Cation ion specifically induces a conformational change in trans-dehydroandrosterone – A solid-state NMR study

• Solid-state NMR provides a sensitive tool for analyzing cation chelation on DHEA.
• 13C NMR spectra of DHEA/Ca+2 mixtures indicate a conformational change.
• DHEA/Ca+2 mixture reveals a conformational change different from that of DHEA/Mg+2.

In this work, we demonstrated that calcium (Ca+2) is able to induce a conformational change in trans-dehydroandrosterone (DHEA). To this respect, solid-state NMR spectroscopy was applied to a series of DHEA molecules that were incubated with Ca+2 under different concentrations. The high-resolution 13C NMR spectra of the DHEA/Ca+2 mixtures exhibited two distinct sets of signals; one was attributed to DHEA in the free form, and the second set was due to the DHEA/Ca+2 complex. Based on chemical shift isotropy and anisotropy analyses, we postulated that Ca+2 might have associated with the oxygen attached to C17 via a lone-pair of electrons, which induced a conformational change in DHEA. Apart from Ca+2, we also incubated DHEA with magnesium (Mg+2) to determine whether Mg+2 was able to interact with DHEA in a similar manner to Ca+2. We found that Mg+2 was able to induce a conformational change in DHEA deviated from that of Ca+2. These solid-state NMR observations indicate that DHEA is able to interact with cations, such as Mg+2 and Ca+2, with specificity.

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