materials chemistry

A Bottle a Day keeps the Aging Away

Following on from the tea party where polyphenols reared their (ugly) heads a “highlight” has appeared in Angewandte Chemie English edition1, 2 pointing out the benefits of red wine, i.e. resveratrol. This is a well-known molecule, which has been at the centre of some controversy of late. Resveratrol is chemically trans3,5,4’-trihydroxystilbene:

This compound can be found in many types of fruits and nuts berries AND grapes. Its concentration in red wines varies between 0.1 and 14 mg/L whereby the 3-glycosate achieves levels of 30 mg/L. Frequently associated with this compound is the “French Paradox”, not that the French are a paradox themselves, but that apparently, in spite of consuming large amounts of saturated fats and barrels of red wine, the incidence of heart disease is lower that one might well expect it to be3. Resveratrol has a plethora of biological activities associated with it:

  1. It was originally noticed for its inhibitory effects against the oxidation of lipoproteins, the low-density variety being present at the onset of atherosclerosis4.
  2. Lowering lipid levels5.
  3. Moderate anti-oxidant properties.
  4. Protective for cancer, inhibiting cellular events associated with tumour initiation, promotion and progression6.
  5. It apparently also has a positive effect in diabetes and Alzheimer’s disease.
  6. It is able to activate sirtuin, thus mimicking calorie restriction and hence slowing the aging process.
  7. It also prevents phosphodiesterases from degrading cyclic AMP, also a mechanism of calorie restriction and hence age slowing.

What a list, I wonder what remains to be discovered?

Derek Lowe, at In the Pipeline  has commented extensively on this molecule and I recommend you all to have a read at the following plus the comments from his learned readership;

  1. The Latest Sirtuin Controversy
  2. Resveratrol in Humans: Results of a Controlled Trial
  3. The Sirtuin saga
  4. A resveratrol Research Scandal. Oh, joy
  5. Defending Das’ Resveratrol Research. Oh, Come On.
  6. Would I take resveratrol? Would You?

More about the sirtuins can be found on this page. In detail sirtuin1 information can be found here.

I do not profess to be conversant with all the details surrounding the apparent controversy concerning this compound and its biology. However, there is also big money at stake. GlaxoSmithKline acquired Sirtis, a company founded to discover and develop small molecules with at least some of the seven biological properties listed above. So presumably they are carrying out extensive medicinal chemistry on resveratrol. This won’t be an easy task to pick out one given the multitude of activities associated with this system, perhaps they can bundle 5,6 & 7 together. That is, of course, if there is any money left after paying the rather large fine recently dished out by the US Government. But, there is always the chance of off label indications being discovered!

Well, I shall certainly extend my red wine cellar but there won’t be many bottles in it, as I must take my daily dose of resveratrol by the bottle, especially at my age. Not to mention imbibing in tons of vitamin c and gallons of green tea. So when I drop dead after taking that lot no doubt I shall be considered as “toxic waste” and be treated accordingly.

References:

  1. Quideau, S., Angew Chem Int Ed Engl. 2012, 51(28), 6824-6826.
  2. Quideau, S., Angew Chem Int Ed Engl. 2011, 50(3), 586-621.
  3. S. Renaud, M. de Lorgeril, Lancet 1992, 339, 1523 – 1526.
  4. E. Frankel, A. Waterhouse, J. Kinsella, Lancet 1993, 341, 1103 – 1104.
  5. H. Arichi, Y. Kimura, H. Okuda, K. Baba, M. Kozawa, S. Arichi, Chem. Pharm. Bull. 1982, 30, 1766 – 1770
  6. M. Jang, L. Cai, G. O. Udeani, K. V. Slowing, C. F. Thomas, C. W. W. Becheer, H. H. S. Fong, N. R. Farnsworth, A. D. King- horn, R. G. Mehta, R. C. Moon, J. M. Pezzuto, Science 1997, 275, 218 – 220

Glucose Fuel Cell for Medical Implants

Professor Rahul Sarpeshkar and colleagues at MIT have created an implantable fuel cell which relies on glucose as its fuel. The device could potentially be used as a power source for the computers needed to decode brain signals and manipulate prosthetic or perhaps paralyzed limbs. The article was published in PLos ONE.

