X‐Ray Spectroscopy on Biological Systems

Abstract

In the field of biological studies, next to the standard methods, new tools are offered by contemporary physics. X-ray spectroscopic techniques enable probing electronic structure of occupied and unoccupied states of studied atom and distinguish the oxidation state, local geometry, and ligand type of elements that occur in biological material. Direct analysis using X-ray spectroscopy avoids many chemical preparation steps that might modify biological samples. The information obtained gives us insight into important biochemical processes all under physiological conditions. In this chapter we focus our attention to the application of X-ray spectroscopy to the study of biological samples, with special emphasis on mechanisms revealing interaction between DNA and different cytotoxic agents and in the determination of changes in oxidation state of different elements in pathologically altered human cells and tissue.

Recent developments of X‐ray absorption spectroscopy as analytical tool for biological and biomedical applications

“…The kβ line holds information to the metal spin state as well as the metalligand covalence; the kβ2,5 line (or VtC area) is more sensitive to the ligands type, electronic structure, and metal-ligand bond length. 6,38 Further details of XES theories and core-level spectroscopy can be found elsewhere 23,[39][40][41] .…”

“…There are three relevant XES spectrometer geometries: von Hamos, Johannson, and Johann. 6 Figure 1 shows an example of setup for XAS-fluorescence measurement using solid-state detector (SSD) and crystal analyzer spectrometer (CAS) in high resolution mode (HERFD). The spectra correspond to the analysis of a Co3O4 sample with a 30-element Ge SSD (total fluorescence yield) and a CAS using five Ge(444) crystals optimized around the Co Kβ1,3 fluorescence line (HERFD).…”

“…In this context, two areas can be distinguished in the XES spectrum of a kβ‐line: the main transition (kβ line) resulting from the transition 3p to 1 s in the metal state and the valence‐to‐core (VtC) transition (kβ2,5 line), resulting of transitions from valence states into metal state 1 s, as the name says. The kβ line holds information to the metal spin state as well as the metal–ligand covalence; the kβ2,5 line (or VtC area) is more sensitive to the ligands type, electronic structure, and metal–ligand bond length 6,38 . Further details of XES theories and core‐level spectroscopy can be found elsewhere 23,39–41 .…”

“…5 XAS requires a high flux beam, which is why it is mainly found at synchrotron sources, and X-rays have high penetration depth. This allows undertaking in situ experiments, with direct observation of the species at the molecular level under conditions maximum close to physiological, as mentioned by Yalovega and Kremennaya, 1 as well as Czapla-Masztafiak et al 6 And in most of the cases without the need for preconcentration. This includes simple systems and more complex one, such as cells and tissues.…”

Bent DNA Bows as Sensing Amplifiers for Detecting DNA-Interacting Salts and Molecules

“…Various techniques have been developed for investigating the interactions between DNA and other molecules, including gel electrophoresis, melting-curve, fluorescence anisotropy, circular dichroism, isothermal titration calorimetry, x-ray absorption spectroscopy, optical tweezers, magnetic tweezers, electron paramagnetic resonance, Raman spectroscopy, and nuclear magnetic resonance spectroscopy [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37]. However, strategies that improve the sensitivity of the existing techniques and methods would be appreciated because they help to identify molecules that interact with DNA too weakly and to make new discoveries [38].…”