| dc.description.abstract | In this study, thymine dimers were detected, for the first time, in both thymine and DNA aqueous solutions using Raman spectroscopy. Thymine dimers, formed by UV radiation of DNA, inactivate bacteria by inhibiting their DNA replication. UV inactivation of bacteria is becoming increasingly important because the number of antibiotic-resistant bacteria is increasing. It is found that the formation of these dimers continues to increase for 20 minutes of irradiation, after which an equilibrium is established between the thymine monomers and dimers. In addition, the formation of another mutagenic photoproduct, (6-4) photoproduct was identified by its fluorescence spectrum. The spectroscopic methods used in this study pave the way for fast and definite identification of the ratio of live and dead bacteria and thus become more advantageous than traditional techniques such as plating.
Owing to the fact that, in many cases, the in-situ detection of different material(s) is imperative, we have designed, constructed, and utilized various hand-held instruments which are capable of recording and displaying the spectra of the investigated materials, and even biological molecules, in-situ within minutes. We have designed and constructed a hand-held device that records resonance Raman spectra of bacterial carotenoids and allows us to measure the ratio of live and dead bacteria after UV irradiation, and also identify various bacterial strains. Another hand-held device was constructed which when used with a telescope, can detect remotely the percentage of inactivated bacteria after UV irradiation, by measuring the change in fluorescence intensity of tryptophan and tyrosine. Both of these devices were constructed and operated successfully. We have also designed and constructed another handheld instrument that uses a cell-phone camera to detect Raman and fluorescence spectra of various chemicals and biological molecules.
We developed a technique to expand human vision to UV and infrared (IR) regions, by making use of IR to visible upconverting rare-earth-doped microparticles (NaYF4:Yb,Er), and a UV to visible converting fluorescent dye (Stilbene 420). These particles were embedded in proteins and rod outer segments in order to successfully demonstrate the conversion. We also developed an eyeglass device, in which the fluorescent dye and upconverting microparticles were dispersed in the lens to expand the visual region of the human eye. | en |
