Monday's Molecule #217

Last week's molecule was the 5′ cap structure on eukaryotic mRNA. Lot's of people got it right. The winners were Mark Sturtevant and Jacob Toth [Monday's Molecule #216].

As you know, the general public is very gullible. Millions of people have been duped into taking various supplements on the grounds that these supplements will improve their health and/or correct for a deficiency in their diet. These people will freely donate millions of dollars to the quacks who prey on their stupidity. Today's molecule is one of these supplements. Give the common name and the specific name that identifies this particular variant.

Email your answers to me at: Monday's Molecule #217. I'll hold off posting your answers for at least 24 hours. The first one with the correct answer wins. I will only post the names of people with mostly correct answers to avoid embarrassment. The winner will be treated to a free lunch.

There could be two winners. If the first correct answer isn't from an undergraduate student then I'll select a second winner from those undergraduates who post the correct answer. You will need to identify yourself as an undergraduate in order to win. (Put "undergraduate" at the bottom of your email message.)

Monday's Molecule #221

Last week's molecule was 2-oxo-4-hydroxy-4-carboxy-5-ureidoimidazoline (OHCU). It is an intermediate in the degradation pathway from uric acid (or urate) to carbon dioxide and ammonia. Uric acid is the main breakdown product in purine catabolism. Humans have lost activity of all of the enzymes of this pathway so they excrete urate. Most other species excrete ammonia, although in other animals some of the terminal enzymes have been lost.

Some textbooks do not show the uric acid degradation pathway since it doesn't occur in humans and those textbooks aren't interested in an evolutionary approach to biochemistry (e.g. Berg, Tymoczko, and Stryer). The other majors textbooks (Voet & Voet, Garrett & Grisham, Nelson & Cox [Lehinger]) all show uric acid converted directly to allantoin via urate oxidase. This reaction was shown to be incorrect about 15 years ago. The actual pathway from uric acid to allantoin involves two intermediates; 5-hydroxyisourate and OHCU.

Image Credit: Moran, L.A., Horton, H.R., Scrimgeour, K.G., and Perry, M.D. (2012) Principles of Biochemistry 5th ed., Pearson Education Inc. page 568 [Pearson: Principles of Biochemistry 5/E] © 2012 Pearson Education Inc.

The winner, for the second week in a row, is Jean-Marc Neuhaus. [Monday's Molecule #220]. Jean-Marc lives in Switzerland so I've made arrangements to fly over there to visit him and treat him to two fondues at the Pinte de Pierre-à-Bot in Neuchatel. Jean-Marc was kind enough to send me a menu [PDF]. There are about 30 different fondues to choose from. If you would like to join us you can leave a comment on last week's post.

This week's molecule is related to a discussion we are having on the How Do the IDiots Explain the Origin of Life? post. Can you identify this molecule? You have to be very specific.

Email your answer to me at: Monday's Molecule #221. I'll hold off posting your answers for at least 24 hours. The first one with the correct answer wins. I will only post the names of people with mostly correct answers to avoid embarrassment. The winner will be treated to a free lunch.

There could be two winners. If the first correct answer isn't from an undergraduate student then I'll select a second winner from those undergraduates who post the correct answer. You will need to identify yourself as an undergraduate in order to win. (Put "undergraduate" at the bottom of your email message.)

Monday's Molecule #207

Last week's molecule was N-acetylmuramic acid (MurNAc) one of the components of the polysaccharide in bacterial cell walls [Monday's Molecule #206]. The winner was Michael Florea. He should contact me by email to collect his winnings.

Today's (Tuesday's) molecule is a new addition to biochemistry textbooks because its structure was only solved a few years ago. There are plenty of hints in the figure. You have to identify the molecule AND each of the seven activities that are labelled. Bonus points for the PDB identification number and the species.

Email your answers to me at: Monday's Molecule #207. I'll hold off posting your answers for 24 hours. The first one with the correct answer wins. I will only post mostly correct answers to avoid embarrassment. The winner will be treated to a free lunch.

There could be two winners. If the first correct answer isn't from an undergraduate student then I'll select a second winner from those undergraduates who post the correct answer. You will need to identify yourself as an undergraduate in order to win. (Put "undergraduate" at the bottom of your email message.)

