The physical characterisation of polysaccharides in solution. Stephen Harding University of Nottingham

The physical characterisation of polysaccharides in solution Stephen Harding University of Nottingham

The physical characterisation of polysaccharides in solution Viscometry SEC-MALLs Analytical Ultracentrifugation Stephen Harding University of Nottingham Imaging

Physical characterisation 1. Viscosity, stability 2. Heterogeneity, Molecular weight & distribution, stability 3. Conformation in solution 4. Interactions

Physical characterisation 1. Viscosity, stability 2. Heterogeneity, Molecular weight & distribution 3. Conformation in solution 4. Interactions 1: Viscometry. 2: SEC-MALLs & analytical ultracentrifugation. 3: Viscometry, SEC-MALLs & analytical ultracentrifugation. 4. Analytical ulttracentrifugation & atomic force microscopy

1. Viscosity from precision viscometry

1. Viscosity by Precision viscometry [η] Intrinsic viscosity, ml/g

Types of Viscometer: Ostwald Viscometer

Types of Viscometer: 1. U-tube (Ostwald or Ubbelohde) Ostwald Viscometer

Types of Viscometer: 1. U-tube (Ostwald or Ubbelohde) Extended Ostwald Viscometer

Types of Viscometer: 1. U-tube (Ostwald or Ubbelohde) 2. Cone & Plate (Couette) Couette-type Viscometer

Types of Viscometer: 1. U-tube (Ostwald or Ubbelohde) 2. Cone & Plate (Couette) 3. Pressure imbalance on-line viscometer

Auto-timer Coolant system Density meter Solution Water bath + 0.01 o C

Definition of viscosity: For normal (Newtonian) flow behaviour: viscosity τ = (F/A) = η. (dv/dy) shear rate shear stress η = τ/(dv/dy) units: (dyn/cm 2 )/sec -1 At 20.0 o C, η(water) ~ 0.01P = dyn.sec.cm -2.. = POISE (P)

Viscosity of biomolecular solutions: A dissolved macromolecule will INCREASE the viscosity of a solution because it disrupts the streamlines of the flow:

We define the relative viscosity η r as the ratio of the viscosity of the solution containing the macromolecule, η, to that of the pure solvent in the absence of macromolecule, η o : η r = η/η o no units For a U-tube viscometer, η r = (t/t o ). (ρ/ρ o )

Reduced viscosity The relative viscosity depends (at a given temp.) on the concentration of macromolecule, the shape of the macromolecule & the volume it occupies. If we are going to use viscosity to infer on the shape and volume of the macromolecule we need to eliminate the concentration contribution. The first step is to define the reduced viscosity η red = (η r 1)/c If c is in g/ml, units of η red are ml/g

The Intrinsic Viscosity [η] The next step is to eliminate non-ideality effects deriving from exclusion volume, backflow and charge effects. We measure η red at a series of concentrations and extrapolate to zero concentration: [η] = Lim c 0 (η red) units [η] = ml/g sometimes researchers use dl/g so 200 ml/g = 2 dl/g

irradiated (10kGy) guar Huggins η red or η inh (ml/g) [η] Kraemer c (mg/ml)

Viscosity probe: chitosan stability Fee et al, 2006

2. Heterogeneity and molecular weight: SEC-MALLs

2. Heterogeneity and Molecular Weight: SEC-MALLs

Molecular Weight: Light scattering photodiode detectors incident beam transmitted beam

Molecular Weight: Zimm plot 10 6.(Kc/R θ ) 1/M w R g from slope sin 2 (θ/2) + kc (k=100)

Molecular Weight: SEC MALLS

Molecular Weight: SEC MALLS Colonic mucin

Can also couple a pressure imbalance type of viscometer on-line

irradiated (10kGy) guar Huggins η red or η inh (ml/g) [η] Kraemer c (mg/ml)

irradiated (10kGy) guar Huggins Solomon-Ciuta η red or η inh (ml/g) Kraemer c (mg/ml)

Analytical Ultracentrifugation

Optima XLA/ XLI

Sedimentation Velocity Centrifugal force Top view, sector of centrifuge cell Air Solvent Solution conc, c Rate of movement of boundary sed. coeff distance, r s o 20,w Sedimentation coefficient, S

Chitosan G213, 0.5 mg/ml meniscus Cell base

Chitosan G213, 0.5 mg/ml meniscus Cell base

Chitosan G213, 0.5 mg/ml Sedimentation g(s*) plot : from analysis of the change with time of the whole concentration profile

Guar, 0.75 mg/ml

Wheat starch, 8 mg/ml

stability studies SAN02 Freeze-thaw (1.16mg/mL) 0.30 0.25 g*(s) 0.20 0.15 0.10 Control 10cycles 20cycles 25cycles 0.05 0.00 0 10 20 30 40 50 s(s)

Multi-Gaussian fit estimates proportions of each species too:

2 types of AUC Experiment: Sedimentation Velocity Centrifugal force Top view, sector of centrifuge cell Air Solvent Sedimentation Equilibrium Centrifugal force Diffusion Solution conc, c Rate of movement of boundary sed. coeff distance, r s o 20,w 1S=10-13 sec conc, c distance, r STEADY STATE PATTERN FUNCTION ONLY OF MOL. WEIGHT PARAMETERS

Extraction of M w,app from sedimentation equilibrium and MSTAR analysis Chitosan G213 M w,app cell bottom

Extraction of M w,app from sedimentation equilibrium and MSTAR analysis xanthan M w = (5.9+1.1)x10 6 g/mol

3. Conformation in solution

Conformation in solution 1. Experimental data required Molecular weight [η], s, R g 2. Modelling strategies General conformation type (rod, coil or sphere etc.) Measure of flexibility the persistence length, L p, If ~ rigid then aspect ratio.

