Raman marker bands of metal coordination sites of histidine side chains in peptides and proteins

Abstract

Raman spectra were measured for metal complexes of amino acid histidine and histidine‐containing peptides. The C4=C5 stretching band of the histidyl imidazole ring appears in the 1606–1594 cm‐1 region when the Nτ atom of the imidazole ring acts as a ligand of the metal coordination and the Nπ atom is protonated, whereas it appears in a lower wavenumber region, 1588–1573 cm‐1, when the metal coordination takes place via Nπ with Nτ being protonated. These wavenumbers are generally higher than those of the corresponding Nπ‐ and Nτ‐protonated tautomeric forms of metal‐free histidine. Upon N‐deuteration, the C4=C5 stretching mode shows downshifts of about 25 and 10 cm‐1 for Nτ– and Nπ–metal complexes, respectively. Raman bands at ca. 1430 and ca. 1275 cm‐1 (ca. 1350 and ca. 1265 cm‐1 for N‐deuterated histidine) gain intensity upon binding of metal to Nτ and Nπ, respectively, and they may also serve as markers of the metal coordination site. In the Raman spectrum of a 27mer zinc finger peptide that contains two histidine residues, the C4=C5 stretching band is identified at ca. 1606 cm‐1 in H2O solution and an intense band is observed at 1342 cm‐1 in D2O solution. These observations are consistent with the zinc coordination by the histidyl Nτ atom in the zinc finger. The histidyl Raman marker bands of metal coordination found here may be useful in analyzing metal–histidine interactions in peptides and proteins. © 1998 John Wiley & Sons, Ltd.

Copper selectively triggers β-sheet assembly of an N-terminally truncated amyloid β-peptide beginning with Glu3

“…Both the 1575 and 1636 cm À1 bands are absent from the spectrum of the Cu(II) complex, and instead the C 4 ¼ C 5 stretch of metal-bound histidine is observed at 1591 cm À1 (Fig. 2(B)) [16]. The COO À symmetric stretch of Glu3 and Asp7 is observed at 1404 cm À1 in the Raman spectrum of metal-free Ab 3-9 (Fig.…”

“…A shoulder band at 1575 cm À1 in the spectrum of metal-free solution is assignable to the C 4 ¼ C 5 stretch of the imidazole side chain of His6 (Fig. 2(A)) [16,21,22]. The corresponding band of histidinium is observed at 1636 cm À1 .…”

“…A very sharp amide I band is also observed at $1670 cm À1 in the Raman spectrum of amyloid plaques from AD brain, in which Ab fibrils adopting a b-sheet rich structure are the predominant constituent [15]. Although wavenumber of the amide III band is also sensitive to the peptide backbone conformation [13,14], a band of histidine at $1265 cm À1 is strong in the amide III region [16]. When a protein is dissolved in D 2 O, hydrogens of amide N-H groups exchange with the solvent deuteriums, and the amide III vibrations are shifted from 1320-1200 cm À1 to 1000-900 cm À1 (designated amide III 0 ).…”

Raman spectroscopy of proteins: from peptides to large assemblies

“…This mechanistic study took advantage of previous studies of metal binding to Aˇfragments 57 -60 and the established imidazole (histidine model compound) markers of metal binding. 61 The intensity of the histidine ring mode at 1275 cm 1 has been shown to increase on metal binding to the N-3 atom of the imidazole ring. 61 The wavenumber of the C-4 C-5 bond within the imidazole ring (metal free 1570 cm 1 ) has been shown sensitive to metal binding at the N-1 (¾1600 cm 1 ) and N-3 (1580 cm 1 ) site, respectively.…”

Structural stabilities of metalated histidines in gas phase and existence of gaseous zwitterionic histidine conformers

“…IR spectroscopy has been widely used to investigate histidine structures in proteins as well as in model compounds [17,[41][42][43][44][45][46][47][48][49][50]. Frequency calculations were performed on the most stable CS structures for each of the metal histidine complexes.…”