bbs上看到一个链接，点过去，发现是Harvard和一个电脑动画公司联合制作的一个短片，讲述的是血管中白细胞附着在血管壁的过程中，细胞内部各个部分精密工作的过程。
真的很难想象大自然能够进化的如此精妙如此完美，想想这样奇迹般的过程其实是每时每刻发生在我们的身上，不禁被生命的伟大而深深折服！
The Inner Life of A Cell
在线视频：
相关说明：
另外附上一个解说供参考：
- First shot: circulation. Red blood cells and platelets move extraordinarily fast through the bloodstream while many white blood cells roll along the walls of your blood vessels. This allows the WBCs to respond to signals that it should break through the vessel wall and help out (if it were unattached it wouldn't be able to land in time to be anywhere near where it was needed)
- Next we zoom in on the white blood cell's rolling process. We see that this happens because proteins sticking out from the WBC stick to proteins sticking out from the cells lining the blood vessel (these proteins are called CAMs, or cellular adhesion molecules. I forget exactly what kind of CAM mediates this kind of cell-cell adhesion, but there are subtypes). We also see the extracellular matrix in this shot -- that's the fibrous stuff covering the outside of the cell, giving it rigidity (it's made up of proteins like collagen... inside your body, if it breaks it lets out a signal to nearby cells to grow and fill in the break, if you're cut for example). One thing to note about CAM adhesion is that two proteins don't generally stick together, they have to be specifically tailed for that function.
- Next we zoom in further on the surface of the cell, beyond the extra cellular matrix. We sea the sea of lipids (blue and green round things) that make up the boundary of the cell, and we see a raft floating through them. This is a "lipid raft", and it has more cholesterol in it than the rest of the cellular membrane. These rafts are special places for certain proteins and lipids to aggregate (i.e., some proteins designed to accept signals from the environment will aggregate in these -- an example of a signal is a hormone like insulin, which when it attaches to a protein designed to catch it will cause a cell to change metabolism, for example).
- Next we see two proteins making contact (the red one hanging down and the purple one sticking up). I don't know what these proteins are, but my guess is that the vessel cell is signaling to the WBC that the WBC should invade the tissue (i.e., there's damage and the inflammatory process sends signals that eventually get to WBCs, which then come to help).
- A pretty shot zoomed out of a raft floating along the cell surface
- I don't know what the trinagular structres are, which is frustrating. Maybe it's actin covering the interior wall of the cell? Actin is a cytoskeletal protein (i.e., it makes up a rigid structural and transport network) that covers the interior side of the cellular membrane. It's a meeting point between things on the inside of the cell and the cellular membrane (which is useful, for example, if a signal is received on the cell surface and needs to trickle into intracellular components).
- Next is the purple and green lattice. I think this is actin with cross-linking proteins. Actin fibers (actin is made up of protein subunits that form those long, twisty fibers) don't just randomly stack, they're also connected to each other by proteins to make the dense structure you see here.
- Next we see actin polymerization (the purple fibrils self-assembling). This is a spontaneous process that happens when the concentrations of actin are high enough (and it looks really cool here). The cell tightly regulates the concentration of actin so as to make the right amount of these fibers.
- Next we see the small green protein stick to actin, breaking it up. Our cells will activate these proteins if they want to break down that huge actin lattice we saw earlier very quickly (i.e., when the cell is moving). An interesting sidenote is how well the proteins fit together. This isn't artistic license, these proteins' 3D structures are modeled after real life.
- Next the huge green tube -- this is a microtubule assembling. Like actin, this is a spontaneous process dictated by concentration. Microtubules are made up of alternating alpha and beta subunits. Then we see the microtubule dissassembling. Notice how it frays at the end and then completely falls apart...I think that's a realistic rendering.
- Next is what I think is the coolest part, the little walker along the microtubule. That's a kinesin, a protein that literally walks along microtubules to carry cargo around the cell. This is how things end up at their destinations without having to just float around until they hit the right thing. Microtubules are organized to radiated from a microtubule organizing center out to the cell surface. Here a kinesin is walking in a specific direction (I assume toward the cell surface) because its cargo, a huge vesicle, needs to get there. Vesicles are little lipid-bound blobs that carry stuff around -- so this all is the FedEx of the cell. Kinesins are fascinating proteins -- they don't walk without energy input, since the walking requires work. ATP is involved.
- Then we zoom out and see the MTOC (microtubule organizing center) in the background (the sphere with two orthogonal cylinders in front). Microtubules emanate from there. MTOCs are pretty interesting things because they have to multiply and divide with the rest of the cell, and we don't know exactly how that works yet.
- Now we've changed venues...we see a round surface with little holes. That round surface is the nucleus, where DNA lives. Those holes are nuclear pores, which is how things get in and out of the nucleus. DNA is transcribed into RNA in the nucleus, and that RNA is then transported out of the cell where it is translated into proteins by ribosomes. In higher order organisms the RNA makes a circle as you see here. If you look closely you can see the small subunit of the ribosome attach to the RNA and scan along until it finds the start sequence on the RNA, where the large subunit then attaches.
- Then we zoom in on the ribosome reading the RNA and spitting out the growing protein. Pretty cool shot.
- Next is the blue and red proteins floating over to the huge cylindrical blob. I don't know if that's a proteasome or a chaperone...I think it's a chaperone. Anyway, the role of a chaperone is to take in a newly synthesized protein and fold it properly. There's lots of research going on into how exactly this happens right now (i.e., Fold@Home).
- The next shot is translation again (see the yellow-green ribosome and the RNA stuck in it). This time translation is happening into the Endoplasmic Reticulum, however, because the protein it's making needs to be secreted out of the cell. This is where that process starts (proteins meant for secretion aren't just made in the cytosol and then magically end up on the outside of the cell. They're spit into this special compartment where its exit from the cell is ordered).
- Next is some vesicle formation, I assume off of the ER and toward the golgi apparatus, which is the next stop in the secretory pathway for proteins destined for the outside of the cell. We see the kinesin in the foreground again.
- Next we see the vesicle arriving at the golgi apparatus, the large layer of blobby pancakes. Vesicles from the ER arrive at one end and progress through the layers, where they're either targeted for other parts of the cell, or if not will exit via a vesicle to the cell membrane.
- Now we see a huge cavity opening up and things flying out of the cell. This is what happens when a vesicle makes it to the cell membrane -- it fuses, releasing its contents outside. Proteins that were in the vesicle membrane are now part of the cellular membrane. The orientation of these membrane-attached proteins is controlled so that they face the right way.
- Then we see raft formation, I think, around a set of proteins.
- Then we zoom out and see the result of the signal to the WBC -- it invades through the blood vessel wall to the surrounding tissue. I don't know anything about the immune system, though, so my details on the macro aspect are sketchy and possibly incorrect.
