donkey

wow, i'm surprised this poll is so one sided I said yes but like any good scientist I was verging on unsure I think my hesitation was due to the wording of the question. I would have prefered "Do you think like exists elsewhere in the universe" and I would answer "probably, yes" to that. k, i'll shut up now

i love the new touches, now just need to subtly change the other buttons (quote, edit etc)

have fun moving

lol, i'd always say -50 but that's an interesting point

hey, I'm happy to help I finsihed my exams for university a couple of weeks ago so have quite a lot of spare time and i'm enough of a geek to enjoy this Lodish et al (5th edition, p725) has some good details. So it looks like PC3 endoprotease, PC2 endoprotease and carboxpeptidase remove all the unwanted amino acids to convert proinsulin to insulin. the online version of an earlier edition of the book (slightly different wording but similar info) is here: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Search&db=books&doptcmdl=GenBookHL&term=endoprotease+proinsulin+AND+106720%5Buid%5D&rid=mcb.section.4846#4850 hope that helps oh and i'm from the UK (Edinburgh), 22, male and an undergraduate biochemistry student What about you?

I *think* it'd lower the pI if you add a negative charge because this page (http://www.rit.edu/~pac8612/webionex/website/html/ione8zvy.html) says "when the pH > pI, a protein has a net negative charge and when the pH < pI, a protein has a net positive charge". So it might be that in general a low pH allows proteins to be more positive and the addition of an extra negative charge would mean that it wouldn't have an overall positive charge until at a slightly lower pH compared to before. Similarly it would also have an overall neutral charge at a lower pH and thus the pI would be lower. So, my guess is that adding a negative group would lower the pI.

If you add a negative charge i'd imagine that would stabilise the protein in water (negative charges interact with water) - therefore, i think adding a negative charge would make it more hydrophilic and less hydrophobic. I'm pretty sure that adding a negative charge would also affect the pH at which the protein's charge became zero (i.e. it's pI) but i'm not totally sure whether you'd need to increase the pH (i.e. increase in the pI) or decrease it. umm, hopefully someone else knows...

hey Matilda, Last night it was late and so I thought I better check my text book to make sure I wasn't talking nonsense. I have checked (Molecular Cell Biology 5th ed., Lodish et al, pp673-675) and it confirms that "the tripeptide sequences Asn-X-Ser and Asn-X-Thr (where X is any amino acid except proline) are substrates for oligosaccharyl transferase, the enzyme that catalyzes this reaction". When it says this reaction it's refering to the transfer of a carbohydrate polymer (i.e. a precursor oligosaccharide - this is a "precursor" because it's later modified in the ER and Golgi apparatus) from a molecule called dolichol to the protein as the new protein is translated and translocated across the membrane of the rough ER. Dolichol is essentially a holding molecule and sits in the membrane holding the carbohydrate waiting for the new protein. So the answer is that oligosaccharyl transferase decides which amino acids get N-glycosylated. Here are a few links that might be helpful: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Search&db=books&doptcmdl=GenBookHL&term=oligosaccharyl+transferase+AND+373563%5Buid%5D&rid=mboc4.figgrp.2351 http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Search&db=books&doptcmdl=GenBookHL&term=oligosaccharyl+transferase+AND+373517%5Buid%5D&rid=mboc4.section.2202#2230 http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Search&db=books&doptcmdl=GenBookHL&term=oligosaccharyl+transferase+AND+373496%5Buid%5D&rid=mboc4.figgrp.2232 edit: that's quite strange, my 2nd post was exactly 12 hours after my first

are you talking about N-liked glycosylation? Carbohydrates are attached to asparagine residues present in the tripeptide sequence Asn-X-Ser or Asn-X-Thr, where X can be any amino acid (except Pro). I'm not exactly sure why this is off the top of my head but it's possibly due to an enzyme mediated reaction which only recognises specific amino acid sequences. In other words, it may be that some amino acids get glycosylated, while others don't, because enzymes involed have specificity for particular AA sequence. I'd like to stress that that's just my guess so you'd really be better off consulting a text book.

loving the new style

yeah it's not exactly clear what yeild it wants. good luck!

