Equimolar complexes

Complex Formation. AH four Cg aromatic isomers have a strong tendency to form several different types of complexes. Complexes with electrophilic agents ate utilized in xylene separation. The formation of the HE-BF —MX complex is the basis of the Mitsubishi Gas—Chemical Company (MGCC) commercial process for MX recovery, discussed herein. Equimolar complexes of MX and HBr (mp — 77°C) and EB and HBr (mp — 103°C) have been reported (32,33). Similatly, HCl complexes undergo rapid formation and decomposition at —80°C (34). 

One of the most efficient plasmin inhibitor is a2-PI (70 kDa), which is synthesized by the liver, secreted into the blood circulation, where its concentration is 1 pM. It rapidly forms equimolar complex with plasmin, and in this complex, the active site of the enzyme is irreversibly blocked. The complex, thereafter, is removed by the liver. It is remarkable that when plasmin is bound to its substrate (fibrin), it is protected against its primarily inhibitor, a2-PI the rate of inactivation decreases by 400-fold (Fig. 4) [3]. 

The a2-plasmin inhibitor, a single-chain glycoprotein (70 kDa), forms rapidly an equimolar complex with plasmin, where the enzyme loses its activity. It is synthesized by the liver and secreted into the blood circulation, where its concentration is 1 pM. 

Three main structural sub-groups can be recognised alkylaluminium dihalides, dialkylaluminium halides, and trialkyldialuminium trihalides (equimolar complexes of a trialkylaluminium and an aluminium trihalide). While this is generally a very reactive group of compounds, similar in reactivity to trialkylaluminium compounds, increase in size of the alkyl groups present and in the degree of halogen substitution tends to reduce pyrophoricity. 

Interactions of heparinoids with the most diverse proteins such as enzymes and enzyme inhibitors, cytokines, and adhesion molecules have been described. To date, many more than a hundred heparin binding proteins are known. A number of heparin binding proteins are members of the serpin family of serine protease inhibitors. The best described example is antithrombin [4]. Antithrombin III (AT III) is able to inhibit various serine proteases involved in the blood coagulation process by formation of stable, equimolar complexes. Binding of heparin to AT III accelerates the kinetics of this complex formation by several orders of magnitude. This has been the basis for the successful clinical use of heparin as an anticoagulant for nearly sixty years. 

A systematic study of the Sharpless epoxidation led to the following conclusions (1) an equimolar complex of titanium tetraalkoxide and tartrate diester [(tartrate)(RO)2Ti] is the... 

Fig. 3. Temperature dependence of the symmetric CFI2 stretching mode frequency of DMPG Na+ (diamonds) and of the equimolar complexes DMPG Mg2+ (circles), DMPG Ca2+ (squares) and DMPG Sr2+ (triangles) in 100mM NaCl at pH 7. Solid symbols represent the heating and open symbols the cooling scan. The samples were stored for 24 h at 4 °C prior to the first cycle. Reprinted with permission from Ref. [56]. Copyright (2000), Elsevier.

Poly(U) = poly(uridylic add), poly(l + C) = equimolar complex of poly(inosinic add) and poly(cytidylic add), poly (A + U) = equimolar complex of poly(adenylic add) and polyfnridylic add), RNA = polyribonucleic add, DNA = polydeoxyribonucleic add, dDNA = denatured DNA... 

The formation of a water-soluble complex of poly(sodium acrylate) with 5,6 ionen bromide of 3 1 composition has been observed108. Its mass and size are independent of the complex origin and are equal to 660 x 103 and 33 nm respectively. The soluble complex presumably consists of the insoluble nucleus of the equimolar polyelectrolyte complex and adsorbed excess of poly(sodium acrylate) on its surface. The soluble polyelectrolyte complex dissociates at higher ionic strengths (0.05-0.1) whereas the insoluble equimolar complex in the core is still stable and precipitates from the solution. 

It is important to consider the influence of interaction between functional groups of drugs that leads to their habit modification when formulated in suspension dosage form. Proton transfer from the N atom of sulfamethoxazole to the pyrimidine basic N1 atom of trimethoprim has been reported to occur in their equimolar complexes. Bettinetti et al. have reported nucleation of the complex of trimethoprim and sulfa-methoxypyridazine (1 1) to be accelerated by water or wet granulation. Our studies on cotrimoxazole (unpublished results) revealed immediate formation of fine needle-shaped crystals irrespective of the initial shape of sulfamethoxazole and trimethoprim crystals as a result of the interaction between the two drugs in suspension form. Small needles (Fig. 6A) were... 

Bleomycin is obtained as an equimolar complex with cupric ion. The copper can be removed by treatment with hydrogen sulfide in methanol solution to give a colorless metal-free BLM, which can be reconverted to the natural copper complex by addition of cupric ion to the aqueous solution, although there are many potential coordination sites in the molecule. Both metal-free and copper-chelated BLMs inhibited growth of microorganisms and mammalian cells, but DNA strand cleavage in vitro was caused only by metal-free BLM, not by the copper-complex. 

The compounds form 1 1 complexes with all alkali ions and with a large number of other metal ions in organic solvents267,268,307. Among the alkali ions, K+ is bound most strongly, but K+-complex stability as well as K+ > Na+ selectivity are much less pronounced than with valinomycin. In concentrated enniatin solutions, non-equimolar complexes are formed. NMR- und CD-spectroscopic titrations have demonstrated that 2 1 enniatin-cation complexes are formed with a stability order of K+ > Cs+ > Na+. Evidence for formation of a 3 2 complex with Cs+ was also obtained133,216 ... 

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