Biology

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1.4.3 Thermostability of Lysozyme on SDS-PAGE
To determine the thermostability of lysozyme enzymes, Akinalp et. al. (2007) exposed the supernatant of various recombinant bacteria to various temperatures (from 37C to 100C) for 15 min followed by centrifugation at 15,000 rpm to remove denatured proteins. The supernatant was then mixed with an equal volume of trichloroacetic acid and the protein collected by centrifugation. Protein analysis was then performed using a denaturing polyacrylamide gel (SDS-PAGE, 12% (w/v)). After electrophoresis, protein bands were visualized by a coomassie blue staining. As a result, the thermostability of the lysozymes from the recombinant bacteria was found to be different. The lysozyme expressed by S. salivarius subsp. thermophilus cells has high thermoresistance and was not denatured at 70C for 15 min. In contrast, the enzyme expressed by L. lactis and E. coli cells was easily denatured when exposed to the same temperature.
1.4.4 Immunoassays
The lack of sensitivity and long assay times of the turbidimetric and lysoplate techniques has led to the development of various immunoassay methods for the determination of lysozymes. Immunoassays rely on the reaction between the target analyte and a specific binding molecule of biological descent (the antibody). They can produce both quantitative and qualitative results and have shown considerable improvements in sensitivity (Ekins andand Chu, 1997). For example, Porstmann et. al. (1989) developed an enzyme immunoassay for the detection of lysozyme in patients with Crohn’s disease and rheumatoid arthritis. Urine samples were taken from patients and were tested using three variations of the same method. The method showing highest sensitivity involved pre-co...

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...ed with a horseradish peroxidase conjugated secondary antibody. The total test time is 4 ¼ hours (http://www.funakoshi.co.jp/data/datasheet/BTI/BT-630.pdf).
Similarly, a company Orgentec (Mainz, Germany) supplies a kit known as Anti-Lysozyme kit for lysozyme in serum and plasma. This test can process 96 patient samples at a time, only requires 10 μl of sample and involves a plate pre-coated with antibody. The antigen from the patients’ sample is added along with a horseradish peroxidase conjugate and then followed by TMB (a color substrate). The reaction is stopped by adding hydrochloric acid; the total time for this assay is two hours, due to the plates being purchased pre-coated (http://www.orgentec.com/products/pdfs/ELISA_en_IFU_ORG_526.pdf). All of these kits have the advantage of conducting analysis on several patient samples using minimal biological fluid.

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