Evaluation of instrumental errors built in circular dichroism spectrometers

Abstract

Because of the increased use of circular dichroism (CD) spectroscopy as a routine technique by nonspecialists to determine the conformational/configurational properties of biomolecules, we have decided to present here some criteria to accurately check the ordinate scale calibration of a CD spectrometer particularly in the critical low-wavelength UV region, to understand, and correct, where possible, the potential limitations coming from the hardware. We also analyze some wavelength calibration methods, and some standards for the CD-scale calibration, and we discuss the critical characteristics of current instrumentation affecting measurements. The example of the bovine catalase CD spectrum is considered.

Molecular Structure Determination Using Chiroptical Spectroscopy: Where We May Go Wrong?

“…Similar precautions for ECD measurements on solid samples have been addressed . Although VROA measurements on gel samples have been reported, solid state measurements of VROA have not yet been accomplished, and the presence of artifacts and methods for their reduction in VROA measurements are known .…”

Formulation Design and High-Throughput Excipient Selection Based on Structural Integrity and Conformational Stability of Dilute and Highly Concentrated IgG1 Monoclonal Antibody Solutions

“…This reduction in reproducibility can probably be attributed to a combination of the high viscosity, uneven distribution of chromophores, relative refractive index changes, increased light scattering, and/or absorption flattening. [22][23][24][25] To probe thermal stability, the CD signal was monitored at 217 nm from 10 • C to 87.5 • C and the normalized transitions are illustrated in Figure 2. Antibody at 1 mg/mL undergoes a secondary structure change both in a pH-and temperature-dependent manner (Fig.…”

Mini review: Instrumentation for vibrational circular dichroism spectroscopy, still a role for dispersive instruments

“…Initial VCD instruments were constructed as logical extensions of conventional CD spectrometers. In other words, most CD spectrometers have dispersive optics, with very bright (usually a Xe arc) broadband sources from which wavelengths are scanned by rotation of prisms or gratings and selected by passing the light through narrow slits . Polarized light is obtained with prism polarizers (linear) and converted to circular states by means of a device capable of variable birefringence that could be oscillated to develop a modulated signal.…”

“…In UV‐vis CD instruments that often use photomultiplier (PMT) detection, normalization was usually realized by a variable gain control circuit that keeps the PMT current output at a constant level by varying the high voltage applied. This acts as an internal gain control (having very low added noise), because PMT output currents are proportional to the high voltage …”