Edwin H. Merrifield

Some new aspects of the molecular structure of Acacia senegal gum (gum arabic)

Abstract The gum polysaccharide of Acacia senegal, the main source of gum arabic, has been re-examined by means of two series of sequential Smith degradations, one starting with the whole polysaccharide, the other with a product from which all acid-labile side-chains had been removed by prior partial hydrolysis. Investigation, mainly by methylation analysis and estimation of molecular weight, of the products obtained at each stage of these two series of degradations, both of which ultimately yielded small galactans that appeared to be identical, has afforded evidence for the presence in the polysaccharide chain of uniform blocks of (1→3)-linked d -galactopyranosyl residues; these blocks are comparable in size to those postulated for many arabinogalactans of simpler structure. Some amplification of the structural model proposed for this polysaccharide by earlier workers is possible in the light of these new data.

Structural investigations of two capsular polysaccharides from cryptococcus neoformans

Abstract Two capsular polysaccharides from Cryptococcus neoformans serotype A have been shown to be chemically equivalent. One of these polysaccharides was further investigated and shown to consist of a chain of (1→3)-linked d -mannosyl residues, each of which is substituted at O–2 by a d -glucosyluronic acid or d -xylosyl group.

Structural features of the gum exudates from some Acacia species of the series Phyllodineae and Botryocephalae

Abstract Smith degradation of each of the polydisperse, gum polysaccharides from Acacia pycnantha, A. difformis, A. filicifolia , and A. podalyriaefolia , for which molecular-weight distributions have been measured by gel-permeation chromatography, gives, in good yield, a methanol-insoluble polysaccharide that shows a single peak on examination by this technique. The molecular weights of the Smith-degraded polysaccharides are close to the values expected if the respective gum polysaccharides, on losing periodate-vulnerable, peripheral sugar residues were to be split also at regular intervals between the otherwise (1→3)-linked d -galactose chains. The structures of these gums, which are similar in many respects, conform to the pattern shown recently to occur in the gum of A. baileyana .

Smith degradation of gum exudates from some prosopis species

Abstract The gum polysaccharides from two species of Prosopis, namely, P. glandulosa and P. chilensis, growing in different locations in South Africa, have been found to have similar structural features, closely resembling those reported in the literature for the gum of the North American species P.juliflora (mesquite). On smith degradation, both of the gums examined in the present study yielded a single polysaccharide product, having molecular weight 6,000, a value also found for the corresponding products from several Acacia species. Successive, Smith degradations of the polysaccharide produced by a sample of P. glandulosahave shown that a simple, (1-→3)-linked d -galactan is obtained after only two such degradations. This suggests the presence of uniform blocks of (1→3)-linked d -galactopyranosyl residues in the skeletal chain of the gum polysaccharide similar to those postulated for gums fromAcacia species.

Alterations in Porcine Gastric Mucin during the Development of Experimental Ulceration

Bile duct ligation in the pig results in ulceration of the pars oesophagea (oesophagogastric junction) within 48 h with 100% reproducibility. This work describes novel observations made during development of such ulcers using an endoscope introduced at intervals postoperatively via a Thomas gastric cannula. Macroscopic and histological changes were recorded and compared with quantitative and qualitative changes in crude mucus scrapings and purified mucins. Crude mucus scrapings of the cardiac gland region had a higher protein content in the ulcerated states than in the normals. After bile duct ligation, the (degraded) mucin glycopeptide/total protein ratio was higher in partially purified mucus from pre-ulcerated and ulcerated stomachs as compared with normal samples. The quantity of purified mucin was less in samples from ulcerated stomachs, and the N-acetylgalactosamine and fucose contents were also decreased. It is possible that these changes resulted in the failure of the mucus barrier and the development of oesophagogastric junction ulceration.

Structural studies on the capsular polysaccharide from klebsiella serotype k64

Partial hydrolysis with acid, methylation analysis (including uronic acid degradation), Smith degradation, and p.m.r. spectroscopy have been used to determine the primary structure of the capsular polysaccharide of Klebsiella serotype K64. The hexasaccharide repeating-unit, which also contains one O-acetyl substituent, comprises a 4)-alpha-D-GlcpA-(1 leads to 3)-alpha-D-Manp-(1 leads to 3)-beta-D-Glcp-(1 leads to 4)-alpha-D-Manp-(1 leads to chain with a 4,6-O-(1-carboxyethylidene)-beta-D-glucopyranosyl and an L-rhamnosyl group attached to the 4-linked D-mannosyl residue at 0-2 and 0-3, respectively.

Bacteriophage-associated lyase activity against Klebsiella serotype K64 capsular polysaccharide

Bacteriophage phi 64 possesses a lyase that depolymerises the capsular polysaccharide of Klebsiella K64 into a hexasaccharide having an unsaturated derivative of glucuronic acid at the non-reducing end (1). The unsaturated hex-4-enuronic acid residue generated was characterised spectroscopically (u.v. and n.m.r.) and by g.l.c.-m.s. after hydrogenation of the double bond. Partial hydrolysis, Smith degradation, methylation analysis, and n.m.r. spectroscopy have been used to establish the structures of oligosaccharides produced from the polysaccharide. Evidence from 1H-n.m.r. spectroscopy indicates that the D-Man rho residue that undergoes fission is beta. (Formula: see text).

Structural investigation of Klebsiella K-type 4 capsular polysaccharide

The capsular polysaccharide from Klebsiella K4 contains the tetrasaccharide repeating-sequence leads to 3)-alpha-D-Glcp-(1 leads to 2)-alpha-D-Glcp A-(1 leads to 3)-alpha-D-Manp-(1 leads to 3)-beta-D-Glcp-(1 leads to. P.m.r. spectroscopy and the measurement of optical rotation were used to establish the anomeric linkages in the polysaccharide and in the oligosaccharides derived by partial hydrolysis. The repeating unit also contains one 0-acetyl group.

The subunit structure of heart muscle chalones.

Abstract Recently, chalones have been isolated from adult bovine hearts and purified to homogeneity (2). A combination of equilibrium centrifugation in 6.0 M Guanidinium chloride and SDS polyacrylamide gelelectrophoresis of the chalones both under reduced conditions suggest the involvement of four indentical subunits with a molecular weight of about 150 000 each. Electron microscopy of negatively stained preparations showed a globular structure. From the amino acid analysis it is evident that the chalones has a net negative charge and a predominant hydrophobic amino acid composition. Isoelectric focusing shows a pI of 5.1. The sugars detected were, in molar proportions, D-Mannose (3.0), D-Galactose (2.5), D-Glucose (1.0) and D-Glucosamine (1.7).