DNA Figures and Discussion
DNA is a polymer. The monomer units of DNA are nucleotides, and the polymer is known as a "polynucleotide." Each nucleotide consists of a 5-carbon sugar (deoxyribose), a nitrogen containing base attached to the sugar, and a phosphate group. There are four different types of nucleotides found in DNA, differing only in the nitrogenous base. The four nucleotides are given one letter abbreviations as shorthand for the four bases.
Adenine and guanine are purines. Purines are the larger of the two types of bases found in DNA. Structures are shown below:
The 9 atoms that make up the fused rings (5 carbon, 4 nitrogen) are numbered 1-9. All ring atoms lie in the same plane.
Cytosine and thymine are pyrimidines. The 6 stoms (4 carbon, 2 nitrogen) are numbered 1-6. Like purines, all pyrimidine ring atoms lie in the same plane.
DNA is a normally double stranded macromolecule. Two polynucleotide chains, held together by weak thermodynamic forces, form a DNA molecule.
Within the DNA double helix, A forms 2 hydrogen bonds with T on the opposite strand, and G forms 3 hyrdorgen bonds with C on the opposite strand.
The helix axis is most apparent from a view directly down the axis. The sugar-phosphate backbone is on the outside of the helix where the polar phosphate groups (red and yellow atoms) can interact with the polar environment. The nitrogen (blue atoms) containing bases are inside, stacking perpendicular to the helix axis.
The components
Note: in a nucleotide, the atoms of the organic base are numbered 1, 2, ... and the atoms of the sugar, wether it is a deoxyribose like in DNA or a ribose like in RNA, are numbered 1', 2', 5'. Atoms in the sugar component of a nucleotide provide the link between the base and the phosphate group. The 1' carbon is attached to the 9 nitrogen of a purine, or the 1 nitrogen of a pyrimidine. The OH (hydroxyl) group on the 5' carbon is replaced by a bond to the phosphate group (ester bond). DNA consists of two associated polynucleotide strands that wind together in a helical fashion. It is often described as a double helix. Each polynucleotide is a linear polymer in which the monomers 
Naming nucleosides and nucleotides:
DNA : some facts...
What's in a name
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http://pubs.acs.org/cen/editor/89/8912editor.html
What is it about the word “radioactivity” that drives otherwise rational people to utter panic?
As C&EN goes to press on March 17, Japan continues to reel in the aftermath of a devastating earthquake and tsunami. The situation at the Fukushima Daiichi Nuclear Power Station—shaken by the 9.0 earthquake and slammed by the tsunami—remains fluid and precarious. There have been explosions at the station, which has a total of six nuclear reactors. The cores of four reactors appear to have at least partially melted, and one could be on the verge of a major meltdown. Two storage ponds where spent reactor fuel is stored have been breached, and the spent fuel is in danger of catching fire. Desperate measures are being taken to try to prevent catastrophic failure of the reactors and storage ponds.
People living within a 20-km radius of the power plant have been evacuated; people living within a 30-km radius have been advised to remain indoors with their homes sealed and ventilation turned off. Tokyo Electric Power Co., which operates the station, has evacuated all but 50 of the 1,400 people who work at the plant. At one point on March 16, even those 50 brave individuals were withdrawn from the plant because radiation levels had spiked.
Around the world, politicians and commentators are pointing at Fukushima and insisting that the events there prove that nuclear energy can never be safe. In the March 15 Washington Post, the normally level-headed Anne Applebaum had an op-ed piece entitled “Time To Slow the Nuclear Rush.” She concluded that she hopes the Fukushima disaster “prompts people around the world to think twice about the true ‘price’ of nuclear energy, and that it stops the nuclear renaissance dead in its tracks.”
On the same op-ed page, columnist Eugene Robinson wrote: “Nuclear power was beginning to look like a panacea—a way to lessen our dependence on oil, make our energy supply more self-sufficient and significantly mitigate global warming, all at the same time. Now it looks more like a bargain with the devil.”
The March 15 Wall Street Journal included a story entitled “Potassium Iodide Runs Low As Americans Seek It Out” that describes a run on potassium iodide supplies by people worried that radioactive fallout from Fukushima could reach the U.S. Anbex Inc., which manufactures Iosat potassium iodide pills, quickly sold out its stock of more than 10,000 14-tablet packages on Saturday, the paper reported. Anbex President Alan Morris told the Journal, “Those who don’t get it are crying. They’re terrified.”
In Europe, legislators are calling for a referendum on the future of nuclear power and shutting down reactors. German elections a couple of weeks from now could be affected by the nuclear power issue. President Barack Obama felt the need to reiterate his support for renewed construction of nuclear power plants in the U.S.
Could everyone please get a grip? Thousands of Japanese are dead as a result of the earthquake and tsunami. Hundreds of thousands are homeless. A vast swath of northeastern Japan has been demolished; it is estimated that rebuilding will cost $35 billion or more. Japan’s economy has been dealt a devastating blow that will take months to years to recover from.
The fate of the Fukushima nuclear reactors and spent fuel storage ponds is important. The situation at the power plant is developing into a disaster that will affect many people’s lives, in Japan and likely around the world. What went wrong at Fukushima will have to be investigated thoroughly and understood to help prevent it from happening again.
