Step-economic and cost effective synthesis of coumarin based blue emitting fluorescent dyes

Cost effective and green protocols for the synthesis of two new series of coumarin based blue light emitting fluorophores named as ‘Beta Fluors’ and ‘Alpha Fluors’ are described. The coumarin alkylamide based Beta Fluors are developed using a one-step multi-component process in the presence of phenyl boronic acid as an efficient green catalyst. The Alpha Fluors are structured with coumarin–triazole–carboxamide peptidomimetics and their synthesis involves the ‘click with MCR’ concept. The new fluorophores gave high Stoke’s shift values for the emission wavelengths and their structural features are promising for further fine tuning to obtain preferred emission maxima.     

Arsenic in marine tissues — The challenging problems to electrothermal and hydride generation atomic absorption spectrometry

Analytical problems in determination of arsenic in marine tissues are addressed. Procedures for the determination of total As in solubilized or extracted tissues with tetramethylammonium hydroxide and methanol have been elaborated. Several typical lyophilized tissues were used: NIST SRM 1566a ‘Oyster Tissue’, BCR-60 CRM ‘Trace Elements in an Aquatic Plant (Lagarosiphon major)’, BCR-627 ‘Forms of As in Tuna Fish Tissue’, IAEA-140/TM ‘Sea Plant Homogenate’, NRCC DOLT-1 ‘Dogfish Liver’ and two representatives of the Black Sea biota, Mediterranean mussel (Mytilus galloprovincialis) and Brown algae (Cystoseira barbata). Tissues (nominal 0.3 g) were extracted in tetramethylammonium hydroxide (TMAH) 1 ml of 25% m/v TMAH and 2 ml of water) or 5 ml of aqueous 80% v/v methanol (MeOH) in closed vessels in a microwave oven at 50 °C for 30 min. Arsenic in solubilized or extracted tissues was determined by electrothermal atomic absorption spectrometry (ETAAS) after appropriate dilution (nominally to 25 ml, with further dilution as required) under optimal instrumental parameters (pyrolysis temperature 900 °C and atomization temperature 2100 °C) with 1.5 μg Pd as modifier on Zr–Ir treated platform. Platforms have been pre-treated with 2.7 μmol of zirconium and then with 0.10 μmol of iridium which served as a permanent chemical modifier in direct ETAAS measurements and as an efficient hydride sequestration medium in flow injection hydride generation (FI-HG)–ETAAS. TMAH and methanol extract 96–108% and 51–100% of As from CRMs. Various calibration approaches have been considered and critically evaluated. The effect of species-dependent slope of calibration graph or standard additions plot for total As determination in a sample comprising of several individual As species with different ETAAS behavior has been considered as a kind of ‘intrinsic element speciation interference’ that cannot be completely overcome by standard additions technique. Calibration by means of CRMs has given only semi-quantitative results. The limits of detection (3σ) were in the range 0.5–1.2 mg kg^− 1 As dry weight (wt.) for direct ETAAS analysis of extracts in both TMAH and MeOH. Within-run precision (RSD%) was 5–15% and 7–20% for TMAH and MeOH extracts at As levels 4–50 mg kg^− 1 dry wt., respectively.     

Total synthesis of novel bioactive natural product paracaseolide A and analogues: computational evaluation of a ‘proposed’ biomimetic Diels–Alder reaction

A short and generally applicable synthesis of bioactive tetracyclic natural product paracaseolide A has been accomplished employing a ‘proposed’ biomimetic Diels–Alder reaction as the key strategic step. The Diels–Alder precursors for this purpose were readily assembled through a versatile Suzuki coupling on preformed α-halo butenolides. The mechanistic aspects of the ‘putative’ biomimetic Diels–Alder reaction have been probed using computational methods, which suggest that this [4+2]-cycloaddition proceeds through a step-wise process and product profile is thermodynamically governed.     

New reactivity of hydroxyallylpyridyl derivatives as C-3 carbon nucleophiles

Hydroxyallylpyridyl derivatives exhibited a peculiar thermal behavior likely ascribed to the weak acidity of the ‘picoline-type’ hydrogen atom on the C-1 carbon of the allyl residue, leading to allyl inversion products. The unprotected alcohol reacted as ‘vinylogous picoline’ carbon nucleophile with strongly activated heterocyclic counterparts. A mechanistic rationale for this unprecedented reactivity was proposed.     

