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Science

New Molecule With Switchable Chirality 56

Posted by timothy from the diamond-age-here-we-come dept.
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."
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New Molecule With Switchable Chirality More

New Molecule With Switchable Chirality

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  • Very interesting....

    If would kind of be good if the page said exactly what a chiral compound or whatever is. Does anyone know?

    And what can this new discovery be used for? Any suggestions?????

    (Not meaning to troll or someting, but that article wasn't very helpful)

  • Molecular polarity rocks!
  • ...but what is chirality?

  • Is that the molecular polarity of any given molecule is directly proportional to the force exerted on that molecule by the forces of the systematic enviroment of that particular instance of the system object in question, if, that instance of course, has anything to do directly with that molecule isn't relevant to the object itself, or in fact, the molecule's relationship directly, with that instance of the object's force. To put it simply, there's no way to find equivalence between the instantial force and the molecule's property grid.

  • It was explained in the article - sort of. Basically, any molecule that is not the same as its mirror image is chiral. Very simple molecules like CO2 (O=C=O) are not chiral. DNA, though, winds only one way and is NOT the same as its mirror image (proof: hold a slinky up to a mirror). DNA is therefore chiral.

    I think what people often mean by chiral is not only the above definition but the important additional point that you do not have a 50-50 mix of the two mirror image forms (called enantiomers). Most molecules that are manufactured artificially are chiral but you get a 50-50 mix of both forms so it isn't very useful. By contrast, almost all biological molecules are chiral and appear in only one form (all DNA everywhere, in every living thing, winds the same way).

    Since it is unusual and difficult, it is considered a big deal when scientists preferentially create one mirror image, thereby introducing some asymmetry where previously there had been none.

  • Definition of "chiral" (Score:3)

    by muldrake ( 171275 ) on Sunday May 28, 2000 @02:08AM (#1042169) Homepage Journal
    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 [utexas.edu]

  • A Chiral compound is... (Score:3)

    by mu_cow ( 168630 ) on Sunday May 28, 2000 @02:09AM (#1042170)
    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".
  • Thanks for the laymans definition, but why is this a big deal? Are there any pratical applications for this newly found molecular engineering?

  • Re:okay, so what? (Score:4)

    by Anonymous Coward on Sunday May 28, 2000 @02:17AM (#1042172)
    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.
  • 1. a step toward optical switching, is this?
    2. a step toward optical computing?
    3. a practical nano-level machine part.
    4. nano-sized lighting effects :P

    If there's anyone who knows more about those, I'd be happy to hear whether they're relevant.

    Is it just me or is this in its digital simplicity a much clearer advancement than the Canadian light-trap [slashdot.org] earlier this week? At least I find this exact data much more trustworthy.

    Obviously, it'll take a while before this will be a part of any nanofactories' product line outcomes. In fact, those nanofactories have not yet been invented either. Who cares, if it's going to take another 20-50 years or so. The future is on its way!-)

    OT: how come /. is only inhabited by trolls this weekend? Is it sunny spring in U.S. as well, or what?
  • It is also important to note that all naturally occurring biological molecules have one chirality (right-handed, I think, by convention), though this seems to merely be an accident of the initial conditions of the formation of life here.
  • Chirality refers to the stereochemistry of an atom, usually carbon. Carbon forms 4 bonds with things, each bond at a 109.5 degree angle (not 90!). At this angle, each atom bonded forms the corner of a tetrahedron with the carbon smack in the center, to maximize distance between each bonded substance.

    If the 4 objects bonded to the carbon is different, then the carbon is said to be chiral. This means that there is a NONIMPOSIBLE MIRROR IMAGE of this compound. A good example would be your hands. Your left hand is a mirror image of your right hand, but you cannot (palm down) overlay them. So, for molecule CClBrI, 2 of the bonded halogens (Cl, Br, I) cannot overlap in the mirror image.

    Chirality affects everything around us. For one thing, chiral molecules are optically active, meaning that it rotates plane polarized light, much like crystals in an LCD display. Cool thing is, say a molecule rotates plane polarized light 30 degrees clockwise. It's mirror image molecule (remember, these things come in pairs) will rotate it 30 degs counterclockwise.

