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Abstract

The objective of this study was to characterize the protein fractions in royal jelly made from Apis mellifera ligustica from middle and southern areas of Taiwan. The total nitrogen content of fresh royal jelly was 2.46%, and the total amino acid nitrogen was 2.34%, suggesting that the nitrogen compound in royal jelly was mostly derived from protein . The nitrogen content of free amino acid in royal jelly was 0.11%, and the amino type nitrogen was 0.20%, indicating that the protein in royal jelly existed mainly in the form of large moleculars. To characterize the protein, royal jelly was dissolved in 0.1 M phosphate buffer(pH 7.0), followed by centrifugation, ammonia sulfate precipitation and dialysis to separate the protein into water soluble and water insoluble fractions. Water soluble fraction accounts for more than 60 % of the total protein in royal jelly, and was further investigated by DEAE-Sephacel, SDS-PAGE and capillary electrophoresis. By DEAE-Sephacel, two fraction peaks (F1 and F2) were identified and collected. By SDS-PAGE, F1 fraction was further separated into two bands, and the molecular weight was determined to be 50 KDa and 44 KDa, whereas F2 fraction was shown to have only one band with molecular weight of 55 KDa. By capillary zone electrophoresis, four poorly-separated peaks were observed in F1 fraction, and two well-separated peaks in F2 fraction. By capillary gel electrophoresis, two peaks were identified in F1 fraction, of which the molecular weight was estimated to be 59 KDa and 73 KDa. By contrast, only one peak was identified in F2 fraction, of which the molecular weight was estimated to be 118 KDa. However, by capillary isoelectric focusing, 6 peaks were identified in F1 fraction with pI of 6.9, 6.7, 6.3, 5.9, 5.7 and 5.5, respectively. Of that, pI of 4.8 and 4.7 were identified in F2 fraction.

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