Chirality

[Perknose]

Did you know that:

All living molecules are left handed.

But that we can flip these molecules to become right handed in the lab.

That Thalidomide, the drug that hideously deformed so many babies in the sixties, was originally totally benign but was flipped in the lab to right handedness.

That a guy changed his life and how people reacted to him by changing which side he parted his hair on. That this same guy noticed President Jimmy Carter was parting his hair on the "wrong" side, sent him a letter, and that six or so weeks later Carter changed his part side?

That Superman is always shown with his hair parted on the "right" side, but that Clark Kent is always shown with his hair parted on the "wrong" side . . . and that, in a clip showing Kent ripping off his clothes as he runs down the street and changed into S-Man, the part on his hair magically changes?

You do now. Listen up and learn, troop: Desperately Seeking Symmetry.

 

[Special K]

I saw the title of your thread and immediately thought of the Radiolab episode of the same name. I then clicked the thread and it confirmed my hunch.

The more recent Radiolab episodes haven't been up their usual standard of quality, and they have started to venture somewhat far from their original focus on science-related topics. That said, Radiolab is probably still one of the best podcasts available.

 

[MongGrel]

:hmm:

 

[Brainonska511]

You also can't really "flip" proteins in the lab. It's pretty much impossible. However, you can make mirror-image amino acids (the building blocks of proteins), then make a mirror image protein using synthetic means. I used to do it in my old research lab. It's quite neat - you can see cool effects like circular dichroism signals that are opposite in sign relative to the native form. You can also make D enzymes that will work on the mirror image substrate of the native form. Quite cool.

And amino acids used in proteins are "L", but you'll find some "D" amino acids in bacterial cell walls and other natural products. Sugars are also not the same handedness - they're generally "D". So I don't think I'd characterize "biological molecules" as having some universal handedness. But there are certain rules that are universal (eg: natural proteins are always made of only "L" amino acids).

And the story behind thalidomide - it isn't that it was flipped in the lab. It's an enantiomer. When it is synthesized, unless you make it in a stereospecific way, you'll get both variants. In this case, one of the enantiomers is the sedative, one is the teratogenic variant. It also doesn't matter if you purify only the good one, as it can racemize (switch between the enantiomers) in vivo.

 

[destrekor]

Molecules are alive?

You mean to say most biologically important molecules are left-handed?

There is one major exception to that: we can only digest right-handed sugars.


Chirality is awesome, and is especially interesting when the concept of enantiomerism plays into how different drugs perform in the body. Racemic compounds (containing both enantiomers, that is, the two mirror image chiral counterparts) can see the two versions actually modulate the total effects, and one or the other taken alone can produce effects that can be more pronounced and possibly different in comparison.

 

[Perknose]

You also can't really "flip" proteins in the lab. It's pretty much impossible. However, you can make mirror-image amino acids (the building blocks of proteins), then make a mirror image protein using synthetic means. I used to do it in my old research lab. It's quite neat - you can see cool effects like circular dichroism signals that are opposite in sign relative to the native form. You can also make D enzymes that will work on the mirror image substrate of the native form. Quite cool.

And amino acids are "L", but sugars are generally "D". However, you'll also see "D" amino acids in some parts of biology, like bacterial cell walls (but as far as I know, there are no "D" proteins in living systems). So there is a general handedness in biological molecules, but there are a lot of exceptions.

And the story behind thalidomide - it isn't that it was flipped in the lab. It's an enantiomer. When it is synthesized, unless you make it in a stereospecific way, you'll get both variants. In this case, one of the enantiomers is the sedative, one is the teratogenic variant. It also doesn't matter if you purify only the good one, as it can racemize (switch between the enantiomers) in vivo.

Thanks for that. :thumbsup:

All I did was listen to an "interesting science for the masses" radio program.

Saaaay, you seem to possess high levels of smartness. Would you help us all out and "teach the controversy" between young earth yahoos and, uhhhhh, the rest of us?

Two things I specifically want to know: Which dinosaurs got on the ark with Noah? And, is that whole evolution conspiracy linked to the same cabal that promotes climate change? :awe:

 

[destrekor]

You also can't really "flip" proteins in the lab. It's pretty much impossible. However, you can make mirror-image amino acids (the building blocks of proteins), then make a mirror image protein using synthetic means. I used to do it in my old research lab. It's quite neat - you can see cool effects like circular dichroism signals that are opposite in sign relative to the native form. You can also make D enzymes that will work on the mirror image substrate of the native form. Quite cool.

And amino acids are "L", but sugars are generally "D". However, you'll also see "D" amino acids in some parts of biology, like bacterial cell walls (but as far as I know, there are no "D" proteins in living systems). So there is a general handedness in biological molecules, but there are a lot of exceptions.

