Unseen in such detail before, this nuclear pore acts as a 'cat-flap' for molecules moving between the nucleus and the surrounding cytoplasm in mammalian cells. Using an electron microscope, scientists revealed the internal structure of the ring-like pores – an arrangement of hundreds of proteins in concentric rings (gold) that form a tube-like passage (green) – allowing only small molecules to pass through the membrane encapsulating cell nuclei, while blocking others with the wrong shape and size. At its narrowest the pore is just one tenth of a micron across – for comparison, a fine human hair is around 50 microns thick. Defective transport of molecules through nuclear pores has been linked to several cancers, including ovarian, thyroid and intestinal, which scientists hope to understand better by studying the detailed structure of the pores.
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