Team:Nanjing High School/Description
Description
Inspiration
Nowadays in China, it is easy for one to notice some vendors selling a kind of mobile phone film called anti-blue light mobile film, which intrigued us. A question hit us when we hung out together hearing someone peddling such a product: is it true that the blue light is everywhere?
Out of curiosity to this question, we visited an academician who invented a new kind of anti-blue light using normal materials but special structure design. The answer was striking. According to the academician, any electric device with screen can generate the blue light, and the blue light was considered as a potential pathogenic factor to many eye diseases. By looking through the Internet, we found that many scientific researches point out tremendous negative influence of the blue light. Some even claim that lights can generate blue light too. So how can people know how much blue light there is in the circumstances they stay in? It seems that there is not a direct answer to the question since we failed to find any product that serve such function. We immediately realized that such vacancy was perfect for us to visualize it.
Our project
Our project is a public welfare project about blue Light monitoring. The core of the project is an engineered Escherichia coli with light-catch system (the expression of optically controlled inhibitory protein, thus regulating the probability of Cas1-Cas2 capturing DNA fragments). The time of exposure to light of Escherichia coli is determined by PCR. In the follow-up promotion, we will make such microorganisms into an ornament to wear on people. After a certain period of time, the samples are returned to the lab, where the length of the Escherichia coli growth is read to infer how long the blue light was exposed.
Introduction to blue light
Blue light
Blue light is able to penetrate the crystalline lens, causing photochemical damage and accelerating the oxidation of retinal macular cells toward the retina. Although the lens of adult eyes has a low transmittance to blue light, exposure to blue light for a long time period will still cause degenerative changes of the retina, resulting in photo retinitis. The hazard of blue
light deserves the attention from the public.
Reference:
赵介军, 乔波, &过峰. (2015). Led 蓝光危害研究. 照明工程学报(1), 84-87.
Introduction to organismal photoreceptors
Light plays an important role in the development of plants. In nature, plants are capable of detecting light and adjusting their behaviors in response to light. When exposed to light, the signaling photoreceptors begin to function and convert light to signals, such as the expression of an array of light-responsive genes, in order to activate more biological processes.We compared serveral papers about light-sensor engineering:
species |
protein |
light |
Publication time |
reference |
Arabidopsis |
PrB，FR，PfrB，PIF3 |
red (R) and far red (FR) |
2000 |
1 |
E. coli |
pcyA, ho1, cph8 |
Red light |
2005 |
2 |
E. coli |
YF1,FixJ |
Blue light(470 nM) |
2012 |
3 |
HEK293 cell |
GAVP homodimerizes |
460 nM |
2012 |
4 |
E. coli |
pcyA and ho1/ Cph8/ CcaSR |
red, green, and blue light induce the PK1F,PCGG, and PT3 promoters 20-fold, 9-fold, and 41-fold, respectively |
2017 |
5 |
The biological activity of photoreceptors is regulated by the light absorption. In essence, they are light-gated protein switches. The Blue sensor, as the blue light regulated switch is called, functions by with a system of YF1 and FixJ. In the absence of blue light, YF1 phosphorylates its cognate response regulator FixJ, which then drives robust gene expression from the FixK2 promoter. Upon light absorption, net kinase activity of YF1 and consequently gene expression is greatly reduced. Thus, by controlling the blue light present in the environment, we are able to control the gene expression downstream of FixK2 promoter.
References:
1. Martinez-Garcia, J.F., Huq, E. and Quail, P.H. (2000) Direct targeting of light signals to a promoter element-bound transcription factor. Science, 288, 859-863.
2. Levskaya, A., Chevalier, A.A., Tabor, J.J., Simpson, Z.B., Lavery, L.A., Levy, M., Davidson, E.A., Scouras, A., Ellington, A.D., Marcotte, E.M. et al. (2005) Synthetic biology: engineering Escherichia coli to see light. Nature, 438, 441-442.
3. Ohlendorf, R., Vidavski, R.R., Eldar, A., Moffat, K. and Moglich, A. (2012) From dusk till dawn: one-plasmid systems for light-regulated gene expression. Journal of molecular biology, 416, 534-542.
4. Wang, X., Chen, X. and Yang, Y. (2012) Spatiotemporal control of gene expression by a light-switchable transgene system. Nature methods, 9, 266-269.
5. Fernandez-Rodriguez, J., Moser, F., Song, M. and Voigt, C.A. (2017) Engineering RGB color vision into Escherichia coli. Nature chemical biology, 13, 706-708.
6. Li, H. M., Culligan, K., & Chory, D. J. . (1995). Cue1: a mesophyll cell-specific positive regulator of light-controlled gene expression in arabidopsis. The Plant Cell, 7(10), 1599-1610.
7. Ohlendorf, R., Vidavski, R. R., Eldar, A. , Moffat, K. , & M?Glich, A. . (2012). From dusk till dawn: one-plasmid systems for light-regulated gene expression. Journal of Molecular Biology, 416(4), 0-542.
Introduction to Cas1-Cas2
CRISPR and Cas1-Cas2 can establish an immunity system in cells in order to avoid virus invasion. When a foreign DNA fragment invades the cell, Cas1 and Cas2 form a stable complex, catch the fragment, and integrate it into the CRISPR array as a new spacer. With molecular memory formed during this process, the cell may have the resistance when the virus invades it the second time.
References:
Xiao, Y., Ng, S., Nam, K. H., & Ke, A. (2017). How type II CRISPR–Cas establish immunity through cas1–cas2-mediated spacer integration. Nature, 550(7674), 137.
Nu?Ez, J. K., Kranzusch, P. J., Noeske, J., Wright, A. V., Davies, C. W., & Doudna, J. A. . (2014). Cas1-Cas2 complex formation mediates spacer acquisition during CRISPR–Cas adaptive immunity. Nature Structural & Molecular Biology, 21(6), 528-534.
Yosef, I., Goren, M. G., & Qimron, U. (2012). Proteins and dna elements essential for the
CRISPR adaptation process in escherichia coli. Nucleic Acids Research, 40(12), 5569-
5576.