    Biological activity is also governed by chirality. Sugar, for instance, is chiral (take karo syrup and 2 polarizing filters and play with it if you don't believe me). alpha-D-Glucose (one of the two sugars that form common table sugar, the other is alpha-d-FRUCTOSE) rotates light clockwise (I believe), and upon polymerization it forms starch, which we humans have an enzyme (also chiral) that can break it down. There is another form of glucose that rotates light counterclockwise called beta-D-glucose, and when that forms *CELLULOSE* upon polymerization. Because our enzymes are chiral, it will cleave starge (alpha polymer) into glucose, and we can digest it, but it won't cleave the beta polymer (cellulose). Termites and cows have a bacteria in their stomach that will synthesise the mirror image enzyme that will cleave the beta polymer, hence, they can eat cellulose, we can't.

    There are very cool implications to this. First of all, virtually all drugs are chiral, and in synthesis we have to perform isolation. Isolation of chiral substances often involves chromatography, and the chromatography column packing material to resolve chiral compounds are often (you guessed it) chiral. Improvement made in separation techniques will give better catalysts and better synthesis options, which in turn opens up new bio and non-bio synthetic techniques towards new material. Optical activity is used for LCDs, so potentially this could be used in LCD display (though the impact here is not that great, there are existing material that can fit this bill). Other potential applications include the possibility of using this in a electro-optical computer system.


  • Uuh, I cannot make sense of this. I would have moderated it down as "nonsense" or whatever.

  • Could you please give me more specifics as to what you can't make sense of ?

  • IANA chemist, but IIRC biological molecules sometimes appear in left-handed and right-handed versions, but the two versions do different things. For example, one of the molecules that gives oranges an orangey flavour - its mirror image is found in lemons, giving them a different flavour. Also with some drugs, the right-handed version might be beneficial and all the side effects come from the left-handed version. But it's difficult to manufacture one without getting an equal amount of the other. See the article Happily, it's an asymmetrical world [dawn.com] for more.

    (As for polarizing light in two different directions, I don't see why that's such a big deal. Liquid crystals do this already depending on what voltage you apply to them.)

  • No, it might not have been accidental. Somewhere down the line something might have started out one way (by choice) but then evolution would have dictated that the sucessful species generate enzymes and whatnots that are a specific chiraltiy.

    Look at the post I made in the other thread explaining the importance of chirality and the difference between cellulose and starch, and the difference in the enzyme requires to cleave it.

    Let's say that you're some protozoa somewhere, and you need to break down a food source that has a certain chirality. In order to be sucessful, your enzymes must fit this chirality requirement (much like threads on pipes) for this reaction to occur). From here on, your proteins, RNAs, DNAs, must all evolve to be of a certain chirality for everything to work...

  • If you can suspend an array of said molecules in a non-chiral gel, aim a x-y plane laser to it (or put the gel on an x-y stage), you have an (nearly completely) organic storage device.
  • Um...it's the wrong fsckin' answer?

    Anyone with OChem 101 can tell you that. And I'm a chemistry major.

    -=- SiliconKnight
  • Nice explanation, but one thing...

    The alpha and beta forms of a hexose sugar can have the same chirality - in your example, they do (D). Alpha and beta denotes which "shape" the molecule is - a glucose ring can exist in two forms, which look like a "boat" and a "chair" respectively, depending on which way you "fold" the straight "glucose" molecule

    You are right about the direction the molecules rotate light - D = dextro = right = clockwise, L = laevo = left = anticlockwise (counterclockwise for all you Americans).

  • Impossible, surely? (Score:3)

    by Cardbox ( 165383 ) on Sunday May 28, 2000 @02:43AM (#1042183) Homepage
    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...

  • I am assured that this mr. Valloppillil [vinod.com] pretender is but a troll, but what the heck, it's always better to have a chat by the bridge than to go out and burn in sunlight.

    A fine troll it seems, however, to gather positive moderation!

    Simply put, your over-long sentence does not parse. I'll break it down:

    "...the molecular polarity of any given molecule is directly proportional to the force" -

    Excuse me, which "force"? What kind of a "force"?

    "- exerted on that molecule by the forces of the systematic enviroment of that particular instance of the system object in question"

    Sentence this long does not sense make.

