( S )-(?)-α-Methylbenzylamine as chiral auxiliary in the synthesis of (+)-lortalamine

Abstract  

(+)-Lortalamine was synthesised using (S)-(−)-α-methylbenzylamine as a chiral auxiliary. The stereochemistry of an intermediate compound was established on the basis of X-ray crystallography, allowing unambiguous assignment of the absolute configuration.     

(<Emphasis Type="Italic">S</Emphasis>)-(−)-α-Methylbenzylamine as chiral auxiliary in the synthesis of (+)-lortalamine

Abstract  (+)-Lortalamine was synthesised using (S)-(−)-α-methylbenzylamine as a chiral auxiliary. The stereochemistry of an intermediate compound was established on the basis of X-ray crystallography, allowing unambiguous assignment of the absolute configuration. Graphical abstract        

A search of an optimal carrier for immobilization of chitin deacetylase

Chitin deacetylase is an enzyme that can play an important role in enzymatic deacetylation of chitosan to obtain polymers with a lower degree of acetylation. As this enzyme has never been immobilized up to now, efforts were directed towards determining both the most suitable carrier and the best method of covalent attachment to the selected carrier. In the preliminary experiments several different carriers were tested that were based on acrylic, silica-gel, agarose, dextran or cellulose materials. The best results were obtained for cellulose-based Granocel matrix. DEAE- and NH₂-Granocel activated with divinyl sulfone or glutaraldehyde were chosen for optimization of the immobilization procedure and the carrier’s superstructure. It was found that covalent binding of chitin deacetylase on DEAE-Granocel-2000 via divinyl sulfone offers preparations with the highest activity and stability. The characteristics of the selected preparation and comparison with the native enzyme show that optimal conditions are close to those for the free enzyme: the optimal pH is 4.0 for both enzymes and the optimal temperatures are 55 °C and 50 °C for native and immobilized forms, respectively. The kinetics of chitosan deacetylation for both enzymes follow the Michaelis–Menten relationship, but significant differences in the values of the equation parameters were observed.     

LC Separation of Fatty Acid Ceramides Using a Two Column System

Type II ceramides were separated according to the length of their fatty acid alkyl chain using two column system. The packing of the first column was non-polar adsorbent prepared by coating of macroporous spherical silica with cationized poly(vinyl alcohol) of low substitution degree. Commercial normal phase column Lichrosorb Si 60 was used as a second column in this system. Elution was performed in an isocratic mode using methanol:chloroform 50:50 (v/v) as an eluent.     

Cinnamon as a Useful Preventive Substance for the Care of Human and Plant Health

Cinnamon is widely used as a food spice, but due to its antibacterial and pharmacological properties, it can also be used in processing, medicine and agriculture. The word “Cinnamon” can refer to the plant, processed material, or an extract. It is sometimes used as a substance, and sometimes used as a mixture or as compounds or a group. This article reviews research into the effectiveness of various forms of cinnamon for the control of plant diseases and pests in crops and during storage of fruit and vegetables. Cinnamon acts on pests mainly as a repellent, although in higher doses it has a biocidal effect and prevents egg-laying. Cinnamon and its compounds effectively hinder bacterial and fungal growth, and the phytotoxic effects of cinnamon make it a possible herbicide. This article presents the wide practical use of cinnamon for various purposes, mainly in agriculture. Cinnamon is a candidate for approval as a basic substance with protective potential. In particular, it can be used in organic farming as a promising alternative to chemical pesticides for use in plant protection, especially in preventive treatments. The use of natural products is in line with the restriction of the use of chemical pesticides and the principles of the EU’s Green Deal.     

The Effect of Supporting Electrolyte Concentration on Zinc Electrodeposition Kinetics from Methimazole Solutions

The kinetic parameters of Zn²⁺ ion electroreduction in sodium perchlorate used as the supporting electrolyte on the mercury electrode in the presence of methimazole were determined using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and DC polarography. The two‐stage nature of this process was demonstrated. Both steps are catalysed by a methimazole. The size of the acceleration effect depends on the concentrations of methimazole and the supporting electrolyte. The acceleration of the electrode process involves the formation of active complexes between the depolarizer ions and methimazole on the electrode surface. These complexes facilitate the exchange of charge between the electrode and zinc ions during electroreduction process. The change of the hydrating sphere of the zinc ion is also important here. This in turn depends on its oxidation state and the concentration of the supporting electrolyte.     

