Biomolecule folding

Biomolecules Fold to Position Polar Charged Groups on Their Surfaces... 

Figure 19.21 A bumpy energy landscape, such as occurs in some diffusion processes, polymer conformational changes, and biomolecule folding. A single minimum in the center may represent product, but there can be many different reactants, such as the many open configurations of a denatured protein. KA Diii and HS Chan, Nat Struc Biol 4, 10-19 (1997).

The application of ROA to studies of unfolded and partially folded proteins has been especially fruitful. As well as providing new information on the structure of disordered polypeptide and protein sequences, ROA has provided new insight into the complexity of order in denatured proteins and the structure and behavior of proteins involved in misfold-ing diseases. All the ROA data shown in this chapter have been measured in our Glasgow laboratory because, at the time of writing, ROA data on typical large biomolecules had not been published by any other group. We hope that this review will encourage more widespread use of ROA in protein science. 

These factors make 125I the iodine label of choice for radiolabeling biological molecules. Its commercial availability from a number of suppliers at relatively low cost further adds to its popularity. Even though it has lower specific activity than 131I, iodine-125 still provides much greater sensitivity than 14C, 32P, 35S, or 3H in labeling biomolecules. In fact, the use of a radioactive iodine label can create probes that have 150-fold more sensitivity than tritiated molecules and as much as 35,000 times the detectability of 14C-labeled molecules (Bolton and Hunter, 1986). 

T he enormous structural diversity of proteins begins with the amino acid sequences of polypeptide chains. Each protein consists of one or more unique polypeptide chains, and each of these polypeptide chains is folded into a three-dimensional structure. The final folded arrangement of the polypeptide chain in the protein is referred to as its conformation. Most proteins exist in unique conformations exquisitely suited to their function. It is the availability of a wide variety of conformations that permits proteins as a group to perform a broader range of functions than any other class of biomolecules. 

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