    Specify "systematic environment"
    Specify "particular instance"
    Specify "system object"
    Specify "question"

    "if, that instance of course, has anything to do directly with that molecule"

    What does "of course" refer to?
    "that instance" seems to refer to the previously mentioned "particular instance" of "system object." However, "system object" remains unspecified.

    "the molecule's relationship directly, with that instance of the object's force."

    What do you mean by this?

    To put it simply, there's no way to find equivalence between the instantial force and the molecule's property grid.

    Specify "instantial force"
    Specify "molecule's property grid"
    Specify relation to the first sentence
    Specify relation to changing chirality of a molecule?

    Why couldn't Microsoft have made NT a multiuser/multitasking version of MS DOS ?

    Why would/should they? On the other hand, isn't it?

  • lol (Score:1)

    by korpiq ( 8532 )

    So it seems to be, indeed :)

  • two different worlds (Score:3)

    by KIngo ( 168933 ) on Sunday May 28, 2000 @03:08AM (#1042186)

    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?

  • Quote from the Canary Lab site:

    In view of the prevalence of chiral natural compounds, chiral sensors and catalysts are of critical importance; however, they are in short supply. We were able to introduce chirality into the TPA scaffold by taking advantage of inherent conformational properties of certain TPA complexes.11,12 The observed amplitudes of some of the circular dichroism spectra of the complexes turn out to be remarkably large.13 To date, we have applied our chiral ligands to the solution of several problems, including the determination of the absolute configuration of -alkyl pyridinemethanamines,14 the development of chiral solvating agents for sulfoxides,11 and the design of a chiroptical sensor for certain metal ions.15 Other applications are presently under investigation.

    According to this paragraph, what they did was to introduce chirality into their molecules. I honestly doubt that they were causing a symmetry flip of one molecule (ie. switching between the L and R configurations of the same molecule); I think what was meant was that they had found a way of preferentially creating, say, an L or R configuration from a non-chiral substrate. This process was possibly also reversible, but the L and R compounds obtained through the addition/removal of an ion are probably different molecules, not the same molecule as the news article seems to be saying.

    I think one of the significant contributions of this is the applicability to finding the absolute configuration of molecules. If you've taken organic chem in college, you'd know that for a long time, chemists have no idea *which* version of a chiral molecule we're really dealing with, given an organic compound X. We know that X and its enantiomer are mirror images, and we can tell that they are different, but we cannot tell which mirror image X is. It's all based on the assumed configuration (either left or right) of a few basic chiral molecules found several decades ago. From this assumption, we `derive' the assumed configuration of many (all?) the chiral molecules today.

    But this research seems to have found a way of determining the absolute configuration -- ie. we can now tell which mirror image X is, with certainty. Of course, currently they only did that for a very limited class of molecules, but this can be developed so that one day, we can know the absolute configuration of all chiral molecules.


    ---

  • I am not too sure on this, but weren't the accidents with Thalidomide in the 70's caused by the fact that while one of the enantiomers was an efficient curing drug, the other one caused gross birth defects if the drug was taken by a pregnant woman?

    This shows the importance of separating enantiomers. This is a difficult but vital process in the "fine" chemical industry.

  • I am assured that this mr. Valloppillil pretender is but a troll, but what the heck, it's always better to have a chat by the bridge than to go out and burn in sunlight.

    Assured by whom? I never once said that my first name is Vinod, or that I'm related to this person. I'm not. My name is actually mark, second name Cedric, but a lot of people just call me Cedric for short :-) The spellings of our surname are even different. I don't see how I'm pretending at all, please clarify.

    Why would/should they? On the other hand, isn't it? No, it's not. It's a bloated mess that's sort of like VMS, but with mandatory graphics (graphics on a server??? WHY ???) If they had have extended MS-DOS to be multiuser and multithreaded, and then extended the Win 3.x system to match it, instead of making the whole system dependent on graphics and the incredibly cryptic, bloated, and poorly documented Win32 API, maybe people wouldn't hate them so much. I don't hate them, of course, I'm just suggesting what they could have done.

