Surface acoustic wave nebulization facilitating lipid mass spectrometric analysis.
ABSTRACT Surface acoustic wave nebulization (SAWN) is a novel method to transfer nonvolatile analytes directly from the aqueous phase to the gas phase for mass spectrometric analysis. The lower ion energetics of SAWN and its planar nature make it appealing for analytically challenging lipid samples. This challenge is a result of their amphipathic nature, labile nature, and tendency to form aggregates, which readily precipitate clogging capillaries used for electrospray ionization (ESI). Here, we report the use of SAWN to characterize the complex glycolipid, lipid A, which serves as the membrane anchor component of lipopolysaccharide (LPS) and has a pronounced tendency to clog nano-ESI capillaries. We also show that unlike ESI SAWN is capable of ionizing labile phospholipids without fragmentation. Lastly, we compare the ease of use of SAWN to the more conventional infusion-based ESI methods and demonstrate the ability to generate higher order tandem mass spectral data of lipid A for automated structure assignment using our previously reported hierarchical tandem mass spectrometry (HiTMS) algorithm. The ease of generating SAWN-MS(n) data combined with HiTMS interpretation offers the potential for high throughput lipid A structure analysis.
Article: Surface Acoustic Wave Microfluidics[Show abstract] [Hide abstract]
ABSTRACT: Fluid manipulations at the microscale and beyond are powerfully enabled through the use of 10-1,000-MHz acoustic waves. A superior alternative in many cases to other microfluidic actuation techniques, such high-frequency acoustics is almost universally produced by surface acoustic wave devices that employ electromechanical transduction in wafer-scale or thin-film piezoelectric media to generate the kinetic energy needed to transport and manipulate fluids placed in adjacent microfluidic structures. These waves are responsible for a diverse range of complex fluid transport phenomena - from interfacial fluid vibration and drop and confined fluid transport to jetting and atomization - underlying a flourishing research literature spanning fundamental fluid physics to chip-scale engineering applications. We highlight some of this literature to provide the reader with a historical basis, routes for more detailed study, and an impression of the field's future directions.Annual Review of Fluid Mechanics 01/2013; 46(1). · 11.26 Impact Factor
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ABSTRACT: Mass spectrometry (MS) has emerged as an important tool to investigate non-covalent interactions between proteins and various ligands (e.g., other proteins, small molecules or drugs). In particular, electrospray ionisation (ESI) under so-called "native conditions" (a.k.a. "native MS") has considerably expanded the scope of such investigations. For instance, ESI quadrupole time of flight (Q-TOF) instruments have been used to probe the precise stoichiometry of protein assemblies, the interactions between subunits and the position of subunits within the complex (i.e., defining core and peripheral subunits). This review highlights several illustrative native Q-TOF-based investigations and recent seminal contributions of top-down MS [i.e., Fourier transform (FT) MS]) to the characterisation of non-covalent complexes. Combined top-down and native MS, recently demonstrated in "high-mass modified" orbitrap mass spectrometers, and further improvements needed for the enhanced investigation of biologically significant non-covalent interactions by MS will be discussed. This article is protected by copyright. All rights reserved.Proteomics 04/2014; 14(10). · 3.97 Impact Factor
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ABSTRACT: Here we implement ultraviolet photodissociation (UVPD) in an online liquid chromatographic MS/MS strategy to support analysis of complex mixtures of lipid A combinatorially modified during development of vaccine adjuvants. 193 nm UVPD mass spectrometry was utilized to characterize the structures and fragment ion types of lipid A from Escherichia coli, Vibrio cholerae and Pseudomonas aeruginosa using an Orbitrap mass spectrometer. The fragment ions generated by UVPD were compared to those from collision induced dissociation (CID) and higher energy collision dissociation (HCD) with respect to the precursor charge state. UVPD afforded the widest array of fragment ions types including acyl chain C-O, C-N and C-C bond cleavages and glycosidic C-O and cross ring cleavages, thus providing the most comprehensive structural analysis of the lipid A. UVPD exhibited virtually no dependence on precursor ion charge state and was best at determining lipid A structure including acyl chain length and composition, giving it an advantage over collision based methods. UVPD was incorporated into an LC-MS/MS methodology for the analysis of a number of structural variants in a complex mixture of combinatorially engineered Escherichia coli lipid A.Analytical Chemistry 01/2014; · 5.83 Impact Factor