In this work the suitability of selected commercially available hyperbranched polymers and ionic liquids as entrainers for the extractive distillation and as extraction solvents for the liquid–liquid extraction is investigated. Based on thermodynamic studies on the influence of hyperbranched polymers and ionic liquids on the vapor–liquid and liquid–liquid equilibrium of the azeotropic ethanol–water and THF–water systems, process simulations are carried out, which allow evaluating the potential of hyperbranched polymers and ionic liquids as selective components for the mentioned applications in terms of feasibility and energetic efficiency. Both hyperbranched polymers and ionic liquids break a variety of azeotropic systems. Since their selectivity, capacity, viscosity, and thermal stability can be customized, they appear superior to many conventional entrainers and extraction solvents. For the ethanol–water separation, the nonvolatile substances hyperbranched polyglycerol and [EMIM]+[BF4]− show a remarkable entrainer performance and therefore enable extractive distillation processes, which require less energy than the conventional process using 1,2‐ethanediol as an entrainer. Evaluation of a new THF–water separation process indicates the competitiveness of the suggested process and a considerable potential of using hyperbranched polymers as extraction solvents. © 2004 American Institute of Chemical Engineers AIChE J 50: 2439–2454, 2004

Mohs' chemosurgery, with its complete microscopic control, is the most reliable procedure in achieving complete ablation of basal‐cell epitheliomas on the face. By utilizing this method, we compared basal‐cell epitheliomas treated by histographic surgery both as to the clinically estimated extension and as to the actual size of the defect resulting from complete tumor removal. This paper deals with the question of how broad a margin of normal tissue should be included in the excision of tumors of varying sizes.

The distribution of the phytohormone, abscisic acid (ABA), within the phylum ofPhycophyta was investigated by an enzyme-linked immunoassay (ELISA). Of 64 algal species tested (originating from 9 divisions, 20 classes and 36 orders, including procaryotes) all species contained ABA, whereas no ABA could be detected in the bacteria Escherichia coli, Rhodospirilhm rubrum, and Halobacterium halobium. It is concluded that ABA is universally distributed within the algal kingdom and is not restricted to cormophytes. The ability to synthesize ABA must have been developed even within the procaryotes. The physiological role of ABA in some selected algae was studied by investigating 1. the distribution of ABA between the cells and the culture medium, 2. the responses of endogenous ABA to stress, 3. the synthesis of 14C-ABA from externally applied ''C-mevalonic acid, 4. the metabolism of ABA, 5. the effect of externally applied ABA on various physiological reactions of the algae, and the effect of norflurazon on ABA content. ''C-mevalonic acid served as precursor of 14C-ABA synthesis in Dunaliella cells and ABA was metabolised to the same products which have been observed in higher plants. In D. parva the internal ABA level increased upon hyperosmotic salt shocks, and in D. acidophila upon alkalization of the medium. Norflurazon caused an increase of ABA content in Dunaliella. Externally applied ABA did not affect photosynthesis, respiration and K' content of the cells. The permeability of the plasma membrane of D. acidophila to water was slightly decreased by ABA. The possible physiological function of ABA in algae is discussed.Botanica Acta 102 (1989) 326-334 -

Our results indicate an additional benefit of this specific therapeutic intervention for older depressed patients.