Synthesis of cyclic peptides via O-N-acyl migration

We describe here a novel and convenient synthesis of head-to-tail cyclic peptide avoiding racemization. Linear depsipeptides including a serine residue as the key element for ester bond formation and acyl transfer were synthesized on 2-chlorotrityl chloride resin. After cleavage from the resin, intramolecular head-to-tail cyclization was performed in solution by C-terminal activation of urethane protected O-acyl serine residue. After removal of the N^α-serine protecting group, the final step consisted in O-N-acyl migration reaction on the ‘switch’ or ‘click’ element to restore native cyclic peptides.     

Acceleration of Cu(I)-mediated Huisgen 1,3-dipolar cycloaddition by histidine derivatives

Acceleration of Cu(I)-mediated Huisgen 1,3-dipolar cycloaddition (Sharpless ‘click reaction’) by non-basic histidine derivatives was found. An efficient ‘self-activating’ click reaction between the azide- and acetylene-containing peptides on the solid-phase has also been achieved by introducing the N^im-benzylhistidine residue on the reacting peptides.     

Fully automated immunoassay for detection of prostate-specific antigen using nano-magnetic beads and micro-polystyrene bead composites, 'Beads on Beads'

Magnetic beads have served as a conventional bioassay platform in biotechnology. In this study, a fully automated immunoassay was performed using novel nano- and microbead-composites constructed by assembling nano-magnetic beads onto polystyrene microbeads, designated ‘Beads on Beads’. Nano-sized bacterial magnetic particles (BacMPs) displaying the immunoglobulin G (IgG)-binding domain of protein A (ZZ domain) were used for the construction of ‘Beads on Beads’ via the interaction of biotin-streptavidin. The efficient assembly of ‘Beads on Beads’ was performed by gradual addition of biotin-labeled BacMPs onto streptavidin-coated polystyrene microbeads. Approximately 2000 BacMPs were uniformly assembled on a single microbead without aggregation. The constructed ‘Beads on Beads’ were magnetized and separated from the suspension by using an automated magnetic separation system with a higher efficiency than BacMPs alone. Furthermore, fully automated detection of prostate-specific antigens was performed with the detection limit of 1.48 ng mL⁻¹. From this preliminary assay, it can be seen that ‘Beads on Beads’ could be a powerful tool in the development of high-throughput, fully automated multiplexed bioassays.     

Pre-analytical method for NMR-based grape metabolic fingerprinting and chemometrics

Although metabolomics aims at profiling all the metabolites in organisms, data quality is quite dependent on the pre-analytical methods employed. In order to evaluate current methods, different pre-analytical methods were compared and used for the metabolic profiling of grapevine as a model plant. Five grape cultivars from Portugal in combination with chemometrics were analyzed in this study. A common extraction method with deuterated water and methanol was found effective in the case of amino acids, organic acids, and sugars. For secondary metabolites like phenolics, solid phase extraction with C-18 cartridges showed good results. Principal component analysis, in combination with NMR spectroscopy, was applied and showed clear distinction among the cultivars. Primary metabolites such as choline, sucrose, and leucine were found discriminating for ‘Alvarinho’, while elevated levels of alanine, valine, and acetate were found in ‘Arinto’ (white varieties). Among the red cultivars, higher signals for citrate and GABA in ‘Touriga Nacional’, succinate and fumarate in ‘Aragonês’, and malate, ascorbate, fructose and glucose in ‘Trincadeira’, were observed. Based on the phenolic profile, ‘Arinto’ was found with higher levels of phenolics as compared to ‘Alvarinho’. ‘Trincadeira’ showed lowest phenolics content while higher levels of flavonoids and phenylpropanoids were found in ‘Aragonês’ and ‘Touriga Nacional’, respectively. It is shown that the metabolite composition of the extract is highly affected by the extraction procedure and this consideration has to be taken in account for metabolomics studies.     

‘O-Acyl isopeptide method’: racemization-free segment condensation in solid phase peptide synthesis

We disclosed a novel ‘racemization-free segment condensation’ based on the ‘O-acyl isopeptide method’ in which an N-segment including C-terminal O-acyl isopeptide structure with urethane-protected Ser/Thr residue was employed for the segment condensation, suggesting that the use of this method contributes to the effective convergent synthesis of long peptides/proteins.     

