Biology Reference
In-Depth Information
endogenous or exogenous lipids [3]. The functionality of emulsifiers
in starch-containing systems is often related to complex formation
with amylose, and thus, explains the importance of the resultant
complexes [4-7].
10.2
Phosphorylase-Catalyzed Synthesis and
Molecular Assembly of Amylosic Block
Copolymers
Amylosic diblock copolymers were synthesized by phosphorylase-
catalyzed polymerization using the polymeric primers having
a maltooligosaccharide moiety at the chain end. For example,
amylose-
-polystyrenes were produced by covalent attachment
of maltoheptaose derivatives to end-functionalized polystyrene and
subsequent enzymatic polymerization [8-10]. As one of the methods
to produce such block copolymers, maltoheptaose was attached by
reductive amination to amine-terminated polystyrene (Fig. 10.1) [9].
The phosphorylase-catalyzed polymerization could be started even
though the primer-modified polystyrenes were insoluble in citrate
buffer of the polymerization medium. The kinetics of the enzymatic
polymerization showed an interesting dependence on the molecular
weight of polystyrene owing to the micellar structure of the primer
in water.
block
-polystyrenes with
various compositions were investigated in water and THF using
fluorescence correlation spectroscopy, dynamic light scattering
(DLS), and asymmetric flow field-flow fractionation with multiangle
light-scattering detection [10]. The analytical data indicated the
presence of unimers, oligomers, and large micellar species in THF. Up
to four different species were detectable by DLS with hydrodynamic
radii ranging from a few nanometers to >10
Micellar aggregates of the amylose-
block
m, indicating that the
system was not in a thermodynamic equilibrium state. Collapsed
aggregates were monitored on a silicon surface by scanning force
microscopy and transmission electron microscopy. In water, crew-
cut micelles were obtained from the same block copolymers by a
single-solvent approach, elevated temperature and pressure. These
crew-cut aggregates were much more uniform than the respective
star aggregates in THF.
ยต
Search WWH ::




Custom Search