Monovalent Interactions Research Articles

Inhibition or activation of human T cell receptor transfectants is controlled by defined, soluble antigen arrays.

We present evidence that direct T cell receptor (TCR) occupancy by antigen can either activate or inhibit T cells, depending upon whether or not a threshold number of local TCRs are crosslinked by multivalent arrays of the antigen. Variants of Jurkat cells were previously transfected with TCR alpha and beta chains that bind fluorescein, yielding FL-TCR+ human T cells. The transfectants are activated upon binding soluble multivalent antigen arrays at concentrations well below those required for monovalent interactions. This activation, measured by calcium fluxes and interleukin 2 (IL-2) production, indicates the superior binding avidity of multivalent ligands. Smaller, less multivalent arrays do not activate the cells, but antagonize larger arrays, demonstrating that antigen can bind TCR as either agonist or antagonist. The balance between activation and inhibition depends upon antigen array size, ligand valence, and concentration, indicating that a threshold extent of receptor crosslinking, and not individual perturbations of single TCR, is required for activation by antigen. Approximately 100 stimulatory arrays specifically bind per FL-TCR+ cell at concentrations where IL-2 production is half-maximal.

Determination of the association constant of monovalent mode protein—sugar interaction by capillary zone electrophoresis

Protein—sugar interaction was observed by capillary zone electrophoresis, using a few β-galactose-specific lectins and lactobionic acid as protein and sugar models, respectively. The lectin peaks were retarded in a concentration-dependent manner by addition of lactobionic acid in a carrier, and association constants of monovalent mode interactions could be obtained from t 1 (migration time of protein), t 2 (migration time of complex, obtainable as the migration time at the plateau) and the slope of the ( t - t 1) −1 vs. [S] −1 plots, where t and [S] are the migration of protein in the presence of lactobionic acid and the concentration of lactobionic acid, respectively. The values for Ricinus communis agglutinin, peanut agglutinin and soy bean agglutinin at pH 6.8 were 3.3 · 10 3, 9.1 · 10 2 and 1.1 · 10 2 1 mol −1, respectively. This method required only small amounts of protein samples and was reproducible. The amount of the sugar could be minimized under the conditions that the carrier was a buffer containing the sugar whereas the electrode solutions consisted only of the buffer

Monovalent ion-phosphatidylcholine interactions: an electron paramagnetic resonance study

The apparent Mn 2+ binding constant for l-α-dipalmitoylphosphatidylcholine (DPPC) bilayers dispersed in monovalent salt and MnCl 2 dispersions was determined as a function temperature using electron paramagnetic resonance (ERP). Reproducibility in the data sets requires the use of a standard salt solution and dual cavity techniques. Changes in the binding constant at different phase states and temperatures were observed and correlated to the influence of monovalent salts on the thermal properties of DPPC. The turning points (i.e. changes in slope) in the curves of the apparent Mn 2+ binding constant versus temperature can be understood in terms of differences in ion binding to headgroups with different bilayer surface areas. The influence of Li + and SCN − on Mn 2+ binding is viewed as a function of their presence in the ionic media in contact with the bilayer rather than as a competitive event. Other monovalent ions studied appear to have little effect on the measured apparent Mn 2+ binding constants for DPPC headgroups.

The nature of simple monovalent cation-silica interaction as reflected in the spin-lattice relaxation time of sodium-23

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe nature of simple monovalent cation-silica interaction as reflected in the spin-lattice relaxation time of sodium-23Hyun M. Jang and Douglas W. FuerstenauCite this: Langmuir 1987, 3, 6, 1114–1118Publication Date (Print):November 1, 1987Publication History Published online1 May 2002Published inissue 1 November 1987https://doi.org/10.1021/la00078a041RIGHTS & PERMISSIONSArticle Views128Altmetric-Citations13LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (579 KB) Get e-Alerts Get e-Alerts

High-performance affinity chromatography of divalent concanavalin A on matrices of variable ligand density

Divalent concanavalin A was chromatographed under isocratic conditions on matrices of variable ligand density, containing immobilized p-aminophenyl α- d-mannopyranoside or d-glucosamine. Methyl α- d-mannopyranoside was used as a competing inhibitor in the mobile phase. As the ligand density increased, retention was observed to change from a primarily monovalent interaction to a primarily divalent interaction. Several retention models were used to examine the data and to evaluate the extent of cooperative binding. Especially when possible heterogeneity in the distribution of ligand molecules was taken into account, it was found that several retention models fit the data reasonably well.

Membrane distribution and adsorptive endocytosis by C3b receptors on human polymorphonuclear leukocytes.

