# SARS-CoV - relative size of the spike protein

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).

• Biology is more suitable for this, I think. – orthocresol Apr 28 at 17:11
• @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). – JKalle Apr 28 at 17:12
• 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. – orthocresol Apr 28 at 17:19
• 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. – orthocresol Apr 28 at 17:20
• The Western blot looks similar to the image, so I will try and read about that. Thank you for trying to help, @orthocresol. – JKalle Apr 28 at 17:26

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.
• 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). – Mathew Mahindaratne Apr 28 at 20:14