In Chapter 2, we discussed in detail the multi-level architecture of proteins. Like all other molecules, proteins are physical entities that are subjected to the same set of physical forces that dominate our universe. e interplay between proteins and these forces results in folding and formation of the unique architectures discussed in Chapter 2, each with its own unique function. It therefore stands to reason that a true understanding of proteins requires their characterization in terms of forces and energies. is approach is the basis of a speci–c –eld in life sciences termed structural biophysics. e –eld not only contributes to the understanding of protein structure but is also used in various applied areas, such as protein engineering and rational drug design (see Chapter 8). Structural biophysics deals with various physical aspects of proteins but can be separated into two major –elds:

1. Energetics studies the principal forces that a˜ect protein folding and stability. It is the subject of the present chapter, focusing on globular, water-soluble proteins. e energetics of –brous and membrane-bound proteins are covered in Chapters 6 and 7, respectively.