Abstract
Written by Carolyn Gorski
Revised by: Carolyna Gorski
Revised by: Shannon Ainsworth
Primitive paints from the times of hunters and gatherers were made by utilizing organic resources. Today, in Biology II these same resources were used to create yellow paint. The paint was produced by boiling water, alum, and white rose, Rosa ‘Alfred de Dalmas’. The yellow paint was painted on paper and exposed to UV, artificial, and no light conditions for seven. A series of tests were performed prior to and after light exposure to observe changes in the sugars, protein content, and pigments of the paint under different lighting conditions. Benedict’s test determined the paint contained sugars with a free aldehyde or ketone group before and after the experiment. Barfoed’s test showed that the paint contained monosaccharide sugars before and after the seven days. Selivanoff’s test showed the paint contained aldoses before the experiment, but the presence of ketoses was evident after the seven days in each treatment. Bial’s test resulted in a positive result for pentose furanoses in the original paint, but hexose furanoses in the no light treatment after seven days. The Iodine test showed that starches were present in the original paint, but were not in each treatment after seven days. The Bradford Assay determined the protein concentration of all treatments decreased significantly after the seven days. Thin layer chromatography showed a decrease in the concentration of the pigment beta-carotene in all three treatments over the seven day period. At the end of the experiment, a t-test was performed on the data with the help of Professor James Dudziak.
Discussion
Written by: Carolyn Gorski
Revised By: Group
The
main question from this experiment is whether or not the composition of
primitive paint will be different after it has been exposed to three different
types of light. The three different types of lighting will be none at all,
artificial light, and sunlight. Our group hypothesizes that the sample of paint
exposed to sunlight will have the greatest degradation of macromolecules and
the treatment with no light at all will have the least amount of change in
composition.
For the Benedict’s test, which
is tests for reducing sugars meaning there is a free aldehyde or ketone group;
our results yielded a positive result for reducing sugars. The same result was
found when we ran Barfoed’s test. This indicates the presence of
monosaccharides. When we ran Selivanoff’s test on the original paint we found
it tested positive to keytoses since out paint reacted with Selivanoff’s
reagent with in the first minute of being in the boiling water bath.
Bial’s, which is responsible for indicating the presence of furanose rings,
showed that hexo furanoses are present. Lastly, we found for the Iodine test,
which are responsible for showing the presence of starch, that the original
paint was indeed positive for starch. We predicted that all of these tests
would indicate a significant degradation in the carbohydrates of the paint
exposed to sunlight, a slight degradation in the florescent light treatment,
and no change in the zero light treatment. Studies have shown that continuous
exposure to UV-B radiation reduces sugar content in plants, which is why we
believe the sunlight treatment will have the most change in carbohydrate
content (Chen, et al 2004). Exposure of plants to UV-B radiation has been shown
to deplete protein content. We predict the
The Second experiment we ran
on the paint was a TLC test or thin layer chromatography to determine the
different pigments in the paint. After placing out TLC strip in our acetone
chamber we found that there was only one pigment in it. This pigment turned out
to be Beta-Carotene. We determined this by measuring the length between the
pigment line and our original line. We then calculated the Rf value and
compared it to known Rf values on and online table to determine it was
Beta-carotene. We then scrapped off the pigment line and ran an absorption
spectrum on it. Using a spectrophotometer, we recorded absorbency readings at
wave lengths between 400 nm and 700 nm. We predicted the basic curve to stay
the same for these tests, with the same peaks; however, we expected the values
to get smaller when they were tested again at week one. UV-B radiation has been
shown to deplete pigments in plants, which is why we think the pigments in the
paint in sunlight will show the most change (Bischof, et al 2002).
When the paints were retested for the sugar assays several things were different than the original tests. When the treatment that was exposed to sunlight was tested it tested negative for both Bial’s test signifying the presence of furanoses and the Iodine test which shows the presence of starch. Since three treatments were ran we think that there was actually degradation of these macromolecules which is why they weren’t present after being exposed to sunlight. When the treatment exposed to artificial light was retested for sugar assays the Bial’s and Iodine test also cam out negative. In the original paint samples prior to treatment they were positive. This is attributed to macromolecule degradation. For the last treatment, no light, the sugar assays showed presence of hexofuranose for Bial’s test and a negative for the presence of starch with the iodine test. Since there was hexofuranoses present in the treatment with no light and not in the treatments with light, we attribute the loss of them to light exposure.
We meet with Dr. James Dudziak in order to run statistical tests on the data we collected. The test that he suggested to perform on our data was a t-test. This test was suggested because it compares whether the means of our two groups of absorbencies (prior to testing and an average of the absorbencies of each treatment after) are statistically different from each other. We set our statistical significance at .05, meaning if the p-value is greater than that we accept our null hypothesis. The null hypothesis was that there was no significant difference between the two results. Our alternative hypothesis was that the means of the two treatments would vary significantly. Our P-value for UV light treatments was .478, for artificial light the p-value was .493, and for no light it was .362. All of these p-values were way above our significance value of .05 meaning that we must accept our null hypothesis that there is no significant difference between the results. Dr. Dudziak did give us some advice as to why our data might have turned out the way it did. First of all, we met with him after collecting data. When we collected data we only did three samples of each treatment. He said that generally statisticians suggest having at least three samples since the t-test is based on the average of these samples. Only having three samples of each gave the individual values much more ability to skew the results. Some of our problems could have been prevented had we met with him prior to performing our experiment.
Before running an experiment it is very important to do some troubleshooting. We tried to troubleshoot is several ways. First of all, our paint was all made at the same time. This helped to prevent any differences in the different treatments of paint. We also made sure that the treatments were in the different light treatments for the same amount of time. If we hadn’t time would become a variable in our experiment. When the paints were put onto the paper we had the same person paint them all and with the same amount of strokes. This was our best idea to be sure that the paint was of equal thickness on the paper. By preplanning quite a bit we hoped that our troubleshooting would help with a lot of the problems that came up in lab.
We expect this experiment to be one that yields interesting results about the composition of primitive paints and the effects light has on them. Whether a painting is in a museum or outside art fair it is usually exposed to light. Learning about some of the beginning paints could potentially help us to make better ones in the future. Knowing how these paints are affected by different conditions is very exciting for the art world. It will allow artists more flexibility and knowledge to be creative.
Figure 1: Results of Benedict's Sugar Test. This picture shows the setup of the Benedict’s sugar test with the yellow paint prior to light exposure in the middle and a negative control sample of Sucrose on the left and a positive control sample of D-Glucose on the right indicated by a red precipitate.