the effect of physiological concentrations of caffeine (purified from persian tea) on adenosine deaminase (ada) activity at physiological and pathological concentrations of adenosine (as substrate) in 50 mm tris-hcl buffer (ph 7.3) at 37°c was investigated, using uv-vis spectroscopy. ada exhibited a bi-phasic activity behavior and both phases showed positive cooperativities indicating adenosine...

We report herein the occurrence of a positive homotropic allosteric binding effect of two macrocyclic azacalixpyridines. This effect was firstly found to be crucial in the formation and stabilization of ultra-small silver nanoparticles.

The phenylalanine inhibition of skeletal muscle pyruvate kinase has been further studied. Even at high levels of the inhibitor the plots of reaction rates as a function of phosphoenolpyruvate concentration give hyperbolic curves; the inhibition by phenylalanine is of the mixed type. The enzyme exhibits a homotropic cooperative effect with respect to this inhibitor. This property is strongly dep...

The 2nd outer loop (o2) of muscarinic acetylcholine receptors (mAChRs) contains a highly conserved cysteine residue that is believed to participate in a disulfide bond and is flanked on either side by epitopes that are critical to the binding of many muscarinic allosteric modulators. We determined the allosteric binding parameters of the modulators gallamine, W84, and tetrahydroaminoacridine (T...

The positive homotropic binding of tetrahydrofolate to monkey liver serine hydroxymethyltransferase was abolished on preincubating the enzyme with NADH and NADPH. NAD+ was a negative heterotropic effector, whereas NADP+ was without effect. The allosteric effects of nicotinamide nucleotides on the serine hydroxymethyltransferase, reported for the first time, lead to a better understanding of the...

L-Lactate dehydrogenase from Bifidobacterium longum shows homotropic activation by pyruvate as well as heterotropic activation by fructose 1,6-bisphosphate. Hybrid enzymes were produced from the wild-type subunit and a mutant subunit, whose substrate specificity was altered to that of malate dehydrogenase, and separated to analyze the substrate-induced homotropic activation mechanism. Oxamate, ...

A triazole-bearing picket fence type nickel porphyrin (1) has been synthesized as a host compound for anion binding. Among the various anionic species examined, cyanide was the only one that affected a spectral change of 1. Moreover, 1 exhibited strong homotropic positive allosterism against cyanide binding due to an electronic effect as well as multiple hydrogen bonds formed between cyanide an...

In this work we use of an optimized homotropic transformation structural element in order to improve the preprocessing stage for handwriting and hand printed document analysis. The homotropic transformation is use to improve the sequential thinning procedure. In that case we produce less coarse skeleton lines with a reduced number of thinning cycles. If the documents are not good enough, an ada...

The effect of physiological concentrations of caffeine (purified from Persian tea) on adenosine deaminase (ADA) activity at physiological and pathological concentrations of adenosine (as substrate) in 50 mM Tris-HCl buffer (pH 7.3) at 37°C was investigated, using UV-VIS spectroscopy. ADA exhibited a bi-phasic activity behavior and both phases showed positive cooperativities indicating adenosine...

The effect of physiological concentrations of caffeine (purified from Persian tea) on adenosine deaminase (ADA) activity at physiological and pathological concentrations of adenosine (as substrate) in 50 mM Tris-HCl buffer (pH 7.3) at 37°C was investigated, using UV-VIS spectroscopy. ADA exhibited a bi-phasic activity behavior and both phases showed positive cooperativities indicating adenosine...