Title: Rotating-frame nuclear overhauser enhancement spectroscopy of aqueous solutions with elimination of the water resonance by transverse relaxation
Abstract: The thymopoietin-type tripeptides TP3 (HArg-Lys-AspOH), TP(d-Asp)3(HArg-Lys-d-AspOH) and tetrapeptide TP4 (HArg-Lys-Asp-ValOH) were studied by one- and two-dimensional, 500 MHz 1H-NMR spectroscopy in H2O and D2O solutions at four different pH values. All proton resonances of the three oligopeptides were assigned by two-dimensional phase-sensitive TOCSY experiments at pH 12.2, 9.1, 5.9 and 3.6. At these pH-values well-defined stages of protonation and concomitant molecular charges exist, allowing different possibilities for intra-molecular and inter-residual orientations. Conformation-sensitive rotating frame nuclear Overhauser enhancement (ROESY) two-dimensional experiments were also performed at the above pH values. These experiments indicated no definite solution conformation of any of the molecules at any pH. Standard one-dimensional experiments were also carried out and three-bond coupling constants were measured for the NHCH and the Asp CHCH moieties. The coupling constants provided evidence that non-statistical orientations of the functional groups exist which are changed upon protonation of the basic sites.
Publication Year: 1990
Publication Date: 1990-04-01
Language: en
Type: article
Indexed In: ['crossref']
Access and Citation
Cited By Count: 8
AI Researcher Chatbot
Get quick answers to your questions about the article from our AI researcher chatbot