“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: