Study Metals in Biological Systems

The study of metals in biological systems requires techniques, some of them highly specific, some limited to specific characteristics of the metal ion in question, some of more general applicability. Thus, Mossbauer spectroscopy in biological systems is restricted to iron-containing systems because the only element with a Mossbauer nucleus available is Fe. The EPR spectroscopic techniques will only be of application if the metal centre has an unpaired electron. In contrast, provided that suitable crystals can be obtained. X-ray diffraction allows the determination of the three-dimensional structure of metalloproteins and their metal centres. 

It is not our intention to describe the techniques in any detail, but rather to indicate what information can be derived from the application of the method in question (and also what cannot). This is motivated in this second edition by the imminent entry into production of a companion volume to the present one Practical Approaches to Biological Inorganic Chemistry (Crichton and Louro, 2012). More detailed information on some of these techniques can be found in Amesano et al., 2005 Banci et al., 2006 Bertini et al., 2005 Campbell Dwek, 1984 Que, 2000 Ubbink et al., 2002. 

Biological Inorganic Chemistry, 2nd Edition. DOI 10.1016/B978-0-444-53782-9.00006-1. Copyright 2012 Elsevier B.V. All rights resCTved. 

Mossbauer spectroscopy Quadrupole coupling, isomer shift For Fe sites oxidation and spin state chemical environment 

Electron paramagnetic resonance (EPR) Quadrupole tensor, nuclear Zeeman splitting, g values, coupling constants, relaxation times Usually for odd electron metal sites probes ground-state wave function at high resolution 

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Chapter 6 Methods to Study Metals in Biological Systems... 

Another useful feature of transition metals in biological systems is the unique battery of physical techniques that can be used to study their structural and electronic properties (electronic properties of transition-metal centers and allow for study of the metal ion without interference from other material in the system. 

In this chapter, the unique features of transition metals in biological systems are discussed from the point of view of structural roles, spectroscopic properties, electron transfer, hydrolytic and redox catalysis, and metal-responsive gene expression. The following chapters provide more detail on these subjects. Several important examples not discussed elsewhere in this volume will be presented. The goal of this chapter (and this volume) is to acquaint the reader with the wide range of roles played by metal ions in biological systems and thereby to demonstrate why metals are such useful cofactors and why scientists from such broad disciplines are drawn to study their properties. 

Perhaps the most important area of biochemistry in which ESR is used is the study of metalloproteins. Transition metals in certain oxidation and spin states have unpaired electrons, are paramagnetic, and in many cases are amenable to ESR spectroscopy. The most commonly found transition metals in biological systems are iron, copper, molybdenum, cobalt, and manganese. The remainder, including metals such as vanadium and... 

Despite their crucial role in life, the trace metals make up only a tiny fraction of the human body-weight (Table 28.1). In this chapter we look at the ways in which living systems store metals, and the manner in which trace metal ions take part in the transport of molecules such as O2, electron transfer processes and catalysis. It is assumed that the reader has already studied Chapters 19 and 20, and is familiar with the general principles of J-block coordination chemistry a study of the trace metals in biological systems is applied coordination chemistry. 

One of the main problems in using NMR to study the alkali metals in biological systems is that the chemical shifts of the aqueous ions are essentially independent of the ion s surroundings in all cases except for i Cs% making differentiation of intra- and extracellular cations difficult. This problem can be met by... 

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