Wikipedia:Reference desk/Archives/Science/2015 May 28

= May 28 =

IIT JAM
SHOULD I TRY TO IIT JAM PHYSICS IF MY NUMERICAL PHYSICS IS NOT VERY GOOD BUT THEORITICAL IS BEST??101.62.252.146 (talk) 07:28, 28 May 2015 (UTC)


 * Do you mean this sort of thing http://www.iitg.ac.in/jam2015/pdfs/PH_QP.pdf - if so i'm afraid it is almost entirely numerical (and easy) Greglocock (talk) 08:28, 28 May 2015 (UTC)

Notes on B.Sc.Agriculture
I hope this is the right place to ask. I couldn't find or how to find any relevant sites for B.Sc.Ag notes, sites for free downloading text books regarding the subject. Anyone knows such sites. Please share. There are also whole list of agricultural college, I wanted to know if any provides recorded video lectures, notes or just anything about B.Sc.agriculture study materials. Also, people talk about mit opencourseware and other, how help myself from it... Please help... :)

Thanks,

Learnerktm 08:25, 28 May 2015 (UTC)


 * You can try here. It does say "The portal is accessible to all Faculty, Teachers, Students and any one interested in the field of Agriculture and Allied Sciences" although I have no idea what you can access for free. The home page for all their courses is here. The MIT open courses website is here but I can't find an agriculture course - not every university will run an Agriculture course and it doesn't look like the do one. There are lists of free online Agriculture courses here and here. Richerman    (talk) 08:54, 28 May 2015 (UTC)

Starling bill colour
According to common starling, a starling's bill changes colour during the year. What mechanism achieves this? Does the bill "grow" and the colour spread from the base to the tip? Or is the colour infused into a static bill somehow? -- SGBailey (talk) 08:26, 28 May 2015 (UTC)


 * This paper relates the yellow colour in the breeding season specifically to the hormone androgen, although without a mechanism. Mikenorton (talk) 12:25, 28 May 2015 (UTC)


 * Interesting. Thanks. -- SGBailey (talk) 12:32, 28 May 2015 (UTC)


 * Thanks, I was wondering exactly the same thing myself. μηδείς (talk) 01:29, 29 May 2015 (UTC)

Is amino acid folding unweightedly random?
This is going to be a bit of a strange question, due to nearly complete ignorance of the writer in this area. I ask to settle a dispute with a friend.

Presupposing an environment where all amino acids were present and without external guidance by a cell, etc. does every protein that could form from the acids have an equal chance of occurring? To phrase it simply: do amino acids have a "preference" for certain configurations over others?

Can the probability of a protein's formation without biological or other guidance be calculated by 26acid iterations or some other simple fashion? Mr.Magik-Pants (talk) 19:08, 28 May 2015 (UTC)


 * I did a simple web search for "random polypeptide" "inclusion bodies" and instantly summoned up, which says what I would think: "Proteins can fold in reasonable times (typically from 10E-2 to 10E3 seconds) because they do not search blindly through this enormous phase space [of all possible secondary structure and tertiary structure]. Guided by locally favorable energetics, they first form secondary structures, and then assemble in a more or less straightforward way to a final configuration.  In contrast, random polypeptide chains often have multiply degenerate ground states with radically different configurations [i.e. they can fold more than one way].  Even ones that have a unique free-energy minimum tend to fold slowly, becoming trapped for long times in metastable structures far from the ground state.  Naturally occurring proteins are probably a special subset of all possible sequences of amino acids: those that fold swiftly and consistently to a single lowest-energy state."  (it goes on to explain that proteins that don't fold correctly tend to get caught up in inclusion bodies) Wnt (talk) 19:56, 28 May 2015 (UTC)
 * This is what I would think, too. Thanks a bunch. Mr.Magik-Pants (talk) 21:16, 28 May 2015 (UTC)


 * Based on the wording of the question (which contradicts itself several times), I don't think you clearly understand the distinction between the amino acid sequence of a protein, and the way it folds in 3D. They are quite different things.  The confusion makes it hard for me to understand what you are asking.  When you ask, "does every protein that could form from the acids have an equal chance of occurring", are you asking about every amino acid sequence or every 3D folding structure? Looie496 (talk) 20:43, 28 May 2015 (UTC)


 * Sorry for being so confused. I think I'm talking about possible sequences, but it makes sense that not every sequence could fold, which is the answer I think I was driving for if that makes sense .Mr.Magik-Pants (talk) 20:53, 28 May 2015 (UTC)
 * Alrighty, I'm going to try to clarify my question. With a random chain of let's just say the 26 core? main? most common? amino acids, is it more likely that the chain will fold into a natural protein or more likely the the chain will not fold or not fold into a natural protein? Mr.Magik-Pants (talk) 21:35, 28 May 2015 (UTC)
 * I don't know where you get the number 26 from, there are 20-23 basic amino acids. Anyway, a random chain will definitely fold in some way, but the chance that it will resemble a natural protein is extremely small. Note also that while folding occurs naturally because it is energetically favorable, there are also special proteins called chaperones which help other proteins fold into the proper shape. - Lindert (talk) 22:15, 28 May 2015 (UTC)
 * Actually, most random protein sequences likely don't have any sort of defined folded structure. They're either intrinsically disordered proteins or they're arbitrarily sticky and will agglomerate into amorphous blobs. Then there's a whole class of amyloid proteins which have semi-regular structure, but not in any sort of "well folded" fashion. Well folded proteins are a small subset of total protein sequences. -- 160.129.138.186 (talk) 23:53, 28 May 2015 (UTC)
 * The number 26 is merely a product of misrecollection. I guess I was close though. Mr.Magik-Pants (talk) 23:12, 28 May 2015 (UTC)
 * The OP may be interested in reading Protein structure prediction which is basically the entire field of study which covers all of his questions. WP:WHAAOE.  -- Jayron 32 23:45, 28 May 2015 (UTC)