Monday's Molecule #224

Last week's molecule was the second messenger, phosphatidylinositol 4,5-bisphosphate or PIP₂. The winner is Dean Bruce. The undergraduate winner is Ariel Gershon [Monday's Molecule #223].

Today's molecule is a protein (purple). It's one of the most abundant proteins in E. coli because it's bound to almost all tRNA molecules in the cell. Name the protein (complete name, not just initials).

Email your answer to me at: Monday's Molecule #224. I'll hold off posting your answers for at least 24 hours. The first one with the correct answer wins. I will only post the names of people with mostly correct answers to avoid embarrassment. The winner will be treated to a free lunch.

There could be two winners. If the first correct answer isn't from an undergraduate student then I'll select a second winner from those undergraduates who post the correct answer. You will need to identify yourself as an undergraduate in order to win. (Put "undergraduate" at the bottom of your email message.)

Monday's Molecule #241

Last week's molecule (above) [Monday's Molecule #240] is a derivative of 2′-deoxythymidine triphosphate that's used in DNA sequencing reactions. The derivative has a 3′-O-azidomethyl group so that when this nucleotide is incorporated into a growing chain it cannot be extended because the 3′ -OH group is blocked. This is a chain-termination derivative. The large group attached to the methyl group at the C5 position on the thymine base is a color compound (a fluor). When this nucleotide is incorporated it stops chain growth, makes the DNA visible, and indicates that there's a T in the last position. The winner is James Wagstaff.

Almost all of you are familiar with today's molecule (right) although I suspect that many of you don't recognize it right away. Name the molecule—the common name will do—and briefly describe its biochemical function.

Email your answer to me at: Monday's Molecule #241. The first one with the correct answer wins. I will only post the names of winners to avoid embarrassment. The winner will be treated to a free lunch.

There could be two winners. If the first correct answer isn't from an undergraduate student then I'll select a second winner from those undergraduates who post the correct answer. You will need to identify yourself as an undergraduate in order to win. (Put "undergraduate" at the bottom of your email message.)

Monday's Molecule #198

The last "Monday's Molecule" was 2R,3S-isocitre [Monday's Molecule #197]. The winner was Evey Salara. She's probably too far away to come for lunch.

This week's molecule is very strange looking but it serves a very important role in some species. What is the molecule, what species have it, and what does it do?

Post your answer as a comment. I'll hold off releasing any comments for 24 hours. The first one with the correct answer wins. I will only post mostly correct answers to avoid embarrassment. The winner will be treated to a free lunch.

There could be two winners. If the first correct answer isn't from an undergraduate student then I'll select a second winner from those undergraduates who post the correct answer. You will need to identify yourself as an undergraduate in order to win. (Put "undergraduate" at the bottom of your comment.)

Monday's Molecule #106: Winners

 
UPDATE: The machine is a mass spectrometer and the technique illustrated is matrix-assisted desorption ionization (MALDI) coupled to time-of-flight (TOF) measurement (MADLI-TOF).

The first person to get it right was David Schuller of Cornell University. The first undergraduate from the Toronto area was Nova Syed of the University of Toronto.

---

This is the second week in a row that Monday's molecule has been on a Tuesday. Sorry for the delay. I promise to get back on schedule next week.

The observant among you might have noticed that this "Monday's" molecule is not a molecule. It's my version of a machine. You have to identify what kind of a machine this is and what it does.

There are two Nobel Laureates who get credit for developing the technique shown here. One of them is responsible for the specific technique and the other for a similar variant. Name the two Nobel Lauretes.

The first person to identify the machine/technique and the Nobel Laureates wins a free lunch at the Faculty Club. Previous winners are ineligible for one month from the time they first collected the prize.

There are six ineligible candidates for this week's reward: Bill Chaney of the University of Nebraska, Maria Altshuler of the university of Toronto, Ramon, address unknown, Jason Oakley of the University of Toronto, John Bothwell from the Marine Biological Association of the UK, in Plymouth (UK), and Wesley Butt of the University of Toronto

Bill and John have offered to donate their free lunch to a deserving undergraduate so the next two undergraduates to win and collect a free lunch can also invite a friend. Since undergraduates from the Toronto region are doing better in this contest, I'm going to continue to award an additional free lunch to the first undergraduate student who can accept a free lunch. Please indicate in your email message whether you are an undergraduate and whether you came make it for your free lunch (with a friend).

