Why Are Viral Capsids Icosahedral?

(asimov.press)

70 points | by surprisetalk 4 days ago ago

22 comments

  • meindnoch 6 hours ago 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

    • yorwba 5 hours ago ago

      There 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 4 hours ago ago

        I 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.

    • 1-more 6 hours ago ago

      And 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

    • strgrd 5 hours ago ago

      do you know what the modifier "like" means in the sentence you quoted, or are you just being annoyingly pedantic

  • NooneAtAll3 7 hours ago 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

  • dekhn 6 hours ago ago

    We used to joke in my biophysics grad program that basically everything was determined by its surface area to volume ratio.

    • IAmBroom 2 hours ago ago

      "First, assume a spherical chicken."

  • avereveard 7 hours ago ago

    eh but also organic chemistry only does well 30 and 60 degrees

    • BigTTYGothGF 4 hours ago ago

      The universe seems perfectly happy to have, for example, 5-member rings tho.

    • dekhn 4 hours ago ago

      See buckyballs as a trivial refutation of your point.

      • HappySweeney 4 hours ago ago

        Are buckyballs organic?

        • andrewflnr 3 hours ago ago

          Formally, yes. "Organic chemistry" is not too far off a synonym for "chemistry with carbon involved".

          • IAmBroom 2 hours ago ago

            "Not too far off" = "exactly defined as".

            • andrewflnr 23 minutes ago ago

              I wasn't sure if there were any weird edge cases, but yeah.

              • dekhn 11 minutes ago ago

                I 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.

        • dekhn 4 hours ago ago

          Yes! 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).

    • pfortuny 6 hours ago ago

      Not in 3D.

      • avereveard 6 hours ago ago
        • adrian_b 4 hours ago ago

          That 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 3 hours ago ago

          An angle projected on a plane is not the same as a 3D angle.

          Also see the structure of diamond (109 degs).