following correction should be noted. In Fig. 1b, the designed sequence of amino acids S 36 contains a typographical error in that only 35 of its 36 monomers appear. The missing amino acid is of type R and should be located between amino acids E (sixth) and G (seventh). The correct sequence is:Although this typographical error does not change the results presented in the paper because they were obtained with the correct number and sequence of amino acids, it constitutes a nuisance for anybody interested in reproducing our results, and we apologize for the inconvenience. We want to thank Prof. H. S. Chan, of the University of Toronto, for calling our attention to this error.Cell Biology. In the article "Quantitative analysis of biological membrane lipids at the low picomole level by nanoelectrospray ionization tandem mass spectrometry" by B. Brügger, G. Erben, R. Sandhoff, F. T. Wieland, and W. D.Lehmann, which appeared in number 6, March 18, 1997, of Proc. Natl. Acad. Sci. USA (94,(2339)(2340)(2341)(2342)(2343)(2344), Table 1

The contents of secondary plant substances in solvent extracts of various byproducts (barks, kernels, peels, and old and young leaves) in a range of Brazilian mango cultivars were identified and quantitated. The results show that the profiles of secondary plant substances such as xanthone C-glycosides, gallotannins, and benzophenones in different byproducts vary greatly but are fairly consistent across cultivars. The free radical scavenging activity of the solvent extracts was evaluated using a high-performance liquid chromatography-based hypoxanthine/xanthine oxidase assay and revealed dose-dependent antioxidant capacity in all extracts. Four (mangiferin, penta- O-galloyl-glucoside gallic acid, and methyl gallate) of the major phenolic compounds detected were also evaluated in additional in vitro bioassay systems such as oxygen radical absorbance capacity, 2,2-diphenyl-1-picrylhydrazyl, and ferric reducing ability of plasma. Mangiferin in particular, detected at high concentrations in young leaves (Coite = 172 g/kg), in bark (Momika = 107 g/kg), and in old leaves (Itamaraka = 94 g/kg), shows an exceptionally strong antioxidant capacity.

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