Recent Advances in DLS and DPI by kws19363

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									 Recent Advances in DLS
 and DPI




Dave Dolak, Malvern Instruments
RAMC 2007, San Diego
Classical vs. Backscatter Dynamic
Light Scattering (DLS)
Backscatter Optics
Backscatter optics facilitate a variable cell position, accommodating both high
& low concentration samples. The increased scattering volume ensures high
sensitivity, without compromising the working size range or needing to resort
to high power lasers which can lead to thermal convection.

                                                  Scattering Volumes
                       Concentrated
                         Samples




    Dilute
   Samples
Advantages of backscatter optics
in the Zetasizer Nano instrument
 Broad concentration range preserves original sample conditions
 (“Does my sample actually change at lower concentrations?”)
 Expanded size range (0.6nm - 6um)
 Enhanced sensitivity yet can handle high concentrations and low
 concentrations without user intervention/sample prep.
 Ease of sample preparation
   Reduced dust problems: dust/large aggregates scatter light more
    in the 90-degree and forward direction. (Dust and large
    aggregates “hosed” 90-degree DLS rendering count rate too
    variable for measurement.) No so at 173º.
   No sample filtration required!
Recent advance: Size and MW from
Absolute Size Exclusion Chromatography (ASEC)




 High resolution
      from
 chromatography
    separation
        +
 Ease of use with
  dynamic light
    scattering
  DPI technology overview




DPI stacks two waveguides together--separated by a spacer – which yields an interference
pattern at the end of the waveguides. If one waveguide is used as the experimental
surface, then changes in the interference pattern can be analyzed to deduce what is
happening at the adsorbed layer when various materials are adsorbed to it or as those
adsorbed materials change.
DPI Return
DPI offers the ability to quantify changes in
the thickness and density (to the sub-
Angstrom level) on the chip surface.
                                                          Sample Liquid

     Thickness
     Refractive index
                                      ~100nm
     Density
     Mass                                             Sensing Waveguide
     Molar Coverage
     Volume Fraction
                                                Rest of sensor chip structure including
                                                         reference waveguide



Sensitive to sub-Angstrom changes in size at picogram
concentrations--can detect onset of crystallization at nucleation.
                Shape orientation, binding & conformational
                changes
                                Lysozyme pH4
                         pH 4 Lysozyme (pI = 11) Adsorption at 1.0 g dm-3                                                          Lysozyme pH7
                                                                                                                        pH7 Lysozyme Adsorption at 1.0 g dm-3 (15 uL/min)
                6                                                           1.46                                    7                                                          1.55



                5                                                           1.44
                                                                                                                    6
                                                                                                                                                                               1.5
                                                                            1.42
                4                                                                                                   5




                                                                                   Refractive Index
Response / nm




                                                                                                                                                                                      Refractive Index
                                                                            1.4
 and ng/mm2




                                                                                                      Response nm
                                                                                                                    4




                                                                                                       and ng/mm2
                3                                                                                                                                                              1.45
                                                                            1.38
                2                                                                                                   3
                                                                            1.36
                                                                                                                                                                               1.4
                                                                                                                    2
                1
                                                                            1.34
                                                                                                                    1
                0                                                           1.32                                                                                               1.35
                 1890           2390            2890           3390
                                                                                                                     0
                -1                                                          1.3                                      1210   1310   1410   1510    1610    1710   1810   1910
                                             Time/s                                                                 -1                                                         1.3

                                                                                                                                                 Time/s



                        Sensor Surface                           30Å                                                                         45Å
                                                                                                                               Sensor Surface

                                                                        Dual Polarization Interferometry (DPI) confirms specific
                                                                        binding of Biotin with Streptavidin and resulting
                                                                        conformational change.
                            Sensor Surface
Membrane behavior and interactions
The Truth Is Out There




DLS and DPI offer new insights
into macromolecular behavior.

								
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