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Wednesday, October 23, 2024

Nobel Laureate: Vincent du Vigneaud


The Nobel Prize in Chemistry 1955
"for his work on biochemically important sulphur compounds, especially for the first synthesis of a polypeptide hormone"

Vincent du Vigneaud (1901-1978) was an American biochemist who was awarded the Nobel Prize in Chemistry in 1955 for his work on biological molecules containing sulfur, especially methionine cystine, and biotin. The prize was for solving the structure of the peptide hormone oxytocin and synthesizing an active molecule. (See Monday's Molecule #244.) From 1938 to 1967 Vigneaud's lab was at Cornell Medical College in New York City.

Here's part of the Presentation Speech.

THEME:
Nobel Laureates

Underneath the brain, there is a small, well-protected gland, the pituitary gland. In man it is about as big as a bean. There are secreted several hormones, that is, substances which regulate important physiological functions. spite of its small size, the pituitary gland is made up of several distinct parts with different functions. We are interested here in the posterior lobe, which contains two substances called oxytocin and vasopressin. The former stimulates the contractions of the uterus and also the lactation, the latter raises the blood pressure and regulates the function of the kidneys. As early as in 1933, when rather impure preparations from the posterior lobe were used in experiments, du Vigneaud found a high percentage of sulphur, which seemed to be correlated to the physiological activity.

Using the experimental methods, which the development of science has put at his disposal and making the best of his own intimate knowledge of the organic chemistry of sulphur, du Vigneaud has step by step forced his way. Both hormones were isolated in a state of purity, and it was found that they are built up from amino acids in the same way as proteins, but with a far lower molecular weight. Such compounds are, as distinguished from real proteins, called polypeptides. The nature of the amino acids and their positions in the molecule could be determined. The sulphur is present in cystine. The two hormones have a very similar structure; both contain eight amino acids, connected to a chain, which at one point is closed to a ring. The molecule has some resemblance to a figure six or nine, where the loop contains five amino acids and the “tail” three. Two sulphur atoms, linked to each other, form a part of the ring.

The design of the molecule was thus known. It remained to build it up by synthesis and check the correctness of the design. That was perhaps the most difficult part of the work. The interest was first concentrated on the synthesis of oxytocin. Step by step the amino-acid chain was built up with the two sulphur atoms in the proper positions, one at the end of the chain and the other near the middle. At last the ring was closed by formation of a bond between the sulphur atoms. Now followed the most thrilling moment, the testing of the chemical properties and the physiological activity; perhaps there had been some mistake after all. It turned out, however, that the synthetic polypeptide was identical with the natural product.



The images of the Nobel Prize medals are registered trademarks of the Nobel Foundation (© The Nobel Foundation). They are used here, with permission, for educational purposes only.

Monday, October 21, 2024

Monday's Molecule #244

You can use whatever tricks you want to identify today's molecule but I'll be really impressed with anyone who recognizes it right away. Regular readers will know that it's related to at least one Nobel Prize Laureate who will be revealed on Wednesday. I don't think that's going to help you very much.

Email your answer to me at: Monday's Molecule #244. 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 coffee and donut at Tim Hortons if you are ever in Toronto or Mississauga (Ontario, Canada).

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.)

In order to win you must give your correct name. Anonymous and pseudoanonymous players can't win.

Comments are closed for at least 24 hours.

UPDATE: The winner is Santi Garcia-Vallve who correctly guessed that the molecule is the peptide hormone oxytocin. Santi lives in Spain so he won't be able to collect his coffee and donut anytime soon.

