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Why Are Viral Capsids Icosahedral?
- avereveard 8mo agoeh but also organic chemistry only does well 30 and 60 degrees
- pfortuny 8mo agoNot in 3D.
- avereveard 8mo agohttps://upload.wikimedia.org/wikipedia/commons/thumb/c/c2/Illustration_of_the_Caspar-Klug_model_for_viruses_%28or_%22Goldberg_Polyhedra%22_or_%22Geodesic_domes%22_or_%22Fullerenes%22%29.gif/250px-Illustration_of_the_Caspar-Klug_model_for_viruses_%28or_%22Goldberg_Polyhedra%22_or_%22Geodesic_domes%22_or_%22Fullerenes%22%29.gif https://upload.wikimedia.org/wikipedia/commons/thumb/c/c2/Il...
- adrian_b 8mo agoThat image just demonstrates what was mentioned in the article, that the sphere cannot be covered only with regular hexagons, but a part of them must be replaced with regular pentagons, so the angles that are multiples of 30 degrees are not sufficient. So the previous poster was right.
- pfortuny 8mo agoAn angle projected on a plane is not the same as a 3D angle. Also see the structure of diamond (109 degs).
- SAI_Peregrinus 8mo agoNot in 3D Euclidean space. I'm pretty sure 3D Hyperbolic space allows it just fine.
- BigTTYGothGF 8mo agoThe universe seems perfectly happy to have, for example, 5-member rings tho.
- dekhn 8mo agoSee buckyballs as a trivial refutation of your point.
- HappySweeney 8mo agoAre buckyballs organic?
- dekhn 8mo agoYes! Not sure why you're asking- things don't have to be created by biological processes to be organic (this concept is totally unrelated to "organic" in the supermarket).
- andrewflnr 8mo agoFormally, yes. "Organic chemistry" is not too far off a synonym for "chemistry with carbon involved".
- IAmBroom 8mo ago"Not too far off" = "exactly defined as".
- andrewflnr 8mo agoI wasn't sure if there were any weird edge cases, but yeah.
- dekhn 8mo agoI mean, I don't think diamonds are considered "organic"; same for graphite. But that's where the term "organic" itself starts to break down as a category.
- andrewflnr 8mo agoI was also thinking carbonates in a geologic context.
- NooneAtAll3 8mo ago> even though evolution is contingent at a local level (such as a specific protein sequence or the shape of a flower), it is remarkably predictable at a global level (such as the very existence of proteins and flowers across many species) to be fair... flowers are a very recent invention that appeared only after the dinosaurs got wiped out and clean slate allowed co-evolution of flowers and pollinators to occur
- yorwba 8mo agoFlowering plants (angiosperms) appeared during the Cretaceous before dinosaurs got wiped out, and there is fossil evidence of insects pollinating non-flowering plants (gymnosperms) like ferns and confers even earlier than that: https://repository.si.edu/server/api/core/bitstreams/152b12da-a614-4633-b063-26caa81dee16/content https://repository.si.edu/server/api/core/bitstreams/152b12d...
- flobosg 8mo agoThe header illustration brought to my mind, for some reason, the tomato bushy stunt virus depiction by the late Irving Geis: https://pdb101.rcsb.org/sci-art/geis-archive/gallery/geis-0563-tomato-bushy-stunt-virus https://pdb101.rcsb.org/sci-art/geis-archive/gallery/geis-05...
- meindnoch 8mo ago>an estimated 70 percent of viral capsids known to date are icosahedral, shaped like tiny soccer balls. Soccer balls are not icosahedra. The archetypal soccer ball is a truncated icosahedron: https://en.wikipedia.org/wiki/Truncated_icosahedron https://en.wikipedia.org/wiki/Truncated_icosahedron
- 1-more 8mo agoAnd that archetypal soccer ball design is called the Telstar and named for a communications satellite, fun fact. I think before 1968 the volleyball shape was more popular https://en.wikipedia.org/wiki/Adidas_Telstar https://en.wikipedia.org/wiki/Adidas_Telstar
- strgrd 8mo agodo you know what the modifier "like" means in the sentence you quoted, or are you just being annoyingly pedantic
- yorwba 8mo agoThere are a few pictures of truncated icosahedra in the article, alongside several other shapes that are not icosahedra. The point is that they have icosahedral symmetry. The L is important.
- JackFr 8mo agoI was going to comment pedantically that soccer balls were dodecahedrons not icosahedrons, but in reading the article, I came to realize that truncated icosahedrons are the same as truncated dodecahedrons. This was such a delightful realization I felt the need to comment anyway.
- dekhn 8mo agoWe used to joke in my biophysics grad program that basically everything was determined by its surface area to volume ratio.
- IAmBroom 8mo ago"First, assume a spherical chicken."