But it will not be the end of the world, and it should not be the death knell for nuclear power. We live with risk. The risk of exposure to radiation from any one of a number of sources, including the partial or complete meltdown of the core of a nuclear reactor, is one such risk, quantitatively no different from any other. Nuclear power must be a component of the mix of energy sources for the world in the 21st century, the situation in Japan notwithstanding.
Thanks for reading.
http://pubs.acs.org/cen/editor/89/8919editor.html
This week’s issue contains six letters on nuclear power, a representative sample of the letters C&EN received in response to the editorial, “Resist Hysteria,” I wrote shortly after the earthquake and tsunami in Japan devastated the Fukushima Daiichi Nuclear Power Station (C&EN, March 21, page 5).
Four of the six letters take sharp issue with the primary point I made in the editorial, which was that, despite the severity of the situation in Japan, nuclear power remains an essential component of our overall energy mix for the near to mid-term because it will help us avert the worst impacts of global climate disruption.
The letter writers make a number of points that I think deserve consideration. Two raise the issue of disposal of nuclear waste. Mark Schauer writes: “At this time, no country on the planet has implemented a long-term solution to the problem of nuclear waste. I consider it criminally irresponsible to implement a process where you don’t know what to do with waste that remains hazardous for tens of thousands of years.”
And Gary Katz observes: “The failure to make any progress on nuclear waste disposal worldwide is underscored by the fact that to date only one small country—Finland—has a long-term storage depository constructed and ready for use. … [T]he U.S. government has scuttled two decades of work on its Yucca Mountain depository after an expenditure of many billions of dollars. This leaves all our reactors laden with the same lethal stores of spent fuel as at Fukushima.”
These are legitimate points. Nuclear waste is an intractable problem for which we have not developed an adequate solution.
That said, at least the nuclear waste is in temporary repositories and remains under human control, which is more than can be said of the waste from burning fossil fuel. That would be, for starters, carbon dioxide, the primary greenhouse gas that is inexorably disrupting Earth’s climate. According to the United Nations, carbon dioxide emissions amounted to about 30 billion metric tons in 2007. Straight into the atmosphere. No known way to take it back out again. And it’s going to remain there for thousands of years.
How about mercury? According to the Department of Energy, coal-fired power plants are responsible for putting about 48 tons of the neurotoxic metal into the atmosphere each year worldwide, about one-third of total natural and anthropogenic emissions.
Schauer also raises the environmental damage done by uranium mining. Again, one can’t argue that such damage is insignificant. However, what about the environmental damage associated with fossil-fuel extraction? The Deepwater Horizon oil spill in the Gulf of Mexico last year released 185 million gal of oil, the total impact of which we will probably never know.
Coal? I’m surprised the coal industry hasn’t come up with a suitable euphemism for “mountaintop removal,” the now-preferred method of extracting coal in West Virginia and Kentucky. You blast off the top of a mountain, deposit the debris in streambeds, excavate the coal, and spray some grass seed on the devastation that remains.
Natural gas is the fossil fuel du jour. It’s always described as “clean-burning natural gas” by the industry. And indeed, it does burn cleaner than coal. The reason natural gas has suddenly become so plentiful, however, is the advent of hydraulic fracturing technology for extracting it from beds of shale. There’s quite a bit of controversy about the impact of “fracking” on groundwater.
Nuclear reactors are expensive. People’s fear of radioactivity should not be dismissed. We should be focused on alternative sources of energy. Carbon taxes should be enacted.
All valid points. I’ve said it before: Humanity must learn how to live off the sun in real time. Humans, however, are not going to give up the benefits of modern civilization, which is based on abundant energy supplies. For the next 50 years or so, alternative energy sources cannot fuel civilization. Nuclear power can make a contribution that doesn’t contribute to climate disruption. That’s the reality we face.
Thanks for reading.
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Maglev (Electrodynamic Suspension (EDS)):
http://science.howstuffworks.com/maglev-train.htm
http://en.wikipedia.org/wiki/Maglev_train
http://www.calmaglev.org/default.php
http://www.hovertech.com/home/research/hoverboards.html
http://phys.kent.edu/pages/cep.htm
Superconductivity
Meissner effect:
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Fe(OH)3 2 FeO(OH) .
Also, FeCl3 (s) What is a "Galvanized Nail?" |
A zinc coated surface--zinc metal will oxidize to ZnO--a rather transparent coating. The term "sacrificial anion" is sometimes used to describe the use of this thin coating.
| Electrolysis of Water
The bubbles are easily seen. Twice as much hydrogen gas is produced as oxygen gas.
The net reaction: 2H2O --> 2H2 + O2 |
Fuel Cell Clip: fc_video_1.avi
Fe2+(aq) +
2 e- 
Here is a very
simple way to demonstrate that water contains hydrogen and oxygen. In order
to show electrolysis, you'll need a 9 volt battery, some bits of
wire, tape, a small saucer, some salt, and two
small pencils sharpened at each end.
Here's the setup. That's all there is!
