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Sunday, August 26, 2012

Chirality revisited

As a break from our harsh Canadian winters we ‘went south’ to the Caribbean islands for many years. I love beach combing and as a result, I have baskets full of sea shells at the cottage that I have picked up and enjoy handling.

When I read that spiral shells were a good example of the invisible chirality [left or right handedness] that many molecules in living systems possess, I lined up some of my spiral shells with their earliest growing tips down and took the picture on the left. When you look at the picture, you can’t help but see that the open ‘mouth’ of the shell is always on the left.

Try it out yourself the next time you have any spiral shells at hand, and you may be lucky enough to find a shell that breaks the rule and opens on the right. They are rare, but exceptions do exist, and therefore the shell's outward chirality must be for another reason, because our body’s chiral molecules are always only one-handed without exception! For snails, the reason for the shell coiling happens to be sex. Snails make coiled shells because their sexual organs are usually twisted, and it is difficult with snails of opposite handedness to mate. Picture on the right is the Nautilus shell.

The fact that our body’s DNA, enzyme and sugar molecules, etc., are chiral was not generally known until a widespread medical tragedy occurred. In the late 1950’s, a drug called ‘thalidomide’was developed by a pharmaceutical company as a sedative and a treatment for morning sickness in early pregnancy. When tested on animals it had few or no side effects, and so was used in many countries, including the UK and Canada starting in 1958. It was not until 1961 that doctors fully realized the drug was the cause of severe birth defects – many children developing flippers instead of arms.  It was withdrawn but too late for kids shown on the left .

When thalidomide was investigated, the results knocked organic chemists for a loop. It was discovered that the molecule was chiral, and when synthesized in the lab, equal amounts of two isomers, one left-handed and the other right-handed, were produced. Because molecules involved in our body chemistry are also chiral, the two isomers reacted differently, with one isomer causing the birth defects. Fortunately, under normal circumstances, if we ingest a molecule with the wrong handedness, our bodies recognize it and - unlike the unfortunate thalidomide case where a fetus was in an early stage of development - it is sent to the liver where most toxins are dealt with.

The development of one-handedness in our body chemistry probably happened just by chance when life first formed on our planet. Should we ever travel to another planet many light years away, it is possible that life started there with its molecules having the opposite handedness, and we could eat as much of their food as we wanted, but we would starve to death! Rie

Sunday, August 19, 2012

Fishing Revisited

My Dad grew up on the famous Restigouche River, and as a child in the 1930’s, I can remember him coming home after a day on the river - and when he'd open up the trunk of his car with a flourish, there would be 5 or 6 beautiful 30 to 40lb. salmon gleaming in the sun!!  I’ve read that the top 10% of anglers catch an amazing 90% of all fish, and I’m sure my father was among that top 10%! 

Even so, I think he would have been intrigued if he had known that the fish’s blood circulation system is very different from land creatures who have lungs. When we fill our lungs with air it oxygenates the blood which then goes directly to the heart from where it circulates to the rest of the body.  
As the simple diagram on the right shows, a fish basically has a closed-loop circulation system with its heart pumping the blood in a single loop around the body. Starting with the gills that act as the fish’s lungs, the red lines in the picture show where the oxygen-carrying blood flows. The oxygen is depleted as the muscles work and the black lines show places where little or no oxygen is left in the blood. But the heart itself is a muscle, and if the fish is using it's muscles fighting hard to get free of a fisherman's  hook, all the oxygen is used up and when the blood reaches the heart, it actually stops so the fish cannot move until the heart recovers and again supplies them with an adequate oxygen supply. 
Any fisherman who has fought to land a large fish will recognize the pattern of keeping the line taught to play the fish and reeling it in when the fish is recovering. 
You have little chance of landing a salmon unless you always keep your line tight - but not so tight that it breaks! If a light ‘leader’ line that is less visible in the water is used [my father would have used a 6 to 8 lb. test line], a big salmon can easily break it. So you have to let the salmon run as many times as it can with just the right tension on the line to deprive its heart of oxygen temporarily so that you can reel it in part way. A big fish can sometimes take up to an hour to land. And after all that, if you are trying to scoop up half dead fish with a net, it is easy to lose it as it comes to life and takes off. 