Winners

#145, Oct. 17, 2011: Bill Chaney, Roger Fan
#146, Oct. 24, 2011: DK
#147, Oct. 31, 2011: Joseph C. Somody
#148, Nov. 7, 2011: Jason Oakley
#149, Nov. 15, 2011: Thomas Ferraro, Vipulan Vigneswaran
#150, Nov. 21, 2011: Vipulan Vigneswaran (honorary mention to Raul A. Félix de Sousa)
#151, Nov. 28, 2011: Philip Rodger
#152, Dec. 5, 2011: 凌嘉誠 (Alex Ling)
#153, Dec. 12, 2011: Bill Chaney
#154, Dec. 19, 2011: Joseph C. Somody
#155, Jan. 9, 2012: Dima Klenchin
#156, Jan. 23, 2012: David Schuller
#157, Jan. 30, 2012: Peter Monaghan
#158, Feb. 7, 2012: Thomas Ferraro, Charles Motraghi
#159, Feb. 13, 2012: Joseph C. Somody
#160, March 5, 2012: Albi Celaj
#161, March 12, 2012: Bill Chaney, Raul A. Félix de Sousa
#162, March 19, 2012: no winner
#163, March 26, 2012: John Runnels, Raul A. Félix de Sousa
#164, April 2, 2012: Sean Ridout
#165, April 9, 2012: no winner
#166, April 16, 2012: Raul A. Félix de Sousa
#167, April 23, 2012: Dima Klenchin, Deena Allan
#168, April 30, 2012: Sean Ridout
#169, May 7, 2012: Matt McFarlane
#170, May 14, 2012: no winner
#171, May 21, 2012: no winner
#172, May 29, 2012: Mike Hamilton, Dmitri Tchigvintsev
#173, June 4, 2012: Bill Chaney, Matt McFarlane
#174, June 18, 2012: Raul A. Félix de Sousa
#175, June 25, 2012: Raul A. Félix de Sousa
#176, July 2, 2012: Raul A. Félix de Sousa
#177, July 16, 2012: Sean Ridout, William Grecia
#178, July 23, 2012: Raul A. Félix de Sousa
#179, July 30, 2012: Bill Chaney and Raul A. Félix de Sousa
#180, Aug. 7, 2012: Raul A. Félix de Sousa
#181, Aug. 13, 2012: Matt McFarlane
#182, Aug. 20, 2012: Stephen Spiro
#183, Aug. 27, 2012: Raul A. Félix de Sousa
#184, Sept. 3, 2012: Matt McFarlane
#185, Sept. 10, 2012: Matt Talarico
#186, Sept. 17, 2012: no winner
#187, Sept. 24, 2012: Mikkel Rasmussen
#188, Oct. 1, 2012: John Runnels
#189, Oct. 8, 2012: Raúl Mancera
#190, Oct. 15, 2012: Raul A. Félix de Sousa
#191, Oct. 22, 2012: Mikkel Rasmussen
#192, Nov. 12, 2012: Seth Kasowitz, Bill Gunn
#193, Nov. 19, 2012: Michael Rasmussen
#194, Dec. 4, 2012: Paul Clapham, Jacob Toth
#195, Dec. 10, 2012: Jacob Toth
#196, Dec. 17, 2012: Bill Chaney, Dima Klenchin, Bill Gunn
#197, Jan. 14, 2013: Evey Salara
#198, Jan. 21, 2013: Piotr Gasiorowski
#199, March 11, 2013: Bill Gunn, River Jiang
#200, March 18, 2013: Bill Gunn
#201, April 8, 2013: Michael Florea
#202, April 15, 2013: no winner
#203, April 29, 2013: Anders Ernberg
#204, May 6, 2013: Alex Ling, Michael Florea
#205, May 13, 2013: Bill Chaney
#206, June 24, 2013: Michael Florea
#207, July 2, 2013: Matt McFarlane
#208, July 8, 2013: no winner
#209, July 15, 2013: Rosie Redfield, Thuc Quyen Huynh
#210, July 22, 2013: Jacob Toth
#211, July 29, 2013: Alex Ling, Matt McFarlane
#212, August 5, 2013: Brian Shewchuk
#213, Sept. 2, 2013: no winner
#214, Sept. 9, 2013: Bill Chaney
#215, Sept. 16, 2013: Zhimeng Yu
#216, Sept. 23, 2013: Mark Sturtevant, Jacob Toth
#217, Sept. 30, 2013: Susan Heaphy
#218, Oct. 7, 2013: Piotr Gasiorowski, Jacob Troth
#219, Oct. 14, 2013: Jean-Marc Neuhaus
#220, Oct. 21, 2013: Jean-Marc Neuhaus
#221, Oct. 28, 2013: Zhimeng Yu
#222, Nov. 10, 2013: Caroline Josefsson, Andrew Wallace
#223, Nov. 18, 2013: Dean Bruce, Ariel Gershon
#224, Nov. 25, 2013: Jon Nuelle, Ariel Gershon
#225, Dec. 2, 2013: Jean-Marc Neuhaus
#226, Dec. 9, 2013: Bill Gunn
#227, Dec. 16, 2013: Piotr Gasiorowski
#228, Jan. 13, 2014: Tom Mueller
#229, Jan. 20, 2014: Tommy Stuleanu
#230, Jan. 27, 2014: Bill Gunn, Ariel Gershon
#231; March 3, 2014: Keith Conover, Nevraj Kejiou
#232, March 10, 2014: Philip Johnson
#233, March 17, 2014: Jean-Marc Neuhaus
#234, March 24, 2014: Frank Schmidt, Raul Félix de Sousa
#235, March 31, 2014: Jon Binkley
#236, April 7, 2014: no winner
#237, April 21, 2014: Dean Bruce
#238, April 28, 2014: Dean Bruce
#239, May 5, 2014: Piotr Gąsiorowski
#240, May 12, 2014: James Wagstaff
#241, May 19, 2014: no winner
#242, Oct. 7, 2024: Elie Huvier
#243, Oct. 14, 2024: Mikkel Rasmussen
#244, Oct. 21, 2024: Santi Garcia-Vallve

Philip Ball strikes back

Philip Ball believes that we are in the middle of a revolution in our way of thinking about how life works. His ideas are complex but part of his case involves molecular biology and how things work at the molecular level. Ball believes that the old view of molecular biology placed far too much emphasis on coding DNA and ignored all the other functional regions of genomes. He also says that most of our genes specify non-coding RNA instead of mRNA and implies to his readers that a very large fraction of our genome is functional (i.e. not junk).1

In order to build the case for revolution, he tries to demonstrate a paradigm shift in our view of molecular biology by showing a huge gap between the understanding of previous generations of molecular biologists and the post-genomic view. I believe he is wrong about this for two reasons: first, he misrepresents the views of older molecular biologists and, second he misrepresents the discoveries of the past twenty years. I tried to explain why he was wrong about these two claims in a previous post where I discussed an article he published in Scientific American in May 2024: Philip Ball says RNA may rule our genome.

Philip Ball responded to my criticism in a comment under that article.

Older molecular biologists were really stupid

I said ...

Ball begins with the same old myth that writers like him have been repeating for many years. He claims that before ENCODE most molecular biologists were really stupid. According to Philip Ball, most of us thought that coding DNA was the only functional part of the genome and most of the rest was junk DNA.

In the comment section of my earlier post, Philip Ball says,

I’m sorry to say that Larry’s commentary here is dismayingly inaccurate.

Let’s get this one out of the way first:

“He claims that before ENCODE most molecular biologists were really stupid.”

I have never made this claim and never would – it is a pure fabrication on Larry’s part. I guess this is what John Horgan meant in his comment to Larry: credible writers don’t just make up stuff.

I admit that Philip Ball never said those exact words. I'll leave it to the readers to decide whether my characterization of his position is accurate.

