Assessment of Embryonic Bioactivity through Changes in the Water Structure Using Near-Infrared Spectroscopy and Imaging

We explored the influence of embryonic bioactivity on the water structure using near-infrared (NIR) spectroscopy and imaging. Four groups of Japanese medaka fish (Oryzias latipes) eggs were studied: (a) one group of eggs was activated by fertilization, and (b-d) three groups of eggs were not activated because embryogenesis was stopped or not started by (b) culturing under cold temperature, (c) instant freezing, or (d) lack of fertilization. The yolks of the activated eggs contained higher proportions of weakly hydrogen bonded water than those of nonactivated eggs. A possible factor responsible for the significant changes in the water structure was revealed to be a protein secondary structural change from an alpha-helix to a beta-sheet in the activated eggs. NIR images of the activated eggs successfully visualized the water structural variation in the yolk with a higher proportion of weak hydrogen bonds due to the activation of embryonic development. The embryogenic activity could be assessed through the water hydrogen bond network, which is affected by newly generated proteins with different secondary structures.