Surface modification of chromatography adsorbents by low temperature low pressure plasma

In this study we show how low temperature glow discharge plasma can be used to prepare bi-layered chromatography adsorbents with non-adsorptive exteriors. The commercial strong anion exchange expanded bed chromatography matrix, Q HyperZ, was treated with plasmas in one of two general ways. Using a purpose-designed rotating reactor, plasmas were employed to either: (i) remove anion exchange ligands at or close to the exterior surface of Q HyperZ, and replace them with polar oxygen containing functions (‘plasma etching and oxidation’); or (ii) bury the same surface exposed ligands beneath thin polymer coatings (‘plasma polymerization coating’) using appropriate monomers (vinyl acetate, vinyl pyrrolidone, safrole) and argon as the carrier gas. X-ray photoelectron spectroscopy analysis (first ∼10 nm depth) of Q HyperZ before and after the various plasma treatments confirmed that substantial changes to the elemental composition of Q HyperZ's exterior had been inflicted in all cases. The atomic percent changes in carbon, nitrogen, oxygen, yttrium and zirconium observed after being exposed to air plasma etching were entirely consistent with: the removal of pendant Q (trimethylammonium) functions; increased exposure of the underlying yttrium-stabilised zirconia shell; and introduction of hydroxyl and carbonyl functions. Following plasma polymerization treatments (with all three monomers tested), the increased atomic percent levels of carbon and parallel drops in nitrogen, yttrium and zirconium provided clear evidence that thin polymer coats had been created at the exteriors of Q HyperZ adsorbent particles. No changes in adsorbent size and surface morphology, nor any evidence of plasma-induced damage could be discerned from scanning electron micrographs, light micrographs and measurements of particle size distributions following 3 h exposure to air (220 V; 35.8 W L⁻¹) or ‘vinyl acetate/argon’ (170 V; 16.5 W L⁻¹) plasmas. Losses in bulk chloride exchange capacity before and after exposure to plasmas enabled effective modification depths within hydrated Q HyperZ adsorbent particles to be calculated as 0.2–1.2 μm, depending on the conditions applied. The depth of plasma induced alteration was strongly influenced by the power input and size of the treated batch, i.e. dropping the power or increasing the batch size resulted in reduced plasma penetration and therefore shallower modification. The selectivity of ‘surface vs. core’ modification imparted to Q HyperZ by the various plasma treatments was evaluated in static and dynamic binding studies employing appropriate probes, i.e. plasmid DNA, sonicated calf thymus DNA and bovine serum albumin. In static binding studies performed with adsorbents that had been exposed to plasmas at the 5 g scale (25 g L⁻¹ of plasma reactor), the highest ‘surface/core’ modification selectivity was observed for Q HyperZ that had been subjected to 3 h of air plasma etching at 220 V (35.8 W L⁻¹). This treatment removed ∼53% of ‘surface’ DNA binding at the expense of a 9.3% loss in ‘core’ protein binding. Even more impressive results were obtained in dynamic expanded bed adsorption studies conducted with Q HyperZ adsorbents that had been treated with air (220 V, 3 h) and ‘vinyl acetate/argon’ (170 V, 3 h) plasmas at 10.5 g scale (52.5 g L⁻¹ of plasma reactor). Following both plasma treatments: the 10% breakthrough capacities of the modified Q HyperZ adsorbents towards ‘surface’ binding DNA probes dropped very significantly (30–85%); the DNA induced inter-particle cross-linking and contraction of expanded beds observed during application of sonicated DNA on native Q HyperZ was completely eradicated; but the ‘core’ protein binding performance remained unchanged cf. that of the native Q HyperZ starting material.     

Microsheets assembled from pyridinium-tailored anthracenes

A facile strategy to construct microsheets assembled from 9-substituted anthracene-pyridinium compounds (APs) has been developed. With the different length of linkers, APs could form the ‘v’-shaped dimer or ‘face-to-face’ dimer, respectively, driven by CH–π interactions and π-stacking interactions, which consequently lead to the assembly of final microsheets.     

