Electroreduction of Pd(II) Complexes with α-Alanine on a Palladium Electrode

The kinetics of electroreduction of Pd(II) complexes with <img src="/content/l765605h27720278/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-alanine, Pd(ala)<sub>2</sub>, is studied on a rotating Pd disk electrode in solutions of pH 8–13 containing large excess of <img src="/content/l765605h27720278/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-alanine and various supporting electrolytes (NaF, Na<sub>2</sub>SO<sub>4</sub>, NaClO<sub>4</sub>). On a Pd electrode, complexes Pd(ala)<sub>2</sub> undergo reduction at potentials much more negative than on an Hg electrode. This is attributed to the chemisorption of water on the Pd electrode, which hampers adsorption of Pd(ala)<sub>2</sub> that take part in the slow electrochemical stage. As with the Hg electrode, perchlorate ions hinder the Pd(ala)<sub>2</sub> reduction on a Pd electrode. Studying adsorption of Pd(ala)<sub>2</sub> on a Pd electrode is hampered by parallel processes of hydrogen adsorption and absorption.     

Determination of methylated dibenzothiophenes in environmental sarnples by on-line HPLC-CGC

Concurrent solvent evaporation with a loop-type interface was used for on-line HPLC-CGC in the analysis of methylated dibenzothiophene (DBT) isomers in oil samples. The chromatographic behavior of 20 methyl DBT's was studied by HPLC on an aminopropylsilane DBTA phase and by GC on a selective methyl-phenylsilicone phase. That provided a method for analyzing by GC-flame photometric detection, the individual components of the DBT family, previously picked out of the crude oil matrix by HPLC. The GC oven temperature was shown to be critical during HPLC eluent introduction into the GC pre-column. Too high a temperature induced a severe broadening of early eluted peaks whereas a temperature too close to the boiling point of the liquid at the inlet pressure induced double peaks. Optimized conditions were retained on this basis and may be used for the analysis of other families of polyaromatic hydrocarbons.     

Calculation of harmonic force constants,vibrational frequencies and integrated intensities of some organic molecules using the MINDO—Forces method

The harmonic force constants, vibrational frequencies and integrated intensity ratios of CH<sub>2</sub>, H<sub>2</sub>O, CH<sub>2</sub>O, C<sub>2</sub>H<sub>2</sub>, CO<sub>2</sub>, HCN, CH<sub>3</sub>, CH<sub>4</sub>, and C<sub>2</sub>H<sub>4</sub> have been calculated using the MINDO—FORCES program and the Pulay method for the calculation of the molecular force constants. The results obtained are in general quite satisfactory when compared with available literature values. The results are, however, not as satisfactory in case of molecules containing heteroatoms, due to the neglect of some dipolar repulsion integrals for the heteroatoms by the MINDO/3 method. Calculated integrated intensities for CH<sub>3</sub> and C<sub>2</sub>H<sub>4</sub> agree well with experimental results. The calculated integrated intensities for other molecules are obtained for the first time and no comparison with published data is therefore possible.Part of the M.Sc. Thesis of K. H. A. 1978.     

Molecule-Responsive Fluorescent Sensors of α-Helix Peptides Bearing α-Cyclodextrin, Pyrene and Nitrobenzene Units in Their Side Chains

<img src="/content/m324377122mp878l/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-Helix peptides bearing one unit of <img src="/content/m324377122mp878l/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-cyclodextrin (<img src="/content/m324377122mp878l/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-CD), one unit of pyrene and one unit of nitrobenzene (NB) in their side chains have been designed and synthesized as novel molecule-responsive devices.In both the CD-peptides, <b><img src="/content/m324377122mp878l/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0"></b> <b>-PR17</b> and <b><img src="/content/m324377122mp878l/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0"></b> <b>-PL17</b>, the NB unit is separated from the CD unit by two turns of the helix. Two reference peptides (<b>PL17</b>, and <b>-P17</b>,) have also been synthesized. The circular dichroism studies in the peptide absorption region (200–250 nm)of <b><img src="/content/m324377122mp878l/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0"></b> <b>-PR17</b> and <b><img src="/content/m324377122mp878l/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0"></b> <b>-PL17</b> suggestthat the CD-peptides form stable<img src="/content/m324377122mp878l/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-helixstructures (83–77%), which was destabilized by accommodating guest molecules (e.g., <i>n</i>-pentanol) into the CD cavity. It suggests that formation of intramolecular host–guest(CD–NB) complex stabilized thehelical structure and exogenous guest molecule excluded the appending NB moiety from inside to outside of the CD cavity, thereby causing destabilization of the helical structure and increasing the random coil content. The ICD spectra of the peptides in the pyrene and nitrobenzene absorption region (250–40 nm) suggest that NB forms inclusion complex with CD. The fluorescence studies revealed that the fluorescence of the pyrene unit is quenched by the NB unit in <b><img src="/content/m324377122mp878l/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0"></b> <b>-PR17</b> and <b><img src="/content/m324377122mp878l/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0"></b> <b>-PL17</b>. The fluorescence intensity increases with increasing guest concentration for the CD-peptides.This guest-responsiveenhancement in the fluorescence intensity can be explained in terms of increased distance between the pyrene and NB moieties, which is caused by exclusion of the NB moiety from the CD cavity by guest accommodation. Using the guest-responsive fluorescence quenching properties of the CD-peptides, we have obtained binding constants for various short chain alkanols.<b><img src="/content/m324377122mp878l/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0"></b> <b>-PL17</b> has higher binding affinity to the guest molecules than its isomer, <b><img src="/content/m324377122mp878l/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0"></b> <b>-PR17</b>, indicating that the location of functional groups on the peptide scaffold is important in molecule detection.     

