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Everything posted by Bioc

  1. Hi, need a little help here. If you are assaying the pressence of a protein during several stages of development of an animal, and you see that, let's say, P1 and P8 have two bands (let's say P0 is the embryonic stage and no protein iband is seen; and the latter stages are P1 to P9) and the rest (P2 to P7 and P9) one band. What is the most probable explanation to this? And how can you verify it? This is what I think: 1)the antibody is recognizing more than one epitope (not very specific) or 2) there is a protein with a very similar epitope (not really think is probable, also relates to 1) in some stages or 3) the protein is an oligomer and it is cleaved in some stages (early and adult). I think 1) is the most probable and I would verify it isolating the lighter protein and re-doing the western blot. If it's positive, then the antibody is not very specific. Any help would be apreciated, hope you can understand me.
  2. Because I recrystallized acetanilide in a water:ethanol mixture (30:1), then filtered it and washed it with 95% ethanol, trying to remove residual water. Thing is, I lost like 70% of solid, so I was (am) kind of in denial, but I think is the only explanation. (btw, It was a test).
  3. Hi, is acetanilide soluble in cold ethanol (~20ºC) ? I found it's about 18g/100ml, but is not a reliable source. I'm asking because maybe I did somenthing stupid...
  4. hum, as far as I know this kind of transformation is to obtain a linear graph, so dy/dx should be the slope. No idea what would happen to the error, tough.
  5. I think wikipedia puts it that way because you are calculating the pH. If you use Kb and [OH-] then you are calculating the pOH. Anyway, pH +pOH = 14, so it must be a convention thing.
  6. Hi, since I infer you precipitated silver with an halide, here is a link where you can get some info: http://employees.oneonta.edu/kotzjc/LAB/SilverGroup.pdf The question is not that hard, don't give up!
  7. Hi, I was wondering why the nitration of acetanilide requires the use of sulfuric acid AND acetic acid. I understand that the acid medium is used to solubilize the acetanilide, so why is concentrated sulfuric acid alone not enough? On a side note, the sulfonitric solution is prepared in another tube and later added to the acetanilide mix. As far as I know, the use of glacial acetic acid is to keep a low percentage of water, and thus, prevent hydrolysis, but this can be achieved using only the concentrated sulfuric acid. So, why is (glacial) acetic acid needed?
  8. Bioc

    DNA Extraction

    Mmmm, a single phase heavy on ethanol makes more sense to me. I saw in a webpage that if you pour cold ethanol slowly, then two phases can form, but that wouldn't explain why would the DNA and the Na+ ions diffuse to the alcohol layer and form the precipitate. I am talking about the simplest form of the experiment btw, the one you can do in your house . None of the websites I have seen mention the use of something to break the wall, so detergent must be enough to atleast cause leakage of the cell material. This is one of the websites I checked: http://learn.genetics.utah.edu/content/labs/extraction/howto/
  9. Bioc

    DNA Extraction

    Hi, I saw this type of experiment on the net, and I don't get a few points. I'm talking about the experiment where you lyse a sample (peas, meat, etc) with a blender, then add detergent and salty water, and finally add alcohol to the mix to precipitate the DNA. What I don't quite get about this experiment is how can alcohol (ethanol) and water form two phases, since ethanol is soluble in water. I think maybe is because the water molecules are solvating the salt and the detergent. Also, in the case of plant cells, I'm not really sure how can detergent break the cell walls. Last, how can salt help precipitate DNA? I know that DNA is negatively charged, it occurs to me that it has a higher affinity to Na+ ions than Cl-.
  10. Can we see it? (with names and other sensible data removed) And trying to answer your question... As far as I know what they test is if the alelles (traits) of specific loci (specific sites of the DNA) are shared among the possible relatives, but people not related can have the same alelle by chance, so this must be backed up with statiscal significance, therefore maybe the matchs you saw are not statistically significant. I don't know why they required the race of some and not yours.
  11. Bioc

    A Idiots Idea

    A while ago I saw, in the TV, a woman that was blind, and had some glasses with a cam plugged directly to the brain so, at least in the optics field, some research have been done
  12. In a few words, coupling phosphate bond to substrate molecules makes the substrate more reactive, because as your friend said, phophate bond are high energy bonds (their breakage is exergonic), also the phosphate group is a good leaving group.
  13. Well, the water does taste different after you let it "breathe", at least in my opinion.
  14. Thanks for the reply, the context was something like why it is important to use a loading control when you are using a western blot in an experiment using differential protein expression. I assumed it was about using protein expressed with different concentrations or something like that, so looks like I wasn't so wrong.
  15. Well, it's not really an accident, but one day I was doing a precipitation titration (fajans method). Thing is I was titrating and my buret needed more titrant solution, and the instructor thought it was a good idea to watch me refill it (made me nervous), so I grabbed the flask and carefully added it into the buret, only to find it was the flask containing the analyte solution. Result: buret full of beautiful precipitate. Instructor facepalms. Try to wash buret to re-use (derp) "why are you going to wash it NOW? why don't you use another one instead?". She hated me.
  16. Hi, I have searched, but only found it's applications, so I was wondering if someone can please explain me what that is.
  17. Hi, from personal experience I haven't seen too much people eating lemon when they're drunk, when they do it is more likely because they are on the table next to the tequila hahaha. What I have seen, tough, are a lot of myths regarding alcohol and food, and I asume those myths vary from culture to culture.
  18. But how can you know that the remaining 99% are not producing molecules that inhibit quorum sensing?
  19. Hi, the Mann-Whitney is the non-parametric alternative to the t-test. Since they told that there is a significant difference between the effects of X & Y on Z, when the concentrations are high enough, I think there is enough evidence to reject the null hypothesis;at low concentrations there is not enough evidence to reject the null hypothesis (hypotheses are never accepted, only rejected or non rejected).
  20. Mmm well you add saturated table salt, so when you are done heating, the solvating capacity of water becomes lower. Or maybe it means that when you are done shaking you have to let the suspended particles decant. When I was at the lab I just added saturated salt water until the emulsion broke, then proceeded to separate the phases, but I don't remember seeing a precipitate (I was extracting plant pigments, though).
  21. Bioc


    Hi, I don't need too much detail. In the organic lab we get a H-NMR and a C-NMR spectra of the compound being synthetized (previously done by the teacher), but I wouldn't categorize it as an advanced course. What I have to do is assign the chemical shift, multiplicity and integration of each hidrogen; as for the C-NMR I only have to assing the chemical shift to each carbon (C13-NMR and DEPT). My real problem is right know I don't have that much time to search for information, so that's why I ask you guys if you know some books of NMR for dummies hahaha.
  22. Bioc


    Thanks!, I'll check the Wade's book. PD: If someone is also studying the same subject, I found this H-NMR predictor: http://www.nmrdb.org/predictor
  23. Bioc


    Hi, I need to learn how to interpret NMR, specially C-NMR. Thing is, I'm having a hard time trying to understand it, specially NMR of aromatic compounds, asigning each H/C of the molecule to the corresponding peaks. I'll really apreciate if someone can suggest me a website or a book that explains it.
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