Professor Dr. Monika Waksmundzka-Hajnos — In honor of her birthday

JPC – Journal of Planar Chromatography – Modern TLC -     

Comparison of Calculated Values of the Lipophilicity of 2,6-Disubstituted 7-Methylpurines with Values Determined by RPTLC

JPC – Journal of Planar Chromatography – Modern TLC - The lipophilicity of 2,6-disubstituted 7-methylpurines and 6-mer-captopurine has been determined by reversed-phase thin-layer...     

Fluorescent Turn-On Probes for the Development of Binding and Hydrolytic Activity Assays for mRNA Cap-Recognizing Proteins

The m⁷G cap is a unique nucleotide structure at the 5′-end of all eukaryotic mRNAs. The cap specifically interacts with numerous cellular proteins and participates in biological processes that are essential for cell growth and function. To provide small molecular probes to study important cap-recognizing proteins, we synthesized m⁷G nucleotides labeled with fluorescent tags via the terminal phosph(on)ate group and studied how their emission properties changed upon protein binding or enzymatic cleavage. Only the pyrene-labeled compounds behaved as sensitive turn-on probes. A pyrene-labeled m⁷GTP analogue showed up to eightfold enhanced fluorescence emission upon binding to eukaryotic translation initiation factor 4E (eIF4E) and over 30-fold enhancement upon cleavage by decapping scavenger (DcpS) enzyme. These observations served as the basis for developing binding- and hydrolytic-activity assays. The assay utility was validated with previously characterized libraries of eIF4E ligands and DcpS inhibitors. The DcpS assay was also applied to study hydrolytic activity and inhibition of endogenous enzyme in cytoplasmic extracts from HeLa and HEK cells.     

Antiepileptic Drug Tiagabine Does Not Directly Target Key Cardiac Ion Channels Kv11.1, Nav1.5 and Cav1.2

Tiagabine is an antiepileptic drug used for the treatment of partial seizures in humans. Recently, this drug has been found useful in several non-epileptic conditions, including anxiety, chronic pain and sleep disorders. Since tachycardia—an impairment of cardiac rhythm due to cardiac ion channel dysfunction—is one of the most commonly reported non-neurological adverse effects of this drug, in the present paper we have undertaken pharmacological and numerical studies to assess a potential cardiovascular risk associated with the use of tiagabine. A chemical interaction of tiagabine with a model of human voltage-gated ion channels (VGICs) is described using the molecular docking method. The obtained in silico results imply that the adverse effects reported so far in the clinical cardiological of tiagabine could not be directly attributed to its interactions with VGICs. This is also confirmed by the results from the isolated organ studies (i.e., calcium entry blocking properties test) and in vivo (electrocardiogram study) assays of the present research. It was found that tachycardia and other tiagabine-induced cardiac complications are not due to a direct effect of this drug on ventricular depolarization and repolarization.     

Rapid analysis of organic farming insecticides in soil and produce using ultra-performance liquid chromatography/tandem mass spectrometry

A new method for the analysis of three ecological insecticides, namely azadyrachtin, spinosad (sum of spinosyn A and spinosyn D) and rotenone, in produce and soil samples is presented. Investigated compounds are one of the most significant insecticides authorized for organic farming crop protection in many countries. Extraction of the pesticides from plant and soil matrices was performed by using a modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) method. The method entailed a single extraction of the investigated compounds with acidified acetonitrile followed by a dispersive solid-phase extraction cleanup step prior to the final determination by reverse-phase ultra-performance liquid chromatography/tandem quadrupole mass spectrometry (UPLC-MS/MS). Validation studies were carried out on cabbage, tomato and soil samples. Recoveries of the spiked samples were in the range between 67% and 108%, depending on the matrix and the spiking level. Relative standard deviations for all matrix–compound combinations did not exceed 12%. The limits of quantification were ≤0.01 mg kg⁻¹ in all cases, except for azadirachtin. The developed method was applied to the analysis of real samples originating from organic farming production.     

Intermolecular interactions in normal-phase HPLC systems with alcohol hydrocarbon eluents

Summary We apply our new retention model introduced elsewhere to the studies of intermolecular interactions between the solute and the remaining components of a normal-phase HPLC system using a binary mobile phase consisting of an alcohol and a hydrocarbon. This can be achieved through the analysis of the regressional parameters A, B, and C appearing in the relationship of solute retardation (R_F) vs. mobile phase composition. Negative values of these parameters indicate a greater affinity of the solute to the stationary phase than to a given mobile phase moiety, whereas positive values have a reverse meaning. According to the absolute values of A, B, and C solute groups can be arranged according to the affinity toward a given mobile phase moiety, which is a detailed and important information regarding their separation, the stationary phase and with each individual constituent of the mobile phase.     

Chromatographic determination of solubility of low soluble substances the physico-chemical basis

The physico-chemical basis for a direct chromatographic determination of solubility of low soluble substances by means of adsorption and partition TLC is discussed. This method is a practical consequence of the chromatographic binary solutions model, a new semi-empirical approach based on phenomenological thermodynamics.

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Chromatographische Bestimmung der Löslichkeit von schwerlöslichen Substanzen. Die physikalisch-chemische Basis (Kurze Mitteilung)

Zusammenfassung Die physikalisch-chemische Basis einer direkten chromatographischen Bestimmung der Löslichkeit von schwerlöslichen Substanzen mit Hilfe der Adsorptions- und Verteilungsdünnschichtchromatographie wird diskutiert. Die Möglichkeit einer solchen Bestimmung ist die praktische Konsequenz des chromatographischen Modells der binären Lösungen, einer neuen semiempirischen, auf der phänomenologischen Thermodynamik begründeten Methode.

     

Thermogravimetric investigation ofwastes from electrical and electronic equipment (WEEE)

Two components of electronic wastes (sample A – a mixture of three types of printed circuit boards, sample B – a mixture of electronic junctions with metal wires) were investigated using thermogravimetric analysis (TG). Thermogravimetric and derivative thermogravimetric data (TG and DTG) give information on the thermal stability of A and B samples and allows finding the correct conditions for their degradation using pyrolysis in an experimental system, built on the laboratory scale for utilization of hazardous wastes. X-ray fluorescence measurements prove that brominated flame retardant is present in sample A, whilst chlorinated flame retardant is a probable component of sample B. Preliminary liquid chromatography of oil products obtained as a result of thermal waste degradation shows that the hydrocarbons released during pyrolysis could be used as a fuel.     

Application of organolithium and related reagents in synthesis. Part 25: Novel specific synthesis of the 4-arylisochroman-3-acetic acids via conversion of benzoic acids

The transformation of the benzanilides 1 into 4-arylisochroman-3-acetic acids 8 applying the following sequence of reactions is described. At first, the 3-arylphthalides 3 were obtained via metallation [n-BuLi] of benzanilides 1 and subsequent treatment of the generated bis-lithiated anilides 2 with aromatic aldehydes. Next, the 3-arylphthalides 3 were reduced [LiBH₄] to phthalanes 5 and then, via reductive metallation [Li/C₁₀H₈] and reaction of the generated bis-lithiated species 6 with dimethylformamide, 3-hydroxy-4-arylisochromans 7 were produced. In the final step the isochromans 7 were treated with 1-methoxy-1-trimethylsilyloxyethene in the presence of titanium tetrachloride and furnished 4-arylisochromans-3-acetic acid methyl esters 8 as trans stereoisomers (Ψ-e/e).