    I don't hate you either, even though calling me a troll is kind of offensive. There are real trolls on Slashdot, but I'm nto one of them. The Steve Woston troll is a real troll. The real Steve Woston is genuinely upset at being impersonated by this troll. The Real Steve Woston's site is here [mnc.co.za], you can read about what he thinks of the whole issue yourself. The guy is basically pissed off at being impersonated on Slashdot, and even though I agree fully with free speech and anonymity, it's a pity that things like this can potentially happen as a trade-off. Steve W0ston, Wost0n, or whatever you call yourself, please stop blackening the name of Steve Woston and generally making Slashdot unpleasant for the good readers of Slashdot.

    As for my post being "non parsable", I'm sorry that you don't udnerstand what I'm saying. Sure, some of my terminology might not be 100%, but the moderaters who originally moderated me understood that while my terminology might not be 100%, I was making a valid point, and they read between the inconsistencies to the truth beneath. Good job, moderators, thank you for not being small minded and understanding what I was trying to say. As for you, korpiq, read the post more carefully before blasting me as Vallopillal pretending (???) troll.

  • This is very true. IANAB(Y) [I am not a biochemist (yet)], but this story seems a little out of place. Everyone clamoring for the definition of chirality (which is a pretty basic chemistry concept) should be a good indicator of an article that's in a different league from "geeks." Not a better or more diffult league, just different.

    Back on topic, the whole thalidomide incident in the 60's was a good example of the different effects of chiral molecules. One of them was supposed to combat morning sickness. The other one led to serious birth defects (e.g., no arms, no legs, &c). Oops. Thalidomide is actually still used for leprosy. You can read more about future applications of it here [discover.com] - I won't bore you.

    Also, I believe that one of those OTC pain killers (aspirin, acetomeniphen, whatever) also has an interesting chiral property. When they make the drug, it comes out ~50/50 each enantiomer. Even though only one of the enantiomers works in the body, they don't bother to screen out the other, but leave it in as "dead weight." Turns out the body converts the "dead" enantiomer into the functional, working drug one on its own. Isn't science neato? ;-)

    ---- Stultus [mailto]

  • Did you actually read the post you just replied to, before replying to it, Anon ?

  • It's alst interesting to note that, upon death,many of the right-handed chiral molecules in our bodies convert into their left-handed complements.

    "When the indicator says you're out of oil, should you continue driving anyway?" - TMBG
  • In my ochem class we were calling pairs of enantiomers R and S, after the latin right and left (rectus and sinister). But everyone here seems to be using L and R, so I was just wondering what the rest of the world calls enantiomers.
  • Liquid crystal displays utilise a feature of liquid crystals in that they line up differently when a voltage is applied, and this twisted alignment causes polarised light passing through them to be rotated. There is a polarising filter on both sides (or on one side with reflective layer at the back so light goes through the same filter twice).

    When a voltage is applied, the area appears to go black, because the light polarised by the first filter has been rotated so that it doesn't go through the second filter. Where no voltage has been applied, the light goes through as normal.

    Scale this up a bit, make the areas to which you can selectively apply a voltage smaller, add a back light, print a matrix of magenta, cyan, and yellow blobs on the screen, and you have an LCD screen. The screen will be black when off because the two polarising layers are at right angles to each other, and no light gets through unless something (the liquid crystal layer) rotates the light between the two polarising filters.

    You can play with this if you have an old LCD calculator, and take it apart. If you find a removable polarising filter, you may be able to reverse it and find that your calculator now does white digits on a black background.

    Alternatively, you can remove it altogether, and have a calculator that only you can read (because you are wearing polarising shades).

    Back to the subject at hand; Will this process make LCD panel displays easier to build or cheaper? With CRT monitor prices dropping like, errm.. CRT monitors, nothing seems to be happening to LCD monitor prices; they are still ridiculously expensive (although I'm still drooling over the prospect of getting a nice 17" LG Electronics display (Saw one at Linux Expo, London last year, and it made me wonder what it was I've been looking at all this time...))
  • Only one enantiomer of thalidomide causes birth defects in the body, however, in the body, racemisation can interchange the chirality of the molecule. It is not safe to administer any enantiomer of thalidomide to any person who can become pregnant.
  • Chirality is literally handedness (<Greek cheiros, hand). Some molecules aren't totally specified just by the number and type of atoms that comprise them--the same set of atoms can be arranged in different ways. Some come in two arrangements, one the mirror reflection of the other, like one's left and right hand; hence the term "chirality."

