Ethylene influences green plant regeneration from barley callus

The plant hormone ethylene is involved in numerous plant processes including in vitro growth and regeneration. Manipulating ethylene in vitro may be useful for increasing plant regeneration from cultured cells. As part of ongoing efforts to improve plant regeneration from barley (Hordeum vulgare L.), we investigated ethylene emanation using our improved system and investigated methods of manipulating ethylene to increase regeneration. In vitro assays of regeneration from six cultivars, involving 10 weeks of callus initiation and proliferation followed by 8 weeks of plant regeneration, showed a correlation between regeneration and ethylene production: ethylene production was highest from ‘Golden Promise’, the best regenerator, and lowest from ‘Morex’ and ‘DH-20’, the poorest regenerators. Increasing ethylene production by addition of 1-aminocyclopropane 1-carboxylic acid (ACC) during weeks 8–10 increased regeneration from Morex. In contrast, adding ACC to Golden Promise cultures during any of the tissue culture steps reduced regeneration, suggesting that Golden Promise may produce more ethylene than needed for maximum regeneration rates. Blocking ethylene action with silver nitrate during weeks 5–10 almost doubled the regeneration from Morex and increased the Golden Promise regeneration 1.5-fold. Silver nitrate treatment of Golden Promise cultures during weeks 8–14 more than doubled the green plant regeneration. These results indicate that differential ethylene production is related to regeneration in the improved barley tissue culture system. Specific manipulations of ethylene were identified that can be used to increase the green plant regeneration from barley cultivars. The timing of ethylene action appears to be critical for maximum regeneration.     

Polyacrylamide lamination enables mass spectrometry compatible staining and in-gel digestion of proteins separated by agarose IEF

Agarose IEF enables the separation of large proteins and protein complexes. A complication of agarose gels attached onto polyester support is the lack of sensitive protein staining methods compatible with protein analysis and identification protocols. In this study, agarose IEF gels were used to separate the proteins, followed by layering the agarose with polyacrylamide. The formed laminate gels were seamless and durable and they were readily detached from the polyester. The gels were amenable to MS compatible staining. The sensitivity obtained with the acidic silver staining method was 20-50 ng/band of myoglobin. Laminated agarose was a suitable matrix for in-gel digestion based generation of tryptic peptides for MALDI-MS.     

Plasmonic Properties of Silver Nanoparticles on Two Substrates

In this paper, we examine the plasmonic properties of silver nanoparticles, with an emphasis on the sensitivity of the extinction spectra on the supporting substrate: silica (SiO₂) microsphere and indium tin oxide (ITO) coated glass slide, on which silver particles are deposited electroless and electrochemically, respectively. The microstructures and phases of these nanoparticles are characterized by transmission electron microscopy, field emission electron microscopy and X-ray diffraction analysis. The surface plasmon resonance (SPR) properties which are experimentally measured in the ultraviolet-visible-near infrared spectral region are compared to electrodynamics calculations based on the discrete dipole approximation. A wide SPR band ranging from 400 to 800 nm is observed for the silver nanoparticles on a silica microsphere, which is similar to the plasmon resonance characteristics of metal nanoshells. The SPR of a conducting substrate, however, has an effect on the plasmonic properties of silver nanoparticles at longer wavelength.      

Coordination polymers of 1,8-bis(2-methylthioethoxy)anthraquinone and 1,5-bis(2-methylthioethoxy)anthraquinone with Ag(I): Synthesis and X-ray crystallography

The reaction of 2-(methylthioethanol) with 1,8-dichloroanthraquinone and 1,5-dichloroanthraquinone in THF with base produces 1,8-bis(2-methylthioethoxy)anthraquinone (1) and 1,5-bis(2-methylthioethoxy)anthraquinone (2), respectively. Silver(I) complexes of 1 and 2 have been synthesized after combination with [Ag(CH₃CN)₄]BF₄ in 1:1 M ratio to yield, [(1,8-bis(2-methylthioethoxy)anthraquinone)Ag]BF₄, (3) and [(1,5-bis(2-methylthioethoxy)anthraquinone)Ag·CH₃CN]BF₄, (4). X-ray crystal structures of the free ligand (1) and the Ag(I) complexes (3 and 4) are reported. The intraannular carbonyl group forms a coordinate-covalent bond with Ag(I) and, in the solid state, both silver(I) complexes are found as coordination polymers.     

