Wikipedia:Reference desk/Archives/Science/2009 December 1

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December 1

Zygotes implanted in the wombs of other species

Has this ever been done in controlled experiments? I wonder how close the species have to be (if anything less than exact species matches can) for the fetus and mother to be able to create a compatible placental link without the mother's body seeing it as a foreign substance and killing it. 71.161.61.41 (talk) 01:06, 1 December 2009 (UTC)

I don't think the mothers body would see it as foreign. The problems are more likely in other areas. For example, a newborn has a special kind of hemoglobin which has a higher affinity for oxygen than the mother (so it can pull oxygen out of the mothers hemoglobin. So that has to match in a different species. The nutrition requirements must match, and the physical size of course. Possibly the most difficult is getting the placenta (which has the dna of the child) to embed in the mother. I have a vague memory of hearing about an extinct (or close to it) species being cloned, then embedded in a different, but similar, species (but I don't know if they did it, or just planned to). All that said, this is a very interesting question, and I don't know the answer. But I figured I'd post what I knew, since you didn't have any other replies. Ariel. (talk) 02:07, 1 December 2009 (UTC)

That would be the woolly mammoth in an elephant, I believe. 90.195.179.130 (talk) 06:37, 1 December 2009 (UTC)

Doesn't the blood get exchanged? Won't the blood cells be identified as foreign? 66.65.141.221 (talk) 03:47, 1 December 2009 (UTC)

No, unless there is a fetomaternal hemorrhage, the blood of the fetus and the mother do not mix. See Placenta#Fetoplacental_circulation. --NorwegianBlue ^talk 22:54, 1 December 2009 (UTC)

I'm pretty sure it would get rejected. Just look at how difficult it is to transplant organs between different humans. Or the fact that humans can form antigens even against their own fetuses. (e.g. Rhesus factor) Add to that different gestation periods and easily thousands of different factors that have to match up, most of which are probably unknown to us. I don't believe it's been attempted and I think it would be outright unethical to even attempt such a bizarre thing, given that there's zero probability of success. You're talking about literally millions of foreign proteins and compounds, every single one of which could possibly trigger an immune system response in the host/mother. --Pykk (talk) 06:45, 1 December 2009 (UTC)

As our article on Cloning#Cloning extinct and endangered species briefly mentions, it has been attempted before, obviously only in related species; with the zygote species usually being endangered. It obviously often comes up when discussing cloning extinct mammal species (for obvious reasons) and cloning or IVF reproduction of endangered mammal species (using mothers of the endangered species may be a bit risky and limiting). For example, this [1] shows some research in 1988 i.e. long before Dolly; this shows a horse mare and it's zebra surrogate child [2] [3]; and in fact this ref says the first case was in the 1970s [4]. Obviously for some of this stuff e.g. zebra/horse it's not that surprising it works since zebra/horse hybrids are possible; in the surrogate case the offspring does not have any genetic complement from the parent species unlike hybrids which have half, but on the other hand it doesn't have to cope with any problems arising from a mismatch (perhaps not the best word but can't think of anything else) of genes. I believe most research/interest now has been for cloning, probably because IVF likely still has some significant risk for the mother and because cloning is the hot thing nowadays. Or perhaps there's a fair amount of research ongoing with cases of non-cloned animals it's just harder to find refs since it isn't so 'hot'. [5] discusses the case of the Pyrenean Ibex (also mentioned there) which has so far been unsuccessful. There's also been discussion about panda cloning [6] and as that mentions and discussed here [7] there was some success with implanting panda embroyos in rabbits, obviously not with the intention of the rabbits carrying the pandas to term but to show implantation is possible (I believe using rabbits as temporary hosts is common so using them to attempt implantion would follow on). Obviously a better surrogate species would be necessary, what I'm not sure but presemuably some kind of bear. This perhaps raises one of the other issues. If you're using a cow, horse, sheep, goat, pig, etc as a surrogate that's easy since they're domestic animals and you can get large numbers. On the other hand if you're using a lion as surrogate for a tiger you may not be making things much easier then just using tiger surrogates while creating additional problems. Anyway although the last ref on pandas is from 2002, there doesn't seem to have been any significant new news I can find perhaps it was abandonded due to opposition [8] or was simply unsuccessful. There's also [9] which could be of interest altho I'm not sure if it discusses anything not in the other refs/our article and this [10] for a more scientific viewpoint. Interspecies surrogacy appears to be the common term but we have no article and while a useful search term you also get stuff like mother cats looking after puppies. Nil Einne (talk) 10:16, 1 December 2009 (UTC)

