Body cells connect to collagen by a special protein, named
, which at one end has binding
sites for a special family of membrane proteins, called
. Along the length of fibronectin, there are a
series of selective binding sites for collagen, fibrin (=blood clots) and several other extracellular structural
proteins., blood clots. Fibronectin also sticks non-specifically to glass and plastic.
Fibronectin was independently discovered and purified by four different researchers
, each using a different
criterion. One of these co-discoveries resulted from 2-dimensional chromatography & electrophoresis of all
the proteins found in cancerous cells, as compared with the most closely related non-cancerous cells. There
was one spot that was dramatically reduced in amount in the cancerous cells.
One of the other independent
studies was a comparison of commercially-bought batches of calf serum
. Tissue culture media traditionally
contains 10% calf serum; and you buy this serum from meat packing companies, sometimes indirectly. Some
batches produce much more cell locomotion ("spreading", "growth") than others. A post-doc was assigned to
find out what was missing in the bad batches, present in the good batches, and could by itself produce much
better cell spreading.
Until then, the dominant opinion was that plasma membranes themselves adhered to external materials by
forming "calcium bridges
". That was because if you reduce the concentration of calcium and magnesium
ions, cells will detach from glass, plastic and each other. This effect is mostly because the cell cortex
becomes much more flexible when Ca and Mg are reduced
, and gets pulled out in strands.
2) Genes are made of DNA
. This was discovered using transfer of genes between pneumonia-causing
. Some members of a certain species were fatal (to mice and humans), and had "smooth" patterns of
growth in culture, with both these properties resulting from sugar polymers on their outer surfaces. Mutant
forms of the same species formed "rough" colonies, had different surface sugars, and were much less lethal.
Griffith had discovered in the 1920s that if you injected mice with some of the rough bacteria, plus
molecules from killed bacteria of the harmful smooth strain, then not only would the mice die, but you could
culture smooth bacteria from them.