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Everything posted by Horza2002

  1. That paper is an interesting read, but remember that carbon-14 is continously being generated in the atmsophere by the action of cosmic radiation on nitrogen atoms. So not all of the carbon-14 observed in the sample would have come from the nuclear testing.
  2. I personally have no problem with him being killed; he has got as good as he gave to the rest of the world. As has been pointed out, he was given the chance to surrender but he didn't take it. Lets not forget that this man is responsible for the murder of thousands of innocent people. If he had been tried he would have been executed anyway. I think it also points out that, no matter how long you hide, justice will be done eventually. As for dumbing the body, as ajb has pointed out, it prevents a "terrorist Mecca". Yes they could do it anyway somewhere, but its less powerful if the body is not there.
  3. To help make this easier, the mechanism is below. You are right that typically, a halide would be displaced by the hydroxide because they are reasonable leaving groups. However, the carbonyl groups makes the protons in the alpha position more acidic...the hydroxide can then deprotonate it to give the enolate which then reacts further with the halogen. Now, at his point (the prdouct of step 2) the prescence of the iodidine on the alpha position makes the two remaining protons more acidic because of its electron withdrawing capabilities. This means that a second proton is deprotonated faster than than a substitution reaction can occur. The last proton is then again easier to remove because the resulting anion is stabilised by the two iodides. If you were to actually do this reaction however, you would normally use three equivalent of a sterically hindered base (e.g. potassium t-butoxide) to get you through steps 1-6 and then at this point add in the hydroxide. Because even though the major product will be what you expect, there will always be some side reactions...and remember that alpha-halo carbonyl compounds are more activated to substitution reactions because of the overlap of the C-X (X is a halogen) sigma* and the C=O pi* makes them more reactive.
  4. Erm, well that would depend on the level of understanding that you want to get. Physiotherapy, I would say, would require biology which you say he is already doing. If he then wants to understand the background of the biology, then I would recommend doing chemistry as well. The chemistry will help explain a lot of areas of biolgy where you are normally expected just to accept it.
  5. While yes, iodode methane is very very nasty...its is toxic and carcinogen. The MSDS is in the link below: http://msds.chem.ox.ac.uk/IO/iodomethane.html However, as mississipichem has said, it is not a stable molecule. In the C-I bonds are very weak and so are undergo photolysis very easily. Not only that, but iodomethane is a good electrophile..so much so that it will react with water reasonably quickly to give hydrogen iodide and methanol. So overal, no I wouldn't be worried at all.
  6. Is this so that you can do PCR on your sample? If so, then the primer that you have, are about 20 base pairs complimentary to the 3' and 5' end of the DNA strand. So once you have added your primers to the DNA sample, it will anneal to each end which provides a "handle" for DNA polymerase to bind and replicate the DNA strand. Is that ok?
  7. Hi all, A few months ago, I posted about the use of IBX as an efficient oxidant to oxidise primary and seconday alcohols to aldehydes and ketones respectively. I've since found another use this, the efficient oxidation of primary alcohols to carboxylic acids without the need for transition metals. http://pubs.acs.org/doi/abs/10.1021/ol050875o In Situ Generation of o-Iodoxybenzoic Acid (IBX) and the Catalytic Use of It in Oxidation Reactions in the Presence of Oxone as a Co-oxidant This method is as good as the method for aldehyde oxidation. Using acetonitrile:water as the solvent, heated to 70oC, there is complete conversion to the corrosponding carboxylic acid. And, like before, simply cooling the reaction down to 0oC to precipitate out the IBX is all that is required for a work up....when I have done it, I have often found that running the crude filtrate is passed through a short (about an inch) of silica gel gives 95% yield clean by NMR. Theres the added bonus, as decsribed in that paper, is that u only needed catalyitc IBX and use Oxone to get good yields. I have used this method myself a lot recently, and it is very good. I know there are alot of methods to do this, but this is by far the easiest oen I have found so far. Just thought I'd share this with you all again as a follow up to the IBX aldehyde oxidation method.
  8. Would it not be easier to sequnce its 16s DNA and identify it that way?
  9. Can you give a little more detail on what you want to do? What concentration of what are you trying to measure? How are you going to measure it? What equipment do you have?
  10. Getting back to the topic....why do you think cancer is easy to cure and yet after all these billions of pounds/dollars the big pharams have not come up with it? I have some experience with workign with cancer drugs, the killing the cancer cells is not the problem with most new drugs, it is the side effects that are the problem. The high levels of cytotoxicity that are required for cancer treatments is what needs to be channelled so that it doesn't harm health cells. There are a wide range of natural products that can do tis very well and in very interesting ways.
  11. ...that questions doesnt make sence... From what you've said, I think you mean which of the reactions that are catalysed by these enzymes is dependant on xontrolling the amount of enzyme. If thats the case, then I would go find out what reactions they are and how they are performed.
  12. Have you tried doing a Scifinder search? Thats looks very simpe to make, you just need the diamine and an oxidant. There are a number of people on this site that are synthetic chemists. While I wouldn't consider myself an expert, I can certainly give you some good ideas about things.
