Should dithiophosphinate esters function as RAFT agents?

[graph: see text] High-level ab initio calculations indicate that *CH3 addition to the sulfur center of S=P(Z)(Z')SCH3 (Z,Z' = CH3, CN, OCH3, Ph) is considerably less exothermic than addition to the corresponding RAFT agents, S=C(Z)SCH3. This suggests that dithiophosphinate esters may have only limited use in controlling free-radical polymerization, but should make excellent radical chain carriers in organic synthesis. The results cast doubt on the notion that phosphoranyl radicals are more "intrinsically" stabilized than carbon-centered radicals.     

Synthesis of New Brassinosteroid 24-Norcholane Type Analogs Conjugated in C-3 with Benzoate Groups

The metabolism of brassinosteroid leads to structural modifications in the ring skeleton or the side alkyl chain. The esterification and glycosylation at C-3 are the most common metabolic pathways, and it has been suggested that conjugate brassinosteroids are less active or inactive. In this way, plants regulate the content of active brassinosteroids. In this work, the synthesis of brassinosteroid 24-norcholane type analogs conjugated at C-3 with benzoate groups, carrying electron donor and electron attractant substituents on the aromatic ring, is described. Additionally, their growth-promoting activities were evaluated using the Rice Lamina Inclination Test (RLIT) and compared with that exhibited by brassinolide (used as positive control) and non-conjugated analogs. The results indicate that at the lowest tested concentrations (10⁻⁸–10⁻⁷ M), all analogs conjugated at C-3 exhibit similar or higher activities than brassinolide, and the diasteroisomers with S configuration at C-22 are the more active ones. Increasing concentration (10⁻⁶ M) reduces the biological activities of analogs as compared to brassinolide.     

Evaluation of molten inorganic salt hydrates as reaction medium for the derivatization of cellulose

Molten inorganic salt hydrates are highly efficient solvents forcellulose. The carboxymethylation of the polymer dissolved in this new group ofcellulose solvents was investigated. The homogeneous carboxymethylation ofcellulose in molten LiClO₄3H₂O using sodiummonochloroacetate in the presence of NaOH is possible. The formation of CMC wasconfirmed by FT- Raman spectroscopy. Structure analysis by means of HPLC afterchain degradation showed the formation of CMC with a DS of 2 after a shortreaction time of 4 h. The derivatives exhibit a statisticaldistribution of substituents along the polymer chain if prepared in moltenLiClO₄3H₂O as solvent. A substituent distributioninthe order C-6 > C-2 C-3 for anhydroglucose units (AGU) was concludedfrom ¹H-NMR measurements. The synthesis of CMC in the swellingmediumLiClxH₂O (2 x 5) yields polymers with astatistical distribution of functional groups along the chain. The watercontentof the salt melts has a dramatic influence on the DS_CMC.     

TiO2 phytate films as hosts and conduits for cytochrome c electrochemistry

Cytochrome c is accumulated into a film of TiO(2) nanoparticles and phytate by adsorption from an aqueous solution into the mesoporous structure. Stable voltammetric responses and high concentrations of redox protein within the TiO(2) phytate layer can be achieved. Two types of electrode systems are reported with (i) the modified TiO(2) phytate film between electrode and aqueous solution phase and (ii) the modified TiO(2) phytate film buried under a porous gold electrode ('porotrode'). The electrical conductivity of TiO(2) phytate films is measured and compared in the dry and in the wet state. Although in the dry state essentially insulating, the TiO(2) phytate film turns into an electrical conductor (with approximately 4 Omega cm specific resistivity assuming ohmic behaviour) when immersed in aqueous 0.1 M phosphate buffer solution at pH 7. The redox protein cytochrome c is therefore directly connected to the electrode via diffusion and migration of electrons in the three dimensional mesoporous TiO(2) phytate host structure. Electron transfer from cytochrome c to TiO(2) is proposed to be the rate-determining step for this conduction mechanism.     

Antiphytopathogenic activity of Psoralea glandulosa (Fabaceae) against Botrytis cinerea and Phytophthora cinnamomi

The resinous exudate, three meroterpenes, namely bakuchiol (1), 3-hydroxybakuchiol (2), 12-hydroxyisobakuchiol (3), and one furanocoumarin, psoralen (4), were isolated from the leaves of culen (Psoralea glandulosa). In addition to these, two semi-synthetic derivatives, bakuchiol acetate (5) and bakuchiol methyl eter (6), were obtained from 1, and were subsequently evaluated in vitro for the inhibitory effect of resin and compounds on the mycelial growth of Botrytis cinerea Pers.: Fr. and Phytophthora cinnamomi Rands. The resinous exudate inhibited the mycelial growth of both the pathogens, while bakuchiol (1) exhibited an inhibitory effect on the mycelial growth of B. cinerea up to 94% at a concentration of 150 mg/L and psoralen (4) reduced the mycelial growth of P. cinnamomi up to 80% at a concentration of 150 mg/L. These compounds have the ability of blocking the development of mycelial growth and may be used as a potential biopesticide in the agricultural sector once the in vivo test results have been validated.     

