Biomedical Engineering Reference
In-Depth Information
other transcription factor function. One of the ligands is dexamethazone. To
understand the importance of LBD, a new GR with a mutation in a tyrosine
residue was introduced and binding affinities were measured [9]. Using these
values, det
ermine the change in the binding
affinity.
Bound [fmol]
50
100
200
300
400
Free ligand with wild type GR [nmol]
0.5
1.3
3
6
10
Mutant [nmol]
0.8
2
5
10.5 20
7.5
Warfarin, an anticoagulant, is known to bind to albumin. There are two dif-
ferent binding sites on human serum albumin (HSA) as well as bovine serum
albumin (BSA). To understand the difference in binding characteristics, Sun
[10] measured the binding characteristics of Warfarin to two albumins and
reported the following values.
Warf
free
(
μ
M)
86.3
73.9
61.6
49.3
37
24.6
12.3
6.2
1.2
0.61
0.36
0.12
R
BSA
(%)
4.87
4.74
4.52
3.9
3.68
2.63
1.54
1.01
0.7
0.64
0.48
0.39
R
HSA
(%)
5.57
4.69
3.83
3.39
2.94
2.39
1.58
1.04
0.61
0.48
0.39
0.31
In this table
R
is the average number of moles of ligand bound per mole of
albumin. The absolute amount of BSA and HSA used in the experiment are
2.28 nmol and 1.14 nmol, respectively. Determine the difference in binding
characteristics of the two albumins with Warfarin using: (a) a Scatchard plot
and a nonlinear regression and (b) the Hill equation with the assumption
Alb
+
nW
⇔
Alb
(
W
)
n
.
7.6
Starting with the equilibrium expression for O
2
binding to myoglobin,
O
2
+
pO
MbO
Mb O
2
, derive the equation
Y
=
2
where
Y
is the frac-
pO
+
P
2
50
tional saturation of myglobin.
7.7
The partial pressure of O
2
in the capillaries of active muscle is approximately
20 mmHg.
(a) Calculate the fractional saturation,
Y
, for myoglobin and hemoglobin.
(b) How do these values relate to the function of myoglobin in muscle?
7.8
A pharmacologist testing a new drug determines its effect on oxygen dissocia-
tion of hemoglobin. Under control conditions, when the drug is absent, the
hemoglobin solution is 50% saturated at an oxygen tension of 30 mmHg, and
it is 25% saturated at an oxygen tension of 20 mmHg. Under experimental
conditions, with the drug present, the hemoglobin solution has a P50 of 40
mmHg. Predict the percent difference in saturation of control and experimen-
tal solutions at an oxygen tension of 83 mmHg. Please show your work and
indicate your reasoning.
7.9
Calculate the amount of protein containing a bound ligand assuming a single
binding site with a
K
d
of 10
−6
M, a protein concentration of 10
−6
M and
a total ligand concentration of 10
−6
M. How much is bound if the protein
concentration is reduced to 10
−9
M but the total ligand concentration is
maintained at 10
−6
M (i.e., a thousand-fold greater)? What does this tell you
about the protein concentration required to perform a binding measurement?
