Search results for "Ternary complex"
showing 6 items of 16 documents
Spectrophotometric determination of vitamin C using the copper(II)-nioxime-ascorbic acid system following stabilization in a propylene glycol medium
1989
Abstract A spectrophotometric method for the determination of Vitamin C is proposed. The procedure is based on formation and stabilization of the ternary complex Cu(II)-nioxime-ascorbic acid in 80% ( v v ) propylene glycol-water medium. The method has a high degree of tolerance for the determination of ascorbic acid in the presence of other active substances or excipients likely to be present along with vitamin C in pharmaceutical formulations. The suggested method has proved to be rapid and precise and has been successfully applied to different commercial pharmaceutical preparations of vitamin C. Precision, measured on the relative standard deviation, did not exceed 0.73%.
Soluble gp130 is the natural inhibitor of soluble interleukin-6 receptor transsignaling responses
2001
Signal transduction in response to interleukin-6 (IL-6) requires binding of the cytokine to its receptor (IL-6R) and subsequent homodimerization of the signal transducer gp130. The complex of IL-6 and soluble IL-6R (sIL-6R) triggers dimerization of gp130 and induces responses on cells that do not express membrane bound IL-6R. Naturally occurring soluble gp130 (sgp130) can be found in a ternary complex with IL-6 and sIL-6R. We created recombinant sgp130 proteins that showed binding to IL-6 in complex with sIL-6R and inhibited IL-6/sIL-6R induced proliferation of BAF/3 cells expressing gp130. Surprisingly, sgp130 proteins did not affect IL-6 stimulated proliferation of BAF/3 cells expressing …
Achieving Strong Positive Cooperativity through Activating Weak Non-Covalent Interactions
2018
Positive cooperativity achieved through activating weak non-covalent interactions is common in biological assemblies but is rarely observed in synthetic complexes. Two new molecular tubes have been synthesized and the syn isomer binds DABCO-based organic cations with high orientational selectivity. Surprisingly, the ternary complex with two hosts and one guest shows a high cooperativity factor (α=580), which is the highest reported for synthetic systems without involving ion-pairing interactions. The X-ray single-crystal structure revealed that the strong positive cooperativity likely originates from eight C-H⋅⋅⋅O hydrogen bonds between the two head-to-head-arranged syn tube molecules. Thes…
Chiral recognition of protected amino acids by means of fluorescent binary complex pyrene/heptakis-(6-amino)-(6-deoxy)-β-cyclodextrin
2006
The ability of the binary complex pyrene (Py)/heptakis-(6-amino)-(6-deoxy)-β-cyclodextrin (am-β-CD) to act as a chiral selector was tested at two pH values (8.0 and 9.0). Phenylalanine (Phe), methionine (Met) and histidine (His) were used as chiral model molecules. The stability of ternary complexes Py/am-β-CD/amino acid was determined by means of spectrofluorimetric measurements. The data collected showed an increase in stability going from the binary to ternary complex and above all the possibility to use the binary complex as a chiral selector. Finally, data collected at two pH values showed that the binary complex is a better chiral selector when charged rather than in its neutral form.
Proton-dependent kinetics of citrate uptake in growing cells ofLactococcus lactissubsp.lactisbv.diacetylactis
1995
The kinetic analysis of citrate uptake in growing cells of Lactococcus lactis subsp. lactis biovar. diacetylactis identified a proton-dependent transport and suggested the divalent anionic species as the form of citrate transported across cell membranes. The reaction followed Michaelis-Menten kinetics for a two-substrate reaction. The limiting steps were the formation of the ternary complex and the rate of transport. Temperature modified the activity of the permease, increasing the uptake rate.
Reversible inhibition of CO2fixation by ribulose 1,5-bisphosphate carboxylase/oxygenase through the synergic effect of arsenite and a monothiol
2013
The activity of the photosynthetic carbon-fixing enzyme, ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), is partially inhibited by arsenite in the millimolar concentration range. However, micromolar arsenite can fully inhibit Rubisco in the presence of a potentiating monothiol such as cysteine, cysteamine, 2-mercaptoethanol or N-acetylcysteine, but not glutathione. Arsenite reacts specifically with the vicinal Cys172-Cys192 from the large subunit of Rubisco and with the monothiol to establish a ternary complex, which is suggested to be a trithioarsenical. The stability of the complex is strongly dependent on the nature of the monothiol. Enzyme activity is fully recovered through …