I guess that the surrogate mother could be heavily immuno-suppressed for the duration of her pregnancy using drugs - but this brings up another related question. How come there are not immune reactions to surrogate children (even of the same species) more frequently. IgG does cross the placental barrier - so why doesn't it attack foreign antigens that you would certainly find in either someone else's child, or even your own child?

Gene Therapy and Hormones

In theory, could gene therapy ever be used to replace or increase the estrogen and progesterone hormones, even if a woman's ovaries have been removed? —Preceding unsigned comment added by 71.156.167.121 (talk) 02:28, 1 December 2009 (UTC)

Gene therapy is in its very early infancy, so what all will ultimately be possible with it is really quite speculative at this point. So I think the sentence at the top of this page may apply here: "The reference desk does not answer requests for opinions or predictions about future events." Red Act (talk) 10:20, 1 December 2009 (UTC)

Perhaps your understanding of gene therapy is a bit misguided. All cells of the body have the theoretical potential to express all genes and produce all proteins. That being said, certain limitations exist for the vast, vast majority of cells in an organism such that they differentiate and lose totipotency/pleuropotency. Because all cells still retain the DNA to make all proteins, though, gene therapy, which works to supplant missing DNA (as in the case of a hereditary, genetic disorder) won't really accomplish what you are asking it to do. What your case would need is a de-differentiation/redifferentiation process by which another cell type would be able to produce ovarian hormones -- something that might work with a cloning-like procedure but is likely not happening anytime soon. DRosenbach ^{(Talk | Contribs)} 13:19, 1 December 2009 (UTC)

I have to disagree. There's no reason to think that, "in theory", gene therapy could not accomplish the production of estrogen and progesterone from a non-ovarian tissue. Gene therapy isn't about de-differentiating a cell type but rather adding back a normal copy of a mutant gene or adding some exogenous gene that will help to correct a disease (in this case, lack of ovaries). Each application of gene therapy is going to have a different target cell type and different approach. There may be some cases in which a small patch of muscle tissue (or other tissue) could produce enough of a certain gene product to reverse the symptoms of a disease. However, other disorders would require replacing the defective gene in a large proportion of the body's cells (which we currently can't do). The problem with the OP's question is that the gene therapy we have now would be like using a sledgehammer to try to cut the facets of a gemstone. It requires some really fancy tricks to mimic the endogenous switching between estrogen production and progesterone production in a fashion similar to the female menstrual cycle. Ideally, you would want your transgene to be under the control of the endogenous gonadotropins released by the pituitary gland, FSH and LH, which would be even more complicated. The answer to the question is that yes, it could probably be achieved using gene therapy, but in reality it seems unlikely that this type of therapy would ever be developed given the already existing (and relatively inexpensive) hormone replacement therapy or combined oral contraceptive pills. --- Medical geneticist (talk) 14:19, 1 December 2009 (UTC)

Air bubles in tap water

In modern tap water we see a lot of air bubbles, from where it comes and when we put our hands the splashing is very less compared to old taps?203.199.205.25 (talk) 09:31, 1 December 2009 (UTC)

The bubbles are there due to the faucet aerator, which not only reduces splashing, but also saves water. Unfortunately, the little stub article explains that the aerator breaks the stream into little droplets, but doesn't explain why that would help reduce splashing compared to a laminar flow of water. Red Act (talk) 09:50, 1 December 2009 (UTC)

Is everything energy?

