Fragmentation mass spectra dataset of linear cyanopeptides - microginins

Microginins are the less common class of bioactive linear cyanobacterial peptides. Recently, an investigation for their presence in cyanobacteria from Greek freshwaters and strain cultures was carried out. The present dataset is related to the research article “New microginins from cyanobacteria of Greek freshwaters” [1]. Cyanobacterial biomass from bloom samples and cultured strains were extracted with aqueous methanol. Extracts were analysed by liquid chromatography coupled to hybrid triple quadrupole/linear ion trap mass spectrometer (LC-qTRAP MS/MS) in information dependent acquisition (IDA) mode. Enhanced ion product (EIP) mode was applied for the collection of ion fragmentation spectra. Identification of microginins was based on the characteristic fragment ions of the unique microginin amino acid 3-amino-2-hydroxy-decanoic acid (Ahda) and its modified forms. The analysis of fragmentation spectra revealed 51 microginin structures, including 36 new variants. This article provides the dataset of fragmentation mass spectra of the microginins detected in cyanobacteria from Greek freshwaters. As this class of cyanopeptides is produced by cyanobacteria from different geographical regions, the aim of this dataset is to enable the identification of microginins in future studies and therefore to contribute to a better evaluation of their presence in freshwater bodies worldwide.


a b s t r a c t
Microginins are the less common class of bioactive linear cyanobacterial peptides. Recently, an investigation for their presence in cyanobacteria from Greek freshwaters and strain cultures was carried out. The present dataset is related to the research article "New microginins from cyanobacteria of Greek freshwaters" [1] . Cyanobacterial biomass from bloom samples and cultured strains were extracted with aqueous methanol. Extracts were analysed by liquid chromatography coupled to hybrid triple quadrupole/linear ion trap mass spectrometer (LC-qTRAP MS/MS) in information dependent acquisition (IDA) mode. Enhanced ion product (EIP) mode was applied for the collection of ion fragmentation spectra. Identification of microginins was based on the characteristic fragment ions of the unique microginin amino acid 3-amino-2-hydroxy-decanoic acid (Ahda) and its modified forms. The analysis of fragmentation spectra revealed 51 microginin structures, including 36 new variants. This article provides the dataset of fragmentation mass spectra of the microginins detected in cyanobacteria from Greek freshwaters. As this class of cyanopeptides is produced by cyanobacteria from different geographical regions, the aim of this dataset is to enable the identification of microginins in future studies and therefore to contribute to a better evaluation of their presence in freshwater bodies worldwide.

Value of the Data
• The data represents a useful library of fragmentation mass spectra for a large number of microginins. • Due to the absence of analytical standards for microginins, the dataset can be used as reference for their identification through LC-MS/MS analysis by research groups working in this field. • The mass spectral dataset will enable studies related to the occurrence of microginins and investigations into their bio-activities. • The dataset can also be used in retrospective mass spectral analysis of cyanobacterial biomass or bloom samples to reveal the presence of microginins. • The provided dataset sheds light to the metabolomic potential of cyanobacteria.
• The dataset presented in this article is a useful tool for research groups in the field of environmental chemistry, biology and biochemistry, especially for those working on cyanobacterial bioactive metabolites. Identification of microginins will also enable their isolation and purification to be used as reference standards for water laboratories and lake authorities.

Data Description
The dataset contains the fragmentation mass spectra obtained during the study of occurrence of microginins in cyanobacterial bloom samples and strain cultures from Greek freshwaters [1] . Samples were analysed using a hybrid triple quadrupole/linear ion trap mass spectrometer after liquid chromatography separation (LC-qTRAP MS/MS) and the fragmentation spectra of a large number of microginins -including new variants -were obtained.
In total, fifty-one microginins' structures were elucidated and their mass fragmentation spectra as well as their structural formula are included in the dataset ( Figs. 1-47 ). The spectra of two microginins with new proposed 3-amino-2-hydroxy-decanoic acid (Ahda) modification, and two microginins with not fully elucidated structures, which are included in the research article [1] are not presented here. The presented microginin variants consist of four or five amino acids.                                               Identification and structural elucidation of the peptides were based on characteristic fragment ions of Ahda moiety, immonium ions, characteristic losses of C-terminal amino acid, and other diagnostic ions related to amino acids sequence. Diagnostic fragment ions formed by Ahda and its variants were m/z 128 for Ahda fragment (C 8 H 18 N), m/z 142 for MeAhda fragment (C 9 H 20 N) [2] , m/z 162 for Cl-Ahda fragment (C 8 H 17 NCl) and m/z 196 for Cl 2 -Ahda fragment (C 8 H 16 NCl 2 ) [3] . Distinction between methyltyrosine (MeTyr) and homotyrosine (Htyr), which are isobaric compounds having the same chemical formula (C 10 H 13 NO 3 ) could not be carried out using the applied MS/MS methodology. The same stands for amino acids leucine (Leu) and isoleucine (Ile) and their methylated units. For this reason, both amino acids are annotated in the given sequences. Further details on the structure elucidation process are described in [1] .

Cyanobacterial cells extraction
In order to release the cell-bond microginins, cyanobacterial cells were extracted with aqueous methanol. For this purpose, 1.5 ml of methanol:water (75%: 25%) was added to ∼10 mg of lyophilized cyanobacterial biomass and mixed thoroughly by vortexing before sonication in ice bath for 15 min. Samples were centrifuged at 10,0 0 0 rpm for 15 min. The collected supernatant extracts were additionally centrifuged at 10,0 0 0 rpm for 5 min prior to LC-MS/MS analysis.

LC-qTRAP MS/MS analysis
Cyanobacterial extracts were analyzed by an Agilent 1200, liquid chromatography apparatus (Agilent Technologies, Waldboronn, Germany) coupled online to a hybrid triple quadrupole/linear ion trap mass spectrometer (QTRAP5500, Applied Biosystems, Sciex; Concorde, Ontario, Canada) according to Mazur-Marzec et al. [4] . Briefly, 5 μL of extracts were injected in a reversed-phase column (Zorbax Eclipse XDB-C18, 4.6 × 150 mm, 5 μm, Agilent Technologies, Santa Clara, CA, USA) and microginins were separated within 13 min by a gradient program with mobile phase composed of (A) acetonitrile and (B) 5% acetonitrile in MilliQ water, both containing 0.1% formic acid, at a flow rate of 0.6 mL/min. Gradient program was starting with 15% A, which was linearly increased to 75% in 5 min, then to 90% in the next 5 min, held for 5 min and brought back to 15% A in 1 min for equilibration. ESI positive ionization was applied at IonSpray voltage 5500, ion source temperature 550 °C and curtain gas (CUR) 20. For the detection of microginins information dependent acquisition (IDA) mode was applied, while the ion fragmentation spectra were collected in enhanced ion product (EIP) mode. In the IDA mode, a full scan from 500 to 1200 Da was acquired and, if the signal of an ion was above a threshold of 10 4 cps, EIP mode was triggered and the ion was fragmented in the collision cell (Q2). Fragmentation spectra were acquired from 50 to 10 0 0 Da with a scan speed of 20 0 0 Da/s and collision energy (CE) of 60 eV with collision energy spread (CES) of 20 eV, declustering potential (DP) 80. Data acquisition and processing were carried out using Analyst QS® 1.5.1 software. Fragmentation spectra obtained by LC-qTRAP MS/MS were examined in order to identify microginins present in the samples and to elucidate their structures.

Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships which have, or could be perceived to have, influenced the work reported in this article.