Amino acid surfactants general

Amino acid surfactants of the general structure (X-amino-(iV-acyl)-P-alkoypropionate. Y = log MIC X = log CMC. 

There are various synthetic routes to introduce hydrocarbon long chains into amino acid-based surfactants. For example, a long-chain fatty acyl group is introduced on the amino part of amino acids by using an acid chloride. To obtain amino acid esters or amides, the carbonyl parts of amino acids are reacted with fatty alcohol or amines, respectively. For example, C-alkylation of an amino acid is obtained by the reaction of a-bromo fatty acid with ammonia or by a transmission reaction of the amino part of the amino ester with a stable Schiff base followed by deprotonation with a strong base. This is followed by alkylation with an alkyl halide. N-Alkylation of an amino acid is generally obtained by the reaction of fatty amines with monochloroacetic acid, methyl acrylate, or maleic acid or by the addition of 1,2-epoxy alkane to amino acids. 

Anions and uncharged analytes tend to spend more time in the buffered solution and as a result their movement relates to this. While these are useful generalizations, various factors contribute to the migration order of the analytes. These include the anionic or cationic nature of the surfactant, the influence of electroendosmosis, the properties of the buffer, the contributions of electrostatic versus hydrophobic interactions and the electrophoretic mobility of the native analyte. In addition, organic modifiers, e.g. methanol, acetonitrile and tetrahydrofuran are used to enhance separations and these increase the affinity of the more hydrophobic analytes for the liquid rather than the micellar phase. The effect of chirality of the analyte on its interaction with the micelles is utilized to separate enantiomers that either are already present in a sample or have been chemically produced. Such pre-capillary derivatization has been used to produce chiral amino acids for capillary electrophoresis. An alternative approach to chiral separations is the incorporation of additives such as cyclodextrins in the buffer solution. 

The function of a surfactant depends on its hydrophilicity-lipo-philicity balance (HLB). Efficient emulsification of oil generally requires a low HLB, while the whipping characteristic arises at a larger HLB. This chapter is an attempt to prepare proteinaceous surfactants with different HLBs by the enzymatic attachment of amino acid esters with different lipophilicity. For this purpose L-leucine n-alkyl esters (Leu-OQ), the alkyl chain length, i, varying from 2 to 12, were used. As... 

Some of the amino acid side chains in proteins are hydrophobic, generally buried in the interior of the folded protein molecule but exposed if the protein is unfolded. Sometimes these hydrophobic regions are partially exposed even in the native folded protein, and they are often referred to as hydrophobic patches on the protein surface. The lipophilic parts of surfactants interact with these hydrophobic regions,... 

Acyclic chiral a-amino acids or derivatives are also effleient eatalysts for the asymmetric two- or three-components Mannich reaction. Protected or free 2-hydroxyketones reacted with 16 in the presence of L-tiyptophan, O-protected-L-threonine or L-serine and generally led to the a ft-adduct 17, explained by the formation of a (Z)-enamine stabilised by an intramolecular hydrogen bond (Scheme 12.5). Threonine surfactant 14 was equally effective for the three-component reaction with hydro gracetone, benzalde-hyde derivatives and anilines. ... 

Bile salts are natural and chiral anionic surfactants which form helical micelles of reversed micelle conformation. The first report on enantiomer separation by MEKC using bile salts was the enantioseparation of dansylated DL-amino acids (Dns-o,L-AAs) and, since then, numerous papers have been available. Nonconjugated bile salts, such as sodium cholate (SC) and sodium deoxycholate (SDC), can be used at pH > 5, whereas taurine-conjugated forms, such as sodium taurocholate (STC) and sodium taurodeox-ycholate (STDC), can be used under more acidic conditions (i.e., pH > 3). Several enantiomers, such as diltiazem hydrochloride and related compounds, carboline derivatives, trimetoquinol and related compounds, binaphthyl derivatives, Dhs-dl-AAs, mephenytoin and its metabolites, and 3-hydroxy-l,4-benzodiazepins have been successfully separated by MEKC with bile salts. In general, STDC is considered as the the most effective chiral selector among the bile salts used in MEKC. 

An important number of esters of long-chain alcohols and amino acids have been described in the literature. The permethylation of the amino function (Scheme 7) leads to the ammonium salts (7) showing generally interesting surfactant properties [30], We have chosen a similar pathway by reacting a perfluorinated fatty alcohol with chloroacetic acid the subsequent substitution of the chlorine atom by trimethylamine leads to the corresponding ammonium salt (8) [31]. The latter is water soluble, but the hydrolysis of the ester function is rather rapid (<6 h), which renders this type of compound less interesting for possible applications. 

The electrical conductivity of hydrophilic polyamides " and the photoconductivity of nylon-6,6" are reported. The time dependence of two transient photocurrents suggest the possible formation of a space charge in the polymer. Time-dependent effects in the form of creep measurements have also been used to examine the influence of moisture on the behaviour of nylon-6,6. Other low molecular weight molecules, whose effects on the properties of this polymer have been reported are surfactant and both acid and disperse dyes. Also with a textile connotation was a paper with more general application describing the determination of amino-acid N groups in nylon-6 and -6,6. ... 

Thus, regeneration of metal ions, surfactants, polyelectrolytes, poly(amino acid)s, etc., participating in the ionic binding of metal ions in solution will require chemical reactions. Chemical reactions are considered in Chapter 5 in general for their effects on separations. 

---