Overcoming GNA/RNA base-pairing limitations using isonucleotides improves the pharmacodynamic activity of ESC+ GalNAc-siRNAs.

We recently reported that RNAi-mediated off-target effects are important drivers of the hepatotoxicity observed for a subset of GalNAc-siRNA conjugates in rodents, and that these findings could be mitigated by seed-pairing destabilization using a single GNA nucleotide placed within the seed region of the guide strand. Here, we report further investigation of the unique and poorly understood GNA/RNA cross-pairing behavior to better inform GNA-containing siRNA design. A reexamination of published GNA homoduplex crystal structures, along with a novel structure containing a single (S)-GNA-A residue in duplex RNA, indicated that GNA nucleotides universally adopt a rotated nucleobase orientation within all duplex contexts. Such an orientation strongly affects GNA-C and GNA-G but not GNA-A or GNA-T pairing in GNA/RNA heteroduplexes. Transposition of the hydrogen-bond donor/acceptor pairs using the novel (S)-GNA-isocytidine and -isoguanosine nucleotides could rescue productive base-pairing with the complementary G or C ribonucleotides, respectively. GalNAc-siRNAs containing these GNA isonucleotides showed an improved in vitro activity, a similar improvement in off-target profile, and maintained in vivo activity and guide strand liver levels more consistent with the parent siRNAs than those modified with isomeric GNA-C or -G, thereby expanding our toolbox for the design of siRNAs with minimized off-target activity.

A Heterometallic Three-Dimensional Metal-Organic Framework Bearing an Unprecedented One-Dimensional Branched-Chain Secondary Building Unit.

A heterometallic metal-organic framework (MOF) of [Cd6Ca4(BTB)6(HCOO)2(DEF)2(H2O)12]∙DEF∙xSol (1, H3BTB = benzene-1,3,5-tribenzoic acid; DEF = N,N'-diethylformamide; xSol. = undefined solvates within the pore) was prepared by solvothermal reaction of Cd(NO3)2·4H2O, CaO and H3BTB in a mixed solvent of DEF/H2O/HNO3. The compatibility of these two divalent cations from different blocks of the periodic table results in a solid-state structure consisting of an unusual combination of a discrete V-shaped heptanuclear cluster of [Cd2Ca]2Ca' and an infinite one-dimensional (1D) chain of [Cd2CaCa']n that are orthogonally linked via a corner-shared Ca2+ ion (denoted as Ca'), giving rise to an unprecedented branched-chain secondary building unit (SBU). These SBUs propagate via tridentate BTB to yield a three-dimensional (3D) structure featuring a corner-truncated P41 helix in MOF 1. This outcome highlights the unique topologies possible via the combination of carefully chosen s- and d-block metal ions with polydentate ligands.

Dual Emission in a Ligand and Metal Co-Doped Lanthanide-Organic Framework: Color Tuning and Temperature Dependent Luminescence.

In this study, we report the luminescence color tuning in the lanthanide metal-organic framework (LnMOF) ([La(bpdc)Cl(DMF)] (1); bpdc2- = [1,1'-biphenyl]-4,4'-dicarboxylate, DMF = N,N-dimethylformamide) by introducing dual emission properties in a La3+ MOF scaffold through doping with the blue fluorescent 2,2'-diamino-[1,1'-biphenyl]-4,4'-dicarboxylate (dabpdc2-) and the red emissive Eu3+. With a careful adjustment of the relative doping levels of the lanthanide ions and bridging ligands, the color of the luminescence was modulated, while at the same time the photophysical characteristics of the two chromophores were retained. In addition, the photophysical properties of the parent MOF (1) and its doped counterparts with various dabpdc2-/bpdc2- and Eu3+/La3+ ratios and the photoinduced energy transfer pathways that are possible within these materials are discussed. Finally, the temperature dependence study on the emission profile of a doped analogue containing 10% dabpdc2- and 2.5% Eu3+ (7) is presented, highlighting the potential of this family of materials to behave as temperature sensors.

Study on the potential way of hepatic cytotoxicity of N,N-dimethylformamide.

