Enhancements in travelling wave ion mobility resolution

The use of ion mobility separation to determine the collision cross-section of a gas-phase ion can provide valuable structural information. The introduction of travelling-wave ion mobility within a quadrupole/time-of-flight mass spectrometer has afforded routine collision cross-section measurements to be performed on a range of ionic species differing in gas-phase size/structure and molecular weight at physiologically relevant concentrations. Herein we discuss the technical advances in the second-generation travelling-wave ion mobility separator, which result in up to a four-fold increase in mobility resolution. This improvement is demonstrated using two reverse peptides (mw 490 Da), small ruthenium-containing anticancer drugs (mw 427 Da), a cisplatin-modified protein (mw 8776 Da) and the noncovalent tetradecameric chaperone complex GroEL (mw 802 kDa). What is also shown are that the collision cross-sections determined using the second-generation mobility separator correlate well with the previous generation and theoretically derived values.

Pulmonary injury after combined exposures to low-dose low-LET radiation and fungal spores

Exposure to infectious microbes is a likely confounder after a nuclear terrorism event. In combination with radiation, morbidity and mortality from an infection may increase significantly. Pulmonary damage after low-dose low-LET irradiation is characterized by an initial diffuse alveolar inflammation. By contrast, inhaled fungal spores produce localized damage around pulmonary bronchioles. In the present study, we assessed lung injury in C57BL/6 mice after combined exposures to whole-body X radiation and inhaled fungal spores. Either animals were exposed to Aspergillus spores and immediately irradiated with 2 Gy, or the inoculation and irradiation were separated by 8 weeks. Pulmonary injury was assessed at 24 and 48 h and 1, 2, 4, 8, and 24 weeks later using standard H&E-stained sections and compared with sham-treated age-matched controls. Immunohistochemistry for invasive inflammatory cells (macrophages, neutrophils and B and T lymphocytes) was performed. A semi-quantitative assessment of pulmonary injury was made using three distinct parameters: local infiltration of inflammatory cells, diffuse inflammation, and thickening and distortion of alveolar architecture. Radiation-induced changes in lung architecture were most evident during the first 2 weeks postexposure. Fungal changes were seen over the first 4 weeks. Simultaneous combined exposures significantly increased the duration of acute pulmonary damage up to 24 weeks (P < 0.01). In contrast, administration of the fungus 8 weeks after irradiation did not produce enhanced levels of acute pulmonary damage. These data imply that the inhalation of fungal spores at the time of a radiation exposure alters the susceptibility of the lungs to radiation-induced injury.

Sites of metabolic substitution: investigating metabolite structures utilising ion mobility and molecular modelling

Drug metabolism is an integral part of the drug development and drug discovery process. It is required to validate the toxicity of metabolites in support of safety testing and in particular provide information on the potential to form pharmacologically active or toxic metabolites. The current methodologies of choice for metabolite structural elucidation are liquid chromatography/tandem mass spectrometry (LC/MS/MS) and nuclear magnetic resonance (NMR) spectroscopy. There are, in certain cases, examples of metabolites whose sites of metabolism cannot be unequivocally identified by MS/MS alone. Utilising commercially available molecular dynamics packages and known quantum chemistry basis sets, an ensemble of lowest energy structures were generated for a group of aromatic hydroxylated metabolites of the model compound ondansetron. Theoretical collision cross-sections were calculated for each structure. Travelling-wave ion mobility (IMS) measurements were also performed on the compounds, thus enabling experimentally derived collision cross-sections to be calculated. A comparison of the theoretical and experimentally derived collision cross-sections were utilised for the accurate assignment of isomeric drug metabolites. The UPLC/IMS-MS method, described herein, demonstrates the ability to measure reproducibly by ion mobility, metabolite structural isomers, which differ in collision cross-section, both theoretical and experimentally derived, by less than 1 Å(2). This application has the potential to supplement and/or complement current methods of metabolite structural characterisation.