I stand by the statements I made although I admit to a bit of hyperbole. Ball has said repeatedly that the molecular biologists of my generation were wedded to the idea that coding regions were the only important part of the genome and he often connects that to the Central Dogma of Molecular Biology. He also claims that the experts in molecular biology dismissed all non-coding DNA as junk. Here's how he puts it in another article that he published recently in Aeon: We are not machines.

Only around 1-2 per cent of the entire human genome actually consists of protein-coding genes. The remainder was long thought to be mostly junk: meaningless sequences accumulated over the course of evolution. But at least some of that non-coding genome is now known to be involved in regulating genes: altering, activating or suppressing their transcription in RNA and translation into proteins.

I interpret that to mean that older molecular biologists, like me, didn't know about functional non-coding DNAs such as centromeres, telomeres, origins of replication, non-coding genes, SARs, and regulatory sequences in spite of the fact that thousands of papers on these sequences were published in the 30 years that preceded the publication of the first draft of the human genome sequence. This is not true, we did know about those things. I don't think it's too much of an exaggeration to say that Philip Ball thinks we were really stupid.

Here's what he says in his book, "How Life Works" (p. 85) when he's talking about the beginning of the human genome project.

Even at its outset, it faced the somewhat troubling issue that just 2 percent or so of our genome actually accounts for protein-coding genes. The conventional narrative was that our biology was all about proteins, for each of which the genome held the template. ... But we had all this other DNA too! What was it for? The common view was that it was mostly just junk, like the stuff in our attics: meaningless material accumulated during evolution, which our cells had no motivation to clear out.

Again, his claim is that in 1990 at the beginning of the human genome project the experts in molecular biology thought that non-coding DNA was mostly junk (98% of the genome). I have repeatedly refuted this myth and challenged anyone to come up with a single scientific paper arguing that all non-coding DNA is junk. I challenge Philip Ball to find a single molecular biology textbook written before 1990 that fails to discuss regulation, non-coding genes, and other non-coding functional elements in the human genome.

The truth is that the molecular biology experts concluded in the 1970s that we had about 30,000 genes and that 90% of our genome is junk and 10% is functional. That 10% consisted of about 2% coding DNA (now thought to be only 1%) and 8% functional non-coding DNA. So the "conventional narrative" was that there was a lot more functional non-coding DNA than coding DNA.

The human genome is full of genes for regulatory RNAs.

"Ball is one of the most meticulous, precise science writers out there. He is the antithesis of hypey, "dumb-it-down" reporting. He is MUCH more credible than you are, Laurence."

John Horgan July, 2024
The title of the article I was discussing is "Revolutionary Genetics Research Shows RNA May Rule Our Genome." In that article Ball says that ENCODE was basically right and there are many more non-coding genes than protein-coding genes. I pointed out that Ball mentions some criticism of this idea but only to dismiss it. I said that "[Ball] wants you to believe that almost of all of those transcripts are functional—that's the revolution that he's promoting." Philip Ball objects to this statement ...

This too is sheer fabrication. I don’t say this in my article, nor in my book. Instead, I say pretty much what Larry seems to want me to say, but for some reason he will not admit it – which is that there is controversy about how many of the transcripts are functional."

Ball states that "ENCODE was basically right" when they claimed that 75% of our genome was transcribed and he goes on to say that ...

Dozens of other research groups, scoping out activity along the human genome, also have found that much of our DNA is churning out 'noncoding' RNA.

He says that ENCODE has identified 37,000 noncoding genes but there may be as many as 96,000. After making these definitive statements, he mentions that there are "still doubters" but then discuss why these discoveries are revolutionary. Later on he quotes John Mattick suspecting that there may be more that 500,000 non-coding genes.

Toward the end of the article, after discussing all kinds of functional RNAs, he brings up the Ponting and Haerty review where they say that most lncRNAs are just noise. He also mentions that the low copy number of non-coding RNAs raises questions about whether they are functional but immediately counters with the standard excuses from his allies.

Ball closes the article with ...

Gingeras says he is perplexed by ongoing claims that ncRNAs are merely noise or junk, as evidence is mounting that they do many things. "It is puzzling why there is such an effort to persuade colleagues to move from a sense of interest and curiosity in the ncRNA field to a more dubious and critical one," he says.

Perhaps the arguments are so intense because they undercut the way we think our biology works. Ever since the epochal discovery about DNA's double helix and how it encodes information, the bedrock idea of molecular biology has been that there are precisely encoded instructions that program specific molecules for particular tasks. But ncRNAs seem to point to a fuzzier, more collective, logic to life. It is a logic that is harder to discern and harder to understand. ut if scientists can learn to live with the fuzziness, this view of life may turn out to be more complete.

What's remarkable about the quote from a leading ENCODE worker (Gingeras) is that he is "puzzled" by scientists who are dubious and critical about claims in the ncRNA field. Isn't that what good scientists are supposed to do? Isn't that exactly what we did when we successfully challenged the dubious claims about junk DNA made in 2012?

There is no doubt in my mind that Philip Ball has fallen hook-line-and-sinker for the ENCODE claims that our genome is buzzing with non-coding genes. He only brings up the counter-arguments to dismiss them and pretend that he is being fair. Nobody who was truly skeptical about the function of transcripts would write an article with the title, "Revolutionary Genetics Research Shows RNA May Rule Our Genome."

However, as Ball points out in other comments, he does have a sentence in his book where he mentions that perhaps only 30% of the genome is functional. He says in the comment that what he believes is that the amount of functional DNA lies somewhere between 10% and 30%. That's not something that he mentions in the Scientific American article but, if he's being honest, it does mean that I was unfair when I said he believes that "almost of all of those transcripts are functional" but I only know that from what he now says, not from the published article.