There are many layers of cool in this story. Implantable glucose fuel cells have been invented before – back in the 70s – but contained enzyme-based anodes which degraded over time and needed to be replaced. Because of this, implants like pacemakers rely on lithium ion batteries – which also drain over time, but have a much longer lifespan. This design utilizes a platinum anode to oxidize glucose ultimately to gluconic acid, liberating 2 electrons. The cathode is a matrix of single-walled carbon nanotubes which reduce dissolved oxygen to water.

What strikes me as the coolest part of this story, the fuel cell is fabricated on a silicon chip and would be placed in the cerebralspinal fluid next to the brain. Platinum is already known for being fairly biocompatable, but placing the chip in the cerebrospinal fluid is beneficial as there are very few white blood cells in the CSF to trigger an immune response and potential rejection. The CSF contains roughly the same concentration of glucose as plasma, and is not predicted to consume enough glucose fuel so as to impair brain function.

via DOI:10.1371/journal.pone.0038436

To avoid short circuiting the fuel cell, the platinum anode is enclosed in a ring of the carbon nanotube cathode. The cathode sequesters the dissolved oxygen for the reduction reaction, creating a concentration gradient across the cathode such that dissolved oxygen does not penetrate past the cathode. The nanotubes do not oxidize glucose, but are permeable to glucose, so the glucose passes through the cathode unreacted. The cathode is separated from the anode by a strip of nafion, a biocompatable perfluorniated polymer similar to teflon, but with branched sulfonate groups throughout. The sulfonate groups allow protons to flow through the nafion from the anode to the cathode, and nafion is permeable to glucose as well. The anode is at the center and can be as large as 2.5cm x 2.5cm.

The oxidation reaction at the anode is considerably less efficient than other implantable glucose fuel cells, but the biocompatability and long lifespan of the fuel cell makes this a really nice step forward in the treatment of paralysis and spinal cord injuries.

Sandwiches, Gluttons and Picky Eaters

This post is contributed by John Spevacek, an industrial polymer chemist and the author of the blog “It’s the Rheo Thing

Quintus guest-blogged recently on that iconic sandwich molecule, ferrocene, an iron atom sandwiched between two cyclopentadiene rings. Ferrocene is the first discovered and best known of a broader class of molecules called metallocenes, molecules in which a metal atom is sandwiched between two aromatic ligands (not necessarily cyclopentadienes). The applications of ferrocene at present are rather limited, but that is not the case with metallocenes. I thought I would expand on this subject by showing the particular usefulness of these molecules – the metallocenes – to polymer chemistry. Most people, including chemists, have little idea how important these molecules are to their everyday life. The molecules themselves are not polymerized, but instead are catalysts for the polymerization of olefins such as ethylene and propylene.

 Before we can get into the reaction details, I first need to explain for the stereochemistry of polymers and why it is import. In a isotactic polymer, all the monomers have been added to the chain in the same orientation:

while in an atactic polymer, the orientation is random:

This stereochemistry is critical to the mechanical properties of a polymer. Atactic propylene is easy to make, but is a pile of goo that you can use as a pretty bad adhesive and not much else. The isotactic version however, can crystallize and that then builds the strength of the material. Crystalline polypropylene is a good strong material that we use every day in food packaging, dishwasher safe food containers, carpeting, nonwoven fabrics, ropes and hundreds of other uses.

Read more ›

Yoe the Scientist’s Nano-Sized Brain

Deep in the heart of south-central Wisconsin, there lives a scientist who would prefer to remain nameless and (nearly) faceless.  We will call him Yoe.

Yoe the Scientist
 

Yoe is a graduate student at the University of Wisconsin, Madison. He is interested in transforming the nature of matter. Yoe is also interested in things that are very small. He combines these interests by researching nanowires made of the element silicon. Before we dive any deeper, let’s talk about what the heck “nano” means. “Nano” usually refers to things that have one dimension (height, width, etc) of 1-100 nanometers. This is around 100 to 100,000 times smaller than the width of a human hair. SMALL! A nanowire is simply a wire whose diameter is around 100 nanometers or less.  A human hair could be called a “microwire,” since its average diameter is around 100 micrometers.

