Spectroscopic Analysis: Deoxyribonucleosides and DNA

Chirality plays a primary role in nature and has immense importance in the chemical processes of all living organism, since most biomolecules (DNA, proteins, sugars) are chiral. Chiral molecules have the ability to rotate polarized light, which can be measured using circular dichroism spectroscopy, among other methods. In order to illustrate the multiple types of chirality, DNA was used as a study molecule. DNA is arguably the most important biomolecule, coding for the genetic composition of most organisms. Thus, it is highly desirable to gain a good understanding of DNA structure and properties. DNA is built of chiral nucleosides (sugar-based building blocks), and the stereochemistry of the DNA building blocks influences the DNA secondary structure. Three spectroscopic experiments were conducted to ensure the full understanding of chirality. The first experiment demonstrated the chirality of the DNA nucleosides, by studying the D and L enantiomers. The second experiment studied how the chirality of the building blocks influences the secondary structure (helicity) of the DNA duplex, by comparing left- and right-handed B-DNA and Z-DNA helices, respectively. In the third experiment, the importance of chirality in DNA binding and recognition was illustrated using a non-chiral cationic water-soluble porphyrin.