Identification of Dimethyldioctadecylammonium Ion (m/z 550.6) and Related Species (m/z 522.6, 494.6) as a Source of Contamination in Mass Spectrometry

Chemical contamination can be one of the more common problems encountered when performing trace-level analysis regardless of the analytical technique. Minimizing or eliminating background interferences can be a difficult task, so knowledge of the chemical composition of these contaminants can prove invaluable when it comes to identifying the source. Once the source is identified, proper steps may be taken to reduce or eliminate it. In this study, we report the identity of some commonly seen contaminants (m/z 550.6, 522.6, and 494.6) in electrospray ionization (ESI) mass spectrometry (MS). Through MS, tandem MS, accurate-mass, and high-resolution measurements we have identified these background contaminants as being quaternary ammonium species that contain long-chain hydrocarbon groups, where m/z 550.6 is a dimethyldioctadecylammonium ion (C18, C18) and m/z 522.6 and 494.6 are similar in nature but have shorter alkyl-chain groups. The lipophilic nature of these compounds and the fact that they have molecular weights similar to lysophospholipids make them a frequent contaminant in lipidomic studies. The likely sources of these compounds are commonly used personal and household products

Dynamic Range Expansion by Gas-Phase Ion Fractionation and Enrichment for Imaging Mass Spectrometry

In the analysis of biological tissue by imaging mass spectrometry (IMS), the limit of detection and dynamic range are of paramount importance in obtaining experimental results that provide insight into underlying biological processes. Many important biomolecules are present in the tissue milieu in low concentrations and in complex mixtures with other compounds of widely ranging abundances, challenging the limits of analytical technologies. In many IMS experiments, the ion signal can be dominated by a few highly abundant ion species. On trap-based instrument platforms that accumulate ions prior to mass analysis, these high abundance ions can diminish the detection and dynamic range of lower abundance ions. Herein, we characterize two strategies for combating these challenges during IMS experiments on a hybrid QqFT-ICR MS. In one iteration, the mass resolving capabilities of a quadrupole mass filter are used to selectively enrich for ions of interest via a technique previously termed continuous accumulation of selected ions (CASI). Secondly, we have introduced a supplemental dipolar AC waveform to the quadrupole mass filter of a commercial QqFT-ICR mass spectrometer to perform selected ion ejection prior to the ion accumulation region. This setup allows the selective ejection of the most abundant ion species prior to ion accumulation, thereby greatly improving the molecular depth with which IMS can probe tissue samples.<br /

Three-Dimensional Visualization of Protein Expression in Mouse Brain Structures Using Imaging Mass Spectrometry

We have developed a method to visualize matrix-assisted laser desorption ionization imaging mass spectrometry (MALDI IMS) data aligned with optically determinable tissue structures in three dimensions. Details of the methodology are exemplified using the 3-D reconstruction of myelin basic protein (MBP) in the corpus callosum of a mouse brain. In this procedure, optical images obtained from serial coronal sections are first aligned to each other to reconstruct a surface of the corpus callosum from segmented contours of the aligned images. The MALDI IMS data are then coregistered to the optical images and superimposed into the surface to create the final 3-D visualization. Correlating proteomic data with anatomical structures provides a more comprehensive understanding of healthy and pathological brain functions, and holds promise to be utilized in more complex anatomical arrangements. (J Am Soc Mass Spectrom 2005, 16, 1093–1099) © 2005 American Society for Mass Spectrometry With the introduction of computer tomography (CT, positron emission tomography (PET) and magnetic resonance imaging (MRI, 3-D medical imaging has become important in studyin

Adjuvants in clinical regional anesthesia practice: A comprehensive review

Adjuvants are medications that work synergistically with local anesthetics to help enhance the duration and quality of analgesia in regional techniques. Regional anesthesia has become more prevalent as evidence continues to show efficacy, enhancement of patient care, increased patient satisfaction, and improved patient safety. Practitioners in the perioperative setting need to not only be familiar with regional techniques but also the medications used for them. Some examples of adjuvant medications for regional techniques include dexamethasone, alpha 2 agonists such as clonidine and dexmedetomidine, midazolam, buprenorphine, NMDA antagonists, including ketamine and magnesium, neostigmine, sodium bicarbonate, epinephrine, and non-steroidal anti-inflammatory drugs. The aim of the present investigation, therefore, is to provide a comprehensive review of the most commonly used non-opioid adjuvants in clinical practice today. Regional adjuvants can improve patient safety, increase patient satisfaction, and enhance clinical efficacy. Future studies and best practice techniques can facilitate standardization of regional anesthesia adjuvant dosing when providing nerve blocks in clinical practice

Cued speech for enhancing speech perception and first language development of children with cochlear implants

Nearly 300 million people worldwide have moderate to profound hearing loss. Hearing impairment, if not adequately managed, has strong socioeconomic and affective impact on individuals. Cochlear implants have become the most effective vehicle for helping profoundly deaf children and adults to understand spoken language, to be sensitive to environmental sounds, and, to some extent, to listen to music. The auditory information delivered by the cochlear implant remains non-optimal for speech perception because it delivers a spectrally degraded signal and lacks some of the fine temporal acoustic structure. In this article, we discuss research revealing the multimodal nature of speech perception in normally-hearing individuals, with important inter-subject variability in the weighting of auditory or visual information. We also discuss how audio-visual training, via Cued Speech, can improve speech perception in cochlear implantees, particularly in noisy contexts. Cued Speech is a system that makes use of visual information from speechreading combined with hand shapes positioned in different places around the face in order to deliver completely unambiguous information about the syllables and the phonemes of spoken language. We support our view that exposure to Cued Speech before or after the implantation could be important in the aural rehabilitation process of cochlear implantees. We describe five lines of research that are converging to support the view that Cued Speech can enhance speech perception in individuals with cochlear implants.SCOPUS: ar.jinfo:eu-repo/semantics/publishe