Expanding Lipidome Coverage Using LC-MS/MS Data-Dependent Acquisition with Automated Exclusion List Generation

Untargeted omics analyses aim to comprehensively characterize biomolecules within a biological system. Changes in the presence or quantity of these biomolecules can indicate important biological perturbations, such as those caused by disease. With current technological advancements, the entire genome can now be sequenced; however, in the burgeoning fields of lipidomics, only a subset of lipids can be identified. The recent emergence of high resolution tandem mass spectrometry (HR-MS/MS), in combination with ultra-high performance liquid chromatography, has resulted in an increased coverage of the lipidome. Nevertheless, identifications from MS/MS are generally limited by the number of precursors that can be selected for fragmentation during chromatographic elution. Therefore, we developed the software IE-Omics to automate iterative exclusion (IE), where selected precursors using data-dependent topN analyses are excluded in sequential injections. In each sequential injection, unique precursors are fragmented until HR-MS/MS spectra of all ions above a user-defined intensity threshold are acquired. IE-Omics was applied to lipidomic analyses in Red Cross plasma and substantia nigra tissue. Coverage of the lipidome was drastically improved using IE. When applying IE-Omics to Red Cross plasma and substantia nigra lipid extracts in positive ion mode, 69% and 40% more molecular identifications were obtained, respectively. In addition, applying IE-Omics to a lipidomics workflow increased the coverage of trace species, including odd-chained and short-chained diacylglycerides and oxidized lipid species. By increasing the coverage of the lipidome, applying IE to a lipidomics workflow increases the probability of finding biomarkers and provides additional information for determining etiology of disease.

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Application of ionic liquids to the electrodeposition of metals

The electrodeposition of most of technologically important metals has been shown to be possible from a wide range of room temperature molten salts, more commonly known today as 'ionic liquids'. These liquids are currently under intense scrutiny for a wide variety of applications some of which have already been commercialized. Despite the fact that electrodeposition was the first application studied in these liquids no metal deposition processes have as yet been developed to an industrial scale. This review addresses the practical and theoretical aspects that need to be considered when choosing ionic liquids for metal deposition. It details the current understanding of the physical and chemical properties of these interesting fluids and highlights the areas that need to be considered to develop practical electroplating systems. The effect of composition and temperature on viscosity and conductivity are discussed together with the fundamental approaches required to synthesise new liquids.     

Azetidine‐Containing Alkaloids Produced by a Quorum‐Sensing Regulated Nonribosomal Peptide Synthetase Pathway in Pseudomonas aeruginosa

Pseudomonas aeruginosa displays an impressive metabolic versatility, which ensures its survival in diverse environments. Reported herein is the identification of rare azetidine‐containing alkaloids from P. aeruginosa PAO1, termed azetidomonamides, which are derived from a conserved, quorum‐sensing regulated nonribosomal peptide synthetase (NRPS) pathway. Biosynthesis of the azetidine motif has been elucidated by gene inactivation, feeding experiments, and biochemical characterization in vitro, which involves a new S‐adenosylmethionine‐dependent enzyme to produce azetidine 2‐carboxylic acid as an unusual building block of NRPS. The mutants of P. aeruginosa unable to produce azetidomonamides had an advantage in growth at high cell density in vitro and displayed rapid virulence in Galleria mellonella model, inferring functional roles of azetidomonamides in the host adaptation. This work opens the avenue to study the biological functions of azetidomonamides and related compounds in pathogenic and environmental bacteria.     

A computational foray into the mechanism and catalysis of the adduct formation reaction of guanine with crotonaldehyde

Crotonaldehyde, a common environmental pollutant and product of endogenous lipid peroxidation, reacts with guanine to form DNA adducts with pronounced genotoxicity and mutagenicity. Here, we explore the molecular mechanism of this adduct formation using double-hybrid density functional theory methods. The reaction can be envisaged to occur in a two-step fashion via an aza-Michael addition leading to an intermediate ring-open adduct followed by a cyclization reaction giving the mutagenic ring-closed adduct. We find that (i) a 1,2-type addition is favored over a 1,4-type addition for the aza-Michael addition, and (ii) an initial tautomerization of the guanine moiety in the resulting ring-open adduct significantly reduces the barrier toward cyclization compared to the direct cyclization of the ring-open adduct in its keto-form. Overall, the aza-Michael addition is found to be rate-determining. We further find that participation of a catalytic water molecule significantly reduces the energy barriers of both the addition and cyclization reaction. © 2018 Wiley Periodicals, Inc.