title: Letter: Small membrane-labels do not unambiguously reveal membrane 'sidedness'.
mesh_terms: D002462:Cell Membrane; D002463:Cell Membrane Permeability; D004912:Erythrocytes / Q000166:cytology*; D006863:Hydrogen-Ion Concentration; D007553:Isotope Labeling; D011485:Protein Binding; D013462:Sulfur Radioisotopes
chemical_list: D013462:Sulfur Radioisotopes