Surfactant amino acid analyses

To obtain data on the heterogeneity of the glycopeptide fraction of microbubble surfactant, comparative amino acid analyses were performed on two of the major peaks obtained from gel filtration. From the ratio of absorbances at 230 and 280 nm (ref. 265) and the elution profile shown in Fig. 5.3, it appeared that peaks I and III would differ the most in amino acid composition and, therefore, these two peaks were selected for amino acid analysis. Peak I was sufficiently large to be divided into three equal aliquots and peak III into two equal aliquots for automated analysis. Peak II, which eluted closest (Fig. 5.3) to the dominant peak I and presumably was most similar in molecular composition to this large initial peak, was analyzed separately by HPLC for carbohydrate content. 

CE has been applied extensively for the separation of chiral compounds in chemical and pharmaceutical analysis.First chiral separations were reported by Gozel et al. who separated the enantiomers of some dansylated amino acids by using diastereomeric complex formation with Cu " -aspartame. Later, Tran et al. demonstrated that such a separation was also possible by derivatization of amino acids with L-Marfey s reagent. Nishi et al. were able to separate some chiral pharmaceutical compounds by using bile salts as chiral selectors and as micellar surfactants. However, it was not until Fanali first showed the utilization of cyclodextrins as chiral selectors that a boom in the number of applications was noted. Cyclodextrins are added to the buffer electrolyte and a chiral recognition may... 

A few years ago, we began a research program to develop methods of analysis which would involve the use of FAB and a high performance tandem mass spectrometer. The tandem instrument was the first triple sector mass spectrometer to be designed and built by a commercial instrument company (Kratos of Manchester, U.K.). The first mass spectrometer of the combination is a double focussing Kratos MS-50 which is coupled to a low resolution electrostatic analyzer, which serves as the second mass spectrometer U). This FAB MS-MS combination has been used to verify the structures of an unknown cyclic peptide (2), a new amino acid modified by diphtheria toxin (3), and an ornithine-containing lipid (4). A number of methods have also been worked out which rely on this instrumentation. They Include the structural determination of cyclic peptides (5), nucleosides and nucleotides (6), and unsaturated fatty acids (7) and the analysis of mixtures of both anionic (8) and cationic surfactants (9). 

In this chapter we introduce compounds which have been successfully applied in the construction of supramolecular assemblies. Only the amphiphiles which have been prepared in sufficient quantities have been admitted milligram quantities being considered unacceptable as starting materials for the preparation, analysis and application of assemblies. Experience proves that complicated dyes, pore builders, receptors etc. never reappear in the literature after their syntheses and spectroscopic properties have been reported. On the other hand, such easily attainable synkinons and surfactants around the ten gram scale need not, of course, be too simple. On the contrary, they may contain all the components of the chiral pool, i.e. amino acids, carbohydrates, steroids etc., as well as all commercial dyes of interest such as protoporphyrin, phthalo-cyanines, carotenes, viologen and quinones. 

Tryptophan In order to focus on the role of surfactant on solubilization, we chose to study an ionic solute which is insoluble in ethane, even when doped with several percent octanol. Amino acids, which are hydrophilic zwitterions, are not soluble in ethane and other hydrocarbons. Tryptophan was selected because its strong chromophore simplified analysis. At 37 C, its solubility is below the detection limit, 0.2mM, in a solution of 6 mole % octanol in ethane at 325 bar. 

Numerous other protein-surfactant systems when subjected to Scatchard analysis give curves that extrapolate to a number of specific binding sites very close to the number of cationic amino acid residues in the protein. Furthermore, chemical modification of the cationic sites, e.g., in the case of lysyl residues by acetylation, shifts the Scatchard plots to give lower values of n [32], Despite these interesting observations, Scatchard analysis should be treated with a degree of caution it is not entirely clear why such a good correspondence between n and the number of cationic sites is obtained, since the binding sites must only approximate to independence and are certainly not chemically identical. 

Most of these applications are in the area of water analysis for the determination of various pesticides, carboxylic and amino acids, aromatic compounds, surfactants, aniline derivatives, and metal ions. There are a few applications of SL membranes in soil and air analysis of carboxylic acids (Table 1). 

As in the case of FAB-MS, the use of surfactants such as cetyltrimethylammonium bromide (CTAB) can be used to substantially or even completely suppress the matrix-related ion background [81]. Use of the CTAB surfactant also resulted in an improved mass resolution for low-molecular-weight molecules including amino acids, peptides, drugs, and cyclodextrins. This technique has been used successfully for the analysis of caffeine, and the vitamins riboflavin, nicotinamide and pyridoxine in various energy drinks [82]. 

Like ELSD, CAD has been applied for the analysis of nonvolatile neutral, acidic, basic, and zwitterionic compounds, both polar and nonpolar. Compound classes include amino acids, fatty acids, carbohydrates, lipids, proteins, steroids, surfactants, and other compounds with weak or no chromophores used in the pharmaceutical, food, chemical, and consumer products industries. Some applications involving ionic and polar species are described below. 

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