Volume 64, Issue 6

Biological studies showed that assembles of biomolecules can dramatically change their physiological effectiveness. Covalent coupling of different types of biomolecules leads to novel biomacromolecules of different properties. Generally, bioconjugate chemistry opens a new dimension in biomedical and biotechnology research. In this review, some important chemical methods of bioconjugates preparation used in the practice are described. Proteins and saccharides modification methods and employment of linkers used to achieve new functionalities are discussed. Common bioconjugation methods are emphasized and novel methods from recent years are described. Except in chemistry, benefits and limits of the studied methods are outlined.

This manuscript presents an overview of the research performed on Talaromyces flavus, a microorganism remarkable for its secondary metabolites with unique biological activities, enzymes applicable in the synthesis of saccharides, preparation of chiral building blocks or biotransformations, and for its application in pest biocontrol.

A highly sensitive spectrophotometric method for palladium determination using piroxicam and tenoxicam as new chromogenic reagents has been developed. In the presence of sodium lauryl sulfate (SLS), palladium reacts with piroxicam (PX) or tenoxicam (TX) to form stable yellow orange complexes in an acetate buffer solution of pH 5.0 at 424 nm and 426 nm with molar absorptivity of 7.16 × 104 L mol−1 cm−1 and 1.20 × 105 L mol−1 cm−1, respectively. Sandell sensitivity, detection, and quantitation limits were also calculated. Optimum conditions were evaluated considering pH, reagent concentration, time, temperature, and surfactant concentration. The complex system conforms to Beer’s law over the range of 0.07–1.28 μg mL−1 palladium. The stoichiometric ratio and stability constant were also evaluated. Tolerance limits of many cations and anions were determined. Finally, the proposed method was applied successfully in the determination of palladium in jewellery, anode mud, synthetic mixtures, catalysts, and alloy samples.

Effect of the addition of six different anions on the absorption and fluorescence spectra of acridine yellow G (AYG) was examined. Only the F− anion could induce a visible color change observable with naked eye and a strong fluorescence quenching with K SV of 8.3 × 104 mol−1 L in CH3CN solutions. Calculated results of the interaction between the F− anion and acridine yellow G using the B3LYP/6-31G(d) program showed that the intermolecular charge transfer through the formation of an H-bond between AYG and F− is an essential sensor mechanism.

Catechin and epicatechin were analysed in the peel of six apple cultivars (three resistant and three non-resistant to apple scab). Two methods of analytical sample preparation following extraction were tested: solid phase extraction and column separation with Sephadex LH-20 coupled to a differential refractometric detector. Prior to GC and GC-MS analyses, these compounds were silylized. This permitted co-injection with standards and the comparison of retention values and mass spectra with those recorded for standards. The content of catechin and epicatechin in apple peel is discussed in relation to the resistance of apple trees to scab.

This work presents the use of sulfated tin oxide enhanced with SiO2 (SO42−/SnO2-SiO2) as a superacid solid catalyst to produce methyl esters from Jatropha curcas oil. The study was conducted using the design of experiment (DoE), specifically a response surface methodology based on a threevariable central composite design (CCD) with α = 2. The reaction parameters in the parametric study were: reaction temperature (60°C to 180°C), reaction period (1 h to 3 h), and methanol to oil mole ratio (1: 6 to 1: 24). Production of the esters was conducted using an autoclave nitrogen pressurized reactor equipped with a thermocouple and a magnetic stirrer. The maximum methyl esters yield of 97 mass % was obtained at the reaction conditions: temperature of 180°C, reaction period of 2 h, and methanol to oil mole ratio of 1: 15. The catalyst amount and agitation speed were fixed to 3 mass % and 350–360 min−1, respectively. Properties of the methyl esters obtained fell within the recommended biodiesel standards such as ASTM D6751 (ASTM, 2003).

The impact of pH and washing procedure on calcium and magnesium distribution between pulp and filtrate in pulp processing was investigated. Depending on media pH, the elements are present in the form of ions (Ca2+, Mg2+) and hydrated oxides (Ca(OH)2, Mg(OH)2). Distribution was monitored using binary systems of CaCl2 and MgCl2 dissolved in deionized water or Ca2+ and Mg2+ ions present in filtrates from an industrial pulp mill. Complying with the relevant standards in force, Ca and Mg contents are expressed as CaO and MgO. The study was aimed at obtaining mathematic relations between pH and calcium and magnesium, as two important non-process elements, sorption on pulp. Distribution of the elements between pulp and liquid (filtrate or water) was determined with analytical procedures and simulation of pulp washing. It was found that both pH and filtrate composition influenced sorption/desorption of the elements on/from pulp. Filtrate from a pulp mill, mainly content of organic substances in liquid phase, affects their sorption on pulp and desorption to liquid. The higher the pH value the more efficient the sorption of the elements, magnesium being sorbed on pulp in higher amounts than calcium. Prevalence of the sorbed magnesium is preserved even at lower concentrations of both elements. Distribution of the elements between pulp and solution is expressed through mathematic relations which, in turn, can be employed to purposefully modify or optimize the distribution between the solid (pulp) and liquid (filtrate) media. Moreover, rationalized exploitation of mathematical relations enables balancing the elements within a cellulose manufacture, regulating media recycling, and predicting an eventual impact on technological processes.

