Mixed Colours: an interview with Brian and Roger Eno

picture from play.google.com

Now that we're all stuck at home, this is a good time to explore some interesting podcasts.

Brian and Roger Eno worked together on Apollo: Atmospheres and Soundtracks, which was released in 1983 as a soundtrack for a movie that became the documentary about the first Apollo moon landing, For All Mankind.  They haven't released a new album together since.
 

Bob Boilen interviews them for NPR's All Songs Considered: Roger And Brian Eno Reveal How They Made Their Tranquil New Album Together 

Both albums are are Ambient Music, which Brian Eno has said "must be as ignorable as it is interesting."  I like to listen to Apollo: Atmospheres and Soundtracks when I am working and it is too quiet.  Ambient music makes for nice background sound that doesn't demand my attention the way most types of music do.

Advice from Astronauts

Some book suggestions from Odin

When I was young I wanted to be an astronaut - that didn't happen.  But I still like reading about all things to do with Space.

Here are three excellent books about the challenges of people going to space:

• Endurance by Scott Kelly who spent a year on the ISS
• An Astronauts Guide to Life on Earth by Chris Hadfield, another ISS astronaut
• Packing for Mars by Mary Roach about the difficulties we'll face in planning a trip to Mars

Scott Kelly also wrote an article for the NY Times on dealing with isolation: 

I Spent a Year in Space, and I Have Tips on Isolation to Share Take it from someone who couldn’t: Go outside.

The Weight | Featuring Robbie Robertson and Ringo Starr| Playing For Change | Song Around The World

 

Wordclouds of Chemistry Texts

After stumbling across a post on One R Tip A Day about building Wordclouds using R, I thought I would try it out myself.  I have been subjecting my undergrad chemistry students to R, so this seemed like a good opportunity to use R for a little fun.  I decided that it would be interesting to look at some old chemistry books.  I picked three works from Project Gutenberg:

• The Sceptical Chymist (1661) by Robert Boyle
• Elements of Chemistry (1789) by Antoine Lavoisier
• An Elementary Study of Chemistry (1905)
• by William McPherson and William Edwards Henderson

The Sceptical Chymist (1661) Robert Boyle

Elements of Chemistry (1789) Antoine Lavoisier

An Elementary Study of Chemistry (1905) McPherson and Henderson

It's no surprise that Boyle's wordcloud is so different from the other two.  The influence of Alchemy was still quite strong in 1661, and Boyle's vocabulary reflects this.  It is perhaps more interesting to see how similar Lavoisier is to McPherson and Henderson despite their being 116 years apart.

Robert Boyle and Antoine Lavoisier were both instrumental in developing modern Chemistry, William McPherson was a chemistry professor at Ohio State University and one of the chemistry buildings there is named for him.

I adapted Paolo's code from  Wordclouds using R. You will need the R packages tm, wordcloud and RColorBrewer. I downloaded the books as plain text from Project Gutenberg and saved them in a directory called chemtxt.


library(tm)
library(wordcloud)
library(RColorBrewer)

#reads all files in the directory chemtxt
chemtexts <- Corpus(DirSource("chemtxt/")) 


book <- Corpus(VectorSource(chemtexts[["boyle.txt"]])) 
book <- tm_map(book, removePunctuation) 
book <- tm_map(book, tolower) 
book <- tm_map(book, stripWhitespace) 
book <- tm_map(book, function(x) removeWords(x, stopwords("english"))) 


# format as a dataframe with words and their frequencies 
book.tdm <- TermDocumentMatrix(book) 
book.m <- as.matrix(book.tdm) 
book.v <- sort(rowSums(book.m),decreasing=TRUE) 
book.d <- data.frame(word = names(book.v),freq=book.v) 


#color scheme 
pal2 <- brewer.pal(8,"Dark2") 


# uncomment this line to save wordcloud as an image file #png("wordcloud_boyle.png", width=600,height=600) 


#I picked just the 60 most frequent words 
# to show ALL the words in the wordcloud use max.words=Inf wordcloud(book.d$word,book.d$freq, scale=c(8,.2),min.freq=3,max.words=60, random.order=FALSE, rot.per=.15, colors=pal2) 
dev.off()

What is public science, and why do you need it?

