Chemistry Reference
In-Depth Information
All-
trans
zeaxathin
OH
HO
O
N
O
O
N
O
O
-
O
-
14-SASL
16-SASL
O
O
O
-
O
-
7-SASL
9-SASL
OO
N
O
N
O
O
O
-
O
O
O
P
O
-
O
O
O
O
5-SASL
O
T-PC
N
O
N
+
O
O
N
O
-
O
-
O
O
O
O
O
P
P
O
O
O
O
O
O
7-PC
5-PC
O
O
N
+
N
+
N
N
OO
OO
O
O
O
-
O
O
O
-
O
O
P
P
O
O
O
O
O
O
10-PC
12-PC
O
O
N
+
N
+
O
O
OO
N
OO
N
O
-
O
-
O
O
O
O
P
P
O
O
16-PC
O
O
O
O
14-PC
O
O
N
+
N
+
O
O
O
N
O
N
O
O
O
-
O
-
O
O
O
O
P
P
POPC
O
O
O
O
DMPC
O
O
O
O
N
+
N
+
O
O
Head
group
region
Head
group
region
Aqueous
phase
Aqueous
phase
Hydrocarbon phase
FIGURE 10.1
Chemical structures of selected spin labels 1-palmitoyl-2-(
n
-doxylsrearoyl) phosphatidylcho-
line (
n
-PC), tempocholine-1-palmitoyl-2-oleoylphosphatidic acid ester (T-PC), and
n
-doxylstearic acid spin
label (
n
-SASL). Chemical structures of dimyristoylphosphatidylcholine (DMPC), dipalmitoylphocphatidyl-
choline (POPC), and zeaxanthin are included. Approximate locations of these molecules across the lipid
bilayer membrane are also illustrated. However, since alkyl chains tend to have many
gauche
conformations,
the chain-length projection to the membrane normal would be shorter than depicted here and the rigid struc-
ture of zeaxanthin would sink somewhat differently in the liquid-crystalline phase membranes.
10.2 HANDLING THE SAMPLE FOR EPR MEASUREMENTS
The membranes used in EPR measurements are usually multilamellar dispersions of lipids (mul-
tilamellar liposomes) containing an investigated carotenoid and 0.5-1.0 mol
%
of an appropri-
ate lipid spin label (Figure 10.1). The total amount of lipids usually is 5-10
μ
mol per sample.
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