Field of Science

Blue Color Workers

The title of this post was inspired by a student blooper in a sociology paper where the writer surely did not mean to say "blue color workers". Spell checkers have their limits. In the right context, however, blue color workers is not a candidate for Richard Lederer's next collection.

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.

Elemental Tales: Reduced Iron

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 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.

Relishing Osmosis

Tomorrow is a day for iconic cooking. Turkey. Stuffing. And of course, cranberry sauce. At a dinner a few years ago, a friend produced an odd silver implement and asked the gathered group of foodies just what we all thought it might be. Would you believe a jellied cranberry server - just the right size, she pointed out, to cut the canned jelly! Turns out that serving pieces for jellied sauces, like tomatoes and cranberries pre-date the Ocean Spray cans, but it was a fun puzzle regardless.

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.

Weird Words of Science: stochastic

I'm teaching a graduate course in mathematical modeling of natural processes. Many math modeling techniques rely on the random numbers and are more generally known as stochastic algorithms. A simple example is numerical integration. We used numerical integration techniques to the value of pi by (virtually) throwing darts at a circular target embedded in square (figure). The ratio of hits inside the circle to the total hits is pi/4. Stochastic comes from the Greek stochastikos "to take a guess", which itself derives from stochos - "target", so the target image above is apt.

Weird Words of Science: MythBusters at the Beach

We're on vacation this week, "down the shore" as they say in these parts. My cable deprived kids are enjoying evenings watching MythBusters and Nick. The episode du jour is Grenades and Guts, in which the myth that drinking a liter of Diet coke and eating a pack of Mentos will make your stomach explode is busted. In the process, the team wondered if the muriatic acid in the stomach was somehow blocking the usual spectacular reaction.

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.

Tin tears

Tin cries. Not tears, but when tin is bent it elicits a peculiar sound called by metallurgists a "tin cry". Indium also lets out a scream when deformed, as Michael Cassidy pointed out in an earlier comment.

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 linings

Yesterday I had a round of minor surgery. When all was said and done, the surgical site was cauterized with what a nineteenth century physician would have called "lunar caustic" -- silver nitrate to a modern chemist or physician. I have to admit my first geeky thought was, "how does that work?"

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".

Perils of Summer 2: Mephitis Squared

It's war on my dad's farm: humans versus Mephitis mephitis, night time maneuvers complete with chemical weapons. Currently the skunks hold the high ground.

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...

Urrrrrr - it itches!

The spring was cold and so the itch to get outdoors once the warm weather arrived was hard to resist. As moms will tell you, scratching just makes the itching worse, and scratching even metaphorical itches can raise welts. Ask anyone who has heeded the siren call of summer and ended up with hives, or worse yet, encountered a patch of poison ivy.

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.

Indolent Molecules

I heard a colleague talk today at the MidAtlantic Regional Meeting of the ACS about his work with fluoroquinones. These molecules (which despite their name contain no fluorine) fluoresce, that is they "glow" when exposed to light. The process can be short circuited by binding another molecule, a quencher, to fluoroquinone. The research discussed the quenching behavior of tryptophan. Tryptophan is an amino acid, one of the building blocks of proteins. Structurally, it's an indole; an aromatic six-membered ring fused to a five-membered ring containing a nitrogen forms the core.
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.

Agonists and Allergies

My mast cells are leaking histamine and I am miserable. Histamine is a small molecule that binds to receptors in a wide variety of tissues including, alas, the respiratory system. It happens to increase vascular permeability - in other words, it's causing fluids to leak through my capillilary walls and into my nose. Sigh.

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.

The Carbon Footprint of that Computer

Someone asked me over lunch yesterday if I was worried about global warming. "Worried enough to ride my bike to work through the hills of Bryn Mawr!" was my response. The conversation eventually turned to how much energy computers used - should you turn them off to save energy (and thereby reduce the amount of CO2 being dumped into the atmosphere)? Their IT support had said to leave the machines on, on the grounds that the amount of energy used to restart them outweighs any savings from turning them off at night. I thought this was not true, and some back of the envelope calculations suggest shutting down from the night (even putting the machine to sleep is not sufficient) is 10 times more energy efficient than leaving it on.

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 and Cranky Suburbanites

I went to work today sporting a pair of molecular earrings: serotonin and norepinephrine to be precise. Two non-chemist colleagues spotted them and wondered about the significance of the molecules (and where to get them!). "Serotonin for serenity, norepinephrine for energy." "Ah, you're in balance then!" When I walked past ten minutes later they were browsing the molecular earring site and trying to figure out how to pronounce "acetyl" (as in acetylcholine). The site says that acetylcholine can promote creativity, learning, dreaming and memory. In passing, I noted that many pesticides are acetylcholinesterase inhibitors, they block the breakdown of acetycholine, which can have nasty effects on the body. Which led one colleague to wonder if that was why "suburban cul-de-sacs were such cranky places!"

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...

Weird Words of Science 12: A need for speed

The nectar busily gathered by the bees outside my window has a high sucrose content. The bees add the enzyme invertase to the nectar to catalyze the inversion of the sucrose to glucose and fructose that are the major sugars in honey. Humans can speed up the same reaction by heating the syrup or by adding a touch of acid.

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?

Turning Sugar Inside Out

This week's worksheet in general chemistry asks my students to analyze the chemical kinetics (the speed) of this reaction:

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.

Dandelion Wine

At a party Saturday night someone mentioned a rumor about extracting illegal drugs from dandelions. This was news to me, I hadn't thought that dandelions had all that much to offer pharmacologically. Google didn't produce any hits, nor did my students know anything (though they did tell me that on MythBusters they'd made nitrous oxide from ingredients you could obtain at home). There is some evidence from rat models that dandelion extracts can interfere with antibiotic absorption (particulary those in the same class as ciprofloxacin), and it has potential for control of blood sugar, but I can't find anything in PubMed more interesting than that.

How did the leopard get it spots?

Biomorphogenesis, the process by which biological forms arise during development, is a fascinating area that crosses many fields, including computer science, mathematics, biology and chemistry. How do the stripes develop on a zebra? Alan Turing, one of the first computer scientists and the man who developed the computational engine that cracked the Enigma code in World War II, took on this problem in the early 1950s. In 1952 he published, "The Chemical Basis of Morphogenesis" [Phil. Trans. R. Soc. London B 1952, 237, 37-72]. He posits in this paper that oscillating chemical reactions, such as the Belousov-Zhabotinsky reaction, could lead to temporal-spatial differences in pigmentation. You can see why this might be the case in this animation of the reaction.

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.

pH Potpouri

The term pH has been in use for nearly a century. It is a logarithmic measure of the hydrogen ion concentration ([H+]): pH = -log10[H+]. (Technically, there aren't bare protons (H+) floating around in solutions, but that's another post!) The original symbol was pH. and introduced by Sörensen in 1909. Theories vary as to the origin of the p - all agree it means power but whether in Latin, French or German, seems in dispute. I would hazard it was either German or Latin as the original paper was published in German (Biochem. Zeitschr.). If I were not on the road, I'd look it up.

The modern form pH was introduced in 1920, "as a matter of typographical convenience".