The intermediate metabolites and redox status imbalance were supported as the two major points for N,N-dimethylformamide (DMF)-induced hepatotoxicity. However, the potential mechanism has not yet been concerned. By applying two inhibitors, this study tried to seek the major role in DMF-induced toxicity on HL7702 cell. We observed that DMF induced cell apoptosis through mitochondrial-dependent and p53 pathway. Inhibition reactive oxygen species by catalase remarkably attenuated the mitochondrial transmembrane potential (MMP), apoptotic proteins, and apoptosis. On the contrary, it reduced the biodegradation rate of DMF by coincubation with CYP2E1 antagonist (DDC) partially reduced late apoptosis. However, the change in MMP, the ratio of Bax to Bcl-xl, and cleaved-caspase 9 was not attenuated by DDC. The pathway in DDC coincubation groups was related to the p53 rather than the mitochondrial pathway. Restoring the redox balance during biodegradation is much more effective than attenuating the metabolite rate of DMF. This study may provide a suitable prevention method to occupational workers.

DBU-catalyzed, aromatization-oriented, regioselective domino synthesis of 2-aminopyrimidines from ß-dicarbonyl compounds, DMF-DMA, and cyanamide.

A multicomponent domino synthesis has been developed for the preparation of 2-aminopyrimidines from ß-dicarbonyl compounds, N,N-dimethylformamide dimethyl acetal, and cyanamide. The protocol was used for the regioselective preparation of 4-amide/ester/ketone substituted 2-aminopyrimidines. Twelve 2-aminopyrimidines were isolated in good yields (56-93%).

Nanoscale MnII -Coordination Polymers for Cell Imaging and Heterogeneous Catalysis.

A mixed ligand approach was exploited to synthesize a new series of MnII -based coordination polymers (CPs), namely, CP1 {[Mn(µ-dpa)(µ-4,4'-bp)]⋅MeOH}∞ , CP2 {[Mn3 (µ-dpa)3 (2,2'-bp)2 ]}∞ , CP3 {[Mn3 (µ-dpa)3 (1,10-phen)2 ]⋅2 H2 O}∞ , CP4 {[Mn(µ-dpa)(µ-4,4'-bpe)1.5 ]⋅H2 O}∞ , CP5 {[Mn2 (µ-dpa)2 (µ-4,4'-bpe)2 ]⋅1/2 DEF}∞ , and CP6 {[Mn(µ-dpa)(µ-4,4'-bpe)1.5 ]⋅1/2 DMA}∞ (dpa=3,5-dicarboxyphenyl azide, 2,2'-bp=2,2'-bipyridine, 1,10-phen=1,10-phenanthroline, 4,4'-bpe=1,2-bis(4-pyridyl)ethylene, 4,4'-bp=4,4'-bipyridine, DEF=N,N-diethylformamide, DMA=N,N-dimethylacetamide), to develop multifunctional CPs. Various techniques, such as single-crystal X-ray diffraction (SXRD), FTIR spectroscopy, elemental analysis, and thermogravimetric analysis, were employed to fully characterize these CPs. The majority of the CPs displayed a four-connected sql topology, whereas CP4 and CP6 exhibited a two-dimensional SnS network architecture, which was further entangled in a polycatenation mode. Compound CP1 displayed an open framework structure. The CPs were scaled down to the nanoregime in a ball mill for cell imaging studies. Whereas CP2 and CP4 were employed for cell imaging with RAW264.7 cells, CP1 was exploited for both cell imaging and heterogeneous catalysis in a cyanosilylation reaction.

Cross-sectional study on N,N-dimethylformamide (DMF); effects on liver and alcohol intolerance.

