Trans-1,2-bis(diphenylphosphino)ethene as bridging ligand in thione-S-ligated dimeric copper(I) chloride complexes

Several mixed-ligand complexes have been prepared by treatment of copper(I) chloride with equimolar amounts of trans-1,2-bis(diphenylphosphino)ethene (trans-dppen) in acetonitrile followed by the addition of a methanolic solution of one equivalent of a heterocyclic thione (L). The novel complex compounds have been characterized by single-crystal X-ray diffraction, ¹H NMR and IR spectroscopy as well as by elemental analyses and melting points. The X-ray structures of three examples confirm that the compounds are homobimetallic dimers of type [CuCl(μ₂-trans-dppen)(L)]₂ containing two tetrahedral coordination units joined by two trans-dppen bridges.     

Protein trans-Splicing To Produce Herbicide-Resistant Acetolactate Synthase

Protein splicing in trans has been demonstrated both in vivo and in vitro by biochemical and immunological analyses, but in vivo production of a functional protein by trans-splicing has not been reported previously. In this study, we used the DnaE intein from Synechocystis sp. strain PCC6803, which presumably reconstitutes functional DnaE protein by trans-splicing in vivo, to produce functional herbicide-resistant acetolactate synthase II (ALSII) from two unlinked gene fragments in Escherichia coli. The gene for herbicide-resistant ALSII was fused in frame to DnaE intein segments capable of promoting protein splicing in trans and was expressed from two compatible plasmids as two unlinked fragments. Cotransformation of E. coli with the two plasmids led to production of a functional enzyme that conferred herbicide resistance to the host E. coli cells. These results demonstrate the feasibility of expressing functional genes from two unlinked DNA loci and provide a model for the design of nontransferable transgenes in plants.     

Reaction of cis and trans isomers of platinum(II) diamminedichloride with purine,adenine and its derivatives in dilute solutions

Reactions of the cytostatic and antitumour agent, cis-platinum(II) diamminedichloride, and its trans isomer with purine, adenine and its N-9 derivatives were followed spectrophotometrically in dilute aqueous solutions. While the cis isomer formed with all compounds studied complexes with the metal-to-ligand ratios ML, ML₂ and M₂L, it was found that the trans isomer did not form the complexes ML₂ with adenosine and AMP. The values of dissociation constants, reaction rate constants and activation energies of the reactions of the cis and trans isomers with purine, adenine and its derivatives were in most cases comparable. Lower stability was exhibited only by the complexes of trans-platinum(II) diamminedichloride (trans-Pt(II)) with AMP as well as by its complexes M₂L with adenine and adenosine. The ability of cis-platinum(II) diamminedichloride (cis-Pt(II)) to react with two adenine residues can explain the greater tendency of the cis isomer to form intrastrand cross-links in nucleic acids as compared with the trans isomer.     

Rational optimization of the DSL ligase ribozyme with GNRA/receptor interacting modules

The DSL ribozyme is a class of artificial ligase ribozymes with a highly modular architecture, which catalyzes template-directed RNA ligation on a helical substrate module that can be either covalently connected (cis-DSL) or physically separated (trans-DSL) from the catalytic module. Substrate recognition by the catalytic module is promoted by one or two sets of GNRA/receptor interactions acting as clamps in the cis or trans configurations, respectively. In this study, we have rationally designed and analyzed the catalytic and self-assembly properties of several trans-DSL ribozymes with different sets of natural and artificial GNRA-receptor clamps. Two variants newly designed in this study showed significantly enhanced catalytic properties with respect of the original trans-DSL construct. While this work allows dissection of the turnover and catalytic properties of the trans-DSL ribozyme, it also emphasizes the remarkable modularity of RNA tertiary structure for nano-construction of complex functions.     

Cis-trimethoxystilbene,exhibits higher genotoxic and antiproliferative effects than its isomer trans-trimethoxystilbene in MCF-7 and MCF-10A cell lines

Stilbenes are a class of natural compounds with a wide variety of biological effects, such as antitumor activity. The best-known stilbene is resveratrol, whose clinical application is limited due to its low bioavailability. Methoxylated derivatives of this stilbene, including cis-trimethoxystilbene (cis-TMS) and trans-trimethoxystilbene (trans-TMS) have demonstrated more pronounced cytotoxic and anti-proliferative effects than resveratrol. Thus, the objective of this study is to evaluate and compare the cytotoxicity and antiproliferative effects of cis- and trans-TMS in MCF-7 and its normal counterpart MCF-10A. Both compounds were cytotoxic, genotoxic, and induced G2-M accumulation and cell death in the two cell lines. These results suggested that the genotoxicity of cis- and trans-TMS is involved in the reduction of cellular proliferation of MCF-7 and MCF-10A cells, but notably, such antiproliferative effects are more pronounced for cis- than trans-TMS.     

