The interaction of sialidase-treated hCG with ovarian cellular membranes

1981 ◽  
Vol 97 (2) ◽  
pp. 270-280 ◽  
Author(s):  
E. C. Brand ◽  
J. Odink ◽  
G. Klok ◽  
E. V. van Hall
Keyword(s):  
Binding Sites ◽  
Association Constant ◽  
Apparent Difference ◽  
Receptor Complexes ◽  
Number Of Binding Sites ◽  
Biological Potency ◽  
The Difference ◽  
The Stability ◽  
Dissociation Curves ◽  
Hcg Receptor

Abstract. The potency of human chorionic gonadotrophin (hCG) in competition for binding to a gonadal membrane fraction is remarkably enhanced by sialidase treatment. The present study was undertaken to investigate the specificity and characteristics of the binding of sialidase-treated hCG (asialo-hCG) in a particulate hCG-binding system from luteinized rat ovaries. The competitive potency of asialo-hCG relative to hCG was 2.5, irrespective of whether [125I]hCG or [125I]asialo-hCG was used for tracer. This was due to a 2.1 times higher equilibrium association constant for asialo-hCG, whereas the estimated number of binding sites did not differ. There was no apparent difference in the stability of hCG and asialo-hCG, or in the stability of the respective hormone-receptor complexes. The effect of variation of the incubation conditions on the binding of both tracers was similar. In accordance with the difference in the equilibrium association constant, the association velocity of asialo-hCG was more than double that of hCG. With all of the tracers used the dissociation curves were biphasic, the size of the initial fast-dissociating fraction being inversely related to the pre-incubation time. Under identical conditions, the fast-dissociating fraction was smaller for the [125I]asialo-hCG complex than for the [125I]hCG complex. The dissociation velocities of these fractions appeared to be similar. The results indicate that asialo-hCG binds to the hCG receptor in a way similar to the binding of the unmodified hormone, but with a higher affinity. The smaller size of the fast-dissociation form of the asialo-hCG-receptor complex may be related to the lower biological potency of the hormone derivative.

THE LH-hCG RECEPTOR OF HUMAN OVARY AT VARIOUS STAGES OF THE MENSTRUAL CYCLE

1975 ◽  
Vol 79 (3) ◽  
pp. 568-576 ◽  
Author(s):  
S. Wardlaw ◽  
N. H. Lauersen ◽  
B. B. Saxena
Keyword(s):  
Menstrual Cycle ◽  
Binding Sites ◽  
Receptor Site ◽  
Binding Activity ◽  
Corpora Lutea ◽  
Human Ovary ◽  
Slow Decline ◽  
Number Of Binding Sites ◽  
Human Ovaries ◽  
Hcg Receptor

ABSTRACT Receptors specific for hCG were found in human corpora lutea and follicles. hCG and LH were found to bind at a similar receptor site. The dissociation constant for hCG ranged from 10−10 to 10−11 mol/l in human corpora lutea. The number of binding sites for 125I-hCG ranged from 10−14 to 10−15 moles/mg protein in human corpora lutea. The binding of 125I-hCG to ovary was found to vary at different stages of the menstrual cycle. The binding of 125I-hCG to human ovaries increased on days 13–15 of the cycle, then declined slightly, and increased again on days 22–23. Following day 23, there was a slow decline until day 27 when binding activity could no longer be measured. No binding could be measured by the corpus luteum after the onset of menstruation or in corpora albicans.

scholarly journals The binding of calcium and yttrium ions to a glycoprotein from bovine cortical bone

1967 ◽  
Vol 105 (3) ◽  
pp. 1177-1185 ◽  
Author(s):  
P A Williams ◽  
A. R. Peacocke
Keyword(s):  
Cortical Bone ◽  
Binding Sites ◽  
Association Constant ◽  
Chondroitin Sulphate ◽  
Bone Sialoprotein ◽  
Carboxyl Groups ◽  
Similar Extent ◽  
Strong Electrostatic Interaction ◽  
Titration Curves ◽  
Number Of Binding Sites

The binding of Ca2+ and Y3+ to an acidic glycoprotein from bovine cortical bone, bone sialoprotein, was determined from the titration curves at I 0·2 in the presence and absence of the cations. The binding of Y3+ was greater than that of Ca2+. The value for the association constant, k, for the interaction with Y3+ increased with pH, from log k 2·93 at pH3·4 to log k 3·50 at pH4·4, and the number of binding sites/mol. increased from 4·6 at pH3·4 to 9·1 at pH4·4. It is proposed that the binding site consists of three carboxyl groups, but it is likely that the binding is a strong electrostatic interaction rather than a co-ordination linkage. A chondroitin sulphate–protein complex also extracted from bovine cortical bone interacted with Y3+ and Ca2+ to a similar extent as did bone sialoprotein. It is suggested that these materials are present in bone at the resting and resorbing surfaces and that they contribute to the deposition of yttrium, americium and plutonium at these sites.

