Kazimierz Surowiec

Proton di-ionizable p-tert-butylcalix[4]arene-crown-6 compounds in cone, partial-cone and 1,3-alternate conformations: synthesis and alkaline earth metal cation extraction

Novel proton di-ionizable p-tert-butylcalix[4]arene-crown-6 compounds in cone, partial-cone and 1,3-alternate conformations are synthesized to compare the efficiency and selectivity with which they extract alkaline earth metal ions. In these ligands, a crown-6 polyether unit links alternate aromatic rings of the calix[4]arene framework. To the remaining lower-rim positions are attached oxyacetic acid or N-(X)sulfonyl oxyacetamide groups. Changing the conformation varies the spatial relationship between a polyether-complexed divalent metal ion and the ionized side arms of the ligands. This is found to markedly affect the efficiency and selectivity in competitive solvent extraction of alkaline earth metal ions from aqueous solutions into chloroform by the di-ionizable calix[4]arene-crown-6 ligands.

Electromigration Injection from a Small Loop in Capillary Electrophoresis

Capillary electrophoresis (CE) is now clearly the separation technique of the decade. One aspect that is still in need of improvement is concentration sensitivity, especially when CE is used in conjunction with on-column UV-visible absorptiometry, by far the most common practice. Electromigration injection (EI) is among the most prominent techniques in CE that serves to improve the attainable limits of detection; it is also the most convenient and simplest of all injection modes. Unfortunately, EI is affected both from sample to sample (the amount of an analyte introduced depends on sample conductance) and from analyte to analyte within a sample (the introduction is strongly biased on analyte electrical mobility). Previously we have shown the utility of small loops affixed at the tip of a capillary (Anal. Chem. 1995, 67, 3853-3860; 1996, 68, 1164-1168). The present paper shows that there are remarkable advantages to be gained from forming a film of the sample solution on a wire loop and using the loop itself as the high-voltage electrode to perform electromigration from a very small sample volume. The sample constituents can be essentially exhaustively electromigrated from this volume in less than 1 min, and the mobility induced bias is dramatically lowered. The observed experimental behavior agrees with theoretical models.

Augmenting Sulfur Metabolism and Herbivore Defense in Arabidopsis by Bacterial Volatile Signaling

Sulfur is an element necessary for the life cycle of higher plants. Its assimilation and reduction into essential biomolecules are pivotal factors determining a plant’s growth and vigor as well as resistance to environmental stress. While certain soil microbes can enhance ion solubility via chelating agents or oxidation, microbial regulation of plant-sulfur assimilation has not been reported. With an increasing understanding that soil microbes can activate growth and stress tolerance in plants via chemical signaling, the question arises as to whether such beneficial bacteria also regulate sulfur assimilation. Here we report a previously unidentified mechanism by which the growth-promoting rhizobacterium Bacillus amyloliquefaciens (GB03) transcriptionally activates genes responsible for sulfur assimilation, increasing sulfur uptake and accumulation in Arabidopsis. Transcripts encoding for sulfur-rich aliphatic and indolic glucosinolates are also GB03 induced. As a result, GB03-exposed plants with elevated glucosinolates exhibit greater protection against the generalist herbivore, Spodoptera exigua (beet armyworm, BAW). In contrast, a previously characterized glucosinolate mutant compromised in the production of both aliphatic and indolic glucosinolates is also compromised in terms of GB03-induced protection against insect herbivory. As with in vitro studies, soil-grown plants show enhanced glucosinolate accumulation and protection against BAW feeding with GB03 exposure. These results demonstrate the potential of microbes to enhance plant sulfur assimilation and emphasize the sophisticated integration of microbial signaling in plant defense.

Effect of para-substituents on alkaline earth metal ion extraction by proton di-ionizable calix[4]arene-crown-6 ligands in cone, partial-cone and 1,3-alternate conformations

Two carboxylic acid or N-(X)sulfonyl carboxamide groups were incorporated into calix[4]arene-crown-6 compounds to afford di-ionizable ligands for use in divalent metal ion separations. Acidities of the N-(X)sulfonyl carboxamide groups were tuned by variation of the electron-withdrawing properties of X. Cone, partial-cone and 1,3-alternate conformations were obtained by different synthetic strategies and their structures verified by NMR spectroscopy. Competitive solvent extractions of alkaline earth metal cations from aqueous solutions into chloroform were performed and the results compared with those reported previously for di-ionizable p-tert-butylcalix[4]arene-crown-6 analogues to probe the influence of the para-substituent on the calix[4]arene scaffold on extraction selectivity and efficiency.