Syntheses and activity of some platinum(IV) complexes with N-methyl derivate of glycine and halogeno ligands against HeLa, K562 cell lines and human PBMC

Four platinum(IV) complexes, trans,trans-dichlorobis(N,N-dimethylglycinato)platinum(IV), trans,trans-[Pt(dmgly)₂Cl₂] (1) and trans,trans-dibromobis(N,N-dimethylglycinato)platinum (IV), trans,trans-[Pt(dmgly)₂Br₂] (2), as well as, trans,trans-dichlorobis(N-methylglycinato)platinum(IV), trans,trans-[Pt(sar)₂Cl₂] (3) and trans,trans-dibromobis(N-methylglycinato)platinum(IV), trans,trans-[Pt(sar)₂Br₂] (4) (with configuration index for all complexes OC-6-14), were synthesized and characterized by elemental analysis, infrared and ¹H NMR spectroscopy. In the aim to assess the selectivity in the antitumor action of these complexes, the antiproliferative action of these compounds was determined to human adenocarcinoma HeLa cells; to human myelogenous leukemia K562 cells and to normal immunocompetent cells; i.e., on human PBMC. The details of the crystal structure synthesized trans,trans-[Pt(sar)₂Br₂] complex were also reported here. In the crystal structure of trans,trans-[Pt(sar)₂Br₂], the Pt(IV) ion had a deformed octahedral coordination with both N-methylglycinates and bromides bonded trans to one another and with the N-Pt-Br bond angles of 84.1(4) and 95.9(4)°. The trans,trans-[Pt(sar)₂Br₂] complex molecules form 2D-layers with multiple N-H?O and C-H?O hydrogen bonds.     

Developmental Effects of Zeatin, Ribosyl-Zeatin, and Agrobacterium tumefaciens B(6) on Certain Mosses

Eight species of mosses studied were divided into two groups on the basis of their developmental responses to ribosyl-trans-zeatin and Agro-bacterium tumefaciens B₆. All eight produced either gametophores or callus on the protonema in response to 6-(γ,γ-dimethylallylamino) purine and trans-zeatin. Three which produced normal gametophores with A. tumefaciens yielded callus or abnormal gametophores with ribosyl-trans-zeatin. Ribosyl-trans-zeatin and A. tumefaciens were relatively ineffective on five other mosses. Characteristics of protonemal growth common to each of these two groups are described.     

Cytotoxic trans-oriented iminoether platinum complexes - Kinetics of binding to DNA oligonucleotides determined by N NMR spectroscopy

The kinetics of reactions between cytotoxic trans-oriented iminoether platinum complexes and DNA oligonucleotides have been studied by 1D and 2D [¹H, ¹⁵N] HMQC NMR spectroscopy. The results for the two isomers of the mono-iminoether compound trans-[PtCl₂(NH₃){E/Z-HNC(OMe)Me}] (trans-E and trans-Z) are compared with those of the bis-iminoether derivative trans-[PtCl₂{E-HNC(OMe)Me}₂] (trans-EE). Earlier we have shown that quite unexpectedly, trans-EE is practically inert towards a central GG residue in a 12-mer double-helical duplex. We now show that the less bulky trans-E and trans-Z compounds do bind to the interior of the duplex [5′-d(G₁G₂T₃A₄C₅C₆G₇G₈ T₉A₁₀C₁₁C₁₂)]₂ which contains terminal and central “hot” GG site. The platination by trans-E and trans-Z is as expected most pronounced for the solvent exposed, terminal GG-step but significantly, competitive binding is also observed for the central GG-step. The rate of platination of the terminal G-sites is almost an order of magnitude larger for the oligomer than for the monomer GMP which was studied for comparison. The role of trans-platinum carrier ligands in influencing the type and rate of formation of adducts with DNA and other relevant biomolecules is discussed.     

The Octatricopeptide Repeat Protein Raa8 Is Required for Chloroplast trans Splicing

The mRNA maturation of the tripartite chloroplast psaA gene from the green alga Chlamydomonas reinhardtii depends on various nucleus-encoded factors that participate in trans splicing of two group II introns. Recently, a multiprotein complex was identified that is involved in processing the psaA precursor mRNA. Using coupled tandem affinity purification (TAP) and mass spectrometry analyses with the trans-splicing factor Raa4 as a bait protein, we recently identified a multisubunit ribonucleoprotein (RNP) complex comprising the previously characterized trans-splicing factors Raa1, Raa3, Raa4, and Rat2 plus novel components. Raa1 and Rat2 share a structural motif, an octatricopeptide repeat (OPR), that presumably functions as an RNA interaction module. Two of the novel RNP complex components also exhibit a predicted OPR motif and were therefore considered potential trans-splicing factors. In this study, we selected bacterial artificial chromosome (BAC) clones encoding these OPR proteins and conducted functional complementation assays using previously generated trans-splicing mutants. Our assay revealed that the trans-splicing defect of mutant F19 was restored by a new factor we named RAA8; molecular characterization of complemented strains verified that Raa8 participates in splicing of the first psaA group II intron. Three of six OPR motifs are located in the C-terminal end of Raa8, which was shown to be essential for restoring psaA mRNA trans splicing. Our results support the important role played by OPR proteins in chloroplast RNA metabolism and also demonstrate that combining TAP and mass spectrometry with functional complementation studies represents a vigorous tool for identifying trans-splicing factors.     

