1. Fluorescence and Absorption Spectroscopy of Bio-molecules
Ivanna Eusebe, René Cardona and Katherine Gil
Mentor: Ms. Cheng-Hui Liu
Steady State Laser Spectroscopy Lab
City College of New York
High School Summer Research Program

2. Abstract
We have looked at the fluorescence and absorption of the four bases of deoxyribonucleic acid (DNA), and three amino acids (Phenylalanine, Tryptophan, and Tyrosine). The purpose of this project was to learn about the fundamental science behind disease detection by using fluorescence and absorption. This experiment can be used to find malignant and benign forms of tumors and other cancerous diseases.

3. Fluorescence
When a substance absorbs radiation, atoms in the substance are excited to a higher energy level. The atoms then emit light of lower energy (longer wavelength) and relax to the ground state. The remainder of the energy is released in the form of heat.

4. Absorption
Absorption is the process in which a substance absorbs or gathers incoming light. Light that is not absorbed is either reflected or transmitted.
E2 > E1
electron

5. Bio-molecules Investigated Table#1
Name
Molecular Formula
Molecular Weight
Molecular Structure
Deoxyadenosine
  (A)
C10H13N5O3
251.24
 Deoxycytidine
(C)
C9H13N3O4
227.22
 Deoxyguanosine
(G)
C10H13N5O4
595.2
 Thymine
(T)
C10H14N2O5
242.23
Tryptophan
C11H12N2O2
204.23
Tyrosine
C9H11NO3
181.19
Phenylalanine
C9H11NO2
165.19

6. Procedures 1) The solution was inserted into a vial by:
a. measuring a certain amount of water (varying from 1mL to 4mL)
b. Then the DNA bases were mixed with powder and water
2) The solution was inserted into the vial and then the narrowband filter (optional) was inserted into the fluorescence meter.
3) Tests were run for the fluorescence and the absorption.
4) The results were made into graphs using origin 5.0.

7. This is a picture of the C-Scan LDS-3 Fluorescence meter we used to measure the fluorescence of the bio-molecules.
This is a picture of the Perkin-Elmer Lambda 9 UV/VIS/NIS Spectrometer we used to measure the absorption of the bio-molecules.
The differences between the two machines (not including the fact that one measures fluorescence and the other measures absorption) is that they collect data in different ways. For example if we wanted to see the absorption we would run a background check to make sure that the viles in which we put the bio-molecules would properly allow light to travel through them. Whereas in fluorescence we do not have to go through the previous procedure.

8. Experimental Results

9. FIG. 2

12. ( excitation WL 260 nm)

13. ( excitation WL 240 nm)

14. Peak Importance Future Work
The peak is important to our research because the peak tells us at what wavelength the bio-molecules fluoresce. Knowing at what wavelength it fluoresces is important because then we have a control sample to compare and contrast whether a tissue is cancerous or not. If the tissue is cancerous, we can determine the intensity or severity of the it.
Future Work
Our future goal is to learn about the Stokes Shift.
We also would like to conduct experiments that would hopefully lead to better and faster detection of cancerous diseases.

15. Conclusion
We learned how to find the fluorescence and absorption of different materials.
We learned how to use many different kinds of spectrophotometers (and spectrometers).
We also learned how this experiment is beneficial to today’s society and how it is associated with cancer detection.

16. Discussion
After doing the entire experiment and looking over the graphs we can see the differences in each of the Amino Acids and DNA bases excitation and emission wavelength. Our graphs show all the bio-molecules at a normalized fluorescence and absorption spectra. We can also see that when the bio-molecules are a powder it shows a scattered curve, because it is harder for the light to go through the powder. In a solution the light can easily travel through it because the solution is a liquid.

17. References
R.R. Alfano, and Yuanlong Yang, “Stokes Shift Emission Spectroscopy of human tissue and key Biomolecules” IEEE Journal of Selected Topics In Quantum Electronics. Vol. 9, No. 2, 2003
D. Onidas, D. Markovitsi,*S. Marguet, A. Sharonov, and T. Gustavsson*, “Fluorescence Properties of DNA Nucleosides and Nucleotides: A Refined Steady-State and Femtosecond Investigation” J. Phys. Chem. B 2002, 106,
Acknowledgements
• Mentor: Ms. Cheng-Hui Liu
• Doctor Sat
Professor R.R. Alfano
Dr. Peter Gross
Ms. Charlene Lee
Harlem Children Society
Mr. Gonzalez
Dr. Manuel Zevallos
NASA COSI