And the story behind thalidomide - it isn't that it was flipped in the lab. It's an enantiomer. When it is synthesized, unless you make it in a stereospecific way, you'll get both variants. In this case, one of the enantiomers is the sedative, one is the teratogenic variant. It also doesn't matter if you purify only the good one, as it can racemize (switch between the enantiomers) in vivo.

Sounds like you would obviously know, but I thought I'd add to your explanation:

Amino acids and proteins can have mirror image variants, but as you said, you can't simply "flip" the molecules because the mirror image cannot be superimposed, as the structure is inherently different. The molecules aren't simply rotated in 3D space, but different at the atomic structure.

 

[destrekor]

Saaaay, you seem to possess high levels of smartness. Would you help us all out and "teach the controversy" between young earth yahoos and, uhhhhh, the rest of us?

Two things I specifically want to know: Which dinosaurs got on the ark with Noah? And, is that whole evolution conspiracy linked to the same cabal that promotes climate change? :awe:

:biggrin: :awe:

 

[Mixolydian]

Yes I am aware of chirality.

 

[Brainonska511]

Sounds like you would obviously know, but I thought I'd add to your explanation:

Amino acids and proteins can have mirror image variants, but as you said, you can't simply "flip" the molecules because the mirror image cannot be superimposed, as the structure is inherently different. The molecules aren't simply rotated in 3D space, but different at the atomic structure.

Yeah, I'm a chemist/biophysicist. I meant you couldn't convert an "L" protein into a "D" protein by doing some sort of chemistry. A property of enantiomers is that they are not superimposable, no matter what rotation operations you try. They are, by definition, mirror images.

However, if you take a protein sequence of amino acids and make a protein out of D-amino acids, you'll get a mirror image protein.

 

[destrekor]

Yeah, I'm a chemist/biophysicist. I meant you couldn't convert an "L" protein into a "D" protein by doing some sort of chemistry. A property of enantiomers is that they are not superimposable, no matter what rotation operations you try. They are, by definition, mirror images.

However, if you take a protein sequence of amino acids and make a protein out of D-amino acids, you'll get a mirror image protein.

Are most amino acids and proteins levorotatory AND left-handed? I know that "L" and "D" variants aren't always associated with left vs right, so I'm genuinely curious if you may know that answer.
Or would it be more correct to say that all amino acids and thus the proteins are levorotatory, but not necessarily "left-handed" in terms of appearance?

And now I think my limited understanding of these things is just making it worse, so I'll let you clear up my babbling nonsense if it does indeed turn out to be such.

 

[Perknose]

Yes I am aware of chirality.

Whereas I, steeped in the quotidian ignorance of the great unwashed, did not.

But now, I, thanks to my life long quest to better myself intellectually and my opposable thumb, was able to operate my Marconi such that I now stand with you in the glorious light of higher awareness.

<-------- Looks at Mixo's brunch plate.

You gonna' finish that? :awe:

 

[Brainonska511]

Are most amino acids and proteins levorotatory AND left-handed? I know that "L" and "D" variants aren't always associated with left vs right, so I'm genuinely curious if you may know that answer.
Or would it be more correct to say that all amino acids and thus the proteins are levorotatory, but not necessarily "left-handed" in terms of appearance?

And now I think my limited understanding of these things is just making it worse, so I'll let you clear up my babbling nonsense if it does indeed turn out to be such.

All proteins are levorotary, as it's simply the way that they rotate plane polarized light. The confusion comes up when you start classifying amino acids by their chiral centers (as S or R) - almost all L amino acids are S, with some exceptions, like L-cysteine (which is R), and glycine, which is achiral. I wouldn't really be inclined to describe a protein as "left-handed", as they have 3 dimensional structures: secondary structural features such as alpha helices, which are "right-handed" and more complicated tertiary and quaternary structures.

 

[Mixolydian]

Whereas I, steeped in the quotidian ignorance of the great unwashed, did not.

But now, I, thanks to my life long quest to better myself intellectually and my opposable thumb, was able to operate my Marconi such that I now stand with you in the glorious light of higher awareness.

<-------- Looks at Mixo's brunch plate.

You gonna' finish that? :awe:

Are u ok? :hmm:

 

[destrekor]

All proteins are levorotary, as it's simply the way that they rotate plane polarized light. The confusion comes up when you start classifying amino acids by their chiral centers (as S or R) - almost all L amino acids are S, with some exceptions, like L-cysteine (which is R), and glycine, which is achiral. I wouldn't really be inclined to describe a protein as "left-handed", as they have 3 dimensional structures: secondary structural features such as alpha helices, which are "right-handed" and more complicated tertiary and quaternary structures.

That's where my brain sort of stopped trying when previously trying to understand the fullest implications of chirality. I remember the "S" and "R" designations as they relate to the chiral center, but actually understanding how that and how they rotated polarized light? I gave up there. I also recall cis- and trans-, at least in relation to fatty acids, and still then only enough to confuse others I reckon. As you see, you can tell a man's intellectual understanding of a subject by the ability to simplify the subject matter so that a pleb like me may better understand.

