dimerization constant. The binding of amphotericin B to cholesteryl trifluoromethylphenyl-carbamate has investigated using absorbance measurements and the results have rationalized in terms of literature models, taking into account both 1:1 drug-sterol system and cooperativity effects. The binding constant of amphotericin B to cholesteryl trifluoromethylphenyl-carbamate has determined using Benesi-Hildebrand, Scott and Scatchard methods.

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The binding of porphyrins by ligandin

Biochemical Journal ◽

10.1042/bj1690509 ◽

1978 ◽

Vol 169 (3) ◽

pp. 509-516 ◽

Cited By ~ 54

Author(s):

E Tipping ◽

B Ketterer ◽

P Koskelo

Keyword(s):

Equilibrium Dialysis ◽

Hydrophobic Effect ◽

Protoporphyrin Ix ◽

Association Constants ◽

Binding Affinities ◽

Glutathione S Transferase ◽

Dimerization Constant ◽

Oestrone Sulphate ◽

Self Association ◽

Inhibition Studies

Spectrophotometric and equilibrium-dialysis measurements show that ligandin (glutathione S-transferase B, EC 2.5.1.18) binds monomeric porphyrins at a single site with association constants in the range 10(4)-10(6) litre/mol at pH 7.0. Binding affinities are paralleled by the tendencies of the porphyrins to aggregate, increasing in the order: uroporphyrins I and III less than coproporphyrins I and III approximately haematoporphyrin less than protoporphyrin IX. From this it is deduced that the hydrophobic effect is the predominant driving-force for binding. The porphyrins can be displaced from their binding site on ligandin by bromosulphophthalein and oestrone sulphate. In enzyme inhibition studies, 50% inhibition was brought about by 8 micron-haematoporphyrin and by 1 micron-protoporphyrin IX. In the analysis of the haemotoporphyrin-ligandin system the self-association of haematoporphyrin was studied in detail. It was found to be limited to dimerization in the concentration range 0-200 micron at pH 7.0, 25 degrees C and a dimerization constant of 1.9 × 10(5) litre/mol was determined. Coproporphrin III has a dimerization constant of 5.2 × 10(5) litre/mol under the same conditions.

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Measurement of self-association and ion-pair dissociation constants by solvent extraction using a membrane phase separator

Canadian Journal of Chemistry ◽

10.1139/v82-189 ◽

1982 ◽

Vol 60 (11) ◽

pp. 1286-1290 ◽

Cited By ~ 4

Author(s):

Murray Carmichael ◽

Frederick F. Cantwell

Keyword(s):

Solvent Extraction ◽

Methylene Chloride ◽

Dissociation Constants ◽

Extraction Constant ◽

Ion Pair ◽

Membrane Phase ◽

Dimerization Constant ◽

Self Association ◽

Phase Separator ◽

Extraction Isotherms

The "filter-probe" membrane phase separator is used with a gravimetric buret to obtain the following constants at 25 °C by measuring solvent-extraction isotherms: dimerization constant of benzoic acid in chloroform (log K2,HBz = 2.12 ± 0.01); "self-ion-pair extraction" constant of Naloxone into chloroform [Formula: see text]; and ion-pair dissociation constant of tetraethylammonium picrate in methylene chloride (log Kdiss = −4.52 ± 0.09).

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The Investigation of the Neopluramycin � DNA System by UV-visible Spectroscopy

Revista de Chimie ◽

10.37358/rc.08.9.1947 ◽

2008 ◽

Vol 59 (9) ◽

Author(s):

Loredana Elena V�jan

Keyword(s):

Absorption Coefficient ◽

Binding Constant ◽

The Self ◽

Molar Absorption Coefficient ◽

Water Mixture ◽

Visible Spectroscopy ◽

Dimerization Constant ◽

Calf Thymus ◽

Uv Visible ◽

Self Association

The self-association of neopluramycin and the binding of this drug to calf thymus DNA were investigated by using UV-visible spectroscopy. This classical pluramycin antibiotic self-associates in 1:1 ethanol - water mixture. Starting from a simple dimerization model, the molar absorption coefficient of monomer, the molar absorption coefficient of dimer and the dimerization constant were determined. The binding constant of neopluramycin to DNA was determined using Wolfe and Scatchard methods.

