Provider: ingentaconnect
Database: ingentaconnect
Content: application/x-research-info-systems
TY - ABST
AU - Fiamingo, Frank G.
AU - Alben, James O.
TI - Photochemical Dissociation in Optically Dense Solutions: Applications to Photolyzed Carboxymyoglobin (Mb⋆CO)
JO - Applied Spectroscopy
PY - 1985-01-01T00:00:00///
VL - 39
IS - 1
SP - 116
EP - 123
KW - Mathematical modeling, photolysis
KW - Methods, analytical
KW - Infrared
KW - UV-Visible spectroscopy
KW - Beer-Lambert relations
KW - Techniques, spectroscopic
KW - Quantum efficiency
N2 - Photodissociation of ligands has made important contributions to the understanding of function and structure of heme proteins. Here we present a theory for photochemical dissociation that is not limited by the assumption of previous analyses of optically thin samples, and apply it to
interpretation of the photodissociated state of carboxymyoglobin (Mb⋆CO). Equations are derived and presented in terms of the effects of absorbance, [log_{10}(*I*
_{0}/*I*) = *A*, the probability of absorption of light quanta per unit surface area], and
the potential for dissociation, *D* (maximum probability of photodissociation per unit surface area; a linear function in time of photolysis), for both monochromatic and polychromatic light sources. When monochromatic light is used, we show that for large absorbances (*A* > 2)
the fractional photolysis increases as (log *D*)/*A*, and may appear to "saturate" even though well below completion. For polychromatic light intensities and absorbances, the theory predicts that the near-infrared tail of the absorbance band of carboxymyoglobin should be sufficiently
transparent to allow the radiation to penetrate the sample, yet still have a significant absorptivity such that complete photodissociation is possible. An optically thick myoglobin-CO sample illuminated with a tungsten lamp was observed to behave somewhere between these two theories. These
theoretical relations may be useful in the analysis of photolysis data from optically dense solutions and as a guide for future experimental design.
UR - http://www.ingentaconnect.com/content/sas/sas/1985/00000039/00000001/art00022
M3 - doi:10.1366/0003702854249367
UR - http://dx.doi.org/10.1366/0003702854249367
ER -