LO $5\mathrm{.}0-$ Q$2$ An extra$-$large analog of adenosine $($ xA $,$ below$)$ has been prepared and characterized in duplex DNA with regular thymine as a pairing partner. The hydrogen bonding pattern is identical to that seen in regular DNA and a right$-$handed double helix is formed. Data related to the stability of a duplex containing AT base pairs only $($DNA$)$ and $\backslash ($ x A $\backslash$bullet T $\backslash )$ base pairs only $($ DDNA $)$ are likewise shown below. The thermodynamic parameters are given for duplex formation.

Discuss the thermodynamics of xDNA relative to regular DNA in the questions below

a$.$ Which duplex is more stable? What evidence supports that finding.

b$.$ Briefly suggest an explanation for the difference in the $\backslash (\backslash$Delta $\backslash$mathrm$\{$S$\}\backslash )$ of helix formation observed with the two variants of DNA.

c$.$ Consider a single $\backslash ($ x A $\backslash$bullet T $\backslash )$ base pair embedded in a normal DNA duplex. How would the $\backslash (\backslash$Delta H $\backslash )$ and $\backslash (\backslash$Delta $\backslash$mathrm$\{$S$\}\backslash )$ of helix formation likely be affected $($more $\backslash (+/-\backslash ))?$ Provide brief explanation for your answers below.

$\backslash (\backslash$Delta $\backslash$mathrm$\{$H$\}\backslash )$ :