THEME:

Nobel Laureates
Send your guess to Sandwalk (sandwalk (at) bioinfo.med.utoronto.ca) and I'll pick the first email message that correctly identifies the molecule and names the Nobel Laureate(s). Note that I'm not going to repeat Nobel Laureate(s) so you might want to check the list of previous Sandwalk postings by clicking on the link in the theme box.

Correct responses will be posted tomorrow. I reserve the right to select multiple winners if several people get it right.

Comments will be blocked for 24 hours. Comments are now open.

---

Monday's Molecule #199

The last "Monday's Molecule" was phycoerythrin [Monday's Molecule #198]. The winner was Piotr Gasiorowski.

This week's molecule can do some very bad things to certain cells. You just have to give the common name and briefly explain what it does and how it works.

Post your answer as a comment. I'll hold off releasing any comments for 24 hours. The first one with the correct answer wins. I will only post mostly correct answers to avoid embarrassment. The winner will be treated to a free lunch.

There could be two winners. If the first correct answer isn't from an undergraduate student then I'll select a second winner from those undergraduates who post the correct answer. You will need to identify yourself as an undergraduate in order to win. (Put "undergraduate" at the bottom of your comment.)

Monday's Molecule #106

 
This is the second week in a row that Monday's molecule has been on a Tuesday. Sorry for the delay. I promise to get back on schedule next week.

The observant among you might have noticed that this "Monday's" molecule is not a molecule. It's my version of a machine. You have to identify what kind of a machine this is and what it does.

There are two Nobel Laureates who get credit for developing the technique shown here. One of them is responsible for the specific technique and the other for a similar variant. Name the two Nobel Lauretes.

The first person to identify the machine/technique and the Nobel Laureates wins a free lunch at the Faculty Club. Previous winners are ineligible for one month from the time they first collected the prize.

There are six ineligible candidates for this week's reward: Bill Chaney of the University of Nebraska, Maria Altshuler of the university of Toronto, Ramon, address unknown, Jason Oakley of the University of Toronto, John Bothwell from the Marine Biological Association of the UK, in Plymouth (UK), and Wesley Butt of the University of Toronto

Bill and John have offered to donate their free lunch to a deserving undergraduate so the next two undergraduates to win and collect a free lunch can also invite a friend. Since undergraduates from the Toronto region are doing better in this contest, I'm going to continue to award an additional free lunch to the first undergraduate student who can accept a free lunch. Please indicate in your email message whether you are an undergraduate and whether you came make it for your free lunch (with a friend).

THEME:

Nobel Laureates
Send your guess to Sandwalk (sandwalk (at) bioinfo.med.utoronto.ca) and I'll pick the first email message that correctly identifies the molecule and names the Nobel Laureate(s). Note that I'm not going to repeat Nobel Laureate(s) so you might want to check the list of previous Sandwalk postings by clicking on the link in the theme box.

Correct responses will be posted tomorrow. I reserve the right to select multiple winners if several people get it right.

Comments will be blocked for 24 hours.

---

Monday's Molecule #209

Last week's molecule was depicted on a stamp honoring Gerty Cori. It was supposed to be the "Cori ester" (glucose 1-phosphate) but the image shown on the stamp is not correct. Nobody recognized that so there was no winner last week [Monday's Molecule #208].

Today's molecule is a very famous RNA with secondary structure. Do you recognize it without BLASTing the sequence?

Email your answers to me at: Monday's Molecule #209. I'll hold off posting your answers for 24 hours. The first one with the correct answer wins. I will only post mostly correct answers to avoid embarrassment. The winner will be treated to a free lunch.

There could be two winners. If the first correct answer isn't from an undergraduate student then I'll select a second winner from those undergraduates who post the correct answer. You will need to identify yourself as an undergraduate in order to win. (Put "undergraduate" at the bottom of your email message.)

Monday's Molecule #211

Last week's molecule was the the R stereoisomer of ibuprofen [((R)-2-(4-(2-methylpropyl)phenyl)propanoic acid]. The winner was undergraduate Jacob Toth. [Monday's Molecule #210].