If I were to take Philip Ball at his word—as expressed in the comment—then he must believe that most of the ENCODE transcripts are junk RNA. That's not a belief that you get from reading his published work.2 Furthermore, if I were to take him at his word, then he must believe that there are some reasonable criteria that must be applied to a transcript in order to decide whether it has a biologically relevant function. So, when he says that ENCODE identified 37,600 non-coding genes he must have these criteria in mind but he doesn't express any serious skepticism about that number. We all know that there's no solid evidence that such a large number of transcripts are functional but that doesn't bother Philip Ball. He thinks we are in the middle of an RNA revolution.


1. In commenting to my previous post, Ball says he believes that somewhere between 70% and 90% of our genome is junk but he doesn't say this in the Scientific American article. Instead, he says that scientists were surprised to learn that 75% of the human genome is transcribed implying that there's a lot of function. He goes on the say that "ENCODE was basically right." But what the ENCODE publicity campaign actually said was that junk DNA is dead and there's practically no junk DNA. If Ball really believes that up to 90% of the genome is junk then to me this means that ENCODE was spectacularly wrong not "basically right."

2. Ball says that 75% of the genome is transcribed. If Ball believes that as little as 10% may be functional then he must believe that less than 10% is transcribed to produce functional RNAs since he has to allow for regulatory sequences and other functional DNA elements. Let's say that 8% is a reasonable number. Ball seems to be willing to admit that 67% of the genome might be transcribed to produce junk RNA.

Wednesday, October 16, 2024

Nobel Laureates Michael Brown and Joseph Goldstein


The Nobel Prize in Physiology or Medicine 1985
"for their discoveries concerning the regulation of cholesterol metabolism"

Michael S. Brown and Joseph L.Goldstein won the Nobel Prize in 1985 for discovering the low-density lipoprotein (LDL) receptor, a cell surface protein that binds lipid-protein complexes containing cholesterol. (See Monday's Molecule #243.)

Here's part of the Press Release.

THEME:
Nobel Laureates

Michael S. Brown and Joseph L. Goldstein have through their discoveries revolutionized our knowledge about the regulation of cholesterol metabolism and the treatment of diseases caused by abnormally elevated cholesterol levels in the blood. They found that cells on their surfaces have receptors which mediate the uptake of the cholesterol-containing particles called low-density lipoprotein (LDL) that circulate in the blood stream. Brown and Goldstein have discovered that the underlying mechanism to the severe hereditary familial hypercholesterolemia is a complete, or partial, lack of functional LDL-receptors. In normal individuals the uptake of dietary cholesterol inhibits the cells own synthesis of cholesterol. As a consequence the number of LDL-receptors on the cell surface is reduced. This leads to increased levels of cholesterol in the blood which subsequently may accumulate in the wall of arteries causing atherosclerosis and eventually a heart attack or a stroke. Brown and Goldstein’s discoveries have lead to new principles for treatment, and prevention, of atherosclerosis.



The images of the Nobel Prize medals are registered trademarks of the Nobel Foundation (© The Nobel Foundation). They are used here, with permission, for educational purposes only.

Monday, October 14, 2024

Monday's Molecule #243

Today's molecule is quite complicated. It's the extracellular domain of a membrane protein.2 You can use whatever tricks you want to identify it. Regular readers will know that it's related to at least one Nobel Prize Laureate who will be revealed on Wednesday. I don't think that's going to help you very much.

Email your answer to me at: Monday's Molecule #242. 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 coffee and donut at Tim Hortons if you are ever in Toronto or Mississauga (Ontario, Canada).1

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.)

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

Comments are closed for at least 24 hours.

UPDATE: The winner is Mikkel Rasmussen who correctly guessed that the protein is the extracellular domain of the low-density lipoprotein (LDL) receptor. Sadly, Mikkel lives in a faraway country that doesn't have a Tim Hortons so he won't get to enjoy a honey cruller or chocolate dip donut.

