Ion Mobility–Mass Spectrometry Approach for the Comparison of Sheep and Goat Milk Lipidomes
, Viviana Garau 2, Margherita Addis 3, Ignazio Ibba 4 and Pierluigi Caboni 1,*Round 1
Reviewer 1 Report
Review
Comments for author File: 
Comments.pdf
Author Response
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Author Response File: 
Author Response.docx
Reviewer 2 Report
The manuscript entitled "Ion mobility mass spectrometry approach for the comparison of 2 sheep and goat milk lipidome" by Manis et al describes the analysis of lipids present in sheep and goat milk using three parameters for separation, namely retention time by LC, m/z value by MS and drift time/CCS by IMS.
The manuscript is overall well-written and describes the results of the conducted analyses concisely. The combination of mass spectrometry, liquid chromatograhy and ion mobility spectrometry is a valuable tool for the comprehensive analysis of the complex lipidome of milk samples.
Before publication of the manuscript, the authors should address the following points:
The introduction contains a lot of information about the structural behaviour of lipids in the liquid phase but this is not particularly relevant to the manuscript. I would suggest to add information on previous literature about lipidomic analysis of milk and other biological fluids outlining the difficulties that such complex samples show. Furthermore, I advise to expand the introduction of ion mobility spectrometry and to reference some of the research on lipids that has been published using IMS.
Did the authors analyze quality control samples to ensure the stability and reproducibility of the measurements? If so, please state in the Materials and Methods section. If QC samples were not analyzed, the authors should explain, how else they made sure that the system works properly.
The statement that "It is generally accepted that for collision induced dissociation-based MS/MS 173 acquisition, more energy is required to cleave the sn-2 FA as compared to sn-1/sn-3 FA", in Chapter 3.2 needs a reference.
Please enlarge the font size in all figures to increase legibility. Also, please incorporate the letters A and B into the figures so that the description does not shift to another page. The readability of Figure 4 is also not sufficient. I suggest to arrange the bars in a downward fashion and enlarge the fonts, or to move the figure to the supplementing material and to mention the main findings in the text.
The description of fatty acids uses both the names of the acids as well as the carbon and double bond configuration. In the diagrams, only #C and #DB are given, which is fine. But when discussing the figures in the text, it would be helpful to mention both the name and #C and #DB to facilitate the reader following the authors explanation.
The manuscript often mentions the usefulness of IMS, but no spectra are depicted. Especially for showing the advantages of the method to discriminate TAG isomers, it would be very helpful to present the experimental data. Also, please elaborate if IMS is potentially useful to discriminate SM lipids with many isomers as mentioned in line 238-241.
Minor points:
Line 17: The sentence starting with "While, ..." should be connected to the previous one. Please rephrase.
line 54: ....despite the use of high throughput mass spectrometers IT is difficult to....
line 160: In this table TAGs were noT reported but discusseD successively.
line 167: Considering the nutritional importanCE of FA position at the glycerol backbone
line 253: specieS
line 261: concernS
line 300: The conclusions chapter should be 5.
Author Response
Please see the attachment
Author Response File: Author Response.docx
