Nondestructive testing of defects in adhesive joints

(Fei Han et al.,2008) and in turn stabilizes the NPs Increase in surfactant concentration
was not found suitable for nano particle preparation.
3.5 Immobilization of subtilisin on polysaccharide nano particles-EFNP
The enzyme immobilization efficiency of the nano particle was in the range of 45.38 to
70.10 % .b Immobilization of enzyme usually results in the conformational change in the
enzyme resulting in a shift in the optimum pH. The effect of pH on the activity of free
and immobilized protease preparations are given in (Figure 6). The optimum pH of the
native enzyme was at 7.0 and was shifted to pH 8.0 after immobilization. This pH shift
towards alkaline side is due to the secondary interactions between the coupling agent,
enzyme and the polymeric gel matrix. The glutaraldehyde coupling of the matrix with the
enzyme would have linked all the available amino groups on the surface of the enzyme,
and hence the acidic groups on the enzyme surface gives a negative charge to the enzyme
protein, ultimately shifting the optimum pH to the higher side. The protease activity of
native enzyme increased gradually with temperature and a maximum activity was
obtained at 55°C. The immobilized enzyme also showed the same temperature optima.
3.6 Reaction Kinetics of EFNPs compared with native subtilisin
The immobilized enzyme shows a lower K value than the native subtilisin. The
m
higher affinity of the immobilized subtilisin towards the substrate may be due to the
presence of a flexible glutaraldehyde arm, which in turn helps the enzyme to suitably
orient its active site towards the substrate (casein). However the catalytic efficiency of the
immobilized enzyme was found to be lower than that of the native enzyme (Table 4)
Table 4 Kinetic parameters of immobilized NPs and native subtilisin
Enzymee
Native
Immobilized
Km
Moles/ml
1.07x10 -5
4.097x10 -5
Vmax
Moles/s/g
4.21x10 -6
2.89x10 -6
kcat
Moles/s/mole of
enzyme
0.147
0.07611
kcat/Km
1.4x10 4
18x10 2
Particle size of the nano - and micro particles is an important formulation
property that influences other pharmaceutical and cellular uptake properties of the drugs.