The Effect of Calcium and Halide Ions on the Gramicidin A Molecular State and Antimicrobial Activity.

Gramicidin A (gA) forms several convertible conformations in different environments. In this study, we investigated the effect of calcium halides on the molecular state and antimicrobial activity of gramicidin A. The molecular state of gramicidin A is highly affected by the concentration of calcium salt and the type of halide anion.

Magnesium and calcium reveal different chelating effects in a steroid compound: A model study of prednisolone using NMR spectroscopy.

In this work, we used high resolution NMR spectroscopy to investigate metal cation chelation by the steroidal drug 1,4-pregnadiene-11β,17α,21-triol-3,20-dione (Prednisolone; abbreviated as Prd). Prd/MgCl and Prd/CaCl mixtures were prepared at eight different molar ratios. Using two-dimensional H/C heteronuclear correlation spectroscopy, we were able to resolve most of the H signals, except those at 1.

Solid-state NMR investigation of effect of fluorination and methylation on prednisolone conformation.

Prednisolone (Prd) is a polymorphous synthetic corticosteroid that has three crystalline forms mediated by different solvents. In this study, we have demonstrated that solid-state {(1)H}(13)C cross-polarization/magic angle spinning (CP/MAS) NMR spectroscopy is able to resolve the effects of methylation and fluorination on the conformation of the steroidal rings in Prd. Two compounds were chosen for the study, 6-α-methylprednisolone (Prd-6M) and 6-α-fluoroprednisolone (Prd-6F).