Field of Science
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Science books for 14-year-olds1 day ago in The Curious Wavefunction
Metereca4 days ago in Variety of Life
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Why I'm Marching for Science4 weeks ago in Angry by Choice
Will democracy survive climate change? - A lesson from the past2 months ago in History of Geology
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Bryophytes Outdoors11 months ago in Moss Plants and More
If You Are Against Nuclear Power1 year ago in The Astronomist
FieldNotes: water on Mars, less in California.1 year ago in Field Notes
A New Wave of Science Blogging?2 years ago in Labs
Update: Tree of Eukaryotes (parasitology edition)2 years ago in Skeptic Wonder
post doc job opportunity on ribosome biochemistry!2 years ago in Protein Evolution and Other Musings
Growing the kidney: re-blogged from Science Bitez2 years ago in The View from a Microbiologist
Blogging Microbes- Communicating Microbiology to Netizens2 years ago in Memoirs of a Defective Brain
Out of Office3 years ago in inkfish
The Molecular Circus4 years ago in A is for Aspirin
The Lure of the Obscure? Guest Post by Frank Stahl4 years ago in Sex, Genes & Evolution
Girlybits 101, now with fewer scary parts!5 years ago in C6-H12-O6
Lab Rat Moving House5 years ago in Life of a Lab Rat
Goodbye FoS, thanks for all the laughs5 years ago in Disease Prone
JAPAN'S RADIOACTIVE OCEAN | DEEP BLUE HOME6 years ago in The Greenhouse
Slideshow of NASA's Stardust-NExT Mission Comet Tempel 1 Flyby6 years ago in The Large Picture Blog
in The Biology Files
Exposure to silver can cause argyria, in which the skin turns a grey-blue color as a result of deposits in the dermis of metallic silver and silver compounds. Unlike the orange coloration that eating too many carrots can cause, the dark grey cast of argyria is permanent. The condition can be striking if the entire body is affected. Barnum & Bailey's Blue Man was found at autopsy to have argyria, perhaps from exposure while working as a silver miner: a real blue color worker.
Argyria in this century is more likely a result of exposure to quantities of silver in non-industrial settings. Silver preparations were used pharmaceutically in the early 20th century, and much of the literature about silver and skin discoloration dates to that time. There are reports of cases of argyria arising from use of colloidal silver compounds. Externally applied, salts of silver are effective antiseptics, hence the marketing of these silver solutions as nutritional supplements "to support the immune systems" and as "all-natural antibiotics". There is no evidence that these compounds are effective in these ways when taken internally - and the risk of being permanently blue is not one to be taken lightly! The FDA has ruled that products containing silver or colloidal silver are "not safe and effective" and may not be sold as having any medicinal benefits. Despite this, colloidal silver is readily available.
The photo is of Rosemary Jacobs, who suffers from argyria, and is used with her permission. In 2006, Stan Jones, ran as the Libertarian candidate for U.S. Senate in Montana. He took a colloidal silver compound in 1999 and now has argyria as a result.
In the 1970's I was a TV news junky. Dinner was typically late - my dad commuted an hour plus from LA in those days - and my mother would kick me and my homework off the table a bit before 6. I'd duck into the den to get the update on the war (Vietnam, not Iraq!) that my friends' older brothers were fighting. Even then, I was clearly not the advertisers' target demographic. The ads ran the gamut from DentuGrip to Phillip's Milk of Magnesia. And of course, Geritol - exhausted wives re-energized by curing their "iron poor blood" with Geritol, much to their husbands' delight ("My wife. I think I'll keep her!")
More than one in ten adult women (12-49) in the US do suffer from "iron poor blood" or more technically iron deficiency anemia, and world-wide it is the most common nutritional deficiency. (By some estimates two-thirds of pregnant women in developing countries are anemic, primarily due to lack of iron in their diets.)
The body does an impressive job of holding onto the iron it needs not only for synthesizing the oxygen carrying protein hemoglobin, but for enzymes used in other key processes. Total body stores of iron run from about 2 to 4 grams, about two-thirds circulating around in hemoglobin, and twenty percent held in reserve in the bone marrow. The daily loss ranges from 1 milligram to about 1.5 mg in women of child-bearing age. Which begs the question, why is the FDA's recommended dietary allowance of iron 20 mg?
