Tu25 - Infrared and Raman spectra of the thymine 13C2 and 13C4 isotopomers in H2O and D2O

Tuesday, October 7, 2025

9:45 AM - 5:30 PM EDT

Location: Exhibit Hall

Presenting Author(s)

AM

Arya Mojahed naghi

PhD Candidate
University of Texas at Arlington (UTA)
Arlington, Texas, United States

Non-Presenting Author(s)

HP

Haoche Peng

PhD in chemistry
Boston, Massachusetts, United States
CS

Charles Philip Shelor

Assistant Professor
University of Texas at Arlington (UTA)
Arlington, Texas, United States
PM

Pavel Matousek

Professor
STFC
Oxford, England, United Kingdom

Project Lead(s)

AS

Allison L. Stelling, PhD

Visiting Scholar
UT Arlington
Richardson, Texas, United States

Submitter(s)

AM

Arya Mojahed naghi

PhD Candidate
University of Texas at Arlington (UTA)
Arlington, Texas, United States

In fifteen words or less, explain the significance of this contribution (Novel Aspect).: Selective 13C labeling reveals localized carbonyl vibrations, sharpening DNA structural probes and interpretative accuracy.

Abstract Text:

The C=O stretching vibrations of nucleobases are used as a probe of DNA and RNA solution state structure in infrared and Raman experiments. The C=O chromophores are of particular interest, as changes to them report on base pair hydrogen bonding. To fully interpret data from these studies, band assignments must be made by measuring isotopomers to observe mass shifts to peaks. To date, thymidine isotopes at each of the carbonyl positions (rather than isotopomers with many atoms replaced with a 13C) have been challenging to synthesize due to the symmetry of thymidine's structure. Here we report the synthesis of two new 13C thymidine isotopomers labeled at the key C=O positions, C2=O and C4=O. We report the first infrared and Raman spectra of each isotope in H2O and in D2O and compare to computational and experimental band assignment proposals for these thymidine vibrations made in previous work. Previous assignments of the two high-frequency modes indicated that the stretches were delocalized over both the C=Os in each peak. Our new isotope shifts indicate these modes are far more localized to the individual carbonyls, making them smaller probes of the surrounding chemical environment than previously thought. This information will help guide future studies that use the vibrations of thymidine to detect structures in DNA and DNA:protein and drug complexes, and determine their mechanisms of binding.