Today's molecule is an easy one. All you have to do is give the common name and a brief explanation of its significance.

Email your answers to me at: Monday's Molecule #211. I'll hold off posting your answers for 24 hours. The first one with the correct answer wins. I will only post the names of people with mostly correct answers to avoid embarrassment. The winner will be treated to a free lunch.

There could be two winners. If the first correct answer isn't from an undergraduate student then I'll select a second winner from those undergraduates who post the correct answer. You will need to identify yourself as an undergraduate in order to win. (Put "undergraduate" at the bottom of your email message.)

Monday's Molecule #183

Last week's molecule was a small protein machine that pumps protons across a membrane (ubiquinol:cytochrome c oxidoreductase) [Monday's Molecule #182]. The winner was Stephen Spiro. I think he's a student at the University of Toronto (UT) but it's a campus I haven't heard of in a place called "Dallas."

This week's molecule is a lot less complicated although it's rather strange looking. This molecule has a very specific use. Name the molecule—the common name will do—and describe its use.

Post your answers as a comment. I'll hold off releasing any comments for 24 hours. The first one with the correct answer wins. I will only post mostly correct answers to avoid embarrassment. The winner will be treated to a free lunch.

There could be two winners. If the first correct answer isn't from an undergraduate student then I'll select a second winner from those undergraduates who post the correct answer. You will need to identify yourself as an undergraduate in order to win. (Put "undergraduate" at the bottom of your comment.)

Some past winners are from distant lands so their chances of taking up my offer of a free lunch are slim. (That's why I can afford to do this!)

In order to win you must post your correct name. Anonymous and pseudoanonymous commenters can't win the free lunch.

Winners will have to contact me by email to arrange a lunch date. Please try and beat the regular winners. Most of them live far away and I'll never get to take them to lunch. This makes me sad.

Comments are invisible for 24 hours. Comments are now open.

UPDATE: The molecule is raltitrexed, also known as Tomudex. It's an inhibitor of the enzyme thymidylate synthase, the enzyme responsible for converting dUMP to dTMP. The drug is effective as an anti-cancer agent since it prevents cell division by blocking DNA synthesis. The winner is Raul A. Félix de Sousa (again).

Winners
Nov. 2009: Jason Oakley, Alex Ling
Oct. 17: Bill Chaney, Roger Fan
Oct. 24: DK
Oct. 31: Joseph C. Somody
Nov. 7: Jason Oakley
Nov. 15: Thomas Ferraro, Vipulan Vigneswaran
Nov. 21: Vipulan Vigneswaran (honorary mention to Raul A. Félix de Sousa)
Nov. 28: Philip Rodger
Dec. 5: 凌嘉誠 (Alex Ling)
Dec. 12: Bill Chaney
Dec. 19: Joseph C. Somody
Jan. 9: Dima Klenchin
Jan. 23: David Schuller
Jan. 30: Peter Monaghan
Feb. 7: Thomas Ferraro, Charles Motraghi
Feb. 13: Joseph C. Somody
March 5: Albi Celaj
March 12: Bill Chaney, Raul A. Félix de Sousa
March 19: no winner
March 26: John Runnels, Raul A. Félix de Sousa
April 2: Sean Ridout
April 9: no winner
April 16: Raul A. Félix de Sousa
April 23: Dima Klenchin, Deena Allan
April 30: Sean Ridout
May 7: Matt McFarlane
May 14: no winner
May 21: no winner
May 29: Mike Hamilton, Dmitri Tchigvintsev
June 4: Bill Chaney, Matt McFarlane
June 18: Raul A. Félix de Sousa
June 25: Raul A. Félix de Sousa
July 2: Raul A. Félix de Sousa
July 16: Sean Ridout, William Grecia
July 23: Raul A. Félix de Sousa
July 30: Bill Chaney and Raul A. Félix de Sousa
Aug. 7: Raul A. Félix de Sousa
Aug. 13: Matt McFarlane
Aug. 20: Stephen Spiro
Aug. 27: Raul A. Félix de Sousa

---

Monday's Molecule #142

 
Sometimes it's almost impossible to find an image of a specific molecule that honors a Nobel Laureate. This is one of those times.