Comparison between Biosynthesis of ent-Kaurene in Germinating Tomato Seeds and Cell Suspension Cultures of Tomato and Tobacco

Biosynthesis of ent-kaurene was investigated in extracts of cell suspension cultures derived from tobacco callus (Nicotiana tabacum L.), tomato callus (Solanum lycopersicum L.), and in germinating tomato seeds. Incubation of extracts derived from the two cell cultures with either isopentenyl pyrophosphate-¹⁴C or with ¹⁴C-labeled mevalonate, followed by alkaline phosphatase hydrolysis, resulted in the formation of trans-geranylgeraniol-¹⁴C and trans-farnesol-¹⁴C. The corresponding pyrophosphates of trans-geranyl-geraniol-¹⁴C and trans-farnesol-¹⁴C were also detected. No detectable amount of ent-kaurene-¹⁴C was produced by these enzymatic preparations when trans-geranylgeranyl-¹⁴C pyrophosphate served as substrate. However, copalyl-¹⁴C pyrophosphate served as a substrate for the production of ent-kaurene. Cell-free extracts derived from germinating tomato seeds catalyzed the formation of ent-kaurene-¹⁴C from mevalonate-¹⁴C, isopentenyl-¹⁴C pyrophosphate, trans-geranylgeranyl-¹⁴C pyrophosphate, and copalyl-¹⁴C pyrophosphate.     

Electroantennogram responses of the male moth, Argyrotaenia velutinana to mixtures of sex pheromone components of the female

Electroantennogram (EAG) responses were recorded from male redbanded leafroller moth, Argyrotaenia velutinana, antennae using mixtures of the three female-produced sex pheromone components: cis-11-tetradecenyl acetate, trans-11-tetradecenyl acetate, and dodecyl acetate (12:Ac). Binary mixtures containing 3%, 8%, and 15% trans in cis elicited significantly higher amplitude responses than other isomeric mixtures as well as pure cis and trans alone. The higher responses to such mixtures were less than additive at high dosages and additive at lower dosages. Receptor adaptation studies using the two isomers support a previous single unit study demonstrating the presence of at least two functionally different receptor sites on male A. velutinana antennae; adaptation to an airstream containing one isomer did not eliminate response to the opposite isomer presented concurrently. An airstream containing the third component, 12:Ac, caused a significant slowing of the recovery rate during the entire recovery period of EAG responses to cis but not trans, suggesting that a possible temporal modulation of neuronal response by 12:Ac may be a means of coding for this component by antennal sensory neurons.     

Studies on fluorescence polarization of 1-acyl-2-cis- or trans-parinaroyl sn-3-glycerophosphorylcholines in model systems and microsomal membranes

Fluorescent lecithin probes containing cis- or trans-parinaric acid (PnA) at the 2-position cis-parinaroylphosphatidylcholine (cis-PnPC) and trans-parinaroyl phosphatidylcholine (trans-PnPC)) showed similar behavior to that of the free cis- or trans-parinaric acids (cis-PnA or trans-PnA) in bilayer vesicles of synthetic saturated lecithins. Transition temperatures detected by cis-PnPc were about 1°C lower than those observed with trans-PnPc. In mixed lecithin vesicles, the trans-PnPc probe monitored a higher temperature melting component than did the cis-probe. Both probes were readily incorporated into microsomal membranes and into sonicated vesicles prepared from the microsomal phospholipids. With either cis- or trans-PnPc no change in polarization ratio was observed for microsomal membranes between 40°C and 0°C but this ratio increased with decreasing temperature between 0°C and ?5°C. However, vesicles of extracted phospholipids showed a continuous increase in polarization ratio with decreasing temperature between 20°C and ?15°C with trans-PnPc and bewteen 5°C and ?15°C with cis-PnPc. These results suggest that the two lecithin probes monitor different environments in the membranes and phospholipid vesicles prepared from them.     

Two amides from Piper amalago

The hexane extracts of the roots of Piper amalago afforded two trans-cinnamoylamides, 2-methoxy-4,5-methylenedioxy-trans-cinnamoyl piperidide and pyrrolidide.     