Shape changes induced by N-terminal platination of ubiquitin by cisplatin

The three-dimensional conformation of a protein is an important property and plays a key role in its biological activity. We show here that ion mobility-mass spectrometry (IM-MS) can be used to detect conformational changes in the protein ubiquitin in the gas phase induced by reaction with the anticancer drug cisplatin. The primary adduct was ubiquitin-{Pt(NH(3))(2)} under denaturing conditions. Up to three different conformations appear to be generated upon platination depending on the charge state. The collision cross-sections (Omega) for each conformation indicate that the conformations of the platinated protein are contracted in size compared with unmodified ubiquitin with generally smaller Omega values. Ion mobility-tandem MS allowed determination of the platinum binding site without a requirement for prior chromatographic separation. A rapid 30-min digestion of cisplatin-modified ubiquitin with trypsin allowed the platination site to be identified as the N-terminal methionine following low-energy collision-induced dissociation (CID) studies of the modified peptide. The data were generated using a Traveling-Wave based ion mobility-MS approach. Such cisplatin-induced shape changes may have a significant effect on its function in vivo. This work highlights the usefulness of the ion-mobility mass spectrometry technique for shedding new light on such protein interactions.

Identifying drug metallation sites on peptides using electron transfer dissociation (ETD), collision induced dissociation (CID) and ion mobility-mass spectrometry (IM-MS)

Electron transfer dissociation (ETD) and collision induced dissociation (CID) have been used to locate the precise binding sites for platinum and ruthenium anticancer complexes on the peptide Substance P. We show that ETD combined with ion mobility-mass spectrometry significantly reduces mass spectral complexity and improves the S/N of the product-ions formed.

Use of ion mobility mass spectrometry and a collision cross-section algorithm to study an organometallic ruthenium anticancer complex and its adducts with a DNA oligonucleotide

We report the development of an enhanced algorithm for the calculation of collision cross-sections in combination with Travelling-Wave ion mobility mass spectrometry technology and its optimisation and evaluation through the analysis of an organoruthenium anticancer complex [(eta6-biphenyl)Ru(II)(en)Cl]+. Excellent agreement was obtained between the experimentally determined and theoretically determined collision cross-sections of the complex and its major product ion formed via collision-induced dissociation. Collision cross-sections were also experimentally determined for adducts of this ruthenium complex with the single-stranded oligonucleotide hexamer d(CACGTG). Ion mobility tandem mass spectrometry measurements have allowed the binding sites for ruthenium on the oligonucleotide to be determined.

Hot electron capture dissociation distinguishes leucine from isoleucine in a novel hemoglobin variant, Hb Askew, beta54(D5)Val-->Ile

Population migration has led to the global dispersion of human hemoglobinopathies and has precipitated a need for their identification. An effective mass spectrometry-based procedure involves analysis of the intact alpha- and beta-globin chains to determine their mass, followed by location of the variant amino acid residue by direct analysis of the enzymatically digested chains and low-energy collision induced dissociation of the variant peptide. Using this procedure, a variant was identified as either beta54Val-->Leu or beta54Val-->Ile, since the amino acids leucine and isoleucine cannot be distinguished using low-energy collisions. Here, we describe how hot electron capture dissociation on a Fourier transform-ion cyclotron resonance mass spectrometer was used to distinguish isoleucine from leucine and identify the mutation as beta54(D5)Val-->Ile. This is a novel variant, and we have named it Hb Askew.

Hb Leeds [β56(D7)Gly→Cys]: A New Hemoglobin that Aggravates Anemia in a child with β0-Thalassemia Trait

A novel beta chain variant found in combination with beta(0)-thalassemia (thal) was identified in a male infant by electrospray ionization mass spectrometry (ESI-MS). Analysis of the infant's denatured blood and a 30 min. tryptic digest of his blood identified the mutation as beta56(D7)Gly-->Cys, which was confirmed by tandem mass spectrometry (MS/MS). We have named this new variant Hb Leeds. The infant's parents, resident in Yorkshire, UK, but originally from Pakistan, were found to have beta(0)-thalassemia (thal) trait (mother) and Hb Leeds trait (father). Hematological data on the infant's parents and siblings are given. Hb Leeds trait was also found in three unrelated Pakistani adults living in the same area of Yorkshire. Hb Leeds trait in adults appears to have few clinical manifestations, but when combined with beta(0)-thal it led to a more severe anemia in the infant than in the corresponding thalassemic trait in his mother.

Isomer separation and gas-phase configurations of organoruthenium anticancer complexes: ion mobility mass spectrometry and modeling

We have used ion mobility-mass spectrometry combined with molecular modeling for the separation and configurational analysis of three low-molecular-weight isomeric organoruthenium anticancer complexes containing ortho-, meta-, or para-terphenyl arene ligands. The isomers were separated using ion mobility based on traveling-wave technology and the experimentally determined collision cross sections were compared to theoretical calculations. Excellent agreement was observed between the experimentally and theoretically derived measurements.