As fishermen say, 'tight lines.' Rie

Sunday, August 12, 2012

Big Voice Revisited

When we were in the Parrsboro area in Nova Scotia last week, we found the very small town of Parrsboro itself an exceptionally interesting place. It has seen more prosperous days - when coal mining, lumbering, and shipbuilding kept the area thriving. Now tourism is a big draw in the summer, since the area boasts the natural wonders of the world's highest tides and famous fossil cliffs. We found as well a surprisingly large group of interesting and knowledgeable people. They run the museums, professional theatre, 'Rock Shops' [with extensive mineral collections and good prices] and the Bed & Breakfasts in the grand old wooden homes built in the booming days in the late 1800's.

The last night of our trip we ended up at a B&B run by a music teacher and his wife, who just happens to be an opera singer. After our ample breakfast and some persuasion, she was gracious enough to sing for us. She stood in the living room so that the archway from the dining room formed a frame that made her seem 'on stage' to us. After chatting for a few minutes, she opened her mouth to sing and produced a sound so powerful it nearly blew us out of our seats.

She sang beautifully, and while she projected her voice with such force, we marveled at how long she could sing without taking a breath. My mother was a trained singer, and I remember her often telling us to sing from our diaphragm. This is a very large muscle tucked under your rib cage. When you breathe in deeply to fill your lungs, that's the muscle you use. Try it. Trained singers increase their lung capacity and learn to strengthen their diaphragm and control the amount of air they release to pass through their vocal cords.

Being conscious of your mouth positions, say slowly: ‘please talk loud’. Now take a deep breath, consciously use your diaphragm muscle, and say the same expression again. Are you surprised that your voice is more powerful, and that you could easily make yourself heard above a crowd? Again being conscious of your mouth positions, sing: ‘please sing loud’. If you’ve been learning as you’ve done this exercise, you’ll now have figured out the difference between talking and singing sounds. But I probably won’t be able to resist doing an entire post about sounds one day anyway.  Rie

Sunday, August 5, 2012

In the Cards Revisited

When my girls were school age, I started teaching High School chemistry and I loved it. However, it soon became clear that what I was trying to teach and what the kids were learning bore amazingly little resemblance to one other. I realized they needed to give me their undivided attention and also I had to figure out some way to repeat what I was trying to get across. I read an article once that said you have to hear something new - like a new word or concept – an average of 7 times before it is really yours. But with those teenagers in front of me, it would be game over if I started repeating myself.

I’d say: “Chemistry is easy if you can follow what I am talking about, but I have found out that most of you don’t seem to be getting it. That means either my teaching is not clear enough for you to understand, or you need to stop me and ask me questions.” That didn’t work - I rarely got a question because they were not sure enough of what to ask and didn’t want to look stupid in front of their classmates. So quite a few students were getting lost and nothing I did seemed to work.

Then I happened on the idea of using cards with a students' names written on the back.  At the beginning of a class, I would get one student to shuffle that class's cards and another to cut the deck. I’d tell them I was going to talk for around 10 minutes about something new they really needed to understand and that I would write any new words I used on the board. When I had finished, I would then ask the person whose name was on the back of the top card in the deck to tell the class what I had just said.

No one knew whose name was on that top card, and suddenly I had a captive audience paying rapt attention - a joy to teach. Very often the kids on those first couple of cards would get so hopelessly muddled over a point that hands would shoot up - so I'd thank the student and turn up another card. Usually after we were 4 or 5 cards into the deck, there would usually be a request that I repeat some of what I had tried to teach in the first place. My classes oftentimes became pretty lively, sometimes they seemed on the edge of chaos with students vehemently discussing and arguing with each other, but as long as they were talking chemistry I’d let them go. Inevitably the topic always got a thorough airing and in the end, most were using the words on the board to talk about the new ideas I was trying to get across.  Best of all - they were involved in their own learning and and they loved it. 

Like Confucius said – Involve me and I'll understand. Rie