Figure 1 | Representation of cell surface properties. a, Diagram of a 35 × 35 nm section of the red blood cell surface showing the lipids (pink), major proteins (blue) and carbohydrates (orange). Different proteins and carbohydrates are indicated by different shapes and shading. Although there is also considerable heterogeneity in the lipid component of the cell membrane, this is omitted both for simplicity and because the nanoscale organization is still a matter of debate. The relative dimensions, concentrations and chemistries of all membrane components can vary drastically depending on cell type, disease state and life cycle, as shown in b–d. b, Relative sizes of the glycocalyx for a red blood cell (RBC; <10 nm) and a cell lining the blood vessel wall (>200 nm). c, Relative concentration of HER2 protein (also known as ERBB2) at the surfaces of a normal cell and a cancerous cell. In certain tumour lines, this protein alone can cover more than 15% of the cell surface area57. d, The carbohydrate coat plays a chemical as well as physical role in cell regulation. Negatively charged domains resulting from sulfation of disaccharide chains are capable of specific protein interactions. Disrupting these domains with strong oxidizing agents can drastically alter cell behaviour, even preventing embryonic stem cells from undergoing differentiation. Ac, acetyl. Insert shows carbohydrate chain based on N-acetylglucosamine (brown) and glucaronic acid (tan) monomers. Green indicates N- (circle), 6-O- (square) or 2-O-sulfation .
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