Winners

#145, Oct. 17, 2011: Bill Chaney, Roger Fan
#146, Oct. 24, 2011: DK
#147, Oct. 31, 2011: Joseph C. Somody
#148, Nov. 7, 2011: Jason Oakley
#149, Nov. 15, 2011: Thomas Ferraro, Vipulan Vigneswaran
#150, Nov. 21, 2011: Vipulan Vigneswaran (honorary mention to Raul A. Félix de Sousa)
#151, Nov. 28, 2011: Philip Rodger
#152, Dec. 5, 2011: 凌嘉誠 (Alex Ling)
#153, Dec. 12, 2011: Bill Chaney
#154, Dec. 19, 2011: Joseph C. Somody
#155, Jan. 9, 2012: Dima Klenchin
#156, Jan. 23, 2012: David Schuller
#157, Jan. 30, 2012: Peter Monaghan
#158, Feb. 7, 2012: Thomas Ferraro, Charles Motraghi
#159, Feb. 13, 2012: Joseph C. Somody
#160, March 5, 2012: Albi Celaj
#161, March 12, 2012: Bill Chaney, Raul A. Félix de Sousa
#162, March 19, 2012: no winner
#163, March 26, 2012: John Runnels, Raul A. Félix de Sousa
#164, April 2, 2012: Sean Ridout
#165, April 9, 2012: no winner
#166, April 16, 2012: Raul A. Félix de Sousa
#167, April 23, 2012: Dima Klenchin, Deena Allan
#168, April 30, 2012: Sean Ridout
#169, May 7, 2012: Matt McFarlane
#170, May 14, 2012: no winner
#171, May 21, 2012: no winner
#172, May 29, 2012: Mike Hamilton, Dmitri Tchigvintsev
#173, June 4, 2012: Bill Chaney, Matt McFarlane
#174, June 18, 2012: Raul A. Félix de Sousa
#175, June 25, 2012: Raul A. Félix de Sousa
#176, July 2, 2012: Raul A. Félix de Sousa
#177, July 16, 2012: Sean Ridout, William Grecia
#178, July 23, 2012: Raul A. Félix de Sousa
#179, July 30, 2012: Bill Chaney and Raul A. Félix de Sousa
#180, Aug. 7, 2012: Raul A. Félix de Sousa
#181, Aug. 13, 2012: Matt McFarlane
#182, Aug. 20, 2012: Stephen Spiro
#183, Aug. 27, 2012: Raul A. Félix de Sousa
#184, Sept. 3, 2012: Matt McFarlane
#185, Sept. 10, 2012: Matt Talarico
#186, Sept. 17, 2012: no winner
#187, Sept. 24, 2012: Mikkel Rasmussen
#188, Oct. 1, 2012: John Runnels
#189, Oct. 8, 2012: Raúl Mancera
#190, Oct. 15, 2012: Raul A. Félix de Sousa
#191, Oct. 22, 2012: Mikkel Rasmussen
#192, Nov. 12, 2012: Seth Kasowitz, Bill Gunn
#193, Nov. 19, 2012: Michael Rasmussen
#194, Dec. 4, 2012: Paul Clapham, Jacob Toth
#195, Dec. 10, 2012: Jacob Toth
#196, Dec. 17, 2012: Bill Chaney, Dima Klenchin, Bill Gunn
#197, Jan. 14, 2013: Evey Salara
#198, Jan. 21, 2013: Piotr Gasiorowski
#199, March 11, 2013: Bill Gunn, River Jiang
#200, March 18, 2013: Bill Gunn
#201, April 8, 2013: Michael Florea
#202, April 15, 2013: no winner
#203, April 29, 2013: Anders Ernberg
#204, May 6, 2013: Alex Ling, Michael Florea
#205, May 13, 2013: Bill Chaney
#206, June 24, 2013: Michael Florea
#207, July 2, 2013: Matt McFarlane
#208, July 8, 2013: no winner
#209, July 15, 2013: Rosie Redfield, Thuc Quyen Huynh
#210, July 22, 2013: Jacob Toth
#211, July 29, 2013: Alex Ling, Matt McFarlane
#212, August 5, 2013: Brian Shewchuk
#213, Sept. 2, 2013: no winner
#214, Sept. 9, 2013: Bill Chaney
#215, Sept. 16, 2013: Zhimeng Yu
#216, Sept. 23, 2013: Mark Sturtevant, Jacob Toth
#217, Sept. 30, 2013: Susan Heaphy
#218, Oct. 7, 2013: Piotr Gasiorowski, Jacob Troth
#219, Oct. 14, 2013: Jean-Marc Neuhaus
#220, Oct. 21, 2013: Jean-Marc Neuhaus
#221, Oct. 28, 2013: Zhimeng Yu
#222, Nov. 10, 2013: Caroline Josefsson, Andrew Wallace
#223, Nov. 18, 2013: Dean Bruce, Ariel Gershon
#224, Nov. 25, 2013: Jon Nuelle, Ariel Gershon
#225, Dec. 2, 2013: Jean-Marc Neuhaus
#226, Dec. 9, 2013: Bill Gunn
#227, Dec. 16, 2013: Piotr Gasiorowski
#228, Jan. 13, 2014: Tom Mueller
#229, Jan. 20, 2014: Tommy Stuleanu
#230, Jan. 27, 2014: Bill Gunn, Ariel Gershon
#231; March 3, 2014: Keith Conover, Nevraj Kejiou
#232, March 10, 2014: Philip Johnson
#233, March 17, 2014: Jean-Marc Neuhaus
#234, March 24, 2014: Frank Schmidt, Raul Félix de Sousa
#235, March 31, 2014: Jon Binkley
#236, April 7, 2014: no winner
#237, April 21, 2014: Dean Bruce
#238, April 28, 2014: Dean Bruce
#239, May 5, 2014: Piotr Gąsiorowski
#240, May 12, 2014: James Wagstaff
#241, May 19, 2014: no winner
#242, Oct. 7, 2024: Elie Huvier
#243, Oct. 14, 2024: Mikkel Rasmussen

1. I still owe some previous winners. If you are one of them, then you should email me to set up a time and place.

2. The figure is from Rudenko, G., Henry, L., Henderson, K., Ichtchenko, K., Brown, M. S., Goldstein, J. L., and Deisenhofer, J. (2002) Structure of the LDL receptor extracellular domain at endosomal pH. Science, 298(5602), 2353-2358. [doi: 10.1126/science.1078124


Friday, October 11, 2024

Philip Ball says RNA may rule our genome

Philip Ball is on a roll. He has published a new book plus several articles in popular magazines and he has appeared in a bunch of podcasts and YouTube videos. The message is all the same, he claims that it's time for a revolution in biology.

Ball's ideas are complicated and I won't go into all of them in this article. Instead, I want to focus on one of his more scientific claims; namely, the claim that genomic data has overthrown the fundamental principles of molecular biology. Let's look at his recent (May 14, 2024) article in Scientific American: Revolutionary Genetics Research Shows RNA May Rule Our Genome.1

The subtile of the article is "Scientists have recently discovered thousands of active RNA molecules that can control the human body" and that's the issue that I want to discuss here.

Wednesday, October 09, 2024

Nobel Laureate: Aziz Sancar


The Nobel Prize in Chemistry 2015.

“for mechanistic studies of DNA repair”



Aziz Sancar won the 2015 Nobel Prize in Chemistry for his contributions to the study of DNA repair.

Sancar was born in Turkey in 1946 and got his MD degree from the Faculty of Medicine of Istanbul University. He then went on to get a Ph.D. with Claud S. Rupert at the University of Texas at Dallas in 1977. The Rupert lab worked on DNA repair and Sancar's thesis topic was the photoreactivating enzyme in E. coli. The photoreactivating enzyme was an enzyme that repaired DNA damage.