Novel amide alkaloids from the roots of Piper guineense

Two novel amide alkaloids, wisanine and wisanidine, have been isolated from the petroleum-extract of the roots of Piper guineense, and found to be N-piperidyl-5 (2-methoxy-4,5-methylenedioxyphenyl)-trans-2-trans-4-pentadienamide and N-pyrrolidyl-5-(2-methoxy-4, 5-methylenedioxyphenyl)-trans-2-trans-4-pentadienamide respectively. The structure of wisanidine has been confirmed by synthesis. N-Isobutyl)-trans-2-trans-4-eicosadienamide, recently reported to be present in the fruits of the plant as well as Piperine and Δ^α,β-dihydropiperine have also been found to be major constituents of the roots.     

Synthesis, characterization, spectroscopic and electrochemical properties of trans,trans,trans-bis(triphenyl phosphine) bis(aroyl hydrazonato)ruthenium(II) complexes

Four ruthenium (II) complexes of general formula Ru(PPh₃)₂(L)₂ have been synthesized and characterized. The spectroscopic and cyclic voltammetric studies of these complexes are also reported. X-ray crystal structure determination of two of the complexes reveal that Ru(II) occupies trans,trans,trans-(t,t,t) N₂O₂P₂ centrosymmetric octahedral environments, with the ligand pair occupying the equatorial plane. ³¹P NMR confirms the presence of two trans-PPh₃ groups in all the complexes. The transformation of the complexes in dichloromethane solution is studied by spectrophotometry and ³¹P NMR spectroscopy.     

Isotachin A and isotachin B,two sulphur-containing acrylates from the liverwort isotachis japonica

Isotachin A and isotachin B, two new sulphur-containing acrylates, were isolated from the liverwort Isotachis japonica. Their structures were established to be benzyl trans-β-methylthioacrylate and β-phenylethyl trans-β-methylthioacrylate by chemical and spectral methods. This is the first report of sulphur-containing substances from bryophytes. Some previously known benzoates and cinnamates as well as 2-methoxy-4-hydroxyphenyl 1β-glucoside and stigmasteryl 3β-glucoside were also isolated.     

In Vivo Performance and Properties of Tamoxifen Metabolites for CreERT2 Control

Mutant Estrogen Receptor (ERT2) ligand-binding domain fusions with Cre recombinase are a key tool for spatio-temporally controlled genetic recombination with the Cre/lox system. CreERT2 is efficiently activated in a concentration-dependent manner by the Tamoxifen metabolite trans-4-OH-Tamoxifen (trans-4-OHT). Reproducible and efficient Cre/lox experimentation is hindered by the gradual loss of CreERT2 induction potency upon prolonged storage of dissolved trans-4-OHT, which potentially results from gradual trans-to-cis isomerization or degradation. Here, we combined zebrafish CreERT2 recombination experiments and cell culture assays to document the gradual activity loss of trans-4-OHT and describe the alternative Tamoxifen metabolite Endoxifen as more stable alternative compound. Endoxifen retains potent activation upon prolonged storage (3 months), yet consistently induces half the ERT2 domain fusion activity compared to fresh trans-4-OHT. Using ¹H-NMR analysis, we reveal that trans-4-OHT isomerization is undetectable upon prolonged storage in either DMSO or Ethanol, ruling out isomer transformation as cause for the gradual loss of trans-4-OHT activity. We further establish that both trans-4-OHT and Endoxifen are insensitive to light exposure under regular laboratory handling conditions. We attribute the gradual loss of trans-4-OHT potency to precipitation over time, and show that heating of aged trans-4-OHT aliquots reinstates their CreERT2 induction potential. Our data establish Endoxifen as potent and reproducible complementary compound to 4-OHT to control ERT2 domain fusion proteins in vivo, and provide a framework for efficient chemically controlled recombination experiments.     

Palladium and rhodium complexes of a chiral pincer ligand derived from 1,3-trans disubstituted cyclohexane

Reactions of cis- and trans-1,3-bis(di-t-butylphosphinomethyl)cyclohexane (cis- and trans-PCyP), with rhodium and palladium chlorides afforded C_s and C₁ symmetrical pincer complexes, RhHCl(cis-PCyP), RhHCl(trans-PCyP), [(COD)Rh(μ-Cl)₂RhH(trans-PCyP)], PdCl(cis-PCyP), and PdCl(trans-PCyP), where the PCyP ligands are coordinated in a meridianal fashion through the two phosphorus atoms and the cyclometalated C-1 carbon of the cyclohexane ring. The rhodium complexes were structurally characterized by X-ray diffraction. Isomers of the RhHCl(PCyP) and PdCl(PCyP) complexes were studied by DFT calculations.