Team:BIT-China/Project/Description
Description
SWEETNESS AND WE
Sweetness, a pleasurable taste associates with happiness and satisfaction.
For most animals including human, it seems innate to be addicted to sugars and some other sweeties.
When we were just babies in the warm embrace of moms, breast milk came firstly as a gift containing galactose which also survived us.
In the Victorian era, some British people ate excessive sweet food thus their tooth were decayed, which was regarded as a symbol of high status in society etcetera.
In some tribes nowadays, people still managed to get honey under the risk of being stung.
As a matter of fact, modern science has demonstrated that our love to sweetness is due to our genes.
Our brain will release serotonin when we take sugar, which makes us feel delightful.
WELL WHY?
Sugar is essential nutrient for everyone.
However, according to the World Health Organization (WHO), having excessive sugar is even more harmful than smoking.
Having excessive sugar may not only cause obesity, but also trigger diseases, such as diabetes and gout.
We need to satisfy our brain with sweet things, nevertheless, metabolizable sugar with enough sweetness usually has high calories at the same time.
Therefore, the demand for seeking sweeteners containing both high sweetness and low calories is quite urgent.
To detect substances’ sweetness and find new ideal sweeteners, people have done a lot.
At the very beginning, saccharometer was used to physically measure the refraction simplicity, but it is not accurate and can only work on the carbohydrate.
Then some people were hired and trained as professional tasters to tell the sweetness of each particular sugar. But it’s really costly and time consuming.
Although there are several other current methods to test how sweet the sugars are, there remains limititions from labs to society.
Thus, it is really urge for us to create a new convenient and effective way to test the sweetness and find more available sweetners.
However, according to the data from the World Health Organization (WHO), having excessive sugar is more harmful than smoking. Having excessive sugar can not only cause obesity, obviously, but also can trigger diseases, such as diabetes and gout.
With the development of technology, artificial sweeteners are becoming better choices. The production technology of artificial sweeteners is becoming more mature. Meanwhile ,as a food additive, artificial sweeteners are also more widely used in the field of food production. But the potential harm of artificial sweeteners to humans is still a controversial issue.
Therefore, it is imperative to detect the ideal sweetener to tackle the problems we mentioned above as well as satisfy our gustation.
THEN WHAT?
With the development of synthetic biology, the types and production of natural products of microbial synthesis are increasing. Does the natural product produced by the microorganism contain some undiscovered sweeteners? Thus we hope to design a system which can identify sweeteners and be able to distinguish the sweetness of these substances by corresponding signal expression.
First and foremost,we must understand the mechanism that people can feel sweetness: the human sweet G protein-coupled receptor T1R2-T1R3. It is a pair of extracellular proteins with homodimer，which has six structural domains. Different sweet substances combine with different regions of T1R2-T1R3，then triggering intracellular G protein coupled pathway and leading to downstream signal expression. Finally, it can lead to a "sweet" feeling.
At the same time, we chose yeast cells as host. We hope to replace its original G protein-coupled receptor Ste2 , which is related to yeast’s mating with the T1R2-T1R3. And some side effects genes are knocked out by homologous recombination technology. After building a complete system, we hope to judge whether the material has sweetness according to whether the signal can express. If there is a response, we hope to judge the sweetness of the substance by the strength of the signal.
BUT HOW?
Our experimental part is divided into three parts:
Host Reconstruction: host reconstruction group uses homologous recombination methods ,using Trp, His, and Ura as screening marker fragments with homologous arms to knock out Ste2, Sst2, and Far1 genes in yeast.Except Ste2 , Sst2 gene can inhibit the signal transduction of Gpa1 protein.Far1 gene avoids interference signal for sweet yeast yeast normal physiological function after transformation.
Receptor Expression: the receptor expression group uses OE, PCR, and other methods to achieve the synthesis of T1R2-T1R3 G protein coupled receptors. The detection team constructed the pFUS and the red fluorescent protein line to detect the sweetness and sweetness functions through the expression of the fluorescent signal.
Detection of Circuit:in combination with our project, our mathematical modeling also establishes three sets of models that provide guidance for our experiments and achieve the desired functional simulation.
