Elimination of hydrophobic

Gobas, F. A.P.C., D.C.G. Muir, and D. Mackay. 1989. Dynamics of Dietary Bioaccumulation and Faecal Elimination of Hydrophobic Organic Chemicals in Fish. Chemosphere 17, 943-962. 

Belfroid, A., van den Berg, M., Seinen, W., Hermens, J. van Gestel, K. (1995) Uptake, bioavailability and elimination of hydrophobic compounds in earthworms (Eisenia andrei) in field-contaminated soil. Environ. Toxicol. Chem. 14, 605-612. 

Gobas FAPC, Muir DCG, Mackay D. 1988. Dynamics of dietary bioaccumulation and faecal elimination of hydrophobic organic chemicals in fish. Chemosphere 17 943-962. 

The same strategy - artificial alkalization or acidification of the urine - is quite commonly employed in the clinical treatment of poisonings. However, if the poison (drug) is neither acidic nor basic, the only option is to increase the urine volume. In this case, the amount of the drug (assuming it to be membrane-permeant, as many are) eliminated will simply be proportional to the volume of urine produced. This strategy is called forced diuresis . Another, more effective but also more involved method for the accelerated elimination of hydrophobic drugs such as barbi-... 

A reliable chromatographic method has been developed for the quantitative aneilysis of hydrophobic impurities in water-soluble polymeric dyes. The method utilizes both the molecular sieve effect of normal gel permeation chromatography and solute-column packing interaction, modified by solvent composition. This method eliminates the need to extract the impurities from the polymeric dye with 100 extraction efficiency, as would be required for an ordinary liquid chromatographic analysis. 

Hydrophobic interactions, on the other hand, are strong, indifferent to local details, and are relatively long range. If transient direct or water-separated contacts occur between nonpolar side chains, the net effect could be local organization and an overall compaction of the polypeptide chain. Whereas the strengths of hydrophobic interactions must be considerably reduced in 8 M urea, they clearly are not eliminated, as evidenced by the persistence of lipid bicelles. Thus hydrophobic interactions probably play some role in persistent global structure, the importance of which can be tested by replacing multiple hydrophobic side chains with similarly shaped polar ones. 

Uncharged oligos appear to enter the cell by passive diffusion, as well as possibly by endocytosis. However, elimination of the charges renders the resultant oligos relatively hydrophobic, thus generating additional difficulties with their synthesis and delivery. 

Murakami and Kondo (1975) reported that the cationic micelle is quite effective for the pyridoxal-catalyzed elimination of S-phenylcysteine. The significant rate acceleration was explained by the binding of the Schiff s base to the micelle phase, followed by the efficient proton abstraction by hydroxide ion at the micelle surface. According to Gani et al. (1978), mixed micelles of CTAB and dodecylamine hydrochloride are good models for the site accommodating pyridoxal 5 -phosphate in glycogen phosphorylase, since the micelles can imitate well the formation of SchifT s bases in hydrophobic environments. 

Pristine CNTs are hydrophobic and cause a lack of solubility in biological aqueous fluids such as blood. The poor solubility of CNTs in blood stream poses a major challenge to in vivo studies making behavior of CNTs difficult to predict and control (Kam et al., 2005 Zheng et al., 2003a, b). Therefore, modification of CNT surface to introduce hydrophilic, functional groups has been utilized in pharmaceutical applications (Lacerda et al., 2006). However, insufficient in vivo evaluation of both pristine and surface-modified CNTs has been performed to answer essential questions on CNT toxicology. Additional in vivo studies also required to devise the best method of administration, means of uptake, metabolism, and elimination of CNTs. The in vivo studies on CNTs performed to date are presented in Table 12.2. 

The major anions and cations in seawater have a significant influence on most analytical protocols used to determine trace metals at low concentrations, so production of reference materials in seawater is absolutely essential. The major ions interfere strongly with metal analysis using graphite furnace atomic absorption spectroscopy (GFAAS) and inductively coupled plasma mass spectroscopy (ICP-MS) and must be eliminated. Consequently, preconcentration techniques used to lower detection limits must also exclude these elements. Techniques based on solvent extraction of hydrophobic chelates and column preconcentration using Chelex 100 achieve these objectives and have been widely used with GFAAS. 

Fats and oils are hydrophobic, water-insoluble substances. The operational difference between them is simple fats are solid at room temperature oils are liquid at room temperature. Chemically, fats and oils are triglycerides, triesters formed from glycerol and three fatty acids. Let me remind you that an ester is a functional group derived by linking a carboxylic acid to an alcohol, with the elimination of a molecule of water ... 

The hydrophobic interior of the phospholipid membrane constitutes a diffusion barrier virtually impermeable for charged particles. Apolar particles, however, penetrate the membrane easily. This is of major importance with respect to the absorption, distribution, and elimination of drugs. 

Adsorption. Hydrophobic interactions, which may occur using aqueous mobile phases, usually can be eliminated by the addition of an organic modifier to the aqueous mobile phase (30,33) or by a reduction of ionic strength (3A 25.)- Recently, Haglund and Marsden (36-AO) have undertaken a systematic study on the chromatographic behavior of low molecular weight solutes on Sephadex packings and explained these results in terms of hydrophobic interactions. 

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