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“Global” Hydrodynamic Analysis of the Molecular
Flexibility of Konjac Glucomannans
Gordon Morris
School of Biosciences
Outline:
1. Introduction
2. Hydrodynamic characterisations
3. Conformational analyses
4. Conclusions and Future Work
Why characterisation of Konjac glucomannan (KGM) is important
Introduction:
- Widely used but poorly understood health food supplement
- Reported potential interaction with wheat gliadins: application in gluten removal
- Biopolymer of interest in diabetes research
1. Extracted from the tubers of Amorphophullus Konjac C. Koch
2. Water-soluble gum
3. -(14) -D-glucose (G) and -D-mannose (M) - G:M ratio 1:1.6- C-6 acetylation (5 – 10 %)
KGM:
Hydrodynamic characterisations:
Sedimentation Velocity in the Analytical Ultracentrifuge- sedimentation coefficient, s0
20,w
- concentration dependence of sedimentation, ks
Size Exclusion Chromatography coupled to Multi-Angle Laser Light Scattering
- weight average molar mass, Mw
Viscometry- intrinsic viscosity, []
Sample Mw
(g mol-1)
[]
(ml g-1)
s020,w
(S)
ks
(ml g-1)
KGM-1 740000
± 20000
1300
± 15
3.40
± 0.02
665
± 20
KGM-2 695000
± 20000
1190
± 25
3.00
± 0.03
455
± 25
KGM-3 305000
± 10000
775
± 5
2.50
± 0.10
275
± 30
KGM-4 240000
± 5000
565
± 10
1.67
± 0.20
115
± 30
KGM-5 210000
± 5000
475
± 5
1.92
± 0.10
160
± 30
Results:
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
0.5 1.0 1.5 2.0 2.5-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
log
(1
0-11 ksML)
log (1012[s]/ML)
A
B
C
D
E
0.5 1.0 1.5 2.0 2.5-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
log
(1
0-11 ksML)
log (1012[s]/ML)
A
B
C
D
E
0 .5 1 .0 1 .5 2 .0 2 .5
-0 .5
0 .0
0 .5
1 .0
1 .5
2 .0
2 .5
3 .0
3 .5
Extra rigid rode.g. schizophyllan
Rigid rode.g. xanthan
Semi-flexible coile.g. pectinRandom coil
e.g. pullulan
Globulare.g. glycogen
SedimentationConformation Zoning:
KGM: semi-flexible coil
Pavlov et al. (1997). Trends in Analytical Chemistry, 16, 401-405.
Bushin-Bohdanecky:
Lp ~ 8 nm
Semi-flexiblecoil
Bohdanecky (1983). Macromolecules, 16, 1483-1493.Bushin et al., (1981). Vysokomolekulyarnye Soedineniya, A23, 2494-2503.
Yamakawa-Fujii:
Lp ~ 33 nm
Rigid rod
Yamakawa & Fujii (1973). Macromolecules, 6, 407-405.
Lp ~ 13 nmML ~ 330 g mol-1 nm-1
Semi-flexiblecoil
HYDFIT:
Ortega & García de la Torre (2007). Biomacromolecules, 8, 2464-2475.
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/[] 0.4 ± 0.1
f/fo 11 ± 2
Summary:
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
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
Acknowledgements:
