Revision as of 20:35, 19 October 2016

T7Promoter+RBS+Sf1a+linker+6X His-Tag

Introduction:

Figure 1.T7 promoter+RBS+Sf1a+linker+His-tag+terminator

      By ligating the IPTG induced promoter T7 (BBa_ I712074), strong ribosome binding site (BBa_B0034), sf1a, linker, and the 6xHistag (BBa_ K1223006), we can express Sf1a, the toxin by IPTG induction .
      This year we create a revolutionary system that integrates biological pesticides, an automatic detector, a sprinkler, and IoT. We made a database that contains most of the spider toxins and selected the target toxins by programming. U2-segestritoxin-Sf1a is coded for the venom of a spider, Segestria florentina. It is under the control of the strong T7 promoter. A 6xHistag is added for further protein purification.

Mechanism of Sf1a

      U2-segestritoxin-Sf1a has a structure called ICK(inhibitor cysteine knot). This kind of structure contains four disulfide bonds. With this structure, Sf1a can resist the high temperature, acid-base solution and the digest juice of insect gut. Sf1a can bind on insect voltage-gated sodium channel Site-1, making it paralyze and die eventually.

Features of Sf1a

1. Non-toxic: U2-segestritoxin-Sf1a is non-toxic to mammals and bees. Since the structure of the target ion channel is different, U2-segestritoxin-Sf1a does not harm mammals and bees. So it is safe to use it as a biological pesticide.

2. Biodegradable: The toxin is a peptide, so it must degrade over time. After degradation, the toxin will become nutrition in the soil.

3. Species-specific:According to reference, U2-segestritoxin-Sf1a has specificity to Lepidopteran (moths) and Dipteran (flies). So another insect such as bees will not be killed.

4. Eco-friendly: Compare with a chemical pesticide, U2-segestritoxin-Sf1a will not remain in soil and water so that it will not pollute the environment and won’t harm the ecosystem.

      Together, using Sf1a is totally an environmentally friendly way for solving harmful insect problems by using this ion channel inhibitor as a biological pesticide.

Target insect:

Figure2

Experiment

1. Cloning :
After assembling the DNA sequences from the basic parts, we recombined each T7 Promoter+B0034+toxin +linker+6xHistag gene to pSB1C3 backbones and conducted a PCR experiment to check the size of each part. The DNA sequence length of these parts is around 250-500 bp. In this PCR experiment, the toxin product's size should be near at 450-700 bp.

Figure 3.

2. Expressing:
E.coli(DE3) express the protein and form the disulfide in the cytoplasm. We sonicated the bacteria and purified the protein by 6xHis-tag behind the toxin using Nickel resin column.

3. Analysis:
We do the Bradford analysis to get the protein concentration.

Figure 4.

Figure 5.

Also, we use tabacco cutworm to test it's effect. Accoding to the Histogram show below, the dose response proof that Sf1a is really work. The negative control are water and the positive control are commercially available pesticides. Leaves in the table are direct results.

Figure 6.

Figure 7.

4.Modeling:
According to reference, the energy of Ultraviolet will break the disulfide bonds and the toxicity is also decreased. To take the parameter into consideration for our automatic system, we modeled the degradation rate of the protein and modified the program in our device.

5. Device:
We designed a device that contains a detector, a sprinkler, and an integrated hardware with users by APP through IoT talk. We use an infrared detector to detect the number of the pest and predict what time to spray the farmland. Furthermore, other detectors like temperature, humidity, lamination, pressure of carbon dioxide are also installed in our device. At the same time, the APP that displays all the information about the farmland would contact the users and spray biological pesticides automatically. This device can make farmers control the farmland remotely.

Sequence and Features