The diagram provides all the clues necessary to identify an important process and then to identify a particular molecule associated with this week's Nobel Laureate.

You must name the molecule and the Nobel Laureate. Be careful 'cause it's easy to make a mistake and name someone who has already been the subject of a Monday's Molecule.

The first person to identify the molecule and name the Nobel Laureate(s) wins a free lunch. Previous winners are ineligible for six weeks from the time they first won the prize.

There are only six ineligible candidates for this week's reward: Frank Schmidt of the University of Missouri, Joshua Johnson of Victoria University in Australia, Markus-Frederik Bohn of the Lehrstuhl für Biotechnik in Erlangen, Germany, Jason Oakley a biochemistry student at the University of Toronto, Dima Klenchin of the University of Wisconsin, Madison and Alex Ling of the University of Toronto.

Joshua and Dima have agreed to donate their free lunch to an undergraduate. Consequently, I have two extra free lunches for deserving undergraduates so I'm going to award an additional prize to the first undergraduate student who can accept it. Please indicate in your email message whether you are an undergraduate and whether you can make it for lunch. If you can't make it for lunch then please consider donating it to someone who can in the next round.

THEME:

Nobel Laureates
Send your guess to Sandwalk (sandwalk (at) bioinfo.med.utoronto.ca) and I'll pick the first email message that correctly identifies the molecule(s) and names the Nobel Laureate(s). Note that I'm not going to repeat Nobel Prizes so you might want to check the list of previous Sandwalk postings by clicking on the link in the theme box.

Correct responses will be posted tomorrow.

Comments will be blocked for 24 hours. Comments are now open.

---

Monday's Molecule #33

 
Today's molecule is complex. The short common name of this molecule is sufficient but you're more than welcome to supply the IUPAC name if you know it. There's a direct connection between this Monday's Molecule and Wednesday's Nobel Laureate. (Hint: this molecule is not mentioned in the description of the award but the class of molecules to which it belongs is mentioned.)

The reward (free lunch) goes to the person who correctly identifies the molecule and the Nobel Laureate(s). Previous free lunch winners are ineligible for one month from the time they first collected the prize. There's only one (Marc) ineligible candidates for this Wednesday's reward since many recent winners haven't collected their prize. The prize is a free lunch at the Faculty Club.

Comments will be blocked for 24 hours. Comments are now open.

UPDATE: The molecule is ergosterol, a plant sterol that is a precursor to vitamin D. Ultraviolet irradiation converts ergosterol to vitamin D₂.

Monday's Molecule #36

 
Today's molecule is complex. It has a strange-looking ring structure. The short common name of this molecule is well known but your task—should you choose to accept it— is to supply the correct IUPAC name. There's an indirect connection between this Monday's Molecule and Wednesday's Nobel Laureate(s). (The molecule also has a connection to Intelligent Design Creationism.)

The reward (free lunch) goes to the person who correctly identifies the molecule and predicts the Nobel Laureate(s). Previous free lunch winners are ineligible for one month from the time they first collected the prize. There's only one (Marc) ineligible candidates for this Wednesday's reward since many recent winners haven't collected their prize. The prize is a free lunch at the Faculty Club. The bonus is a free drink (alcoholic) with your lunch if you guess the connection to Intelligent Design Creationism.

Comments will be blocked for 24 hours. Comments are now open.

THEME:
Malaria
UPDATE The molecule is quinine, a drug used in the treatment of malaria. The Noble Laureates are Charles Laveran (1907) and Ronald Ross (1902)

Monday's Molecule #108

 
Today's Monday's Molecule really is a molecule. Your task is to identify the molecule from the cartoon shown here. It won't be sufficient to just find the name of the molecule, you will also have to identify the significance behind determining its chemical structure.

There's one scientist who was involved in that determination who also did some important work based, in part, on knowing the sequence. This scientist was awarded a Nobel Prize for his work but the prize didn't come until 15 years later. Name this Nobel Laureate.

The first person to identify the molecule and the Nobel Laureate wins a free lunch at the Faculty Club. Previous winners are ineligible for one month from the time they first won the prize.

