Distribution of protein sulphydryls and disulphides in fixed mammalian chromosomes, and their relationship to banding.

Fixed mammalian mitotic chromosomes, when stained with a variety of sensitive, sulphydryl-specific fluorochromes directly or following reduction of disulphide groups, show uniform fluorescence. Thus sulphydryl and disulphide groups are uniformly distributed along the length of the chromosomes, and do not show patterns related to chromosome bands. Performance of G- or C-banding procedures oxidizes sulphydryls to disulphides, but does not produce an inhomogeneous distribution of these groups. Cross-linking sulphydryl groups has no effect on G-, C- or Q-banding of chromosomes. Thus there appears to be no connection between chromosome bands and the distribution or state of oxidation of sulphur in chromosomal proteins.