Thursday, October 15, 2009

Killing time, among other things

Right now I'm in the middle of an assay. I've finished all the hard parts and now I just have to wait for certain time points to collect the data. This assay in particular is call a DPPH assay (DPPH stands for 2,2-Diphenyl-1-Picrylhydrazyl, or really long name for a "stable" free radical). I'm measuring total antioxidant capacity of grape extracts. And since I'm killing time and free radicals, I'm going to explain how it works and what I do!! Fun, no?

So a free radical is a type of chemical molecule that is technically unstable. It has an unbalanced positive charge and will steal it from anywhere it can get it. In your body, it's your cells (which creates damage). Over time, if free radicals aren't "quenched", if could lead to things like cancer, or so they say. The quenching occurs when an antioxidant (which has an extra negative charge) donates an electron to the free radical's cause. It then becomes chemically happy and won't cause any further damage. Photo courtesy of

There are lots of different kinds of antioxidants and there are other assay that measure specific ones (like when I worked with the purple sweet potatoes, one assay I used was a total phenol antioxidant assay). The DPPH assay is a measure of all antioxidant capacity. And in the assay I've been running lately, I've been measuring green tea, black tea, EGCG, red grape extracts and white grape extracts. The grape extracts I've been specifically looking at are Nobel and Carlos which are popular in wine making (which is where we got our extracts).

So in my assay, I make up a solution of DPPH. I put quotes around stable earlier because the inherint nature of free radicals are to be unstable, but DPPH has a known, measurable and linear quenching in the presence of Trolox. So I make a standard curve with the trolox and DPPH solutions. I also make up different dilutions of my grape extracts and add DPPH to them too. I let them incubate in the dark for 90 minutes, taking spectrophotometric readings at 30, 60 and 90 minutes. After I've taken the readings I create my cruve (which is actually a straight line) and compare the values I received from the spectrophotometer (also known as the absorbance) and see where they fall, if at all, on my line. If I've diluted my samples enough, they should fall on that line and then I can tell you how much trolox my sample is equivalent to in quenching DPPH.

Neat, huh? Ok, so I know most of you haven't even made it this far and I'm sorry, but I don't have much else I can do right now. I suppose I could've been blogging about the state fair and the candle I entered into the crafts competition, but I didn't think about that until after I had written this whole long entry. Oh well. I hope to find out if I one anything soon! Look for my candle in the hobbies and handicrafts building (after you get some ice cream at the NCSU Dairy Bar)! It's a white pillar candle with green leaf images stamped onto it and brown ribbon at the top and the bottom of the candle. I hope I win!!

1 comment:

  1. wow, I don't know what to say. That's more info I than I ever thought I'd care to know but you are amazing to understand and enjoy all of it! I hope you win with the candle! We plan on entering things in our fair next year. I thought the kids would make a great entry!!haha


Related Posts Plugin for WordPress, Blogger...