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Monday, March 19, 2012

Monday's Molecule #162

The last few challenges have been too easy so I'm going to make this week's molecule a bit more difficult. Not only do you have to identify the molecule but you also have to identify each of the four residues that are sugar derivatives. What is the molecule in blue and what are the other three sugary-looking residues?

Be sure to give a complete unambiguous name—that means getting the stereochemistry correct.

Post your answer in the comments. I'll hold off releasing any comments for 24 hours. The first one with the correct answer wins. I will only post correct answers to avoid embarrassment. The winner will be treated to a free lunch. I'll be setting up a lunch for this Thursday so expect an email message. If I owe you a lunch, it wouldn't hurt to remind me in case I forget you.

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.

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

UPDATE: The molecule is ganglioside GM2. The residues are N-acetyl-α-neuraminic acid (blue), N-acetyl-β-D-galactosamide, β-D-galactose, and β-D-glucose (left to right). You were asked to be specific in naming the sugar residues. Several people got the molecule correct but nobody named the sugar residues in a completely unambiguous manner, although the correct names are implied in the formal name of the molecule. There is no winner this week.

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


  1. It appears to be the ganglioside GM2.

    The sugar residues, from left to right, are N-Acetyl-D-galactosamine, D-Galactose, and D-Glucose. The blue residue is sialic acid (N-Acetylneuraminic acid).


  2. Raul A. Félix de SousaMonday, March 19, 2012 11:32:00 AM

    Molecule # 162 is ganglioside GM2 or β-D-GalNAc-(1→4)-[α-Neu5Ac-(2→3)]-β-D-Gal-(1→4)-β-D-Glc-(1↔1)-N-octadecanoylsphingosine (according to Wikipedia). The sugary residues are galactosamine, galactose and glucose. The blue part of the molecule is a Sialic (or N-Acetylneuraminic) acid residue. The lipophilic part of the molecule is stearylsphingosine.

  3. OK, the blue sugar is N-acetylneuraminic acid (sialic acid). The other three sugars, left to right, are N-acetyl-beta-D-galactosamine, beta-galactose, and beta-glucose. The aglycon is ceramide, which makes the whole molecule a glycosphingolipid. Looking at the list on wikipedia, this particular one seems to be known as the Tay Sachs ganglioside, or unambiguosly: β-D-GalNAc-(1→4)-[α-Neu5Ac-(2→3)]-β-D-Gal-(1→4)-β-D-Glc-(1↔1)-N-octadecanoylsphingosine.

  4. GM2 Ganglioside


    The blue residue is N-acetylneuraminic acid, the most common sialic acid in humans

    The neutral residues are (from left to right) N-acetylgalactosamine, galactose, and glucose

    GM2 is a cell membrane component and the molecule that accumulates in lysosomes in hexominidase A deficiency, or Tay Sachs disease.