ABSTRACT
Using model peptides, each of the nine MX2H or HXnM (n = 1, 2) motifs of the silver resistance protein SilE has been shown to coordinate to one Ag+ ion by its histidine and methionine residues with Kd in the µM range. This suggests an Ag+ buffering role for SilE in the case of high Ag+ overload.
Subject(s)
Bacterial Proteins/metabolism , Carrier Proteins/metabolism , Peptide Fragments/metabolism , Silver/metabolism , Bacterial Proteins/chemistry , Binding Sites , Carrier Proteins/chemistry , Drug Resistance, Bacterial/physiology , Glutamic Acid/chemistry , Glutamic Acid/metabolism , Histidine/chemistry , Histidine/metabolism , Methionine/chemistry , Methionine/metabolism , Peptide Fragments/chemical synthesis , Peptide Fragments/chemistry , Protein Binding , Silver/chemistryABSTRACT
A series of naphthaldehydes, including a Mannich base, have been investigated by UV-Vis spectroscopy, NMR and theoretical methods to explore their potential tautomerism. In the case of 4-hydroxy-1-naphthaldehyde concentration dependent deprotonation has been detected in methanol and acetonitrile. For 4-hydroxy-3-(piperidin-1-ylmethyl)-1-naphthaldehyde (a Mannich base) an intramolecular proton transfer involving the OH group and the piperidine nitrogen occurs. In acetonitrile the equilibrium is predominantly at the OH-form, whereas in methanol the proton transferred tautomer is the preferred form. In chloroform and toluene, the OH form is completely dominant. Both 4-hydroxy-1-naphthaldehyde and 4-methoxy-1-naphthaldehyde (fixed enol form) show dimerization in the investigated solvents and the crystallographic data, obtained for the latter, confirm the existence of a cyclic dimer.
ABSTRACT
In the title compound, C20H20N2O2, the quinoline ring system makes dihedral angles of 81.05â (4) and 61.16â (5)° with the mean planes of the benzene and morpholine rings, respectively; the mean planes of the latter two rings make a dihedral angle of 83.59â (4)°. In the crystal, pairs of O-Hâ¯N hydrogen bonds link neighbouring mol-ecules related by a twofold rotation axis, generating R2(2)(10) motifs.
