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Clinical and Diagnostic Laboratory Immunology, March 1998, p. 146-159, Vol. 5, No. 2
1071-412X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.

Cryptococcus neoformans Chemotyping by Quantitative Analysis of 1H Nuclear Magnetic Resonance Spectra of Glucuronoxylomannans with a Computer-Simulated Artificial Neural Network

Robert Cherniak,1,* Homayoun Valafar,2 Laura C. Morris,1 and Faramarz Valafar2

Department of Chemistry, Laboratory for Biological and Chemical Sciences, Georgia State University, Atlanta,1 and Complex Carbohydrate Research Center, University of Georgia, Athens,2 Georgia

Received 15 September 1997/Returned for modification 11 December 1997/Accepted 30 December 1997

The complete assignment of the proton chemical shifts obtained by nuclear magnetic resonance (NMR) spectroscopy of de-O-acetylated glucuronoxylomannans (GXMs) from Cryptococcus neoformans permitted the high-resolution determination of the total structure of any GXM. Six structural motifs based on an alpha -(1right-arrow3)-mannotriose substituted with variable quantities of 2-O-beta - and 4-O-beta -xylopyranosyl and 2-O-beta -glucopyranosyluronic acid were identified. The chemical shifts of only the anomeric protons of the mannosyl residues served as structure reporter groups (SRG) for the identification and quantitation of the six triads present in any GXM. The assigned protons for the mannosyl residues resonated at clearly distinguishable positions in the spectrum and supplied all the information essential for the assignment of the complete GXM structure. This technique for assigning structure is referred to as the SRG concept. The SRG concept was used to analyze the distribution of the six mannosyl triads of GXMs obtained from 106 isolates of C. neoformans. The six mannosyl triads occurred singularly or in combination with one or more of the other triads. The identification and quantitation of the SRG were simplified by using a computer-simulated artificial neural network (ANN) to automatically analyze the SRG region of the one-dimensional proton NMR spectra. The occurrence and relative distribution of the six mannosyl triads were used to chemotype C. neoformans on the basis of subtle variations in GXM structure determined by analysis of the SRG region of the proton NMR spectrum by the ANN. The data for the distribution of the six SRGs from GXMs of 106 isolates of C. neoformans yielded eight chemotypes, Chem1 through Chem8.

* Corresponding author. Mailing address: Department of Chemistry, Georgia State University, University Plaza, Atlanta, GA 30303. Phone: (404) 651-3868. Fax: (404) 651-1416. E-mail: cherniak{at}gsu.edu.

Clinical and Diagnostic Laboratory Immunology, March 1998, p. 146-159, Vol. 5, No. 2
1071-412X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.


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