The methyl- trans configuration of the proximal cyclopropane group appears to be a pre-requisite for antigenicity of the hydroxy-MAs (Nos.13 and 14, compared to Nos. 11 and 12, Fig. 5).
The multiscale modeling scheme has been extended to derive the coarse-grained potentials for simulating glass transition temperatures (Tg) of the bulks and the freely-standing films of two stereoregular poly (methyl methacrylate) (PMMA) configurations.
Thus in all the oxygenated MAs (i.e., methoxy-, hydroxy- and keto-MA), the methyl- trans-cyclopropane configuration provides for the best antigenic functionality.
Like the hydroxy-MAs, keto-MAs also require a proximal cyclopropane in the methyl- trans-cyclopropane configuration (No. 5, Fig. 6) to be antigenic, compared to the two cis-cyclopropane configurations (Nos. 4 and 3, Fig. 6) that did not show any significant antigenic activity.
This correlation demonstrates that the oxygenation occurred with retention of the configuration of methyl group CH3-15. 2 was named rickinic acid A. Rickinic acid B (3) has the same molecular formula C15H22O3 as 2, which was obtained by HRESIMS data.
As seen from Fig. 4, the antibody binding signal of R,R-methoxy-methyl cis-cyclopropane MA configuration (No. 8) most closely resembles the response towards the natural mixture of MA.
It would appear that the configuration of the methyl group at C4 controls the reaction process since 4β-methyl-cycloeucalenol was not transformed by a cell-free preparation containing COI, and this selectivity may explain the absence of lanosterol and eburicol in plants generally.
Furthermore, each replicate hit also contained a chiral methyl group with the S configuration at the first variable position.
This shows that the junction of structural features: the α,β-double bond, the side chain in proper geometrical configuration, and the methyl group at the N-terminal amide bond, creates unique properties necessary for the biological action of this peptide.
Each module is known to catalyze decarboxylative condensation of (2 S -methylmalonyl-ACP and the incipient polyketide chain with net inverS -methylmalonyl-ACPn at the methyl-bearing carbon to generate the correS -methylmalonyl-ACPhyl-3-ketoandl-ACP chain elongathen incipientate.
