The phenomenon of ion mobility (IM), the movement/transport of charged particles under the influence of an electric field, was first observed in the early 20th Century and harnessed later in ion mobility spectrometry (IMS). There have been rapid advances in instrumental design, experimental methods, and theory together with contributions from computational chemistry and gas‐phase ion chemistry, which have diversified the range of potential applications of contemporary IMS techniques. Whilst IMS‐mass spectrometry (IMS‐MS) has recently been recognized for having significant research/applied industrial potential and encompasses multi‐/cross‐disciplinary areas of science, the applications and impact from decades of research are only now beginning to be utilized for “small molecule” species. This review focuses on the application of IMS‐MS to “small molecule” species typically used in drug discovery (100–500 Da) including an assessment of the limitations and possibilities of the technique. Potential future developments in instrumental design, experimental methods, and applications are addressed. The typical application of IMS‐MS in relation to small molecules has been to separate species in fairly uniform molecular classes such as mixture analysis, including metabolites. Separation of similar species has historically been challenging using IMS as the resolving power, R, has been low (3–100) and the differences in collision cross‐sections that could be measured have been relatively small, so instrument and method development has often focused on increasing resolving power. However, IMS‐MS has a range of other potential applications that are examined in this review where it displays unique advantages, including: determination of small molecule structure from drift time, “small molecule” separation in achiral and chiral mixtures, improvement in selectivity, identification of carbohydrate isomers, metabonomics, and for understanding the size and shape of small molecules. This review provides a broad but selective overview of current literature, concentrating on IMS‐MS, not solely IMS, and small molecule applications. © 2012 Wiley Periodicals, Inc., Mass Spec Rev 32:43–71, 2013

Antisense oligonucleotides (ASOs) and small interfering RNA (siRNA) promise specific correction of disease-causing gene expression. Therapeutic implementation, however, has been forestalled by poor delivery to the appropriate tissue, cell type, and subcellular compartment. Topical administration is considered to circumvent these issues. The availability of inhalation devices and unmet medical need in lung disease has focused efforts in this tissue. We report the development of a novel cell sorting method for quantitative, cell type-specific analysis of siRNA, and locked nucleic acid (LNA) ASO uptake and efficacy after intratracheal (i.t.) administration in mice. Through fluorescent dye labeling, we compare the utility of this approach to whole animal and whole tissue analysis, and examine the extent of tissue distribution. We detail rapid systemic access and renal clearance for both therapeutic classes and lack of efficacy at the protein level in lung macrophages, epithelia, or other cell types. We nevertheless observe efficient redirection of i.t. administered phosphorothioate (PS) LNA ASO to the liver and kidney leading to targeted gene knockdown. These data suggest delivery remains a key obstacle to topically administered, naked oligonucleotide efficacy in the lung and introduce inhalation as a potentially viable alternative to injection for antisense administration to the liver and kidneys.

14Cellular Biology, University of Leeds, LS2 9JT, UK Electrospray ion mobility-mass spectrometry (IM-MS) data show that for some small 21 molecules, two (or even more) ions with identical sum formula and mass, but distinct drift 22

RATIONALE Ion mobility spectrometry‐mass spectrometry (IMS‐MS) offers an opportunity to combine measurements and/or calculations of the collision cross‐sections and subsequent mass spectra with computational modelling in order to derive the three‐dimensional structure of ions. IMS‐MS has previously been reported to separate two components for the compound norfloxacin, explained by protonation on two different sites, enabling the separation of protonated isomers (protomers) using ion mobility with distinguishable tandem mass spectrometric (MS/MS) data. This study reveals further insights into the specific example of norfloxacin and wider implications for ion mobility mass spectrometry. METHODS Using a quadrupole ion mobility time‐of‐flight mass spectrometer, the IMS and MS/MS spectra of norfloxacin were recorded and compared with theoretical calculations using molecular modelling (density functional theory), and subsequent collision cross‐section calculations using projection approximation. RESULTS A third significant component in the ion mobilogram of norfloxacin was observed under similar experimental conditions to those previously reported. The presence of the new component is convoluted by co‐elution with another previously observed component. CONCLUSIONS This case demonstrates the potential of combined IMS‐MS/MS with molecular modelling information for increased understanding of 'small‐molecule' fragmentation pathways. Copyright © 2013 John Wiley & Sons, Ltd.