Circular Dichroism

Method Introduction

The signal obtained from circular dichroism (CD) measurements (ellipticity) arises from differences in absorption by chiral molecules of left- and right-handed circularly polarized light.

Near-UV CD measurements are obtained over a wavelength range of about 250-300 nm, where tyrosine, tryptophan, phenylalanine residues, and disulfide bridges absorb light and are CD-sensitive. Near-UV CD signals largely depend on these residues’ relative orientation and local mobility. Consequently, near-UV CD measurements can provide information about changes in the tertiary structure of proteins, e.g., because of formulation conditions, elevated temperature, or storage.

For proteins, Far-UV CD measurements are obtained using circularly polarized light over a wavelength range of about ≤ 200-250 nm. Light absorption in this wavelength range is mainly due to absorption by the peptide bonds. Since each type of secondary structure element (such as α-helix, β-sheet, etc.) has a distinctive spectral CD profile, Far-UV CD is sensitive to changes in the secondary structure. For instance, Far-UV CD measurements can be performed in different solution conditions (pH, excipients, etc.) to determine the effects on a given protein’s secondary structural content. Also, secondary structures can be estimated compared to library/database information.

Applications

Circular dichroism (CD) measurements are most commonly used to determine changes in the secondary and tertiary structure of proteins, but they can also be applied to other biomolecules.

Quality and Biosafety Level

We provide all our analytical services with the highest quality standards. Experienced scientists carry out each project, and a scientific reviewer comprehensively checks every report or data presentation.

We offer this technology with the following quality and biosafety levels:

R&D level

We offer this method under R&D. Our GRP system assures the highest-quality research standards.

Up to biosafety level 1

This method can be applied to proteins, nucleic acids, and most viral vectors, including AAVs and more.

Analytical Method Development, Qualification and Validation

For common sample types, we can often apply standardized methods with little setup effort. However, when needed, our experienced analytical experts create or optimize custom methods tailored to your active pharmaceutical ingredient, product type and development phase.

Method Development

Our method development approach tailors sample preparation, method settings and data analysis to the needs of your project and sample.

We include representative samples and, where available, suitable reference standards and stressed/degraded materials, allowing our analytical scientists to design a highly suitable, stability-indicating, robust and repeatable method. Upon request, we will compile a detailed description of the method for your records.

Method Qualification

Method qualification is the initial assessment of an analytical procedure’s performance to show its suitability for its intended purpose.

During method qualification, our analytical scientists perform documented testing demonstrating that the analytical procedure meets criteria in several categories. Criteria may include factors such as repeatability, specificity and robustness. We compile a qualification plan and report, including all relevant data.

Method Validation

Under GMP conditions, method validation confirms that an analytical procedure’s performance suits its intended purpose. Depending on the method’s scope, a broad range of method characteristics, such as specificity, accuracy, precision, limit of detection/limit of quantification (LOD/LOQ), linearity and range, is considered.

During method validation, our analytical scientists perform documented testing demonstrating that the analytical procedure consistently produces a result that meets the predetermined acceptance criteria. We compile a validation plan and report that includes all relevant data.

Depending on the development phase, a fit-for-purpose validation approach can be offered, adjusting the validation required efforts in a phase-appropriate way to meet the method’s needs.

Method Verification

Compendial method verification confirms that a compendial method (e.g., from Ph. Eur. or USP) is suitable and reliable for its intended purpose under the specific conditions of the laboratory.

Unlike full method validation, compendial method verification is often considered a partial validation since the method has already undergone extensive testing and validation during its inclusion in the compendium. The extent of method verification depends on the type of method.

During method verification, our analytical scientists perform documented testing demonstrating that the developed analytical method performs adequately for the specific product or matrix being tested and within the specific laboratory where the method will be employed.

Talk to Our Experts or Request a Quote

Our expert team is ready to answer your questions and guide you to the services best suited to your program’s modality, stage and challenge. If your needs are well-defined, we’ll begin the quotation process.

Related Services

Higher Order Structure – Overview Circular dichroism (CD) Differential scanning calorimetry (µDSC) Dynamic Light Scattering (DLS) Fluorescence spectroscopy Fourier transform infrared (FTIR) spectroscopy High-performance size-exclusion chromatography (HP-SEC) Liquid chromatography coupled mass spectrometry (LC-MS) Nano differential scanning fluorimetry (nanoDSF / nDSF)

Enter a term to search