= Slit diaphragm
A <slit diaphragm> is a specialized junctional structure spanning the filtration slit between adjacent <podocyte foot process> structures. It forms one component of the <glomerular filtration barrier>, alongside the glomerular <basement membrane> and <capillary> <endothelium>. The <slit diaphragm> bridges a gap; it is distinct from the <cell membrane> of either neighboring <podocyte>.
<Nephrin> provides a molecular example. Antibodies against its extracellular region, followed by gold-coupled secondary antibodies, localized the recognized <protein> to podocyte slits in the 1999 study. A model of how neighboring <nephrin> molecules might assemble was then proposed. The observed label location and the proposed molecular arrangement are different levels of evidence.<Nephrin is specifically located at the slit diaphragm of glomerular podocytes by V. Ruotsalainen and others>[Figure3: localization; Figure5: hypothetical assembly]{ref}
For a useful comparison, imagine two barriers with the same total slit length but different junctional organization. Equal length does not establish equal passage of <water> or <proteins>: molecular organization and the other barrier layers also matter. A localization image therefore helps identify components but cannot alone supply the <glomerular filtration rate>.
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