Electricity and magnetism in biological systems / D.T. Edmonds.

Format:

Book

Author/Creator:

Edmonds, D. T. (Donald T.)

Language:

English

Subjects (All):

Electromagnetism--Physiological aspects.

Electromagnetism.

Biomagnetism.

Physical Description:

xii, 286 pages : illustrations ; 25 cm

Place of Publication:

Oxford [England] ; New York : Oxford University Press, 2001.

Summary:

On the molecular biological level the only significant forces are electromagnetic, so that ultimately all living processes must be understood in terms of electromagnetic fields and forces. The first half of the present book deals with the theory of electromagnetism using a descriptive and geometrical approach suited to students of biology, chemistry, and biochemistry, including biologically relevant examples where possible. The second half contains biological topics which can serve as applications of the theory for students of chemistry or biology, or as an introduction to biology for students trained in the physical sciences who wish to migrate to biology. Topics include the properties of water and ions in bulk solution and in narrow pores, the Debye Layer, possible mechanisms for a magnetic animal compass, an electrostatic model of a proton/ion counterport, and the semi-classical theory of nuclear magnetic resonance.

Contents:

Part I The Basic Theory

1. Electrostatic fields and voltage 3

1.1 Electricity, magnetism and biology 3

1.2 The sources of electrical forces 4

1.3 The electric field 5

1.4 Representation of electric fields 8

1.5 Gauss's law 9

1.6 Voltage 18

2. How conductors shape an electric field 29

2.1 Electrical conductors 29

2.2 The electric field within a conductor 30

2.3 The electric field surrounding a conductor 33

2.4 The electrical capacitor 37

2.5 The animal cell plasma membrane as a capacitor 39

2.6 The capacitance of a single conductor 40

2.7 The spherical capacitor 41

3. Ionic conductors 46

3.1 Ohm's law of conductivity 46

3.2 Ionic diffusion 48

3.3 Fick's first law of diffusion 51

3.4 Ionic motion in a constant electric field 53

3.5 Ionic motion with both an electric field and a concentration gradient 55

4. Properties of the electric dipole and the application of Gauss's law when dielectrics are present 61

4.1 The electric dipole 61

4.2 The interaction of electric dipoles with electric fields 66

4.3 Induced charges in dielectrics 68

4.4 Gauss's law with dielectrics present 72

4.5 The properties of the electric displacement D 74

4.6 General procedure for solving problems in electrostatics 76

5. The calculation of electric fields and voltages in the presence of dielectrics 81

5.1 The dielectric constant of water 81

5.2 The electric field and voltage of a charged conducting sphere within dielectric material 82

5.3 Electric fields at the interface between two different dielectrics 84

5.4 Capacitors filled with dielectric material 86

5.5 The electrostatic self-energy of an isolated conductor 88

5.6 The extra electrostatic energy of an assembly of charges 91

5.7 The energy stored in an electric field 92

5.8 The cell plasma membrane as a barrier to ions 93

6. Static magnetic fields 100

6.1 The magnetic field and Gauss's law 100

6.2 The interaction of a magnetic dipole and a magnetic field 104

6.3 The magnetic field of a macroscopic current loop 106

6.4 The magnetostatic potential of a magnetic dipole 107

6.5 The magnetostatic potential near a current loop and Ampere's law 108

6.6 The differences between the electrostatic and magnetostatic potentials 112

7. The generation of magnetic fields 119

7.1 The magnetic field around a straight current-carrying wire 119

7.2 The long solenoid 121

7.3 The Biot-Savart Law 123

7.4 The single coil and the Helmholtz pair of coils 125

7.5 Practical coils for the generation of laboratory magnetic fields 127

8. Magnetic polarization of material 132

8.1 Magnetic material 132

8.2 Modification of Ampere's law by induced magnetic moments 133

8.3 Properties of the vector H 138

8.4 Boundary conditions for B and H 139

9. Induced electric and magnetic fields 145

9.1 Faraday's law of induction 145

9.2 An application of Faraday's law 147

9.3 The screening of induced electric fields in biological tissue 149

9.4 The displacement current 150

9.5 Maxwell's equations 152

10. The motion of a charged particle in electric and magnetic fields and relativity 158

10.1 The Lorentz force 158

10.2 The motion of a free charged particle in a static magnetic field 159

10.3 The Larmor theorem 161

10.4 Diamagnetism 164

10.5 Special relativity and magnetism 166

Part II Applications

11. Ions in aqueous solution and the ionization of acids and bases 175

11.1 Ions in aqueous solution 175

11.2 The dissociation of the water molecule and pH 178

11.3 Ionizable residues 179

11.4 The effects of electric fields on the ionization of acid and basic residues 181

11.5 The effects of the electrical polarizability of the environment on the ionization of residues 182

12. The Debye Layer 186

12.1 The basic electrostatics 186

12.2 The electric field and voltage at the surface for a given surface charge density 188

12.3 The variation of voltage with distance from the surface 191

12.4 The variation of ionic concentration with distance from the charged surface 194

12.5 How reliable is the simple theory of the Debye layer? 195

13. The behaviour of ions in narrow pores 197

13.1 Ion channels in biology 197

13.2 The electrostatic self-energy of an ion in a narrow water-filled pore 198

13.3 Enhanced electrostatic interaction within narrow water-filled pores 201

13.4 Interactions between ions and ionizable residues in the pore wall 204

13.5 The possible ordering of the water structure within narrow pores 205

14. Possible mechanisms for a magnetic animal compass 208

14.1 The magnetic field of the Earth 208

14.2 The animal compass 210

14.3 Magnetic induction 211

14.4 The magnetite compass 215

14.5 The free radical magnetic field detector 218

15. An electrostatic model of a proton/ion or an ion/ion coport or counterport 223

15.1 The ionic coport and counterport 223

15.2 A simple mechanical model of a counterport 224

15.3 An electrostatic analogue of the mechanical model for a proton/ion counterport 225

15.4 Kinetics of the model 227

15.5 A Monte Carlo computer simulation 229

16. An introduction to the semi-classical theory of pulsed nuclear magnetic resonance 235

16.1 Classical angular momentum and the Larmor theorem 235

16.2 The rotating frame 237

16.3 Application of a small-amplitude rotating magnetic field and magnetic resonance 239

16.4 The detection of nuclear magnetic resonance, the 90[degree] pulse and the free precession signal 241

16.5 The 180[degree] pulse and the spin echo 244

16.6 Nuclear magnetic resonance as a structural technique on a molecular scale 246

16.7 Nuclear magnetic resonance as a structural technique on a macroscopic scale 248

Appendix 1 Mathematics 251

A1.1 Cartesian and polar coordinates 251

A1.2 The work done by forces and couples 253

A1.3 Vectors 255

A1.4 Vector products 257

A1.5 Vector calculus 258

A1.6 Integrals 259

A1.7 Geometrical vector theorems 262

Appendix 2 The Boltzmann distribution, entropy and detailed balance 263

A2.1 Disorder and the number of available states 263

A2.2 The Boltzmann distribution 265

A2.3 Entropy 266

A2.4 Detailed balance 266

A2.5 An entropic force 268

Appendix 3 An introduction to thermodynamics and the chemical potential 270

A3.1 The first law 270

A3.2 The second law 272

A3.3 The Gibbs function 272

A3.4 Uses of the chemical potential 274

A3.5 The tension in an 'entropic chain' 277

Appendix 4 Hints for the solution of and numerical answers to the problems 279.

Notes:

Includes index.

ISBN:

0198506805

OCLC:

45743303