Duplex DNA can be heated to produce the individual nucleic strands while formati

Question

Duplex DNA can be heated to produce the individual nucleic strands while formation of the duplex is thermodynamically spontaneous in the temperature range 25-37°C for most complementary DNA strands as shown below.

List and explain which enthalpic and entropic factors are involved with formation of the double-stranded double helix (‘ds’) from the separate nucleic acid strands in solution. Why is Gds still negative and therefore why does the double helix form at these temperatures?

Explanation / Answer

delta G is the gibbs free energy change.

Whenever the reactants have more free energy than products, the gibbs free energy change becomes negative and hence the process is favourable under given temperature conditions.

For non spontaneous reactions the gibbs free energy change is positive.

The free energy change for the process mentioned above is approximately -21.8 KJ/mol.

The enthalpic and entropic factors associated with 10 nearest neighbour parameters for DNA/ DNA duplexes have been given below, which sum upto negative free nergy change at normal body temperature that isd 37 degree celcius and hence the reaction for the formation of double stranded DNA is spontaneous.

nearest neighbour sequence delta H delta S delta G

5'-3'/ 3'-5' in KJ/mol in J/mol.K in KJ/mol

AA/TT -33.1 -85.4 -4.26

AT/TA -30.1 -85.4 -3.67

TA/AT -30.1 -89.1 -2.50

CA/GT -35.6 -95.0 -6.12

GT/CA -35.1 -93.7 -6.09

CT/GA -32.6 -87.9 -5.40

GA/CT -34.3 -92.9 -5.51

CG/GC -44.4 -113.8 -9.07

GC/CG -41.0 -102.1 -9.36

GG/CC -33.5 -83.3 -7.66

Terminal AT base pair 9.6 17.2 4.31

Terminal GC base pair 0.4 -11.7 4.05

Related Questions

Navigate

• Browse (All)
• Browse D
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.