Team:Dalhousie Halifax NS/drylab/bioreactor

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Fluorescence Model

Overview

The data used to build a model of pyoverdine fluorescence was taken from an article published in the Journal Of Inorganic Biochemistry titled “Fluorescent complex of pyoverdin with aluminum”. Fluorescence intensities correspond to the sum of the emission values of pyoverdine between 450 and 470 nm [1]. The fluorescence intensity of 3 different solutions of pyoverdine was measured with increasing ionic aluminum concentration. A 1 μM pyoverdine solution, a 1 μM pyoverdine solution with 3 1 μM Fe (III) added after aluminum, and a 1 μM pyoverdine solution with 3 1 μM Fe (III) and aluminum added simultaneously [1].

Fig 1. Fluorescence intensities of pyoverdine and Fe (III) solutions with increasing aluminum concentrations. Taken from “Fluorescent complex of pyoverdin with aluminum” [1].

The fluorescence intensity of 1 μM pyoverdine in the absence of metals is 2245. When pyoverdine is present in a 3 μM solution of Fe (III) without any aluminum in solution the fluorescence intensity is 80 [1].

Modelling

To build a model of pyoverdine fluorescence intensity with changing aluminum and iron concentrations we started with a basic assumption that the difference in fluorescence in solutions containing Al (III) only, and both Al (III) and Fe (III) is proportional to [Fe]. Using this assumption, we generated estimated values with different concentrations of Fe (III).

Fig 2. The change in ionic aliuminum levels for Nova Scotia rivers from June 1 2015 to June 1 2016 (MacLeod, 2016).

Looking at ionic aluminum levels from June 2015 to June 2016, ionic aluminum levels appear to be the highest from June to September, and lowest around December to March. When plotting the temperature and pH of the water over the same time frame, the same trend appears. From these graphs the amount of dissolved ionic aluminum changes with the changing temperature, these changes will also lead to a change in pH of the water.

Conclusion

It is important that our biosensor is able to read toxic ionic aluminum levels of 0 μg/L to 15 μg/L (when pH of water is between 5.0 and 6.0) or 30 μg/L when the water has a pH of less than 5.0 as these levels are when the toxicity of aluminum becomes dangerous. After analyzing the relationship between the toxicity of aluminum, pH, and temperature of the water it becomes clear that the highest aluminum levels occur within a pH of 4.25 - 5.5 and a water temperature of 15 - 20 degrees celcius

References

[1] del Olmo, A., Caramelo, C., & SanJose, C. (2003). Fluorescent complex of pyoverdin with aluminum. Journal Of Inorganic Biochemistry, 97(4), 384-387. doi: 10.1016/s0162-0134(03)00316-7