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CIRCULAR DICHROISM SPECTROSCOPY

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Ellipticity, Prism Polarizer ... used units are mean residue ellipticity, (degree cm2/dmol), and the difference ... The molar ellipticity [ ] is related to the ... – PowerPoint PPT presentation

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Title: CIRCULAR DICHROISM SPECTROSCOPY


1
CIRCULAR DICHROISM SPECTROSCOPY
  • structural analysis of nmol samples of
    macromolecules
  • Prof. Eric Wickstrom

2
Circular Dichroism is the difference in
absorption between left and right hand circularly
polarised light in chiral molecules. A chiral
molecule is one with a low degree of symmetry
which can exist in two mirror image isomers.
Illustrated above is an example of circular
dichroism in glucose, a simple sugar.
3
? E
? B
orthogonal electronic (E) and magnetic (B)
components of linearly polarized light
4
electronic field of linearly polarized light
(left) right-handed circularly polarized light
(right)
5
Ellipticity, ?
6
? ? Prism Polarizer
7
The most commonly used units are mean residue
ellipticity, ? (degreecm2/dmol), and the
difference in molar extinction coefficients
called the molar circular dichroism, eL-eR ?e
(liter/molcm). The molar ellipticity ? is
related to the difference in extinction
coefficients by ? 3298 ?e.
8
Typical Initial Concentrations
  • Protein Concentration 0.5 mg/ml
  • Cell Path Length 0.5 mm
  • Stabilizers (Metal ions, etc.) minimum
  • Buffer Concentration 5 mM or as low as possible
    while maintaining protein stability
  • Contaminants Unfolded protein, peptides,
    particulate matter (scattering particles)

9
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