Visualizing the Invisible : Imaging Techniques for the Structural Biologist.

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Cover; Contents; Preface; Notes for the Reader; PART ONE: Fundamentals; 1. On the Scattering of Electromagnetic Radiation by Atoms andMolecules; 1.1 What is electromagnetic radiation?; 1.2 Atoms are electrically polarized by electromagnetic radiation; 1.3 Oscillating dipoles emit electromagnetic radiation; 1.4 The electrons in atoms and molecules scatter X-rays as though they were unbound; 1.5 The scattering of X-rays by molecules depends on atomic positions; 1.6 Radiation detectors measure energy, not field strength.

1.7 If the radiation being scattered is unpolarized, the polarization correction depends only on scattering angle1.8 The coherence length of the radiation used in scattered experiments affects the accuracy with which I[sub(d)] can be measured; 1.9 Measurement accuracy also depends on transverse coherence length; Problems; Appendix 1.1 Exponential notation, complex numbers, and Argand diagrams; Appendix 1.2 The polarization correction for unpolarized radiation; 2. Molecular Scattering and Fourier Transforms; 2.1 F(S) is a function of three angular variables.

2.2 Fourier series are a useful way to represent structures2.3 In the limit of d = 8, the Fourier series becomes the Fourier transformation; 2.4 The Great Experiment; 2.5 The shift theorem leads to a simple expression for the scattering of molecules; 2.6 The scaling theorem: Big things in real space are small things in reciprocal space; 2.7 The square wave and the Dirac delta function; 2.8 Multiplication in real and reciprocal space: The convolution theorem; 2.9 Instrument transfer functions and convolutions; 2.10 The autocorrelation theorem; 2.11 Rayleigh's theorem; Problems.

3. Scattering by Condensed Phases3.1 The forward scatter from macroscopic samples is 90° out of phase with respect to the radiation that induces it; 3.2 Scattering alters the phase of all the radiation that passes through a transparent sample; 3.3 Phase changes are indistinguishable from velocity changes; 3.4 Polarizabilities do not have to be real numbers; 3.5 Atomic polarization effects are small; 3.6 The frequency dependence of polarizabilities can be addressed classically; 3.7 When the imaginary part of a is large, energy is absorbed.

3.8 The refractive index of substances for X-rays is less than 1.03.9 The wavelength dependences of the processes that control light and X-ray polarizabilities are different; 3.10 On the frequency dependence of atomic scattering factors for X-rays; 3.11 Real X-ray absorption and dispersion spectra do not look the way classical theory predicts; 3.12 The imaginary component of f can be determined by measuring mass absorption coefficients; 3.13 Scattering can be described using scattering lengths and cross sections; 3.14 Neutron scattering can be used to study molecular structure.

Knowledge of the microscopic structure of biological systems is the key to understanding their physiological properties. Most of what we now know about this subject has been generated by techniques that produce images of the materials of interest, one way or another, and there is every reason to believe that the impact of these techniques on the biological sciences will be every bit as important in the future as they are today. Thus the 21st century biologist needs to understand how microscopic imaging techniques work, as it is likely that sooner or later he or she will have to use one or anot.

Includes bibliographical references and index.

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