Image via Wikipedia

Did you use a browser to zoom around on the internet today? Have you ever been vaccinated? If you answered yes to either of those questions, your life has already been made better through publicly-funded science in America. Public science is basic scientific research funded by governments, and just in America alone it's led to breakthroughs in everything from medicine to clean energy. But now public science is under threat. Here's why — and why we can't afford to lose it.

The Science Fiction blog IO9.com has a nice overview on the value of basic research funded by the US government and some of the myths about science funding.  Don't rely on know-nothing blowhards who tell you the US should cut funding for science.  Check it out.

What is public science, and why do you need it?

Animated sheet music - So What

So What

via Kottke.org Animated sheet music

Nano "Motor" Powered by Chemistry

We have been hearing about nanotechnology in the media and in science fiction for a long time now.  I have always been a little skeptical  about how realistic an idea "nano-machines" are.  This new research has me rethinking that skepticism.

A communication published online in Angewandte Chemie describes what you could call a working nano-motor.  Ayusman Sen and his coworkers at Pennsylvania State University have prepared little spheres less than a micrometer across - one side of the sphere is gold and the other side is silica (SiO2).  On the silica side they have attached a Ruthenium compound known as a Grubbs Catalyst.  The Grubbs Catalyst reacts with alkenes which are the "fuel" for the motor.

Image via Angewandte Chemie

When they place their motor-particles in a solution containing norbornene, the catalyst group on the silica side of the particle polymerizes the norbornene, and the amount of unreacted norbornene molecules on the silica side of the particle decreases.  This causes a concentration gradient - the concentration of norbornene on the gold side is higher than the concentration of norbornene on the silica side.

It is this difference in concentration of "fuel" molecules that makes the particle move.  Osmosis involves solvent molecules moving from a region where concentration is low, to a region where concentration is high.  As a result, solvent molecules flow around the "nano-motor" from the silica side (less norbornene - because the Grubbs cayalyst polymerized it) to the gold side (lots of norbornene).  And this causes the particle to move in the opposite direction.

Professor Sen anticipates that eventually you could redesign his nano-motor to use a "fuel" like glucose and doctors could use it in the bloodstream to repair damaged tissue.  Just like something out of Fantastic Voyage.

Image via Wikipedia

Self-directed microspider could repair blood vessels - New Scientist

Original research article:  A Polymerization-Powered Motor  DOI: 10.1002/anie.201103565

What is a Bridgehead Carbon anyway?

It's the start of a new school year and I am going to try to post a little more regularly.  Since it has been a while since I posted on a regular basis, I thought it would be a good idea to re-introduce this blog.

What is a Bridgehead Carbon anyway?  I teach undergraduate chemistry and my main area of interest is Organic Chemistry.  I chose the name "Bridgehead Carbons" partly because I have always liked the look of bicyclic compounds like norbornane.  You can think of Norbornane as being a cyclohexane (in pink) with a CH2 unit (in black)that acts as a bridge connecting the top and the bottom of the pink ring.  The carbons that connect the "main ring" to the "bridge" are the Bridgehead Carbons.

Another reason for choosing this name is that Bridgehead Carbons serve to connect different rings within the same molecule, and I intend to write about a variety of topics that I none the less feel are connected to my experience with chemistry and teaching.

So, what is this blog all about?  Stuff that interests me as a chemistry teacher, especially organic and bio-organic chemistry, cheminformatics, things that might be helpful to college students in general, and anything else that strikes my fancy.

Science in the Library winner

Louise Peck posted this on the CHEMINF-L list serve

The Royal Society of Chemistry's RSC Publishing division recently ran an annual photograph competition with the theme 'Science in the Library'. 

The competition prize was that the winning photograph would be placed on the front cover of the 2012 RSC Publishing Catalogue and was voted for by over 115 RSC staff and the RSC Library Advisory Board.

image from RSCPublishing Blogs Home 

And the winner is Johns Hopkins University in Baltimore, MD,  home of the first PhD program in chemistry in the United States which was started by Ira Remsen if I recall correctly.

You can download a copy of the 2012 RSC Publishing Catalogue from their website.  All 17 libraries that were entered in the contest are shown on pages 2-5 of the catalogue.  See if you can guess which one I have visited.

