Ligand aggregation

Remmele RL Jr, Bhat SD, Phan DH, Gombotz WR. Minimization of recombinant human Flt3 ligand aggregation at the Tm plateau a matter of thermal reversibility. Biochemistry 1999 38(16) 5241-5247. 

Substantial structural and mechanistic work has been carried out on the acetylide-ligand aggregation complex. " The reactive species responsible for this remarkable degree of selectivity is sensitive to the conditions of formation, and both yield and selectivity depend on strict adherence to the reaction protocol. 

Figure 12,4 Data workflow with statistical analysis. The data processing and analysis follows the following sequence (a) Acquisition of files for the protein in the apo state and bound with the ligands of interest over several time points, (b) Isotope measurement and %D determination, (c) Aggregate sample percent deuteratlon Is arrived at by the mean of the individual on-exchange time point mean values. The standard deviation for the sample Is the RMS error of each time point divided by the number of time points, (d) Perturbation %D = ligand aggregate %D-apo aggregate %D. Standard error is calculated by taking the root sum squared of aggregate sample standard deviations, (e) Results are subjected to t-test and Tukey comparison, (f) Visualization components represent the results. Reproduced from Ref. [1], with permission from Elsevier...

Fig. 3. Synthesis of mixed lithium-ligand aggregate, for the controlled ROP of L-LA.

As stated at the outset, the organometallic ligand can transport alkali metal cations across phospholipid membranes. Since the molecular surface of the 1 1 complex is polar at one end and apolar at the other, it will be reasonable to assume that transfer of the cations through lipophilic media is more likely to occur in the form of polymeric cation-ligand aggregates than in the form of monomeric entities. The observed structures of the dinuclear Li and the trinuclear Na" " complexes may represent in fact two possible modes of such an aggregation during the process of transport. 

The TEM images also describe the same experimental results (Figure 10.7). Gold nanoparticles prepared in the absence of stabilizing ligands aggregate into large ones with a diameter of 7.7 1.9 nm, while the... 

It is often difficult to represent inorganic compounds with the usual structure models because these structures are based on complex crystals space groups), aggregates, or metal lattices. Therefore, these compounds are represented by individual polyhedral coordination of the ligands such as the octahedron or tetrahedron Figure 2-124d). 

Oxidation—Reduction. Redox or oxidation—reduction reactions are often governed by the hard—soft base rule. For example, a metal in a low oxidation state (relatively soft) can be oxidized more easily if surrounded by hard ligands or a hard solvent. Metals tend toward hard-acid behavior on oxidation. Redox rates are often limited by substitution rates of the reactant so that direct electron transfer can occur (16). If substitution is very slow, an outer sphere or tunneling reaction may occur. One-electron transfers are normally favored over multielectron processes, especially when three or more species must aggregate prior to reaction. However, oxidative addition... 

Water-soluble polymers and polyelectrolytes (e.g., polyethylene glycol, polyethylene imine polyacrylic acid) have been used success-hilly in protein precipitations, and there has been some success in affinity precipitations wherein appropriate ligands attached to polymers can couple with the target proteins to enhance their aggregation. Protein precipitation can also be achieved using pH adjustment, since proteins generally exhibit their lowest solubility at their isoelectric point. Temperature variations at constant salt concentration allow for frac tional precipitation of proteins. 

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