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DOI: 10.1201/9781003336433-5

5

Detection and

Imaging Tools that Use

Nonoptical Waves

Radio and Microwaves, Gamma and X-​Rays,

and Various High-​Energy Particle Techniques

It must be admitted that science has its castes. The man whose chief apparatus is the differential

equation looks down upon one who uses a galvanometer, and he in turn upon those who putter

about with sticky and smelly things in test tubes.

—​Gilbert Newton Lewis, The Anatomy of Science (1926)

General Idea: In this chapter, we explore many of the detection and sensing tools of biophysics,

which primarily use physical phenomena of high-​energy particles or electromagnetic radiation

that does not involve visible or near-​visible light. These include, in particular, several methods

that allow the structures of biological molecules to be determined.

5.1  INTRODUCTION

Modern biophysics has grown following exceptional advances in in vitro and ex vivo (i.e.,

experiments on tissues extracted from the native source) physical science techniques. At one

end, these encapsulate several of what are now standard characterization tools in a biochem­

istry laboratory of biological samples. These methods typically focus on one, or sometimes

more than one, physical parameter, which can be quantified from a biological sample that

either has been extracted from the native source and isolated and purified in some way or

has involved a bottom-​up combination of key components of a particular biological process,

which can then be investigated in a controlled test tube level environment. The quantification

of these relevant physical parameters can then be used as a metric for the type of biological

component present in a given sample, its purity, and its abundance.

Several of these in vitro and ex vivo techniques utilize detection methods that do not

primarily use visible, or near-​visible, light. As we shall encounter in this chapter, there are

electromagnetic radiation probes that utilize radio waves and microwaves, such as nuclear

magnetic resonance (NMR) as well as related techniques of electron spin resonance (ESR)

and electron paramagnetic resonance (EPR), and terahertz spectroscopy, while at the more

energetic end of the spectrum, there are several x-​ray tools and also some gamma ray

methods. High-​energy particle techniques are also very important, including various forms

of accelerated electron beams and also neutron probes and radioisotopes.

Many of these methods come into the category of structural biology tools. As was discussed

in Chapter 1, historical developments in structural biology methods have generated enor­

mous insight into different areas of biology. Structural biology was one of the key drivers in

the formation of modern biophysics. Many expert-​level textbooks are available, which are

dedicated to advanced methods of structural biology techniques, but here we discuss the core