End of the Year Writing Advice

It is the end of the school year and our seniors will be turning in their senior research papers soon.  I think that scientific writing in particular can be a big challenge, especially when writing about your own research.  When you work on a project for most of a year you become emotionally invested in it, and you loose sight of its complexity.  But in sharing your results with others, whether as a paper or an oral presentation, it is easy to assume that everyone knows what you know.  And when discussing complex ideas, you can try to say too much at a time.

The original list has seven rules, but I am only quoting the first three.  If you are a writer of any sort, go read the original post with all seven rules.

VS Naipaul’s Rules for Beginners 

1. Do not write long sentences. A sentence should not have more than ten or twelve words. 

2. Each sentence should make a clear statement. It should add to the statement that went before. A good paragraph is a series of clear, linked statements. 

3. Do not use big words. If your computer tells you that your average word is more than five letters long, there is something wrong. The use of small words compels you to think about what you are writing. Even difficult ideas can be broken down into small words.

The point is to use good judgement.  Use big words when they are necessary, not just to impress your reader.  Strive for short, direct and clear.  If the result is too simple, you can always revise.  But if your first draft is full of long, convoluted sentences it can be hard to make it concise.

Sometimes you don't really understand some of the details yourself.  Really good writing can help you to better understand the topic yourself.  It forces you to choose your words carefully and think about the meaning.  

VS Naipaul’s Advice To Writers - The India Uncut Blog - India Uncut via BoingBoing

Jmol test in Blogger

Here is a short test to see if I can display a Jmol applet in a blog post.  I don't currently have access to a server to host the jmol applet, so for this test I am linking to the applet, script and molecule files on the Jmol Samples page.

UI Controls example

Chiral Drugs on the Chemistry Blog

Yesterday we started Stereochemistry in my Organic Class, and on Monday Azmanam on the Chemistry Blog had a post on  Chiral Drugs.  Take a look at the structures below:

Both are used to treat gastroesophageal reflux desease (GERD, commonly known as acid reflux).  Can you see the difference in the structures?  Click the image to see a larger version.  Prilosec is sold as a racemic mixture: a 50-50 mix of the R and S enantiomers.  Nexium contains just one enantiomer - the S isomer.  This is an example of a chiral molecule whose stereogenic center is not a carbon, but rather a sulfur.  The fourth group attached to the sulfur - the one with the lowest priority - is a lone pair of electrons.  Read Azmanam 's post for a good discussion of the two.


Chemistry Blog - Nexium’s Dirty Little Secret

How Plants Use Caterpillar Spit for Protection

How do plants protect themselves from the bugs that chew on their leaves?  In the case of the wild tobacco Nicotiana attenuata, when tobacco hornworm (manduca sexta) caterpillars feed on the leaves a collection of molecules called Green Leaf Volatiles (GLV's) is released by the plant.  GLV's are released any time a leaf is damaged, but the interesting thing is that when the damage is done by chewing caterpillars, a different form of the GLV's are produced which attracts Big-Eyed Bugs (Geocoris spp) - a predator for the caterpillars.

Image via Wikipedia

Plants emit two main types of volatile molecules: terpenoids and Green Leaf Volatiles.  The terpenoids are emitted from the whole plant and usually after a delay - maybe as much as a day after the damage.  The green leaf volatiles are more specific - they are emitted from the damaged leaf itself and it looks like they are produced at the same time as the damage.

Green Leaf Volatiles are typically 6-carbon alcohols, aldehydes or esters.  In the case of Nicotiana Attenuata they seem to mostly consist of hexenal, hexenol and simple esters of hexenol.  The interesting bit is the alkene portion of these molecules.  Alkenes can have one of two basic geometries around the double bond: the Z (or cis) isomer is locked into a u-turn shape and the E (or trans) isomer is locked into a zigzag-like orientation.

