folate leads to increased ratio of deoxyuridine monophosphates (dUMP)/deoxythymidine monophosphates (dTMP) and uracil misincorporation into DNA and eventually low production of DNA. Uracil can be used for drug delivery and as a pharmaceutical. When elemental fluorine reacts with uracil, they produce 5-fluorouracil. 5-Fluorouracil is an anticancer drug (antimetabolite) used to masquerade as uracil during the nucleic acid replication process. Because 5-fluorouracil is similar in shape to, but does not undergo the same chemistry as, uracil, the drug inhibits RNA transcription enzymes, thereby blocking RNA synthesis and stopping the growth of cancerous cells. Uracil can also be used in the synthesis of caffeine. Uracil has also shown potential as a HIV viral capsid inhibitor. Uracil derivatives have anti-tubercular and anti-leishmanial activity. Uracil can be used to determine microbial contamination of tomatoes. The presence of uracil indicates lactic acid bacteria contamination of the fruit. Uracil derivatives containing a diazine ring are used in pesticides. Uracil derivatives are more often used as antiphotosynthetic herbicides, destroying weeds in cotton, sugar beet, turnips, soya, peas, sunflower crops, vineyards, berry plantations, and orchards. In yeast, uracil concentrations are inversely proportional to uracil permease. Mixtures containing uracil are also commonly used to test reversed-phase HPLC columns. As uracil is essentially unretained by the non-polar stationary phase, this can be used to determine the dwell time (and subsequently dwell volume, given a known flow rate) of the system. References External links Uracil MS Spectrum Nucleobases Pyrimidinediones