Influence of electrode morphology on electrochemical properties of lead dioxide electrodes (β-PbO2) for oxygen-ozone evolution reactions in acid medium was investigated using scanning electronic microscopy (SEM), cyclic voltammetry (CV), polarization curves (PC), and determination of the current efficiency (Φ). Experimental findings revealed that application of high electrodeposition current densities furnishes more rough β-PbO2 films. Surface characteristics were verified by SEM images and the analysis of interfacial pseudo-capacitances and morphology factor (φ). Kinetic study of the overall electrode process (O2 + O3) based on the analysis of the Tafel slope revealed that the electrode morphology and electrolyte composition considerably affect the electrode kinetics. In most cases, the existence of two Tafel slopes distributed in the low and high overpotential domains was observed. Abnormal Tafel slopes (b ≠ 120 mV) obtained for the primary water discharge step during water electrolysis were interpreted considering the apparent charge transfer coefficient (α apa). Optimum conditions for the ozone production were obtained for the less rough β-PbO2 electrode immersed in a sulfuric acid solution (1.0 mol dm−3) containing KPF6 (30 × 10−3 mol dm−3), where the current efficiency of 15 mass % for the ozone production was obtained.

The synthesis of methyl acetoacetate (MAA) by methoxycarbonylation of acetone with dimethyl carbonate (DMC) was carried out in the presence of MgO and alkali-promoted MgO catalysts. From among Li, Na, K, and Cs, potassium was found to be the most effective promoter to improve the activity of MgO. The effect of K/MgO with variable content of K was also investigated, and the individual catalysts were characterised by the XRD, BET, SEM, CO2-TPD, and in situ CO2 IR techniques. The results showed that the addition of a small amount of K (1.97 mass %) could promote MAA formation, but a higher K loading caused a decrease in the yield of MAA, which might result from particle agglomeration and the presence of stable potassium carbonates. In situ FTIR experiments of co-adsorbed reactants indicated that the reaction probably proceeded via abstraction of Hα from acetone by base sites.

Deuterated dinuclear ruthenium(II,III) 3,4,5-tri(ethoxy-d 5)benzoate, [Ru2{3,4,5-(C2D5O)3C6H2-COO}4Cl]n, was synthesized by a reaction of [Ru2(C2H5COO)4Cl]n and 3,4,5-tri(ethoxy-d 5)benzoic acid and characterized by single-crystal X-ray analysis as well as IR, UV-VIS, and 1H NMR spectra, and compared with those of the undeuterated complex [Ru2{3,4,5-(C2H5O)3C6H2COO}4Cl]n. Single-crystal X-ray analysis showed that chloride ligands bridge the dinuclear ruthenium(II,III) units at the axial positions to form a zigzag chain molecule with the Ru1-Cl-Ru2 angle of 123.82(4)°. 1H NMR spectra in CD2Cl2 displayed a broad signal attributable to o-H atoms on the phenyl rings of the benzoate ligands from approximately δ = 23 to δ = 32 at 25°C and several signals from approximately δ = −50 to δ = 50 at −80°C. These spectra show the preservation of the polymeric or oligomeric chain structure in dichloromethane, which is supported by the solution behavior confirmed by the UV-VIS spectra and electronic conductance.

A series of poly(vinyl alcohol) (PVA)/poly(γ-benzyl l-glutamate)-block-poly(ethylene glycol) (PBLG-b-PEG) blend membranes with different PVA/PBLG-b-PEG mole ratios were prepared by pervaporation. Structure and morphologies of PVA/PBLG-b-PEG blend membranes were investigated using Fourier transformation infrared spectroscopy (FTIR), and atomic force microscopy (AFM). Mechanical and chemical properties of PVA/PBLG-b-PEG blend membrane were studied by tensile testing and other physical methods. It was revealed that the introduction of PBLG-b-PEG copolymer has significant effect on the properties of a PVA membrane.