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Self-Association of the Macromolecules of Aldrich Humic Acid in Aqueous Solutions Using Ultraviolet–Visible (UV–Vis) Absorption Spectroscopy

Applied Spectroscopy ◽

10.1177/0003702819829809 ◽

2019 ◽

Vol 73 (7) ◽

pp. 810-815

Author(s):

Nikolay L. Lavrik ◽

Nikolay M. Bazhin

Keyword(s):

Aqueous Solutions ◽

Absorption Spectroscopy ◽

Spectral Dependence ◽

The Self ◽

Dimerization Constant ◽

Absorption Bands ◽

Characteristic Absorption ◽

Mathematical Algorithm ◽

The Difference ◽

Self Association

The ultraviolet–visible (UV–Vis) spectra of the aqueous solutions of humic acids (HA) Aldrich were obtained within the concentration range 1–20 mg/L (0.1–2ċ10–6 mol/L). A conclusion on the existence of the self-association (dimer formation) of HA macromolecules is based on the deviation of the concentration dependence of optical density (OD) from the linear one at [HA] > 10 mg/L (>10–6 mol/L). An original, mathematical algorithm is proposed to determine a dimerization constant K and a molar coefficient of dimer absorption [Formula: see text] The value of K was (2.56 ± 0.07) ċ 106 L/mol. The calculated molar coefficients of HA macromolecule dimer absorption, [Formula: see text], indicate an increase in the dimer extinction coefficient [Formula: see text] compared to the double value of the molar monomer absorption 2[Formula: see text]. It was established that the spectral dependence of the value β = [Formula: see text]/[Formula: see text] exhibits a minimum within a wavelength range of 300–450 nm, which is due to the difference in the efficiency of the interaction of various sites upon HA macromolecule dimerization. Thus, an approach of studying the processes of self-association is proposed using the method of UV–Vis absorption spectroscopy. This method is implemented for molecules that do not have characteristic absorption bands. The proposed method can also be successfully applied to molecules with characteristic absorption bands.

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Aggregated, Conformationally Changed Fibrinogen Exposes the Stimulating Sites for t-PA-Catalysed Plasminogen Activation

Thrombosis and Haemostasis ◽

10.1055/s-0038-1650269 ◽

1996 ◽

Vol 75 (02) ◽

pp. 326-331 ◽

Cited By ~ 7

Author(s):

Unni Haddeland ◽

Knut Sletten ◽

Anne Bennick ◽

Willem Nieuwenhuizen ◽

Frank Brosstad

Keyword(s):

Conformational Changes ◽

Gel Permeation Chromatography ◽

Tissue Type ◽

Plasminogen Activation ◽

Chromogenic Substrate ◽

Type Plasminogen Activator ◽

Gel Permeation ◽

Self Association ◽

Fibrin Monomers ◽

Stimulation Of

SummaryThe present paper shows that conformationally changed fibrinogen can expose the sites Aα-(148-160) and γ-(312-324) involved in stimulation of the tissue-type plasminogen activator (t-PA)-catalysed plasminogen activation. The exposure of the stimulating sites was determined by ELISA using mABs directed to these sites, and was shown to coincide with stimulation of t-PA-catalysed plasminogen activation as assessed in an assay using a chromogenic substrate for plasmin. Gel permeation chromatography of fibrinogen conformationally changed by heat (46.5° C for 25 min) demonstrated the presence of both aggregated and monomeric fibrinogen. The aggregated fibrinogen, but not the monomeric fibrinogen, had exposed the epitopes Aα-(148-160) and γ-(312-324) involved in t-PA-stimulation. Fibrinogen subjected to heat in the presence of 3 mM of the tetrapeptide GPRP neither aggregates nor exposes the rate-enhancing sites. Thus, aggregation and exposure of t-PA-stimulating sites in fibrinogen seem to be related phenomena, and it is tempting to believe that the exposure of stimulating sites is a consequence of the conformational changes that occur during aggregation, or self-association. Fibrin monomers kept in a monomeric state by a final GPRP concentration of 3 mM do not expose the epitopes Aα-(148-160) and γ-(312-324) involved in t-PA-stimulation, whereas dilution of GPRP to a concentration that is no longer anti-polymerizing, results in exposure of these sites. Consequently, the exposure of t-PA-stimulating sites in fibrin as well is due to the conformational changes that occur during selfassociation.

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