Chemistry Reference
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fractions used were the water-soluble plasma proteins from egg yolk, fraction-
ated by the method of McBee and Cotterill.
11
The fraction was characterized
with two-dimensional SDS polyacrylamide electrophoresis (Figure 1) and the
most abundant proteins were identified with mass spectrometry. These results
are given in Table 2.
The emulsions were made with medium-chain triglyceride (MCT) oil by high-
pressure homogenization at 15 MPa in a laboratory-scale valve homogenizer.
The emulsion surface area was calculated from the Sauter mean diameter of the
emulsions as determined by light diffraction and verified with light microscopy.
For the three OSA-starch samples, the emulsions were prepared at pH 6.0 with
different levels of OSA-starch. For the proteins, two different series of emulsions
were prepared. In the first series of experiments the pH was kept constant at 7.0
and the protein concentration was varied. In the second set the protein concen-
tration was kept constant while the pH was varied between 2.8 and 8.0 at
constant ionic strength. The particle-size distribution of the emulsions was
determined and the amount of adsorbed OSA-starch
13
or protein
14
was obtained
via serum depletion.
The non-adsorbing protein species were determined using one-dimensional
SDS
polyacrylamide electrophoresis.
15
The molar mass and rms radius dis-
tributions of OSA-starch were determined using asymmetrical flow-field flow
fractionation coupled to multi-angle light scattering and refractive index
detection (AsFlFFF-MALS-RI).
16
To allow faster separation, a programmed
cross flow rate was employed. The elution was started at an initial cross flow
Figure 1 Two-dimensional polyacrylamide gel of soluble egg yolk plasma protein. The six
most prominent protein bands, marked by rings, were identified by mass spect-
rometry: (1) ovotransferrin or conalbumin; (2) immunoglobulin G; (3) serum
albumin or
a
-livetin; (3a) truncated serum albumin (residues 1
410); (4) yolk
plasma glycoprotein YGP42; (5) yolk plasma glycoprotein YGP40. The pres-
ence of several spots for most of the proteins is due to differential phosphor-
ylation
(Modified from Ref. 12).
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