Monolayer freeze‐fracture autoradiography: origins and directions

SUMMARY Monolayer freeze‐fracture autoradiography (MONOFARG) is a product of two earlier methods: freeze‐fracture autoradiography (FARG) and cell monolayer freeze‐fracture. MONOFARG incorporates many of the basic principles and cytochemical goals of FARG while exploiting the technical advantages of monolayer freeze‐fracturing. The latter method offers the opportunity to process freeze‐dried ‘half’ membranes at room temperature. Although the feasibility of MONOFARG has been shown for qualitative analyses of split membranes, its quantitative feasibility for transmembrane and in‐plane analyses has just begun to be documented. An example of one aspect of that documentation is included in this report. The distribution of 125 I‐FITC‐Concanavalin‐A in the plane of split plasma membranes, human erythrocyte extracellular fracture faces, was examined and found to be homogeneous. The relevance of this finding to recently described double labelled membrane splitting experiments is discussed. The future of MONOFARG appears promising, especially in the application of the technique to biologically significant questions.