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It is shown that the chiral ligand glutathione can induce active surface growth in the deposition of Au on Au nanoplates, forming nano‐badges with complex surface patterns. The special feature of the growth mode is that the growth materials are diverted to a few active sites, causing deep valleys and high standing walls. The circular dichroism signal depends on the tilting degree of the walls, which likely arises from the different packing of the chiral ligands on the two pro‐chiral slopes. As a characteristic sign of the Active Surface Growth mode, low seed concentration is used to promote the rate of deposition, which expands the ridge–valley competition favoring growth at the active sites. The understanding and rational control of the chiral ridges will advance the synthetic control for chiral nanostructures. [ABSTRACT FROM AUTHOR]

Molecular metal oxo or oxo/alkoxo clusters, MwOx(OH/OR)y(L/X)z (L or X = organic ligands), can often be isolated upon (partial) hydrolysis of metal alkoxides. Investigation of such clusters leads to a better understanding of the basic processes of sol–gel chemistry. The ligands not only stabilize the cluster core but also influence to some extent the cluster structures. They can easily change their position on the cluster surface, thus adapting to changing cluster geometries, and can be exchanged under certain conditions. A close inspection of titanium oxo/alkoxo cluster structures, taken as an informative example, shows that Ti3O units (with or without organic ligands) are the basic building blocks. Clusters with higher nuclearities appear to be predominantly formed by cluster–cluster or by cluster–monomer condensations. Ligand substitution or condensation reactions within a cluster unit are also possible. Highlights: Comparison of metal oxo cluster structures allows conclusions on the mechanisms by which the clusters might be formed or modified. Organic ligands protecting the cluster core are dynamic and can be exchanged. Organic ligands influence the cluster structure. Ti3O units are the basic building blocks in titanium oxo clusters. [ABSTRACT FROM AUTHOR]

Understanding the dynamics of ligands bound to proteins is an important task in medicinal chemistry and drug design. However, the dominant technique for determining protein–ligand structures, X‐ray crystallography, does not fully account for dynamics and cannot accurately describe the movements of ligands in protein binding sites. In this article, an alternative method, ensemble refinement, is used on six protein–ligand complexes with the aim of understanding the conformational diversity of ligands in protein crystal structures. The results show that ensemble refinement sometimes indicates that the flexibility of parts of the ligand and some protein side chains is larger than that which can be described by a single conformation and atomic displacement parameters. However, since the electron‐density maps are comparable and Rfree values are slightly increased, the original crystal structure is still a better model from a statistical point of view. On the other hand, it is shown that molecular‐dynamics simulations and automatic generation of alternative conformations in crystallographic refinement confirm that the flexibility of these groups is larger than is observed in standard refinement. Moreover, the flexible groups in ensemble refinement coincide with groups that give high atomic displacement parameters or non‐unity occupancy if optimized in standard refinement. Therefore, the conformational diversity indicated by ensemble refinement seems to be qualitatively correct, indicating that ensemble refinement can be an important complement to standard crystallographic refinement as a tool to discover which parts of crystal structures may show extensive flexibility and therefore are poorly described by a single conformation. However, the diversity of the ensembles is often exaggerated (probably partly owing to the rather poor force field employed) and the ensembles should not be trusted in detail. [ABSTRACT FROM AUTHOR]

The dynamic behavior of the N, N, N′, N′-tetramethylethylenediamine (tmeda) ligand has been studied in solid lithium-fluorenide(tmeda) ( 3) and lithium-benzo[ b]fluorenide(tmeda) ( 4) using CP/MAS solid-state 13C- and 15N-NMR spectroscopy. It is shown that, in the ground state, the tmeda ligand is oriented parallel to the long molecular axis of the fluorenide and benzo[ b]fluorenide systems. At low temperature (<250 K), the 13C-NMR spectrum exhibits two MeN signals. A dynamic process, assigned to a 180° rotation of the five-membered metallacycle ( π-flip), leads at elevated temperatures to coalescence of these signals. Line-shape calculations yield Δ H‡=42.7 kJ mol−1, Δ S‡=−5.3 J mol−1 K−1, and $\rm{\Delta G_{298}^{\ddag}}$=44.3 kJ mol−1 for 3, and Δ H‡=36.8 kJ mol−1, Δ S‡=−17.7 J mol−1 K−1, and $\rm{\Delta G_{298}^{\ddag}}$=42.1 kJ mol−1 for 4, respectively. A second dynamic process, assigned to ring inversion of the tmeda ligand, was detected from the temperature dependence of T1 ρ, the 13C spin-lattice relaxation time in the rotating frame, and led to Δ H‡=24.8 kJ mol−1, Δ S‡=−49.2 J mol−1 K−1, and $\rm{\Delta G_{298}^{\ddag}}$=39.5 kJ mol−1 for 3, and Δ H‡=18.2 kJ mol−1, Δ S‡=−65.3 J mol−1 K−1, and $\rm{\Delta G_{298}^{\ddag}}$=37.7 kJ mol−1 for 4, respectively. For (D12)- 3, the rotation of the CD3 groups has also been studied, and a barrier Ea of 14.1 kJ mol−1 was found. [ABSTRACT FROM AUTHOR]

Pin1 is a modular enzyme that accelerates the cis-trans isomerization of phosphorylated-Ser/Thr-Pro (pS/T-P) motifs found in numerous signaling proteins regulating cell growth and neuronal survival. We have used NMR to investigate the interaction of Pin1 with three related ligands that include a pS-P substrate peptide, and two pS-P substrate analogue inhibitors locked in the cis and trans conformations. Specifically, we compared the ligand binding modes and binding-induced changes in Pin1 side-chain flexibility. The cis and trans binding modes differ, and produce different mobility in Pin1. The cis-locked inhibitor and substrate produced a loss of side-chain flexibility along an internal conduit of conserved hydrophobic residues, connecting the domain interface with the isomerase active site. The trans-locked inhibitor produces a weaker conduit response. Thus, the conduit response is stereoselective. We further show interactions between the peptidyl-prolyl isomerase and Trp-Trp (WW) domains amplify the conduit response, and alter binding properties at the remote peptidyl-prolyl isomerase active site. These results suggest that specific input conformations can gate dynamic changes that support intraprotein communication. Such gating may help control the propagation of chemical signals by Pin1, and other modular signaling proteins. [ABSTRACT FROM AUTHOR]