Tolerance to solvents

The greatest advance in the analysis of peptides has been the coupling with spectrometric techniques, both for identification and for characterization. Their high accuracy, sensitivity, and, in some instances, tolerance to solvents make mass spectrometers ideal detectors for analyses of HPLC-separated peptides. 

Polymer semiconductor materials which are soluble cannot tolerate exposure to solvents, which can cause them to swell and/or dissolve. Many oligomeric organic semiconductors are also not tolerant to solvent exposure, which complicates photolithography. Pentacene, for example, is not soluble to any significant degree in any solvents. When pentacene OFETs are exposed to most solvents, however, their semiconductor character is destroyed. 

Despite the general toxic effect of solvents to whole cells, some microbial strains present an unusual tolerance to solvents (e.g.. Pseudomonas [69, 71], Rhodococcus [72]). This may involve an adaptation mechanism at the level of the cytoplasmatic membrane, aiming to restore its stability and fluidity, once dis-... 

Lactobacillus High tolerance to solvent Less tractable... 

Fig. 5 Exploring protein fitness landscape by directed evolution to modify specificity or create new functions and modulating biophysical properties such as thermostability, tolerance to solvents, flexibility...

Volume ratio (ASTM D1720) of diluent to solvent that just fails to dissolve completely 8 g of nitrocellulose in 100 mL of solvent. The higher the dilution ratio, the mote diluent the solution tolerates. 

Similarly, for the analysis of polymers using high-temperature solvents, the important concern is column stability and durability. Eor this reason, 10-/am particles are the best column choice. Waters Styragel HT columns are designed for this kind of application. Similarly, these columns are also more tolerant to eluent changes. Therefore, these columns are also recommended... 

ADMET is quite possibly the most flexible transition-metal-catalyzed polymerization route known to date. With the introduction of new, functionality-tolerant robust catalysts, the primary limitation of this chemistry involves the synthesis and cost of the diene monomer that is used. ADMET gives the chemist a powerful tool for the synthesis of polymers not easily accessible via other means, and in this chapter, we designate the key elements of ADMET. We detail the synthetic techniques required to perform this reaction and discuss the wide range of properties observed from the variety of polymers that can be synthesized. For example, branched and functionalized polymers produced by this route provide excellent models (after quantitative hydrogenation) for the study of many large-volume commercial copolymers, and the synthesis of reactive carbosilane polymers provides a flexible route to solvent-resistant elastomers with variable properties. Telechelic oligomers can also be made which offer an excellent means for polymer modification or incorporation into block copolymers. All of these examples illustrate the versatility of ADMET. 

From tamarind seed xyloglucan, carboxymethyl derivatives with different levels of DS were prepared in isopropanol medium [440]. Swelling power, solubihty and tolerance to organic solvents of the derivatives increased with increasing DS. The interaction properties of the unmodified xyloglucan with calcium chloride and sodiiun tetraborate were found to be reversed upon car-boxymethylation. 

Tolerance is characterized by reduced responsiveness to the initial effects of a drug after repeated exposure or reduced responsiveness to a related compound (i.e., cross-tolerance). Animal studies have not provided conclusive evidence of tolerance to the effects of the centrally active compounds in toluene or trichloroethane (Moser and Balster 1981 Moser et al. 1985). Observations in humans, on the other hand, have documented pronounced tolerance among subjects who chronically inhale substances with high concentrations of toluene (Glaser and Massengale 1962 Press and Done 1967) and butane (Evans and Raistrick 1987). Kono et al. (2001) showed that tolerance to the reinforcing effects of solvents is comparable to that conditioned by nicotine but less intense than that reported with alcohol or methamphetamine use. 

Himnan DJ Tolerance and reverse tolerance to toluene inhalation effects on open-field behavior. Pharmacol Biochem Behav 21 625-631, 1984 Hinman DJ Biphasic dose-response relationship for effects of toluene inhalation on locomotor activity. Pharmacol Biochem Behav 26 65-69, 1987 Hormes JT, Filley CM, Rosenberg NL Neurologic sequelae of chronic solvent vapor abuse. Neurology 36 698—702, 1986... 

The development of biphasic media requires a knowledge of general rules based on observation. The choice of the biocatalyst and the organic solvent is very important. Estimation of the biocatalyst tolerance to an organic solvent is based on various indicators, described later in this chapter. Biocatalysts are also sensitive to the process of the liquid-liquid interface. They can be used in two different forms free, soluble or immobilized. 

Further work at EniTecnologies was conducted with Rhodococcus strains. Rhodococ-cus was selected for its metabolical versatility, easy availability in soils and water, and remarkable solvent tolerance. Its capabilities for catalyzing diverse transformation reactions of crude oils, such as sulfur removal, alkanes and aromatics oxidation and catabolism caught their attention. Hence, genetic tools for the engineering of Rhodococcus strains have been applied to improve its biotransformation performance and its tolerance to certain common contaminants of the crude oil, such as cadmium. The development of active biomolecules led to the isolation and characterization of plasmid vectors and promoters. Strains have been constructed in which the careful over-expression of selected components of the desulfurization pathway leads to the enhancement of the sulfur removal activity in model systems. Rhodococcus, Gordona, and Nocardia were transformed in this way trying to improve their catalytic performance in BDS. In a... 

Katsuki et al. have reported that high enantioselectivity can be obtained in the oxidation of nonconjugated cyclic enol ethers by using Mn(salen) (34) as the catalyst.138 The reactions were performed in an alcoholic solvent to obtain a-hydroxy acetals as the products, because a-hydroxy acetals are tolerant to a weak Lewis acid like Mn(salen) and do not racemize during the reaction and the isolation procedure (Scheme 29). 

Application in organic synthesis of pentacoordinated triorganodifluorosilicate anions, such as [Bu4N][Ph3SiF2] 825, have been extended to palladium(0)-catalyzed cross coupling reactions (solvents DMF, TFIF, dioxane) with arene halides (Scheme 111).825 This method is tolerant to various palladium(O) catalysts and provides excellent yields of mainly heterocoupled products and only small amounts of homocoupled byproducts. 

Nebulization is inefficient and therefore not appropriate for very small liquid samples. Introducing samples into the plasma in liquid form reduces the potential sensitivity because the analyte flux is limited by the amount of solvent that the plasma will tolerate. To circumvent these problems a variety of thermal and electrothermal vaporization devices have been investigated. Two basic approaches are in use. The first involves indirect vaporization of the sample in an electrothermal vaporizer, e.g. a carbon rod or tube furnace or heated metal filament as commonly used in atomic absorption spectrometry [7-9], The second involves inserting the sample into the base of the... 

Thermospray (TSP) [29-31] unites three modes of operation. In pure TSP, a solution of the analyte and a volatile buffer, usually 0.1 M ammonium acetate, is evaporated from a heated capillary at a flow rate of 1-2 ml min into a heated chamber, hence the term thermospray. As the solvent evaporates, the analyte is forming adducts with ions from the buffer salt. While most of the neutrals are removed by a vacuum pump, the ions are extracted orthogonally from their main axis of motion by use of an electrostatic potential. The ions are transferred into a quadrupole mass analyzer through a pinhole of about 25 pm in diameter (Fig. 11.2). The quadrupole was employed according to its tolerance to poor vac-... 

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