The answer has much to do with the ability of the body to extract iron from various sources. The best form of iron, in terms of its bioavailability, is heme-iron, or iron bound to the plate-like heme structure found in hemoglobin. Non-heme iron, found in plants like the iconic iron source spinach, is tougher for the body to extract and use - estimates are only 10 to 15% of the iron can be absorbed. So to get that 1 mg a day, you need to consume about 10 mg a day. If spinach is not your cup of tea, try dark chocolate; there's 2.3 mg of iron in a 100 gram bar, about the same as in the identically sized serving of spinach.
Lots of Americans get their iron from fortified cereals. Read your box of Total. You'll find that a cup gives you 18 mg of iron. Check the ingredients and you'll notice that it's added in the form of reduced iron. Reduced iron is not iron on a diet, but iron is the pure metallic form. That's right, there's tiny iron filings in your cereal. If you're feeling experimental, toss a couple of cups with milk into the blender, then run a magnet through it. You'll pick up the filings on the magnet. The acid in your stomach turns the metal into an ionic form (Fe2+).
Better yet, cook in cast iron. Scramble your eggs in a cast iron frying pan and you can triple the iron content (from 1.5 mg to almost 5 mg). Cook something acidic, like spaghetti sauce and you can up the iron content by a factor of ten.
Husbands of tired wives might thus consider a nice box of dark chocolate covered apricots rather than replacing the window shades with ads for Geritol...it might cure more ills than just iron deficiency. I would not advise a cast iron frying pan with a bow!
Dried apricots have twice the iron content of spinach and are much tastier when drenched in chocolate.
The heme figure is taken from here.
For me, the whole question of canned or homemade sauce is moot, since I prefer cranberry relish. I make it by running a bag of cranberries and a whole orange through the food processor, then adding sugar to taste. Since it's best made ahead, so the flavors can blend, I made a batch yesterday afternoon when I went home for lunch between office hours. Straight from the food processor the relish is whitish, dry and pretty bitter. Stir in the sugar and not only does it become sweet, but a ruby syrup begins to appear.
This is a (literally) beautiful example of osmosis in action. The high concentration of sugar outside the cell walls of the finely chopped orange and cranberry mixture encourages the water within the cells to pass through the cell membrane to bring the concentrations inside and out into equilibrium. The sugar and cellular contents are too big to cross the membrane, so the best the poor cells can do is to dump their water out creating that lovely syrup. The process intensifies the flavors of the berry and orange bits as well, since they are essentially "dried".
After a day of cooking and now kitchen scrubbing, my fingers are wrinkled. [This is an osmotic process as well, in this case, the water is crossing the cell membranes into my cells, causing the out layer of skin to get larger, and wrinkle.] Or perhaps, not! As David Bradley points out in the comments to this post, the wrinkling of the skin on your fingers after prolonged immersion in water is not particularly well understood. My reading of the literature suggests that osmosis plays at most a small role.
Muriatic acid is better known to chemists as hydrochloric acid. It gets its name from the Latin for brine - muria. It was also sometimes called marine acid, again calling to mind its briny origins (though the eytmology of marine is different than that of muriatic, the former comes from the Latin for sea, mare).
The first synthesis of hydrochloric acid is attributed to Jabir ibn Hayyan around 800 CE. Mixing oil of vitriol (sulfuric acid) and common salt (sodium chloride), produces hydrochloric acid: HCl.
You are hearing the sound made by a phase transition, a change in the structure of the metal at the atomic level. Indium in its crystalline form is tetragonal, when bent, the mechanical stress induces "twinning" in which sections of the crystal become mirror images of adjacent planes. Twinning plays a role in mechanical failure of metals subject to stress, the research literature goes back roughly a century.
Listen to a recording of indium "screaming" made by Theodore Gray at the WGBH studios. It's an unnerving sound, more like a crackling than a scream.
The photo is courtesy of David Hammon in the physics department at the University of Vermont.
Silver nitrate has been used for a long time as a cauterizing agent. In 1826 John Higginbottom, a British physician wrote An essay on the application of the lunar caustic in the cure of certain wounds and ulcers. My physician used a solution of AgNO3, Higginbottom almost certainly used a solid mixture of silver nitrate and silver chloride, but other than that the basic treatment protocol hasn't changed in almost 200 years. Higginbottom notes that the application "smarts" and I would guess that it must have. I felt it, even with a good local anesthetic. The good 19th physician also prescribed adjuvant therapy ("I took away ten ounces of blood and administered purgative medicine") which my physician sensibly eschews!