Syntheses, structures and bioactivities of silver(I) complexes with dithioether ligands that contain a di- or triethylene glycol chain and different terminal groups

A series of flexible dithioethyl ligands that contain ethyleneoxy segments were designed and synthesized, including bis(2-(pyridin-2-ylthio)ethyl)ether (L¹), 1,2-bis(2-(pyridin-2-ylthio)ethoxy)ethane (L²), bis(2-(benzothiazol-2-ylthio)ethyl)ether (L³) and 1,2-bis(2-(benzothiazol-2-ylthio)ethoxy)ethane (L⁴). Reactions of these ligands with AgNO₃ led to the formation of four new supramolecular coordination complexes, [Ag₂L¹(NO₃)₂]₂ (1), [Ag₂L²(NO₃)₂] (2), [AgL³(NO₃)]_∞ (3) and [AgL⁴(NO₃)] (4) in which the length of the (CH₂CH₂O)_n spacers and the terminal groups of ligands cause subtle geometrical differences. Studies of the inhibitory effect to the growth of Phaeodactylum tricornutum show that all four complexes are active and the compound 4 has the highest inhibitory activity.     

Synthesis, structural characterization and biological studies of novel mixed ligand Ag(I) complexes with triphenylphosphine and aspirin or salicylic acid

Two new mixed ligand silver(I) complexes of formulae {[Ag(tpp)₃(asp)](dmf)} (1) (aspH = o-acetylsalicylic acid and tpp = triphenylphosphine) and [Ag(tpp)₂(o-Hbza)] (2) (o-HbzaH = o-hydroxy-benzoic acid) were synthesized and characterized by elemental analyses, spectroscopic techniques and X-ray crystallography at ambient conditions. Three phosphorus and one carboxylic oxygen atoms from a de-protonated aspirin ligand in complex 1 and two phosphorus and two carboxylic oxygen atoms from a chelating o-Hbza anion in complex 2 form a tetrahedral geometry around Ag(I) ions in both complexes.Complexes 1 and 2 and the silver(I) nitrate, tpp, aspNa and o-HbzaH were tested for their in vitro cytotoxic activity against leiomyosarcoma cells (LMS), human breast adenocarcinoma cells (MCF-7) and normal human fetal lung fibroblasts (MRC-5) cells with Thiazolyl Blue Tetrazolium Bromide (MTT) assay. For both cell lines 1 and 2 were found to be more active than cisplatin. Additionally, 1 and 2 exhibit lower activity on cell growth proliferation of MRC-5 cells. The type of LMS cell death caused by 1 and 2 were evaluated in vitro by use of flow cytometry assay. The results show that at concentrations of 1.5 and 1.9 μΜ of complex 1, 44.1% and 69.4%, respectively of LMS cells undergo programmed cell death (apoptosis). When LMS cells were treated with 1.6 and 2.3 μM of 2, LMS cells death was by 29.6% and 81.3%, respectively apoptotic. Finally, the influence of the complexes 1 and 2, upon the catalytic peroxidation of linoleic acid to hydroperoxylinoleic acid by the enzyme lipoxygenase (LOX) was kinetically and theoretically studied. The binding of 1 and 2 towards LOX was also investigated by Saturation Transfer Difference (STD) ¹H NMR experiments.     

N-Heterocyclic carbene gold(I) and silver(I) adducts of [Pt2(μ-S)2(PPh3)4]

Reaction of the metalloligand [Pt₂(μ-S)₂(PPh₃)₄] with the N-heterocyclic carbene (NHC) complexes IPrAuCl, IMesAuCl and IMesAgCl in methanol gave the first examples of metal adducts of [Pt₂(μ-S)₂(PPh₃)₄] that contain NHC ligands, namely [Pt₂(μ-S)₂(PPh₃)₄AuL]⁺ (L = IPr, IMes) and [Pt₂(μ-S)₂(PPh₃)₄AgIMes]⁺. The complexes were isolated as hexafluorophosphate salts. Reaction of [Pt₂(μ-S)₂(PPh₃)₄] with excess IPrAuCl in refluxing methanol yielded only the mono-adduct, in contrast to the behaviour with the gold(I) phosphine complex Ph₃PAuCl, which undergoes double addition giving [Pt₂(μ-SAuPPh₃)₂(PPh₃)₄]²⁺. The X-ray structure of [Pt₂(μ-S)₂(PPh₃)₄AuIPr]PF₆ was determined and reveals that the ‘free’ sulfide is substantially sterically protected by the IPr ligand, accounting for the low reactivity towards addition of a second AgIPr⁺ moiety.     

