1. School of Biosciences
“Global” Hydrodynamic Analysis of the Molecular Flexibility of Konjac Glucomannans
Gordon Morris

2. Outline:
1. Introduction 2. Hydrodynamic characterisations 3. Conformational analyses 4. Conclusions and Future Work

3. Introduction: Why characterisation of Konjac glucomannan
(KGM) is important
- Widely used but poorly understood health food supplement - Reported potential interaction with wheat gliadins: application in gluten removal - Biopolymer of interest in diabetes research

4. KGM:
1. Extracted from the tubers of Amorphophullus Konjac C. Koch 2. Water-soluble gum 3. b-(14) b-D-glucose (G) and b-D-mannose (M) - G:M ratio 1: C-6 acetylation (5 – 10 %)

5. Hydrodynamic characterisations:
Sedimentation Velocity in the Analytical Ultracentrifuge - sedimentation coefficient, s020,w - concentration dependence of sedimentation, ks Size Exclusion Chromatography coupled to Multi-Angle Laser Light Scattering - weight average molar mass, Mw Viscometry - intrinsic viscosity, [h]

6. Results: Sample Mw (g mol-1) [h] (ml g-1) s020,w (S) ks KGM-1 740000
± 20000
1300
± 15
3.40
± 0.02
665
± 20
KGM-2
695000
1190
± 25
3.00
± 0.03
455
KGM-3
305000
± 10000
775
± 5
2.50
± 0.10
275
± 30
KGM-4
240000
± 5000
565
± 10
1.67
± 0.20
115
KGM-5
210000
475
1.92
160

7. Conformational analyses:
1. Sedimentation conformation zoning 2. Bushin-Bohdanecky approach 3. Yamakawa-Fujii approach 4. Combined “global” analysis: HYDFIT 5. Mark-Houwink-Kuhn-Sakurada (MHKS) relation 6. Wales-van Holde & frictional ratios

8. Sedimentation Conformation Zoning: KGM: semi-flexible coil
Extra rigid rod
e.g. schizophyllan
Rigid rod
e.g. xanthan
KGM:
semi-flexible coil
Semi-flexible coil
e.g. pectin
Random coil
e.g. pullulan
Globular
e.g. glycogen
Pavlov et al. (1997). Trends in
Analytical Chemistry, 16,

9. Bushin-Bohdanecky: Lp ~ 8 nm Semi-flexible coil
Bohdanecky (1983). Macromolecules, 16,
Bushin et al., (1981). Vysokomolekulyarnye Soedineniya, A23,

10. Yamakawa-Fujii: Lp ~ 33 nm Rigid rod
Yamakawa & Fujii (1973). Macromolecules, 6,

11. HYDFIT: Lp ~ 13 nm ML ~ 330 g mol-1 nm-1 Semi-flexible coil
Ortega & García de la Torre (2007). Biomacromolecules, 8,

12. Summary: Property Value Conformation Zone C Lp (nm) from HYDFIT 13 ± 1
MHKS exponent “a”
0.74 ± 0.01
MHKS exponent “b”
0.32 ± 0.01
ks/[h]
0.4 ± 0.1
f/fo
11 ± 2

13. Conclusions 1. Discrepancy between Bushin-Bohdanecky and Yamakawa-Fujii approaches - best to use non-biased HYDFIT method 2. Konjac glucomannan has a semi-flexible coil conformation Future Work 1. Characterisation of KGM-gliadin complexes 2. Investigation of KGM-insulin mixtures

14. Acknowledgements:
Prof. Stephen E. Harding & Ali Saber Abdelhameed, University of Nottingham, UK Dr. M. Samil Kök, University of Bolu, Turkey Dr. Jose Garcìa de la Torre & Dr. Alvaro Ortega, University of Murcia, Spain