Resonance Raman assignment and evidence for noncoupling of individual 2- and 4-vinyl vibrational modes in a monomeric cyanomethemoglobin.
We have investigated the resonance Raman spectra of monomeric insect cyanomethemoglobins (CTT III and CTT IV) reconstituted with (1) protohemes IX selectively deuterated at the 4-vinyl as well as the 2,4-divinyls, (2) monovinyl-truncated hemes such as pemptoheme (2-hydrogen, 4-vinyl) and isopemptoheme (2-vinyl, 4-hydrogen), (3) symmetric hemes such as protoheme III (with 2- and 3-vinyls) and protoheme XIII (with 1- and 4-vinyls), and (4) hemes without 2- and 4-vinyls such as mesoheme IX, deuteroheme IX, 2,4-dimethyldeuteroheme IX, and 2,4-dibromodeuteroheme IX. Evidence is presented that the highly localized vinyl C = C stretching vibrations at the 2- and 4-positions of the heme in these cyanomet CTT hemoglobins are noncoupled and inequivalent; i.e., the 1631- and 1624-cm-1 lines have been assigned to 2-vinyl and 4-vinyl, respectively. The elimination of the 2-vinyl (in pemptoheme) or the 4-vinyl (in isopemptoheme) does not affect the C = C stretching frequency of the remaining vinyl. Furthermore, two low-frequency vinyl bending modes at 412 and 591 cm-1 exhibit greatly different resonance Raman intensities between 2-vinyl and 4-vinyl. The observed intensity at 412 cm-1 is primarily derived from 4-vinyl, whereas the 591-cm-1 line results exclusively from the 2-vinyl. Again, there is no significant coupling between 2-vinyl and 4-vinyl for these two bending modes.
Gersonde
K
K
Hauptabteilung Medizintechnik, Fraunhofer-Institut für zerstörungsfreie Prüfverfahren, Saarbrücken, West Germany.
Yu
N T
NT
Lin
S H
SH
Smith
K M
KM
Parish
D W
DW
D000818:Animals; D002683:Chironomidae; D003903:Deuterium; D008706:Methemoglobin / Q000031:analogs & derivatives* / Q000378:metabolism; D011487:Protein Conformation; D013059:Spectrum Analysis, Raman / Q000379:methods; D014732:Vibration; D014753:Vinyl Compounds
D014753:Vinyl Compounds; C007169:cyanomethemoglobin; D008706:Methemoglobin; D003903:Deuterium