Speciation of Cyclo(Pro-Gly) 3 and Its Divalent Metal-Ion Complexes by Electrospray Ionization Mass Spectrometry

Electrospray ionization mass spectrometry (ESI-MS) was used to study the binding of selected group II and divalent transition-metal ions by cyclo(Pro-Gly) 3 (CPG3), a model ion carrier peptide. Metal salts (CatX n) were combined with the peptide (M) at a molar ratio of 1:10 M/Cat in aqueous solvents...

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Bibliographic Details
Published in:	Journal of the American Society for Mass Spectrometry Vol. 16; no. 9; pp. 1536 - 1544
Main Authors:	Ross, Andrew R.S., Luettgen, Sarah L.
Format:	Journal Article
Language:	English
Published:	New York, NY Elsevier Inc 01-09-2005 Elsevier Science Springer Nature B.V
Subjects:	Abundance Acetonitrile Ammonium acetate Atomic properties Binding Binding Sites Chemistry Coordination compounds Copper Electrospraying Exact sciences and technology Inorganic chemistry and origins of life Ionization Ions Manganese Mass spectrometry Metal ions Metals - chemistry Models, Chemical Models, Molecular Nickel Oxygen atoms Peptide Mapping - methods Peptides Peptides, Cyclic - chemistry Preparations and properties Scientific imaging Speciation Spectrometry, Mass, Electrospray Ionization - methods Spectroscopy Strontium Divalent metal Complexes Collisional activation Stability Peptides Cyclic peptides Organic ligand Fragmentation pattern Alkaline earth metal Complexes Transition metal Complexes Experimental study Electrospray Hexapeptide Mixed solvent Mass spectrometry MS/MS Hydroorganic solvent Mass spectrometry Speciation
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Summary:	Electrospray ionization mass spectrometry (ESI-MS) was used to study the binding of selected group II and divalent transition-metal ions by cyclo(Pro-Gly) 3 (CPG3), a model ion carrier peptide. Metal salts (CatX n) were combined with the peptide (M) at a molar ratio of 1:10 M/Cat in aqueous solvents containing 50% vol/vol acetonitrile or methanol and 1 or 10 mM ammonium acetate (NH 4Ac). Species detected include [M + H] +, [M + Cat − H] +, [M 2 + Cat] 2+, [M + Cat + Ac] +, and [M + Cat + X] +. The relative stabilities of complexes formed with different cations (Mg 2+, Ca 2+, Sr 2+, Mn 2+, Co 2+, Ni 2+, Cu 2+, and Zn 2+) were determined from the abundance of 1:1 and 2:1 M/Cat species relative to that of the unbound peptide. The largest metal ions (Ca 2+, Sr 2+, and Mn 2+) formed the most stable complexes. Reducing the buffer concentration increased the overall extent of metal binding. Results show that the binding specificity of CPG3 depends upon the size of the metal ion and its propensity for electrostatic interaction with oxygen atoms. Product ion tandem mass spectrometry of [M + H] + and [M + Cu − H] + confirmed the cyclic structure of the peptide, although the initial site(s) of metal attachment could not be determined.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	1044-0305 1879-1123
DOI:	10.1016/j.jasms.2005.05.002