 

[Brainonska511]

That's where my brain sort of stopped trying when previously trying to understand the fullest implications of chirality. I remember the "S" and "R" designations as they relate to the chiral center, but actually understanding how that and how they rotated polarized light? I gave up there. I also recall cis- and trans-, at least in relation to fatty acids, and still then only enough to confuse others I reckon. As you see, you can tell a man's intellectual understanding of a subject by the ability to simplify the subject matter so that a pleb like me may better understand.

Plane polarized light:

One enantiomer rotates the polarization clockwise, the other rotates it counter clockwise and equal magnitude.

But, I guess I learn something new every day. Upon further looking, I wouldn't even say that proteins are "levarotary". I don't think many people are interested though in optical rotation properties of proteins. However, the main takeaway is that proteins are made up of amino acids that have the same configuration.

From Wiki's article on chirality:
"Rather, it says that the compound's stereochemistry is related to that of the dextrorotatory or levorotatory enantiomer of glyceraldehyde&#8212;the dextrorotatory isomer of glyceraldehyde is, in fact, the D- isomer. Nine of the nineteen L-amino acids commonly found in proteins are dextrorotatory (at a wavelength of 589 nm), and D-fructose is also referred to as levulose because it is levorotatory."

 

[MongGrel]

Two things I specifically want to know: Which dinosaurs got on the ark with Noah? And, is that whole evolution conspiracy linked to the same cabal that promotes climate change? :awe:

I think sharks and many things in general just kept swimming around going "SSDD"

()

 

[Perknose]

Whereas I, steeped in the quotidian ignorance of the great unwashed, did not.

But now, I, thanks to my life long quest to better myself intellectually and my opposable thumb, was able to operate my Marconi such that I now stand with you in the glorious light of higher awareness.

<-------- Looks at Mixo's brunch plate.

You gonna' finish that? :awe:

Are u ok? :hmm:

Such a deeply existential question! Hand over your brunch plate and I'll attempt to address it. :awe:

 

[brainhulk]

Because im a pharmacist and work mostly with levo enantiomers, are you suggesting i'm racist against dextro compounds? Because if you are, just come out and say it.


























I'm done here

 

[uclaLabrat]

Plane polarized light:

One enantiomer rotates the polarization clockwise, the other rotates it counter clockwise and equal magnitude.

But, I guess I learn something new every day. Upon further looking, I wouldn't even say that proteins are "levarotary". I don't think many people are interested though in optical rotation properties of proteins. However, the main takeaway is that proteins are made up of amino acids that have the same configuration.

From Wiki's article on chirality:
"Rather, it says that the compound's stereochemistry is related to that of the dextrorotatory or levorotatory enantiomer of glyceraldehyde—the dextrorotatory isomer of glyceraldehyde is, in fact, the D- isomer. Nine of the nineteen L-amino acids commonly found in proteins are dextrorotatory (at a wavelength of 589 nm), and D-fructose is also referred to as levulose because it is levorotatory."

Well thanks for making me review that, I had always thought that +/- corresponded to the D/L configuration and the two were related. I hate the way biochemists do chemistry. R/S is good enough for everyone, damnit!

 

[Gibsons]

You also can't really "flip" proteins in the lab. It's pretty much impossible. However, you can make mirror-image amino acids (the building blocks of proteins), then make a mirror image protein using synthetic means. I used to do it in my old research lab. It's quite neat - you can see cool effects like circular dichroism signals that are opposite in sign relative to the native form. You can also make D enzymes that will work on the mirror image substrate of the native form. Quite cool.

And amino acids used in proteins are "L", but you'll find some "D" amino acids in bacterial cell walls and other natural products. Sugars are also not the same handedness - they're generally "D". So I don't think I'd characterize "biological molecules" as having some universal handedness. But there are certain rules that are universal (eg: natural proteins are always made of only "L" amino acids).

Except glycine of course. :sneaky:

Also, DNA is mostly right handed.

 

[Ruptga]

Turn a right glove inside out and now it's a left glove, turn it inside out again and now it's a right glove. Magic.

 

[Perknose]

Turn a right glove inside out and now it's a left glove, turn it inside out again and now it's a right glove. Magic.

RTFT. You seem to have no idea how shallow and stupidly smug you sound.

 

[Ruptga]

RTFT. You seem to have no idea how shallow and stupidly smug you sound.

I did, and the same could be said for you though I don't know what that has to do with chirality.

 

[Perknose]

I did, and the same could be said for you though I don't know what that has to do with chirality.

You did read the thread, and you still posted your shallow, stupid, clueless, ignorant, way-off-the-mark magic glove analogy?

WOW. Way to completely own your dimbulb self there, Chief.

Try not to get any more on ya', k?