A comparative study of UniSpray and electrospray sources for the ionization of neuropeptides in liquid chromatography tandem mass spectrometry.

Despite the extensive use of electrospray ionization (ESI) for the quantification of neuropeptides by liquid chromatography-tandem mass spectrometry (LC-MS/MS), poor ionization and transmission efficiency are described for this ionization interface. A new atmospheric pressure ionization source, named UniSpray, was recently developed and commercialized. In this study, the LC-MS performance of this new ionization interface is evaluated and compared with ESI for the quantification of seven neuropeptides.

Assessing mixtures of supercharging agents to increase the abundance of a specific charge state of Neuromedin U.

With increasing evidence of the important role of peptides in pathophysiological processes, a trend towards the development of highly sensitive bioanalytical methods is ongoing. Inherent to the electrospray ionization process of peptides and proteins is the production of multiple charge states which may hamper proper and sensitive method development. Supercharging agents allow modifying the maximal charge state and the corresponding distribution of charges, thereby potentially increasing the number of ions reaching the detector in selected reaction monitoring mode.

Biodegradable Amphipathic Peptide Hydrogels as Extended-Release System for Opioid Peptides.

Chronic pain is currently treated with opioids that offer unsatisfactory long-term analgesia and produce serious side effects. There is a clear need for alternative therapies. Herein, peptide-based hydrogels are used as extended-release drug delivery carriers.

Synthesis and Evaluation of Stabilized and Selective Neuromedin U-1 Receptor Agonists.

Neuromedin U (NMU) is a multifunctional neuropeptide which is characterized by a high conservation through all species. Herein, we describe the synthesis of a novel set of NMU-analogs based on the truncated NMU-8. Through combination of previously reported modifications, an elaborate structure-activity relationship study was performed aiming for the development of peptides with an increased selectivity toward NMU receptor 1 (NMUR1).

Development of potent and proteolytically stable human neuromedin U receptor agonists.

Neuromedin U (NMU) is a highly conserved endogenous peptide that is involved in a wide range of physiological processes such as regulation of feeding behavior, the stress response and nociception. The major limitation to use NMU as a therapeutic is its short half-life. Here, we describe the development of a set of novel NMU-analogs based on NMU-8, by introducing unnatural amino acids into the native sequence.

LC-method development for the quantification of neuromedin-like peptides. Emphasis on column choice and mobile phase composition.

In this study, the separation of four neuromedin-like peptides is investigated on four different core-shell stationary phases. Moreover, the effect of the mobile phase composition, i.e.

Challenges for the in vivo quantification of brain neuropeptides using microdialysis sampling and LC-MS.

In recent years, neuropeptides and their receptors have received an increased interest in neuropharmacological research. Although these molecules are considered relatively small compared with proteins, their in vivo quantification using microdialysis is more challenging than for small molecules. Low microdialysis recoveries, aspecific adsorption and the presence of various multiply charged precursor ions during ESI-MS/MS detection hampers the in vivo quantification of these low abundant biomolecules.

An improved microbore UHPLC method with electrochemical detection for the simultaneous determination of low monoamine levels in in vivo brain microdialysis samples.

The simultaneous determination of the monoamines dopamine (DA), noradrenaline (NA) and serotonin (5-HT) in in vivo microdialysis samples remains challenging because of the low extracellular neurotransmitter levels in different brain regions, specific sample characteristics, and the quest for high temporal resolution and a multi-target strategy in neuropharmacological research. A fast and sensitive microbore (1.0mm i.

Mixed α/β-Peptides as a Class of Short Amphipathic Peptide Hydrogelators with Enhanced Proteolytic Stability.

Peptide hydrogels are a highly promising class of materials for biomedical application, albeit facing many challenges with regard to stability and tunability. Here, we report a new class of amphipathic peptide hydrogelators, namely mixed α/β-peptide hydrogelators. These mixed α/β-gelators possess good rheological properties (high storage moduli) and form transparent self-supporting gels with shear-thinning behavior.

Miniaturized ultra-high performance liquid chromatography coupled to electrochemical detection: Investigation of system performance for neurochemical analysis.

The interest in implementation of miniaturized ultra-high performance liquid chromatography (UHPLC) in neurochemical research is growing because of the need for faster, more selective and more sensitive neurotransmitter analyses. The instrument performance of a tailor designed microbore UHPLC system coupled to electrochemical detection (ECD) is investigated, focusing on the quantitative monoamine determination in in vivo microdialysis samples. The use of a microbore column (1.

An ultrasensitive nano UHPLC-ESI-MS/MS method for the quantification of three neuromedin-like peptides in microdialysates.

Aim: An ultrasensitive nano UHPLC-ESI-MS/MS method is developed to simultaneously monitor three low-concentration neuromedin-like peptides in microdialysates.

Results: Peptide preconcentration and sample desalting is performed online on a trap column. A shallow gradient slope at 300 nl/min on the analytical column maintained at 35°C, followed by two saw-tooth column wash cycles, results in the highest sensitivity and the lowest carryover.

Improved sensitivity of the nano ultra-high performance liquid chromatography-tandem mass spectrometric analysis of low-concentrated neuropeptides by reducing aspecific adsorption and optimizing the injection solvent.

Obtaining maximal sensitivity of nano UHPLC-MS/MS methods is primordial to quantify picomolar concentrations of neuropeptides in microdialysis samples. Since aspecific adsorption of peptides to Eppendorf tubes, pipette tips and UHPLC vials is detrimental for method sensitivity, a strategy is presented to reduce adsorption of these peptides during standard preparation. Within this respect, all procedural steps from dissolution of the lyophilized powder until the injection of the sample onto the system are investigated.