    What I'm wondering is whether this can be turned into very high density memory.

  • I don't claim to be a physical chemist, but I do a fair bit of work with optically active compounds, and I'm pretty confident in saying that this reaction is likely to be far too slow to be of any use as a switch (logic gate, transister etc) in any kind of computing device -- perhaps this is obvious, but some are asking.

    On the other hand this does seem to be quite relevant to nanotechnology. There is an analogy in the visual system, where a pigment in the retina absorbs a photon and changes conformation (not chirality) -- this shape change ultimately triggers the neural impulse etc. The researchers do specifically mention sensors in their information, so perhaps this sort of chirality change would be useful as a detector of some sort. Or if you could bind one end of the molecule to a larger molecule like a protein, you'd have a teensy tiny lever arm. Neato.

  • I don't think it's out of place. Even though my chemistry is rather weak, I've learned a bit just from many of the responses to this story. Part of the reason I come here is to make sure I expand my technical horizions as much as I can.

    If stories only stick to what the general audience are already experts at, what good is that? All you have then is a thousand virtual Statler and Waldorfs heckling the same show for eternity - I think it would get stale.
  • Always was L and R for me, but then I took O-chem, ummm, 17 years ago now so maybe it's obsolete terminology. US vs. the world thing, perhaps? (I was in the US) Where did you take O-chem? Non US chemists out there, can you comment? Any IUPAC board members read /.? (cackle)
  • OT: how come /. is only inhabited by trolls this weekend? Is it sunny spring in U.S. as well, or what?

    In the US it's a 3-day holiday weekend Memorial Day (initially our Civil War remembrance, but now remembers all war dead). It is a big travel weekend, when people reopen their summer vacation homes, and all universities have ended their spring semesters by now as well so students are back home again.

  • It's L and D, and R and S. L and D is notation for which direction a chiral molecule rotates plane-polarize light: Levo (left) or Dextro (right). R and S refer to the absolute configuration of a molecule according to a systematic naming system. There is no correspondence/relationship between L & D and R & S.
  • They say they make a copper complex of the organic ligand. The removal/addition of an electron is without a doubt the oxidation/reduction of the copper center. A change in oxidation state may lead to a corresponding change in coordination geometry around the Cu atom. It's probably the case that both complexes are chiral, but that they are NOT enantiomers of each other (i.e. mirror images of each other). They may simply be two DIFFERENT chiral complexes that fortuitously rotate plane polarized light in opposite directions.
  • Assured by whom?

    Sorry, should've been "sure", not "assured" - my English failed me there.

    As for your point, I just can't read your original message so that anything understandable would come out. That led me into assuming it was a sophisticated-looking bunch of nonsense. Obviously, my limited ability of parsing English is to be blamed for this.

    NT hasn't evolved around DOS because it's a branch of joint operating system project with IBM. The other branch is OS/2. Generally, you can't always take the old code/functionality if you target something very different, and I'm afraid that's the case with NT as well. As for your point about stupidity of GUI-based OS, I wholeheartedly agree.
  • There's the material you need to make optical transistors possible. Depending on how quickly the polarization takes effect (I'm assuming damn near instantanious) we now have a way to interface electrical and optical systems together in a much more convenient way. Cisco should be eating its heart out right now - THIS will make a (near) pure optic router possible.
  • Moderators - read the thread below this post.

    This cvillopillil guy is oh so obviously a troll.

    Go get your free Palm V (25 referrals needed only!)

