Table 2. Accuracy and recovery data for the LC-MS/MS quantification of SAM and SAH in mouse embryos.

Embryo samples consisted of pools of homogenised embryos collected at E9.5 and E10.5. Accuracy (% nominal concentration) was determined by comparing the measured concentration of SAM of SAH against the nominal concentration (the predicted value equating to the baseline concentration with 0 pM SAM or SAH added + spiked concentration). Thus, %Nominal concentration = Mean Measured Conc.]/[Mean Baseline conc. + Spiked conc.]. Recovery was determined by comparing the assay results for embryo samples spiked pre- and post- extraction (n = 3 for each condition). % Recovery = ([Response of Pre-Extracted Spiked Sample] / [Response of Post-Extracted Spiked Sample]) x 100 [as ref. 22]. Concentration values are given as mean ± standard deviation.

Sample	Spiked conc. added (μM)	Measured conc. (μM)	Accuracy (% Nominal Conc.)	Measured conc. (μM)	Accuracy (% Nominal Conc.)	Recovery (%)
	SAM Added	Spiked pre-extraction		Spiked post-extraction
E9.5 mouse embryo	0	0.08 ± 0.020
	0.5	0.57 ± 0.030	98	0.57 ± 0.02	98	100
	1.0	1.06 ± 0.020	98	1.09 ± 0.06	101	97
	2.0	2.08 ± 0.004	100	2.12 ± 0.09	102	98
E10.5 mouse embryo	0	0.79 ± 0.01
	0.5	1.21 ± 0.01	94	1.19 ± 0.17	92	101
	1.0	1.82 ± 0.04	102	2.03 ± 0.28	113	90
	2.0	2.64 ± 0.04	95	2.83 ± 0.27	101	94
	SAH Added
E9.5 mouse embryo	0	0.11 ± 0.009
	0.05	0.13 ± 0.002	81	0.14 ± 0.003	88	97
	0.1	0.19 ± 0.001	86	0.21 ± 0.009	100	87
	0.2	0.33 ± 0.027	106	0.35 ± 0.030	113	92
E10.5 mouse embryo	0	0.20 ± 0.030
	0.05	0.23 ± 0.001	92	0.24 ± 0.006	96	90
	0.1	0.30 ± 0.070	100	0.34 ± 0.030	113	91
	0.2	0.38 ± 0.040	95	0.42 ± 0.050	105	95