How to Interpret Circular Dichroism Analysis Results?

The circular dichroism spectrum is a commonly used analytical technique in biopharmaceuticals, which can be used to study the structure and conformation changes of biological macromolecules. By measuring the absorption of the sample to the left and right circularly polarized light at different wavelengths, we can obtain the circular dichroism spectrum.

 

Basic Structure of the Circular Dichroism Spectrum

The circular dichroism spectrum usually consists of two curves: the positive circularly polarized light curve and the negative circularly polarized light curve. The positive circularly polarized light curve represents the absorption of the sample to the right circularly polarized light, while the negative circularly polarized light curve represents the absorption of the sample to the left circularly polarized light. The shape and peak position of these two curves can provide information about the structure and conformation of the sample.

 

Interpretation of Peak Position

The peak position in the circular dichroism spectrum can provide us with secondary structure information of the sample. Generally, the α-helix structure will show a negative peak at 190-200 nm, while the β-sheet structure will show a positive peak at 210-220 nm. By observing the changes in peak position, we can infer the changes in the secondary structure of the sample.

 

Interpretation of Peak Intensity

In addition to the peak position, the peak intensity in the circular dichroism spectrum is also an important indicator for interpreting the structure of the sample. The peak intensity reflects the degree of absorption of the sample to circularly polarized light, and the higher the intensity, the stronger the absorption. By comparing the peak intensities of different samples, we can judge their structural differences.

 

Interpretation of Chromatogram Shape

In addition to the peak position and peak intensity, the overall shape of the circular dichroism spectrum also provides information about the structure of the sample. For example, if the spectrum shows a symmetrical double-peak shape, there may be a chiral structure. If the spectrum shows a single-peak shape, the sample may be achiral.

 

Interpretation of Structural Changes

By comparing the circular dichroism spectra under different conditions, we can observe changes in the structure of the sample. For example, when the sample is measured at different temperatures, we can observe changes in the peak position, thus inferring the thermal stability of the sample. Similarly, by comparing the circular dichroism spectra at different pH values, we can understand the acid-base stability of the sample.

 

The interpretation of the results of circular dichroism spectrum analysis needs to consider factors such as peak position, peak intensity, peak shape, chromatogram shape, and comparative analysis. By analyzing these indicators comprehensively, we can obtain important information about the structural characteristics, purity, and quality changes of the sample. As an important analytical technique, circular dichroism has a broad application prospect in the field of biopharmaceuticals.