hopefully someone else will reply to confirm/correct me as I'm doing this from memory and I've never actually had any real life experience with this stuff (i'm just an undergraduate) but I think the following is correct. ok well my understanding is that your % yield is 30% (7.5/25 x100) Basically your total activity is directly proportional to the amount of protein A you have. Therefore if you lose some of your target protein (protein A) you lose activity as has happened. Therefore you yield goes down. It should simply be a process of working out how much your final amount of protein A is compared with the initial amount. This can be worked out using the activity, what % of final total activity do you have compared with your initial amount? I've calculated that above to be 30%. --- I think your final purification factor is 15. I assume this basically means how pure is the final sample compared with the original, crude, sample. So again, your total activity is related to the total amount of protein A you have. So in the crude extract you have 500mg of protein containing protein that has 25 units of activity. In your final one you have 10mg containing protein that has 7.5 units of activity. In other words, in the crude extract (500/25 = 20) 20mg would contain enough protein to give a total activity of 1 unit. In the final extract (10/7.5 = 1.333) 1.333mg would contain enough protein to give a total activity of 1 unit. Therefore it's easy to see that 20mg is a lot more than 1.333mg (i.e. it's less pure - it has other material there). In fact it's (20/1.333333333333333 = 15.0) 15 times more mass for the same activity. Therefore it's 15x less pure. So you could say that the final sample has been purified 15x compared to the crude extract. --- As far as I understand it, specific activity is simply units/mg so that's be 7.5/10 = 0.75 for the final sample and it'd be 25/500 = 0.05 for the crude extract. Again it's easy to see that 0.75 is 15x as large as 0.05 confirming the purification factor. hope that makes sense/helps

ah cool - interesting stuff I'd be inclined to say that that would be molecular biology (as opposed to biochemistry) or at least something that'd be used by molecular biologists. Obviously I don't know what it's like to design such things and drawing distinctions between biochemistry and molecular biology isn't an easy thing to do so I should probably shut up .

lol, awesome post does he like it?

hey, there's actually a category called "Biochemistry/Genetic Engineering" (just above General Sciences in the forum index). I'm currently an undergraduate biochemistry student and find it very interesting. I can't really tell you too much about the profession as I've had no first hand experience but you'll need a degree and possibly a PhD if you want to go far in teh field. As far as I can tell there's a few routes you can go down with a biochem degree. You could either go into academic research where often you'll be based in a university doing research to advance our knowledge in a particular area. An alternative is to work in industry for say, a biotech company or a drug company. These will often have a medical slant although not always, for example, you could work for some GM crop company or many other applications of biochemistry. You could try checking out some universities and maybe emailing their biology departments to ask the lecturers what a career in biochemistry is like. Normally they're very friendly and happy to help

I think he's talking about the RNA world hypothesis. Basically the theory suggests that RNA - which is known to have some catalytic activity as well as, of course, genetic storage capabilities - was the precursor molecule at the origin of life. It has been suggested that RNA molecules could use itself as a template and catalyse the duplication of itself. Then DNA and proteins came along and took over the storage and catalytic roles of RNA, religating it to a messenger and a few other niche roles. see here for details: http://en.wikipedia.org/wiki/RNA_world_hypothesis

of course most identical twins share a similar environment but I think the largest IQ difference between identical twins ever recorded was around 19 points (and the norm being much closer). That said, it's clear that the environment has a huge impact and without a proper environment, people will never come near their maximum potential IQ.

that'll bring a country to it's knees!

I've had deja vu quite a few times. Often i'll think woah - this has happened before but I wont be able to say what comes next but as time progresses it'll feel exactly like it should do (and how i then "remember" it). The most amazing times was when I was really young and I went to see a kids play as a family and at one point during the play my identical twin brother and I turned to each other and said "didn't this happen before?" to each other. Both of us had deja vu at the same time! what's that about?

22/m/UK

yes it's very potent but it's not very stable, by the time it gets from the reservoir into the pipes it'll have broken down.

First off this thread is pretty sick, i hope you're just thinking of ideas for some dystopia story If you're interested in committing genocide and killing 1/2 the world's population for their natural resources, why not just use more traditional chemical / biological warfare? I can't see prions being an effective weapon. I guess with traditional WMDs there may be a problem with contaminating the country.

doesn't look like it

yay, glad to hear you got it sorted sorry, I'm more used to yields in % and didn't even think about anything else.

sorry, you've got me stumped! hopefully someone else here will have an idea although I appreciate you're running out of time good luck!