title: Formation of a vitamin B-12-serum complex on heating at alkaline pH.
abstract: The binding of vitamin B-12 to serum proteins during heating at alkaline pH was investigated by gel filtration of serum supplemented with cyano[57Co]-cobalamin. Heating for 5 min at 100 degrees C destroyed most of the vitamin B-12 binding activity of serum but, with further heating, the vitamin B-12 became incorporated into a complex that did not correspond in molecular size to the original vitamin B-12 binding proteins. Radioassay of vitamin B-12 in heated serum showed correspondingly first an increase then a progressive decrease in the apparent vitamin B-12 level suggesting that, on heating, vitamin B-12 was initially released then subsequently complexed by the serum. The formation of complexed vitamin B-12 was abolished by the presence of the reducing agent dithiothreitol during the heating step.
mesh_terms: D002850:Chromatography, Gel; D003037:Cobalt Radioisotopes; D006358:Hot Temperature; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D011869:Radioligand Assay; D014805:Vitamin B 12 / Q000378:metabolism; D014803:Vitamin B Complex / Q000097:blood*
chemical_list: D003037:Cobalt Radioisotopes; D014803:Vitamin B Complex; D014805:Vitamin B 12