Sancar eventually secured a position at the University of North Carolina, Chapel Hill where he worked on excision repair and on photoreactivation. He is best known for his study of the mechanism of photolyase, the enzyme that repairs thymine dimers. [see Monday's Molecule #242] Photolyases are present in bacteria, protozoa, fungi, plants, and most animals. The gene for photolyase has been lost in placental mammals.

The information on the Nobel Prize website describes the career of Aziz Sancar.

THEME:
Nobel Laureates

Aziz Sancar’s fascination with life’s molecules developed while he was studying for a medical degree in Istanbul. After graduating, he worked for a few years as phycisian in the Turkish countryside, but in 1973 he decided to study biochemistry. His interest was piqued by one phenomenon in particular: when bacteria are exposed to deadly doses of UV radiation, they can suddenly recover if they are illuminated with visible blue light. Sancar was curious about this almost magical effect; how did it function chemically?

Claud Rupert, an American, had studied this phenomenon and Aziz Sancar joined his laboratory at the University of Texas in Dallas, USA. In 1976, using that time’s blunt tools for molecular biology, he succeeded in cloning the gene for the enzyme that repairs UV-damaged DNA, photolyase, and also in getting bacteria to over-produce the enzyme. This work became a doctoral dissertation, but people were hardly impressed; three applications for postdoc positions resulted in as many rejections. His studies of photolyase had to be shelved. In order to continue working on DNA repair, Aziz Sancar took up a position as laboratory technician at the Yale University School of Medicine, a leading institution in the field. Here he started the work that would eventually result in the Nobel Prize in Chemistry.

By then it was clear that bacteria have two systems for repairing UV damage: in addition to light-dependent photolyase, a second system that functions in the dark had been discovered. Aziz Sancar’s new colleagues at Yale had studied this dark system since the mid-1960s, using three UV-sensitive strains of bacteria that carried three different genetic mutations: uvrA, uvrB and uvrC.

As in his previous studies of photolyase, Sancar began investigating the molecular machinery of the dark system. Within a few years he had managed to identify, isolate and characterise the enzymes coded by the genes uvrA, uvrB and uvrC. In ground-breaking in vitro experiments he showed that these enzymes can identify a UV-damage, then making two incisions in the DNA strand, one on each side of the damaged part. A fragment of 12-13 nucleotides, including the injury, is then removed.

Aziz Sancar’s ability to generate knowledge about the molecular details of the process changed the entire research field. He published his findings in 1983. His achievements led to an offer of an associate professorship in biochemistry at the University of North Carolina at Chapel Hill. There, and with the same precision, he mapped the next stages of nucleotide excision repair. In parallel with other researchers, including Tomas Lindahl, Sancar investigated nucleotide excision repair in humans. The molecular machinery that excises UV damage from human DNA is more complex than its bacterial counterpart but, in chemical terms, nucleotide excision repair functions similarly in all organisms.

So, what happened to Sancar’s initial interest in photolyase? Well, he eventually returned to this enzyme, uncovering the mechanism responsible for reviving the bacteria. In addition, he helped to demonstrate that a human equivalent to photolyase helps us set the circadian clock.



The images of the Nobel Prize medals are registered trademarks of the Nobel Foundation (© The Nobel Foundation). They are used here, with permission, for educational purposes only.

Monday, October 07, 2024

Monday's Molecule #242

It's been a while since the last Monday's Molecule on May 19, 2014 but I think it's time to revive that tradition. I'll show you a molecule and you have to guess what it is without searching the internet. In other words, you have to recognize it immediately or it doesn't count. Email your answer to me at: Monday's Molecule #242. 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 coffee and donut at Tim Hortons if you are ever in Toronto or Mississauga (Ontario, Canada).1

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.)

Today's molecule (right) looks very complicated but I'm not going to ask you to give me a complete chemical name. The simple common name will do but you have to briefly explain it's biological significance and why it's always discussed in biochemistry textbooks.

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

Comments are closed for at least 24 hours.

UPDATE: The winner is Elie Huvier who pointed out that the molecule is a thymine dimer with a cyclobutane ring. Thymine dimers are mutations caused by ultraviolet light, which causes photodimerization of adjacent stacked pyrimidines in DNA. Elie Huvier was the first one to identify the molecule and describe its significance.

