Encapsulation of Myoglobin with a Mesoporous Silicate Results in New Capabilities

Abstract

A metmyoglobin (Fe3+), an oxidized form of myoglobin (Fe2+), was confined in nanospaces of about 4 nm in diameter in mesoporous silica (FSM; folded-sheet mesoporous material), forming a metmyoglobin (Fe3+)-FSM nanoconjugate. The spectral characteristics of metmyoglobin (Fe3+)- and myoglobin (Fe2+)-FSM show an absorption curve quite similar to that of native metmyoglobin, indicating that myoglobin retains its higher-order structure in the pores of FSM. The metmyoglobin (Fe3+)-FSM conjugate had not only a peroxidase-like activity in the presence of hydrogen peroxide (a hydrogen acceptor) and 2,2-azino-bis(3-ethylbenzothiazoline)-6-sulfomic acid (ABTS) or guaiacol (a hydrogen donor) but also an advanced molecular recognition ability enabling it to distinguish between ABTS and guaiacol. Furthermore, the metmyoglobin (Fe3+)-FSM showed the peroxidase-like activity even in an organic media using benzoyl peroxide as the hydrogen acceptor and leucocrystal violet as the hydrogen donor. The simple immobilization of metmyoglobin (Fe3+) into FSM results in enhanced catalytic activity in organic media compared to that of native metmyoglobin (Fe3+).

Proteins in Mesoporous Silicates

“…4 30 kDa [a] FSM-16, CNS 2.7-13 myoglobin [71,127] 7.1 ca. 17.6 SBA-15, FDU-12, MCF 3.8-24 metmyoglobin [128] ca. 17.6 FSM-16, FSM-22 2.7, 4 hemoglobin [109,110] 6.8-7.0 5.3 5.4 6.5 SBA-15, FSM 3-10 conalbumin [2,127] 6.0 5.0 5.6 9.5 SBA-15, MCF, FDU-12 5.9-18 ovalbumin [2] 4.9 4.0 5.0 7.0 SBA-15, MCF 5.9, 16 trypsin inhibitor protein [2] 5.2 14 kDa [a] SBA-15, MCF 5.9, 16 a-amylase [101] ca.…”

“…Of the enzymes immobilized on mesoporous materials, only approximately one third have been examined for their ability to be recycled, and activity losses occur in each cycle in many of these cases. [b] Reuse cytochrome c [64,73,108] no higher enhancedmicroperoxidase-11 [118] no less --lysozyme [84,86] no ---trypsin [41,112,114,126,127] no higher higher [c] enhanced enhanced [c] yes organophosphorus hydrolase [45,91,92] no higher enhanceda-chymotrypsin [57,63,116] no less enhanced yes horseradish peroxidase [62,73] higher [c] enhancedchloroperoxidase [65,90,93,94,106] no less [c] enhanced yes manganese peroxide [66] active enhanced yes papain [27,117] no less enhanced yes pepsin [73] ----bovine serum albumin [71,73] ----subtilisin [62,73] higher [c] enhancedmyoglobin [71,127] ----metmyoglobin [128] higher [c] --hemoglobin [109,110] higher [d] enhanced yes [c]…”

Effective immobilization of subunit protein in mesoporous silica modified with ethanol

“…The encapsulation of proteins into the mesoporous silicate resulted in increased resistance to organic solvents, or surroundings, in comparison with the native (Deere et al, 2001(Deere et al, , 2003Fan et al, 2003;Itoh et al, 2006b;Takahashi et al, 2000;Vinu et al, 2004). Thus, the encapsulation of enzymes in mesoporous materials is likely to be quite useful for establishing new functions and will have wide application to different chemical processes.…”

“…To examine the stability of enzymes, horseradish peroxidase (Deere et al, 2003;Takahashi et al, 2000), cytochrome c (Deere et al, 2001;Vinu et al, 2004), and lysozyme (Fan et al, 2003) have been introduced into mesoporous silica materials (Hartmann, 2005). Quite recently, we have succeeded in the encapsulation of a monomeric unit protein, myoglobin, with a mesoporous silicate, which revealed that the encapsulation brings about new capabilities (Itoh et al, 2006b). Incorporation also seems to increase the stability of the incorporated molecules, and such host-guest reactions should be useful for the arrangement and accumulation of molecules and enzymes.…”

“…In addition, in the case of the MCM type, proteins tend to be immobilized both inside and outside the pores. On the other hand, the interior of the nanometer pores of FSM is expected to provide a suitable environment for proteins similar to that in vivo, because in FSM, proteins seem to be exclusively accommodated into the pores (Itoh et al, 2006b;Takahashi et al, 2000). Thus, as capsules for big subunits proteins, it is very important to obtain FSM with a structure stable in aqueous…”