Table 1. List of ligands, metals and buffers used in peptide mass-spectrometry experiments.

Heavy-atom compounds	Chemical formula	Vendor/catalog No.†	Peptides	Buffers
Platinum		All platinum-containing compounds were from Hampton Research HR2-422	GEAGMASAGGAG	HEPES pH 78
Potassium tetrachloroplatinate(II)‡	K2PtCl4		GEAGCASAGGAG	MES pH 6
Platinum potassium thiocyanate	K2Pt(SCN)6		GEAGHASAGGAG	Sodium acetate pH 45
Platinum potassium iodide§	K2PtI6			Sodium cacodylate pH 5.56.5
Potassium hexabromoplatinate(IV)‡	K2PtBr6			Sodium citrate pH 46
Potassium tetrabromoplatinate(II)‡ §	K2PtBr4			TrisHCl pH 7.58.5
Diamino platinum dinitrate‡ §	Pt(NH3)2(NO2)2
Potassium tetranitroplatinate(II)	K2Pt(NO2)4
Dichloro(ethylenediamine)platinum(II)§	PtCl2(H2NC3H6NH2)
Potassium tetracyanoplatinate(II)	K2Pt(CN)4
Ammonium tetrachloroplatinate(II)	(NH4)PtCl4
Potassium hexachloroplatinate(IV)	K2PtCl6
Gold
Potassium tetrachloroaurate(III)	KAuCl4	HR2-444	GEAGMASAGGAG	HEPES pH 78
Sodium tetrachloroaurate(III)	NaAuCl4 4	HR2-444	GEAGCASAGGAG	MES pH 6
Gold(III) chloride‡ §	AuCl3	HR2-444	GEAGHASAGGAG	Sodium acetate pH 45
Gold chloride	HAuCl4	HR2-444		Sodium cacodylate pH 5.56.5
Gold sodium bromide	NaAuBr4	HR2-444		Sodium citrate pH 46
Potassium tetrabromoaurate(III)	KAuBr4	Strem Chemicals 79-3250		TrisHCl pH 7.58.5
Gold sodium thiosulfate§	Na3Au(S2O3)2	Alfa Aesar 39741
Gold(I) potassium cyanide	KAu(CN)2	HR2-444
Gold potassium thiocyanide§	KAu(SCN)4	Alfa Aesar 39666
Mercury
Thiomersal‡	C9H9HgNaO2S	HR2-446	GEAGMASAGGAG	HEPES pH 78
Mersalyl‡ §	HOHgCH2CH(OCH3)CH2NHCOC6H4OCH2CO2H	HR2-446	GEAGCASAGGAG	MES pH 6
Potassium mercury tetraiodide§	K2(HgI4)	HR2-446	GEAGHASAGGAG	Sodium acetate pH 45
Methylmercury(II) acetate‡ §	CH3HgO2CCH3	Pfaltz Bauer M21875		Sodium cacodylate pH 5.56.5
Ethylmercury(II) phosphate‡	(C2H5HgO)HPO2	HR2-446		Sodium citrate pH 46
p-Chloromercuribenzenesulfonic acid (PCMBS)	C6H5ClHgSO3	Sigma C4503		TrisHCl pH 7.58.5
Mercury(II) acetate‡ §	Hg(OOCCH3)2	HR2-446
Methylmercury(II) chloride‡ §	CH3HgCl	HR2-446
Mercury(II) cyanide	Hg(CN)2	HR2-446
Mercury(II) bromide‡ §	HgBr2	HR2-446
Mercury(II) chloride	HgCl2	HR2-446
Methylmercury(II) bromide	Ch3HgBr	HR2-446
p-Chloromercuribenzoic acid (PCMB)	C7H5ClHgO2	HR2-446
Ethylmercury(II) chloride	C2H5HgCl	HR2-446
Mercury(II) iodide§	HgI2	HR2-446
Mercury(II) oxide	HgO	HR2-446
Other
Potassium hexachloroosmate(IV)§	K2OsCl6	HR2-448	GEAGMASAGGAG	HEPES pH 78
Potassium hexachloroiridate(III)§	K2IrCl6	HR2-448	GEAGCASAGGAG	MES pH 6
			GEAGHASAGGAG	Sodium acetate pH 45
				Sodium cacodylate pH 5.56.5
				Sodium citrate pH 46
				TrisHCl pH 7.58.5
Lead
Lead acetate‡	Pb(CH3COO)2	Sigma L3396	GAAGDASAGGAG	HEPES pH 78
Trimethyllead acetate	CH3CO2Pb(CH3)3	Sigma 116815	GAAGEASAGGAG	MES pH 6
Hexaphenyl dilead§	[(C6H5)3Pb]2	Alfa 57132	GAAGNASAGGAG	Sodium acetate pH 45
Lead nitrate‡	Pn(NO3)2	Sigma L6258	GAAGQASAGGAG	Sodium cacodylate pH 5.56.5
Triethyllead acetate‡	Ch3CO2Pb(C2H5)3	Sigma 116823	GAAGYASAGGAG	Sodium citrate pH 46
				TrisHCl pH 7.58.5

^†HR2-422, HR2-444, HR2-446 and HR2-448 are from Hampton Research.

^‡Compounds used to derivatize lysozyme.

^§Compounds that were not fully soluble at 10mM.