So why is the stuff called lunar caustic? The caustic part is obvious, silver nitrate is an effective oxidizing agent for organic molecules, including biomolecules. Alchemists associated silver with the moon, its Latin name, argentum derives from "white, shining".
Last night my brother's dog threatened a skunk, with predictable results. The collateral damage included my shoes and feet. The Reverend's Wife produced a bottle of something guaranteed to elminate the smell and we decontaminated me and the dog on the lawn. I was more cooperative about being hosed down. The odor was overpowering, and even after twice deskunking me, my kids swore I still smelled of skunk.
Skunk musk is a mixture of low molecular weight thiols, sulfur containing compounds that have the basic structure ☐-S-H (where the box represents a functional group, such as methyl or butyl), and related compounds called thioacetates. Most thiols have a characteristic, and awful, odor. (Thioacetates don't smell quite so badly.) The simplest thiol is methane thiol, also known as methyl mercaptan, which is used to spike methane (natural gas) so that leaks can be detected. (Methane is actually odorless.) Humans can detect thiols at very low concentrations, less than 1 ppm, which explains why my kids could still pick up the odor.
Skunk odor can be neutralized by converting the thiols to less odiferous molecules. One way this can be accomplished is by reacting the thiols with hydrogen peroxide, which oxidizes the thiol to a sulfonic acid ( ☐-SO3H), which has virtually no odor. Bleach (a strong oxidizing agent) will work as well. A similar technology is used to remove thiols from industrial waste water, where the thiols are converted to disulfides ( ☐-S-S- ☐), which are oils that separate easily from the water.
Mercaptan comes from the Latin mercurium captans, something that seizes or captures mercury. Sulfur reacts very effectively with mercury, and one way to clean up a mercury spill is to sprinkle sulfur on the mercury. Thiol is Greek for sulfur.
If you need a recipe to remove skunk odor, try Humbolt's list. I can personally vouch for the effectiveness of the pet/human version. Note that tomato juice is not particularly effective.
1-para-methen-8-thiol is an uncharacteristically and pleasantly scented thiol more commonly known as grapefruit mercaptan.
More demystified chemical perils of summer...
My niece and I took a tour last week of the Mutter Museum in Philadelphia which has a great collection of wax models of dermatological pathology, used for teaching students in the days before slides and PowerPoint, including hives or urticaria. The name comes from the Latin for nettle, and the resulting skin wheals certainly bear some resemblance to nettle stings (as my youngest can attest after a close encounter with that plant). Histamine leaking from mast cells in the skin is responsible for hives' principal misery - itching.
True misery is reserved for those who have contacted Toxicodendron radicans - poison ivy - or a relative. These plants produce urushiol, which binds tightly to proteins in the skin. Molecules like this are called haptens, which comes from the Greek "to fasten". Antibodies don't recognize the small molecule until it fastens onto its target. Then the body reacts, in this case triggering the characteristic linear rash, and keeps reacting until the invader detaches from its binding site.
Despite the similarity in names between urticaria and urushiol, they come from different roots. Urushiol was first isolated from the Japanese lacquer tree - the urushi - by a Japanese chemist, Miyama.
Other haptens can react with the same sites as urushiol, including substances found in mango skin and fresh cashew nuts, with similar unfortunate consequences.
Urushiol isn't just a weekend gardener's nuisance, but can cause serious problems for fire fighters in working brush fires in areas such as the California hills, where poison sumac, another urushiol producing plant, thrives. The chemistry gives some clues to helping prevent and treat urushiol reactions. Application of an organic derivative of an absorbent mineral (bentonite) can soak up and trap any oil before it reaches the skin and binds- this is the principal behind the commercial product Ivy Block. Alternatively, something that binds strongly to the urushiol target but is not itself a hapten could act as a preventative. D-Limonene, found in citrus skins, has been floated as a possibility, but I couldn't find any evidence that it works!
Once the stuff has bound, you just have to wait it out. It takes a couple of weeks for the bulk of the urushiol-protein complexes to break down. In the meantime, steroids can reduce the inflammatory reaction and histamine blockers, H1 (like Benadryl) or H2 (Tagamet or Zantac) can provide some relief from the itch.
