Question: 4. (30 pts.) The phosphodiester of the DNA backbone has a formal electrostatic charge of -1. a) W…


4. (30 pts.) The phosphodiester of the DNA backbone has a formal electrostatic charge of -1. a) What is the work required to assemble two single helical strands of DNA (each with 5 bases) into a double helix? Assume a Coulomb constant of unity. Is the sign of the work negative (stabilizing) or positive (destabilizing). b) If the Coulomb constant, 1/4TTE (where E is a permittivity of free space), is expressed in the proper units, work will be in units of joules/duplex, and multiplication by Avogadros number gives joules/mole. This number will exceed the -20 joules/mole of work per base due to hydrogen bonding. So what other factors contribute to double-strand DNA stability other than hydrogen bonding? c) An enzyme binds to double-strand DNA, using positively charged side chains to hydrogen bond with the phosphodiester backbone. How is it possible for an enzyme to destabilize the DNA double helix when it is neutralizing the negative charge of the phosphodiester backbone?

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4. (30 pts.) The phosphodiester of the DNA backbone has a formal electrostatic charge of -1. a) What is the work required to assemble two single helical strands of DNA (each with 5 bases) into a double helix? Assume a Coulomb constant of unity. Is the sign of the work negative (stabilizing) or positive (destabilizing). b) If the Coulomb constant, 1/4TTE (where E is a permittivity of free space), is expressed in the proper units, work will be in units of joules/duplex, and multiplication by Avogadro's number gives joules/mole. This number will exceed the -20 joules/mole of work per base due to hydrogen bonding. So what other factors contribute to double-strand DNA stability other than hydrogen bonding? c) An enzyme binds to double-strand DNA, using positively charged side chains to hydrogen bond with the phosphodiester backbone. How is it possible for an enzyme to destabilize the DNA double helix when it is neutralizing the negative charge of the phosphodiester backbone?

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