  • Actually, the L/D chirality is only defined as `chiral like the L (or D) glycerin-aldehyd', and two D molecules don't neccesarily rotate polarized light in the same direction (in fact, your definition is a sure way to get fired from your biochemistry exam:)
  • As it has already been pointed out, a chiral compound is a compound that has AT LEAST 2 different forms - both of which are mirror images of each other. In terms of organic chemistry, chirality is very important. Organic chemists define chirality to be any carbon atom that has four different "things" bonded to it. The chirality arises because these carbons are said to be sp3-hybridized, meaning that they look like tetrahedrons. This is the basis for the mirror image. In a compound with many carbons, you find all carbons which have 4 different things attachted to them (as carbon has 4 bonds) and call them chirality centers. The number of possible variations of that compound is 2^n, where n is the number of chirality centers. Chirality is important because it forms the basis for most organic reactions. For example, almost all sugars in nature are D-sugars. The reaction will not proceed with an L-sugar. (D & L just mean the different mirror image configuration). On the same note, enzymes only work with one isomer (either D or L) and so on. It isn't particularly hard to change chirality centers either.
  • I am former member of the Canary lab (back when I was doing my PhD), and here is one of the first papers we published on dynamically chiral compounds: http://www.ch.ic.ac.uk/ectoc/echet96/papers/003/in dex.htm This web paper was written back in 1996, and has some animations, as well as some more background on chiral compounds (tripodal metal complexes in particular). Some of the structures need to use a plugin from www.mdli.com (ChemChime). Simple explanation: In these systems, there is equal probability of finding either conformation (left-handed or right-handed), in the systems we were working, a single point derivatization of the organic part leads to a bias towards one of the conformation w/ respect to the other, hence dynamic chiral control.
  • Judging from the title of the paper, I think the experiment doesn't have much to do with conversion from L to D-amino acids.

    Typically, helical chirality refers specifically to the "handedness" of macromolecules such as DNA and proteins. For example, DNA is normally in its "right-handed" B form, but it can also adopt a "left-handed" Z form. The handedness of a macromolecule is determined by the screw sense of its helix, Of course, these types of chiral compounds are also optically active.

    Apparently, helical chirality can also apply to carbon chains with identifiable rotational conformations as well (rotational conformations such as gauche and eclipsed...best to refer to an O-chem textbook, because I don't remember them too well.)

    In either case, it isn't too far fetched to imagine that copper atoms can cause changes in helical chirality.

    But my question is: is this experiment about the helical chirality of poly-dialkyl-Met chains, or the helical chirality of a single dialkyl-Met residue?

  • Sure!, why not?
    [Latency] Some posters said it is like a liquid crystal effect, but not in all ways. It stays whatever orientation it is after the juice is cut, wheras an LCD will blank. It makes a storage device possible, and if you cram a bunch of these molecules onto a disk(needing 1 molecule thickness), a suitable R/W head, you're talking serious storage(100terabyte disks!)
    [Optical computing] as long as the structures aim light at the molecule, detect it, I see no reason why not. They(opto chips) would need to polarise light to notice the difference, or use a detector that knew the angle of rotation.
    [Heat] Bane of all computing and mechanical devices, is the molecule stable over a wide temperature range? It would be the only forseeable problem to making an opto chip. So long as we are using packets of energy to represent on-off states, it will generate heat. Drain it away quickly enough, no problem.
    [Nano-nano] If one wanted to wiggle a molecule to do work, no. It is too small(but efficient, 1 electron!), and the mass it could move would depend on the momentum of the electron itself. Not a very useful bit of energy, even if incorporated into long chains, they would still be of little effect. If however, the molecule changes shape, say 40% difference in forms, or straight to a ball, it might be a first step.
    What I do see is a replacement for paper, electronicaly written to, and erased, reused. Or an entire screen(you wouldn't need a super fast refresh rate, but it would need to remove the electron as well, meaning a CRT is out).
    Or, as another reader eludes to, suspend into a matrix, and make holograms(again, adding/removing the elecron is tricky part)
    How about this for scary, put a bunch of non-toxic molecules on the surface of your eye, and recieve stock quotes all day.(or the stupid ads paying for it....)
  • This is just the type of story that I love to see on Slashdot, simply because it is non-applicable science. I guess I'm just a helpless science geek. But your post brings up a very salient point.

    The scientific posts on Slashdot (physics, biology, chemistry, etc.) sometimes seem to be garbled and misunderstood almost to the point of complete inaccuracy. For example, check out the "Welcome to Gattaca..." article that's still in the Slashdot "Science" section and the comments about Michael's misunderstanding of his source.