Normally, Nicotiana attenuata produces mostly the Z isomer of these molecules and a relatively small amount of the E isomer.  However something unusual happens when the damage is caused by caterpillars chewing on the leaves:  in this case the plant produces roughly equal amounts of the Z isomer and the E isomer.  You and I would probably not notice a difference in the smell of the leaves, but apparently there are bugs that can.  When more E isomer is produced, more Big-Eyed Bugs are attracted to the plants.  And the big-eyed bug eats caterpillars and their eggs.  The E isomer GLV's are a plant distress call and the big-eyed bugs are the cavalry.

How exactly does the plant "decide" which GLV isomers to make?  After testing a variety of possible candidates, it looks as though there is an enzyme in the caterpillars' saliva that causes the Z isomers to isomerize to the corresponding E isomers.  It is the caterpillar spit that produces the distress call.

If you look closely at the Z molecules and the E molecules you will notice that there are actually two changes that take place.  First, the geometry around the alkene switches.   In general, the E isomer is more spread-out than the Z isomer and as a result it is lower in energy. Given a choice the alkene will usually adopt the E geometry.  If there is a catalyst available, this change is pretty easy to understand.

The second thing that changes is the location of the alkene, the  alkene moves closer to the oxygen end of the molecule.  Enzymes are very efficient molecules and they are very sensitive to shape.  My guess is that the "real" target for the isomerase in the caterpillar saliva is the aldehyde.  The aldehyde has a carbonyl group as well as the alkene and the most stable arrangement for these two functional groups is the one in hex-2-enal.  When the two double bonds are separated by only one single bond their orbitals are able to interact and form a conjugated system.  The conjugated version is more stable than the one where the two double bonds are farther apart and unable to interact with one another.

If improved conjugation in the product is the reason that the alkene moves from the 3-position to the 2-position, why does the alkene move in the alcohol and ester molecules too?  The alcohol has only one double bond since there is no C=O, so conjugation is not possible in this molecule.  And while the ester does have a C=O, it is too far away to interact with the 2-alkene to form a conjugated system.  What gives?

Enzymes can be very selective about the molecules that they react with, but they can also be forgiving if the structure is not exactly correct.  A lot of drugs affect specific enzymes in the body - the drug isn't exactly the correct shape, but it's close enough to bind to the enzyme.  In the case of the GLV's, the alcohol and ester molecules are close enough to the right shape to bind to the enzyme and react.  In the aldehyde the enzyme causes the alkene to migrate as well as change shape because it forms conjugated molecule.  Even though the alcohol and ester don't benefit from forming a product molecule that has conjugation, the enzyme treats them the same way it treats the aldehyde and the alkene migrates to the 2-position.

The other curious thing about this is the isomerase enzyme in the caterpillar saliva.  I would bet the reason the caterpillars make this enzyme has nothing to do with attracting big-eyed bugs to come eat the caterpillars, that would be counter productive. The plants probably evolved their GLV's to take advantage of this enzyme that the caterpillars make anyway.  So what is the isomerase "supposed" to do that benefits the caterpillars?

The smell of freshly-cut grass is actually a plant distress call | IO9.COM

Allmann S, & Baldwin IT (2010). Insects betray themselves in nature to predators by rapid isomerization of green leaf volatiles. Science (New York, N.Y.), 329 (5995), 1075-8 PMID: 20798319

How to safely put your hand into really scary liquids - fun with the Leidenfrost effect

Image via Wikipedia

Check out these two videos demonstrating the Leidenfrost effect.  If you have ever seen drops of water bounce around on a hot skillet, that's the Leidenfrost effect.



First Theo Gray puts his hand into liquid Nitrogen.  Liquid Nitrogen is really cold:  −196 °C, −321 °F.  You have probably seen demonstrations where something like a rubber ball or a rose is dipped in Liquid Nitrogen - on freezing at such a low temp most things will shatter if dropped or hit with a hammer.

Theo Gray dips his hand into a large container of liquid Nitrogen without developing a permanent case of frost bite by taking advantage of the Leidenfrost Effect.  Since his hand is much warmer than the liquid nitrogen, a very thin layer of gaseous nitrogen forms and acts as a protective barrier between the bulk liquid nitrogen and the surface of his hand.



Adam and Jamie demonstrated the same effect with molten lead on an episode of Mythbusters.  This is kind of the opposite of the liquid nitrogen case - instead of using an extremely cold liquid they are using a very hot liquid.  Lead melts at 621 °F, but they actually did the experiment at about 800 °F.