Scanning electron micrograph of a human hair. Via The University of Wales Bioimaging Laboratory.
 

Yoe makes his silicon nanowires by a method that seems truly crazy to me. Not crazy in the “extremely dangerous” sense of the word (though his method is not without danger), but crazy in the “extremely awesome” sense of the word. First, he takes a chemical called silicon oxide and puts it in a long ceramic tube. He then heats the tube up to 1200 degrees Celsius (2,200 degrees Fahrenheit!) and flows a steady stream of hydrogen gas (4% in argon) through the tube. The machine he uses is called a tube furnace (clever huh?), and looks like this:

A red hote tube furnace. Image via Yoe the Scientist.
 

The box in the center is what creates the heat. The tube goes right through its center and is glowing red hot due to blackbody radiation. This is a cool-looking experiment!!!

Holy Crapola!!! Image via Yoe the Scientist
 

It’s not completely clear what happens next, but here is a guess. These insanely hot conditions cause some of the solid silicon oxide molecules to jump from the bottom of the tube, into the hydrogen gas stream. During their journey down the tube the silicon oxide and hydrogen can react with one another and be transformed into the pure element silicon. Towards the edge of the furnace the temperature in the tube drops, and this causes the newly formed silicon to fall onto tiny stainless steel disks that Yoe placed there.  In his first experiment he put a bunch of disks in the tube, because the disks towards the outer edge of the tube would be cooler and the disks towards the inside of the tube would be hotter. Yoe wanted to find the “sweet spot” where the temperature was just right to allow his nanowires to form.

Nanowire experimental setup. Image adapted from one created by Yoe the Scientist
 

After Yoe stopped the reaction and the disks cooled down, they looked totally flat and boring aside from being slightly different colors than before. Just by looking at them, Yoe had no idea whether he had made his nanowires. So, Yoe looked at the disks with a super-powered microscope called a scanning electron microscope. These microscopes are WAY more powerful than normal visible-light microscopes, and they look like this on the inside.

Super high tech!!!!
 

Not all of the steel disks had nanowires on them, but one of them had millions and millions of them! They were everywhere!! Yoe was super-psyched!!! The nanowires looked like this at 1,500 times magnification (click to look at high-res version, seriously! Click!!!):

One of the steel disks that was hotter than the one shown above looked like total insanity!!! There were nano-sized wires, ribbons, spheres, and (if you look closely) corkscrews!! CLICK THIS IMAGE!!!

Yoe zoomed in on another portion of this disk and even found a nanoBRAIN! This nanobrain is 300,000 times smaller than your brain!! Check it out!!!

Yoe thinks the nanobrain started out as a nanodroplet of liquid silicon. He thinks that as the silicon cooled down, the outside surface solidified first. Then as the inside of the nanodroplet cooled and shrunk further, the solid silicon shell crinkled up–kind of like how the surface of a grape shrivels up when it is dried out to become a raisin. This is also similar to how your fingers prune up when they’re in water, though the mechanism for that is a bit different.

Here’s what is kind of surprising. Yoe thinks the nanobrain and the insane jumble of wires and ribbons are really cool, but he is more interested in doing experiments using the nanowires shown in the first image. You may ask, “Is Yoe some sort of dummy? Why isn’t he more interested in the awesomer-looking image and the nanoBRAIN??!?” Yoe is no dummy. He is making these nanowires to study how they will work in the batteries of the future, and he prefers the nanowires in the first image for two main reasons.

#1) There are a lot of them. Their abundance, in addition to their tiny size, will make for a more powerful battery. #2) They are all pretty much the same size and shape, which makes them easier to study. If he saw something awesome happen using the insanity in the second image, it would be difficult to determine whether it was caused by the nano-sized wires, ribbons, spheres, or corkscrews. Scientists love cool-looking stuff, but they also want to know answers–and these interests don’t always overlap.

The moral of the story is, Yoe the scientist had successfully made his nanowires! Here he is, celebrating his success at science!!

This post originally appeared on the blog Science Minus Details.

By April 23, 2012 11 comments fun, lab technique, materials chemistry