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Everything posted by CharonY

  1. For metabolome analyses we disrupt ~10-30 mg cells in 80 % methanol using bead beating. -incubation 15 min at 70° C -centrifugation -supernatant was evaporated for GC/MS: -Methoximation of carbonyl moieties: 50 μl of a 20 mg/ml solution of methoxylamine hydrochloride in pyridine, incubation 37°C for 90 min (stirring) -Protection of acidic protons: 50 μl N-methyl-N-[trimethylsilyl]trifluoroacetamide, incubation at 37°C for 30 min
  2. I stand corrected. I only had memorized that it contained two chains and I assumed that it was the results of two gene products. However, if I recall correctly the first hetereologous expressions of insulin was done by expressing both chains seperately and then combining them chemically (hence my errror).
  3. In principle yes. However the complete insulin consists of two gene products. The A and B chain have to make disulfide bonds in order to get to the correct quartiary structure. On a different point, I think nowadays yeast cells are used as hosts as they can easily be made to secrete active insulin...
  4. Granted. You have to shift the sand in 6 minutes. I wish I had first authorship on a Nature paper.
  5. Without enrichments? And to what purpose (that is, how much yield/purity do you need)? if you just want to make some PCRs on it, it might be sufficient to concentrate the water (e.g. using filters) then take the concentrate and make a general lysis (e.g. cooking, bead beating....). Otherwise you might need a cleanup with phenol. Alternatively there are some kits, but you need quite a lot of bacteria to get enough DNA (otherwise they just get lost in the columns).
  6. Or how about prokaryotes? On the one hand they got asexual reproduction, on the other hand heavy horizontal gene transfer. Here we got, well, gene pools that flow into each other so to say...
  7. Wait a tick. How was that determined (from a paper, possibly?)? And more importantly, how many of these were neutral and how many beneficial? I would assume that the vast majority should be neutral and only a fraction beneficial. As such lumping both data sets together would not allow a direct comparison with detrimental mutations.
  8. We studied together at the same university, however I never had much interested in her (and vice versa). I was (am) somewhat nerdy with workoholic tendencies and As such I never really assumed that a woman would ever play a signifcant role in my life (except being born and raised by one that is). However during nightly workshifts in the lab I found out that she was a workoholic, too. And also a nerdette (she knew all episodes from STNG from her memory, I could only counter with Monty Python), although she really did not look like one. We got interested in each other after some night sessions and have been together for over six years now. We do not have kids and are unlikely to ever have some. We do share a number of papers, though. And rabbits. Edit: forgot that it is 2006 already. Seven years together now...
  9. When I was still studying we had a course toying around with those glasses. I did not try them on, but those that did described it as Glider said. It took around 5 -25 minutes (depending on the person), if I remember correctly to readapt. If you are interested and have a library near you here are some (old) papers dealing with it (JFYI). Stratton, G. (1896). Some preliminary experiments on vision without inversion of the retinal image. Psychological Review, 3, 611-617; Stratton, G. (1897). Upright vision and the retinal image. Psychological Review, 4, 182-187. Dolezal, H. (1982). Living in a world transformed. Chicago: Academic Press; Kohler, I. (1964). the formation and transformation of the perceptual world. New York: International University Press.
  10. I have no problems with that link. Alternatively try this one http://www.mozilla.com/firefox/
  11. Einstein. I go for the destruction part, though.
  12. Well most doors are basically insulators, but some may have functions integrated into it. Probably best to ask the respective manufacturers. There might be some problems, though. Are you planning to turn off the freezer during daytime? Unless very heavily insulated heat of course will disperse across your tubings and the freezer would have to work harder (and thus emit more heat) just to keep up. In the worst case the motor might overwork. An alternative may be peltier element based coolant systems and circulate water through them. They tend to be quite expensive, though. Or what about a small air conditioner? Many of them allow an easy extension with tubings and they are meant to run constantly (as the cheap ones often do not struggle to keep a constant temp but rather a constant output).
  13. Uhm actually I do. The pocket of the labcoats here are rather large and it takes ages of rummaging through them if I do not clip my pen onto it Actually quite the reverse here. I think they stink too much. Bad: mobiles. They are pure evil. Especially if they can do everything you never wanted. Good: usb sticks. I have got tons of them. Wouldn't know how to move my data otherwise.
  14. That's actually a good example of a typical non-hypothesis driven approach that are en vogue again lately. Kind of similar to many high-throughput (but low output ) "systems biology" approaches that are running wild nowadays. What irks me a little is the money that goes into these approaches. Not that I really may complain, a part of my PhD work was funded by it (although I used it differently than I was supposed to, ah well). Anyhow as can be seen, I share Mokele's sentiments regarding the NASA experiments. They are porbably also more used as a side-aspect with which they want to spread interest into other fields. The technical necessities for full-fledged meaningful microgravity experiments done in space are probably too high to actually perform them.
  15. That pretty sums up my position, too. Especially if there is no expert board looking into the subjects, especially if one wants to create more detailed entries than available already in wikipedia. I am sorry to say this, but the majority of essays or reports written by undergrads (which supposedly are the majority here) that I get are inaccurate at best.
  16. Well, how do X and Z know that what they see is half as large as Y? Let's assume that there is an object with the length of 1 m. If asked how long it is all three will respond 1m, right?
  17. 10 times smaller than what? As stated above, without a point of reference relative measurements are meaningless.
  18. There are, in fact several elements. The main factor in Dolly was, if I remember correctly the telomere length. Human DNA is essentially linear meaning that during repication the ends might shorten (as the replication does not precisely start at the outermost base). To circuvent this problem the chromosomes possess highly repetitive regions, the mentioned telomeres which serve as a buffer for information loss. However over time the telomeres also shorten and thus might contribute to aging. Another mechanism is modification of DNA. The DNA is methylated age-dependently. This modification is usually involved in certain regulatory processes which also affect cell development.