Quantitative injection from a microloop. Reproducible volumetric sample introduction in capillary zone electrophoresis

A wire loop deployed at the tip of a capillary electrophoresis system has been investigated as a means of quantitative injection. A thin film of a liquid is formed on the loop, the loop is transferred to a sealed chamber, and then pneumatic pressure is applied to introduce the contents of the loop into the capillary. As long as the applied pressure is below a certain threshold, no air is introduced into the capillary, even after the loop contents have been fully introduced. Sample surface tension and viscosity do not have a significant effect on the injected volume. The small loop injection technique appears to be a robust and reproducible alternative to presently practiced approaches to sample injection in CE.

Effect of Pendant Group Length Upon Metal Ion Complexation in Acetonitrile by Di-Ionized Calix[4]Arenes Bearing Two Dansyl Fluorophores

A series of three di-ionizable calix[4]arenes with two pendant dansyl (1-dimethylaminonaphthalene-5-sulfonyl) groups linked to the lower rims was synthesized. Structures of the three ligands were identical except for the length of the spacers which connected the two dansyl groups to the calix[4]arene scaffold. Following conversion of the ligands into their di-ionized di(tetramethylammonium) salts, absorption and emission spectrophotometry were utilized to probe the influence of metal cation (Li+, Na+, K+, Rb+, Cs+, Mg2+, Ca2+, Sr2+, Ba2+, Ag+, Cd2+, Co2+, Fe2+, Hg2+, Mn2+, Pb2+, Zn2+ and Fe3+) complexation in acetonitrile. Upon complexation with these metal cations, emission spectra underwent marked red shifts and quenching of the dansyl group fluorescence for the di-ionized ligand with the shortest spacer. A similar effect was noted for the di-ionized ligand with an intermediate spacer for all of the metal ions, except Ba2+. For the di-ionized ligand with the longest spacer, the metal cations showed different effects on the emission spectrum. Li+, Mg2+, Ca2+ and Ba2+ caused enhancement of emission intensity with a red shift. Other metal cations produce quenching with red shifts in the emission spectra. Transition metal cations interacted strongly with all three di-ionized ligands. In particular, Fe3+ and Hg2+ caused greater than 99% quenching of the dansyl fluorescence in the di-ionized ligands.

The properties of poly(ethylene glycol) 20M layer on the surface of a silanized support

SummaryThe properties of poly(ethylene glycol) 20M (PEG 20M) on the silanized surface of Chromosorb W HMDS were investigated. Using “inverse” gas chromatography and x-ray diffraction methods it was found that on this surface PEG 20M is divided into two forms: a surface layer for τ below 0.105 of PEG 20M and an excess over the surface layer for loadings characterized by τ greater than 0.105 (τ is the ratio of the amount of stationary phase to the amount of uncoated support).The surface layer is characterized by the lack of melting point at the normal melting temperature of PEG 20M. The thickness of this layer is equal to 830 Å.

The structure and chromatographic properties of poly(ethylene glycol) 20M layer on the surface of a diatomaceous earth type support

SummaryThe properties of poly(ethylene glycol) 20M (PEG 20M) coated on the hydroxylated surface of Chromaton N AW were investigated by inverse gas chromatography. It was found that the solid form of PEG 20M exhibits partition as the retention mechanism even below its melting range. The contribution of adsorption to the specific retention volume was also determined. It was demonstrated that inverse gas chromatography establishes the existence of a polymer surface layer but precise determination of its thickness is difficult. The limitation of the applicability of inverse gas chromatography results from the structure of the investigated surface layer which is thin and not coherent so that solute molecules can penetrate it.

The retention mechanism in poly(ethylene glycol) 20M layer on the surface of a silanized support

SummaryThe properties of poly(ethylene glycol) 20M (PEG 20M) on the silanized surface of Chromosorb W HMDS were investigated. It was found that the surface layer of PEG 20M is in a liquid form below its melting temperature. It the stationary phase loading ratio is above 0.105 the main retention mechanism is partition in both the liquid and solid forms of PEG 20M. The contribution of adsorption to the retention volume was also determined. It is suggested that in the case of methanol this contribution is caused by adsorption on the residual silanol groups present on the support surface whereas for n-octane this is rather adsorption on the gas-liquid interface.

DTA investigations of n-octadecanol films on complex carbon-silica adsorbents as a method for determination of their surface properties

SummaryThe properties of n-octadecanol films on complex carbonsilica adsorbents were investigated. It was found that two forms of oriented surface film exist on Carbosil surface. The structure of each form of the film distinctly depends on the nature of the surface patches of Carbosil. It was shown, using differential thermal analysis that it is possible to determine the ratio of carbonized and hydroxylated parts of the Carbosil surface.