title: Use of protein containing magnetic microparticles in radioassays.
abstract: We describe a radioassay method that involves the use of magnetic protein microparticles composed of a water-insoluble protein matrix containing magnetically responsive material. We define two different types of particles according to the mechanism of action: (a) The substrate is sorbed nonspecifically by the protein matrix of the particle or by a second substance such as charcoal or ion-exchange resin incorporated within the protein matrix of the particle. These particles are useful for separating free from bound substrate. Examples of these are albumin magnetic microparticles for use in a total thyroxine radioassay and triiodothyronine uptake test, or albumin magnetic microparticles containing charcoal for use in a vitamin B12 radioassay. (b) The substrate is sorbed specifically by a binding protein incorporated within the matrix of the particles. The binding protein can include antibodies or other specific nonimmune proteins. Particles of this type are useful in solid-phase radioassays. These particles are exemplified by albumin magnetic microparticles containing sockeye salmon serum, used in a solid-phase B12 radioassay. We discuss the methods for the preparation of both types of magnetic microparticles and their use in radioassays. We describe a unique inexpensive magnetic separation rack, which provides simple, fast, and reproducible separation of the magnetic microparticles from their suspending medium during the assay.
mesh_terms: D006801:Humans; D007501:Iron; D008280:Magnetics; D011869:Radioligand Assay / Q000379:methods; D012710:Serum Albumin, Bovine; D013974:Thyroxine / Q000097:blood*; D014284:Triiodothyronine / Q000097:blood*; D014805:Vitamin B 12 / Q000097:blood*
chemical_list: D014284:Triiodothyronine; D012710:Serum Albumin, Bovine; D007501:Iron; D014805:Vitamin B 12; D013974:Thyroxine