As the subject line says. Is all matter made ultimately of energy? (Please excuse me for posting this. I should know the answer but I'm full of cold and my head is made of cotton wool.) --TammyMoet (talk) 10:16, 1 December 2009 (UTC)

That's basically correct. The mass of a body of matter is a measure of its energy content. See Mass–energy equivalence. Red Act (talk) 10:28, 1 December 2009 (UTC)

Thanks Red Act, I knew we had an article on it somewhere! --TammyMoet (talk) 11:45, 1 December 2009 (UTC)

Red Act is correct to point to mass-energy equivalence, but that does not mean that "all matter is made ultimately of energy". Energy is just our label for the quantity that is conserved in the conservation of energy law. Mass-energy equivalence establishes an "exchange rate" for converting between mass and energy. It means that conservation of energy and conservation of mass, which had origimated as two separate conservation laws, are now merged into a single conservation law. But the conversion does not have a preferred direction - we could just as easily say that the energy content of a body is a measure of its mass. From this point of view, we could, for example, assign a relativistic mass to photons, and add up the relativistic masses of colliding particles instead of adding their energies. But this is just a change of viewpoint - it does not mean that all energy is made ultimately of matter. There are several other conservation laws, and each of them gives us some information about which physical processes are possible and which ones are impossible (although when you introduce quantum mechanics, things are not as black and white as this, and possible/impossible becomes probable/improbable). But none of these conservation laws tell us anything conclusive about the ultimate constituents of matter. Gandalf61 (talk) 13:00, 1 December 2009 (UTC)

Mass-energy equivalence is one of the fundemental threads that actually shows up, in one form or another, in all of modern theoretical physics. It isn't that matter is a form of energy, or that energy is a form of matter. Its that the two are the same exact thing, but being observed under different conditions or in different environments. The same basic principle is at work in wave-particle duality, that is all of the universe can be said to behave in a wave-like (energy-like) manner, or as particles (matter-like) manner. That is, everything is both an object (particle) and a wave (energy), its not so much that anything "chooses" one form or another, its that the method of observation of something determines which properties of that thing you actually see; some methods of observation lead to wave-like properties being highlighted, while others lead to particle-like properties (see Double-slit experiment for a discussion of the principle at work in electrons and photons). For really big things, we only have observation methods that highlight the object-like nature of them, but when you get smaller and smaller, you can arrive at more and more wave-like properties comeing out. See also DeBroglie wavelength for the theoretical wave-particle duality in large objects, Schrödinger equation for the complex mathematics of wave functions of matter (there is even a possible Schrödinger equation which describes the entire universe as a single wave function), and Copenhagen interpretation for some of the philosophical implications of mass-energy equivalence. --Jayron32 20:57, 1 December 2009 (UTC)

Actually no. What it means is that mass and energy are the same thing! They are two words that mean the same thing. There is no test that can distinguish them, and no definition that discriminates between them. They are not interconvertable, they are the same. Note that "matter" and energy are not the same. But "mass" and energy are. Matter is energy plus quantum numbers, like charge or boson, spin, etc. And don't get confused by concepts like a photon being massless - it's actually that it has no rest mass, not that it's massless. All that said, I think the convention is that energy that is tightly bound in matter is called "mass". So the binding energy of an atom is called mass, but the heat, and velocity of an atom, it called energy, even though both contribute to it's gravity, and weight, etc. Heat is easy to remove from an atom, the binding energy is not. And to answer the question in the title, everything is not energy, because there are quantum numbers that are conserved, which also make up the universe. Ariel. (talk) 21:14, 1 December 2009 (UTC)

Regarding your last sentence, it depends on what the meaning of the word 'is' is. I would take the question "is everything energy?" to mean something like "within a closed region of flat spacetime, does what is contained within that region differ from a vacuum if and only if the total energy within that region differs from the total energy of a vacuum?". The answer to that question is "yes". You're taking the question "is everything energy" to mean something like "within a closed region of flat spacetime, is total energy the only conserved property of what's within that region?". The answer to that question is indeed "no", but I don't think that was the intent of the original question. Red Act (talk) 23:34, 1 December 2009 (UTC)

