Circular Dichroism of Biological Macromolecules

Abstract

Circular dichroism, the unequal absorption of right and left circularly polarized light, is a manifestation of optical activity in the vicinity of absorption bands. To the experimental scientist interested in the conformation of macromolecules and in the sensitive response of optical activity to conformational alteration, it offers a relatively new and powerful means of understanding the environment of chromophoric residues. As a tool in the elucidation of electronic spectra, it should be useful to the theoretical scientist in identifying weakly allowed absorption bands as well as in providing rotational parameters which can be compared with the developing theory of optical activity. I have stressed application of circular dichroism, to experimental aspects of protein and nucleic acid conformation in solution. Much is still uncertain in particular quantitative details. However, even these early results shed new light and yield new information on the conformation of these molecules.

An Optical Rotatory Dispersion Investigation of Fungal Laccase

“…The anomalous optical rotatory dispersion curve in the 270-300 nm region, generally associated with the aromatic side chains of the protein [18], was not affected by treatments which reduce Type I Cu2+ or which affect Type 2 Cu*+. It does not seem likely, therefore, that dissymmetric aromatic residues are involved in the non-symmetric binding of Cu2+ in laccase.…”

Effect of Silica Surface Properties on the Formation of Multilayer or Submonolayer Protein Hard Corona: Albumin Adsorption on Pyrolytic and Colloidal SiO2 Nanoparticles

“…The spectrum of native BSA exhibits the expected profile characterized by a positive signal at 192 nm (left-hand polarized π nb →π* electronic transition) and two negative components at 208 nm and 222 nm due to the right-hand polarized π nb →π* and n→π* transitions, respectively. 51,52 The deconvolution of the spectral profile, carried out by CDNN software, resulted in a relative amount of α-helix, β-sheet, and unordered secondary motifs (Table 3, entry 1). Obtained data are consistent with literature ones 53 based on CDSSTR software based on CD spectra of proteins for which high-quality X-ray diffraction data are available.…”

Using circular dichroism collected as a function of temperature to determine the thermodynamics of protein unfolding and binding interactions

“…In the simplest case a molecule undergoes an unfolding transition between two states: folded, F, and unfolded, U. At any temperature, T, the constant of folding, K, is: (1) [F] and [U] are the concentrations of the folded and unfolded forms respectively a The free energy of folding is (2) R is the Gas constant =1.98 cal/mol, and T is the absolute temperature (Kelvin).…”

“…There are numerous reviews on the theory and use of circular dichroism (CD) [1][2][3][4][5][6][7] as well as a website with animated graphics http://www.enzim.hu/~szia/cddemo/, which illustrates the production of circularly polarized light, the circular dichroism of optically active molecules, and how passing plane polarized light through an asymmetric molecule results in the production of elliptically polarized light. An introduction to CD and a description of how to estimate the secondary structure of a protein from its CD spectrum are in the first protocol in this series 8 .…”