By following the tryptophan fluorescence of yeast seryl-tRNA synthetase on additition of tRNASer it was observed that the number of binding sites for tRNA decreases from two to one with increasing temperature, ATP or KCl concentration. Concomitantly a considerable decrease of the apparent binding constant was observed. The variation in the number of binding sites is explained by the presence of at least one temperature and ionic strength sensitive binding site and one temperature and ionic strength independent binding site.Relaxation kinetic experiments revealed two binding processes : a fast one depending on tRNA concentration and ionic strength and a slow one, which appeared to be independent of tRNA concentration and ionic strength. Enzyme kinetic studies showed that the activity of seryl-tRNA synthetase strongly depends on the KC1 concentration and exhibits a maximum at 0.2 M KCI. Based on the data from relaxation and enzyme kinetic experiments a model is suggested for the recognition process involving a first unspecific step where all tRNAs, cognate and non-cognate, are bound to the synthetase (scanning step). The identification of the cognate tRNA is then performed at the recognition site by a conformational transition of the tRNA . synthetase complex (identification step).The interactions of aminoacyl-tRNA synthetases with their cognate tRNAs are specificity-determining steps in protein synthesis [l -41. In a number of studies the binding of tRNASer to seryl-tRNA synthetase was investigated [5-131. In most publications the binding of two tRNA molecules per synthetase molecule was reported [5-121. But also a ratio of 1 : 1 was determined 1131. Even more than two binding sites for tRNASer on seryl-tRNA synthetase were deduced from fluorimetric titrations at low pH [9] and, for heterologous tRNAS" in the absence of ATP [lo]. It was also observed that the stoichiometric relations varied between one and two depending on temperature, salt conditions and enzyme concentration [6,9]. In the present publication results of a systematic study of the influence of conditions on the stoichiometry and binding constants in this system are reported. These results and those from

No abstract

The interactions of yeast seryl-tRNA and phenylalanyl-tRNA synthetases with the cognate and the noncognate tRNA have been studied by fluorescence spectroscopy. The binding process was followed by observing the changes in tryptophan fluorescence of the synthetases as well as the changes in the polarized fluorescence of the tRNAs covalently labeled with ethidium bromide, proflavine, or l,N6-etheno-ATP. The degree of polarization of the fluorescence labels is particularly sensitive to changes in rotational diffusion of the tRNA. Both methods can be regarded as complementary and gave comparable results. There exist, however, cases such as the interaction between seryl-tRNA synthetase and tRNASer in the absence of Mg2+, where the binding process could only be detected by measurement of the fluorescence polarization.Unspecific interactions between synthetases and tRNAs (or tRNA-dye compounds) could be detected and were found to be highly dependent on pH, salt concentration and on the buffer used. I n potassium phosphate buffer pH 7.3 discrimination between cognate and noncognate tRNA by seryl-tRNA synthetase increases with addition of salt. The tryptophan fluorescence of phenylalanyl-tRNA synthetase was influenced differently by the cognate and the noncognate tRNA while the stabilities of the complexes between this synthetase and the ethidium-labeled tRNAPhe and tRNASer were rather similar. Seryl-tRNA synthetase apparently discriminates more efficiently than phenylalanyl-tRNA synthetase between the cognate and the noncognate tRNAs.The presence of two binding sites on seryl-tRNA synthetase and the presence of one binding site on phenylalanyl-tRNA synthetase for cognate as well as noncognate tRNA could be deduced. For the specific interaction between tRNASer and seryl-tRNA synthetase in the presence of Mg2+ indications for cooperative behavior have been found. Experiments on competition between noncognate and cognate tRNAs as well as tRNA half molecules for the binding to the synthetase indicate an overlap of specific and unspecific binding sites.We conclude that the unspecific interaction may be an important initial step preceding the specific binding and recognition of the tRNA by the synthetase. Enzymes. Seryl-tRNA synthetase (EC 6.1.1.11); phenylalanyl-tRNA synthetase (EC 6.1.1.-); CC14-transferase (EC 2.7.7.25).The interactions of tRNAs with their cognate aminoacyl-tRNA synthetases are specificity-determining steps in protein biosynthesis. These interactions have been studied by a number of methods (for summaries see . The fluorescence of tryptophan residues of the synthetases has been used to investigate the equilibria [4-10] and kinetics [6] of the interactions. I n addition to the specific binding, interactions between synthetases and noncognate tRNAs have been observed [6,7,9]. A principal difficulty in the interpretation of the tryptophan fluorescence lies in the fact that the presently known Em.

Our results indicate the efficacy of this specific therapeutic intervention for older depressed patients.