Biology Reference
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Oxygen Concentration
FIGURE 7-3.
Examples of the noncooperative myoglobin fractional saturation as a function of oxygen
concentration (M) and the positive cooperative hemoglobin fractional saturation as a function
of oxygen concentration (H).
Figure 7-3 depicts typical fractional saturation as a function of O 2
concentration for both myoglobin (M) and hemoglobin (H). Curve M
represents the fractional saturation of myoglobin and curve H a typical
sigmoid-shaped hemoglobin-oxygen fractional saturation curve.
The difference in shapes should not be surprising, as hemoglobin's
complex tetrameric structure allows cooperative interactions that the
simple monomeric myoglobin cannot have.
Our next section presents a brief overview of the history of the
mathematical modeling of hemoglobin-oxygen binding. We should note
that the mathematical modeling of hemoglobin-oxygen binding
developed concurrently with the decoding of the chemical and three-
dimensional structure of the hemoglobin molecule. In many ways, these
parallel efforts have been complementary, with advancements made in
one area accelerating progress in the other.
III. MATHEMATICAL MODELS OF HEMOGLOBIN-OXYGEN
BINDING
As George Santayana noted, ''Progress, far from consisting in change,
depends on retentiveness
Those who cannot remember the past are
condemned to repeat it'' (Santayana [1905]). This is especially true for
scientific research. It is nearly impossible to understand the conceptual
models of hemoglobin-oxygen binding and cooperativity without
understanding the context within which they were developed. The
hemoglobin literature dates back almost 200 years, and almost every
experimental technique used in biophysical chemistry was developed
using hemoglobin. Many of the models of macromolecular
interactions were developed in attempts to describe the functional
properties of the binding of O 2 by hemoglobin. The early literature on
hemoglobin was examined in a wonderful review by Edsall (1972).
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