On the optical rotation of 1 (or 3)-stearoyl-sn-glycerol

Small specific rotation is one of the setbacks in the studies of 1 (or 3)-acyl-sn-glycerols, which makes assessment of the optical purity/establishment of the identity of new compounds difficult. Some unusually large data reported for 3-stearoyl-sn-glycerol in the literature suggested that use of low sample concentrations in recording optical rotations might alleviate the long-existing (though probably ‘hidden’ to those, who are not working in this area) problem. To verify the astonishing data and to explore the potential cause(s) for the unexplained phenomenon, a systematic study was performed. The results revealed that the ‘amplifying’ effect at low concentrations did not exist. And those seemingly ‘flawless’ literature data were proven to be artefacts. The sign of specific rotation for 3-stearoyl-sn-glycerol was shown to be changeable with dilution, providing a warning for the risk in assignment of absolute configurations of similar compounds on the basis of a single point optical rotation data.     

Continuous flow structuring of anisotropic biopolymer particles

We review concepts and provide examples for the controlled structuring of biopolymer particles in hydrodynamic flow fields. The structuring concepts are grouped by the physical mechanisms governing drop deformation and shaping: (i) capillary structuring, (ii) shear and elongational structuring and (iii) confined flow methods. Non-spherical drops can be permanently structured if a solidification process, such as gelation or glass formation in the bulk or at the interface, is superimposed to the flow field. The physical and engineering properties of these processes critically depend on an elaborate balance between capillary phenomena, rheology, gel or glass formation kinetics, and bulk heat, mass and momentum transfer in multiphase fluids. This overview is motivated by the potential of non-spherical suspension particles, in particular those formed from ‘natural’ and ‘sustainable’ biopolymers, as rheology modifiers in food materials, consumer products, cosmetics or pharmaceuticals.     

Immobilization of Ru(III) complex on silica: a heterogenized catalyst for selective oxidation of alcohols in water at room temperature

We have developed a heterogenized catalyst (‘SiO₂’–NH₂–Ru^III) by the immobilization of [Ru(acac)₂(CH₃CN)₂]PF₆ on SiO₂. The catalyst was characterized by SEM, solid state NMR, EPR, FT-IR, ICP, and BET surface area analyses. ‘SiO₂’–NH₂–Ru^III catalyzed the selective oxidation of alcohols with periodic acid in water at room temperature. This protocol was applicable to the controlled oxidation of structurally diverse primary and secondary alcohols. The catalyst could be quantitatively recovered and reused up to six cycles without significant loss of catalytic activity.     

A highly selective and sensitive perylenebisimide-based fluorescent PET sensor for Al determination in MeCN

A novel ‘turn-on’ fluorescent probe with perylene tetracarboxylic bisimide (PBI) as the fluorophore and di(2-(salicylideneamino))ethylamine (DSEA) as the metal ion receptor was designed. The capability of the prepared probe to detect metal ions was evaluated by the changes in its emission intensity. The probe demonstrated a considerable emission enhancement (ca. 110-fold) in the presence of Al³⁺ in MeCN with high selectivity and sensitivity. Furthermore, the considerably ‘off–on’ fluorescence response concomitantly led to the apparent color change from colorless to brilliant yellow, which could also be identified by naked eye easily under UV lamp.     

“Click” immobilized perphenylcarbamated and permethylated cyclodextrin stationary phases for chiral high-performance liquid chromatography application

Two cyclodextrin-based chiral stationary phases have been prepared by immobilization of functionalized mono-6-azido-β-CD derivatives to alkynyl modified silica via “click” chemistry and applied to the HPLC enantioseparation of various chiral compounds. The perphenylcarbamated CD CSP (CCP-CSP) exhibited excellent chiral recognition of a wide range of analytes including racemic aryl alcohols, flavonoids, bendroflumethiazide, atropine and some β-blockers. Methanol proved to be a better organic modifier than acetonitrile for most of the analytes with the exception of bendroflumethiazide. The “click” chemistry immobilized permethylated CD CSP (CCM-CSP) afforded poor chiral recognition for most analytes, but could resolve non-aromatic ionone derivatives which were not separated on CCP-CSP. These results suggest that resolution with cyclodextrin derived CSPs depend on a complex interplay of ‘host’–‘guest’ inclusion, hydrogen bonding, π–π and hydrophobic interactions.     

