Proposed Mechanism for the Formation of M-H~+ in Novel Antineoplastic Curcumin Analogues

摘要

From all experiments shown, a general mechanism for the formation of the [M-H]~+ in curcumin analogues can be proposed: With LD, M·~+ is formed by photoionization, which undergoes hydrogen transfer from another analyte molecule to form [M+H]~+, and the subsequent loss of H_2 yields the [M-H]~+. During MALDI, there is a proton transfer from the matrix to the analyte, yielding the [M+H]~+, and the subsequent loss of H_2 yields the [M-H]~+. The [M+H]~+ ion is more stable in the MALDI FTICR experiments than the LD FTICR experiments. This suggests that ion transfer via the matrix is less exothermic than the LD process described above. The [M]~·- ion is very stable, as it is observed in both the LD and MALDI negative mode analyses. The addition of a radical scavenger did not deplete this peak.