Regarding quantum numbers; don't quantum numbers all sum to zero when added across the whole universe anyways (i.e., the universe is neutral?). So there is nothing "extra" there that needs to be conserved once you have taken account of the energy/mass. Yes, they are conserved, but only to maintain the neutrality of the universe; there's nothing "left over" once you factor out the energy/mass! If so, then the singularity at the big bang would have had a net charge, and that doesn't make much sense... --Jayron32 00:41, 2 December 2009 (UTC)

Jayron32: That's the whole question of baryogenesis. Red Act: Your first question is also not what the op asked. You are basically saying there can be no quantum numbers unless there is also energy. A fine statement (is that really what you meant to say though?), but not what the op asked. The op asked is there anything else besides energy in the universe. And the answer is no, there are also other conserved quantities (as Gandalf61 said). In truth we are arguing over words, because the op's question is not well defined. But hopefully reading this will give him the answer anyway. And BTW, your answer to him was correct, I was arguing with Gandalf61 who implied that mass and energy were different, but they are not. They are not simply interchangeable - they are the same. Ariel. (talk) 01:36, 2 December 2009 (UTC)

Yes, loosely speaking, I was basically saying that there can be no quantum numbers unless there is also energy. Something physically exists if and only if it has energy. (I'm here ignoring vacuum energy and the complexity of the quantum vacuum.) So it works as a reasonable perspective to say that everything consists of energy, and quantum numbers are a way of describing some of the properties of that energy. I'm not saying that that's the only correct perspective, merely that it's a reasonable one. If you have a cubical granite rock, most people would say that it clearly consists of granite, and has a property of being cubical, rather than arguing that it consists of granite and cubicality. But the distinction between "consists of" and "has a property of" is a lot more arbitrary at small enough scales. That's ultimately not well-defined AFAIK. Red Act (talk) 07:29, 2 December 2009 (UTC)

I agree that energy and mass are indistinguishable and interchangeable - energy has mass, and mass has energy. And therefore we cannot say "everything consists of energy" without also saying "everything consists of mass". But the latter formulation sounds just wrong because it begs the questions "where does the mass come from ?" and "why do different bits of mass (i.e. fundamental particles) have different properties ?". You might as well say "everything consists of blue - but some of that blue appears to be green or red". Gandalf61 (talk) 12:01, 2 December 2009 (UTC)

Sell copyrights of my research work

Hi folks,

I have done a research work and project has come really well. My research paper has been chosen for publication in a Internatinal Journal in USA. I am basically from India. I was thinking like it would be better if I could give the copy rights for any of the research company so that my work (which I believe will cater the need of many doctor's world over) will get improved more. To be more specific My project is an Ophthalmology related one. Its not about drugs, its about diagnosing a device. So it will be a great help for me if any of you folks coul give me some information with regards to this (I don't have much knowledge in this field thats why asking).I am really sorry if I have posted in the wrong section.Thanks in Advance.

Thanks in Regards. —Preceding unsigned comment added by 202.54.176.51 (talk) 10:46, 1 December 2009 (UTC)

• Does copyright help? Also, if your research pertains to an ophthalmological diagnostic device, it seems like patent may also be a helpful article. However, we can't give you legal advice about copyrights and patents as they may apply to your specific case. Red Act (talk) 10:59, 1 December 2009 (UTC)
• (ec)You don't have copyright in the scientific results of your work - these could, if at all, only be protected by a patent. Copyright only protects the expression, not the ideas or the data. You do hold copyright to the actual text you wrote, but if you publish it in a journal, you almost certainly have to transfer copyright to the publisher - at best, you give him a fairly unrestricted license, but more typically you transfer it and receive some rights back. Sorry, that's how science works, and that's why scientists are rarely rich ;-). If you only want the results to be used (fame for you, better life for humanity), make sure you publish in a good journal and bring the paper to the attention of people who might be interested. If you want to make extra money, you need to apply for a patent, but a) it could be too late and b) its a fairly involved and none too cheap process, and there is no guarantee that you will recoup the money. --Stephan Schulz (talk) 11:07, 1 December 2009 (UTC)
  • One nitpick. In the US system you can't copyright scientific data, but in the UK and some other places one can claim a copyright over data. (Personally I think such copyrights are dumb, but I don't write the laws.) Dragons flight (talk) 01:47, 2 December 2009 (UTC)

