Ligands attachment points

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. 

The numerous surface hydroxyl groups provide attachment points for other functional groups and ligands. 

Binding of these ligands does not occur in a concave groove located on the surface of the receptor protein as otherwise often imagined. As described in Section 2.2.1, the x-ray structure of rhodopsin showed that retinal is bound deep in the seven-helical structure with major interaction points in TM-III and TM-VI, as well as the covalent attachment point in TM-VII. In fact, rhodopsin interacts with basically all transmembrane segments. Importantly, side-chains from the transmembrane helices cover the retinal molecule on all sides, and its binding site is found deep in the middle of... 

The loss of degeneracy of atomic or molecular levels in a molecular entity with a given symmetry by the attachment or removal of ligands to produce reduced symmetries. Ligand field theory treats metal ligand complexation as a consequence of molecular orbital formation, whereas crystal field splitting considers ligands as point... 

K(H0H)6 , the oxygens on the water molecules being the points of attachment. The ion is said to have a coordination number of 6, this value referring to the number of points of attachment that K" " provides to molecules or ions (ligands) which can attach. This water complex with attachments to oxygen is so very stable that displacement of the water molecules by other ligands (attaching molecules or ions) is difficult. As a result, K+... 

The attachment point of the antenna is indicated by — in case of ternary complexes, the sketched molecule acts both as the ternary ligand and antenna. Intrinsic quantum yields estimated from a radiative lifetime ro(Yb) = 2 ms. 

Lohray and coworkers reported the first application of silica gel-supported Cinchona alkaloids in AD in 1996 [67], A 3,6-DHQ2-pyridazine derivative was linked to a silica gel support with an attachment point at one of the quinudidine moieties (Fig. 4, catalyst 13). The alkaloidic ligand was expected to bind to the silica surface resulting in better availability of the active site compared to polymer-... 

Ketz et al. synthesised a keto functionalised imidazolium salt using the standard protocol by reacting the appropriate N-aryl substituted imidazole with the respective keto halide [95], Their intention was to use the corresponding nickel(II) carbene enolate complex in olefin polymerisation reactions similar to the phosphino enolates in the SHOP process [1 ]. It proved difficult to prepare the intended precatalyst with only one carbene enolate ligand attached to the nickel centre. Initially, the homoleptic complex with two carbene enolate ligands was formed. The authors pointed out that the high proportion of n-olefins is unusual. 

Figure 5.8. Example of privileged four-point pharmaeophores, either ereated from a ligand using a particular feature (e.g., the centroid of a "privileged" substructure) or complementary to a protein site using a site point or attachment point of a docked scaffold. Only pharmacophores that include this special feature are included in the fingerprint, thus providing a relative measure of diversity 1 similarity with respect to the privileged feature.

Multidentate Ugand - these have several points of attachment, e.g. ethylenediaminetetra-acetic acid (EDTA), which is a hexadentate ligand (six points of attachment) (Fig. 23.2). 

Because each member of a pair of enantiomeric molecules differs from the other only in the spatial arrangement of the ligands attached to the chiral center, their physical properties, that is, melting point, boiling point, refractive index, solubility, etc., are identical. The major difference between the isomers of an enantiomeric pair was first observed by Biot in 1815 when he noted that one form of tartaric acid rotated plane-polarized light, whereas another form did not (1). 

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