Binding of an Acetic Acid Ligand to Adenosine:  A Low-Temperature NMR Study

• Published in: Journal of the American Chemical Society 2004-02, Vol.126 (7), p.2135-2141
• Main Authors: Basílio Janke, Eline M, Limbach, Hans-Heinrich, Weisz, Klaus
• Format: Article
• Language: English
• Subjects: Acetic Acid - chemistry; Acetic Acid - metabolism; Adenosine - chemistry; Adenosine - metabolism; Biological and medical sciences; Cold Temperature; Fundamental and applied biological sciences. Psychology; Hydrogen Bonding; Interactions. Associations; Intermolecular phenomena; Molecular biophysics; Nuclear Magnetic Resonance, Biomolecular - methods
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja038630z

Binding of an acetic acid (HAc) ligand to adenosine (A) was studied by 1H NMR spectroscopic techniques. Using a low-melting deuterated Freon mixture as solvent, liquid-state measurements could be performed in the slow exchange regime and allowed a detailed characterization of the formed associates. Thus, at 128 K, trimolecular complexes A·HAc2 and A2·HAc with both Watson−Crick and Hoogsteen sites of the central adenine base occupied coexist in various amounts depending on the adenosine:acetic acid molar ratio. Whereas the carboxylic acid OH proton is located closer to the acid for all hydrogen bonds formed, a more deshielded proton at the Watson−Crick site is evidence for a stronger hydrogen bond as compared to the Hoogsteen interaction. For the binding of acetic acid to an adenosine−thymidine base pair in either a Watson−Crick or a Hoogsteen configuration, hydrogen bonds to the available adenine binding site are strengthened as compared to the corresponding hydrogen bonds in the A·HAc2 complex.