The modification of glucose oxidase by palmitic acid ester of N-hydroxysuccinimide leads to the formation of a new hydrophobized enzyme with five covalently bound C16 groups. Such a modification was shown not to alter noticeably the native structure of the enzyme. The modified glucose oxidase displays enhanced surface activity at the water/air interface in comparison with the native enzyme. The max. redn. of surface tension at all concns. studied was higher for the modified glucose oxidase than for the native one. The modified enzyme also displayed a much steeper rise of the surface potential with time and a much more rapid attainment of the satn. plateau than the unmodified enzyme. [on SciFinder(R)]

A review with 29 refs. Cosmetic delivery systems such as different types of emulsions, liposomes, niosomes, and microcapsules are discussed. [on SciFinder(R)]

Formation and surface properties of microcapsules, which are based on interaction of gelatin and sodium dodecyl sulfate (SDS) were investigated. It was found that microcapsules of oil droplets can be obtained at a specific range of SDS/gelatin concn. ratios. Both the amt. of gelatin and SDS which were bound to the oil/water interface were maximal in this range, in agreement with Zeta-potential measurements and fluorescence microscopy performed for FITC labeled gelatin. [on SciFinder(R)]

The formation of microcapsules which contain rosemary oil, is described. The process is based on two steps; (a) formation of oil-in-water emulsions, by using lecithin as emulsifier, thus imparting neg. charges on the oil droplets; (b) addn. of a cationic biopolymer, chitosan, in conditions that favor the formation of an insol. chitosan-lecithin complex. Zeta potential measurements revealed that addn. of very low concns. of chitosan to lecithin stabilized emulsions, led to reversal of charge. At a suitable pH range the chitosan pptd. around the oil droplets forming pos. charged microcapsules. The chitosan-lecithin insol. complex is composed of a 1:1 molar ratio of the chitosan monomeric unit and lecithin, as evaluated by elementary anal. and turbidity measurements. [on SciFinder(R)]

Surface active gelatin was formed by covalent attachment of hydrophobic groups to gelatin mols. The modification was carried out at various degrees of attachment and with various chain lengths. These modified gelatins (MGs) were synthesized in dry DMSO by a simple and rapid method. The new method leads to high yields and allows high degrees of modification. The MGs, which have various hydrophobicities, have better surface activity than the native gelatin, as detd. by surface tension redn. The surface tension redn. is correlated to the hydrophobicity of the modified mol., which was detd. by a fluorescent probe. It appears that both the increase in the no. of the hydrophobic groups and the increase in the chain lengths lead to decreased surface tension. [on SciFinder(R)]

Hydrophobic modification of human IgG by fatty acid esters (C8, C12 and C16) of N-hydroxysuccinimide was carried out. Such a modification leads to a spontaneous formation of micelle-like colloidal clusters with a mean diam. of 19.9-22.7 nm for C8-modified IgG. C12- and C16-modified IgGs form larger clusters in spite of a lower no. of attached alkyl chains. The adsorption of the modified IgGs onto latex particles was studied. It was found that the affinity of modified IgGs to the neg. charged hydrophobic polystyrene surfaces is higher than that of the native protein, although an increase in hydrophobicity is also followed by an increase in the net charge of the protein mol. In all cases, the highest equil. concns. correspond to the nearly satd. layer of adsorbed protein mols., this layer being more compact for hydrophobized IgG. The mol. areas of IgGs on the surface are close to those calcd. from the known structural data for the "leg-on" disposition of the "T"- or "Y"-shaped mols. The modified IgG retains recognition ability in ELISA tests, the activity decreases only at a high degree of modification. [on SciFinder(R)]

The interactions between gelatin and sodium dodecyl sulfate (SDS) were studied, and the conditions which favor formation of insol. complex of gelatin-SDS were applied to form microcapsules of oil droplets. It was found that the insol. complex is formed only while the protein has a net pos. charge, at pH 4.0 and only at a narrow range of surfactant concns., below the crit. micellar concn. The compn. of the coating layer around the oil droplets was evaluated as a function of SDS/gelatin ratio. The maximal adsorbed amt. of gelatin and SDS on the oil droplets corresponds to the SDS concn. in which the zeta potential was minimal and in which insol. gelatin-SDS particles were obtained in absence of the oil phase. [on SciFinder(R)]