C3b receptors on human polymorphonuclear leukocytes (PMN) were nonrandomly distributed in small clusters on the plasma membranes of these cells when assessed by indirect immunofluorescence at 0 degree C using monospecific rabbit Fab' or F(ab')2 anti-C3b receptor and tetramethylrhodamine isothiocyanate (TRITC)-conjugated goat IgG anti-F(ab')2. When PMN were incubated with the bivalent anti-C3b receptor at 37 rather than at 0 degree C, almost no immunofluorescence was observed, which indicates that the C3b receptor-F(ab')2 complexes had been rendered inaccessible to TRITC-IgG anti-F(ab')2. Endocytosis of the anti-C3b receptor ligand was quantitated by measuring the binding 131I-IgG anti-F(ab')2 by PMN that had previously taken up 125I-F(ab')2 anti-C3b receptor at 0 and at 37 degree C, respectively. There was a constant 2: 1 molar ratio of anti-F(ab')2 to anti-C3b receptor with PMN that had been incubated with the first antibody at 0 degree C. In contrast, when increments of F(ab')2 anti-C3b receptor were taken up by the cells at 37 degree C, there was a dose-related decline in this molar ratio to a minimum of 0.2 molecules of anti-F(ab')2 anti-F(ab')2 bound per molecule of PMN-associated anti-C3b receptor. 125I-F(ab')2 anti-C3b receptor taken up by PMN at 37 degree C was also inaccessible to release by proteolytic treatment of the cells with pronase. The rate of endocytosis of 125I-F(ab')2 anti-C3b receptor was rapid as the PMN-bound antibody fragment became inaccessible to 131I-IgG anti-F(ab')2 within 10 min during incubation of the cells at 37 degree C. In contrast to these findings, 125I-Fab' anti-C3b receptor that was taken up by PMN at 37 degree C remained accessible to both 131I-IgG anti-F(ab')2 and to proteolytic release by pronase, which suggests that monovalent interaction of ligand with C3b receptors was not sufficient for induction of endocytosis. The requirement for multivalency was also demonstrated using the C3b-OR, the normal ligand for the C3b receptor. 125I-C3b-OR was specifically bound by PMN but remained on the cell receptor. 125I-C3b-OR was specifically bound by PMN but remained on the cell surface, as determined by its accessibility to pronase, unless it was cross-linked with F(ab')2 anti-C3. Although C3b receptors on PMN do not mediate internalization of adsorptive pinocytosis of soluble ligand indicates their potential for the clearance of C3b-bearing immune complexes without recruitment of other cell surface receptors.

Low field electric birefringence study of monovalent cation-DNA interactions

The effects of monovalent cations on DNA have been studied using static and dynamic electric birefringence. Kerr's law is obeyed in a limited E range (<30 V cm −1) and the steady state birefringence values are close for the different cations. The birefringence kinetics have been analysed in terms of three relaxation times. On a semilogarithmice plot of Δn(t), the tail of the curve is linear over a wide range of time for Na +, K +, NH 4 + and Li +. Only for Cs + solution is no linear part found and a much longer relaxation time is determined. This only contributes a small part of the total birefringence. With Cs + this contribution is more field-dependent than for the other cations and we observe a larger molecular flexibility. On the other hand, with Li + a greater stiffness of the DNA molecule appears. The electrical polarizabilities anisotropies decrease in the order: Cs + > NH + 4 > K + > Na + > Li +. There are no significant differences in the optical anisotropy factors.

Effets du glycérol sur les interactions des cations monovalents avec la (Na +-K +)-ATPase des membranes d'érythrocytes humains solubilisées

Effets du glycérol sur les interactions des cations monovalents avec la (Na +-K +)-ATPase des membranes d'érythrocytes humains solubilisées

Cation sites of the ( [formula omitted])-dependent ATPase: Mechanisms for Na +-induced changes in K + affinity of the phosphatase activity

Monovalent cation interactions with the K +-dependent phosphatase activity of a rat brain ( Na + + K + )-dependent ATPase (ATP phosphohydrolase, EC 3.6.1.3) preparation were reexamined in attempts to distinguish between two models designed to account for stimulation of phosphatase activity by Na + when K + concentrations are low, but inhibition when K + concentrations are high. One model (Robinson, J. D. (1970) Arch. Biochem. Biophys. 139, 17–27) proposes that in the presence of Na + an alternative enzyme pathway, characterized by a higher affinity for K +, becomes available through the phosphorylation of the enzyme by substrate. The second model (Albers, R. W. and Koval, G. J. (1973) J. Biol. Chem. 248, 777–784) attributes the response to distinct classes of sites for K +, without involving the participation of substrate. Data obtained using umbelliferone phosphate can be fitted quantitatively to the original model. In addition, experiments evaluating K + affinity through a Be 2+ inactivation technique demonstrated that both Na + and substrate were necessary for the increase in K + affinity. Similar experiments with nitrophenyl phosphate and a non-phosphorylating analog that can attain the active site, nitrobenzyl phosphonate, imply that phosphorylation was the necessary factor. These data support the original proposal, but do not rule out the possibility that, in addition, there may be multiple classes of sites for K +.