Lesley A.S. Parolis
Rhodes University
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Featured researches published by Lesley A.S. Parolis.
Carbohydrate Research | 1996
Haralambos Parolis; Lesley A.S. Parolis; Isabel F. Boán; Francisco Rodriguez-Valera; Göran Widmalm; M.Cristina Manca; Per-Erik Jansson; Ian W. Sutherland
The halophilic Archaeon Haloferax mediterranei exudes into the growth medium a high molecular weight sulfated polysaccharide. The structure of the repeating unit of this polymer was determined by a combination of glycose, methylation, and sulfate analysis, periodate oxidation, and 1D and 2D NMR spectroscopic analysis of the native and periodate-oxidised/reduced polysaccharides. The location of the sulfate group was established from the 1H and 13C NMR data. The structure of the repeating unit of the polysaccharide may be written as [formula: see text]
Carbohydrate Research | 1998
Lesley A.S. Parolis; Haralambos Parolis; Lennart Kenne; Morten Meldal; Klaus Bock
The exopolysaccharide produced by Pichia (Hansenula) holstii NRRL Y-2448 is composed of a phosphomannan core to which oligosaccharide diester phosphate side chains are appended. The oligosaccharides of the side chains were released as oligosaccharide phosphates and neutral oligosaccharides by mild hydrolysis with aqueous acetic acid and aqueous hydrogen fluoride, respectively. The liberated oligosaccharide phosphates were studied by NMR spectroscopy and by electrospray and fast atom bombardment mass spectrometry. The structures of the neutral oligosaccharides were determined by 1D and 2D NMR spectroscopic experiments. Further insight into the length of the side chains was obtained from a matrix assisted laser desorption ionisation-time of flight mass spectrometric study of high and low molecular weight fragments obtained from partial acid hydrolysis of the native polysaccharide.
Carbohydrate Research | 1998
Nikolai A. Paramonov; Lesley A.S. Parolis; Haralambos Parolis; Isabel F. Boán; Josefa Antón; Francisco Rodriguez-Valera
The structure of the neutral exocellular polysaccharide isolated from the Archaeon Haloferax gibbonsii (ATCC 33959) has been determined using acid hydrolysis, methylation analysis and NMR spectroscopy. The polysaccharide contained D-Man, D-Glc, D-Gal and L-Rha in the ratios 2:1:3:1. The substitution patterns of the sugar residues were deduced from the methylation analysis which indicated the polymer to be composed of a heptasaccharide repeating unit containing two branches. The 1H and 13C NMR resonances of the component sugars were assigned using COSY, HOHAHA, HMQC, and HMQC-TOCSY 2D NMR experiments and the sequence of the sugars in the repeating unit was determined from NOESY and HMBC experiments. The structure can be written as: [formula: see text]
Carbohydrate Research | 1997
Haralambos Parolis; Lesley A.S. Parolis; Gianfranco Olivieri
The O-specific polysaccharide isolated from the lipopolysaccharide (LPS) of Escherichia coli O121 by mild acid hydrolysis has been studied using mainly NMR spectroscopy. The polysaccharide was treated with mild base to yield a O-deacetylated polysaccharide which contained D-GlcNAc, D-GalNAcA, D-GalNAcAN (2-acetamido-2-deoxy-D-galacturonamide) and D-Qui4NAcGly (where D-Qui4N is 4-amino-4,6-dideoxy-D-glucose) in equimolar proportions. The presence of the amide was confirmed by recording the 1H NMR spectrum of the O-deacetylated polysaccharide at different pH values. The O-acetyl group was located on O-3 of the GalNAcAN and the structure of the polysaccharide can be written as [sequence: see text] This structure is almost identical to that previously reported for the O-specific polysaccharide of Shigella dysenteriae type 7 LPS, the only difference being that O-acetylation is stoichiometric in the latter.
Carbohydrate Research | 1992
Lesley A.S. Parolis; Haralambos Parolis; Guy G.S. Dutton; Phillip Lee Wing; Brent J. Skura
The structure of the exocellular glycocalyx polysaccharide of Pseudomonas fragi ATCC 4973, a bacterium implicated in the spoilage of meat, has been determined using hydrolysis, methylation analysis and 1D- and 2D-n.m.r. spectroscopy. The polysaccharide, which aids in the adhesion of the cells to each other and to the meat tissue, has the regular repeating unit ----4)-3-O-[(R)-1-carboxyethyl]-alpha-D-Glcp-(1----3)-beta-D-ManpNAc+ ++- (1----4)-beta-D-Glcp-(1----. Random partial O-acetylation occurred in some preparations of the polysaccharide.
