Decontaminating Nebraska's Water Supplies with Uranium-peptide Bonding
Lauren Samson, Esha Mishra, Cody Schultz, Rebecca Y. Lai, Carolina C. Ilie, Peter A. Dowben
Author
07/23/2021
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16
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Description
In Nebraska, wells that the majority of the population rely on for their water needs have been tested, revealing that in over 26 towns in the state have uranium concentrations higher than federal standards. This uranium in the soil is natural, leftover from glacial and volcanic deposits, but the concentration of uranium oxide 〖UO〗_2^(2+) is increasing due to the frequent use of nitrate-based fertilizers. When ingested in amounts greater than the 30 micrograms per liter (the maximum recommended by WHO), uranium will cause kidney damage and possibly even cancer. Currently, there are two main forms of testing for uranium in a water supply, uranium mass-spectrometry and Gross Alpha Radiation. We propose a new type of test, using naturally occurring peptide chains that capture the Uranium atoms, making the peptide-uranium bonded molecule a biosensor for uranium. These peptides also have a use to remove uranium from within the human body after critical exposure to the toxic metal.
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- [00:00:00.000]Hello, my name is Lauren Samson.
- [00:00:01.660]I'm a physics student at a Osweggo State,
- [00:00:03.387]and a participant of the 2021 Summer REU program
- [00:00:06.640]here at UNL.
- [00:00:07.783]I was able to work with Dr. Peter Dowben's group
- [00:00:10.100]on uranium peptide bonding
- [00:00:11.750]to decontaminate Nebraska's water supplies.
- [00:00:15.800]In water, uranium's soluble form is UO2-plus,
- [00:00:19.760]pictured on the right.
- [00:00:22.590]This soluble form of uranium has been found
- [00:00:25.340]in excess of 30 micrograms per liter,
- [00:00:27.750]the maximum recommendation concentration
- [00:00:31.030]by WHO, in over 26 towns in Nebraska.
- [00:00:34.120]This uranium is natural,
- [00:00:36.240]however, it is changing into its soluble form
- [00:00:38.980]due to the increased use of nitrous-based fertilizers
- [00:00:42.700]within the state.
- [00:00:44.120]In its soluble form,
- [00:00:45.310]uranium is a nephrotoxin
- [00:00:46.890]that primarily causes kidney damage in humans.
- [00:00:50.860]To test for uranium in a water supply
- [00:00:52.830]there are two main forms of testing,
- [00:00:54.920]uranium mass spectrometry,
- [00:00:57.790]and gross alpha radiation.
- [00:00:59.630]However, we propose a new type of test
- [00:01:01.860]which uses naturally occurring peptide change
- [00:01:05.550]as a biosensor for uranium.
- [00:01:07.930]In addition, once bonded,
- [00:01:10.640]this uranium cation becomes insoluble
- [00:01:13.400]and can pass through the digestive tract
- [00:01:15.500]of those previously affected by uranium without harm.
- [00:01:19.990]Here I will compare the structures of two of our peptides.
- [00:01:22.840]On the top we have R6 arginine,
- [00:01:25.520]which is composed of a sulfur group,
- [00:01:28.570]a carbon chain and R6 groups,
- [00:01:32.140]hence R6 with a lysine and methyl blue indicator.
- [00:01:36.690]On the bottom, we have serine S6,
- [00:01:38.890]which is of a similar structure to arginine R6.
- [00:01:43.020]However, the group ending,
- [00:01:45.080]it is hydroxyl for serine,
- [00:01:47.230]but for arginine, it is a guanidino group.
- [00:01:51.470]Previous work done by our collaborates
- [00:01:52.970]in the UNL chemistry department,
- [00:01:54.820]we know that the sulfur ending
- [00:01:56.220]on our peptides bind nicely to gold.
- [00:01:58.930]This means we can make an Au peptide thin film,
- [00:02:03.330]which we can then take
- [00:02:04.640]x-ray photo electron spectroscopy data upon.
- [00:02:08.400]This spectra produced should have a strong peak
- [00:02:11.210]near the known binding energy for uranium,
- [00:02:13.270]which is approximately 381 eV,
- [00:02:16.330]but also the exothermic reaction will fulfill
- [00:02:18.830]the second requirement for the peptides
- [00:02:20.780]to be considered a biosensor for uranium.
- [00:02:23.750]Here we have a diagram representing the internal process
- [00:02:26.450]of XPS.
- [00:02:28.820]An x-ray is produced and hits the sample
- [00:02:33.460]at a specified angle.
- [00:02:35.350]The energy of the x-ray excites electrons
- [00:02:39.100]to become photoelectrons.
- [00:02:41.150]These photoelectrons then move
- [00:02:42.480]through a hemispherical analyzer around to a detector.
- [00:02:46.240]The detector then records the number of electrons
- [00:02:49.080]based on their energy when the detector receives them.
- [00:02:53.460]And XPS is based on the theory of the photoelectric effect
- [00:02:57.700]and Beer-Lambert Law.
- [00:02:59.990]Next, we have a picture
- [00:03:01.040]of our ultra-high vacuum UHV chamber,
- [00:03:05.390]which was operated at a base pressure
- [00:03:07.360]of five times 10 to the negative nine Torr.
- [00:03:10.460]And here are the results from our XPS runs.
- [00:03:13.740]We compare the results for two
- [00:03:16.610]of the spectra taken
- [00:03:18.140]between S6 serine and R6 arginine.
- [00:03:23.980]While we only compare these two,
- [00:03:25.680]the data sets of the other peptides tested are very
- [00:03:28.600]similar to serine.
- [00:03:30.600]On the left we have the nitrogen spectra,
- [00:03:33.470]and we see that in both samples with and without uranium,
- [00:03:39.510]arginine has a defined peak near the binding energy,
- [00:03:42.850]the known binding energy of nitrogen.
- [00:03:46.670]On the right, we have the uranium spectra.
- [00:03:51.420]And again, we see that R6 arginine has a defined peak
- [00:03:56.380]near the known binding energy for uranium.
- [00:04:00.190]Now with the nitrogen spectra,
- [00:04:03.400]we see this defined peak primarily due
- [00:04:06.330]to arginine's guanidino groups,
- [00:04:09.860]which contain nitrogen.
- [00:04:14.590]But as we see that arginine is the only peptide
- [00:04:18.550]that has a defined peak for the uranium spectra,
- [00:04:22.850]we conclude that the guanidino group binds best
- [00:04:27.870]to uranium and therefore means
- [00:04:30.110]that arginine is our best biosensor for uranium.
- [00:04:36.430]However, as arginine only contains six groups,
- [00:04:40.830]we can move up to an R9 sample,
- [00:04:44.340]which will add an additional three guanidino endings.
- [00:04:47.720]We believe this will be truly our best candidate
- [00:04:51.520]for uranium biosensor
- [00:04:53.990]due to the addition of these three binding sites
- [00:04:57.800]for uranium.
- [00:04:59.270]However, to strengthen this conclusion,
- [00:05:02.210]we would like to do absorption tests of all the peptides
- [00:05:04.990]in solution form.
- [00:05:06.800]And here is the complete reference list.
- [00:05:09.350]I would like to thank both the Nebraska REU
- [00:05:13.020]for allowing me to work in person,
- [00:05:16.630]but also Dr. Peter Dowben for allowing me
- [00:05:18.630]to help his group with this research.
- [00:05:21.950]Last but not least, the PowerPoint presentation
- [00:05:26.860]in poster form.
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