To be protected by the Leidenfrost effect they needed a thin layer of gas between their hands and the lead, so they dipped their hands in water and shook off the excess before putting their hands into the liquid lead.  The small amount of water on their hands vaporized to provide the thin, protective layer of gas between their skin and the liquid lead.  The fun starts about 2 minutes into the clip.



It goes without saying - making a mistake when doing this will have severe consequences. Don't try this at home.

You can safely stick your hand in liquid nitrogen...but you probably shouldn't | IO9.com

Gray Matter: In Which I Fully Submerge My Hand in Liquid Nitrogen | Popular Science

Laboratory Disaster Stories

Do you need some good reasons to wear your lab goggles?  Check out the Lab Horror Stories thread on Reddit.

Image via Wikipedia

 Here's one short and sweet example from an organic chemistry lab:

When I was in organic lab, my TA closed my heating reaction flask a little too tightly. It blew up. I pulled three pieces of glass out of my forehead right above my right eyebrow. The stopper hit my partner in the head. We lived long enough for the department to let us graduate.

Yay for goggles!

For educational and entertainment purposes only, please don't do any of these things yourself.


Link from Boingboing:
Or does it explode?: Reddit collection of laboratory disaster stories - Boing Boing

ChemSketch on Linux Again

Last year I wrote about using ChemSketch on Linux.  It is about the only Windows program that I regularly use these days.  Since switching to Linux I have not  completely settled on a chemical structure drawing program.  Sometimes I still use ChemSketch on Windows and then copy the image into OpenOffice, sometimes use another program on Linux - usually MarvinSketch.

Thanks to a comment left by Dragly on my original ChemSketch post in January, I can now reliably use ChemSketch on Linux.

ChemSketch is a Windows program, so I have to use Wine in order to run ChemSketch.  The problem was that ChemSketch would run fine the first time it is started after installation, but every other time I tried to run the program it would hang-up without the ChemSketch window ever appearing.

Dragly's comment referred me to:

http://markmail.org/message/grddjlgsn3dh5kqp

And he also pointed out that the program could be run with the window maximized by using this command, provided that the file path to the program is correct:

wine start /MAX C:\\WINDOWS\\TEMP\\ACDFREE12\\CHEMSK.EXE

This works, but it behaves a bit flakey for me running Ubuntu 10.04 and Wine 1.1.42.  First the ACD/Lab Products panel appears (very slowly) - after clicking the "OK" button, the program itself loads on the workspace to the right of the one I am working on. The 3D View program behaves the same way - you need to use:

wine start /MAX C:\\WINDOWS\\TEMP\\ACDFREE12\\SHOW3D.EXE 

to get it to open normally, and then it shifts one workspace to the right.

After digging around a bit, it turns out that the problem is in the Wine registry file, which for me is at

/home/steve/.wine/user.reg

This file is updated every time you close a program that is running under Wine.  The quick and dirty solution would be to delete this file before running ChemSketch.  Except for losing all the settings for every program you run with Wine, this works pretty well.  The program starts normally - if a bit slowly compared to Windows.

The clever thing to do would be to edit user.reg to delete the offending setting, which starts with

[Software\\Advanced Chemistry Development (ACD)\\Size]

and is followed by a bunch of numbers.  Deleting this setting allows you to run ChemSketch and the 3DViewer "normally."    This is a bit tedious but do-able.  To be really clever I should write a program to do it for me every time I run ChemSketch.

Under Windows, you can open the 3DViewer from ChemSketch by using the ACD/Labs menu. Unfortunately, when I run under Linux, this menu does not have any of the labels visible.  The first menu item is the 3DViewer.  Or you can right-click the ACD/Labs icon in the Gnome panel at the top of the screen and select the 3D Viewer to open it.

Copying between the ChemSketch and 3D Viewer windows works, and so do the Database search options.  The only remaining problem is getting the figure into an Open Office document.  You can't simply copy the image, nor can you insert an OLE object the way you would in Windows.  Instead you will need to save the figure as an image and import the image into the Open Office document.  The downsides of this are adding an extra step to save the image, and not being able to edit the image easily unless you also saved the original ChemSketch file.

