Efficacy of Different Forms of UV Protection

Experiment

Methods

We exposed both Wildtype and Mutant strains of yeast to 20 seconds of UV light while shielded by three colors of UV blocking sunglasses: Black, Orange, and Clear

12 plates were divided up into two groups of 6 to test the difference in wildtype vs mutant. We had 2 sub-replicates of each color of sunglasses.

We obtained 20 seconds as our exposure time in our preliminary trial where 20 seconds was found to be the minimum amount of time of UV exposure needed to result in 100% mortality in wildtype yeast whereas any amount of exposure proved fatal for the mutant strain.

Results

Conducted two tests, to examine which form of protection is more effective.

1) Does the chemical protectant in sunglasses absorb enough UV light to prevent damage?

Do the colors of the sunglasses influence its protective abilities?

We found that in all colors, there was 100% mortality in the mutant strains whereas many colonies were sustained in the wildtype strain.

This suggests that while the color of sunglasses do not effect its UV blocking capabilities, it is not absorbing enough UV light to protect mutant strains from eradication.

UV Protection

Conclusion

There are 2 types of UV protection: Chemical and Physical.

Chemical Protectants absorb UV light whereas Physical Protectants disperse UV light.

By testing these two types of UV protection we can see which materials are more effective and consider which materials to consider for more extensive applications in UV protection.

Sunglasses commonly use a thin layer of chemicals within the layers of glass to absorb UV light. Chemical protection is also found in common sunscreens.

Physical protection is found in industrial glass coating as well

as specialized sunscreen for those with sensitive skin.

Experiment 2

While sunglasses do provide some level of

protection for the wildtype strain, it is insufficient for mutant strains. This suggests that individuals with eyes that are especially vulnerable to UV radiation should seek out a more powerful form of protection.

We also see that physical blockers of UV light are more effective at preventing UV rays from damaging both strains.

Perhaps we should seek out ways to apply physical blockers over sunglasses or incorporate more industrial grade chemical absorbers of UV light into commercial products.

For future experiments, it would be best to test the physical sunblock against a chemical sunblock to execute a more equal test

We used a special sunscreen lotion that has titanium dioxide, a physical UV protectant.

It protects skin from UV damage because of its high refractive index, which scatters UV light away from the skin.

It is also the preferred form of sunscreen as it does not cause skin irritation in people with sensitive skin

www.youtube.com/watch?v=o9BqrSAHbTc

Methods

We laid down a sheet of saran wrap over UV table and spread an even layer of sunscreen across it.

We placed our plates of yeast and exposed them to UV for 20 seconds

These plates were divided up in to groups of 6 with 5 replicates of sunscreen protected plates and a single control plate without protection.

We repeated the time interval of 20 seconds to maintain a consistent test time between the two experiments

Results

A count of the colonies showed that much of the UV rays had been effectively blocked as there were several colonies in both mutant and wildtype plates.

Compared to the performance of the chemical blocker, this suggests that the physical blockers used in this experiment are more effective at blocking harmful UV light

Intro

References

"Cancer Council Australia; Centre for Eye Research Australia: Position Statement: Eye Protection. August 2006"

Kanavy HE, Gerstenblith MR (December 2011). "Ultraviolet radiation and melanoma". Semin Cutan Med Surg 30 (4): 222–8.

Osborne JE, Hutchinson PE (August 2002). "Vitamin D and systemic cancer: is this relevant to malignant melanoma?". Br. J. Dermatol. 147 (2): 197–213. doi:10.1046/j.1365-2133.2002.04960.x. PMID 1217408

Winkler, Jochen (2003). Titanium Dioxide. Hannover: Vincentz Network. pp. 5. ISBN 3-87870-148-9.

Zeman, Gary. 2009. Ultraviolet Radiation. Health Physics Society.

Yeast

Damage from UV Rays is an everyday danger that we face in life.

Many organisms have evolved a mechanism through which they can repair damage caused by UV

Yeast are a good model organism to study when considering DNA damage repair

Yeast have several DNA repair mechanisms one of which are homologs to the DNA repair mechanism found in humans. In yeast, this is the RAD1 gene that is involved in DNA excision repair.

By knocking out this gene we create RAD1 Mutants that can no longer perform this important function. When the yeast accumulate damage, this eventually becomes fatal.

During each experiment, we must cover the yeast after radiation because they still have functional photolyase which allows them to repair their DNA in the presence of visible light.

Comparing survivability of Mutant and Wildtype when shielded by some form of UV protection will be very informative in the development of better UV blocking products.

www.microbiologyonline.org.uk/themed/sgm/img/slideshows/3.1.4_fungi_2.png

www.lighting.philips.com/pwc_li/main/subsites/special_lighting/assets/

Efficacy of Different Forms of UV Protection

by Josh Lee

Haley Matthews & Omar Sahibzada