Winners

#145, Oct. 17, 2011: Bill Chaney, Roger Fan
#146, Oct. 24, 2011: DK
#147, Oct. 31, 2011: Joseph C. Somody
#148, Nov. 7, 2011: Jason Oakley
#149, Nov. 15, 2011: Thomas Ferraro, Vipulan Vigneswaran
#150, Nov. 21, 2011: Vipulan Vigneswaran (honorary mention to Raul A. Félix de Sousa)
#151, Nov. 28, 2011: Philip Rodger
#152, Dec. 5, 2011: 凌嘉誠 (Alex Ling)
#153, Dec. 12, 2011: Bill Chaney
#154, Dec. 19, 2011: Joseph C. Somody
#155, Jan. 9, 2012: Dima Klenchin
#156, Jan. 23, 2012: David Schuller
#157, Jan. 30, 2012: Peter Monaghan
#158, Feb. 7, 2012: Thomas Ferraro, Charles Motraghi
#159, Feb. 13, 2012: Joseph C. Somody
#160, March 5, 2012: Albi Celaj
#161, March 12, 2012: Bill Chaney, Raul A. Félix de Sousa
#162, March 19, 2012: no winner
#163, March 26, 2012: John Runnels, Raul A. Félix de Sousa
#164, April 2, 2012: Sean Ridout
#165, April 9, 2012: no winner
#166, April 16, 2012: Raul A. Félix de Sousa
#167, April 23, 2012: Dima Klenchin, Deena Allan
#168, April 30, 2012: Sean Ridout
#169, May 7, 2012: Matt McFarlane
#170, May 14, 2012: no winner
#171, May 21, 2012: no winner
#172, May 29, 2012: Mike Hamilton, Dmitri Tchigvintsev
#173, June 4, 2012: Bill Chaney, Matt McFarlane
#174, June 18, 2012: Raul A. Félix de Sousa
#175, June 25, 2012: Raul A. Félix de Sousa
#176, July 2, 2012: Raul A. Félix de Sousa
#177, July 16, 2012: Sean Ridout, William Grecia
#178, July 23, 2012: Raul A. Félix de Sousa
#179, July 30, 2012: Bill Chaney and Raul A. Félix de Sousa
#180, Aug. 7, 2012: Raul A. Félix de Sousa
#181, Aug. 13, 2012: Matt McFarlane
#182, Aug. 20, 2012: Stephen Spiro
#183, Aug. 27, 2012: Raul A. Félix de Sousa
#184, Sept. 3, 2012: Matt McFarlane
#185, Sept. 10, 2012: Matt Talarico
#186, Sept. 17, 2012: no winner
#187, Sept. 24, 2012: Mikkel Rasmussen
#188, Oct. 1, 2012: John Runnels
#189, Oct. 8, 2012: Raúl Mancera
#190, Oct. 15, 2012: Raul A. Félix de Sousa
#191, Oct. 22, 2012: Mikkel Rasmussen
#192, Nov. 12, 2012: Seth Kasowitz, Bill Gunn
#193, Nov. 19, 2012: Michael Rasmussen
#194, Dec. 4, 2012: Paul Clapham, Jacob Toth
#195, Dec. 10, 2012: Jacob Toth
#196, Dec. 17, 2012: Bill Chaney, Dima Klenchin, Bill Gunn
#197, Jan. 14, 2013: Evey Salara
#198, Jan. 21, 2013: Piotr Gasiorowski
#199, March 11, 2013: Bill Gunn, River Jiang
#200, March 18, 2013: Bill Gunn
#201, April 8, 2013: Michael Florea
#202, April 15, 2013: no winner
#203, April 29, 2013: Anders Ernberg
#204, May 6, 2013: Alex Ling, Michael Florea
#205, May 13, 2013: Bill Chaney
#206, June 24, 2013: Michael Florea
#207, July 2, 2013: Matt McFarlane
#208, July 8, 2013: no winner
#209, July 15, 2013: Rosie Redfield, Thuc Quyen Huynh
#210, July 22, 2013: Jacob Toth
#211, July 29, 2013: Alex Ling, Matt McFarlane
#212, August 5, 2013: Brian Shewchuk
#213, Sept. 2, 2013: no winner
#214, Sept. 9, 2013: Bill Chaney
#215, Sept. 16, 2013: Zhimeng Yu
#216, Sept. 23, 2013: Mark Sturtevant, Jacob Toth
#217, Sept. 30, 2013: Susan Heaphy
#218, Oct. 7, 2013: Piotr Gasiorowski, Jacob Troth
#219, Oct. 14, 2013: Jean-Marc Neuhaus
#220, Oct. 21, 2013: Jean-Marc Neuhaus
#221, Oct. 28, 2013: Zhimeng Yu
#222, Nov. 10, 2013: Caroline Josefsson, Andrew Wallace
#223, Nov. 18, 2013: Dean Bruce, Ariel Gershon
#224, Nov. 25, 2013: Jon Nuelle, Ariel Gershon
#225, Dec. 2, 2013: Jean-Marc Neuhaus
#226, Dec. 9, 2013: Bill Gunn
#227, Dec. 16, 2013: Piotr Gasiorowski
#228, Jan. 13, 2014: Tom Mueller
#229, Jan. 20, 2014: Tommy Stuleanu
#230, Jan. 27, 2014: Bill Gunn, Ariel Gershon
#231; March 3, 2014: Keith Conover, Nevraj Kejiou
#232, March 10, 2014: Philip Johnson
#233, March 17, 2014: Jean-Marc Neuhaus
#234, March 24, 2014: Frank Schmidt, Raul Félix de Sousa
#235, March 31, 2014: Jon Binkley
#236, April 7, 2014: no winner
#237, April 21, 2014: Dean Bruce
#238, April 28, 2014: Dean Bruce
#239, May 5, 2014: Piotr Gąsiorowski
#240, May 12, 2014: James Wagstaff
#241, May 19, 2014: no winner
#242, Oct. 7, 2024: Elie Huvier

1. I still owe some previous winners. If you are one of them, then you should email me to set up a time and place.

Thursday, October 03, 2024

Intelligent Design Creationists made up a fake march of progress illustration

Everyone is familiar with the typical March of Progress figures that are often used to illustrate evolution. However, most people don't know that evolutionary biologists object to that depiction of evolution because it seriously misrepresents the reality of human evolution.

Stephen Jay Gould has been one of the most vocal opponents of such icons because they imply a sense of direct linear progress from some primitive ancestor to a modern species when, in fact, the actual evolution involves branching trees with multiple lineages, most of which have gone extinct. In one of his most famous essays, Life's Little Joke (Gould, 1987, 1991), Gould explains why the evolution of horses is falsely depicted as a march of progress.

Tuesday, October 01, 2024

Jonathan Wells (1942 - 2024)

Johnathan Wells died recently. He was a well-known Intelligent Design Creationist and that's why Evolution News (sic) is eulogizing him by posting multiple tributes and excerpts from his books and essays.

I think it's only fair to post links to my efforts to demonstrate the serious flaws in his arguments. I'm particularly proud of the series of articles I wrote when he published his book The Myth of Junk DNA. I went through every chapter and analyzed his arguments against junk DNA. It won't surprise anyone to learn that I found those arguments lacking in substance and in some cases I discovered that Wells had misrepresented the science.

