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Intermolecular Forces




Experiments with ribonuclease originally showed that if denaturing chemicals are removed, many proteins will regain their native shape and activity. This was important in the history of biology because it showed that secondary and tertiary structure are determined by primary structure. Although there are complex exceptions in cases such as post-translational processing, for most proteins, all the information necessary for the protein to assume its native state is encoded in the DNA.

Work, Energy, and Power


Intermolecular Forces


Chemical Thermodynamics and the Equilibrium State




The Musculoskeletal System


Solubility effects are important in determining the tertiary structure of globular proteins in aqueous solution. The nonpolar, hydrophobic groups push away from the water toward the interior of the protein while the polar groups pull outwards towards the surface where they are solvated by the water. The hydrophobic interior space formed is often essential for catalytic or binding function. For example, in myoglobin the only polar residues on the inside are two histodines. Like a given amount of charge on a capacitor without dielectric has a higher voltage, being surrounded and protected by nonpolar moeities activates the polarity of the histidine residues, which is essential for oxygen binding. This structural motif, is known as the 'globin fold', is also found in hemoglobin α and β chains and in which a nested heme group transports or stores oxygen reversibly.

Coordination Chemistry


One important aspect of protein structure are attached prosthetic groups or coordinated metal ions. Metalloenzymes are proteins with coordinated metal ions that are essential for enzyme activity. Examples include carbonic anhydrase and carboxypeptidase A, which contain coordinated zinc.



Wave Optics

X-ray crystallography is a powerfully important technique for the elucidation of protein structure, revealing the three-dimensional relationships of the atoms in a protein molecule. The first protein structure solved by x-ray crystallography was Sperm Whale myoglobin in 1958. Since that time, tens of thousands of protein structures have been successfully elucidated.

In X-ray crystallography, the interference pattern produced by X-rays reflecting off the closely spaced lattice of atoms in a crystal is recorded and then analyzed to reveal the nature of that lattice. The spacing in the crystal lattice can be determined using Bragg's law, which describes the relationship between the x-ray wavelength, lattice spacing, and the phase shifts corresponding to constructive interference.

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