Conformation in solution 1. Experimental data required Molecular weight: SEC-MALLs reinforced by sed. equilibrium [η], s, R g 2. Modelling strategies General conformation type (rod, coil or sphere etc.) Measure of flexibility the persistence length, L p, If ~ rigid then aspect ratio.

Sedimentation Velocity Centrifugal force Top view, sector of centrifuge cell Air Solvent Solution conc, c Rate of movement of boundary sed. coeff distance, r s o 20,w Sedimentation coefficient, S

s o 20,w extraction κ-carrageenan 1/s 20,w (S -1 ) slope=k s /s o 20,w 1/s o 20,w c (mg/ml)

Molecular Weight: Zimm plot 10 6.(Kc/R θ ) 1/M w R g from slope sin 2 (θ/2) + kc (k=100)

irradiated (10kGy) guar Huggins η red or η inh (ml/g) [η] Kraemer c (mg/ml)

Haug Triangle

Sphere [η] ~ M 0 Rod [η] ~ M 1.8 Coil [η] ~ M 0.5-0.8 s o 20,w ~ M0.67 R g ~ M 0.33 s o 20,w ~ M0.15 R g ~ M 1.0 s o 20,w ~ M0.4-0.5 R g ~ M 0.5-0.6

Mark-Houwink-Kuhn-Sakurada Power law plot Galactomannans a=0.74+0.01

Change in Conformation Rollings, 1992

Sphere [η] ~ M 0 Rod [η] ~ M 1.8 Coil [η] ~ M 0.5-0.8 s o 20,w ~ M0.67 R g ~ M 0.33 s o 20,w ~ M0.15 R g ~ M 1.0 s o 20,w ~ M0.4-0.5 R g ~ M 0.5-0.6 k s /[η] ~1.6 k s /[η] <1 k s /[η] ~1.6

Conformation Zoning: Pavlov, Harding & Rowe., 1997

Conformation Zoning: Extra-rigid Rod: Schizophyllan Rigid-rod: DNA Semi-flexible coil: cellulose derivatives, chitosans Random coil: Dextran, glycoproteins from mucus Globular/Branched: Proteins/glycogen

Pectins: Morris et al., 2007

Worm-like Chain Flexibility parameter: Persistence length L p Contour Length Kuhn-statistical length λ -1 = 2L p

Worm-like Chain Flexibility parameter: Persistence length L p Theoretical limits: Random coil L p = 0 Rigid rod L p = infinity Practical limits: Random coil L p ~ 1-2nm Rigid rod L p ~ 200nm

[ ] 2 1/ 2 1/ 3 1/ 0 3 1/ 0 3 1/ 2 2 w L p L w M M L B M A M Φ + Φ = η ( ) + + + =... 2 2 1.843 3 1 2 1/ 3 2 2 1/ 0 0 0 p L w p L w A L L M M A A L M M N v M s πη ρ Bohdanecky relation Yamakawa-Fujii relation

800 Global plot: xyloglucan 700 M L (g. mol -1. nm -1 ) 600 500 400 300 200 2 4 6 8 10 12 14 16 18 20 L p (nm) Patel et al, 2007

.or if you know the mass per unit length 1.0 0.8 Target function, Δ 0.6 0.4 0.2 0.0 2 4 6 8 10 12 14 16 18 20 L p (nm) Patel et al, 2007

Flexibilities of carbohydrate polymers Carbohydrate Polymer Pullulan Xyloglucan L p (nm) 1-2 5-8 Pectins DNA Schizophyllan Scleroglucan Xanthan 10-20 45 120-200 180+30 200

4. Interactions

Atomic Force Microscopy: chitosan Sedimentation coefficient s o 20,w ~ 1S Deacon et al, 2000

chitosan-mucin complex Sedimentation coefficient s o 20,w ~ 2000S

chitosan-mucin complex Sedimentation coefficient s o 20,w ~ 2000S very strong, irreversible interaction

bioactive arabinoxylan very weak, reversible interaction Patel et al, 2007

bioactive arabinoxylan very weak, reversible interaction

Physical characterisation 1. Viscosity, stability 2. Heterogeneity, Molecular weight & distribution 3. Conformation in solution 4. Interactions

Physical characterisation 1. Viscosity, stability 2. Heterogeneity, Molecular weight & distribution 3. Conformation in solution 4. Interactions Thanks to: Prof. Arthur Rowe, Drs. Gordon Morris, Yanling Lu, Trushar Patel (NCMH) & Professor Jose Garcia de la Torre (Murcia)

for a copy of this presentation http://www.nottingham.ac.uk/ncmh