CHANGES IN OESTRADIOL-17β BINDING IN THE HYPOTHALAMI AND PITUITARY GLANDS OF PERSISTENTLY INFERTILE EWES PREVIOUSLY EXPOSED TO OESTROGENIC SUBTERRANEAN CLOVER: EVIDENCE OF ALTERATIONS TO OESTRADIOL RECEPTORS

1978 ◽  
Vol 78 (2) ◽  
pp. 171-177 ◽  
Author(s):  
B. Y. TANG ◽  
N. R. ADAMS
Keyword(s):  
Binding Sites ◽  
Association Constant ◽  
Feedback Regulation ◽  
Subterranean Clover ◽  
Pituitary Glands ◽  
Number Of Binding Sites ◽  
And Control ◽  
Apparent Association

SUMMARY The binding of [3H]oestradiol-17β to the hypothalamus and pituitary gland of cloveraffected permanently infertile and control ovariectomized ewes was compared in vivo and in vitro. When [3H]oestradiol-17β was infused into the carotid artery (10 ng/min), the total homogenate and the nuclear and protamine-precipitable cytosol fractions of hypothalami and pituitary glands from clover-affected ewes bound significantly more [3H]oestradiol than those of the controls. Cytoplasmic oestradiol-17β receptors from the pituitary glands of clover-affected ewes showed a significantly lower apparent association constant and a higher number of binding sites/mg protein in vitro. It is suggested that the hypothalami and pituitary glands of ewes made permanently infertile by oestrogenic clover are less sensitive to feedback regulation of oestradiol-17β at physiological levels.

Zinc transport in the haemolymph of Carcinus maenas (Crustacea: Decapoda)

1984 ◽  
Vol 64 (4) ◽  
pp. 801-807 ◽  
Author(s):  
Paolo Zatta
Keyword(s):  
Binding Sites ◽  
Association Constant ◽  
Carcinus Maenas ◽  
Zinc Ions ◽  
Zinc Transport ◽  
Copper Protein ◽  
Number Of Binding Sites

In Carcinus maenas haemolymph, zinc is almost entirely bound to the respiratory pigment, which is the copper-protein haemocyanin (Hc). Zinc ions are loosely bound, as indicated by the low value of the association constant (k = 1.7 × 105 M-1 at pH = 8.0). The number of binding sites N is equal to 4 per minimal functional subunit (75000 Dalton). No co-operativity has been found between the different metal sites. Data reported in this paper support the hypothesis that haemocyanin can act as metal carrier in the haemolymph of C. maenas.

Changes in Cardiac and Hepatic Glucocorticoid Receptors after Adrenalectomy

1976 ◽  
Vol 51 (5) ◽  
pp. 487-493
Author(s):  
M. C. Gregory ◽  
D. Duval ◽  
P. Meyer
Keyword(s):  
Intravenous Injection ◽  
Binding Sites ◽  
Rat Heart ◽  
Glucocorticoid Receptors ◽  
Liver Cytosol ◽  
Receptor Complexes ◽  
Number Of Binding Sites ◽  
Endogenous Steroids

1. The total number of specific dexamethasone-binding sites in rat heart and liver cytosol was measured at intervals after adrenalectomy. 2. Between 12 and 48 h after adrenalectomy there was a significant increase in the number of binding sites in both heart and liver cytosol. Affinity was unchanged. 3. Of the [3H]corticosterone bound to liver cytosol proteins after an intravenous injection 98% disappeared within 2 h in vivo. Dissociation of endogenous corticosterone-receptor complexes in liver cytosol will thus be substantially complete some hours before the number of receptors increases. 4. It was concluded that there is a true increase in the number of glucocorticoid receptors occurring principally between 12 and 48 h after suppression of endogenous steroids.