If you publish your article in a traditional subscription journal you will be asked to transfer copyright to the journal as part of the process - and they won't pay you for it. See Scientific journal#Copyright. If you publish in an open access journal, i.e. a journal that is free to read and reuse, you will generally retain copyright, but you will usually have agree to release your work under a free license like the Creative Commons license. You need to pay to publish in many but not all open access journals,[11] and many open access journals will give full or partial waivers of the publication fees for researchers from countries like India. Fences&Windows 15:47, 1 December 2009 (UTC)

Size of processor dies

Does anyone know how large a typical processor die (I believe they're also referred to as wafers prior to assembly into a processor) would be? This [12] is exactly what I'm referring to - but I couldn't see a scale. 157.203.42.175 (talk) 13:19, 1 December 2009 (UTC)

First google hit has some numbers for recent chips: [13]. --Sean 13:32, 1 December 2009 (UTC)

FYI: I work in a fab where things such as that are manufactured. We refer to them as 'chips'. A 'wafer' is a round piece of silicon on which several to several hundred chips are built. See wafer (electronics). Dismas|^(talk) 14:14, 1 December 2009 (UTC)

Sean, thanks. Not sure how I missed that one. 157.203.42.175 (talk) 15:04, 1 December 2009 (UTC)

You can also look for pictures of naked cores, i.e. with the IHS removed. Extreme overclockers particularly those using water cooling sometimes do it (it's probably less common now then it was before because they are usually soldered) to improve cooling. The solder may confuse things a bit but if it's sufficiently removed you can usually see the size of the actual core. E.g. [14] [15] [16] [17] [18] [19] [20]. While these don't carry measurements (well one of them does and actually tells you the official size so you can see it's fairly close), you can work it out if you know the size of the entire processor (i.e. including circuit board) which probably isn't that hard to find out given that these are consistent within a processor socket for obvious reasons. Also [21] of a GPU (harder to find the dimensions but it helpfully includes a Singaporean coin). I'm not sure if all modern GPUs include an IHS anyway. I also came across [22] of a poor removal (of an already dead processor) which may be of interest because you can actually see some of the layers Nil Einne (talk) 23:46, 1 December 2009 (UTC)

Back before we had flash memory - lots of chips would have on-board UV-erasable, Programmable, ROM (UV-EPROM). In order to get the UV light into the chip to erase it - they had quartz windows over them - which handily lets you see the naked die inside. The processor in the photo to the right here is an ancient (and very simple) 8048. For scale, the pins on the side of the package are 1/10th of an inch apart. SteveBaker (talk) 00:36, 2 December 2009 (UTC)

the acidic group in aspartate/glutamate is COOH. what do you call the basic group in arginine?

That R-NH-(C=N)-NH2 motif. Why isn't this motif more common among organic compounds as carboxylic acids? It's kinda like the basic equivalent of COOH, isn't it? John Riemann Soong (talk) 15:48, 1 December 2009 (UTC)

It's a Guanidine group. I have to ask...did you actually look in the arginine article before posting the question about what its sidechain motif is called? It's stated in the first sentence of arginine#Structure. DMacks (talk) 17:00, 1 December 2009 (UTC)

I took a quick glance. I have to say, the phrase "the distal end of which is capped by a complex guanidinium group" isn't the most eye-catching sentence ever. Well anyway, why isn't the C+ carbocation resonance contributor shown? I would think it would be a major resonance structure, since with three electronegative nitrogens I imagine that that carbon is very positive. (In fact some 3-21 calculations show it to have over full positive charge!) Is a guanidine group much more reactive to nucleophiles than carboxylic acids, especially when protonated? Or does the delocalised positive charge, etc. make it react like amides? Basically why isn't this group hydrolysable under mild conditions (physiological conditions even) -- I imagine that hydrolysing a guanidine group on a protein (maybe converting it into an amide) would be potentially bad. John Riemann Soong (talk) 18:16, 1 December 2009 (UTC)