PURPOSE: There are still concerns regarding occupational exposure to hepatotoxic DMF. This study was designed to evaluate possible liver damaging effects of DMF under current workplace conditions in synthetic fibres industries. METHODS: Among other laboratory parameters, liver function parameters (alkaline phosphatase (ALP), aspartate aminotransferase, alanine aminotransferase and gamma-glutamyltransferase), the mean corpuscular erythrocyte volume (MCV) and carbohydrate-deficient transferrin (CDT) of the workforce of two companies present at the days of study were investigated. Internal exposure to DMF was assessed via three different biomarkers [sum of N-methylformamide and N-hydroxymethyl-N-methylformamide, N-acetyl-S-(N-carbamoyl)cysteine (AMCC) and 3-methyl-5-isopropylhydantoin (MIH)]. Alcohol consumption was assessed by means of direct ethanol metabolites (ethylglucuronide and ethylsulfate). RESULTS: None of the tested liver enzyme activities showed a positive association with any of the three exposure markers, nor did CDT and MCV. CDT was negatively associated with AMCC and the ALP activity negatively with all three exposure markers. Changes in liver function are seen mainly in conjunction with ethanol consumption but also with increasing body weight and age. MCV was associated with smoking. Almost half of the workers stated to experience alcohol flush reaction. CONCLUSION: The present study indicates that long-term exposure to DMF, which was specified by median urinary AMCC levels of 4.84 mg/g creatinine and DMF haemoglobin adduct levels of 60.5 nmol/MIH/g globin, respectively, does not result in any adverse liver effects. In contrast, these DMF exposure levels still elicit certain alcohol intolerance reactions.

DMF Dimethyl Acetal as Carbon Source for α-Methylation of Ketones: A Hydrogenation-Hydrogenolysis Strategy of Enaminones.

A novel heterogeneous catalytic hydrogenation-hydrogenolysis strategy has been developed for the α-methylation of ketones via enaminones using DMF dimethyl acetal as carbon source. This strategy provides a very convenient route to α-methylated ketones using a variety of ketones without any base or oxidant.

Stitching 2D polymeric layers into flexible interpenetrated metal-organic frameworks within single crystals.

A 2D coordination polymer prepared with bulky diethylformamide solvates exhibits channels which allow dipyridyl bridging ligands to diffuse into the crystal lattice. The absorbed dipyridyls thread through the pores of one layer and substitute the surface diethylformamide molecules on the neighboring layers to stitch alternate layers to form flexible interpenetrated metal-orgaic frameworks. The threading process also results in exchange of the bulky diethylformamide solvates for aqua to minimize congestion and, more strikingly, forces the slippage of two-dimensional layers, while still maintaining crystallinity.

An amphiphilic, catalytically active, vitamin B12 derivative.

We performed the reaction of vitamin B12 with N,N-dimethylformamide dimethyl acetal for primary amide activation, and added MeOH as a nucleophile, to afford cobalester, the first amphiphilic cobalamin derivative. The unique combination of redox properties and solubility represents an asset for its use as a catalyst in C-C bond forming reactions.

Metal-catalyzed reduction of HCONR'2, R' = Me (DMF), Et (DEF), by silanes to produce R'2NMe and disiloxanes: a mechanism unraveled.

We demonstrate that using Mo(CO)(6), Mo(CO)(5)NMe(3), and (η(5)-C(5)H(5))Mn(CO)(3) as catalysts for the silane, R(3)SiH, reduction of N,N-dimethylformamide (DMF), and N,N-diethylformamide (DEF), we can observe, intercept, and isolate, the important siloxymethylamine intermediates, R(3)SiOCH(2)NR'(2), R' = Me, Et, for the first time. In the presence of excess DMF such intermediates thermally react with a variety of silanes to form the corresponding disiloxanes in the absence of a metal catalyst. We also show that the germanium hydrides, Et(3)GeH and Bu(3)GeH, also reduce DMF to form trimethylamine and the corresponding digermoxane but observe no intermediates R(3)GeOCH(2)NMe(2). Bu(3)SnH reduces DMF, but along with the low yields of Bu(3)SnOSnBu(3) (but no Bu(3)SnOCH(2)NMe(2)) significant side products are obtained including (Bu(3)Sn)(2) and Bu(4)Sn. In the absence of DMF the siloxymethylamines can undergo metal-catalyzed reactions with silanes, germanes and stannanes to form disiloxanes, and R(3)SiOER(3) E = Ge, Sn, respectively. To date, the most efficient catalyst for this latter process is (η(5)-C(5)H(5))Mo(CO)(3)CH(3) via a photochemical reaction.