From small acorns--developing a laparoscopic colorectal surgical service

INTRODUCTION

Randomised controlled trials have shown that laparoscopic colorectal surgery is equal in terms of safety to open surgery. Benefits have been seen for length of stay, blood loss, immune suppression and analgesia requirements. The aim of this study was to assess the safety and feasibility of introducing laparoscopic colorectal surgery to our unit.

PATIENTS AND METHODS

Prospectively collected cases of all patients undergoing laparoscopic colorectal surgery between July 2003 and July 2007 were reviewed.

RESULTS

A total of 143 patients (75 males and 68 females) with a mean age of 65.8 years (range, 21-95 years) underwent surgery. Laparoscopic resection for colorectal malignancy was performed in 93 patients (65%). The conversion rate for all cases was 14.7%. Mean operative time was 203 min (range, 100-400 min), with a mean blood loss of 180 ml. The mean number of lymph nodes in malignant cases was 13.8 with clear resection margin in all but one case. The mean postoperative stay was 5.6 days (median, 4 days; range, 2-35 days). UKCCR standard for lymph node retrieval was achieved in 62.6% of cases. There were four postoperative deaths. The overall 30-day morbidity rate was 21.7%. The service is consultant-led with 9.8% of cases performed by senior trainees and 37% of procedures performed by two consultants.

CONCLUSIONS

Laparoscopic colorectal surgery is technically feasible and safe in our hands. Although operative time is longer, this is counterbalanced by shorter hospital stay. The results from this series support the findings of others and continuing development of this service.

Ion mobility augments the utility of mass spectrometry in the identification of human hemoglobin variants

The global dispersion of hemoglobin variants through population migration has precipitated a need for their identification. A particularly effective mass spectrometry (MS)-based procedure involves analysis of the intact globin chains in diluted blood to detect the variant through mass anomalies, followed by location of the variant amino acid residue by direct analysis of the enzymatically digested globins. Here we demonstrate the use of ion mobility separation in combination with this MS procedure to reduce mass spectral complexity. In one example, the doubly charged tryptic peptide from a low abundance variant (4%) occurred at the same m/z value as a singly and a doubly charged interfering ion. In another example, the singly charged tryptic peptide from an alpha-chain variant (26%) occurred at the same m/z value as a doubly charged interfering ion. Ion mobility was used to separate the variant ions from the interfering ions, thus allowing the variant peptides to be observed and sequenced by tandem mass spectrometry.

Spatial and temporal variations of meiofaunal communities from the western sector of the Gulf of Batabanó, Cuba: III. Vertical distribution

The vertical distribution of meiofauna within subtidal sediments was studied in four stations pertaining to mangrove or muddy flats habitats. In 2003, replicated samples were taken in dry (February) and wet (July) seasons at the Bacunagua Inlet, southwestern coast of Cuba. The abundance and number of meiofaunal taxa exhibited a vertical gradient possibly due to changes in the concentrations of oxygen and hydrogen sulphide, rather than food availability along this gradient. Nematodes are capable of distributing themselves throughout the whole sediment column due to their ability to tolerate reducing conditions; however depletion of communities along depth was evident. Their presence in deeper sediments (6 - 10 cm) suggests that certain species are adequately adapted to spend their entire life cycle in these harsh environments (where soluble tannins and decomposing organic matter predominate). Copepods showed a strong limitation to vertical distribution (concentrating in the top 2 cm), possibly in response to a sharp vertical decline in oxygenation within these organically enriched sediments.

Nociceptin and urotensin-II concentrations in critically ill patients with sepsis

BACKGROUND

The systemic inflammatory response to infection (sepsis) involves widespread organ dysfunction, including changes in immune modulation, cardiovascular derangements, and neural activation. Two neuropeptide/receptor systems, nociceptin/orphanin FQ (N/OFQ) which acts at the non-classical opioid receptor NOP and urotensin-II (U-II) which acts at the urotensin receptor (UT), have been implicated in neural, immune, and cardiovascular system function. In this study, we make measurements of these peptides in critically ill patients.

METHODS

Plasma samples from 21 critically ill patients with sepsis were collected over four consecutive days. Plasma N/OFQ and U-II concentrations were determined by radioimmunoassay and compared with biochemical and clinical markers of illness severity, including serum creatinine, bilirubin, platelet and white cell counts, admission APACHE II and serial SOFA scores.

