High-pressure liquid chromatography and field desorption mass spectrometry of heme alpha, heme alpha dimethyl ester and acetyl heme alpha dimethyl ester

Simultaneous determination of hemes a, b, and c from pyridine hemochrome spectra

Two procedures for analyzing overlapping optical spectra of mixtures of pyridine hemochromes are described, and extinction coefficients of pyridine hemochromes are provided for use with these methods. In the first procedure, absorbance is measured at a number of wavelengths equal to the number of components to be analyzed. This is the minimum amount of spectral data from which the concentration of each species can be calculated. In the second procedure, absorbance is measured at a number of wavelengths greater than the number of components to be analyzed. This redundancy of information makes it impossible to fit spectra which contain contributions from additional components, unless the spectra of the additional components are equal to linear combinations of the spectra of the species being analyzed. These two procedures are generally applicable to analyses of absolute or difference spectra of mixtures of components obeying Beer's law. The sensitivity to error in the absorbance measurements is only slightly greater than that for measuring a pure component at a single wavelength.

Reactivities of hydroxylamine and sodium bisulphite with carbonyl-containing haems and with the prosthetic groups of the erythrocyte green haemoproteins

The reactivities of alkaline NH(2)OH and neutral NaHSO(3) with carbonyl and olefinic groups conjugated with the tetrapyrrole nucleus of haems were studied. The reactions were carried out with 2-3nmol of haem a, spirographis haem, isospirographis haem, 2,4-diacetyldeuterohaem and protohaem. Vinyl side chains were found to be insensitive to the chemical action of both alkaline NH(2)OH and neutral NaHSO(3). The formyl-containing haems reacted rapidly with both reagents at room temperature, as evidenced by sizable hypsochromic shifts of the reduced pyridine haemochrome spectrum. In less alkaline solution, the reactions of these formyl-containing haems with NH(2)OH were much slower. 2,4-Diacetyldeuterohaem reacted with alkaline NH(2)OH, but not with neutral NaHSO(3). These rapid, simple and straightforward tests are readily usable in differentiating among formyl, acetyl and other electron-withdrawing side chains conjugated with the tetrapyrrole ring of haems. We applied these observations to an investigation of the two unique prosthetic groups of the bovine erythrocyte green haemoproteins. The prosthetic groups of these two proteins were isolated and spectrally characterized. Under the conditions used, the haems did not react with either NH(2)OH or NaHSO(3), but were altered by dithionite, suggesting that the previous interpretation that a formyl group was present [Hultquist, Dean & Reed (1976) J. Biol. Chem.251, 3927-3932] may have been premature. These studies also provide evidence that the alpha-hydroxyfarnesylethyl side chain of haem a affects the alpha-band maximum, but not the beta- or Soret bands of the reduced pyridine haemochrome spectrum of haem a.