Abstract
Natural abundance carbon-13 and proton NMR spectra of bovine chromaffin granules have been obtained and analyzed using computer simulation techniques. High resolution spectra show the presence of a fluid aqueous phase containing epinephrine, ATP and a random coil protein. The protein spectrum conrains unusually intense resonances due to glutamic acid and proline and has been simulated satisfactorily using the known amino acid composition of chromogranin A.
The lipid phase of chromaffin granules gives rise to intense, but very broad, resonances in the carbon-13 spectrum. Protons in the lipid phase are also observable as a very rapid component of the proton-free induction decay (T2 ~- 15 ps).
Linewidths of the carbon-13 spectra have been used to set upper limits on rotational correlation times and on the motional anisotropy in the aqueous phase. These limits show that the aqueous phase is a simple solution (not a gel) that is isotropic over regions much larger than solute dimensions. No gel transition is observed between --3 and 25°C. The carbon-13 spectra are definitely inconsistent with a lipoprotein matrix model and chromaffin granules previously proposed by Helle and Serck-Hanssen ((1975) Mol. Cell. Biochem. 6, 127--146). Relative carbon-13 intensities of ATP and epinephrine are not consistent with the known 1 : 4 mol ratio of these components. This fact suggests that epinephrine and ATP are not directly complexed in intact chromaffin granules.
Keywords
chemistry -- research, biochemistry, analytic chemistry
Date of Authorship for this Version
1977
Volume Number
497
First Page
14
Last Page
28
Repository Citation
Edward P. Richards & Robert R. Sharp, Analysis of the Carbon-13 and Proton NMR Spectra of Bovine Chromaffin Granules, 497 Biochimica et Biophysica Acta 14 (1977).
Comments
497 Biochimica et Biophysica Acta 14 (1977)