Method of localizing lipid double bonds

Patent metadata

Field	Value
Publication number	US-10043645-B2
Application number	US-201515304634-A
Country	US
Kind code	B2
Filing date	Apr 14, 2015
Priority date	Apr 17, 2014
Publication date	Aug 7, 2018
Grant date	Aug 7, 2018

Abstract

A method of mass spectrometry for analyzing lipids and similar biological molecules is disclosed. The lipid molecules may be ionized to form a plurality of lipid parent ions and subjected to photon-induced fragmentation to form a plurality of fragment or product ions. The position of one or more unsaturated bonds in the lipid molecules may be determined by mass analyzing the fragment and product ions and analyzing their intensity profile.

First claim

The invention claimed is:

1. A method of mass spectrometry comprising:
ionising lipid molecules to form a plurality of lipid parent ions;
subjecting said lipid parent ions to photon-induced fragmentation in order to cause said lipid parent ions to fragment to form a plurality of fragment or product ions;
mass analysing said fragment or product ions, wherein subjecting said lipid parent ions to photon-induced fragmentation causes said lipid parent ions to fragment directly or indirectly; and
determining the position of one or more unsaturated bonds in said lipid molecules by analysing an intensity profile of fragment or product ions that correspond with cleavage of carbon-carbon bonds from the end of a hydrocarbon chain of the lipid up to the position of an unsaturated bond within said chain, wherein analysing said intensity profile of said fragment or product ions in order to determine the position of one or more unsaturated bonds in said lipid molecules comprises comparing said intensity profile to one or more previous experimentally obtained intensity profiles or comparing said intensity profile to a predicted, calculated or theoretical intensity profile.

2. A method as claimed in claim 1 , wherein said fragment or product ions are multiply or substantially doubly charged.

3. A method as claimed in claim 1 , wherein the step of subjecting said lipid parent ions to photon-induced fragmentation comprises directing photons emitted from an incoherent light source or non-laser light source onto said lipid parent ions.

4. A method as claimed in claim 1 , wherein said lipid parent ions are caused to fragment via photon induced electron detachment.

5. A method as claimed in claim 1 , wherein said lipid molecules comprise one or more triglycerols, glycerophospholiids, sphingolipids, fatty acids, glycerolipids or saccharolipids.

6. A method as claimed in claim 1 , further comprising confining said lipid parent ions in an ion guide whilst subjecting said lipid parent ions to photon-induced fragmentation.

7. A method as claimed in claim 1 , wherein said lipid parent ions comprise a first charge state and wherein said fragment or product ions comprise a second different charge state or comprise a second charge state that is a higher positive charge state or more positive than said first charge state.

8. A method as claimed in claim 1 , wherein said lipid parent ions are substantially singly charged.

9. A method as claimed in claim 1 , wherein the step of subjecting said lipid parent ions to photon-induced fragmentation causes said lipid parent ions to fragment by photon induced electron detachment, photodissociation or photo-activation.

10. A method as claimed in claim 1 , further comprising causing at least some of said lipid parent ions to interact with excited neutral gas molecules or causing at least some of said lipid parent ions to form radical ions and/or metastable ions.

11. A method as claimed in claim 10 , wherein said radical ions or metastable ions subsequently dissociate to form said fragment or product ions.

12. A method as claimed in claim 1 , wherein the step of subjecting said lipid parent ions to photon-induced fragmentation comprises subjecting said lipid parent ions to ultraviolet radiation.

13. A method as claimed in claim 1 , wherein the step of subjecting said lipid parent ions to photon-induced fragmentation comprises directing photons emitted from a vacuum ultraviolet (“VUV”) discharge lamp, a glow discharge lamp, an ultraviolet lamp, a lamp onto said lipid parent ions.

14. A method as claimed in claim 1 , wherein the step of analysing said intensity profile of said fragment or product ions in order to determine the position of one or more bonds in said lipid molecules comprises determining the position of one or more C═C double bonds, carbon double bonds or vinyl bonds in said lipid molecules.

15. A method as claimed in claim 1 , further comprising subjecting at least some of said lipid parent ions or said plurality of fragment or product ions to supplementary activation to form a plurality of further fragment or product ions and mass analysing said further fragment or product ions.

16. A method as claimed in claim 15 , further comprising selecting by mass or using a mass filter one or more of said lipid parent ions or one or more ions derived from said lipid parent ions prior to the step of supplementary activation.

17. A method as claimed in claim 1 , further comprising separating at least some of said lipid parent ions, at least some ions derived from said lipid parent ions or at least some fragment or product ions according to ion mobility prior to mass analysis.

18. A mass spectrometer comprising:
an ion source arranged and adapted to ionise lipid molecules to form a plurality of lipid parent ions;
a photon-induced fragmentation device arranged and adapted to subject said lipid parent ions to photon-induced fragmentation in order to cause said lipid parent ions to fragment to form a plurality of fragment or product ions, wherein subjecting said lipid parent ions to photon-induced fragmentation causes said lipid parent ions to fragment directly or indirectly;
a mass analyser arranged and adapted to mass analyse said fragment or product ions; and
a control system arranged and adapted to determine the position of one or more unsaturated bonds in said lipid molecules by analysing an intensity profile of fragment or product ions that correspond with cleavage of carbon-carbon bonds from the end of a hydrocarbon chain of the lipid up to the position of an unsaturated bond within said chain, wherein analysing said intensity profile of said fragment or product ions in order to determine the position of one or more unsaturated bonds in said lipid molecules comprises comparing said intensity profile to one or more previous experimentally obtained intensity profiles or comparing said intensity profile to a predicted, calculated or theoretical intensity profile.

Assignees

• Micromass Ltd

Inventors

• Green Martin Raymond
• Richardson Keith

Classifications

• H01J49/0059 Primary

  by a photon beam, photo-dissociation · CPC title

• G01N33/92

  involving lipids, e.g. cholesterol {, lipoproteins, or their receptors (steroid hormones G01N33/743)} · CPC title

• G01B15/00

  Measuring arrangements characterised by the use of electromagnetic waves or particle radiation, e.g. by the use of microwaves, X-rays, gamma rays or electrons (characterised by the use of optical techniques G01B9/00, G01B11/00) · CPC title

• H01J49/0031

  Step by step routines describing the use of the apparatus (H01J49/0081 takes precedence) · CPC title