There are eight ineligible candidates for this week's reward: Ramon, address unknown, Jason Oakley of the University of Toronto, John Bothwell from the Marine Biological Association of the UK, in Plymouth (UK), Wesley Butt of the University of Toronto, David Schuller of Cornell University, Nova Syed of the University of Toronto, Dima Klenchin of the University of Wisconsin and undergraduate Alex Ling of the University of Toronto

John, David, and Dima have offered to donate their free lunch to a deserving undergraduate so I'm going to continue to award an additional free lunch to the first undergraduate student who can accept a free lunch. Please indicate in your email message whether you are an undergraduate and whether you came make it for your free lunch (with a friend).

THEME:

Nobel Laureates
Send your guess to Sandwalk (sandwalk (at) bioinfo.med.utoronto.ca) and I'll pick the first email message that correctly identifies the molecule and names the Nobel Laureate(s). Note that I'm not going to repeat Nobel Laureate(s) so you might want to check the list of previous Sandwalk postings by clicking on the link in the theme box.

Correct responses will be posted tomorrow. I reserve the right to select multiple winners if several people get it right.

Comments will be blocked for 24 hours.

---

Monday's Molecule #31

 
Today's molecule is complicated but it makes a lot of sense if you know your basic biochemistry. We don't need a long complicated name this time. It's sufficient to simply describe what you're looking at and why it's significant. You have to identify the key residue to get credit for the answer.

As usual, there's a connection between Monday's molecule and this Wednesday's Nobel Laureate(s). This one is an obvious direct connection. Once you have identified the molecule you should be able to name the Nobel Laureate(s).

The reward (free lunch) goes to the person who correctly identifies the molecule and the reaction and the Nobel Laureate(s). Previous free lunch winners are ineligible for one month from the time they first collected the prize. There are no ineligible candidates for this Wednesday's reward since recent winners (including last week's winner, "Kyo") have declined the prize on the grounds that they live in another country and can't make it for lunch on Thursday (a feeble excuse, in my opinion, haven't you heard of airplanes?).

Comments will be blocked for 24 hours. Comments are now open.

UPDATE: The molecule is the lariat structure of the RNA splicing intermediate. The key residue is the adenylate residue that's joined through its 2′ hydroxyl group to the 5′ end of the intron [see RNA Splicing: Introns and Exons]. The Nobel Laureates are Rich Roberts and Phil Sharp. (See the comments for an interesting anecdote concerning the discovery of this molecule.)

Monday's Molecule #105: The winners

 
 
Monday's molecule is on Tuesday this week. Sorry for the delay, I've been busy with a mid-term test in my introductory biochemistry course.

You have to identify this molecule. The role of this molecule in a particular species was elucidated by a Nobel Laureate in the second half of the 20th century. We need the name of the Nobel Laureate who first isolated and characterized the protein.

Your task is to correctly identify the molecule and the species from which it was purified. You also need to name the Nobel Laureate. The first one to do so wins a free lunch at the Faculty Club. Previous winners are ineligible for one month from the time they first collected the prize.

There are five ineligible candidates for this week's reward: Dima Klenchin of the University of Wisconsin, Bill Chaney of the University of Nebraska, Maria Altshuler of the university of Toronto, Ramon, address unknown, and Jason Oakley of the University of Toronto.

Dima and Bill have offered to donate their free lunch to a deserving undergraduate so the next two undergraduates to win and collect a free lunch can also invite a friend. Since undergraduates from the Toronto region are doing better in this contest, I'm going to continue to award an additional free lunch to the first undergraduate student who can accept a free lunch. Please indicate in your email message whether you are an undergraduate and whether you came make it for your free lunch (with a friend).

THEME:

Nobel Laureates
Send your guess to Sandwalk (sandwalk (at) bioinfo.med.utoronto.ca) and I'll pick the first email message that correctly identifies the molecule and names the Nobel Laureate(s). Note that I'm not going to repeat Nobel Laureate(s) so you might want to check the list of previous Sandwalk postings by clicking on the link in the theme box.

Correct responses will be posted tomorrow. I reserve the right to select multiple winners if several people get it right.

Comments will be blocked for 24 hours. Comments are now open.

UPDATE:The molecule is green fluorescent protein from the jellyfish Aequorea victoria. The Nobel Laureate is Osamu Shimomura (2008).

