ABSTRACT
The stability and activity of lipase in organic media are important parameters in determining how quickly biocatalysis proceeds. This study aimed to examine the effects of two commonly used alcohols in industrial applications, methanol (MtOH) and ethanol (EtOH) on the conformational stability and catalytic activity of G210C lipase, a laboratory-evolved mutant of Staphylococcus epidermidis AT2 lipase. Simulation studies were performed using an open-form predicted structure under 30, 40 and 50% of MtOH and EtOH at 25 °C and 45 °C. The overall enzyme structure becomes more flexible with increasing concentration of MtOH and exhibited the highest flexibility in 40% EtOH. In EtOH, the movement of the lid was found to be temperature-dependent with a noticeable shift in the lid position at 45 °C. Lid opening was evidenced at 50% of MtOH and EtOH which was supported by the increase in SASA of hydrophobic residues of the lid and catalytic triad. The active site remained mostly intact. An open-closed lid transition was observed when the structure was re-simulated in water. Experimental evaluation of the lipase stability showed that the half-life reduced when the enzyme was treated with 40% (v/v) and 50% (v/v) of EtOH and MtOH respectively. The finding implies that a high concentration of alcohol and elevated temperature can induce the lid opening of lipase which could be essential for the activation of the enzyme, provided that the catalytic performance in the active site is not compromised.Communicated by Ramaswamy H. Sarma.
ABSTRACT
Public health measures employed to fight against the spread of SARS need to be guided by biomedical knowledge as well as an understanding of the social science aspects of the disease. Using Singapore as a case study, we explore how the state constructs the disease and implements measures targeted at creating a ring of defense around the island and using surveillance to monitor and prevent its spread. While there is support, there is also resentment among some Singaporeans who complain that their right to privacy has been invaded and that over surveillance may have actually occurred. Marginalisation and discrimination have not only affected the local population but in this open economy which is striving to achieve global city status, businesses, tourism, foreign talent, foreign contract workers and foreign students studying in Singapore have also been negatively affected. While Singapore has been applauded by WHO and used as an example of quick and effective response, a holistic approach to the management of infectious disease must address the social implications of strategies that are drawn from medical knowledge alone because it impinges on the social lives of people and how people interact with each other under stressful circumstances.