Preparation and characterization of theβ-cyclodextrin inclusion complex with sulfafurazole

The 1 : 1 inclusion complex involving sulfafurazole (SF) and<i><img src="/content/l3m2m67387h07724/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0"></i>-cyclodextrin (<img src="/content/l3m2m67387h07724/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-CD) is prepared by the freeze-drying method and characterized on the basis of its chemical analysis, thermal behavior, infrared spectrum, X-ray powder pattern and<sup>13</sup>C NMR spectrum in DMSO-d<sub>6</sub> solution. The stability constant of the inclusion complex was determined by the solubility method. The effect of cyclodextrin on the UV absorption spectrum of sulfafurazole was also observed.     

Synthesis of phosphorus (silicon,tin)-containing derivatives of mercaptoketenes and some of their properties

Some new<i>S</i>-phosphorylated,<i>S</i>-silylated, and<i>S</i>-stannylated derivatives of <img src="/content/l471457556572830/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-mercaptoketones were obtained. The reactions of some of these compounds induced by the temperature and by molecular oxygen as well as the phosphorylation of the Si- and Sn-containing derivatives were studied.Translated from<i>Izvestiya Akademii Nauk. Seriya Khimicheskaya</i>, No. 2, pp. 353–357, February, 1995.     

Alkylation of cyclododecanone with α,ω-dibromoalkanes under conditions of phase-transfer catalysis

Alkylation of cyclododecanone with <img src="/content/l72010208527l674/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">,<img src="/content/l72010208527l674/xxlarge969.gif" alt="ohgr" align="BASELINE" BORDER="0">-dibromoalkanes Br(CH)<sub> <i>n</i> </sub>Br (<i>n</i>=3, 4, 5) under conditions of phase-transfer catalysis in the presence of KOH results in the formation of either bicyclic ketones for<i>n</i>=3 and 5 or a mixture of bicyclic and spirocyclic ketones for<i>n</i>=4.Translated from<i>Izvestiya Akademii Nauk. Seriya Khimicheskaya</i>, No. 8, pp. 1436–1438, August, 1994.     

On the electrostatic and steric similarity of lactam compounds and the natural substrate for bacterial cell-wall biosynthesis

Summary Electrostatic and structural properties of a set of <img src="/content/tj0624125l838q67/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-lactam, <img src="/content/tj0624125l838q67/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0">-lactam and nonlactam compounds have been analyzed and compared with those of a model of the natural substrate <small>d</small>-alanyl-<small>d</small>-alanine for the carboxy- and transpeptidase enzymes. This first comparison of the electrostatic properties has been based on a distributed multipole analysis of high-quality ab initio wave functions of the substrate and potential antibiotics. The electrostatic similarity of the substrate and active compounds is apparent, and contrasts with the electrostatic properties of the noninhibitors. This has been quantified to give a reasonable correlation with the MIC (Minimum Concentration for Inhibition) and with kinetic data (k<sub>2</sub>/K) in accordance with the model for interaction of the lactam compounds with <small>dd</small>-peptidase. These correlations provide a better prediction of antibacterial activity than purely structural criteria.     

Direct and stepwise intercalation of alkylalcohols intoα-zirconium phosphate

Intercalation of alkylalcohols into <img src="/content/l492p76141t7k517/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-zirconium phosphate was investigated at 25°C and/or under reflux.<i>n</i>-Alcohols having two to five carbons and 2-propanol were taken up at 25°C. These alcohols, and<i>n</i>-hexanol and heptanol, also intercalated under reflux.<i>n</i>-Alcohols having eight to eighteen carbon atoms intercalated when a stepwise method was employed. 2-Butanol and tertiary amylalcohols intercalated under reflux using a butanol intercalate as a starting material. Ethanol-to-butanol intercalates were unstable at room temperature, losing alcohols and changing to <img src="/content/l492p76141t7k517/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-zirconium phosphate. The particle size of the <img src="/content/l492p76141t7k517/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-zirconium phosphate did not affect the intercalation of alcohols.