Application of probabilistic neural networks in qualitative analysis of near infrared spectra: determination of producing area and variety of loquats

Near infrared (NIR) spectra of a sample can be treated as a signature, allowing samples to be grouped on basis of their spectral similarities. Near infrared spectroscopy (NIRS) combined with probabilistic neural networks (PNN) have been used to discriminate producing area and variety of loquats. Two varieties of loquats (‘Dahongpao’ and ‘Jiajiaozhong’) picked from two producing areas of ‘Tangxi’ and ‘Cunan’ in Zhejiang province were analyzed in this study. Principal component analysis (PCA) was applied before PNN modeling and the results indicated that the dimension of the vast spectral data can be effectively reduced. For each model, half samples were used to train the network and the remaining half were used to test the network. The results of the PCA-PNN models for discriminating the variety of samples from the same producing area or for discriminating the producing area of the same variety samples were much better than those of the PCA-PNN models for discriminating variety or producing area of all loquat samples. The results of this study show that NIRS combined with PCA-PNN is a feasible way for qualitative analysis of discriminating fruit producing areas and varieties.     

Dispersive kinetic models for isothermal solid-state conversions and their application to the thermal decomposition of oxacillin

The authors recently published works in which the use of two novel equations for modeling the dispersive kinetics observed in various solid-state conversions are described. These equations are based on the assumptions of a ‘Maxwell-Boltzmann (M-B)-like’ distribution of activation energies and a first-order rate law. In the present work, it is shown that it may be possible to expand the approach to include mechanisms other than first-order, i.e. some of those commonly encountered in the field of thermal analysis, thus obtaining ‘dispersive versions’ of these kinetic models. The application of these dispersive kinetic models to the slightly sigmoidal, isothermal conversion-time (x-t) data of Rodante and co-workers for the degradation of the antibiotic, oxacillin, is described. This is done in an effort to test the limitations of the proposed dispersive models in describing kinetic data which is not clearly sigmoidal (i.e. as shown in previous works). Finally, it is demonstrated that, using graphical analysis, the typically sigmoidal x-t plots of first-order dispersive processes are the direct result of (asymmetric) activation energy distributions that are either ‘∩-shaped’ (for heterogeneous conversions) or ‘∪-shaped’ (for homogeneous conversions) in appearance, i.e. when the activation energy is plotted as a function of conversion. This finding lends support to the founding hypothesis of the authors’ approach for modeling dispersive kinetic processes: the existence of ‘M-B-like’ distributions of activation energies.     

Gas-sensing properties of Fe2−xTixO3+γ (x = 0–1.4)

As part of a systematic study of mechanisms of response of semiconducting oxides as trace gas sensors, we have explored the behaviour of iron–titanium oxide solid solutions Fe_2−xTi_xO₃ (x = 0.1–1.4). The materials were single-phase for x = 0.1 with increasing proportions of a pseudobrookite second phase at higher degree of substitution. Unmodified, pure iron oxide does not show sensitivity to CO. A significant signal was developed for x = 0.1, that then diminished with increasing x and was lost for x = 1.4. Three effects have been deduced important for the gas response: significant surface segregation of Ti at low Ti content; grain growth inhibition and agglomeration into more massive, non-porous lumps as Ti content increased; and the appearance of a band-gap state associated with Fe(II) at higher Ti content. The effects of microstructure change have been analyzed by fitting the data to a simple 2-resistor model of gas-insensitive ‘grains’ in series with gas-sensitive ‘grain boundaries’. A Mars–van Krevelen type model for the response is presented, based on reactions at surface-segregated defect clusters, to develop and remove electrically-active surface trap states.     

Li2MnO3-based composite cathodes for lithium batteries: A novel synthesis approach and new structures

A new, simple technique has been demonstrated for fabricating high-capacity composite electrode structures. In this technique, Li₂MnO₃ is leached in acid in the presence of soluble transition metal ions and subsequently annealed between 450 and 850 °C. The technique can be used to prepare a wide variety of composite compounds, in particular, a new family of ‘layered–rocksalt’ xLi₂MnO₃·(1−x)MO (e.g., M = Ni and Co) structures and modifications thereof, as well as ‘layered–layered’ xLi₂MnO₃·(1−x)LiMO₂ (e.g., M = Mn, Ni, and Co) and ‘layered–spinel’ xLi₂MnO₃·(1−x)LiM₂O₄ (e.g., M = Mn and Ni). This novel approach also holds promise for 1) synthesizing materials that reduce the extent of internal phase transitions of composite cathode structures with a high manganese content, and 2) minimizing the extent to which cells need to be electrochemically activated to remove Li₂O, thereby reducing the extent of the irreversible capacity loss on the first charge/discharge cycle.