Oxidative modification of rat sulfotransferase 1A1 activity in hepatic tissue slices correlates with effects on the purified enzyme.

Mammalian cytosolic sulfotransferases (SULTs) catalyze the sulfation of xenobiotics as well as numerous endogenous molecules. The major aryl (phenol) SULT in rat liver, rSULT1A1, has been used extensively as a model enzyme for understanding the catalytic function of SULTs. Previous studies showed that purified rSULT1A1 displays significant catalytic changes in the presence of GSSG and other oxidants. In the present study, the effects of diamide [1,1'-azobis(N,N-dimethylformamide)] and tert-butyl hydroperoxide (TBHP) on the activity of rSULT1A1 in rat hepatic slices were compared with the effects of these oxidants on a homogeneous preparation of the enzyme. Precision-cut hepatic slices were incubated with 10 µM 7-hydroxycoumarin (7-HC) in the presence of varied concentrations of either diamide or TBHP. Analysis of the 7-hydroxycoumarin sulfate released into the incubation medium indicated that both oxidants significantly increased the sulfation of 7-HC, and this occurred at optimal concentrations of 5 and 10 µM, respectively. Cellular GSH and GSSG levels in the hepatic slices were not significantly altered from control values at these concentrations of diamide and TBHP. Exposure of homogeneous rSULT1A1 to diamide or TBHP also increased the rate of sulfation of 7-HC, although the optimal concentrations of diamide and TBHP were lower (50- and 100-fold, respectively) than those required for effects with the hepatic slices. These results indicate that both diamide and TBHP may modify the rSULT1A1 in intact cells in a manner similar to that observed with the homogeneous purified enzyme.

Lack of correlation between catalytic efficiency and basicity of amines during the reaction of aryl methyl ketones with DMF-DMA: an unprecedented supramolecular domino catalysis.

1-Methylimidazole exhibits an unusually high efficiency in promoting the reaction of aryl methyl ketones with DMF-DMA to form (2E)-1-aryl-3-dimethylamino-2-propenones which lacks correlation between the catalytic efficiency and the basicity of 1-methylimidazole in comparison to other amines. An unprecedented supramolecular domino catalysis rationalises the lack of correlation between the catalytic efficiency and basicity of the amines. The supramolecular assemblies have been characterized by mass-spectrometric ion fishing. The time-dependent increase/decrease in the concentration (ion current) of the supramolecular species consolidated the mechanism.

Coordination chemistry study of hydrated and solvated lead(II) ions in solution and solid state.

The coordination chemistry of lead(II) in the oxygen donor solvents water, dimethylsulfoxide (dmso, Me(2)SO), N,N-dimethylformamide (dmf), N,N-dimethylacetamide (dma), N,N'-dimethylpropyleneurea (dmpu), and 1,1,3,3-tetramethylurea (tmu), as well as in the sulfur donor solvent N,N-dimethylthioformamide (dmtf), has been investigated by extended X-ray absorption fine structure (EXAFS) and/or large angle X-ray scattering (LAXS) in solution, and by single crystal X-ray diffraction and/or EXAFS of solid hydrates and solvates. Lead(II) may either form hemidirected complexes with large bond distance distribution and an apparent gap for excess electron density, or holodirected ones with a symmetric coordination sphere with normal bond distance distribution, depending on the strength of antibonding lead 6s/ligand np molecular orbital interactions and ligand-ligand interactions. The crystallographic data show that the solid lead(II) perchlorate and trifluoromethanesulfonate hydrate structures are hemidirected, while the solid lead(II) solvates of dma and dmpu have regular octahedral configuration with holodirected geometry and mean Pb-O bond distances in the range 2.50-2.52 Å. EXAFS data on the hydrated lead(II) ion in aqueous solution show broad bond distance distribution and a lack of inner-core multiple scattering contributions strongly indicating a hemidirected structure. The Pb-O bond distances found both by EXAFS and LAXS, 2.54(1) Å, point to a six-coordinate hydrated lead(II) ion in hemidirected fashion with an unevenly distributed electron density. The results obtained for the dmso solvated lead(II) ion in solution are ambiguous, but for the most part support a six-coordinate hemidirected complex. The mean Pb-O bond distances determined in dmf and dma solution by LAXS, 2.55(1) and 2.48(1) Å, respectively, indicate that in both solvate complexes lead(II) binds six solvent molecules with the former complex being hemidirected whereas the latter is holodirected. The dmpu and tmu solvated lead(II) ions have a regular holodirected octahedral configuration, as expected given their space-demanding characteristics and ligand-ligand intermolecular interactions. The dmtf solvated lead(II) ion in solution is most likely five-coordinate in a hemidirected configuration, with a mean Pb-S bond distance of 2.908(4) Å. New and improved ionic radii for the lead(II) ion in 4-8-coordination in hemi and holodirected configurations are proposed using crystallographic data.

