A glucuronomannan (GM) was derived by removal, through Smith degradation, of xylose from the native (3-O-acetylglucurono)xylomannan exopolysaccharide isolated from Tremella mesenterica. 13C-N.m.r. chemical shifts measured at various pD values were compared for p-nitrophenyl β-D-glucopyranosiduronic acid (1) and two GMs (2 and 3) differing in GlcA content (Man:GlcA; 2, 10:1; and 3, 5:1). Also measured and compared were pKa values for 1 and 2. One-dimensional and two-dimensional (COSY and HETCOR) n.m.r. data allowed unambiguous assignments of pD-sensitive chemical shifts due to 2-O-β-D-GlcpA substituents attached to a (1----3)-linked α-D-Manp backbone. The pKa and n.m.r. data indicated that the CO2H groups in either GM are independent of each other, and are similar in behavior to those of p-nitrophenyl β-D-glucopyranosiduronic acid molecules. The n.m.r. data confirmed the previous, chemically deduced, structural role of GlcpA in the native polysaccharide from T. mesenterica, and indicated that significant pD-induced changes occur in the stabilities of the glycosidic orientations in the GM. Previous 13C-n.m.r. assignments for 2-O-β-D-GlcpA in polysaccharides derived from Cryptococcus neoformans serotype A-variant were confirmed, except for the signal due to the anomeric carbon atom. This signal is now known to be pD-sensitive. In acidic solutions, it is coincident with the signal (104.5 p.p.m.) due to the anomeric carbon atoms of the unsubstituted α-D-Manp backbone residues. In basic solutions, the 2-O-β-D-GlcpA anomeric carbon resonance is shifted upfield by approximately 0.2 p.p.m., and is observed as a separate signal.
13C NMR, 1H NMR, Smith degradation, sonication, methanol precipitation, ionization constant measurement
13C NMR data:
Linkage Residue C1 C2 C3 C4 C5 C6
3,3,3,3,3,3,3,3,3 aDManp 104.56 72.32 80.85 68.86 76.18 63.72
3,3,3,3,3,3,3,3 aDManp 104.56 72.32 80.85 68.86 76.18 63.72
3,3,3,3,3,3,3 aDManp 104.56 72.32 80.85 68.86 76.18 63.72
3,3,3,3,3,3 aDManp 104.56 72.32 80.85 68.86 76.18 63.72
3,3,3,3,3 aDManp 105.19 72.54 81.07 69.28 76.30 63.65
3,3,3,3,2 bDGlcpA 104.32 75.32 78.13 74.35 79.47 178.03
3,3,3,3 aDManp 102.41 79.77 79.30 69.08 76.06 63.31
3,3,3 aDManp 104.72 72.54 81.12 69.28 76.30 63.65
3,3 aDManp 104.56 72.32 80.85 68.86 76.18 63.72
3 aDManp 104.56 72.32 80.85 68.86 76.18 63.72
aDManp 104.56 72.32 80.85 68.86 76.18 63.72
1H NMR data:
Linkage Residue H1 H2 H3 H4 H5 H6
3,3,3,3,3,3,3,3,3 aDManp 5.13 4.22 4.03 3.79 3.83 3.80
3,3,3,3,3,3,3,3 aDManp 5.13 4.22 4.03 3.79 3.83 3.80
3,3,3,3,3,3,3 aDManp 5.13 4.22 4.03 3.79 3.83 3.80
3,3,3,3,3,3 aDManp 5.13 4.22 4.03 3.79 3.83 3.80
3,3,3,3,3 aDManp 5.11 4.22 4.02 3.68 ? 4.42
3,3,3,3,2 bDGlcpA 4.49 3.38 3.50 3.58 3.65 -
3,3,3,3 aDManp 5.25 4.28 4.09 3.84 3.98 3.84
3,3,3 aDManp 5.19 4.22 3.96 3.68 ? 4.42
3,3 aDManp 5.13 4.22 4.03 3.79 3.83 3.80
3 aDManp 5.13 4.22 4.03 3.79 3.83 3.80
aDManp 5.13 4.22 4.03 3.79 3.83 3.80
1H/13C HSQC data:
Linkage Residue C1/H1 C2/H2 C3/H3 C4/H4 C5/H5 C6/H6
3,3,3,3,3,3,3,3,3 aDManp 104.56/5.13 72.32/4.22 80.85/4.03 68.86/3.79 76.18/3.83 63.72/3.80
3,3,3,3,3,3,3,3 aDManp 104.56/5.13 72.32/4.22 80.85/4.03 68.86/3.79 76.18/3.83 63.72/3.80
3,3,3,3,3,3,3 aDManp 104.56/5.13 72.32/4.22 80.85/4.03 68.86/3.79 76.18/3.83 63.72/3.80
3,3,3,3,3,3 aDManp 104.56/5.13 72.32/4.22 80.85/4.03 68.86/3.79 76.18/3.83 63.72/3.80
3,3,3,3,3 aDManp 105.19/5.11 72.54/4.22 81.07/4.02 69.28/3.68 76.30/? 63.65/4.42
3,3,3,3,2 bDGlcpA 104.32/4.49 75.32/3.38 78.13/3.50 74.35/3.58 79.47/3.65
3,3,3,3 aDManp 102.41/5.25 79.77/4.28 79.30/4.09 69.08/3.84 76.06/3.98 63.31/3.84
3,3,3 aDManp 104.72/5.19 72.54/4.22 81.12/3.96 69.28/3.68 76.30/? 63.65/4.42
3,3 aDManp 104.56/5.13 72.32/4.22 80.85/4.03 68.86/3.79 76.18/3.83 63.72/3.80
3 aDManp 104.56/5.13 72.32/4.22 80.85/4.03 68.86/3.79 76.18/3.83 63.72/3.80
aDManp 104.56/5.13 72.32/4.22 80.85/4.03 68.86/3.79 76.18/3.83 63.72/3.80
report error
Found 2 records.
Displayed records from 1 to 2
