Bicine complexes

The stability constants of the two examples for binary M(Bicinate) and ternary M(ATP)(Bicinate) complexes (no value for Cd " is known) provide an order and speak for themselves. These values are so large (Table 13) that Bicine, if used as buffer in the presence of metal ions, will certainly complex a very significant amount of metal ions present. It is further clear that the hydroxyl groups of Bicinate participate at least to some extent in metal ion binding. To put the observed negative values for A log m/atp/l overall into perspective, it may be helpful to recall that the expected statistical value for a regular octahedral coordination sphere of (e.g., Co " ) and the coordination of two different but simple and symmetrical tridentate ligands amounts already to A log A 3.3/s,at/oh = -103 [213]. 

Equilibrium studies in water were performed for [Mc2Sn(IV)] complexes of zwitterion buffers, such as bicine and tricine (L). The results showed the formation of MLH, ML, ML2, MLH i, and MLH 2 with the hydrolysis products of the... 

Bicinchoninic Acid (BCA) Assay. The bicin-choninic acid assay for proteins is based on the same reactions as the Folin-Ciocalteau assay. Proteins are again reacted with alkaline cupric ions to form the biuret complex, and these ions are reduced to cuprous ions by the aromatic amino acids in the proteins. In this case, however, the Cu1+ ions form a complex with bicinchoninic acid (Fig. II-6), which has an intense absorbance maximum at 562 nm. This assay shows the same variation from protein to protein as the Folin-Ciocalteau assay, but is more convenient experimentally and can be made somewhat more sensitive. 

Absorption, fate, and excretion Daunorubicin, doxom-bicin, epirubicin, and idarubicin usually are administered intravenously and cleared by a complex pattern of hepatic metabolism and biliary excretion. The plasma disappearance curve for doxorubicin is multiphasic, with elimination half-lives of 3 hours and about 30 hours. All anthracyclines are converted to an active alcohol intermediate that plays a variable role in their therapeutic activity. Idarubicin has a half-life of about 15 hours, and its active metabolite, ida-rubicinol, has a half-life of about 40 hours. There is rapid uptake of the drugs in the heart, kidneys, lungs, liver, and spleen. They do not cross the blood-brain barrier. 

Because Bicine is derived from glycine, it was expected already nearly 50 years ago that this buffer forms complexes with metal ions [216]. For Tris and Bistris the awareness of metal ion interactions is much lower, and the fact that also mixed ligand complexes may form [212,213], has hardly been reaUzed. Therefore, the stabilities of the ternary Cd " and some other metal ion complexes formed between these buffers and ATP are briefly summarized. The stability constants according to equilibria (28) and (29) are listed in Table 13 together with the stability differences defined in equation (30). 

Table 13 Stability constants of some ternary M(ATP)(L) (eq. 28) and binary M(L) complexes (eq. 29), where L = Tris [212], Bistris [213], or Bicinate [214], as determined by potentiometric pH titrations [212,213] or spectrophotometric measurements [214] in aqueous solutions at 25°C, together with the stability differences according to eq. (30)" ...

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