Left handed amino acids
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11-09-2015, 08:54 PM
RE: Left handed amino acids
(11-09-2015 08:51 PM)Ted Tucker Wrote:  New you had it under control. My iPad is also not playing well with the forum?? There is that spooky action thing...must be proof for the existence of God.

I go to do a link and the stupid thing freezes up. Fucking Apple crap. I'm on the PC in the living room now, so, no worries. And more information is always better. Thumbsup

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11-09-2015, 10:25 PM
RE: Left handed amino acids
(11-09-2015 07:44 PM)daniel1948 Wrote:  Amino acids can twist in one direction or the other.

This. It's a concept called "chirality", and it refers to the fact that two molecules can be created from the same atoms but be constructed in opposite ways, as if one is a mirrored reflection of the other - hence the right- versus left-handed concept. Your hands have all the same components of one another, but they are reflections rather than identical.

Because of the way chemistry works, molecules of opposite chiral orientations don't exactly play well together. Due to the way their opposite constructions interact, you won't find a biological organism with both right- and left-handed amino acids in their system. There are also other differences which are rather interesting; for example, some compounds smell or taste different depending on whether they are formed from right- or left-handed molecules.

It's basically just a fancy way of saying "molecules can be built of all the same atoms but put together differently, which means that they might react a little strangely when confronted with ones that aren't put together like they are".

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12-09-2015, 08:56 AM
RE: Left handed amino acids
(11-09-2015 08:06 PM)dancefortwo Wrote:  
(11-09-2015 07:44 PM)daniel1948 Wrote:  Amino acids can twist in one direction or the other. For some reason, all life on Earth is made of one version, never the other. The other versions can be found in nature, but never in living things. I don't think anybody knows why. Sometimes when you synthesize amino acids, you get both versions. But living things only make the one version. Again, I don't think anybody knows why. Yet. There are always new questions, and eventually someone finds an answer and they move on to other questions. This one remains a mystery for the time being.

Yeah, one of the reasons I ask is that someone I know claims it's a part of intelligent design. Hobo If it's a fuckin mystery then it must be fuckin god. Christ, people drive me crazy sometimes.

It's called the god of the gaps: If there's a gap in our scientific knowledge, then it must be God. Science is constantly closing gaps as it learns more and more, but our knowledge will never be complete, so there are always gaps to shove God into.

An easy way to counter such arguments is to insist on squeezing a different god into the same gap. "God didn't create chirality. It was the Loch Ness Monster that did it." Or: Space aliens didn't build the pyramids. The Loch Ness Monster built them, by telekinesis, without ever leaving her loch.

(I like Nessie, She's my favorite cryptid. It would be so cool if she was real.)

(11-09-2015 10:25 PM)Unbeliever Wrote:  ... some compounds smell or taste different depending on whether they are formed from right- or left-handed molecules.

I think that's how they make Sucralose. It's sucrose, but twisted the other way. Our tongue registers it as a thousand tines (?) as sweet as sucrose, so you get the same sweetness with a thousandth (?) the amount. (Not sure of the number, but it's big.)

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12-09-2015, 11:48 AM
RE: Left handed amino acids
Here is a Radio Lab discussing chirality with a few comments by Neil Degrasse Tyson and related information (if my memory serves me) on right handed thalidomide which was so devastating to the human fetus.

http://www.radiolab.org/story/122613-mirror-mirror/

Shakespeare's Comedy of Errors.... on Donald J. Trump:

He is deformed, crooked, old, and sere,
Ill-fac’d, worse bodied, shapeless every where;
Vicious, ungentle, foolish, blunt, unkind,
Stigmatical in making, worse in mind.
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12-09-2015, 01:14 PM
RE: Left handed amino acids
The left and right hands are mirror images that are not superposable, that is to say if you put both hands palms down and try to make the thumb on one hand occupy the same space as the thumb on the other hand, you can't. Mirror images that are not superposable are said to be chiral. Some molecules also have this property, that the mirror images of the molecules are not superposable. Non superposable mirror images of molecules are called enatiomers. For example, the amino acids (except glycine) and the example below, 2-butanol. The two mirror images of 2-butanol are enantiomers and each has a "handedness".

[Image: butanolMI.gif]

Proteins and enzymes in organisms are made all from the L-amino acids and are therefore chiral and would have a non superposable mirror image made from only D-amino acids. Enzymes typically only recognize a single enantiomer. For example, hexokinase, the first enzyme in the metabolism of glucose only catalyzes the reaction of D-glucose, not the enantiomer L-glucose. Different enantiomer can thus interact differently with biological systems. Advil is sold as a mixture of enantiomer in which one enantiomer is an analgesic, the other has no effect. Another example is that one enantiomer of limonene smells oranges, the other one like lemons. Lastly is the whole thalidomide issue in which one enantiomer relieves morning sickness, while the other one causes birth defects.