RESULTS

Median (inter-quartile range) admission plasma N/OFQ concentrations in sepsis were higher in patients who died within 30 days (n=4) compared with survivors (n=17); 3.0 (2.5-5.0) vs 1.0 (1.0-2.5) pg ml(-1) (P=0.028). Plasma N/OFQ concentrations were increased in a subgroup of five patients who had undergone major gastrointestinal surgery. There were no significant changes in plasma U-II concentrations. There were no correlations between plasma U-II and N/OFQ concentrations and markers of illness severity and organ system dysfunction.

CONCLUSIONS

Plasma N/OFQ concentrations were increased in critically ill patients with sepsis who had undergone major gastrointestinal surgery and in patients who subsequently died. Further work is required to clarify the significance of plasma N/OFQ concentrations in sepsis.

Coupling desorption electrospray ionisation and neutral desorption/extractive electrospray ionisation with a travelling-wave based ion mobility mass spectrometer for the analysis of drugs

Desorption electrospray ionisation (DESI) and neutral desorption/extractive electrospray ionisation (EESI) have been coupled to a hybrid quadrupole travelling-wave (T-Wave)-based ion mobility time-of-flight mass spectrometer for the direct accurate mass analysis of active ingredients formulated into pharmaceutical samples. The collision cross-section measurements of polyethylene glycol (PEG) excipients detected in one formulation were estimated and compared with published data. These estimated collision cross-sections of the PEG species showed good agreement with published data.

Prediction of product ion isotope ratios in the tandem electrospray ionization mass spectra from the second isotope of tryptic peptides: identification of the variant beta 131 Gln-->Glu, hemoglobin Camden

Many human hemoglobin variants occur in heterozygotes; that is, the variant and normal hemoglobins are present in the same sample. In a procedure for rapidly identifying such variants by mass spectrometry, mutations that increase the mass by 1 Da require a special approach. One of the steps in this procedure involves digesting the denatured hemoglobin with trypsin and analyzing the resulting peptide mixture by mass spectrometry to identify the mutant peptide. Generally the mutant peptide ion can then be selected as the precursor and sequenced by tandem mass spectrometry to identify or confirm the mutation. However, with heterozygotes in which the mass of the variant is 1 Da higher than normal, the first isotope of the mutant peptide occurs at essentially the same mass as the second isotope of the normal peptide, precluding analysis of the mutant peptide on its own. Product ions from the second isotope of a peptide are doublets, 1 Da apart. The way in which the relative abundance of the components in these doublets varies with the elemental composition of the product ions was predicted from the isotopic abundance of the elements and agreed well with experimental data. These results were applied to the identification of a variant that increases the mass by 1 Da in a heterozygote-that is, beta 131 Gln-->Glu, hemoglobin Camden.

Novel software for the assignment of peaks from tandem mass spectrometry spectra of synthetic polymers

Novel software has been developed to aid the interpretation of tandem mass spectrometry (MS/MS) data from synthetic polymers. The software is particularly focused toward aiding the end-group determination of these materials by significantly speeding up the interpretation process. This allows information on the initiator and/or chain transfer agents, used to generate the polymer, and the mechanism of termination to be inferred from the data much more rapidly. The software allows the validity of hypothesized structures to be rapidly tested by automatically annotating the data file using previously proposed fragmentation rules for synthetic polymers. Low-energy collision-induced dissociation (CID) data from methacrylate, styrene, and polyether oligomers are used as example data for the software. Exact-mass CID information was used to aid the understanding of the dissociation mechanism of the polymers. The software can use exact-mass data to provide more confidence in the results. The MS/MS results indicate that the fragmentation pathways are those previously proposed for these polymers.

Polarity switching accurate mass measurement of pharmaceutical samples using desorption electrospray ionization and a dual ion source interfaced to an orthogonal acceleration time-of-flight mass spectrometer

A novel approach for the rapid, accurate mass analysis of pharmaceutical solid, liquid, and cream formulations using desorption electrospray ionization (DESI) is described. The method is based on polarity switching and real-time accurate mass measurement in an orthogonal acceleration time-of-flight mass spectrometer fitted with a dual-inlet electrospray ion source. Infusion of a reference compound into one inlet provides a single-point "lock mass" for accurate mass measurement. The other inlet sprays solvent at the sample being investigated using DESI. Minimal sample preparation was required. Results demonstrate the ability to acquire simultaneously positive and negative accurate mass DESI data within the same acquisition, thus negating the need for repeat analysis in each ion mode. In this paper, drugs that preferentially ionize in a particular mode depending on their physiochemical properties are presented. Mass accuracy to within 2 mTh was obtained for all drugs sampled.

