NIDDM is associated with decreased chiro-inositol excretion and decreased chiro-inositol content in muscle. These abnormalities seem to reflect the presence of insulin resistance in NIDDM:

Monensins are a series of polyether ionophore antibiotic factors produced by Streptomyces cinnamonensis. Three monensin factors and four metabolites of monensin A isolated from cattle feces were investigated by electrospray ionization mass spectrometry (ESI-MS). In-source collision-induced dissociation (CID) of the alkali metal and ammonium molecular ion adducts of monensin produce strikingly different mass spectra, with the alkali metal complexes exhibiting little dissociation and the ammoniated forms characterized by extensive fragmentation of the polyether skeletal structure with the production of several structurally diagnostic ions. The observed fragmentation of ammoniated monensin primarily involves opening of the cyclic ether rings and consecutive H 2 O losses. The propensity of ammoniated monensin derivatives toward skeletal fragmentation may involve the complexation of the thermally labile NH 4 ion through multiple hydrogen-bonding interactions with the polyether complexing oxygens resulting in decreased stability of the resultant complex. Comparison of the in-source CID spectra associated with the structurally similar compounds evaluated provides for the proposal of a general scheme for the fragmentation of ammoniated monensins and related compounds, the consistency of which indicates the usefulness of ESI-MS with insource CID in ionophore structure elucidation. # 1998 John Wiley & Sons, Ltd. Received 8 May 1998; Accepted 20 May 1998 Monensin is a polyether monocarboxylic acid ionophore and refers to a group of factors comprising an antibiotic complex first isolated from Streptomyces cinnamonensis.

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Reversed phase high-performance liquid chromatography (RPHPLC) coupled with electrospray ionization mass spectrometry (ESI-MS) was used to separate and characterize the peptides resulting from the tryptic cleavage of somidobove, a recombinant bovine growth hormone. The tryptic digestion of somidobove was carried out at room temperature for 15 hours. The tryptic peptides were separated on a Zorbax SB300 C8 column with trifluoroacetic acid--acetonitrile gradient elution and characterized by LC/ESI-MS. Resulting single and combined peptide fragments were characterized by comparing the observed molecular mass with the calculated mass for these fragments.

Tilmicosin is a semisynthetic macrolide antibiotic used in the treatment of respiratory disease in cattle and swine. The technique of liquid chromatography/atmospheric pressure chemical ionization mass spectrometry (LC/APCI-MS) was employed in an on-line capacity for the analysis of tilmicosin in extracts from spiked swine liver. Increasing the potential in the cone/skimmer region of the ion source resulted in an increased abundance of unique structurally indicating fragment ions of tilmicosin. Three ions, [M+H]+ and two diagnostic fragment ions were chosen for confirmation of the presence of tilmicosin in swine liver tissue extracts using the mass spectrometer in selected-ion monitoring mode. The ion abundance ratios arising from any given combination of ions in data acquired from extracts of swine liver tissue spiked with tilmicosin at 5 and 10 ppm were within +/- 10% of the corresponding mean standard abundance ratio, and duplicate sample analyses exhibited < 10% relative standard deviation. These results suggest the potential for the application of LC/APCI-MS as a confirmatory technique for tilmicosin in swine liver.