The aspartate-99 of secreted phospholipase A2 (PLA2) has been proposed to be critical for the catalytic mechanism and interfacial activation of PLA2. Aspartate-99 connects the catalytic machinery (including the catalytic diad, the putative catalytic waters W5 and W6, and the calcium cofactor) to the hydrogen-bonding network. The latter involves Y52, Y73, the structural water, and the N-terminal region putatively required for the interfacial activation. A triple mutant of bovine pancreatic PLA2 with substitutions aspartate plus adjacent tyrosine residues (Y52,73F/D99N) was constructed, its X-ray structure was determined, and kinetic characteristics were analyzed. The kinetic properties of the D99N mutant constructed previously were also further analyzed. The X-ray structure of the Y52,73F/D99N mutant indicated a substantial disruption of the hydrogen-bonding network including the loss of the structural water similar to that seen in the structure of the D99N mutant published previously [Kumar, A., Sekharudu, Y. C., Ramakrishnan, B., Dupureur, C. M., Zhu, H., Tsai, M.-D., & Sundaralingam, M. (1994) Protein Sci. 3, 2082-2088]. Kinetic analysis demonstrated that these mutants possessed considerable catalytic activity with a k(cat) value of about 5% compared to WT. The values of the interfacial Michaelis constant were also little perturbed (ca. 4-fold lower for D99N and marginally higher for Y52,73F/D99N). The results taken together suggest that the hydrogen-bonding network is not critically important for interfacial activation. Instead, it is the chemical step that is perturbed, though only modestly, in the mutants.

One of the greatest challenges of tunnel lighting and underpass lighting systems is their ability to support drivers’ visual perceptions—both day and night—from the point of entry through to the point of exit. Effective tunnel and underpass lighting, therefore, requires consistent light levels throughout the structure for safe passage.  We provide a number of LED tunnel lighting options.

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These are also highly corrosive environments requiring tunnel lights have sealed and durable luminaires. This is due to heavy traffic and fluctuations in weather and climate, tunnel fixtures are continually exposed to water, dirt, road salt, exhaust fumes, brake dust and other corrosive agents.

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While Kenall tunnel fixtures are controls agnostic, NYX Hemera is our preferred provider. Their seamless integration with our robust luminaires has proven successful in major tunnel projects across the U.S. While the choice of lighting controls is yours, we are confident Kenall tunnel luminaires and NYX Hemera controls will perform in even the most challenging tunnel environments…today, tomorrow, and well into the future.

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