Assembly of 1D, 2D and 3D silver(I) coordination polymers with nitrilotriacetate and 2-aminopyrimidyl mixed ligands

Three mixed ligands coordination polymers (CPs) [Ag_1.5(apym)(nta)_0.5]_n (1), [(NH₄)Ag₂(mapym)(nta)·(H₂O)₃]_n (2), [Ag₂(dmapym)₃(Hnta)]_n (3) (apym = 2-aminopyrimidine, mapym = 4-methyl-2-aminopyrimidine, dmapym = 4, 6-dimethyl-2-aminopyrimidine, H₃nta = nitrilotriacetate) were synthesized and characterized. For 1-3, as the substituents change from H to one methyl and two methyl groups, the dimensionalities of 1-3 decrease from three-dimension (3D) to one-dimension (1D) due to the steric effect of methyl groups. For 1, the μ₂-apym ligands link the Ag(I) ions to form a 1D double-chain incorporating ligand unsupported Ag···Ag interaction. The nta³⁻ ligands extend the 1D double-chain into a 3D framework. In 2, one heptadentate nta³⁻ ligand binds four Ag(I) ions and incorporates μ₂-mapym ligand to link metal centers to form a 2D sheet which can be simplified to be a 10³ net. Complex 3 features a 1D chain structure incorporating Hnta²⁻ and monodentate dmapym ligands. The substituents on the pyrimidyl ring intensively influence the coordination environments of metal ion and the coordination modes of the carboxyl group, and thus determine the structures of the CPs. The photoluminescent properties of 1-3 were also investigated.     

New metal complexes with 5-(1H-imidazol-4-ylmethyl)aminoisophthalic acid: Syntheses, structures, electrochemistry and electrocatalysis

Three new coordination polymers {[Cu(HL)(H₂O)]·H₂O}_n (1), [Ag(H₂L)]_n (2), and {[Co(HL)(phen)(H₂O)]·8H₂O}_n (3) [H₃L = 5-(1H-imidazol-4-ylmethyl)aminoisophthalic acid, phen = 1,10-phenanthroline] have been synthesized under hydrothermal conditions. The results of X-ray diffraction analysis revealed that complex 1 displays (3, 3)-connected 2D network with (4, 8²) topology, while complexes 2 and 3 have infinite 1D chain structure, in which one of the two carboxylic groups of H₂L⁻/HL²⁻ is uncoordinated. The 2D layers of 1 or the 1D chains of 2 and 3 are further linked together by hydrogen bonds and π-π interactions to form 3D supramolecular frameworks. Moreover, the electrochemical properties of complexes 1 and 2 have been studied by modified glassy carbon electrodes of 1 (Cu-GCE) and 2 (Ag-GCE), and the results indicate that the Cu-GCE and Ag-GCE show one-electron redox peaks. In addition, both Cu-GCE and Ag-GCE have good electrocatalytic activities toward the reduction of H₂O₂ in phosphate buffer (pH 5.5) solution.     

Tetrameric 1:1 and monomeric 1:3 complexes of silver(I) halides with tri(p-tolyl)-phosphine: A structural and biological study

Silver(I) halides react with tri(p-tolyl)phosphine (tptp, C₂₁H₂₁P) in MeOH/MeCN solutions in 1:1 or 1:3 molar ratios to give complexes of formulae {[AgCl(tptp)]₄} (1) or [AgX(tptp)₃] (X = Cl (2), Br (3), I (4)), respectively. The complexes were characterized by elemental analyses, and FT-IR far-IR, FT-Raman, TG and ¹H, ¹³C, ³¹P NMR spectroscopic techniques. Crystal structures of complexes 2-4 were determined by X-ray diffraction at room temperature (rt). The crystal structure of 1 and 4 was also determined at 100(1) and 140(2) K (lt), respectively. In complex 1 four μ3-Cl ions are bonded with four Ag(I) ions forming a cubane while the coordination sphere of silver(I) ions is completed by one P atom from a terminal tri(p-tolyl)phosphine ligand. In complexes 2-3 one terminal halogen and three P atoms from phosphine ligands form a tetrahedral arrangement around the metal ion. Complexes 1-4 were tested for in vitro cytostatic activity against sarcoma cancer cells (mesenchymal tissue) from the Wistar rat, polycyclic aromatic hydrocarbons (PAH, benzo[a]pyrene) carcinogenesis and against murine leukemia (L1210) and human T-lymphocyte (Molt4/C8 and CEM) cells. The silver(I) complexes 1-4 show strong activity.