Search for evidence of life in space: analysis of enantiomeric organic molecules by N,N-dimethylformamide dimethylacetal derivative dependant Gas Chromatography-Mass Spectrometry.

Within the context of the future space missions to Mars (MSL 2011 and Exomars 2016), which aim at searching for traces of life at the surface, the detection and quantitation of enantiomeric organic molecules is of major importance. In this work, we have developed and optimized a method to derivatize and analyze chiral organic molecules suitable for space experiments, using N,N-dimethylformamide dimethylacetal (DMF-DMA) as the derivatization agent. The temperature, duration of the derivatization reaction, and chromatographic separation parameters have been optimized to meet instrument design constraints imposed upon space experiment devices. This work demonstrates that, in addition to its intrinsic qualities, such as production of light-weight derivatives and a great resistance to drastic operating conditions, DMF-DMA facilitates simple and fast derivatization of organic compounds (three minutes at 140 degrees C in a single-step) that is suitable for an in situ analysis in space. By using DMF-DMA as the derivatization agent, we have successfully identified 19 of the 20 proteinic amino acids and been able to enantiomerically separate ten of the potential 19 (glycine being non-chiral). Additionally, we have minimized the percentage of racemized amino acid compounds produced by optimizing the conditions of the derivatization reaction itself. Quantitative linearity studies and the determination of the limit of detection show that the proposed method is also suitable for the quantitative determination of both enantiomeric forms of most of the tested amino acids, as limits of detection obtained are lower than the ppb level of organic molecules already detected in Martian meteorites.

A new and facile synthesis of quinazoline-2,4(1H,3H)-diones.

A new and facile preparation of quinazoline-2,4(1H,3H)-diones was first reported which was the condensation of aromatic o-aminonitriles with DMF or N,N-diethylformamide in the presence of ZnCl(2) (0.5-10 mol %) at 190-200 degrees C in the sealed reactor.

Microwave assisted condensation reactions of 2-aryl hydrazonopropanals with nucleophilic reagents and dimethyl acetylenedicarboxylate.

The reaction of methyl ketones 1a-g with dimethylformamide dimethylacetal (DMFDMA) afforded the enaminones 2a-g, which were coupled with diazotized aromatic amines 3a,b to give the corresponding aryl hydrazones 6a-h. Condensation of compounds 6a-h with some aromatic heterocyclic amines afforded iminoarylhydrazones 9a-m. Enaminoazo compounds 12a,b could be obtained from condensation of 6c with secondary amines. The reaction of 6e,h with benzotriazolylacetone yielded 14a,b. Also, the reaction of 6a,b,d-f,h with glycine and hippuric acid in acetic anhydride afforded pyridazinone derivatives 17a-f. Synthesis of pyridazine carboxylic acid derivatives 22a,b from the reaction of 6b,e with dimethyl acetylenedicarboxylate (DMAD) in the presence of triphenylphosphine at room temperature is also reported. Most of these reactions were conducted under irradiation in a microwave oven in the absence of solvent in an attempt to improve the product yields and to reduce the reaction times.

Solvent effects on spectrophotometric titrations and vibrational spectroscopy of 5,10,15-triphenyl-20-(4-hydroxyphenyl)porphyrin in aqueous DMF.

