Correction : Mesoporous titania thin fi lms as e ffi cient enzyme carriers for paraoxon determination / detoxi fi cation : e ff ects of enzyme binding and pore hierarchy on the biocatalyst activity and reusability

a Literature data (ref. 15) where specific activity (SA) is given for the freshly expressed enzyme before lyophilisation. b Lyophilised enzyme contained only approx. 10–20% of His6-OPH, thus the quantity of immobilized His6-OPH is accordingly lower than the determined value, giving approx. 4, 6 and 2 μg of immobilized His6-OPH. These quantities were further used to gain SA (U mgOPH) values. SA was calculated from the Vmax divided by the mass of immobilized enzyme, where we also took into account volume of the reaction mixture and factor 60 to obtain results in correct units, namely U mgOPH . One unit of enzymatic activity (U) was considered as an enzyme concentration hydrolysing 1 μmol of the substrate (paraoxon) per minute at 25 °C.

The original manuscript contained errors in the data of Tables 2 and 3 and in the subsequent discussion of Table 3.The necessary changes are detailed below.
The third column of Table 2 is replaced; the complete table is as follows: Amendments are required to some of the data in column 2 of Table 3.Additionally, columns 4 and 5 of the original table are to be removed and replaced by the new column 4 given below, and footnotes a and b are added to the table.The complete table is as follows:  ) values.SA was calculated from the V max divided by the mass of immobilized enzyme, where we also took into account volume of the reaction mixture and factor 60 to obtain results in correct units, namely U mg OPH −1 . One unit of enzymatic activity (U) was considered as an enzyme concentration hydrolysing 1 μmol of the substrate (paraoxon) per minute at 25 °C.
To reflect the changes to Table 3, amendments are required to the text and one figure within the section 'Performance, stability and reuse of synthesised biocatalyst films'.These corrections are detailed below.
Fig. 3 and its caption should be replaced to correct the wavelength at which absorbance was measured, as follows: In the second paragraph of the section 'Performance, stability and reuse of synthesised biocatalyst films', the first two sentences should be amended as follows: 'Determination of the kinetic parameters for paraoxon hydrolysis by free and immobilized His 6 -OPH demonstrated that depending on the immobilization method (covalent attachment vs. physical adsorption) and mesoporosity (TiF-9 and TiF-13/38) the specific activity (SA) was between 13-17 U mg −1 for covalently bound enzyme, and approx.60 U mg −1 for adsorbed His 6 -OPH (Table 3).When an enzyme was immobilized, regardless of immobilization type or porosity, the K M of immobilized enzyme increased (approx.20-100 times) while the V max decreased (approx.2.5-5 times); meaning that the affinity of the enzyme for its substrate and the velocity of the enzymatic reaction decreased.' In the third paragraph of the section 'Performance, stability and reuse of synthesised biocatalyst films', the final sentence should be amended as follows: 'As expected, K M of immobilized enzyme is higher than that of the enzyme in solution (Table 3), where K M and V max were found to be (0.48 ± 0.02) mM and (0.43 ± 0.02) × 10 −3 mM s −1 for TiF-9, and 0.98 ± 0.07 mM and (0.98 ± 0.1) × 10 −3 mM s −1 for TiF-13/38, respectively.' In the fourth paragraph of the section 'Performance, stability and reuse of synthesised biocatalyst films', the first two sentences should be amended as follows: 'As mentioned before, for both samples the K M increased and V max decreased, where TiF-9 exhibited smaller changes (∼48 times increase of K M and ∼5 times decrease of V max ) in comparison to the free enzyme.Due to the immobilization efficiency (44% and 65%), the specific activities of both samples is approximately the same (Table 3)'.
The fourth sentence of this paragraph is also amended as follows: 'The accumulation of a hydrolysis product, p-nitrophenol, was measured spectrophotochemically at 405 nm.'

Table 2
His 6 -OPH immobilization efficiency and activities

Table 3
Kinetic constants for POX hydrolysis by free and immobilized His 6 -OPH Lyophilised enzyme contained only approx.10-20% of His 6 -OPH, thus the quantity of immobilized His 6 -OPH is accordingly lower than the determined value, giving approx.4, 6 and 2 μg of immobilized His 6 -OPH.These quantities were further used to gain SA (U mg OPH 15)iterature data (ref.15)wherespecific activity (SA) is given for the freshly expressed enzyme before lyophilisation.b