Spectroscopy in Molecular Biology

Molecular biology continues to be the most exciting and dynamic area of science and is predicted to dominate the 21st century. Only by investigating biological phenomena at the molecular level is it possible to understand them in detail. Spectroscopic techniques that monitor the interactions of radiation with molecules are amongst the most useful in molecular biology and are described in the four chapters of this volume. Most commonly used are the absorption and emission of visible and UV light (Chapter 1): excited states, difference spectroscopy, solvent perturbation, fluorescence, phosphorescence, quenching, FRET, reporter groups, luminescence, luciferases, aequorin, green fluorescent protein (GFP), and EXAFS. The interaction of polarized light with molecules depends critically upon their chiral properties and is a very useful probe of molecular structure (Chapter 2): Cotton effects, optical rotation, circular dichroism, and secondary structure of proteins and nucleic acids. The absorption of light by stimulation of the vibrational properties of molecules can be very informative about their structures (Chapter 3): infrared (IR), Raman, and resonance Raman spectroscopies; chiroptical, surface-enhanced and nonlinear techniques. Some of the most important biological reactions are involved in the transfer of electrons from one molecule to another, and this often produces free radicals with unpaired electrons that give the molecules electron magnetic resonance properties (Chapter 4): ESR, EPR and electron magnetic resonance spectra; g-value; hyperfine structure; anisotropy; spin-spin interactions; ENDOR, ESE, ESEEM and ESE-ENDOR techniques; free radicals, nitroxides; nitric acid; spin trapping and labeling; photosynthesis and ribonucleotide reductases. These four chapters were taken from the larger volume The Physical and Chemical Basis of Molecular Biology (2010, Helvetian Press, ISBN 978-0-9564781-0-8).