Loihichelins A-F, a suite of amphiphilic siderophores produced by the marine bacterium Halomonas LOB-5.

A suite of amphiphilic siderophores, loihichelins A-F, were isolated from cultures of the marine bacterium Halomonas sp. LOB-5. This heterotrophic Mn(II)-oxidizing bacterium was recently isolated from the partially weathered surfaces of submarine glassy pillow basalts and associated hydrothermal flocs of iron oxides collected from the southern rift zone of Loihi Seamount east of Hawai'i.

Fragmentation of tunichrome Sp-1 is dominated by an unusual gas-phase intramolecular rearrangement.

Tunichrome Sp-1 is a modified pentapeptide from the ascidian Styela plicata, having the structure H-DOPA-DOPA-Gly-Pro-dcDeltaDOPA (where DOPA = 3,4-dihydroxyphenylalanine and dcDeltaDOPA = decarboxy-(E)-alpha,beta-dehydro-DOPA). The tandem mass spectrum of the peptide is dominated by a number of abundant fragment ions that involve a gas-phase rearrangement where the dcDeltaDOPA group becomes covalently attached to the N-terminus. The high degree of rearrangement in Sp-1 compared with a related octapeptide, plicatamide, allowed for detailed multiple mass spectrometric (MS(n)) (up to n = 6) experiments, and hence permitted a detailed assessment of the origin and routes to the formation of the various rearrangement ions.

Plicatamide, an antimicrobial octapeptide from Styela plicata hemocytes.

Plicatamide (Phe-Phe-His-Leu-His-Phe-His-dc Delta DOPA), where dc Delta DOPA represents decarboxy-(E)-alpha,beta-dehydro-3,4-dihydroxyphenylalanine, is a potently antimicrobial octapeptide from the blood cells of the solitary tunicate, Styela plicata. Wild type and methicillin-resistant Staphylococcus aureus (MRSA) responded to plicatamide exposure with a massive potassium efflux that began within seconds. Soon thereafter, treated bacteria largely ceased consuming oxygen, and most became nonviable.

Tunichrome sp-1: new pentapeptide tunichrome from the hemocytes of Styela plicata.

A modified pentapeptide has been isolated from the hemocytes of the ascidian Styela plicata. The structure of the peptide was determined by Edman sequence analysis, mass spectrometry, and NMR spectroscopy with the stereochemistry assigned by acid hydrolysis followed by both (a) GC-MS of the volatile amino acid derivatives on a chiral column and (b) ultrasensitive detection of fluorescent diasteromeric derivatives of the component amino acids after reversed-phase HPLC. The peptide L-DOPA-L-DOPA-Gly-L-Pro-dcdeltaDOPA (where DOPA = 3,4-dihydroxyphenylalanine and dcdeltaDOPA = decarboxy-(E)-alpha,beta-dehydro-3,4-dihydroxyphenylalanine) we designate as tunichrome Sp-1.