scholarly journals Investigation of the effects of temperature and ions on the interaction between ECG and BSA by the fluorescence quenching method

2011 ◽  
Vol 63 (2) ◽  
pp. 325-331 ◽  
Author(s):  
Jinyao Zhao ◽  
Xinyu Jiang ◽  
Xin Liu ◽  
Fenglian Ren
Keyword(s):  
Bovine Serum Albumin ◽  
Binding Sites ◽  
Binding Constants ◽  
Epicatechin Gallate ◽  
Number Of Binding Sites ◽  
Fluorescence Quenching Method ◽  
Effects Of Temperature ◽  
Quenching Method ◽  
The Stability ◽  
Increasing Temperature

The effects of temperature and common ions on binding (-)-epicatechin gallate (ECG) to bovine serum albumin (BSA) are investigated. The binding constants (Ka) between ECG and BSA are 1.20 ? 106 (17?C), 1.38 ? 106 (27?C), and 5.69 x 106 L mol-1 (37?C), and the number of binding sites (n) were 1.14, 1.15, and 1.26, respectively. These results showed that the increasing temperature improves the stability of the ECG-BSA system, which results in a higher binding constant and the number of binding sites of the ECG-BSA system. The presence of Co2+ and Zn2+ ions decreased the binding constants (Ka) and the number of binding sites (n) of ECG-BSA complex. However, the presence of Cu2+ and Ni2+ increased the affinity of ECG for BSA largely. The positive ?H and positive ?S indicated that hydrophobic forces might play a major role in the binding between ECG and BSA.

Use of a Lyophilized Reference Plasma to Compare Coagulation Test Procedures

1975 ◽  
Vol 34 (02) ◽  
pp. 426-444 ◽  
Author(s):  
J Kahan ◽  
I Nohén
Keyword(s):  
Oral Anticoagulant Therapy ◽  
Repeated Measurements ◽  
Test Procedures ◽  
Coagulation Activity ◽  
Close Relationship ◽  
Measured Activity ◽  
Test Materials ◽  
The Difference ◽  
The Stability ◽  
The One

SummaryIn 4 collaborative trials, involving a varying number of hospital laboratories in the Stockholm area, the coagulation activity of different test materials was estimated with the one-stage prothrombin tests routinely used in the laboratories, viz. Normotest, Simplastin-A and Thrombotest. The test materials included different batches of a lyophilized reference plasma, deep-frozen specimens of diluted and undiluted normal plasmas, and fresh and deep-frozen specimens from patients on long-term oral anticoagulant therapy.Although a close relationship was found between different methods, Simplastin-A gave consistently lower values than Normotest, the difference being proportional to the estimated activity. The discrepancy was of about the same magnitude on all the test materials, and was probably due to a divergence between the manufacturers’ procedures used to set “normal percentage activity”, as well as to a varying ratio of measured activity to plasma concentration. The extent of discrepancy may vary with the batch-to-batch variation of thromboplastin reagents.The close agreement between results obtained on different test materials suggests that the investigated reference plasma could be used to calibrate the examined thromboplastin reagents, and to compare the degree of hypocoagulability estimated by the examined PIVKA-insensitive thromboplastin reagents.The assigned coagulation activity of different batches of the reference plasma agreed closely with experimentally obtained values. The stability of supplied batches was satisfactory as judged from the reproducibility of repeated measurements. The variability of test procedures was approximately the same on different test materials.

The Estimation of the Number of Binding Sites for Antibody on Antigen Molecules with Reference to Factor VIII and its Antibody

1976 ◽  
Vol 35 (02) ◽  
pp. 274-288 ◽  
Author(s):  
Judith Pool ◽  
Rosemary Biggs ◽  
R. G Miller
Keyword(s):  
Factor Viii ◽  
Binding Sites ◽  
Theoretical Basis ◽  
Human Antibody ◽  
Rabbit Antibody ◽  
Number Of Binding Sites ◽  
Theoretical Considerations

SummaryThe theoretical basis for determining the number of antibody sites on antigen molecules is examined. The theoretical considerations are applied to factor VIII molecules. Examples based on data available at the Oxford Haemophilia Centre are calculated to illustrate the approach. It is concluded that there are few sites on each factor VIII molecule for human antibody. The three antibodies for which reasonable data were available suggest 1–3 sites for human antibody. The data for rabbit antibody suggest 5–6 sites per factor VIII molecule.

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