When you protonate the imine to make the guanidinium ion, this puts a + charge on a nitrogen. Basic rules of resonance will show that such charges are shared among alternate atoms; if you do the "electron pushing" to shift between resonance forms, there is no possible resonance form which puts a + charge on the carbon. Thus, there is no carbocation contribution to the resonance structure of guanidinium. The formal charge on the carbon is 0, and on each nitrogen is +1/3. Yeah, the electronegativity would indicate that having nitrogen at a higher formal charge would seem to be an intuitively backwards situation; but its just that there is no mechanism to have any charge on that carbon in guanidinium. --Jayron32 21:06, 1 December 2009 (UTC)

If the π electrons of C=N⁺H₂ are pulled into being a lone-pair on that N without another N lone-pair pushing it, you get C⁺(NH₂)₃ (for the parent structure). All this arrow-pushing would mean each N is sp² and the whole guanidinium is planar and highly resonance-stabilized, which is a common explanation for why guanidine is such a strong base. Of course, Nature is more clever than we are (once we actually study Her): turns out the NH₂ are actually rotated (propeller-like geometry around the C) and therefore there is not nearly as much resonance as simple arrow-pushing might predict. And that the high basicity is due to H-bonding of the added proton, not really enhanced electronic stability of the structure. See doi:10.1021/ja00059a035 for info. DMacks (talk) 22:51, 1 December 2009 (UTC)

In other words, it depends on whether the imine-N lone pair OR the imine C=N double bond is a better lewis base as to whether you end up with the carbon with a +1 formal charge OR you end up with the three nitrogens with a +1/3 formal charge. I'm pretty sure that in most cases, lone pairs are better lewis bases than π-bonding electrons are, which gives us the + charge distributed among the N's and not the C. --Jayron32 00:34, 2 December 2009 (UTC)

Putting cancer cells to sleep

I was reading about Kodiak bears' reproduction, specifically the part that says:

As soon as the egg is fertilized and divides a few times, it enters a state of suspended animation until autumn when it finally implants on the uterine wall and begins to grow again.

this made me wonder if any researchers are seeing if it would be possible to find out how to do that to other cells than Kodiak bear embryo cells by finding out how exactly it's done there (if that suspended animation functionality is a property of the Kodiak embryo cells themselves, an interaction in that specific kind of womb, or something else). The first application that came to my mind for stopping cell division of targeted cell types was cancer treatment. 20.137.18.50 (talk) 18:52, 1 December 2009 (UTC)

As I understand it - the difficulty isn't with killing or preventing subdivision of cancer cells - the problem is with finding ways to attack ONLY the cancer cells. If you have some way to direct a drug or other treatment to JUST the cancer cells - then there are any number of nasty things you can do to them to wipe them out. SteveBaker (talk) 00:30, 2 December 2009 (UTC)

Is there a medical term for this?

I think this might be closed-eye hallucination but I'm not sure...when I have my eyes closed when I'm about to go to sleep I sometimes see wallpaper-like repetitive patterns of leaves and flowers, or sometimes just ambiguous droplet-like dots. What is this called, if it isn't just CEH?--Editor510 ^{drop us a line, mate} 19:26, 1 December 2009 (UTC)

This seems to be a stage between consciousness and dreaming, akin to hypnogogic imagery. The mind may be perceiving the random sensory data as patterns. A higher level of dreaming would be perceiving the patterns as scenes rife with meaning, in vivid detail. If one attends to the incipient dream stage, the increasing level of consciousness causes the percept to revert to the original random patterns. See also the controversial Lucid dreaming. Edison (talk) 06:47, 2 December 2009 (UTC)

You may also find Prisoner's cinema interesting. cheers, 10draftsdeep (talk) 18:52, 2 December 2009 (UTC)

It may be related to Charles Bonnet Syndrome. -Craig Pemberton 02:06, 4 December 2009 (UTC)

It may be afterimages of whatever you were looking at that is, staring at, before you closed your eyes. Are you staring at leaves and flowers, or rain splashes on the window? --Janice Vian, Ph.D. (talk) 23:56, 6 December 2009 (UTC)

aspartame

I think saccharin is considered safe because it is broken down into non-toxic components in the stomach. What about aspartame? Is it broken down into non-toxic components during digestion or does it break down into toxic components during digestion which can be absorbed into the blood stream? 71.100.160.161 (talk) 21:38, 1 December 2009 (UTC)

Aspartame has some information pertaining to this. Unomi (talk) 21:42, 1 December 2009 (UTC)

Gums Bleeding

Before this question is dismissed as medical advice, please read carefully.

