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Complexes with bulky hydrotris(triazolyl)borate (Ttz) ligands, TtzCuCO, were used to probe how acids change the donor properties of Ttz ligands. (TtztBu,Me)CuCO shows four distinct protonation states and a gradual increase in the CO stretch. The increased electrophilic nature of the Cu center upon protonation leads to enhanced C–H activation catalysis. [ABSTRACT FROM AUTHOR]

Raman spectroscopy has positioned itself as an invaluable tool in the study of complex biological systems, consistently being used to obtain information illustrating a vast array of fundamental properties. Of primary interest, with respect to the focus of this chapter, are conformational changes of peptide backbones. For short peptides to larger biological systems this understanding can be extended to local hydrogen bonding interactions and the probing of other structural or organizational properties. With regard to unfolded peptides Raman spectroscopy can be used as a technique complementary to infrared (IR) and vibrational circular dichroism (VCD) spectroscopy. This chapter describes how high quality polarized Raman spectra of peptide can be recorded with a Raman microspectrometer and how the structure sensitive amide I band profiles of isotropic and anisotropic Raman scattering can be analyzed in conjunction with the respective IR and VCD profiles to obtain conformational distributions of short unfolded peptides.

Vibrational circular dichroism (VCD) spectroscopy is an invaluable spectroscopic techniques utilized to exploit the optical strength of vibrational transitions for structure analysis. In this chapter, we describe the protocol for measuring and self-consistently analyzing VCD and the corresponding FT-IR spectra of short peptides. This process involves the decomposition of the IR spectrum as well as simulations of the amide I band profiles in both spectra based on structural models of the peptides investigated. This type of spectral analysis should be complemented with similar investigations of Raman spectra, which are described in the subsequent chapter. The structural analysis of short, unfolded peptides described in this chapter can easily be extended for the analysis of longer unfolded peptides or even proteins. This is particularly important in view of the demonstrated biological relevance of intrinsically disordered peptides and proteins (IDPs).

Over the last 50 years cytochrome c has been used as a model system for studying electron transfer and protein folding processes. Recently, convincing evidence has been provided that this protein is also involved in other biological processes such as the apoptosis and α-synuclein aggregation. Numerous lines of evidence suggest that the diversity of the functional properties of cytochrome c is linked to its conformational plasticity. This chapter introduces circular dichroism and absorption spectroscopy, as an ideal tool to explore this protein's conformational in solution. Besides assisting in distinguishing different conformations and in obtaining the equilibrium thermodynamics of the transitions between them, the two spectroscopies can also be used to explore details of heme-protein interaction, for example, the influence of the external electric field on the prosthetic heme group., (Copyright © 2009 Elsevier Inc. All rights reserved.)