Finding Buckyballs in Space

When you hear about molecules in interstellar space or on the moons of Saturn they tend to be small molecules like methane, ammonia or water. A big organic molecule would be something like glycine, the simplest amino acid, with only 5 "big" atoms (carbon, oxygen and nitrogen) and 5 Hydrogen atoms.  So finding buckyballs with 60 or 70 carbon atoms is really quite extraordinary.  It's a big difference, and buckyballs contain only carbon atoms - no other elements not even hydrogen, the most common element in the universe.

Buckminsterfullerene - C60

Image via Wikipedia

Using the Spitzer Space Telescope, an international reseach group has recently observed the buckminsterfullerenes C60 and C70 in Tc 1, a young Planetary Nebula (PN) with a white dwarf at the center.  The inner region of the nebula is carbon-rich, hydrogen-poor and dusty and this seems to be an important reason that they were able to see buckyballs there - buckyballs need lots of carbon in order to form, and they don't have any hydrogen in them at all.

The Hourglass Nebula

Image via Wikipedia

Most planetary nebulae have strong emissions from polycyclic aromatic hydrocarbons (PAH's) but not Tc 1.  Also missing, there are almost no simple hydrogen-containing molecules like HCN or C2H2.  A PAH would be like a small piece of a buckyball with hydrogens around the outside edge.  Once a buckyball started to form if there was any hydrogen around, hydrogen atoms could attach to the carbons on the edges resulting in a PAH instead of a buckyball.

from the research article:

On Earth, fullerenes can be synthesized by vaporizing graphite in a hydrogen-poor atmosphere that contains helium as a buffer gas. The fullerene formation process is very efficient, and C60 is by far the dominant and most stable species among the large cluster population formed in these experiments, followed by C70. However, fullerene formation is inhibited by the presence of hydrogen. The circumstellar environment of Tc 1 seems to be the astrophysical analog of such a laboratory setup.

They used Infra-Red (IR) spectroscopy to identify the buckyballs. It's especially useful in this context because it tells you what kinds of bonds there are in a molecule.  Visible light doesn't usually give a lot of useful information except for individual atoms, or maybe certain types of large, complex molecules. But IR gives you a lot of information about the bonds in a molecule.  IR spectra can be quite complex - the nifty thing with C60 is that for as large as it is, it has a very simple IR spectrum.

I had a difficult time finding an IR spectrum for C60 at the usual online chemistry databases (NIST Webbook, ChemSpider, SDBS). But this web page has a small image of the IR spectrum of C60.  It's a very simple spectrum with just 4 absorptions.  The molecular structure of C60 it looks intimidating, but it turns out that there are really only two kinds of bonds:  bonds that are shared between two 6-membered rings, and bonds shared between a 5-membered ring and a 6-membered ring. And the thing about IR spectroscopy is that it is highly dependent on symmetry.  C60 is highly symmetrical, so you only see 4 absorptions for it. C70 is the second most common buckyball.  It's not as symmetrical as C60, and as a result its spectrum is more complex that that of C60.

Cami, J., Bernard-Salas, J., Peeters, E., & Malek, S. (2010). Detection of C60 and C70 in a Young Planetary Nebula Science DOI: 10.1126/science.1192035

The Chemistry of Cthulhu?

I write like
H. P. Lovecraft

I Write Like by Mémoires, Mac journal software. Analyze your writing!

I haven't posted in a while - is this the reason?  

Was I tottering on the brink of cosmic horrors beyond man's power to hear?  

I suppose that some people might say of Organic Chemistry that 

... there is no language for such abysms of shrieking and immemorial lunacy, such eldrich contradictions of all matter, force, and cosmic order.

Image via Wikipedia

Thinking about Simplicity

Harvard Organic Chemistry professor George Whitesides takes a stab at defining "simplicity." Here's a wonderful, thoughtful talk for the end of the school year.

Top 30 Science Blogs at Times Online - Eureka Zone

The Eureka Zone science blog at the NY Times has a list of their top 30 science blogs.  If you are looking for science reading this is a great place to start.  I only wish there was a Chemistry blog or two on their list.

Times Online - Eureka Zone: Eureka's Top 30 Science Blogs