  13. Organisms can't change their DNA so that they are perfectly adapted to the enviroment they are in. All mutations do is provide an alternative to a current characterists (e.g. colour of fur). If this happens to be better than before then its good, if its not then it tends not to be spread amongst the population in further generations. Just remember though, that a lot of mutations are "silent". The change in the DNA sequence has no effect on the characterisic (point mutations)
  14. The exact sequence of nucleotides gives you the sequence of amino acids that a particular gene codes for. There are very simple tables that convert the codon into the amino acid for you; go to RNA codon table in the link below. http://en.wikipedia.org/wiki/Genetic_code It is then the resulting protein that gives all the effects (good and bad)
  15. In biological systems, a large portion of thiols (e.g. PKS and FAS systems) is deprotonated. Thiols are more acidic because the sulphur based anion is more stable because it is a larger atom than the corrosponding alcohol.
  16. Another way I have found works very well is to azeotrope the sovlent off. Once you have the majority of the solvent off, add in some diethyl ether and it helps remove the last of solvent. Works very well for ethyl acetate. You can also use this method in sequence to get rid of water from a sample. Dissolve the sample in toluene and remove under vacuum removes the water. Then added ethyl acetate to get the toluene off, then added DCm to get the ethyl acetate off and then add ether to get the DCM off. Its a rather long winded approach but it certainly works.
  17. To be honest, I rarely bother getting all the last remaing of solvent out of my compounds (except final compounds). Unless of course that solvent is going to cause problems....like having chloroform in the presence of BuLi is really just asking for trouble. You can also just flash freeze them....that works well on the rare occassion I actually get a solid
  18. Not all compounds will be solid or crystals. In fact, all of mine are oils. Alternatively, you have a miniscule amount of solvent trapped in the material and so it doesn't crystalise
  19. The vast majority of chemistry short hands are for certain functional groups e.g. the BOC group, CBZ, Fmoc....these are all protecting group. The problem is that if you simplify a benzene ring any further, you lose the information of the positions of the groups around the ring (e.g. where they are). I would basically advice you to become very good at drawign hexagons. Alternatively, invest in chemistry stenciles...
  20. It will depend on what atom you ar lookign at and to which orbtials you are actually filling. S-orbitals are indeed spherical about the nucleus, but p-, d-, f-, etc orbitls are not. If they are not all symmetrically filled, then the electron density around the nucleus will not be. I.e. if you onyl fill the px and py orbitals, then there will be no electron density in the z-plane. Another example is that of cobalamine (otherwise known as Vitamin B12). During its reaction cycle, the central cobalt atom exists as Co(I)...the unpaired electrons are in the dz2 orbitals which points in one direction only...in this case, the atom electron density would not look spherical. Id also should point out that the planets are not spheres....they are squashed slightly and bulge and the equators. Also remember that the electrons are not orbiting an atom in the same sence that an planet orbits the sun (and again for very differenet reasons).
  21. Will you need to actually perform any experiments that you propose? And what areas of biochemistry are you interested in? One possible idea could be working out how to isolate/detect the intermediates in PKS biosynthesis....the ones that remain covalently attached to the enzymes via the thioester linkerage. As far as I'm aware, not many of these intermediates have been observed and the majority of them are only proposed structures.
  22. Will you need to actually perform any experiments that you propose? And what areas of biochemistry are you interested in? One possible idea could be working out how to isolate/detect the intermediates in PKS biosynthesis....the ones that remain covalently attached to the enzymes via the thioester linkerage. As far as I'm aware, not many of these intermediates have been observed and the majority of them are only proposed structures.
  23. More than likely yes, it is simply the air that is trapped in the polymer mesh being released as the polymer dissolves.
  24. The mesomeric effect (otherwise known as resonance stabilisation) is a through bond stabilisation. It uses the delocalised pi system of a molecule to stabilise anions, radiclas and also cations. Hyperconjugation is a through space effect in which the bonding electrons of alpha-C-H or C-C bonds are donated into an empty/partially empty orbital. This means that this only stabilises cations and radicals; it infact destabilises anions. Think about the stability of a tertiary, secondary and primary anion; the tertiary is least stable. In the majority of cases, I would say resonance as a more profound influence on the stability of an charged specie than hyperconjugation. I say this because I am not aware of any anions or cations that exist in water that don't use resonance stabilisation. If you were silly enough to add butyl lithium (essentially the butyl anion) to water, there would be a large explosion with a nice red tinge to it. However, methyl blue, http://en.wikipedia.org/wiki/Methyl_blue, is a carbocation that is perfectaly stable in water resulting from the extensive delocailsation of the cation.
  25. I think there thinking here is that if you wear gloves all the time, you get complacent and think the gloves will protect you whatever you do. Lol did you make him wash the calcium hydride up in the sink as punishment? At least it wasn't sodium hydride, you could have had some more serious issues with that. Thats actually lucky really, out of the most common hydrides, caclium is the least reactive...not to say its harmless though.
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