Chirascan

Accessory Note 11

LD.3 Linear Dichroism Detector

Linear dichroism is the difference in the absorption of parallel and perpendicular linearly polarised light. Chirascan can be enabled for measurement of LD spectra simply by switching from the standard detector to the LD.3 detector; this comprises a photomultiplier detector and amplifier tuned to twice the PEM modulation frequency. Sample handling and orientation is left to the discretion of the user. Most commonly a flow through cell is used, such as the one pictured, and sample is continuously pumped through the beam path to promote sample orientation. The use of a Couette flow cell is also well established1,2,3

Sample Calf Thymus DNA Solvent 10 mM pH 7 Sodium Cacodylate buffer Concentration 5 mg/l (approx) Step size 1.0 nm Bandwidth 1 nm Time per point 1 s Pathlength 0.5 mm Duration of measurement 4 minutes

The LD spectrum (above) is of Calf Thymus DNA under the conditions tabulated. This is raw data; no post-acquisition smoothing (or filtering) has been applied. Also shown (blue trace) is the LD spectrum obtained from the sample when there is no flow (i.e. no sample orientation).

^{1 Wada, A., and S. Kozawa. 1964. Instrument for the studies of differential flow dichroism of polymer solutions. Journal of Polymer Science Part A. 2:853–864.}

^{2 Rachel Marrington, Timothy R.Dafforn, David J. Halsall and Alison Rodger, Biophysical Journal 87:2002-2012 (2004) Micro-Volume Couette Flow Sample Orientation for Absorbance and Fluorescence Linear Dichroism.}

^{3 Rachel Marrington, Timothy R. Dafforn, David J. Halsall, James I. MacDonald, Matthew Hicks and Alison Rodger, Analyst, 2005, 130, 1608 - 1616, Validation of new microvolume Couette flow linear dichroism cells.}

Other Chirascan Accessories

• PCS.3 Single Cell Holder with Peltier Temperature Control
• PCM.3 Four Position Cell Autochanger with Peltier Temperature Control
• TT.3 Dual Syringe Titrator
• TF.3 Total Fluorescence Detector
• FP.3 Fluorescence Polarisation / Anisotropy Accessory
• SM.3 Scanning Emission Monochromator
• MCD.3 1T Permanent Magnet for Magnetic Circular Dichroism
• FDCD Fluorescence Detected Circular Dichroism
• MC.3 Multi-Channel Fluorescence
• J.3 Julabo AWC-100 recirculating cooler for use with the Peltier
• LD.3 Linear Dichroism Detector
• ORD.3 Optical Rotary Dispersion Accessory
• IR.3 Extended NIR Photomultiplier Detector
• LT.3 Liquid Nitrogen Cryostat
• SF.3 Stopped-flow accessory