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A new oligomeric surfactant: N,N,N',N?,N?- pentamethyl diethyleneamine—N,N?-di-[tetradecylammonium bromide] referred to as 14-2-N(CH3)-2-14 was synthesized, purified and characterized by Elemental Analysis, 1H and 13C NMR and Electrospray. The micellar properties of this compound were determined by electrical conductivity and surface tension methods. Optical microscopy was also employed to study the behavior of anhydrous surfactant and the binary water/surfactant system as a function of temperature. The critical micellar concentration (cmc), degree of counterion binding and thermodynamic parameters of micellization (standard molar Gibbs energy, enthalpy and entropy of micellization) were determined by electrical conductivity measurements in the temperature range [24–54 °C]. Surface tension measurements also provide information about the dependence of the surface tension at the cmc (?cmc), pC20(negative logarithm of the surfactant's molar concentration C20, required to reduce the surface tension by 20 mN/m, the surface excess (Gmax) at air/solution interface, the minimum area per surfactant molecule at the air/solution interface (Amin), surface pressure at the cmc (?cmc), critical packing parameter(CPP) and the standard free energies of micellization (?Gm0) and of adsorption (?Gads0).

A vesicle-to-ribbon transition has been observed in extremely dilute 1-O-(l-arginyl)-2, 3-O-di-decanoyl-sn-glycerol dichlorohydrate (1010R) surfactant systems by means of static light scattering. At concentration as low as 0.005 mM the solutions scattered significantly. From the angular dependence and molecular weight of the aggregates a vesicular structure is suggested. Increasing surfactant concentration in water induces the vesicle-to-ribbon transition at concentrations as low as 0.5 mM. This transition is accompanied by a strong decrease of scattered intensity and change in angular dependence. Lowering the pH at a fixed concentration can induce the same transition. Both parameters change the protonation of the surfactant, inducing an increase in preferred surfactant head-group area. Those findings are congruent with the observed surface tension behaviour as a function of surfactant concentration and suggests an explanation for the widely different critical micellar concentration (c.m.c.) as determined by different techniques.

A vesicle-to-ribbon transition has been observed in extremely dilute 1-O-l-arginyl-2, 3-O-di-decanoyl-sn-glycerol dichlorohydrate 1010R surfactant systems by means of static light scattering. At concentration as low as 0.005 mM the solutions scattered significantly. From the angular dependence and molecular weight of the aggregates a vesicular structure is suggested. Increasing surfactant concentration in water induces the vesicle-to-ribbon transition at concentrations as low as 0.5 mM. This transition is accompanied by a strong decrease of scattered intensity and change in angular dependence. Lowering the pH at a fixed concentration can induce the same transition. Both parameters change the protonation of the surfactant, inducing an increase in preferred surfactant head-group area. Those findings are congruent with the observed surface tension behaviour as a function of surfactant concentration and suggests an explanation for the widely different critical micellar concentration c.m.c. as determined by different techniques.

Amino acid-based surfactants constitute a class of bio-based surfactants with excellent adsorption and aggregation properties, low potential toxicity and broad biological activity. In this review, the enzymatic synthesis, physicochemical and biological properties as well as the potential uses of these compounds are described.

A novel chemo-enzymatic synthesis of arginine-based gemini cationic surfactants bis(Args) is reported. These compounds consist of two single N^α-acyl-arginine structures connected through the alfa-carboxylic groups of the arginine residues by a α,ω-diaminoalkane spacer chain. N^α-Acyl-L-arginine alkyl ester derivatives were the starting building blocks for the synthesis. The best strategy found consisted of two steps. First, the quantitative acylation of one amino group of the spacer by the carboxylic ester of the N^α-acyl-arginine took place spontaneously, at the melting point of the α,ω-diaminoalkane, in a solvent-free system. The second step was the papain-catalyzed reaction between another N^α-acyl-arginine alkyl ester and the free aliphatic amino group of the derivative formed in the first step. Reactions were carried out in solid-to-solid and solution systems using low-toxic potential solvents. Changes in reaction performance and product yield were studied for the following variables: organic solvent, support for enzyme deposition and substrate concentration. The best yields (70%) were achieved in solid-to-solid systems and in ethanol at aw = 0.07. Bis(Args) analogs of 8, 10 and 12 carbon atoms using 1,3-diaminopropane and 1,3-diamino-2-hydroxy-propane as hydrocarbon spacers were prepared at the 6–7 gram level employing the methodology developed. The overall yields which include reaction and purification varied from 51% to 65% of pure (97–98% by HPLC) product. © 2000 John Wiley & Sons, Inc. Biotechnol Bioeng 70: 323–331, 2000.

A novel enzymatic approach for the synthesis of arginine N-alkyl amide and ester derivatives is reported. Papain deposited onto solid support materials was used as catalyst for the amide and ester bond formation between Z-Arg-OMe and various long-chain alkyl amines and alcohols (H2N-Cn², HO-Cn; n = 8–16) in organic media. Changes in enzymatic activity and product yield were studied for the following variables: organic solvent, aqueous buffer content, support for the enzyme deposition, presence of additives, enzyme loading, substrate concentration, and reaction temperature. The best yields (81–89%) of arginine N-alkyl amide derivatives were obtained at 25°C in acetonitrile with an aqueous buffer content ranging from 0 to 1% (v/v) depending on the substrate concentration. The synthesis of arginine alkyl ester derivatives was carried out in solvent-free systems at 50 or 65°C depending on the fatty alcohol chain length. In this case, product yields ranging from 86 to 89% were obtained with a molar ratio Z-Arg-OMe/fatty alcohol of 0.01. Papain deposited onto polyamide gave, in all cases, both the highest enzymatic activities and yields. Under the best reaction conditions the syntheses were scaled up to the production of 2 g of final product. The overall yields, which include reaction, N^α-benzyloxycarbonyl group (Z) deprotection and purification, varied from 53 to 77% of pure (99.9% by HPLC) product. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 63: 333–343, 1999.