Team:Harvard/flavor/results

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Revision as of 06:21, 25 October 2010



confirmation results

The two flavors that are currently ready for transformation into plants are the "taste-inverter" miraculin and the sweetener brazzein. Given the long time-frame of plant transformation we used two different assays in E. Coli to confirm that our proteins could indeed be transcribed and translated. The results of those assays are shown here.

Confirmation with YFP-2x Tags

In order to confirm that the Miraculin and Brazzein are able to be expressed in E. Coli we attached a YFP-2x tag sequence to the termini of both proteins. The proteins were placed under an IPTG-expressible promoter and used spectrophotometry to determine the level of YFP fluorescence against a baseline, untagged protein. Figure 1 shows relative-fluorescence at times post induction. In all circumstances the levels of YFP-fluorescence increased.

Figure 1   click to enlarge


Figure 1. Induced expression of YFP-tagged Miraculin and Brazzein in E. Coli
Figure 1 (A) through (D) are normalized plots of Miraculin and Brazzein YFP-fused constructs expressed in E. Coli. YFP-2x tags were attached to both N- and C- termini to ensure that folding was not hindered. In all cases relative YFP fluorescence had appreciably increased after 120 minutes as compared to the non-induced E. Coli

Confirmation with Western Blot

A western blot assay was performed to check for E. Coli expression of Miraculin and Brazzein. Proteins tagged at either the N- or C- terminus were placed under the control of an IPTG-inducible promoter. In the miraculin assay, no protein expression was seen. It is possible that the protein does not express well in E. Coli, or that the plant-specific codon optimization of the proteins resulted in reduced expressibility. Brazzein, specifically C-terminus tagged brazzein was seen to be highly expressed in E. Coli.

Figure 2   click to enlarge


Figure 2. Western Blot of Miraculin and Brazzein Expression in E. Coli
Proteins were tagged using a StrepII standard Antibody tag, attached to both N- and C- termini. Miraculin (A) does not appear to have been expressed in high enough quantities to be visualized. The expected protein weight is 25 kDa. Brazzein (B) shows strong expression of a protein in the 10-15 kDa range. Brazzein has an expected weight of 6.5 kDa, a discrepancy that we have attributed to inconsistencies in the gel.

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