Ligand binding weak interactions

The species shown in Schemes 8.1 and 8.2 do not contain vacant coordination sites suitable for binding weakly donating ligands such as alkenes. Even in Breslow s zwitterionic intermediate (Scheme 8.1) the nature of the metal-ethene interaction is unclear alkenes do not bind to the LUMO of 16-electron complexes CP2MCI2 (M = Ti, Zr, Hf) or their alkyl derivatives. The isolation by Eisch in 1985 of a cationic titanium vinyl complex [Cp2TiC(Ph)=C(Me)SiMe3], apparently formed by insertion of an alkyne into a putative [Cp2TiMe] intermediate [29], raised the... 

Using a nonequilibrium approach, strong binding can be studied (ligand-receptor complex) (43). However, of particular interest in ACE and MACE is the characterization of weak interactions, since the rate of complex formation and the exchange of solute between aqueous and micellar phase could be too fast to be studied with conventional structure determination methods (MS, NMR). The alternative to those methods, namely, to measure in an equilibrium state, makes MACE highly attractive. Thus, weak bond strengths (acid-base and complex/partition equilibria) are measurable. 

The interaction between actin and myosin, like that between all proteins and ligands, involves weak bonds. When ATP is not bound to myosin, a face on the myosin head group binds tightly to actin (Fig. 5-33). When ATP binds to myosin and is hydrolyzed to ADP and phosphate, a coordinated and cyclic series of conformational changes occurs in which myosin releases the F-actin subunit and binds another subunit farther along the thin filament. 

These ligands are frequently used as metal ion traps to bind undesired metal ions, e. g. in formulations of X-ray contrast agents. Chelated cations may associate electrostatically with anionic compounds and with solvent molecules by weak interactions. This results in the formation of an outer coordination sphere. Instead of the term complex the term chelate is very frequently used meaning that the metal ion is covered by the ligand like a claw ( chela word from the Greek for claw). 

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