Allostery and molecular stripping mechanism in profilin regulated actin filament growth

Profilin is an actin-sequestering protein and plays key role in regulating the polarized growth of actin filament. Binding of profilin to monomeric actin (G-actin) allows continuous elongation at the barbed end, but not the pointed end, of filament. How G-actin exchanges between the profilin-sequestered state and the filament state (F-actin) to support the barbed end elongation is not well understood. Here, we investigate the involved molecular mechanism by constructing a multi-basin energy landscape model and performing molecular simulations. We showed that the actin exchanging occurs by forming a ternary complex. The interactions arising from the barbed end binding drive the conformational change of the attached G-actin in the ternary complex from twist conformation to more flatten conformation without involving the change of nucleotide state, which in turn destabilizes the actin-profilin interface and promotes the profilin stripping event through allosteric coupling. We also showed that attachment of free profilin to the barbed end induces conformational change of the barbed end actin and facilitates its stripping from the filament. These results suggest a molecular stripping mechanism of the polarized actin filament growth dynamics controlled by the concentrations of the actin-profilin dimer and the free profilin, in which the allosteric feature of the monomeric actin plays crucial role.

Crystal structure of (+)-(1S,5S,6S,7S,10S,11S,16S)-16-hydroxy-7-(methoxymethoxy)-11,15,18,18-tetramethyl-3,13-dioxo-2,4-dioxatetracyclo[12.3.1.01,5.06,11]octadec-14-en-10-yl benzoate

In the fused tetracyclic system of the title compound, C29H36O9, the five-membered dioxolane ring adopts a twist conformation; the two adjacent C atoms deviate alternately from the mean plane of the other three atoms by −0.252 (6) and 0.340 (6) Å. The cyclohexane, cyclohexene and central cyclooctane rings show chair, half-chair and boat-chair forms, respectively. There are three intramolecular C—H...O interactions supporting the molecular conformation, with one S(6) and two S(7) graph-set motifs. In the crystal, intermolecular O—H...O hydrogen bonds connect the molecules into a helical chain running along the c-axis direction, generating a C(7) graph-set motif. The chains are further linked by intermolecular C—H...O interactions to construct a three-dimensional network. There is no valid C—H...π interaction.

Dual versus normal TADF of pyridines ornamented with multiple donor moieties and their performance in OLEDs

Pyridine ring in novel dicyanopyridines exists in a twist-conformation in solid state. Green and orange OLEDs with 3,6-di-tert-butyl-carbazole-containing emitter exhibiting normal TADF, showed high maximum EQE of 25%.

Crystal and molecular structures of dichloridopalladium(II) containing 2-methyl- or 2-phenyl-8-(diphenyphosphanyl)quinoline

The crystal structures of dichloridopalladium(II) complexes bearing 2-methyl- and 2-phenyl-8-(diphenylphosphanyl)quinoline, namely, dichlorido[8-(diphenylphosphanyl)-2-methylquinoline-κ2 N,P]palladium(II), [PdCl2(C22H18NP)] (1) and dichlorido[8-(diphenylphosphanyl)-2-phenylquinoline-κ2 N,P]palladium(II), [PdCl2(C27H20NP)] (2), were analyzed and compared to that of the 8-(diphenylphosphanyl)quinoline (PQH) analogue (3). In all three complexes, the phosphanylquinoline moiety acts as a bidentate P,N-donating chelate ligand. In the PQH complex (3), the PdII center has a typical planar coordination environment; however, both the methyl- and phenyl-substituted phosphanylquinoline (PQMe and PQPh, respectively) complexes (1) and (2) exhibit a considerable tetrahedral distortion around the PdII center, as parameterized by the τ4 values of 0.1555 (4) and 0.1438 (4) for (1) and (2), respectively. The steric interaction from the substituted group introduced at the 2-position of the quinoline ring enforces the cis-positioned Cl ligand to be displaced from the ideal coordination plane. Also, the ideally planar phosphanylquinoline five-membered chelate ring shows a large bending deformation by the displacement of the PdII center from the quinoline plane. In addition, in the phenyl-substituted complex (3), the coordinating quinolyl and the substituted phenyl rings are not co-planar to each other, having a dihedral angle of 33.08 (7)°. This twist conformation prohibits any intermolecular π–π stacking interaction between the quinoline planes, which is observed in the crystals of complexes (1) and (2).

DNA size in confined environments

For short DNA molecules in crowded environments, we evaluate macroscopic parameters such as the average end-to-end distance and the twist conformation by tuning the strength of the site specific confinement driven by the crowders.

