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I am taking an online course in image analysis and have been asked to use the attached image to determine the size of the SARS-S protein of the SARS-CoV relative to the total of its proteins. However, I have been given no explanation of the image, and with a physics background, I simply do not understand it. Can someone please explain the image (specifically the SARS-CoV column).

enter image description here

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    $\begingroup$ Biology is more suitable for this, I think. $\endgroup$
    – orthocresol
    Apr 28 at 17:11
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    $\begingroup$ @orthocresol, I tried but they said that they don't help with homework (although I am not asking you to solve the problem - simply to help me understanding the image). $\endgroup$
    – JKalle
    Apr 28 at 17:12
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    $\begingroup$ Hmm. This is a tough case. After all, Chem.SE has a similar 'homework" policy; and although I can understand your point, it may or may not be that other users will be sympathetic towards it. I think it could also logically be closed as being off-topic (i.e. not about chemistry). To be entirely honest, the root cause of the problem is that you're given an image without any context whatsoever, and asked to interpret it. That seems like an unrealistic expectation to me, and even though you may happen to find an answer on SE, it seems to me that that'd only be a one-time, superficial fix. $\endgroup$
    – orthocresol
    Apr 28 at 17:19
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    $\begingroup$ It's been a long time since I did biology, but I think I can at least point you in the direction of the Western blot and gel electrophoresis. Wikipedia might not be the best resource on this. You might be able to find other easier explanations elsewhere on the Internet. $\endgroup$
    – orthocresol
    Apr 28 at 17:20
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    $\begingroup$ The Western blot looks similar to the image, so I will try and read about that. Thank you for trying to help, @orthocresol. $\endgroup$
    – JKalle
    Apr 28 at 17:26
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Although this is a homework question, I also think OP deserves a help as orthocresol suggested. I'm not going to go into details but leave it at orthocresol's suggestion of this being a Western Blot of protein analysis, which is absolutely correct. Hence, OP should start reading of electrophoresis and western blots techniques since, I assume, s/he taking molecular biology class.

In brief, the given image is a X-ray photograph of the nitrocellulose membrane after transferring the proteins from the SDS-PAGE gel (after electrophoresis). I'm suggesting that because the image looks like visualized by radioactivity (I suggest OP to read about these techniques in details to understand). In SDS-PAGE gel electrophoresis, the proteins separated mainly by molar mass of each protein while heaviest protein go first since electric current run from top to bottom as sepicted in following diagram:

SARS-CoV-2

As marked in the diagram, SARS-CoV consists of SARS-M ($\pu{20 kD}$, SARS-N ($\pu{54 kD}$, and SARS-S (~$\pu{175 kD}$ proteins. I may give you your answer but I strongly suggest to read about the subject for better understanding. I do not support online courses, but there are no choice you can made during a bad pandemic era.

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    $\begingroup$ I am not taking a class in molecular biology; it is supposed to be a class in image analysis with a focus on using the software, not understanding biology (we have also analyzed pictures of faces, traffic, etc.). It is online because the university is shot down. You say SARS-CoV consists of the three proteins you indicated with a red line, but what are all the small lines in between? $\endgroup$
    – JKalle
    Apr 28 at 19:06
  • $\begingroup$ Those are some other proteins, of which authors either didn't understand or have no interest. SARS-ME have identical or similar proteins with different concentrations. If you pay attention, SARS-CoV also have protein similar to Vero protein with $\pu{50 kD}$ (just below SARS-N protein). However, authors didn't mark it meaning they are not interested (I keep telling authors because I assume the image is from a publication). $\endgroup$ Apr 28 at 20:14
  • $\begingroup$ Okay, so I believe the image analysis part is that I need to identify all the little lines since I need to consider the total of its protein. Thank you very much. $\endgroup$
    – JKalle
    Apr 28 at 20:39
  • $\begingroup$ @JKalle it is still surprising that the exercise has been given. How one can analyse an image of that type in relation to protein size (obscure in a way in itself, it is number of amino acids or the physical V) without knowing about proteins and the technique used? Really puzzling. Unless you arbitrary resume the actual quiz text. $\endgroup$
    – Alchimista
    Apr 29 at 9:10
  • $\begingroup$ @Alchimista, yes and it is frustrating to be given such a task when the image analysis part is not that difficult once I know what he wants me to do. But maybe the teacher thinks that a Western blot is second nature to anyone in science, which is not the case. The task does say the 'approximate' size of the S protein relative to the total of the proteins, but that would be implicit either way since it is impossible to determine the exact value from that image. $\endgroup$
    – JKalle
    Apr 29 at 10:06

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