What is unknown is how living systems came to use only one enantiomer
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14-09-2015, 03:37 AM
RE: Left handed amino acids
In case this is not already crystal clear, here's an analogy:
Let's say you have an electric drill. The drill bit has a twist in it and the direction of the twist is the same as the direction the electric drill turns. Let's call a twist in one direction "left" and a twist in the other direction "right". A left-turning drill works with left-twisting drill bits and wouldn't work with right-twisting bits. Likewise a right-turning drill would only work with right-twisting drill bits.

Humans have standards for deciding which way the bits should be. Life has ancestry to decide much the same thing. In principle it doesn't matter whether life is left or right, but it is more efficient if all of life is left-twisting or that all of life is right-twisting. In our case life is left twisted. We left-twisted creatures are built with left-twisted molecules. When we die we are eaten by left-twisted creatures. Right-twisted creatures can't really develop because they wouldn't have anything to right-twisted to eat.

Give me your argument in the form of a published paper, and then we can start to talk.
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14-09-2015, 09:47 AM
RE: Left handed amino acids
(14-09-2015 03:37 AM)Hafnof Wrote:  In case this is not already crystal clear, here's an analogy:
Let's say you have an electric drill. The drill bit has a twist in it and the direction of the twist is the same as the direction the electric drill turns. Let's call a twist in one direction "left" and a twist in the other direction "right". A left-turning drill works with left-twisting drill bits and wouldn't work with right-twisting bits. Likewise a right-turning drill would only work with right-twisting drill bits.

Humans have standards for deciding which way the bits should be. Life has ancestry to decide much the same thing. In principle it doesn't matter whether life is left or right, but it is more efficient if all of life is left-twisting or that all of life is right-twisting. In our case life is left twisted. We left-twisted creatures are built with left-twisted molecules. When we die we are eaten by left-twisted creatures. Right-twisted creatures can't really develop because they wouldn't have anything to right-twisted to eat.

That's a great description. Thanks. As I recall from the Radio Lab program, Thalidomide was twisting right which causes birth defects. I need to recheck this though.

Of course, to crazy intelligent designer proponents this is god designed because, even without any proof.......it just is.

Shakespeare's Comedy of Errors.... on Donald J. Trump:

He is deformed, crooked, old, and sere,
Ill-fac’d, worse bodied, shapeless every where;
Vicious, ungentle, foolish, blunt, unkind,
Stigmatical in making, worse in mind.
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14-09-2015, 10:44 AM
RE: Left handed amino acids
I believe thalidomide is given as a 1:1 mixture of both enantiomers. This is most likely due to the fact that even if the one beneficial enantiomer were administered, it will racemize or be converted into a mixture of both enantiomers in the body. Although, this can happen with thalidomide (and Advil), it doesn't necessarily happen with all chiral drugs (or compounds). This racemization is a function of their structures (suffice it to say they have an acidic alpha-hydrogen on the chiral carbon...)
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14-09-2015, 10:48 AM
RE: Left handed amino acids
(14-09-2015 10:44 AM)Iñigo Wrote:  I believe thalidomide is given as a 1:1 mixture of both enantiomers. This is most likely due to the fact that even if the one beneficial enantiomer were administered, it will racemize or be converted into a mixture of both enantiomers in the body. Although, this can happen with thalidomide (and Advil), it doesn't necessarily happen with all chiral drugs (or compounds). This racemization is a function of their structures (suffice it to say they have an acidic alpha-hydrogen on the chiral carbon...)

I found this on a website.

"Thalidomide is a sedative drug that was prescribed to pregnant women, from 1957 into the early 60's. It was present in at least 46 countries under different brand names. "When taken during the first trimester of pregnancy, Thalidomide prevented the proper growth of the foetus, resulting in horrific birth defects in thousands of children around the world" [1]. Why? The Thalidomide molecule is chiral. There are left and right-handed Thalidomides, just as there are left and right hands. The drug that was marketed was a 50/50 mixture. One of the molecules, say the left one, was a sedative, whereas the right one was found later to cause foetal abnormalities. "The tragedy is claimed to have been entirely avoidable had the physiological properties of the individual thalidomide [molecules] been tested prior to commercialization [2]."

Shakespeare's Comedy of Errors.... on Donald J. Trump:

He is deformed, crooked, old, and sere,
Ill-fac’d, worse bodied, shapeless every where;
Vicious, ungentle, foolish, blunt, unkind,
Stigmatical in making, worse in mind.
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14-09-2015, 11:25 AM
RE: Left handed amino acids
Haf, I wanted to point out that your description is better suited for axial chirality which is a bit different. Your response implies that right drills will only work with left drills and that simply is not true in the context of a biological system. Small nitpick but an important one.

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