Detecting the body’s reproductive hormonal brake against tissue overgrowth: Micrin/SgII-70
Fig 5
MALDI MS of a solid ‘upstream precipitate’ that formed on the 3 kDa membrane during a 3−30 kDa ultrafiltration (with sodium azide) of ovine jugular vein EDTA plasma (S1 in S1 File Sheffield Method) – without the bacterial contamination of Fig 4. Matrix and calibration as Fig 2. Acquisition mass range 2500−25000 Da. Electroeluted SDS-PAGE Band 1 at ~7 kDa showed cell-inhibitory bioactivity in vitro. Edman sequencing of Band 1 from a prior (contaminated, azide free) purification provided the 14-residue N-terminal sequence MKPLTGKVKEFNNI (EPL001). This matched anionex Beale 4, the minimal sequence obtained from maximally purified (bacterially uncontaminated) material. Gel electroelution, as used here, provides a cleaner spectrum than solvent extraction (S3 Fig. 5 in S3 File), albeit with the same base peak, an sSgII-70 65mer, lacking –KANNI (Table 1).