Does cigarette smoking increase plasma urotensin II concentrations?

OBJECTIVE

Human urotensin II (UII) acts on the urotensin (UT) receptor and is the most potent mammalian vasoconstrictor identified to date. The role of UII in human cardiovascular regulation remains unclear, and the results of plasma measurements have been conflicting, perhaps because different measurement techniques have been used. The effects of cigarette smoking on plasma UII concentrations are unknown. The primary aim of our study was to demonstrate whether cigarette smoking had any effect on plasma UII concentrations in otherwise healthy volunteers. Our secondary aim was to compare the results obtained from assaying simultaneously using both radioimmunoassay (RIA) and immunoluminometric assay (ILMA).

METHODS

Blood was taken from 20 healthy male non-smokers and 20 healthy male cigarette smokers. Plasma was separated and stored at -70 degrees C. Samples were batch analysed simultaneously for UII using RIA and ILMA.

RESULTS

Median (range) plasma UII concentrations were lower in non-smokers [1.67 (1.0-2.27) pg ml(-1)] compared to smokers [2.62 (1.87-3.46) pg ml(-1)] (P = 0.03) measured using RIA. Those who had smoked a cigarette in the 10 min before sampling had greater concentrations of UII [3.10 (1.87-4.60) pg ml(-1)] compared to controls (P = 0.01). Plasma UII concentrations determined by ILMA were consistently low with no differences between groups.

CONCLUSION

The data obtained by RIA show that smoking may increase plasma concentrations of UII with a more pronounced increase when a cigarette has been smoked recently. There was a complete lack of correlation between RIA and ILMA for the whole data set, which suggests that some of the variability in plasma UII reported in the literature may result from differences between assays.

The rapid characterisation of poly(ethylene glycol) oligomers using desorption electrospray ionisation tandem mass spectrometry combined with novel product ion peak assignment software

A rapid method for the characterisation of polyglycol esters and ethers is described which uses accurate mass desorption electrospray ionisation (DESI) quadrupole time-of-flight mass spectrometry (Q-ToFMS). The results are combined with newly developed software which aids the interpretation of product ions produced using collision-induced dissociation (CID) of selected precursor ions. The poly(ethylene glycol) (PEG) samples analysed were PEG dibenzoate, PEG monooleate, PEG butyl ether, PEG bis(2-ethyl hexanoate) and PEG diacrylate. Lithium metal was used for cationisation of the PEG oligomers since it yielded the most useful structural information compared with other group I metals. The full scan mass spectra and product ion mass spectra were all obtained in <5 s. Interpretation of the MS/MS product ion spectra, using the product ion interpretation software which incorporates previously developed fragmentation rules, was carried out in <1 s.

Collision-induced fragmentation pathways including odd-electron ion formation from desorption electrospray ionisation generated protonated and deprotonated drugs derived from tandem accurate mass spectrometry

The rapid desorption electrospray ionisation (DESI) of some small molecules and their fragmentation using a triple-quadrupole and a hybrid quadrupole time-of-flight mass spectrometer (Q-ToF) have been investigated. Various scanning modes have been employed using the triple-quadrupole instrument to elucidate fragmentation pathways for the product ions observed in the collision-induced dissociation (CID) spectra. Together with accurate mass tandem mass spectrometry (MS/MS) measurements performed on the hybrid Q-ToF mass spectrometer, unequivocal product ion identification and fragmentation pathways were determined for deprotonated metoclopramide and protonated aspirin, caffeine and nicotine. Ion structures and fragmentation pathway mechanisms have been proposed and compared with previously published data. The necessity for elevated resolution for the differentiation of isobaric ions are discussed.