Anilinium 5-sulfosalicylate was prepared and characterized by elemental analysis, and FTIR and NMR spectroscopies. It was polymerized in an aqueous solution using ammonium peroxydisulfate as an oxidant. The precipitated polyaniline 5-sulfosalicylate exhibited high thermal stability and conductivity of 0.13 S cm−1. Its mass-average molar mass and polydispersity index were determined by gel-permeation chromatography as 22,900 g mol−1 and 2.7, respectively. Elemental analysis and FTIR spectroscopy study of polyaniline 5-sulfosalicylate revealed the doping level and the oxidation state between emeraldine and protoemeraldine salt while corresponding studies of the polyaniline base indicate a small extent of the covalent bonding of 5-sulfosalicylate anions to polyaniline chains.

A number of poly(N-isopropylacrylamide) (polyNIPAM) microgels were prepared with dimethacrylate cross-linking agents of various lengths, ether and ester groups in the backbone, and pendant vinylidine functionality. These materials were characterized by examining their morphological patterns using optical and scanning electron microscopy. When ethylene glycol dimethacrylate (EGDMA) was used as a cross-linking agent, microspheres of approximately 1 μm in diameter were obtained. Diethylene glycol dimethacrylate (DEGDMA) cross-linking resulted in relatively large spherical structures (1–5 μm) as well as spherical nanostructures (200 nm). Using triethylene glycol dimethacrylate (TEGDMA) resulted in spheres with diameters between 1 μm and 3 μm. The hydrodynamic particle diameter decreased with the increasing chain length of the dimethacrylate cross-linking agents. The turbidity increased with the temperature of transition points occurring at approximately 31–32°C confirming the thermosensitivity of the obtained polymeric structures.

In our experimental work on carbon nanotubes synthesis, the influence of pre-treatment and reaction temperature conditions over Fe catalyst loaded on low-cost activated carbon (AC) in the catalytic chemical vapor deposition of methane was studied. Catalyst with the metal concentration of 5 mass % calcined at 350°C and reduced at 450°C was effective in CH4 decomposition giving 98 % conversions. TEM images showed that thin multi-walled carbon nanotubes (MWNTs) with the average internal diameter of ∼ 8 nm and the wall thickness of ∼ 2.5 nm were obtained over unreduced Fe/AC catalyst at the reaction temperature of 850°C. On the other hand, broader filamentous nanostructures with the diameter of ∼ 22 nm and the wall thickness of ∼ 3.72 nm were observed over reduced catalyst.

Perkin condensation with subsequent intramolecular lactonisation as one pot syntheses of 2-(2-oxo-2H-chromen-3-yl)acetic acids VIIa-Xa has been studied. The required acids VIIa-Xa were prepared as precursors of recently discovered compounds possessing antineoplastic activities. Syntheses of VIIa-Xa were carried out using para substituted 2-hydroxybenzaldehydes II-VI, succinic acid anhydride, sodium succinate under thermal or microwave conditions. Significant shortening of the reaction time under microwave irradiation was observed (18–50 min instead of 1.5–5 h of heating). Microwave assisted reactions proceeded more smoothly to give higher yield of the required products VIIa-Xa (31–61 %) compared to those under classical thermal conditions e.g. 21.8 % for IXa (Hurenkamp et al., 2007). Seven reaction by-products were isolated and determined as 2H,2′H-3,3′-bichromene-2,2′-diones VIIb-Xb and (E)-3-(2-hydroxystyryl)-2H-chromen-2-ones VIIc-IXc.

For the first time, synthesis of AB ring core of camptothecin synthons such as (2-chloroquinolin-3-yl)methanols (Va-Vg) using zinc oxide nanoparticles is reported. The desired attractive products were obtained in high yields, short reaction time, using a simple work-up procedure with the purification of products by non-chromatographic methods.

Enol lactones such as 4-hydroxy-6-methyl-2H-pyran-2-one (triacetic acid lactone, TAL) and 4-hydroxycoumarin when treated with 2-amino-3-formylchromone under basic conditions afforded 3-acetoacetyl benzopyranopyridones and benzopyranopyridines, respectively. A series of pyrazole derivatives was prepared by the reaction of 3-acetoacetyl benzopyranopyridones with different hydrazines. All compounds were characterised on the basis of spectral data and their antibacterial activity evaluated.

Polyethylene glycol was found to be an inexpensive non-toxic and effective medium for one pot synthesis of high yields of decahydroacridine-1,8-diones in the presence of ceric ammonium nitrate as the catalyst. Moreover, the solvent can be recovered and reused.