Why do one's gums bleed when there are a lot of bacteria proliferating on them? For instance, when someone avoids bruching their teeth for a while, and then brushes them, a lot of bleeding is observed. Why?130.127.52.67 (talk) 21:56, 1 December 2009 (UTC)

My understanding is this has nothing to do with bacteria at all. Gum tissue is simply sensitive, and if brushed regularly "toughens" against the assault of the bristles. The same can be said for flossing. If you don't floss for ages and then start, you'll look like you got on the wrong side of Mike Tyson. 61.189.63.183 (talk) 22:30, 1 December 2009 (UTC)

That would be a misunderstanding. DRosenbach ^{(Talk | Contribs)} 03:33, 2 December 2009 (UTC)

It is bacteria - see the link below. --Tango (talk) 22:38, 1 December 2009 (UTC)

See the two articles linked to from Gum disease. --Tango (talk) 22:38, 1 December 2009 (UTC)

There is a space between the gum and the tooth called the sulcus or gingival crevice. In health, the depth of the sulcus occurs where the junctional epithelial cells attach to the tooth. When the gum tissue is inflamed due to plaque, the depth of the sulcus no longer consists of fit, rigid junctional epithelial cells, but rather of flimsy, somewhat irregular epithelial cells. The epithelial barrier exists in an ulcerated state during gingival inflammation (otherwise known as gingivitis) and thus, bleeding from the underlying connective tissue occurs more easily, either when stimulated, or in cases of worse inflammation, even unstimulated. Plaque causes gingivitis and junctional epithelial ulceration because it is essentially minute food particles colonized by bacteria. Bacteria secrete all sorts of noxious and nasty chemicals, such as endotoxin and collagenase that stimulate a host response that induces inflammation via histamine and various interleukins and degrades colalgen, respectively. Let me know if there's anything else you'd like to know. DRosenbach ^{(Talk | Contribs)} 01:46, 2 December 2009 (UTC)

the economics of enantioselective chemistry

Are enantiotopically pure substances typically:

• Less than twice as expensive as a racemic mixture
• About as twice as expensive as a racemic mixture, with a little more to compensate for reagent consumption/workup
• More than 2x expensive as the racemic mixture?

Basically I'm wondering how price economics might convince companies whether to adopt an asymmetric process versus a chiral resolution process (where you discard half your yield). I imagine it might be variable for the substance involved (like if one enantiomer of a drug was particularly poisonous, for instance). John Riemann Soong (talk) 23:56, 1 December 2009 (UTC)

Depends on the source. Biologically derived molecules are usually provided in their enantiomerically pure state, and with the "unnatural" isomer being anywhere to slightly to ungodly more expensive (Because they have to be synthesized chemically). For example, L-phenylalanine from Sigma is about $390/kg, whereas D-phenylalanine is $2000/kg, and DL-phenylalanine is $430/kg (all for 98-99% purity, no extra testing/certification). For compounds which are both chemically synthesized, it depends on the starting materials. If chirally pure starting materials are available for reasonable prices and the chemical reactions to synthesize doesn't introduce/scramble any positions, entantiomerically pure compounds won't be any more expensive than the racemic mixture. The final case is where the stating compounds aren't chiral. If the synthesis incorporates entantioselective reactions/catalysts, the entantomerically pure compounds will be slightly more expensive than racemic, as entantioselective catalysts tend to be more expensive than the ones which give racemic products. If none of the previous points hold, the only practical way you can get entantiomerically pure compounds is by chiral column chromatography or by making a diastereomeric derivative. This makes the entantiomerically pure compounds ungodly expensive, as chiral chromatography columns are seriously expensive, and diastereomeric derivitization is a p.i.t.a. -- 128.104.112.95 (talk) 16:11, 3 December 2009 (UTC)