Influence of the parathyroid glands on bone metabolism

Bone is a classic target tissue for parathyroid hormone (PTH), whose calciotropic effect is mediated largely via catabolic actions on this tissue. Paradoxically, PTH also exerts anabolic actions, with intermittent injections of PTH or its amino-terminal fragments causing an increase in bone formation and bone mass, actions that form the basis for the use of PTH in the treatment of osteoporosis. Besides vitamin D, PTH is the only other known bone anabolic agent. High-affinity PTH receptors (PTH-1R) have been detected on osteoblasts and osteoclasts (albeit in lower numbers). Bone turnover, which includes activation of osteoclasts and osteoblasts, appears to be best reflected not by absolute concentrations of PTH (which can vary based on the assay and antibody used) but by a balance of circulating full-length PTH-(1-84) and amino-terminally truncated C-PTH fragments. When PTH-(1-84) is predominant, bone turnover is promoted. Among PTH fragments, PTH-(7-84) appears to be the most potent antagonist of PTH-(1-84). The mechanisms involved in these effects are unclear although mediation via unique C-terminal receptors has been suggested. We propose that, within the range of total PTH (100-1000 pg mL(-1)), the ratio of PTH-(1-84)/C-PTH fragment is a valuable tool for diagnosis of bone turnover. Data indicate that at PTH levels < 100-150 pg mL(-1) and > 1000 pg mL(-1), the ratio looses its predictive power. Assay type, patient characteristics (race, underlying renal disease) and treatment attributes (vitamin D, corticosteroids, phosphate binders) have an impact on the PTH ratio, and care should be used in interpreting assay results and making subsequent treatment decisions.

Gas phase characterization of the noncovalent quaternary structure of cholera toxin and the cholera toxin B subunit pentamer

Cholera toxin (CTx) is an AB5 cytotonic protein that has medical relevance in cholera and as a novel mucosal adjuvant. Here, we report an analysis of the noncovalent homopentameric complex of CTx B chain (CTx B5) using electrospray ionization triple quadrupole mass spectrometry and tandem mass spectrometry and the analysis of the noncovalent hexameric holotoxin usingelectrospray ionization time-of-flight mass spectrometry over a range of pH values that correlate with those encountered by this toxin after cellular uptake. We show that noncovalent interactions within the toxin assemblies were maintained under both acidic and neutral conditions in the gas phase. However, unlike the related Escherichia coli Shiga-like toxin B5 pentamer (SLTx B), the CTx B5 pentamer was stable at low pH, indicating that additional interactions must be present within the latter. Structural comparison of the CTx B monomer interface reveals an additional alpha-helix that is absent in the SLTx B monomer. In silico energy calculations support interactions between this helix and the adjacent monomer. These data provide insight into the apparent stabilization of CTx B relative to SLTx B.

The retinoblastoma protein is required for Ras-induced oncogenic transformation

Most human cancers involve either mutational activation of the Ras oncogenic pathway and/or inactivation of the retinoblastoma tumor suppressor (RB) pathway. Paradoxically, tumors that harbor Ras mutations almost invariably retain expression of a wild-type pRB protein. We explain this phenomenon by demonstrating that Ras-induced oncogenic transformation surprisingly depends on functional pRB protein. Cells lacking pRB are less susceptible to the oncogenic actions of H-RasV12 than wild-type cells and activated Ras has an inhibitory effect on the proliferation of pRB-deficient human tumor cells. In addition, depletion of pRB from Ras-transformed murine cells or human tumor cells that harbor Ras pathway mutations inhibits their proliferation and anchorage-independent growth. In sharp contrast to pRB-/- 3T3 cells, fibroblasts deficient in other pRB family members (p107 and p130) are more susceptible to Ras-mediated transformation than wild-type 3T3 cells. Moreover, loss of pRB in tumor cells harboring a Ras mutation results in increased expression of p107, and overexpression of p107 but not pRB strongly inhibits proliferation of these tumor cells. Together, these findings suggest that pRB and p107 have distinct roles in Ras-mediated transformation and suggest a novel tumor-suppressive role for p107 in the context of activated Ras.

Desorption electrospray ionisation mass spectrometry and tandem mass spectrometry of low molecular weight synthetic polymers

A range of low molecular weight synthetic polymers has been characterised by means of desorption electrospray ionisation (DESI) combined with both mass spectrometry (MS) and tandem mass spectrometry (MS/MS). Accurate mass experiments were used to aid the structural determination of some of the oligomeric materials. The polymers analysed were poly(ethylene glycol) (PEG), polypropylene glycol (PPG), poly(methyl methacrylate) (PMMA) and poly(alpha-methyl styrene). An application of the technique for characterisation of a polymer used as part of an active ingredient in a pharmaceutical tablet is described. The mass spectra and tandem mass spectra of all of the polymers were obtained in seconds, indicating the sensitivity of the technique.