Suddenly, the use of 5-ethylthio-1H-tetrazole (S-ethyltetrazole) is increasing by leaps and bounds. What's going on here? Is a new rambo activator being born? This product has been lurking in our catalog for some time, so why the sudden interest now? Well, the explanation is fairly simple. Several articles have recently been published extolling its virtues as an activator.(1,2,3) But what particular attributes make it special compared to the tried and trusty veteran, 1H-tetrazole? The presence of the ethylthio group makes it significantly more acidic than tetrazole and this improves its ability as an activator. Ethylthiotetrazole is also considerably more soluble in acetonitrile than tetrazole. A more concentrated solution offers the possibility of better activator performance. However, concentrations from 0.25M to 0.75M are reported in the literature, so what is the optimal concentration?
We have now compared the performance of ethylthiotetrazole at various concentrations in acetonitrile with our standard tetrazole product in a series of low scale (~1 µmole) syntheses. The water content of the solutions was always < 25ppm. DNA synthesis performance was determined by DMT assay and RP HPLC analysis of the resulting oligonucleotides, while RNA synthesis performance was determined by DMT yield alone. We found that a 0.25M solution of ethylthiotetrazole performs better than 0.45M tetrazole solution in DNA synthesis but a marked improvement was observed in the results of RNA syntheses. Results of this study are shown in a report on our world wide web site: Activator Caomparison.
Throughout the year, supplies of ethylthiotetrazole from the manufacturers have been plagued with high moisture content and particulate contamination. We will continue to offer the powder only if it will allow acceptable solutions to be produced. We will also be offering a solution at 0.25M concentration with a water content specification of ~ 50ppm for better control and performance.
(1) B. Sproat, et al., Nucleosides and Nucleotides, 1995, 14, 255-273.
(2) D. Tsou, A. Hampel, A. Andrus, and R. Vinayak, Nucleosides & Nucleotides, 1995, 14, 1481-1492.
(3) F. Wincott, et al., Nucleic Acids Res., 1995, 23, 2677-2684.
