Balance the tubes by adding isopropanol or extraction buffer. Produce a pellet of DNA by centrifuging at 15,000 rpm for 15 min. Gently pour off the supernatant and lightly dry the pellets by inverting the tubes on paper towels for 1-2 min.
Onions not only provide flavor, they also provide important nutrients and health-promoting phytochemicals. High in vitamin C, onions are a good source of dietary fiber, and folic acid. They also contain calcium, iron, and have a high protein quality (ratio of mg amino acid/gram protein). Onions are low in sodium and contain no fat. Onions contain quercetin, a flavonoid (one category of antioxidant compounds).
Onions and the Cardiovascular System. Onions share some of the health benefits of garlic, which many of us know are good for thinning the blood. Both foods contain sulphides which can help to lower blood lipids and blood pressure. Onions help to prevent blood clotting as they contain flavonoids and other substances which when consumed can dramatically reduce the risk of cardiovascular disease.