Remediation of polycyclic aromatic hydrocarbons (PAHs) in oily sludge has become the focus of attention. UV spectrophotometer analysis showed that four types of PAHs were found in sample, which including phenanthrene, anthracene, benzo( a )anthracene and benzo( b )fluoranthene. In order to degrade PAH effectively, the laccase reverse micelles system was proposed. The system protects laccase from being affected by organic phase. Reverse micelles were prepared by using isooctane to simulate oil. The optimum water content W 0 was 10 by measuring the electrical conductivity of the system. Under this condition, the effects of pH, temperature and ionic strength on the degradation rate of PAHs were investigated. Also, compared with that of non-immobilized laccase, the ratio between the secondary structures of laccase under different conditions was studied. The results showed that the highest laccase activity was obtained at pH 4.2 and 30 °C with 60 mmol/L KCl. Meanwhile, the structure of α-helix accounts for the largest proportion, and the ratio of α-helix in the laccase secondary structure in the laccase-reverse micelle system was higher than that of the non-immobilized one under this condition. Finally, predicting the reactive site of the degradation of polycyclic aromatic hydrocarbons was simulated by ORCA (Version 4.2.0). The application in oily sludge was further conducted. This study provides an effective method and basis for the degradation of PAHs in oily sludge.
The influence of pH-induced structural modifications of myofibrillar proteins (MPs) on their interaction mechanisms with pyrazine compounds was investigated. At a lower pH (4.9, 5.5), MPs aggregated to larger particle sizes due to enhanced the protein–protein interactions. The binding with pyrazine compounds was strongly affected by pH and the nature of flavor compounds. MPs exhibited flavor releasing behavior, probably due to protein–protein interactions and surface tension. Fluorescence analysis revealed that the interaction of pyrazine compounds with MPs followed a combination of static and dynamic quenching. The changes in quenching constant ( K sv ) might be attributed to a dynamic quenching, probably due to protein aggregation. The percentages of free 2,5-Dimethylpyrazine (2,5-DMP) were similar to K sv . Thermodynamic parameters indicated that electrostatic interactions and hydrophobic interactions were the major acting forces in the binding of MPs to 2,5-DMP. The binding of 2,5-DMP increased the α-helix content of MPs.
Butachlor is an effective herbicide to deal with undesired weeds selectively and is used at high levels in Asian countries. However, its interaction and impairment effect on BSA was still not clear. In this study, we investigated the interaction between butachlor and bovine serum albumin (BSA) by multi-spectroscopic methods including UV absorption , circular dichroism (CD) spectra, Fourier transform infrared (FTIR) spectra and fluorescence spectra under physiological conditions (pH = 7.4). The results revealed that there was a static quenching of BSA induced by butachlor stemmed from the formation of complex. Based on thermodynamic data, the interaction of butachlor with BSA was due to happen, and van der Waals force as well as hydrogen bond were the major forces contributed to the interaction. The binding constant K b and number of binding site of butachlor with BSA were 5.158 × 10 5 and 1.372 at 303 K, respectively. The distance r between donor (BSA) and acceptor (butachlor) was 0.113 nm, obtained according to the Förster theory. The results revealed that butachlor induced conformational changes in BSA but the secondary structure of BSA was still retained. In addition, the microenvironment around chromophore residues of BSA, for example, tryptophan , changed as well, resulting from the formation of more hydrogen bonds.
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