Shaping Solid-State Supramolecular Cavities: Chemically Induced Accordionlike Movement of gamma-Zirconium Phosphate Containing Polyethylenoxide Pillars

The hydrophilic oxygen atoms of polyethylenoxide chains inserted as pillars in gamma-zirconium phosphate form hydrogen bonds with the acid groups of the host. As a result the pillars are almost perpendicular to the gamma layers. Upon changing the pH level of the supernatant solution the hydrogen bonds are broken and the pillars become almost perpendicular to the layers (shown schematically). Thus there is a reversible enlargement-shortening of the interlayer space.     

Separation of Tetracycline Antibiotics by Hydrophilic Interaction Chromatography Using an Amino-Propyl Stationary Phase

In this work the potential of hydrophilic interaction chromatography (HILIC) is explored for the analysis of tetracycline antibiotics. The choice of the polar stationary phase is first discussed and it is demonstrated that aminopropyl stationary phases lead to higher efficiencies and peak symmetry than bare silica ones. The influence of the composition of the mobile phase is studied next : the concentration of the weaker solvent (acetonitrile), the nature and concentration of the more polar solvent (water or methanol), pH, the nature and ionic strength of the buffer. It is shown that high efficiencies are reached only with a citrate buffer that impairs the interactions with the residual silanol groups whatever the mobile phase pH is. We demonstrate that the citrate buffer strongly interacts with the cationic moiety of the aminopropyl stationary phase and thus reduces the accessibility of silanols. The separation of oxytetracycline, tetracycline and chlortetracycline is achieved in a few minutes at pH 3.5 or 5, with no peak tailing as usually observed in reversed phase liquid chromatography with an opposite elution order when compared with reversed phase liquid chromatography.     

Synthesis of some dibenzodiazepinone derivatives as potent and m2-selective antimuscarinic compounds

Two series of 5-[[4-[4-(dialkylamino)butyl]-l-cyclohexyl]acetyl], and 5-[(dialkylamino)acyl]-10,11-dihydro-5H- dibenzo[b,e][1,4]diazepin-11-ones were synthesized as potential m2-selective ligands 1,2. Their affinity and selectivity for the muscarinic cholinergic receptor m-AChR subtypes were determined. Replacing a nitrogen with CH in the piperidine ring of 5-[[4-[4-(dialkylamino)butyl]-l-piperidinyl]acetyl]-10,11-dihydro-5H-dibenzo-[b,e][1,4]diazepin-11-ones 3 significantly altered the affinity and selectivity to the muscarinic receptor subtypes.     

Optimization of culture medium and conditions for penicillin acylase production by Streptomyces lavendulae ATCC 13664

The culture medium for Streptomyces lavendulae ATCC 13664 was optimized on a shake-flask scale by using a statistical factorial design for enhanced production of penicillin acylase. This extracellular enzyme recently has been reported to be a penicillin K acylase, presenting also high hydrolytic activity against penicillin V and other natural aliphatic penicillins such as penicillin K, penicillin F, and penicillin dihydroF. The factorial design indicated that the main factors that positively affect penicillin acylase production by S. lavendulae were the concentration of yeast extract and the presence of oligoelements in the fermentation medium, whereas the presence of olive oil in the medium had no effect on enzyme production. An initial concentration of 2.5% (w/v) yeast extract and 3 microg/mL of CuSO4 x 5H2O was found to be best for acylase production. In such optimized culture medium, fermentation of the microorganism yielded 289 IU/L of enzyme in 72 h when employing a volume medium/volume flask ratio of 0.4 and a 300-rpm shaking speed. The presence of copper, alone and in combination with other metals, stimulated biomass as well as penicillin acylase production. The time course of penicillin acylase production was also studied in the optimized medium and conditions. Enzyme production showed catabolite repression by different carbon sources such as glucose, lactose, citrate, glycerol, and glycine.     

Integrated production of ethanol fuel and protein from Coastal Bermudagrass

The herbaceous crops that may provide fermentable carbohydrates for production of fuels and chemicals also contain 10–20% protein. Protein coproduction with biomass-derived fuels and chemicals has important advantages: (1) food and fuel production can be integrated, and (2) protein is a high-value product that may significantly improve overall process economics. We report the results of an integrated approach to producing protein and fermentable sugars from one herbaceous species, Coastal Bermudagrass (CBG). The ammonia fiber explosion (AFEX) process makes possible over 90% conversion of cellulose and hemicellulose to simple sugars (about 650 mg reducing sugars/g dry CBG) at 5 IU cellulase/g vs < 20% conversion for untreated CBG. The AFEX treatment also improves protein extraction from CBG; over 80% protein recovery is possible from AFEX-treated CBG vs about 30% recovery from untreated CBG.     