Amphiphilic Polymethyloxazoline–Polyethyleneimine Copolymers: Interaction with Lipid Bilayer and Antibacterial Properties

Polycations, mimicking activity of antibacterial peptides, belong to an important class of molecules investigated as a support or as an alternative to antibiotics. In this work, studies of modified linear amphiphilic statistical polymethyloxazoline (PMOX) and polyethyleneimine copolymers (PMOX_PEI) series are presented. Variation of PEI content in the structure results in controllable changes of polymeric aggregates zeta potential. The structure with the highest positive charge shows the best antimicrobial activity, well visible in tests against model Gram‐positive and Gram‐negative bacteria, fungi, and mycobacterium strains. The polymer toxicity is evaluated with MTT and hemolysis assay as a reference. Quartz crystal microbalance (QCM‐D) is used to investigate interaction between polycations and a model lipid membrane. Polymer activity correlates well with molecular structure, showing that amphiphilic component is altering polymer behavior in contact with the lipid bilayer.     

A combined experimental and theoretical study of the pH‐dependent binding mode of NAD+ by water‐soluble molecular clips

The highly selective recognition process of NAD⁺ and NADH (as important cofactors of many redox enzymes) by molecular clips in aqueous solution is studied systematically by a combined experimental and quantum‐chemical approach. The strongly pH‐dependent complexation‐induced ¹H NMR shifts of the guest molecule indicate that in buffered aqueous solution at pH = 7.2 the nicotinamide ring, the active site of NAD⁺, is preferentially bound inside the cavity of the molecular clip, whereas in pure water under slightly acidic conditions both units (the nicotinamide ring as well as the adenine moiety) are located outside the cavity. The latter finding is explained by a competing self‐aggregation of NAD⁺ which prohibits the recognition process. In addition, the investigation of the NAD⁺ fragments NMNA, NMN, and AMP as well as the comparison of measured and computed chemical shieldings provides information on possible binding modes. Under equal conditions the binding of NADH to the molecular clip is significantly weaker than that of NAD⁺, so that the oxidation states (NAD⁺/NADH) can be distinguished by the molecular clips. The nucleotides NMN and AMP are bound less strongly by the molecular clips than NAD⁺. The weaker binding indicates that multiple aromatic π?π and cation?π host–guest interactions only possible in NAD⁺ have a synergetic effect on the complex stability. In addition to the inhibition of the cofactor NAD⁺, a further implication is the development of sensors since a quenching of fluorescence is observed for specific molecular clips by the addition of NAD⁺. Copyright © 2009 John Wiley & Sons, Ltd.     

Exercise-induced motor improvement after complete spinal cord transection and its relation to expression of brain-derived neurotrophic factor and presynaptic markers

Background  

It has been postulated that exercise-induced activation of brain-derived neurotrophic factor (BDNF) may account for improvement of stepping ability in animals after complete spinal cord transection. As we have shown previously, treadmill locomotor exercise leads to up-regulation of BDNF protein and mRNA in the entire neuronal network of intact spinal cord. The questions arise: (i) how the treadmill locomotor training, supplemented with tail stimulation, affects the expression of molecular correlates of synaptic plasticity in spinal rats, and (ii) if a response is related to BDNF protein level and distribution.     

Electrochemical Sensing of Pb2+ and Cd2+ Ions with the Use of Electrode Modified with Carbon-Covered Halloysite and Carbon Nanotubes

A novel voltammetric method for the sensitive and selective determination of cadmium and lead ions using screen-printed carbon electrodes (SPCEs) modified with carbon-deposited natural halloysite (C_Hal) and multi-walled carbon nanotubes (MWCNTs) was developed. The electrochemical properties of the proposed sensor were investigated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), while the morphology and structure were established by scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). A two-factorial central composite design (CCD) was employed to select the composition of the nanocomposite modifying the electrode surface. The optimal measuring parameters of differential pulse anodic stripping voltammetry (DPASV) used for quantitative analysis were established with the Nelder–Mead simplex method. In the analytical investigation of Cd(II) and Pb(II) ions by DPASV, the MWCNTs/C_Hal/Nafion/SPCE exhibited a linear response in the concentration range of 0.1–10.0 µmol L⁻¹ (for both ions) with a detection limit of 0.0051 and 0.0106 µmol L⁻¹ for Pb(II) and Cd(II), respectively. The proposed sensor was successfully applied for the determination of metal ions in different natural water and honey samples with recovery values of 96.4–101.6%.