Phenolphthalein is colourless in acid but turns a deep pink in a basic solution. In this case, though, the important feature is that phenolphthalein can be reduced with zinc into colourless phenolphthalin, which along with a base is present in the test reagent. In the usual process, a drop of alcohol is added to an unknown stain to dissolve any hemoglobin that may be present, followed by rubbing with a swab that has been treated with the Kastle-Meyer reagent. A drop of hydrogen peroxide is then applied to the swab.
If hemoglobin is present, the hydrogen peroxide decomposes to yield oxygen that in turn oxidizes the phenolphtalin to phenolphthalein. Since the solution is basic, a pink colour develops indicating the presence of blood. The test is very sensitive, but is not specific for human blood. Animal blood will also yield a positive reaction as will oxidizing agents such as some metal ions. The technique is to spray the suspect area with a solution of luminol and hydrogen peroxide.
If blood is present, the peroxide will yield oxygen that then reacts with luminol to produce a blue glow. This reaction was first noted in by the German chemist H.
Albrecht and was put into forensic practice in by forensic scientist Walter Specht. Even dried and decomposed blood gives a positive reaction with the blue glow lasting for about 30 seconds per application.
The glow can be documented with a photo but a fairly dark room is required for detection. The reaction is so sensitive that it can reveal blood stains on fabrics even after they have been laundered. In one case, a pair of washed jeans with no visible stains gave a positive test with luminol on both knees. A study of residential dishwashers found that 83 percent of the dishwashers they tested were positive for fungi, and 47 percent of dishwashers tested contained the black yeast E.
Many home care blogs recommend this trick to clean your kitchen sink: Wet the surface of your sink, then scrub it with baking soda sprinkled onto a sponge. According to The Ohio State University Extension , cleaning counters with undiluted hydrogen peroxide is effective at killing E.
Carrots, potatoes, and other tough-skinned veggies can be soaked 30 minutes before rinsing and drying. Because bacteria can cause vegetables and fruits to turn brown, a hydrogen peroxide bath is believed to keep them fresh longer in your fridge. If your cookie sheets, pots, and pans have a baked-on layer of brown, Jill Nystul of the blog One Good Thing recommends sprinkling them with baking soda, then spritzing the soda with 3 percent hydrogen peroxide will restore them.
Allow them to soak for 1 to 3 hours before wiping off the mess. After washing the garbage can with soap and water, spray the whole container with a solution of hydrogen peroxide and water.
Let the trash can sun-dry for several hours. According to the CDC , hydrogen peroxide is effective at removing microorganisms, including bacteria, yeasts, fungi, viruses, and spores, making it a good choice for cleaning your bathroom. Spray a solution of water and hydrogen peroxide onto glass surfaces, then wipe with paper towels, a lint-free cloth, or newspapers for a streak-free clean. To kill them without having to breathe in toxic bleach fumes, spray with undiluted 3 percent hydrogen peroxide and allow it to sit for 30 minutes.
The peroxide will kill the mold and mildew, but you may still need to remove the stains they left behind. If your porcelain pedestal sink has yellowed, you can brighten it by scrubbing the dampened sink surface with baking soda, then scrubbing with a sponge saturated with 3 percent hydrogen peroxide.
When the bubbles subside, scrub the surface of the shower with the mixture. Take care! Hydrogen peroxide can cause redness and burning. The Environmental Working Group recommends hydrogen peroxide as an effective way to remove grass stains, blood stains, and drink stains like fruit, juice, and wine.
Try dabbing the cleaner on the reverse side of the fabric to start. Nystul also has a solution if your T-shirts, sheets, and towels have taken on a grimy, gray hue. Start the cycle, allow the washer to fill, and soak the clothing for a couple of hours before finishing the cycle to whiten and sanitize.
Swab a swatch first. Before you try hydrogen peroxide on any fabric, test a small, out-of-the-way section for color fastness. Numerous studies have shown that soaking seeds in 1 to 3 percent hydrogen peroxide can soften the seed coat and start germination. If you want to increase the chances of a good plant yield, you can soak seeds in hydrogen peroxide for 20 minutes before planting.
If you have a water feature or koi pond, you can safely treat the water to reduce or remove harmful algae. If your garden vegetables are suffering from powdery mold or other fungal infections, you can spray them with a hydrogen peroxide solution to rid them of the fungus.
Mix 4 teaspoons of hydrogen peroxide in a pint of water and spray the plant. If your pet has eaten something poisonous, your veterinarian may advise you to use hydrogen peroxide to make the animal vomit. Let it sit for 15 minutes before rinsing, drying, and replacing the litter. Some aquarium hobbyists use hydrogen peroxide to control algae and clean their tanks, but talk to a fish veterinarian before putting hydrogen peroxide in your tank.
But the FDA warns that getting hydrogen peroxide on your skin may cause irritation, burning, and blistering. Prx actually has a dual role in the process.
Its usual job is removing excess hydrogen peroxide from the cells by converting it to water. But if levels get dangerously high -- and Prx needs help -- it becomes inactive in its "converting" job and instead becomes a "signaler," telling the cell to produce or activate other proteins to help remove the excess. But how does Prx revert back to its usual job and become active again, so that it is available for a new wave of hydrogen peroxide?
In , scientists reported that a protein known as sulfiredoxin Srx was involved in the process. The goal of Lowther's team was to use X-ray crystallography to learn exactly what happens. The scientists knew that the repair of Prx would involve it binding with Srx. They also knew that the structure of Prx would need to change because the portion of the molecule that is repaired by Srx is initially hidden when it is in the inactive form.
The scientists said that understanding this protective mechanism that keeps cells healthy may one day help reveal how the process goes awry in disease. They will continue the research by studying how the structural change may affect how Prx interacts with other proteins.
Lynnette C.
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