Measuring the strength of the hydrogen bonds between DNA base pairs is of vital importance for understanding how our genetic code is physically accessed and recognized in cells, particularly during replication and transcription. Therefore, it is important to develop probes for these key hydrogen bonds (H-bonds) that dictate events critical to cellular function, such as localized melting of DNA. The vibrations of carbonyl bonds are well-known probes of their H-bonding environment, and their signals can be observed with infrared (IR) spectroscopy. Yet, pinpointing a single bond of interest in the complex IR spectrum of DNA is challenging due to the large number of carbonyl signals that overlap with each other. Here, we use a method we developed that exploits isotope editing and infrared (IR) spectroscopy to isolate IR signals from thymine (T) C=O carbonyls. We use solvatochromatic and temperature-dependent experiments on model compounds that mimic the T base to show that the T C2=O and T C4=O signal's positions in the IR can be correlated with the enthalpy of individual H-bonds in large DNA duplexes.

Probing the enthalpies of individual hydrogen bonds in DNA duplexes with isotope edited infrared spectroscopy

ACS Fall 2021

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