Tryptophan is thought to induce sleep - and is often blamed for post-Thanksgiving meal naps. Melatonin, which also play a role in sleep regulation, is also an indole.
The indoles of chemistry get their name from the Latin for indigo, the dye from which the basic indole structure was first isolated. The indolence which some indoles induce has a different etymological root, dolorens - grief or pain.
I'm fighting back by taking a histamine antagonist, diphenhydramine to be precise. Antagonists bind to a receptor and block its response, in this case inhibiting the H1 histamine receptors in the respiratory tract (H2 receptors cluster in the gastrointestinal tract - and so H2 antagonist, like Zantac, are used to treat heartburn). Agonists are molecules that bind to a receptor and cause a response. Why would you want to take something that binds to a histamine receptor and provoke a response? Turns out there are a couple of drugs that are histamine agonists, including one for Meniere's disease and another that may have theraputic potential for diabetes.
What does the term amine have to do with camel dung? Read about it here.
Powering up my machine takes 3 minutes at full tilt. At 120 watts, this uses up about 22 kJ of energy. If I left it in sleep mode all night (at 3.5 watts), it uses 228 kJ. I save about 200 kJ of energy, if I shut it off for the night, rather than just put it to sleep. It comes to about 44 pounds of carbon dioxide a year. It's a drop in the bucket compared to the per capita amount of carbon dioxide produced in the US (19.8 metric tons in 2003) - about 0.1%.
If you want to check your own carbon footprint, the EPA has a calculator.
Acetylcholine is a neurotransmitter, a small molecule that plays a role in transmitting signals along neurons. Originally found to stimulate the vagus nerve (responsible for controlling heart rate, among other things), it was christened vagustoff by Otto Loewi who eventually won the Nobel prize for its discovery. Curare blocks the receptor sites for acetylcholine, thus preventing muscle contraction (and causing respiratory arrest). You can have too much of a good thing, the venom of black widows causes synapses to be flooded with acetylcholine.
vagus is from the Latin for wandering, which is what that nerve does...
Both enzyme and catalysis are lofty words lifted by scientists in the 19th century to serve more prosaic ends.
Enzyme's first meaning in the bread used for the Eucharist in the Greek Orthodox tradition. It means "leavened". It's not such a stretch to borrow the word to describe stuff that encouraged cellular reactions to proceed, what had been called the ferment.
Catalysis was originally used to describe the collapse of a nation, its origins can be traced to the mid 17th century. It comes from the Greek "to loosen". In the 19th century, Berzelius suborned the term to describe the process by which chemical reactions are facilitated. Catalysts participate in a reaction, but are in the end are restored to their original form, like molecular Phoenixes. Why did Berzelius settle on this term? Did he hope to imply that the constraints which bound the reaction to a slow pace are loosened by a catalyst?
C12H22O11 (sucrose or table sugar) + H2O (water) -> C6H12O6 (glucose) + C6H12O6 (fructose).
It's called the inversion of sucrose, and the resulting mix of glucose and fructose is tagged invert sugar. The name suggests that table sugar has been turned inside out or perhaps upside down, but in fact it's simply been split into two simpler sugars. The inversion is not of the sugar itself, but of the way it bends polarized light. If you pass a beam of polarized light through a solution of regular table sugar, the light will "rotate" or bend to the left. The mixture of glucose and fructose "inverts" the rotation, and bends the beam to the right.
Invert sugar is less like to crystalize than regular sugar, making it ideal for sweetening candy or jams. The reaction in the absence of a catalyst is slow at room temperature, but can be completed . The simplest way to catalyze the reaction is with an acid, often citric acid or ascorbic acid (Vitamin C), and many jam recipes call for one or the other.
So why do these compounds "bend" polarized light? Like many biological molecules, they are chiral or handed. The right handed or D form bends the polarized light toward the right, the left handed form (denoted L) left.
Another name for the D form of glucose is dextrose, named for the direction in which it bends polarized light.
The BZ reaction is complex, the proposed mechanism consists of almost 20 steps - much more complex than those we are discussing in general chemistry this week! You can watch the BZ reaction in this video clip - the color changes look like magic.
The modern form pH was introduced in 1920, "as a matter of typographical convenience".