Here are my posts.

Jonathan Wells never responded directly to my criticism but he did respond to a comment that Paul McBride made on one of his blog posts. Paul asked him why he didn't respond to my post and here's what Wells said,

Oh, one last thing: “paulmc” referred to an online review of my book by University of Toronto professor Larry Moran—a review that “paulmc” called both extensive and thorough. Well, saturation bombing is extensive and thorough, too. Although “paulmc” admitted to not having read more than the Preface to The Myth of Junk DNA, I have read Mr. Moran’s review, which is so driven by confused thinking and malicious misrepresentations of my work—not to mention personal insults—that addressing it would be like trying to reason with a lynch mob.

This is typical of the attitude of most Intelligent Design Creationists. They are happy to publish lengthy books denegrating science and scientists but couldn't be bothered responding to criticism.

Here's are some other post of mine where I demonstrate the flawed thinking of Jonathan Wells.

Friday, September 27, 2024

John Mattick's seminar at the University of Toronto

I just learned that John Mattick gave a seminar this morning at the Department of Cell & Systems Biology at the University of Toronto. Unfortunately, I was unable to attend.

Most Sandwalk readers will recognize Mattick as one of the few remaining vocal opponents of junk DNA. He is probably best known for his dog-ass plot but this is only one of the ways he misrepresents science.

Tuesday, September 24, 2024

On the evolution of the glycolytic pathway (glycolysis)

Jonathan McLatchie has a PhD in Evolutionary Biology from Newcastle University (UK) and he is currently "resident biologist" and a fellow at the Center for Science and Culture at the Discovery Institute. He is an intelligent design creationist who attacks evolution by questioning standard explanations in the fields of biochemistry and molecular biology.

I've debated him frequently over the years since those are my areas of interest as well. The last time we met was at an evolution conference in London (UK) in 2016 (see photo).

I've always found Jonathan to be more honest and more willing to learn than most of his creationist colleagues so that's why I'm addressing his latest post on Evolution News (sic) where he challenges the evolutionary origins of the glycolytic pathway. As you might expect, his argument is largely based on the idea that since the glycolytic pathway is very complicated, there's no way it could have arisen all at once. He then goes on to reject the idea that the pathway could have evolved incrementally, one step at a time.

Friday, September 20, 2024

Should Scientific American endorse United States political candidates?

Scientific American has endorsed Kamala Harris, a candidate for president of the United States. I think this is a mistake and so do many other scientists and even journalists [Scientific American Didn’t Need to Endorse Anybody].

I agree with those who say that science should stay out of politics as much as possible. But this is just one of many indications that Scientific American is sliding rapidly downhill and no longer qualifies as a real science magazine.


Monday, September 09, 2024

The DNA papers

The DNA papers is a series of podcasts on the discovery that DNA is the source of genetic information. Each podcast is a discussion among experts on the history of molecular biology, including some who have been regularly featured on this blog. I draw your attention to episodes 6 and 15 where you can hear Matt Meselson one of the key figures in the 'phage group.

The key take-home lesson is that the importance of DNA was recognized by a small group of scientists who were paying attention to the scientific literature. By the time of Watson and Crick (1953) this small group was already convinced that DNA was the "stuff of life," which is why they realized that solving the structure was extremely important.

This is not unusual. There are many cases where a small group of knowledgeable experts are well in advance of the average scientist who often doesn't even realize that a revolution is under way.

  • Episode 1 on Friedrich Miescher and the discovery of nuclein
  • Episode 2 on Albrecht Kossel and the discovery of the building blocks of nuclein
  • Episode 3 on Walter Sutton and the relation between chromosomes and heredity
  • Episode 4 on Fred Griffith and the discovery of bacterial transformation/li>
  • Episode 5 on Phoebus Levene, DNA chemistry and the tetranucleotide hypothesis
  • Episode 6 on William Astbury, Florence Bell and the first X-ray pictures of DNA
  • Episode 7 on Oswald Avery, Colin McLeod, and Maclyn McCarty and the chemical basis of bacterial transformation
  • Episode 8 on Maclyn McCarty, Oswald Avery and the enzymatic evidence for DNA as the transforming substance
  • Episode 9 on Erwin Chargaff and the evidence for non-uniformity of nucleotide base composition in DNA
  • Episode 10 on Harriet Ephrussi-Taylor, Rollin Hotchkiss and the demonstration of bacterial transformation as a general phenomenon
  • Episode 11 on Alfred Hershey, Martha Chase, and the conclusive evidence for the function of DNA as the material of heredity
  • Episode 12 on Maurice Wilkins, Rosalind Franklin, their collaborators, and the data that supported the double helix model for DNA structure
  • Episode 13 on James Watson, Francis Crick, and the DNA Double Helix
  • Episode 14 on Matthew Meselson, Franklin Stahl, and semiconservative replication of DNA
  • Episode 15 A conversation with Matthew Meselson and Franklin Stahl


Sunday, September 01, 2024

Scite Assistant (AI) answers the question "How much of the human genome consist of junk DNA?"

Scite Assistant is billed as "your AI research partner" and as "ChatGPT for researchers." It's supposed to draw on peer-reviewed published scientific papers for its information and it will give you an answer with genuine citations.

That sounds like a good idea until you realize that the scientific literature is full of misinformation and conflicting information. What we need is an AI assistant that can help us sort throught the misinformation and give us a genuine well-informed answer on controversial issues.

Let's pick the question of junk DNA as a completley random (!) example of such an issue. The scientific literature is full of false information about the origin of the term "junk DNA" and what it was originally intended to describe. It's also full of false information about recent results and how they pertain to junk DNA.