The spectrophotometric titration by sodium hydroxide of 5,10,15-triphenyl-20-(4-hydroxyphenyl)porphyrin ((OH)(1)PH(2)) is studied as a function of solvent composition of DMF-H(2)O binary solvent mixture ([OH(-)]=0.04 M). Combining the structure changes of the porphyrin and the "four orbital" model of Gouterman, many features of the optical spectra of this deprotonated para-hydroxy-substituted tetraphenylporphyrin in different composition of binary solvent mixtures can be rationalized. In highly aqueous solvents, the changes of the titration curves are shown to be mainly due to hydrogen-bonding of the oxygen of the phenoxide anion group by the hydroxylic solvent, Which decreases the energy of the phenoxide anion pi orbital. Thus the phenoxide anion pi orbital cannot cross over the porphyrin pi orbital being a different HOMO. However, its energy is close to that of the porphyrin pi orbitals. As a result, in the visible region, no charge-transfer band is observed, while in the visible-near region, the Soret peak split into two components. In nonaqueous solvents, the changes are mainly attributed to further deprotonation of pyrrolic-Hs of (OH)(1)PH(2) by NaOH and coordination with two sodium ions to form the sodium complex of (OH)(1)PH(2), which turns hyperporphyrin spectra of deprotonated of phenolic-H of (OH)(1)PH(2) into three-banded spectra of regular metalloporphyrin.

Development of a solid phase microextraction-gas chromatography method to determine N-hydroxymethyl-N-methylformamide and N-methylformamide in urine.

A headspace solid phase microextraction (SPME) method has been developed to determine metabolites of dimethylformamide, N-hydroxymethyl-N-methylformamide, and N-methylformamide (NMF) as NMF in urine by gas chromatography with nitrogen-phosphorus detector (GC-NPD). An SPME holder with a 65-microm PDMS/DVB fiber coating was used. Optimal desorption conditions were 250 degrees C for 1 min, adsorption at 80 degrees C for 15 min, and 3.00 mL of sample in the headspace vial. The method presented good resolution, repeatability, recovery, detection limit, ruggedness and response linearity.

Synthesis, characterization, crystal structure and biological activity of a novel heterotetranuclear complex: [NiLPb(SCN)2(DMF)(H2O)]2, bis-{[mu-N,N'-bis(salicylidene)-1,3-propanediaminato-aqua-nickel(II)](thiocyanato)(mu-thiocyanato)(mu-N,N'-dimethylformamide)lead(II)}.

The mononuclear nickel complex NiL (LH2 = N,N'-bis(salicylidene)-1,3-diaminopropane) can be transformed into the tetranuclear complex [NiL(H2O)Pb(SCN)2(DMF)]2 in the aid of SCN-, DMF (dimethylformamide) and Pb(II) ions. The complex was characterized by elemental analysis and FTIR investigation. The crystal structure reveals it is a nonlinear Ni(II)-Pb(II)-Pb(II)i-Ni(II)i (i: 1-x, 1-y, 1-z) heterotetranuclear complex and crystallizes in the triclinic space group P1. The Ni(II) and Pb(II) ions have a distorted octahedral coordination geometry. There are three kinds of mu-bridge in the molecule between the metal ions. Each pair of Ni and Pb ions in the asymmetric unit is equatorially linked by two phenolic oxygen bridging atoms of N,N'-bis(salicylidene)-1,3-propanediaminato (salpd(2-), C17H16N2O2(2-)) ligand. The dinuclear centres from tetranuclear clusters Ni-Pb(i) and Ni(i)-Pb pairs are bridged by two mu-1,3-SCN groups. Pb(II) and Pb(II)i ions are also bridged by the oxygen atoms of DMF molecules. The tetranuclear units are hydrogen bonded by two O-H...N intermolecular interactions along the c-axis. The complex was screened for antibacterial and antifungal activities by the disc diffusion and microtiter plate techniques using DMF as solvent. The minimum inhibitory concentration values were calculated. It has been found that antimicrobial activities of the complexes are higher than the free ligand.