Fig. 6.

Proposed zinc signature population interpretation. a Interpretation of zinc signature meaning and population segregation: 16% of fresh, ejaculated spermatozoa had undergone early-stage capacitation upon semen collection (lightest blue working to darkest); 14% of spermatozoa spontaneously undergo early-stage capacitation during incubation without IVC inducers; 60% of spermatozoa remained capacitation competent with IVC inducers, with 21% sensitive to proteasomal inhibition; remaining 10% of sperm were capacitation incompetent under IVC conditions (darkest blue) (s.e. bars included). b Proposed zinc signature changes throughout female reproductive tract and oocyte zinc spark interference with sperm zinc signature as a combined polyspermy defense mechanism, the zinc shield