  19. Sorry, no. Technically it is a new strain, but same species (DNA : DNA hybridization is clearly above the threshhold). This may seem like nitpicking but this time no technology exist to curate the genome up to a point that allows creation of a new species. Well, technically there is a way (for bacteria) but it would simply involve taking a genome with large accessory genetic elements and cure them all. But my point is that atm we can only manipulate existing cells (to quite some extent, though), but we lack the ability of creating something completly de novo (as I assumed this thread was about), nor will this be possible by purely concentrating on DNA.
  20. Actually it doesn't look like she is not aging. She is only arrested in her development. One should not confuse aging on the cellular level with maturation. In another report I read that they did not find any obvious chromosomal defects/differences btw.
  21. Ugh you made me trying to remember stuff from my student days. In general ecological simplification means a reduction of function, complexity and structure of a system. - Reduction of function is the case if certain ecological processes/flows are disrupted. Examples might be carbon or nitrogen cycles. The nitrogen cycle for instance can be disrupted if for instance there is a significant loss of ammonifier/denitrifiers or for instance nitrogen fixers. Or plants using immobilised nitrogen and so forth. This is often coupled with -reduction of the complexity of the system, meaning the loss of elements (usually species) in an eco system. Every species plays a specific role in a given ecosystem and as such a loff of them reduces both, complexity and function of a system. Finally there is -reduction of the structure of a system. A higher structural complexity is characterized by higher diversity and variations of habitats in a given system.
  22. Possible but only the far far future. Getting sequences is comparatively easy now. The identification of genes from this sequences is still rather tricky (especially for eukaryotes). Assigning functions to these genes extremely complicated. Even in well known, very basic bacteria like E. coli the amount of genes coding proteins of unknown function is around 20-40% at least. Then we do have intergenic regions which apparently do have a function (e.g. in regulation) but is nigh impossible to detect them as we know very little about it. Then of course there is the problem that not everything is determined genetically. That is, you also have to consider at the very least the cellular environment and then it gets really complicated...
  23. I fear you have started with slightly wrong definitions of evolution. First, evolution can be defined as a change in allele frequency in a population. Or a bit simpler, a change of the gene pool over time. There is no direction in this change per se (or at least one cannot infer it). There only has to be a change which is then described as an evolutionary event. Now, mutations are one of the mechanisms which can lead to evolution. So in theory every mutation changes the gene pool a bit. However, most are lost or at least do not spread and therefore do not contribute to any lasting effects on the gene pool. Mutations alone however are in general considered randomised and by their very nature cannot give evolution any direction (or as you put it, "start a new phase"). So if we got mutations as the only mechanism, the only way evolution might happen is by a rapid accumulation of mutations. Now another factor comes in: natural selection. You assumed that However, as I pointed out above, a change in the gene pool is evolution already. The only thing that selection adds is a direction. By no means does it mean that the gene pool might get "better" somehow. It only means that it forces the gene pool to adapt to these selective pressures. So in selective sweeps and also random events mutations will either get lost or persist in the gene pool (loss of already established alleles in a gene pool is evolution, too btw) and thus contribute to evolution. The frequency (or likelihood) of a certain mutation (or allele in general) to get established in the gene pool is a function of its frequency (how often does this mutation occur in the population?) and its effect on the fitness of the individuum (increasing/dcreasing/being neutral to reproduction chances). Now that being said do humans prevent mutations? NO of course not. Mutations are a mechanisms that happen all the time, we have no way of preventing it. So the human gene pool is and will continue to be subjected to mutation events. However some mtuations that are detrimental can now be diagnosed. Now if we assume that all foeti with this detrimental alleles are aborted, do we stop evolution? Of course not. We simply add a selective pressure on the certain alleles. Everything we do just changes selective pressures, but we do not and can not eliminate them completely. There are always some individuals with a higher fitness (higher reproductive chances) that are based on genetic elements. Sexual selection for instance will always work. A change in life condition can also dramatically change selective pressure. For instance let's assume that a thousand years ago being atheletic was a prerequisite to reproduce. Nowadays assume that it is less so. Therefore alleles contributing to an atheletic build will have less impact on fitness and the frequency of it could in theory decline. This too is evolution. In contrast nowadays literacy is very important. So if we assume that there are alleles that prevent literacy (assuming there is such an extreme form of dyslexia that has a genetic basis), they might have been abundand thousands of years ago (few selection against it) but nowadays it is likely that the frequency is lower, due to the higher selective pressure. And lastly I want to point out that humans are adapted to the given environement (and yes also the ability to change the environment is and adaptation) otherwise we will have died out already. So what I wanted to say with this long post (for which I now have no time to check for spelling errors atm, my apologies) is that while human societies do change selective pressures, there is no way that evolution per se can be stopped.
  24. During (aerobic) respiration reactive oxygen species (ROS) are formed (e.g. by the Fenton reaction). Of these hydroxyl radicals are probably the most reactive ones. The more agressive species directly act on e.g. proteins, DNA and lipids causing aggregation (cross-linking), fragmentations, deletions etc. In fact it is a kind of corrosion, as in most cases corrosions are simple oxidation reactions, too. Antioxidants however, either prevent the formation of these ROS or directly detoxify them. As such it is believed that antioxidants should help preventing cell damage (and thus aging), but I am not sure how large the impact of the intake of antioxidants really is. The body of course produces a number of enzymes involved in detoxification (e.g. catalases, peroxidases and superoxide dismutases..).
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