The winner is John Bothwell (again) from the Marine Biological Association of the UK, in Plymouth (UK). The local winner is Wesley Butt of the University of Toronto.

---

Monday's Molecule #75

 
Some readers have been complaining that Monday's Molecule is too easy.¹ That's why I've chosen a more difficult task for you today.

You have to examine the structure and figure out what's going on. The molecule you have to identify isn't even shown in the figure—only small fragments are depicted. You need to identify the invisible molecule and explain why this figure is so important. Its importance is mostly historical. The elucidation of what's happening is a defining moment in biochemistry and helped open up a whole new field of study.

There's a direct connection between today's molecule and a Nobel Prize. The prize was awarded for discovering exactly what the figure depicts. The first person to correctly identify the molecule, describe what the figure shows, and name the Nobel Laureate(s), wins a free lunch at the Faculty Club. Previous winners are ineligible for one month from the time they first collected the prize. There are three ineligible candidates for this week's reward.

THEME:

Nobel Laureates
Send your guess to Sandwalk (sandwalk (at) bioinfo.med.utoronto.ca) and I'll pick the first email message that correctly identifies the molecule and names the Nobel Laureate(s). Note that I'm not going to repeat Nobel Laureate(s) so you might want to check the list of previous Sandwalk postings by clicking on the link in the theme box. [Hint: A co-recipient of this week's Nobel Laureates is already on the list.]

Correct responses will be posted tomorrow. I may select multiple winners if several people get it right. (Like that's going to happen this week!)

Comments will be blocked for 24 hours. Comments are now open.

UPDATE: Turns out it wasn't as difficult as I thought. The winning answer arrived within one hour, followed shortly by several other correct answers. The image shows a small piece of RNA about to be cleaved in the active site of Ribonuclease A. The key residues are His12, His119, and Lys 41 and their interactions with the substrate are shown. Note how they form weak interactions with the phosphodiester linkage. This causes destabilization of the bonds in preparation for cleavage. The Nobel Laureates are Stanford Moore and William Stein who received the Nobel Prize in 1972 for working out the mechanism of Ribonuclease A. This was the first detailed demonstration of how enzymes worked at the molecular level.

The winner is Michael Clarkson. Congratulations Michael.

---

1. Okay, maybe not "some" readers. Maybe it's only one reader. In fact, maybe I'm the reader.

Monday's Molecule #220

Last week's molecule was citrate synthase, one of many enzymes that show considerable amounts of structural change during binding. It looks like the "induced fit" mechanism is a general feature of substrate binding and not something that is limited to just a few examples. That part of the question was easy but the second part was hard. Jean-Marc Neuhaus is this week's winner because he has a copy of my book and was able to look up the explanation. The important point to keep in mind when you are thinking about the thermodynamics of biochemical reactions is that most reactions are near-equilibrium reactions where ΔG = 0. In the case of the citrate synthase reaction, ΔG°′ = -31.5 kJ mol^-1, in the direction of citrate formation. What this means is that the equilibrium concentrations of the products are very much higher than the concentrations of the substrates. These concentrations would be closer to being equal if the reaction was coupled to substrate level phosphorylation (e.g. ATP formation). This would be a problem since the concentration of oxaloacetate (substrate) inside the cell is very low. (Because the standard free energy change of the malate dehydrogenase reaction is ΔG°′ = +30 kJ mol^-1) [Monday's Molecule #219]. Jean-Marc lives in Switzerland so I've made arrangements to fly over there to visit him and treat him to fondue at the Pinte de Pierre-à-Bot in Neuchatel.

Today's molecule is one of those molecules that students should never be asked to memorize. It's an intermediate in a very important pathway. Identify the molecule and the pathway. You have to give me the full name and the common abbreviation. Email your answer to me at: Monday's Molecule #220. I'll hold off posting your answers for at least 24 hours. The first one with the correct answer wins. I will only post the names of people with mostly correct answers to avoid embarrassment. The winner will be treated to a free lunch.

There could be two winners. If the first correct answer isn't from an undergraduate student then I'll select a second winner from those undergraduates who post the correct answer. You will need to identify yourself as an undergraduate in order to win. (Put "undergraduate" at the bottom of your email message.)