Vibrational Circular Dichroism (VCD) spectrometer
VCD is defined as the difference in the absorbance (A) of left minus right circularly polarized infrared radiation, A=AL -AR. VCD extends the functionality of electronic Circular Dichroism (CD) into the infrared spectral region where vibrational tranisitions in molecules are observed. VCD combines the structural specificity of FT-IR spectroscopy with the stereo-sensitivity of circular dichroism. This gives access to multiple, well-defined bands that provide molecular quantitative information. Measurements can be done in solids and solutions.
In 1997, BioTools commercialized the technology by introducing the ChiralIR™. BioTools is proud to be the first company to present a stand-alone dedicated VCD spectrometer and its powerful applications in the fields of chemistry and biology.
Unique Advantages of the CHIRALIR-2X™ VCD Spectrometer
- Dual Source increases signal-to-noise ratio (S/N) of approximately 3.6 times over any single-source system
- 30-48 hour hold detector time
- Exclusive stage for elimination of cell artifacts with SyncRoCell™
- Simultaneous collection of IR & VCD spectra (AC & DC)
- Complete spectral range of measurement 4000-850 cm-1 (no change of filters required)
ChiralIR-2X ™ Software is included with the CHIRALIR-2XTM. Easy to use, no learning curve.
Since commercial introduction of VCD by BioTools thousands of compounds have been determined using this technology. It has become the-must-have-tool in the pharmaceutical and other industries.
VCD Application Examples
Proteins – Peptides – Carbohydrates – Nucleic Acids
VCD provides an enhanced sensitivity to secondary structure of proteins and peptides. The changes in VCD spectra are observed in both the Amide I and II regions. The VCD sign of Amide I band changes for proteins with the two most common motifs – α-helical protein myoglobin (lower spectra) and a primarily β-sheet containing proteins concanavalin A and chymotrypsin (upper spectra).
During the course of a chemical stereospecific reaction, the combination of IR, for detection of changes in mole fraction composition, and VCD, for combined mole fraction composition and enantiomeric excess (%EE), enables one to follow %EE of each chiral species as a function of time. The figure above shows epimerization versus time of DDM with trifluoroacetic acid in two different solvents.