Use of a55Fe radioisotope for the determination of titanium in laterite samples via energy dispersive X-ray fluorescence

A rapid method for the determination of titanium in geochemical samples using a⁵⁵Fe radioisotope as the extraction source coupled to a Si(Li) detector and a PDP-11.05 computer is described. The relative standard deviation for a thin sample about 100 mg in weight is less than 4% and it is achieved in a fluorescent time of 100 sec. Data are given for the use of two different internal standards, KBrO₃ and K₂Cr₂O₇, the latter being more precise. The values for five international reference standards are in agreement for this method with the reported values. Finally, besides being rapid, no hydrofluoric acid dissolution of fusion is necessary as in atomic absorption and classical methods. This paper was presented at the XX Colloquium Spectroscopium Internationale, 8 Aug.–7. Sept. 1977, Prague, Czechoslovakia.     

Determination of diethanolamine or <Emphasis Type="Italic">N</Emphasis>-methyldiethanolamine in high ammonium concentration matrices by capillary electrophoresis with indirect UV detection: application to the analysis of refinery process waters

Alkanolamines such as diethanolamine (DEA) and N-methyldiethanolamine (MDEA) are used in desulfurization processes in crude oil refineries. These compounds may be found in process waters following an accidental contamination. The analysis of alkanolamines in refinery process waters is very difficult due to the high ammonium concentration of the samples. This paper describes a method for the determination of DEA in high ammonium concentration refinery process waters by using capillary electrophoresis (CE) with indirect UV detection. The same method can be used for the determination of MDEA. Best results were achieved with a background electrolyte (BGE) comprising 10 mM histidine adjusted to pH 5.0 with acetic acid. The development of this electrolyte and the analytical performances are discussed. The quantification was performed by using internal standardization, by which triethanolamine (TEA) was used as internal standard. A matrix effect due to the high ammonium content has been highlighted and standard addition was therefore used. The developed method was characterized in terms of repeatability of migration times and corrected peak areas, linearity, and accuracy. Limits of detection (LODs) and quantification (LOQs) obtained were 0.2 and 0.7 ppm, respectively. The CE method was applied to the determination of DEA or MDEA in refinery process waters spiked with known amounts of analytes and it gave excellent results, since uncertainties obtained were 8 and 5%, respectively.     

Comparison of tryptophan interactions to free and grafted BSA protein

The binding of d- and l-tryptophan molecules to bovine serum albumin (BSA) protein has been studied using liquid chromatography and ultrafiltration in the pH range from 7 to 11. A hydrophobic interaction between tryptophan and BSA has been observed at pH 7.0 on BSA grafted chromatographic column. However, this interaction is negligible at higher pH for which the interaction to the stereospecific site was predominant. For both grafted and free proteins, the complexation mechanism was a competitive binding of d- and l-enantiomers on a single site. The apparent complexation constants for both d- and l-tryptophan show a maximum in the pH range 9-10. The variations of the apparent complexation constants versus pH were the result of the protonation of both the amino acid and a single site of the protein assuming that the complexation occurs between the zwitter-ionic amino acid form and the unprotonated BSA site. The apparent pK(BSA) is slightly shifted from 8.3 for grafted BSA protein to 9.4 for free BSA protein. This shift is presumably as a result of the different protein conformation.     

Interactions between octyl-β-D-glucoside and α-amino acids or small peptides

The interactions between octyl--D-glucoside and glycine in water have been investigated by surface tension, viscosity, and density measurements. The results show that the -amino acid causes an unexpected lowering of the critical micellar concentration of octyl--D-glucoside. Such a finding has been interpreted in temss of dipole-dipole interactions between the hydrophilic site of the surfactant and the peptidic cosluttes. From three to seven amino acid molecules have been estimated to be coordinated with each glucoside unity in the micellar state. The research has been extended to glycine oligopeptides and L-lysine. The latter compound has effects similar to those observed with glycine whereas diglycine and triglycine show weaker effects on the micellization process.     

Bioelectrochemical determination of lactic and malic acids in wine

Electroanalytical methods based on biosensor technology and differential pH measurement for the determination of l-lactic and l-malic acids in wine were developed. Lactic acid was determined according to two procedures consisting of the use of two lactate electrochemical biosensors, one based on a Clark O(2) probe and the other based on the H(2)O(2) probe. The two probes were assembled employing a polymeric membrane where the enzyme lactate oxidase was previously immobilized. Both sensors exhibited high storage and operational stabilities, and good reproducibility when used in wine matrix. Measurement of lactate was carried out using two different flow-through cells assembled with the lactate probes. The low detection limit of these probes and the relatively high concentration of lactate in wine samples required a serial dilution in the range 1:100 to 1:200, thus eliminating all potential electrochemical or enzyme interferences present in the sample. Malic acid was determined using a differential commercially available pH-meter and an enzymatic procedure. For this analysis, we employed the malic enzyme (EC 1.1.1.40) and the NADP(+) cofactor. The pH variation due to the action of this enzyme on malic acid was found to be proportional to the malic acid present in the sample. Experimental parameters such as pH, temperature, and co-factor concentration were optimized, resulting in malate determination in less than 1 min with good reproducibility. Various samples of wine and wine musts were assayed for lactate with the two biosensor procedures, and for malate with differential pH-metry. The results when compared with those obtained with the commonly used spectrophotometric procedure correlated well.