Bis(pyrrolidinium) hexachloridostannate: a redetermination

The crystal structure of the title compound, (C4H10N)2[SnCl6], has been redetermined at 180 K. All atoms were located with higher precision than the previous structure determined at room temperature [Ishida et al. (2000). J Mol. Struct. 524, 95–103]. In the crystal, the SnIV atom is located on a special position of site symmetry 2/m and is coordinated by six Cl atoms in a pseudo-octahedral geometry. Of the six Cl atoms, two equivalent axial atoms lie on the mirror plane [Sn—Cl = 2.4281 (6) Å] and the other four equivalent equatorial atoms lie on general positions [Sn—Cl = 2.4285 (4) Å]. The N atom of the pyrrolidinium cation lies on a mirror plane and the other atoms of the cation are disordered over two sites with respect to the mirror plane. Each component of the disordered five-membered rings adopts a twist conformation. The cations and anions are connected via N—H...Cl hydrogen bonds, forming a tape-like structure propagating along [010].

Chloridobis(ethane-1,2-diamine)(4H-1,2,4-triazole-κN1)cobalt(III) dichloride

In the title complex, [CoIIICl(C2H8N2)2(C2H3N3)]Cl2, the CoIIIion has a distorted octahedral environment. It is surrounded by four N atoms in the equatorial plane, with another N atom and a Cl atom occupying the axial positions. Both five-membered Co—N—C—C—N rings adopt a twist conformation. The Co—N bond lengths range from 1.941 (2) to 1.954 (1) Å, while the Co—Cl bond length is 2.257 (1) Å. In the crystal, molecules are linked by N—H...N, N—H...Cl and C—H...Cl hydrogen bonds. Dimers are formed by N—H...Cl hydrogen-bonding interactions between amine H-atom donors and chloride ions resulting in anR42(8) ring motif. These dimers are further connected in a head-to-tail fashionviaN—H...Cl and C—H...Cl hydrogen bonds. All the interactions together combine to link the molecules into a three-dimensional framework.

5′-Benzylidene-1′′-methyl-4′′-phenyltrispiro[1,3-dioxolane-2,1′-cyclohexane-3′,3′′-pyrrolidine-2′′,3′′′-indole]-4′,2′′′-dione

In the title compound, C32H30N2O4, two spiro links connect the methyl-substituted pyrrolidine ring to the oxindole and cyclohexanone rings. The cyclohexanone ring is further connected to the dioxalane ring by a third spiro junction. Both the pyrrolidine and dioxalane rings adopt a twist conformation. The indole ring is nearly planar, with a maximum deviation of 0.0296 (7) Å, and the cyclohexanone ring adopts a distorted boat conformation. In the crystal, C—H...O and N—H...N hydrogen-bonding interactions connect molecules into chains running parallel to thebaxis, which are further linked into layers parallel to theabplane by C—H...O hydrogen bonds.

Crystal structure of methyl 3′-benzamido-4′-(4-methoxyphenyl)-1′-methylspiro[indeno[1,2-b]quinoxaline-11,2′-pyrrolidine]-3′-carboxylate

In the title compound, C35H30N4O3, the spiro C atom connects the five-membered pyrrolidine ring and the indenoquinoxaline ring system. The pyrrolidine ring adopts a twist conformation. An intramolecular N—H...N interaction between the amino group and the pyrazine ring is observed. In the crystal, molecules are linked by a pairs of C—H...O hydrogen bonds, forming inversion dimers.

Crystal structures of two substituted thiazolidine derivatives

In the first of the compounds reported herein, namely 6′-ferrocenyl-6a′-nitro-6′,6a′,6b′,7′,9′,11a′-hexahydro-2H-spiro[acenaphthylene-1,11′-chromeno[3′,4′:3,4]pyrrolo[1,2-c]thiazol]-2-one, [Fe(C5H5)(C29H21N2O4S)], (I), the thiazolidine ring adopts a twist conformation on the methine N—C atoms. In the second compound,viz.6′-(4-methoxyphenyl)-6a′-nitro-6′,6a′,6b′,7′,9′,11a′-hexahydro-2H-spiro[acenaphthylene-1,11′-chromeno[3′,4′:3,4]pyrrolo[1,2-c]thiazol]-2-one, [Fe(C5H5)(C26H19N2O5S)], (II), the thiazolidine ring adopts an envelope conformation with a methine C atom as the flap. In both compounds, the pyrrolidine ring adopts a twist conformation on the thiazolidine and tetrahydropyran C atoms. The mean planes of the thiazolidine and pyrrolidine rings subtend angles of 67.30 (1) and 62.95 (7)° in (I) and (II), respectively, while the mean plane of the pyrrolidine ring makes dihedral angles of 76.53 (1) and 87.74 (7)° with the acenaphthylene ring system in (I) and (II), respectively. In both compounds, an intramolecular C—H...O hydrogen bond forms anS(7) ring motif. In the crystal of (I), molecules are linkedviatwo different C—H...O hydrogen bonds, forming chains along [001] and [100]. In (II), they are linked through C—H...O hydrogen bonds, forming dimers with anR22(10) ring motif while C—H...π interactions link the molecules in a head-to-tail fashion, forming chains along thea-axis direction.