پاورپوینت آماده; Intrinsic Viscosity of Macromolecular Solutions

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Viscometry Intrinsic Viscosity of Macromolecular Solutions Viscosity of biomolecules Simple, straightforward technique for assaying
Solution conformation of biomolecules & water binding
Molecular weight of biomolecules
Flexibility “ “ Why viscometry? “U-tube” (Ostwald or Ubbelohde)

“Cone & Plate” (Couette)



Types of Viscometer: Ostwald Viscometer “U-tube” (Ostwald or Ubbelohde)

“Cone & Plate” (Couette)



Types of Viscometer: Extended Ostwald Viscometer “U-tube” (Ostwald or Ubbelohde)

“Cone & Plate” (Couette)




Types of Viscometer: Couette-type Viscometer Water bath + 0.01oC Density meter Coolant system Solution Auto-timer For normal (Newtonian) flow behaviour:

t = (F/A) = h . (dv/dy)


Definition of viscosity: h = t/(dv/dy) units: (dyn/cm2)/sec-1
= dyn.sec.cm-2. . = POISE (P) At 20.0oC, h(water) ~ 0.01P For normal (Newtonian) flow behaviour:

t = (F/A) = h . (dv/dy)


Definition of viscosity: h = t/(dv/dy) units: (dyn/cm2)/sec-1
= dyn.sec.cm-2. . = POISE (P) At 20.0oC, h(water) ~ 0.01P shear stress shear rate viscosity 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 hr as the ratio of the viscosity of the solution containing the macromolecule, h, to that of the pure solvent in the absence of macromolecule, ho:
hr = h/ho units?

For a U-tube viscometer, hr = (t/to). (r/ro) 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
hred = (hr – 1)/c
If c is in g/ml, units of hred are? The Intrinsic Viscosity [h]
The next step is to eliminate non-ideality effects deriving from exclusion volume, backflow and charge effects. By analogy with osmotic pressure, we measure hred at a series of concentrations and extrapolate to zero concentration: [h] = Limc⃗0 (hred) units [h] = ? Form of the Concentration Extrapolation
2 main forms
Huggins equation: hred = [h] (1 + KH[h]c)
Kraemer equation: (