Boxer's group used atomic force microscopy to locate interesting places and then employed the NanoSIMS 50 to determine what was there chemically. ''Either technique by itself would be I think insufficient, but combined, they're really powerful,'' Boxer said. The combination of techniques allowed the researchers to distinguish debris from features of interest.
''The real point is that you can do quantitative analysis,'' Boxer said, emphasizing that this research allowed the first high-resolution mapping of chemical features in a region of interest. ''We can analyze a few percent of one component in the presence of other components...It's exquisitely sensitive.''
Sensitivity is important because cell membranes are not pure materials. ''We're looking at mixtures of things, and we want to be able to say that we've got one molecule in 20 of type A mixed in with type B, or something like that,'' Boxer said.
This world is flat-sometimes
''Imagine how a cell could divide if it weren't for the fact that the membranes were flexible,'' Boxer said. ''They must be flexible. You have endocytosis, exocytosis, all these processes which involve dynamic reorganizations of membranes.''
The membrane that surrounds a cell or the organelles within cells is made of two layers of phospholipids-microscopic ''lollipops'' with water-loving (hydrophilic) heads that point outward and water-fearing (hydrophobic) tails that point inward. The cell membrane is studded with proteins like receptors and ion channels, which cross the membrane many times and transmit signals from the outside of the cell to the inside. Others don't cross the membrane at all-they are anchored to the membrane by lipid-like entities or by single transmembrane helices. The membrane is a fluid and components can move around laterally to differing degrees, like swimmers in a pool. The Nan