Surfactant glycopeptides

A library of 50 glycosylamines has been prepared directly from the corresponding unprotected mono- and oligosaccharides. These unprotected glycosylamines are used as intermediates in the synthesis of a number of glycoconjugates such as surfactants, glycopeptides or glycopolymers. 

The occurrence of uronic acid provides another means of easy access to bicyclic lactones, which can be used for the synthesis of various targets, such as surfactants or pseudo glycopeptides. 

CHARACTERISTIC GLYCOPEPTIDE FRACTION OF NATURAL MICROBUBBLE SURFACTANT... 

Subsequent experimental work in this laboratory was aimed at the systematic development of an efficient method for isolating the proteinaceous surfactants, which help stabilize natural microbubbles, from both commercial agarose powder and from forest soil samples collected locally. Successful isolation of this glycopeptide fraction was eventually achieved (ref. 322), and the results obtained from an extended program of chemical analysis, to further characterize and compare chemically these proteinaceous surfactants from both natural substances, are described below. 

Isolation of microbubble glycopeptide surfactant from commercial agarose and forest soil... 

C) for several months. The precipitated agarose, from which the glycopeptide surfactant had been extracted, retained its capacity to form gels and these were later used in decompression tests (see below). 

Thereafter, to remove suspected high-molecular-weight polysaccharide contaminants, a modified filtration procedure was developed. This particular procedure involved first passing the original 80%-ethanol extract of the microbubble glycopeptide surfactant through a 5,000-dalton cut-off molecular filter (Nucle-... 

Amino acid composition3 of microbubble glycopeptide surfactant isolated from agarose powder and forest soil. (Taken from ref. 322.)... 

Thereafter, approximate quantitative determinations of the carbohydrate content of the microbubble glycopeptide surfactant were made through the use of degradative enzymes. Table 4.3 summarizes the results from polyacrylamide (slab) gel electrophoresis of glycopeptide surfactant treated with P-N-acetyl-hexosaminidase, both alone and with endoglycosidase H. The... 

Calculation is based on a molecular weight of approximately 5,200 daltons for untreated microbubble glycopeptide surfactant, as determined in Table 4.3. 

Table 4.3). This same negative result for endoglycosidase H was found in a second test employing a higher concentration of both enzymes, and a much longer reaction period with the microbubble glycopeptide surfactant (Table 4.4). 

An effort was made to better quantitate this suggested preponderance of N-acetylglucosamine and/or N-acetylgalactos-amine in the carbohydrate portion of microbubble glycopeptide surfactant by performing direct HPLC analysis of the monosaccharides contained in the surfactant. This analysis began with the (carbohydrate) hydrolysis of a partially purified preparation containing approximately 30 pg of the proteinaceous microbubble... 

Fig. 4.3. High performance liquid chromatography (HPLC) of the monosaccharides obtained from a partially purified preparation of microbubble glycopeptide surfactant from forest soil. Following hydrolysis (in 2 N HC1 for 6 hr at 100°C) and filtration, the carbohydrate mixture was charged on a Bio-Rad HPX-87 cation exchange column. For comparison, part A shows the chromatogram (using the same HPLC column) of a standard solution, which contained 4 pg of each of three different monosaccharides (i.e., the last three peaks shown are glucose, xylose and fiicose, in the order of increasing retention times). Part B shows the chromatogram obtained from hydrolysis of the partially purified (see text) microbubble surfactant (approximately 30 pg). All other experimental conditions were identical in the two cases, i.e., water eluent, 0.5 ml/min flow rate, 85°C, refractive index detector attenuation -2x. (Taken from ref. 322.)...

Fig. 4.5. Gel-filtration column chromatography of dansylated microbubble glycopeptide surfactant on Sephadex G-25. The column (0.9 cm I.D. x 55 cm) was equilibrated with 50 mM-Na acetate buffer, pH 4.5, containing 4 M guanidine-HCl. The column was eluted with the equilibrating buffer, at a flow rate of 3.3 ml per hour. The volume per fraction was 0.7 ml, and each fraction was combined with an added 0.8 ml aliquot of the equilibrating buffer before being analyzed for fluorescence. Activation of the dansyl label was performed at 254 nm, and the emitted fluorescent light was monitored at 450 nm. (Taken from ref. 322.)...

REVIEW OF NATURAL-PRODUCT LITERATURE AND POSSIBLE ANIMAL SOURCES OF THE GLYCOPEPTIDE FRACTION OF MICROBUBBLE SURFACTANT... 

Cysteine as cysteic acid, except for microbubble glycopeptide surfactant for which determined as 1/2 Cystine. 

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