New Molecule With Switchable Chirality

Nanotechnology writes: "Available here, The molecule was developed by adding copper ions to a derivative of the amino acid methionine. The investigators were then able to switch the molecule's chirality by the addition or removal of an electron. Furthermore, they found that the molecule's chirality could be switched repeatedly, and that the two forms of the molecules polarized light in opposite directions." Especially interesting is this line from The Canary Lab's home page ("Research"): "We are also scrutinizing other aspects of signal detection technology. We prepared a new polymer very similar in structure to polyaniline ... The new polymer was designed to serve as a molecular wire for attaching electrochemical sensor molecules to electrodes."

Comments

Definition of "chiral"

[muldrake]

chiral
Definition:
A term used to describe a molecule which, in
a given configuration, cannot be superimposed
on its mirror image. This is in contrast to
achiral molecules which can be superimposed
on their mirror images. The two mirror image versions of
the molecule are known as "levo" (left-handed),
abbreviated "L," or "dextro" (right handed),
abbreviated "D," depending on which way they
rotate polarized light.

chiral compound
Definition:
A molecule that has an asymmetric center and can
be found in two non-superimposable mirror-image
forms (enantiomers).

Science and Biotechnology Dictionary

A Chiral compound is...

[mu_cow]

Simplistically a chiral compound is one which would appear different if viewed in a mirror. For example, your left hand cannot be imposed on top of your right hand as they are mirrors of each other. Your hands are chiral.

Biological molecules are (almost) always chiral and normally organisms can only cope with one version of a molecule and not its mirror.

Chiral molecules rotate plane polarised light. A molecule's mirror will rotate the light in the other direction. This is why they may have a use in "liquid crystal displays and non-linear optics".

Re:okay, so what?

[Anonymous Coward]

A chiral compound is one that is 'non-superimposable with its mirror image'. In other words, it can exist in 'right-handed' and 'left-handed' forms.

There are a variety of reasons for worrying about chirality. As mentioned, chiral molecules rotate the plane of polarised light. This can be used for display tech - imagine two polaroid filters paralell to each other, each polarising at a different angle. Light comes in, gets polarised by the first filter, and can't get through because its polarised at the wrong angle. Now stick a layer of your switchable-chiral molecule inbetweem the filters. If its in one form, then it rotates the polarisation of the polarised light to match the other filter, and light goes through. In the other form, it does it in the opposite direction, and the polarised light is at a different 'wrong' angle, and doesn't get through. Use lots of little bits of switchable compound, and you have a nice LCD-like display. You can do something similar with one filter and a mirror, too.

Or how about nanotech? Put electrons into/take electrons out of these molecules, and they change shape. Have these molecules in contact with other molecules, and you can cause shape-changes in those, too (possibly causing them to gain/lose electrons). Could be used for molecular machinery, or for 'molecular computers', which use such molecules instead of conventional semicondutor tech.

Impossible, surely?

[Cardbox]

As described in the press release, this is, by definition, impossible.

The two enantiomers of a chiral (asymmetrical) molecule are identical in every respect, except that they are mirror-images of each other. Call the two enantiomers of this particular molecule L and R. If you add an electron to L you get L-plus-an-electron (call it L+e) which by definition cannot be any less stable than R+e - in other words, the flip from one to the other simply can't be caused by the addition of the electron by itself.

I'm sure that these research findings are genuine but they've been edited into meaninglessness in order to make a press release - rather like the recent "space is flat" story, which, by the time it was "explained" for the general public, made no sense at all. The rules of editing press releases are:

1. identify the crucial elements of the story
2. omit at least one of them.

One thing that might have been omitted:

these molecules are part of a larger complex, or a lattice, or are simply combined in pairs (dimers).

Anything like that does give the possibility of an electron causing a symmetry-flip, because you're not flipping a whole system, just one part of it, and there's nothing to stop a system where one part only is flipped being significantly different from one where it isn't. The system consisting of two left gloves is about as valuable as the system consisting of two right gloves (system flipped as a whole) but a lot less valuable than the system consisting of one left and one right glove!

But I wish someone would get hold of the real information and fill in the gaps...

two different worlds

[KIngo]

This is a classical example of a collision of two different worlds with two very different sets of interest: slashdot vs. science. Let me elaborate.

• slashdot views nano-technology as a source of futuristic application systems, the science fiction realizable in our lifetimes. Terabyte molecular memory chips, terahertz optical computing, holographic computer screens etc. While this is a legitimate point of view, it differs radically from that of the
• scientist who is in search of a model system which displays novel and unexpected features, thus making a good case for a publication in Science or Nature. The scientist's reputation and job hinge on those publications. Rarely these works are closely tied to an application. The physicist (less true for higher level disciplines) is not an engineer, but a searcher in the dark, looking for wonders that challenge his/her intellectuality. However, the money for projects mostly comes from much more wordly sources which want to see results. Thus, scientist have become exceedingly good at combining and compromising between their financers' requests and their own agenda.

One of the less original ideas, though, is the announcement of a new type of memory. Anything can be sold to the public as a new memory. I have seen so many proposals for new types of memories come and go that I'll believe them when I see them.

These new chiral molecules do have special applications, I cite their website:

To date, we have applied our chiral ligands to the solution of several problems, including the determination of the absolute configuration of -alkyl pyridinemethanamines, the development of chiral solvating agents for sulfoxides, and the design of a chiroptical sensor for certain metal ions.

That's all right, but is it really a story for slashdot?