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Report YES assay - general toxicology
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This document contains the practical report of the YES assay. This practical was carried out during the course of general toxicology.
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YEAST ESTROGENASSAY
General toxicology – TOX2030
Suzie Rademakers & Mette Daamen
1049319 - 1049804
20-9-2021
, Aim of the assay
In this experiment E2, which is a type of estrogen, is used. Also Bisphenol A (BPA) and
diethylstilbestrol (DES) are used, these are estrogen-like compounds (1). The aim of the assay is to
measure the estrogenic activity of the chemicals, this is done with the yeast estrogen (YES) assay (2).
When an estrogen-like compound binds to the corresponding receptor it induces transcription of lacZ
and therefore the production of β-galactosidase. This is also shown in figure 1. β -galactosidase
transforms the substrate CPRG to a red product. This red product can be measured at a absorbance
of 570 nm.
The absorbance is also measured at 690 nm during the experiment. This reflects the amount of yeast
in each well (cytotoxicity). Therefore an effect on viability of the chemicals can also be evaluated.
Figure 1 binding of an estrogen like-compound causing a serie of reactions (1)
The aim of the assay is to investigate which estrogen-like compound (BPA or DES) is the most similar
as E2 and therefore can cause the most damage.
Results
Table 1: The used and exposure concentrations of E2 (nM), BPA (mM) and DES (μM). During the
experiment, the used concentrations are being diluted twice. Firstly, the exposure media is made by
adding 20 μl of each compound is to 480 μl medium + CPRG. Afterwards, 100 μl were added in 100 μl
of yeast in each well. This means that the actual exposure concentration is diluted 50 times and
therefore can be calculated by dividing the used concentration by 50.
E2 concentration (nM) BPA concentration (mM) DES concentration (μM)
Used Exposure Used Exposure Used Exposure
concentration concentration concentration concentration concentration concentration
0,050 0,001 0,010 2,00 x 10-4 0,002 4,00 x 10-5
0,100 0,002 0,100 0,002 0,005 1,00 x 10-4
0,500 0,010 0,250 0,005 0,010 2,00 x 10-4
1,00 0,020 0,500 0,010 0,020 4,00 x 10-4
5,00 0,100 1,00 0,020 0,200 0,004
10,0 0,200 2,50 0,050 2,00 0,040
50,0 1,00 5,00 0,100 20,0 0,400
500 10,0
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