Sunscreen's Effects on UV Attenuation Chase McCorkle 9 th grade Central Catholic High School
Ultraviolet Light Electromagnetic radiation The wavelength is shorter than that of visible light The shorter wavelength has greater energy The sun produces UV light Responsible for sunburn and some cancers Alters and damages DNA Three types; UVA, UVB, UVC
Sunscreen Commonly used topical ointment for help to prevent sunburn Prevents sunburn by reflecting or absorbing ultraviolet radiation from the sun Uses organic particulates to reflect or scatter UV light
Sunscreen (continued) Non-mineral sunscreen uses harmful ingredients Mineral sunscreen uses environmentally safe ingredients Sun protection factor (SPF) the measurement of protection
Microbial Flora Comprised of all the microorganisms that reside in or on the human body (examples: skin, saliva, gut) Most species are non-pathogenic microorganisms that either have no effect on the host or offer some benefit
Skin Flora Comprised of all microorganisms of the human flora that live on the skin Trillions of bacteria live on or in the skin of an average human Stimulates the skin's immune system by the prevention of colonization by pathogenic microorganisms
Saccharomyces Cerevisiae Yeast Unicellular, eukaryotic microorganism 3 4 µm diameter The most studied cellular model in research Cell cycle is similar to human cells Comparable DNA replication, recombination, cell division and metabolism
Purpose To find if mineral sunscreen and non-mineral sunscreen vary significantly in the remediation of UV light s effects on yeast cells
Hypothesis Null there will be no significant effect of the sunscreen Alternative Both sunscreens will have protective effect on UV exposed yeast survivorship
Materials 48 YEPD agar plates Spreader bars Ethanol Bunsen burner Vortex Saccharomyces Cerevisiae Yeast Mineral sunscreen SPF 60 Non-mineral sunscreen SPF 60 Wax paper 254 nanometer LabConco UV hood light with a UVC bulb 20-40 micro watts per square centimeter 0.7-0.9 micro watts per square centimeter at the working surface Incubator Tape Micro pipettes Sterile solution Klet spectrophotometer
Procedure 1. Saccharomyces cerevisiae was grown overnight in sterilized YEPD media 2. A sample of the overnight cultures was added to fresh media in a sterile sidearm flask 3. The culture of yeast was incubated at 30 C until a density of 50 Klett spectrophotometer units was reached. This represents a cell density of 10^7 cells per ml 4. The culture was diluted in sterile dilution fluid to a concentration of approximately 10^5 cells per ml
Procedure (continued) 5. Measured out 0.1 grams of mineral sunscreen on wax paper 6. Spread in a circular motion using a sterilized spreader bar 7. Created 16 pieces for mineral and 16 non-mineral 8. Used sterile pipette to add 0.1 ml of yeast (10^3 cells per ml) to the YEPD plate 9. Attached the wax paper covered with sunscreen as a replacement lid for the plate
Procedure (continued) 10. Attached wax paper with nothing on it to create a control 11. Exposed plates to UV light at the time of 0, 60, 120, 360, and 720 seconds 12. When finished, took off the wax paper and put on the lids 13. Incubated at 38 degrees c for 48 hours 14. Measured the survivorship by counting the colonies of yeast 15. Took plates to lab at Carnegie Mellon University to be autoclaved
Yeast colonies Sunscreen effects on UV exposed survivorship P-Value: 0.00039111 120. 109. 90. 60. 88.2 88.2 88.2 51.5 73.5 Control Non Mineral 42.5 Mineral 30. 32.5 17.8 0. 4.3 6. 1.3 1. 0.8 0. 0 60 120 360 720 UV exposure (seconds)
P- Values Time 0 60 120 360 720 P-value 0 0.9657 1.19E-0.6 0.00205 0.03998
Analysis Dunnett s Test T-Value 3.03 Time 0 Sec 60 sec 120 sec 360 sec 720 sec Mineral T- Value 0 Insignificant 1.334 Insignificant 0.295 Insignificant 0.035 Insignificant 0.114 Insignificant Non-Mineral T-Value 0 Insignificant 8.524 Significant 11.689 Significant 4.449 Significant 2.596 Insignificant
Analysis Dunnett s Test T-value 3.03 Time 0 sec 60 sec 120 sec 360 sec 720 sec Mineral T- Value 0 Insignificant 9.852 Significant 11.393 Significant 4.485 Significant 2.711 Insignificant
Results Does UV light have a significant effect on yeast survivorship? Yes: P-Value 0.00039111 Is there significant variation between mineral and non-mineral sunscreen? Yes: T-Crit is greater than 3.03 at 60, 120, and 360 seconds but not at 720 seconds
Conclusion Null UV light will not have a significant effect on yeast survivorship Reject the null Alternative Both sunscreens will have protective effect on UV exposed yeast survivorship Reject the alternative
Limitations and extensions Plate lids were replaced which could lead to possible contamination Hard to insure even spread Only UVC light used Use different brands Use shorter exposure time intervals Use other types of exposure Use other means of spreading Try different microbial model Test growth/help
Works cited 1. "Effects of UV Radiation on You." Student's Guide -. N.p., n.d. Web. 16 Dec. 2014. 2. HowStuffWorks. HowStuffWorks.com, n.d. Web. 20 Dec. 2014. 3. "Natural vs. Chemical Sunscreen - Goddess Garden." Goddess Garden Natural vs Chemical Sunscreen Comments. N.p., 18 Mar. 2012. Web. 03 Dec. 2014. 4. "OCTINOXATE." Skin Deep Cosmetics Database. N.p., n.d. Web. 10 Dec. 2014. 5. "OXYBENZONE." Skin Deep Cosmetics Database. N.p., n.d. Web. 11 Dec. 2014. 6. "What Is SPF Sunscreen?" - Sun Protection Factor Explained by Badger. N.p., n.d. Web. 17 Dec. 2014.
Anova (all) Anova: Single Factor SUMMARY Groups Count Sum Average Variance Column 1 20 615 30.75 1566.618 Column 2 20 1356 67.8 1587.747 Column 3 20 447 22.35 730.2395 ANOVA Source of Variation SS df MS F P-value F crit Between Groups 23393.1 2 11696.55 9.033003 0.000391 3.158843 Within Groups 73807.5 57 1294.868 Total 97200.6 59