In the world of biomolecular analysis, Circular Dichroism (CD) spectroscopy is an essential technique for studying the structural properties of proteins, nucleic acids, and other chiral molecules. Chirascan CD spectrometers lead the way in providing high-sensitivity CD measurements, making them an invaluable tool for researchers in structural biology, pharmaceutical development, and material science.
Here we explore the fundamental principles behind Chirascan systems and their innovative technology.
How Does a Chirascan CD Spectrometer Work?
A Chirascan CD spectrometer generates left- and right-circularly polarized light and measures the differential absorption of these two components by a chiral sample. The system comprises several key components that work together to ensure precise and accurate measurements.
The Light Source: A Xenon Arc Lamp
Chirascan systems use a 150W Xenon arc lamp as the light source, which produces high-intensity ultraviolet (UV) and visible light. This ensures a high signal-to-noise ratio, enabling high-quality data.
However, exposure of oxygen to UV light can produce ozone, which can degrade optical components. To counteract this, the system features an Active Nitrogen Management System (ANMS) to purge oxygen from the optical pathway.
The Monochromator: Precision Polarization Selection
Unlike conventional dual-prism spectrometers, Chirascan systems not only utilize two prisms, but a dual-polarizing monochromator, which offers purer polarized light.
Photoelastic Modulator (PEM): Generating Circularly Polarized Light
A crucial step in CD spectroscopy is converting linearly polarized light into circularly polarized light. This is achieved using a Photoelastic Modulator (PEM), which modulates the phase shift between orthogonal components of the light wave. By controlling this modulation, the system alternates between left- and right-circularly polarized light at a high frequency.
The Sample Interaction: Measuring Circular Dichroism
Once the circularly polarized light interacts with a chiral sample, the differential absorption of left- and right-handed circularly polarized light is measured. This difference is what generates the characteristic CD spectrum, which provides insights into the secondary and tertiary structure of proteins, protein-ligand interactions, and other molecular properties.
High-Sensitivity Detection
Chirascan systems are designed for maximum sensitivity and precision. The advanced models, the Chirascan V100 and Q100 incorporate a solid-state detector (large-area avalanche photodiode, LAAPD) to achieve exceptional signal quality. This detector synchronizes with the PEM frequency to accurately capture data with minimal noise.
Why Choose Chirascan for CD Spectroscopy?
Chirascan spectrometers stand out due to their advanced optical design and high-performance detection capabilities.
Key advantages include:
Modular accessories for expanded functionality, including fluorescence and stopped-flow experiments
Enhanced polarization purity with dual-polarizing monochromators
Solid state detection that provides superior sensitivity
Active Nitrogen Management System (ANMS) to prolong optical component lifespan
