Breakage reversible

Dynamic light-scattering experiments or the analysis of some physicochemical properties have shown that finite amounts of formamide, A-methylformamide, AA-dimethyl-formamide, ethylene glycol, glycerol, acetonitrile, methanol, and 1,2 propanediol can be entrapped within the micellar core of AOT-reversed micelles [33-36], The encapsulation of formamide and A-methylformamide nanoclusters in AOT-reversed micelles involves a significant breakage of the H-bond network characterizing their structure in the pure state. Moreover, from solvation dynamics measurements it was deduced that the intramicellar formamide is nearly completely immobilized [34,35],... 

In 1985, it was reported by Hsiang et al. [43] that the cytotoxic activity of 20-(S)-camptothecin (CPT III) was attributed to a novel mechanism of action involving the nuclear enzyme topo I, and this discovery of unique mechanism of action revived the interest in CPT and its analogues as anticancer agents. CPT stabilizes the covalent, reversible topo I-DNA complex leading to the inhibition of DNA synthesis in mammalian cells and interferes with the topo I breakage-reunion reaction [44]. Clinical trials and structure-activity relationships have demonstrated the requirement of the a-hydroxy group, the... 

Based on the principle of microscopic reversibility one may conclude that the intermediate(s) in the off step will be the same as those generated during the k(m pathway, thus iron nitrosyl bond breakage (k 2)... 

VioOfg- t,/2 = 7-15 h (25 °C), pH-dependent Near equivalency of all oxygens mandates reversible, extensive breakage as exchange mechanism 48-50(a)... 

Industrial examples of adsorbent separations shown above are examples of bulk separation into two products. The basic principles behind trace impurity removal or purification by liquid phase adsorption are similar to the principles of bulk liquid phase adsorption in that both systems involve the interaction between the adsorbate (removed species) and the adsorbent. However, the interaction for bulk liquid separation involves more physical adsorption, while the trace impurity removal often involves chemical adsorption. The formation and breakages of the bonds between the adsorbate and adsorbent in bulk liquid adsorption is weak and reversible. This is indicated by the heat of adsorption which is <2-3 times the latent heat of evaporahon. This allows desorption or recovery of the adsorbate from the adsorbent after the adsorption step. The adsorbent selectivity between the two adsorbates to be separated can be as low as 1.2 for bulk Uquid adsorptive separation. In contrast, with trace impurity removal, the formation and breakages of the bonds between the adsorbate and the adsorbent is strong and occasionally irreversible because the heat of adsorption is >2-3 times the latent heat of evaporation. The adsorbent selectivity between the impurities to be removed and the bulk components in the feed is usually several times higher than the adsorbent selectivity for bulk Uquid adsorptive separation. 

These substances are analogues of thymine (azidothymidine, stavudine), adenine (didanosine), cytosine (lami-vudine, zaldtabine), and guanine (car-bovir, a metabolite of abacavir). They have in common an abnormal sugar moiety. Like the natural nucleosides, they undergo triphosphorylation, giving rise to nucleotides that both inhibit reverse transcriptase and cause strand breakage following incorporation into viral DNA. 

On the other hand, available evidence supports the occurrence of the breakage of protein crosslinks, which allows the antibody access to the antigen. Conventional heat, dry or steam, breaks down reversible protein-protein, protein-nucleic acid, and protein-carbohydrate crosslinks introduced by formaldehyde and thereby unmasks the epitopes, as well as allowing the antibodies access to the epitopes. It is well known that most, if not all, crosslinks formed during formaldehyde fixation are destroyed upon heating even at 37°C... 

---