Carbohydrate Research | 1999
Lesley A.S. Parolis; Haralambos Parolis; Nikolai A. Paramonov; Isabel F. Boán; Josefa Antón; Francisco Rodriguez-Valera
The structure of a linear, acidic exopolysaccharide isolated from the Archaeon Haloferax denitrificans ATCC 35960 has been determined using NMR spectroscopy. The sugar residues in the repeating unit of the polysaccharide were identified as Gal and GlcA2,3NAc after the assignment of the 1H and 13C resonances using COSY, HOHAHA, HMQC and HMQC-TOCSY experiments. The sequence of the residues in the polysaccharide was established from the inter-residue connectivities observed in the HMQC-NOESY plot. The only sugar released on acid hydrolysis was shown to be D-Gal by GLC analysis, while the absolute configuration of the acidic sugars was shown to be D by comparison of the carbon chemical shifts with those of model compounds. Partial acid hydrolysis yielded a tetrasaccharide, terminated by D-Gal at the reducing end, whose structure confirmed that of the repeating unit of the polysaccharide as-->4)-beta-D-GlcpA2,3NAc-(1-->4)-beta-D-GlcpA2, 3NAc-(1-->4)-alpha-D-GlcpA2,3NAc-(1-->3)-alpha-D-Galp- (1-->, where D-GlcpA2,3NAc is 2,3-diacetamido-2,3-dideoxy-D-glucopyranosiduronic acid.
Carbohydrate Research | 1987
Guy G.S. Dutton; Haralambos Parolis; Lesley A.S. Parolis
The acidic capsular polysaccharide isolated from Escherichia coli O9:K9:H12 was investigated by using n.m.r. spectroscopy, methylation analysis, periodate oxidation, and bacteriophage-borne enzyme degradation. The polysaccharide, the structure of which is shown below, is the third E. coli capsular polysaccharide reported to contain neuraminic acid, the others being the K1 and K92 polysaccharides, and it is the first in the E. coli series shown to contain a 4-linked neuraminic acid unit. (formula; see text).
Analytica Chimica Acta | 1990
Zamas Lam; Melvin B. Comisarow; Guy G.S. Dutton; Haralambos Parolis; Lesley A.S. Parolis; Asgeir Bjarnason; David A. Weil
Abstract The positive- and negative-ion laser desorption ionization Fourier transform ion cyclotron resonance mass spectra of two known, underivatized, linear oligosaccharides obtained by enzymatic hydrolysis with bacterial viruses of the corresponding native bacterial capsular polysaccharides were analyzed. The high-resolution spectra, estimated to be from less than 1 nmol of sample, showed prominent pseudo-molecular ions, as well as fragment ions derived from glycosidic bond and ring cleavages. For some of these frequently observed ring fragments, structures are proposed by analogy to known even-electron gas phase fragmentations and even-electron solution chemistry. The structures of the capsular biopolymers were delineated from these fragmentations, confirming that Klebsiella pneumoniae serotype K3 capsular polysaccharide is made up of a pentasaccharide repeating unit, consisting of four hexoses, one hexuronic acid and one pyruvic acid acetal; and confirming that the tetrasaccharide repeating unit of Escherichia coli serotype K9 is composed of two hexoses, one acetamido hexose and one N -acetyl neuraminic acid. The analysis of oligosaccharides containing N -acetylated sugars was complicated by the fact that an amino hexose attached to a −C 2 H 3 O 2 ring fragment shares the same elemental formula as an acetamido hexose. Nevertheless, other less ambiguous structural ions could be used for sequencing. Furthermore, analysis of the ring fragments also provided some indication of the positions of linkage of certain monosaccharide residues.
Carbohydrate Research | 1988
Lesley A.S. Parolis; Haralambos Parolis; Heiner Niemann; Stephan Stirm
The primary structure of the acidic capsular polysaccharide isolated from Klebsiella serotype K22 has been investigated using methylation analysis, hydrolysis, bacteriophage-borne enzyme degradation, and n.m.r. spectroscopy. The repeating unit comprises the chain disaccharide----3)-beta-D-Galp-(1----4)-beta-D-Glcp-(1---- substituted by 4-O-[(S)-1-carboxyethyl]-beta-D-GlcpA-(1----6)-alpha-D-Glcp-(1---- at O-4 of the galactose. The galactose carries an O-acetyl group on position 6.
Carbohydrate Research | 1994
Darryl V. Whittaker; Lesley A.S. Parolis; Haralambos Parolis
The structure of the exocellular capsular polysaccharide expressed by Escherichia coli O8:K48:H9 has been investigated by hydrolysis and methylation analysis, and by NMR spectroscopic studies of the polysaccharide and of the oligosaccharides generated by solvolysis with anhydrous HF. The capsular polysaccharide was shown to have the repeating unit: [formula: see text] where beta-L-Sug p represents 2,3-diacetamido-2,3,6-trideoxy-beta-L- mannopyranose.