13.7 An increase in coupling will increase the energy difference between
the molecular orbitals.13.8 In valence bond theory, a bond is formed when electrons from two
atoms pair up, with σand πorbitals corresponding to s and p atomic
orbitals, respectively.13.9 A peptide bond is formed by the carboxyl group of one amino acid
being joined to the amino group of another amino acid, resulting
in the loss of a water molecule.13.10 The higher dielectric constant decreases the effect of the interac-
tions in water so the strength of the electrostatic interactions is much
greater in benzene.13.11Proteins and DNA are stabilized by the presence of the cumulative
effect of many interactions.13.12 The (φ,ψ) values fall into relatively restricted regions of the plot as
the sterically allowed conformations are limited, with most values
found for the regions corresponding to αhelices and βstrands. The
values for glycine are usually excluded because they frequently fall
outside of the expected ranges.13.13 Membrane proteins form well-defined secondary structures in the
membrane, usually αhelices, which have hydrogen bonds naturally
formed along the backbone.13.14 Hydrogen bonds stabilize secondary structure.13.15 The surrounding amino acid side chains and water molecules will
respond to the presence of a charge and will effectively minimize
the electrostatic interactions.13.16 Answers can include myoglobin and hemoglobin.13.17 The binding of oxygen to the four hemes in hemoglobin is
regulated allosterically by interactions among the four polypeptide
chains.13.18 For any given conformation, the interactions can be calculated and
the energy of that state plotted.13.19These are high-energy states initially formed during protein folding
in which the hydrophobic amino acids collapse together, forming
what will become the interior of the protein.13.20 Velocities are generated by assigning a certain temperature to the
system and then generating a distribution of velocities, the average
kinetic energy of which matches the kinetic energy.472 ANSWERS TO PROBLEMS
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