Everyday Chirality

Bean There Done That

It has been a long and wet spring, but I am happy to report, we saw the sun for brief moments the last day or two.  Though the weather has not been good for morale, it has been good for the water bill and the back yard garden.  Along with knee-high grass, the kohlrabi, lettuce, and carrots are off to a good start.  After a disappointing failure last year at growing beans, I gave it another try. I am happy to report that at this moment they are thriving.

In the background, you will see a second stalk.  This is my second attempt to train it onto the trellis.  I hooked it on yesterday, but I hooked it on the left side of the pole.  When I came out today, it had pushed itself off trying to curl to the left.  At first, I mumbled, "Silly beanstalk, turn right" forgetting that right turns are not the forte' of creatures in my care.  So today, I trained it to the right side of the bar.  I guarantee it will be wrapping its way up the trellis tonight.

Here is a time lapse video of beans growing.  Notice the same spiral turn as it searches for the next link of the fence:

Now that might seem strange to non-gardeners. Why will it only turn left?  Well, beanstalks, like many things in nature are what chemists call chiral.

The Right Way:

Chirality is a trait of objects often referred to as "Handedness."  This comes from looking at your hands.  You have a right and left hand.  They are mirror images of each other, but you could never make them match up or superimpose on each other.  Superimpose  is not easy to grasp, but I liken it to ghosts in cartoons that enter someone else.  The ghost left hand has to enter the person's left hand to move it.  Well the ghost left hand can never overlap with the right hand or the thumb would be sticking out the wrong side or be upside down.  You can try this.  Put your palms together...your hands are mirror images.  Put your right hand on top of your left hand so that your four fingers are aligned... thumbs on opposite sides. Your hands are chiral!

The structures above are mirror images (wedges are out and dashes back), but will never be able to perfectly overlap, (a thumb will always be hanging off the side). Try lining up any two groups, the other two will be reversed.  This is common in many biological molecules. It comes from a change in ONE ATOM! Four different groups around ONE ATOM can determine whether a molecule smells like spearmint or caraway!  If you want to see the structure of this molecule, check out the post on terpenes.  (S)-carvone is caraway, (R)-carvone is spearmint.  All due to a single atom like above.
Living things are oozing with chirality.

Chemists use terms like D and L, R and S, or P and M to assign whether molecules turn to the right or left respectively.  That discussion is for another day... but in practical application it is mind-boggling how nature works.  Almost all amino acids in your body (the molecules that make up proteins) are only one type of chirality, which we call L. Statistics would say that we should have a 50/50 mixture of L and D, but that is not the case. Somewhere in the world's history, an L-molecule was formed and cascaded through all life on the planet. All DNA helices twist the same way (we call it R or P). This is the same as the beanstalk!

Here is a picture off of Wikipedia:

http://en.wikipedia.org/wiki/File:ADN_animation.gif

My Steak is Chiral?

All the proteins in your steak are made of chiral molecules.  When you go to grill it, you find even more chirality. Engineers use chirality to their advantage to make sure you use proper adapters for flammable gasses. Screws, nuts, and bolts are all chiral.  The old adage, "Righty-tighty, Lefty-losey" only exists because someone chose it by convention. To read about the history, click HERE. Some flammable gas regulators are threaded "lefty-tighty, righty-losey" to prevent you from accidents. No washing machine hoses on the propane tank! You may want to revisit the post Time for Grillin'!

Imagine if you had to buy light-bulbs based on whether you had sockets that turned left or right, someone had to choose that you can screw them in clockwise.

That reminds me of a joke.  How many professors does it take to screw in a lightbulb?  None, they call it "research on chirality" and ask the students to do it. 

All that aside, I am trying to get the comment board fired up this month.  If you run in to some unexpected chirality, post it below.  Let's see what we can find together. 

1. Beanstalks

2. My shoes

3. The cap on my Leinie's Summer Shandy

4. The rest is up to you...