Possible mechanisms of binding

Possible mechanisms of binding to the settling particles should be examined, taking into account the speciation in solution of Cu and Zn. An intriguing relationship exists between total dissolved copper, free copper ion, and copper bound in particles. The ratio of [Cu2+] to total dissolved Cu is about 10 610 As determined from the concentration in settling particles and in the water column, the distribution coefficients for Cu are Kd = 1-5 X 104 L/kg, with variations over the year. 

Enzymatic activities. The hydrolysis of ATP by actin-activated myosin is the characteristic enzymatic activity of muscle, smooth muscle included. All forms of smooth muscle myosin are slower than those of other muscles. The binding site for ATP and a reduced enzymatic activity are still present in monomeric myosin. The enzymatic activity of monomeric myosin is altered by a conformational change, (the 10S-6S transition) and the species of cations present in the reaction mixture. These differences relate to the possible mechanisms of regulation. 

Acute exposure to large amounts of endosulfan results in frank effects manifested as hyperactivity, muscle tremors, ataxia, and convulsions. Possible mechanisms of toxicity include (a) alteration of neurotransmitter levels in brain areas by affecting synthesis, degradation, and/or rates of release and reuptake, and/or (b) interference with the binding of those neurotransmitter to their receptors. 

Fig. 9.1 Schematic representation of possible mechanisms of resistance in Gram-negative and Gram-positive bacteria. 1, antibiotic-inactivating enzymes 2, antibiotic efflux proteins 3, alteration or duplication of intracellular targets 4, alteration of the cell membrane reducing antibiotic uptake 5, alterations in porins or lipopolysaccharide reducing antibiotic uptake or binding.

Another possible mechanism of potentiator action, the barrier disruption hypothesis, has received considerable attention. This theory of potentiator action, first proposed by Parrot and Nicot (24), suggests that the potentiators may interfere with the protective actions of intestinal mucin. Mucin is known to bind histamine in vitro (53), and Parrot and Nicot ( ) suggested that this binding was essential to prevent passage of histamine across the intestinal wall. Potentiators such as putrescine and cadaverine... 

Johnson, C. A. Kersten, M. 1999. A possible mechanism of Zn binding to Ca silicate hydrates. Environmental Science and Technology, 33, 2296-2298. 

For [cis-Pt(NH3)2(N-het)Cl]+ compounds an ammonia-loss pathway, as a result of the trans labilizing effect of a N-het, to achieve didentate binding to DNA has been considered as a possible mechanism of action... 

The reaction of sulfur-containing biomolecules with platinum antitumor compounds, thereby preventing binding to the critical DNA target, is a possible mechanism of inactivation and is supported by numerous studies. Thus, glutathione (GSH, a cysteine-containing tripeptide see also Fig. 6), which is the predominant intracellular thiol and is present in concentrations varying from 0.5 to 10 mM, is able to inhibit the reaction of DNA with [Pt(en)Cl2] (74) and with cis-Pt (75, 76). It has also been observed that the presence of cysteine can inhibit the reaction between cis-Pt and d-Guo (77). Furthermore, the antitumor activity of cis-Pt was proved to be inhibited by coadministered methionine (78, 79) and even a bis-adduct between cis-Pt and methionine has been isolated from the urine of patients (80). 

Possible mechanisms of hormone action, (a) The hormone (H) theoretically activates an enzyme (E) directly as an allosteric effector. (b) Alternatively, a separate binding protein for the hormone, called a receptor (R), may then activate an enzyme, (c) Another possibility interposes an acceptor protein (A) between the receptor and the enzyme. Each interaction is reversible. 

Flavonoids are now regarded as a class of MDR modulators that directly interact with nucleotide and steroid binding domains of P-gp. However, the molecular mechanism leading to inhibition of MRP1 transport activity by these compounds is still far from being fully understood. Apart from interaction with NBD or substrate binding sites, the stimulation of GSH transport carried by MRP1 and depletion of cellular GSH was also proposed as a possible mechanism of MRPl-mediated resistance reversal by flavonoids [223]. 

Two possible mechanisms of exchange reactions are supposed 1) joining of P3 to the loops of the Pt chain in the P, - P2 complex 2) binding of P3 by Pj-free molecules in the system because of the equilibrium Pt - P2 5 P) + P2. An exchange reaction between P2 and P3 in the complex may occur both due to the high heat of Pj — P3 complex formation and to the increase of entropy of the system by exclusion of more flexible chains into the solution. 

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