    Part of this problem is that most of Slashdot's readers and moderators are hardcore techie geeks, as opposed to science geeks. Thus, I may not understand everything about the "Tru64" posting, but judging from the comments, it's all accurate and in-depth. However, when reading through scientific posts, one usually has to ignore the post and go straight to the actual article itself.

    Possibly, Slashdot needs to acquire some more scientific moderators, especially biology- and chemistry-oriented moderators. I see quite a few physics articles around, probably because physics has traditionally had quite a bit of application to techie fields, and thus can be quite interesting to the average /. reader. However, now that molecular and chemical computing is emerging, some dedicated chemical/biochemical moderators would really help increase the quality of the posts.

    Don't get me wrong. It's by no means bad that most of /. is techie-oriented. That's its basic function, and I learn a lot from carefully reading the in-depth technology posts and comments.
    However, when it comes to science posts, I'm better off just reading the article and paying attention to the few commenters that actually know what they're talking about.
  • cvillopillil [slashdot.org] and Steve Woston [slashdot.org] are the same troll. You can tell by the identical writing styles, although when he trolls as cvillopillil his lure is more sophisticated. It's sort of a "good troll, bad troll" game to get people to fall for the cvillopillil version.

    Moderators, please moderate all cvillopillil posts down.
  • The absolute COOLEST prospect of a chirality changing molecule is the polorization changing properties. If you have an electron that has 1/2 probability of being added to this molecule and use light as a transmission medium for possible further switching of the molecule down the road you could have something...

  • I would refer you to the cited papers, and to an old (ca March-April 1996) web article: Dynamic Control of Topological Asymmetry [ic.ac.uk]

    In that earlier report you can clearly see the biasing of a molecule conformation by a simple metal binding event. This was detected by optical methods.

    Since them, other systems have been described by the same group, redox systems (Cu for example), in which there is a very strong conformational change affecting the optical and the electronic properties of the system. And this was very reproducible and stable.

    I am a former memeber of the group, when I was doing my PhD at NYU

  • It is not that the Copper atom changes the helical chirality, it is that upon binding the systems undergo a biasing of one of the possible helical conformations.

    When you oxidize/reduce the copper atom, the system undergoes a conformational change that is still chiral, but different in geometry, and thus it generates a different electro-optical response.

    For more info, look at the web article I mentioned elsewhere. It is an initial report back when I was workging on my PhD at Canary's lab.

  • Sounds like they came up with some new method of making a qubit. If this is the case, and they *did* actually patent it, it's another case of the patent system being corrupt. (I don't know the specific research you are referring to, but the idea of 'switching' a single atom is something that has been investigated for some time now (early 80s.)) In any case, it is amazing to see that in the last 2 years or so, quantum computing technology has gone from, "well, this works, in theory," to "damn!! it's only a 4 qubit machine, but it HAULS." I was doing some background research for a project that I worked on last semester and it amazed me that from the point in time wherein I started writing the paper to the time when the paper was completed, my research was *already* out of date. Keep in mind that there is not, as of yet, a real quantum computer, but there have been actual functioning quantum computing cores. That is to say that qubits have been made, and they interact with each other, doing calculations, and not losing data. This is a big step, and it has been made only in the last year. I haven't looked at the current research on this in the last couple of months, so I bet there is something even more impressive to say for someone who has the time/energy to go peruse Phys. Review Letters or any of the other publications that are likely to have incredibly boring but informative articles on what is currently going on.
  • The absolute configuration can be determined experimentally by X-ray crystallalography. Essentially it is a way to obtain the configuration of a molecule in 3 D spcce, and this includes the absolute configuration around a stereo centre. There are other ways that are more abstracted,in that you use the properties of already determined molecule to determine the configuration, like chiral HPLC, or synthesize the compound from appropriate optically active compounds.
  • Your right, the reasson that everybody is calling them L and R is that not many people on slashdot are chemists.

    Anyway they are R and S, according to IUPAC naming conventions. Unless you are working with carbohydrates, or other biological materials, then it is D and L, which is related back to the absolute configuration of Glyceraldehyde If I am not mistaken.
  • "another case of the patent system being corrupt"

    Is it just me, or does every single thread on /. end up bashing patents in some way or another? I suppose it's reassuring, in an odd kind of way.

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