FT-IR Microspectroscopy on molecular building of Zebrafish oocytes

Zebrafish oocytes growth causes relevant modifications in protein components; in fact, the proteolytic cleavage of vitellogenin, a large sex-specific phospholipoglycoprotein synthesized in the female liver, leads to three main yolk protein components (phosphovitin and lipovitellins 1, 2), present as a complex in the oocyte. FT-IR Microspectroscopy could have the potentiality of monitoring these biochemical changes during the maturation process. Representative spectra for I–II, IIIA, IIIB and IV classes oocytes (Hierarchical Clustering Analysis and Principal Component Analysis) were investigated to find specific vibrational patterns corresponding to different maturation degrees. On going from I–II to IV class oocytes, relevant spectral differences were found with III class exhibiting an intermediate spectroscopic behaviour. In particular, the increase of the convoluted band at 2925 cm−1 (CH2 and CH3 stretching modes), as well as of intensity band ratios at 2926/2954 cm−1 (νasym CH2/CH3), 2854/2873 cm−1 (νsym CH2/CH3) and 1452/1392 cm−1 (δCH2/3/νsymCOO-δCH2/3/νsymCOO-), suggest longer lipidic chains; broadening of Amide I and II bands and absorptions at 1737 (νCO, phospholipids) and 1157 cm−1 (νCO and νCOH carbohydrates) in lipovitellin and vitellogenin spectra, are present in III and IV classes.