Studying the stereostructures of biomolecules and their analogs by vibrational circular dichroism

Abstract

The functions of biomacromolecules are largely governed by their stereostructure (i.e., configuration and conformation). Therefore, detailed understanding of their structural properties should help in regulating the functions of artificial macromolecules. However, studying the stereostructure of a molecule in the solution state is typically difficult due to the lack of suitable analytical techniques. Vibrational circular dichroism (VCD) spectroscopy, which measures circular dichroism in the infrared region, exhibits high sensitivity toward molecular stereostructures. In this paper, we first discuss a method for the elucidation of the stereostructures of small to large molecules based on theoretical calculations of VCD. The rest of the paper is dedicated to the applications of a VCD exciton chirality method, a novel approach recently developed by the authors to interpret VCD data by observing a VCD couplet in the C = O stretching region, to various biomolecules such as peptides, carbohydrates, polyesters and lipids.

Exploring potentialities and limitations of stapled o‐oligo(phenyleneethynylene)s (o‐OPEs) as efficient circularly polarized luminescence emitters

“…To gain further information and to test the theoretical conformational study, we considered also the use of VCD spectra . Vibrational circular dichroism is very sensitive to conformations of compounds in solution and to conformational mobility, because of the fact that vibrational chiroptical response can reflect also local differences and may heavily depend on hindered torsions .…”

“…To gain further information and to test the theoretical conformational study, we considered also the use of VCD spectra. [33][34][35][36][37][38][39][40][41][42][43][44][45] Vibrational circular dichroism is very sensitive to conformations of compounds in solution and to conformational mobility, because of the fact that vibrational chiroptical response can reflect also local differences and may heavily depend on hindered torsions. [33][34][35] Therefore, VCD gives relevant structural information about the sample in solution, which in many cases cannot be inferred from other spectroscopic techniques.…”

Modifying oligoalanine conformation by replacement of amide to ester linkage

“…21 Meanwhile, to the best of our knowledge, there has been no study on the conformations of oligopeptides containing di-and longer oligo(Lac)s. Recently, the solution conformation of poly(L-Lac), a biodegradable thermoplastic polyester, was studied by Ho′s and our groups by means of vibrational circular dichroism (VCD) spectroscopy. 22,23 A negative-positive VCD couplet at around 1760 cm −1 observed under several conditions suggested that poly(L-Lac) adopts a fairly stable left-handed 10 3 -like helix in solution, [23][24][25] unlike multiconformational oligoalanines. Moreover, conformational studies on several oligo(L-Lac)s indicated that 4 ester linkages are sufficient to fix their helicity.…”

Analysis of Molecular Configuration and Conformation by (Electronic and) Vibrational Circular Dichroism: Theoretical Calculation and Exciton Chirality Method

“…Less than 20 g of a sample has been sufficient for observing its VCD couplet in some cases. 10 The use of this method is also effective for structural analysis of complex systems such as macromolecules and supramolecules (for example, see section 4.6), 38,46 as pointed out also by Abbate et al 47 The subsequent sections describe examples of the use of the VCD exciton chirality method reported by the author and coworkers. Applications by other researchers are to be discussed elsewhere, and not discussed in this account.…”

“…This work also analyzed the structure of a supramolecular PLLAamylose complex, a biodegradable material; the conformation of PLLA was shown to be mostly maintained within the cavity of amylose. 38,46 Applications of the VCD couplet approach for other macromolecules and supramolecules will be reported in due course.…”