Synthesis, Characterization, and Copper(II) Chelates of 1,11-Dithia-4,8-diazacyclotetradecane.

Synthesis of 1,11-dithia-4,8-diazacyclotetradecane (L1), a constitutional isomer of the macrocyclic [14]aneN2S2 series, is accompanied with reaction and method optimization. Chelation of L1 with copper(II) provided assessment of lattice packing, ring contortion, and evidence of conformational fluxionality in solution through two unique crystal structures: L1Cu(ClO4)2 and [(L1Cu)2µ-Cl](ClO4)3. Multiple synthetic approaches are presented, supplemented with reaction methodology and reagent screening to access [14]aneN2S2 L1. Reductive alkylation of bis-tosyl-cystamine was integrated into the synthetic route, eliminating the use and isolation of volatile thiols and streamlining the synthetic scale-up. Late-stage cleavage of protecting sulfonamides was addressed using reductive N-S cleavage to furnish macrocyclic freebase L1.

Lone-Pair-Induced Topicity Observed in Macrobicyclic Tetra-thia Lactams and Cryptands: Synthesis, Spectral Identification, and Computational Assessment.

The synthesis of a rigid macrobicyclic N,S lactam L1 and a topologically favored in/in N,S cryptand L2 are reported with X-ray structure analysis, dynamic correlation NMR spectroscopy, and computational analysis. Lactam L1 exhibits two distinct rotameric conformations (plus their enantiomeric counterparts) at 25 °C, as confirmed via NMR spectroscopy and computational analysis. Coalescence of the resonances of L1 was observed at 115 °C, allowing for complete nuclei to frequency correlation. Combining computational investigations with experimental data, topological equilibria and relative energies/strain relating to the perturbation of the pore were determined. Due to the increased conformational strain of the N2S2 template, the nitrogen lone pairs in L2 elicit a unique transannular interaction, resulting in a thermodynamically favored in/in nephroidal racemate. The combination of preferred topology, steric relief, and electronic localization of L2 induces a chiral environment imparted through the amine with a computed inversion barrier of 10.3 kcal mol-1.

Reversal of RNA polymerase II ubiquitylation by the ubiquitin protease Ubp3.

The final outcome of protein polyubiquitylation is often proteasome-mediated proteolysis, meaning that "proofreading" of ubiquitylation by ubiquitin proteases (UBPs) is crucial. Transcriptional arrest can trigger ubiquitin-mediated proteolysis of RNA polymerase II (RNAPII) so a UBP reversing RNAPII ubiquitylation might be expected. Here, we show that Ubp3 deubiquitylates RNAPII in yeast. Genetic characterization of ubp3 cells is consistent with a role in elongation, and Ubp3 can be purified with RNAPII, Def1, and the elongation factors Spt5 and TFIIF. This Ubp3 complex deubiquitylates both mono- and polyubiquitylated RNAPII in vitro, and ubp3 cells have elevated levels of ubiquitylated RNAPII in vivo. Moreover, RNAPII is degraded faster in a ubp3 mutant after UV irradiation. Problems posed by damage-arrested RNAPII are thought to be resolved either by removing the damage or degrading the polymerase. In agreement with this, cells with compromised DNA repair are better equipped to survive UV damage when UPB3 is deleted.

Ca2+/Calmodulin-dependent kinase II signaling causes skeletal overgrowth and premature chondrocyte maturation.

The long bones of vertebrate limbs originate from cartilage templates and are formed by the process of endochondral ossification. This process requires that chondrocytes undergo a progressive maturation from proliferating to postmitotic prehypertrophic to mature, hypertrophic chondrocytes. Coordinated control of proliferation and maturation regulates growth of the skeletal elements. Various signals and pathways have been implicated in orchestrating these processes, but the underlying intracellular molecular mechanisms are often not entirely known. Here we demonstrated in the chick using replication-competent retroviruses that constitutive activation of Calcium/Calmodulin-dependent kinase II (CaMKII) in the developing wing resulted in elongation of skeletal elements associated with premature differentiation of chondrocytes. The premature maturation of chondrocytes was a cell-autonomous effect of constitutive CaMKII signaling associated with down-regulation of cell-cycle regulators and up-regulation of chondrocyte maturation markers. In contrast, the elongation of the skeletal elements resulted from a non-cell autonomous up-regulation of the Indian hedgehog responsive gene encoding Parathyroid-hormone-related peptide. Reduction of endogenous CaMKII activity by overexpressing an inhibitory peptide resulted in shortening of the skeletal elements associated with a delay in chondrocyte maturation. Thus, CaMKII is an essential component of intracellular signaling pathways regulating chondrocyte maturation.

Ovarian cancer activity of cyclic amine and thiaether metal complexes.

A thiaether metal complex 1-aza-4,7-dithiacyclononane-RhCl3, 2, and cyclic amine metal complexes tacn-CuBr2, 3, and Me3tacn-RuCl3, 4, have been evaluated for anticancer activity against the ovarian cancer cell line NuTu-19 and for cell toxicity against the noncancerous ovarian tissue cell line OVepi. Specifically, metal complex 2 is active when compared to cisplatin at micromolar concentrations using the MTT and cell invasion assay. The in vitro results reported warrant further evaluation of metal complex 2 in living systems.

Blue copper protein analogue: synthesis and characterization of copper complexes of the N2S2 macrocycle 1,8-dithia-4,11-diazacyclotetradecane.

To improve understanding of copper at the active site of Type 1 copper proteins, Cu(I) and Cu(II) complexes of 1,8-dithia-4,11-diazacyclotetradecane, shown in , have been successfully isolated and structurally characterized by X-ray crystallography. In these compounds, both Cu(I) and Cu(II) are centered in the plane of the macrocycle containing two sulphur and two nitrogen heteroatoms comprising the distorted tetrahedral/square planar coordination geometry. The UV/VIS spectra, electrochemistry and EPR properties have been obtained for the Cu(II) complex 2. Three absorption bands at 295 nm, 354 nm, and 545 nm are observed in aqueous solution at a pH of 5. These bands have been assigned to the N → Cu(II) and S → Cu(II) charge transfer bands and the d-d transitions respectively. The Cu(I/II) redox midpoint potential of complex 2 in CH3CN is +403 mV versus NHE.

Facile peripheral modification of N-confused porphyrin.

[reaction: see text] An improved methodology for the N-alkylation of the porphyrin isomer N-confused porphyrin is presented. The combination of polar solvent conditions and the use of the base Cs2CO3 affords externally modified products in high yield without separation difficulties and without the use of large excesses of alkylating reagent. The further transformation and metalation of these products provides opportunities for the construction of metalloenzyme model complexes, peptide adducts, and chromophore assemblies.