Selenium-77 and carbon-13 high-resolution solid-state NMR studies of selenomethionine

✍ Scribed by Marek J. Potrzebowski; Rafał Katarzyński; Wodzimierz Ciesielski

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 153 KB
• Volume: 37
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/(sici)1097-458x(199903)37:3<173::aid-mrc423>3.0.co;2-s

✦ Synopsis

77Se cross-polarization magic angle spinning (CP/MAS) and 13C CP/MAS experiments were employed to study the structure and dynamics of DL-selenomethionine (1) and L-selenomethionine (2) in the solid state. The 77Se principal elements of chemical shift tensors and shielding parameters for both compounds were d ii calculated by means of the graphical method of Herzfeld and Berger. An attempt to assign the 77Se to the d ii molecular structure of selenomethionine is presented. From 77Se and 13C NMR it is concluded that the unit cell of 2 contains A and B molecules and 2 is isomorphous with L-methionine. The signiÐcant distinction in side-chain dynamics for A and B molecules is apparent from 77Se measurement (23 and 3.5 s). For 1 77Se is established T 1 T 1 to be 16.5 s. It is found that 2 undergoes a phase transition at 305 K. 77Se CP/MAS revealed that both A and B molecules undergo isomerization and such a process causes changes in the selenium shielding parameters. Similar isomerization is observed at room temperature when the sample is rotated with a spinning rate of 14.5 kHz.