Abstract
Hemoglobin is examined as a model system for intrinsic photoelectron labeling experiments. The absolute photoelectron quantum yields of hemin, hemoglobin, and apohemoglobin thin films were measured in the 180-230 nm wavelength region. Hemin exhibits a quantum yield of approximately 6 × 10-4 electrons per incident photon at 180 nm, 9 × 10-5 electrons per incident photon at 210 nm, and 2 × 10-6 electrons per incident photon at 230 nm. At all wavelengths the hemin curve lies approximately a factor of 20 above that of hemoglobin and two orders of magnitude above that of apohemoglobin. High image contrast is observed between hemin and apohemoglobin in low magnification photoelectron micrographs, suggesting the feasibility of intrinsic labeling studies involving heme proteins. The quantum yield of hemoglobin is discussed in terms of linear contributions from heme groups and protein weighted by their relative surface areas. The fractional surface areas based on the known structure of hemoglobin are consistent with values derived from the quantum yields of hemin and apohemoglobin.
Full text
PDF
Images in this article
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Birrell G. B., Burke C., Dehlinger P., Griffith O. H. Contrast in the photoelectric effect of organic and biochemical surfaces. A first step towards selective labeling in photoelectron microscopy. Biophys J. 1973 May;13(5):462–469. doi: 10.1016/S0006-3495(73)85999-5. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Dam R. J., Burke C. A., Griffith O. H. Photoelectron quantum yields of the amino acids. Biophys J. 1974 Jun;14(6):467–472. doi: 10.1016/S0006-3495(74)85927-8. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Griffith O. H., Lesch G. H., Rempfer G. F., Birrell G. B., Burke C. A., Schlosser D. W., Mallon M. H., Lee G. B., Stafford R. G., Jost P. C. Photoelectron microscopy: a new approach to mapping organic and biological surfaces. Proc Natl Acad Sci U S A. 1972 Mar;69(3):561–565. doi: 10.1073/pnas.69.3.561. [DOI] [PMC free article] [PubMed] [Google Scholar]