Cell Biology. In the article “Quantitative analysis of biological membrane lipids at the low picomole level by nano-electrospray 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, 2339–2344), Table 1 contains errors. A corrected table is reprinted below with corrections in boldface type.

Table 1.

Identification of the most abundant signals in the ESI mass spectra of total lipid extract of CHO cells, as given in Fig. 1 a and b

Class of phospholipid	Ion	Total fatty acid carbon no.:no. of double bonds
		32:1	34:2	36:2	38:4	16:0	18:0	22:0	24:1	26:0
PA	[M-H]−	645	671	699	723
PS	[M-H]−	732	758	786	810
PE	[M-H]−	688	714	742	766
Plasmenyl-PE	[M-H]−	672	698	726	750
PI	[M-H]−	807	833	861	885
PG	[M-H]−	719	745	773	797
PC	[M+H]+	732	758	786	810
	[M+Na]+	754	780	808	832
Plasmenyl-PC	[M+H]+	716	742	770	794
	[M+Na]+	738	764	792	816
PE	[M+H]+	690	716	744	768
Plasmenyl-PE	[M+H]+	674	700	728	752
PS	[M+H]+	734	760	788	812
SM	[M+H]+					703	731	787	813	843
	[M+Na]+					725	753	809	835	865

In the negative ion mode, PS and PE (with two nitrogen atoms) show signals at even-numbered m/z values, whereas PI, PG, and PA show signals at odd-numbered values. In the positive ion mode, SM signals appear at odd m/z values (2 nitrogen atoms), whereas PC, PE, and PS-signals occur at even m/z values. The m/z values are nominal monoisotopic data.