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Jeffrey N Stuart

Publications and source records attributed to Jeffrey N Stuart.

10 recordsLinked to original sources
PubMed2006

Capillary electrophoresis of ultrasmall carboxylate functionalized silicon nanoparticles.

Capillary electrophoresis is used to separate ultrasmall ( approximately 1 nm) carboxylate functionalized Si nanoparticles (Si-np-COO(-)) prepared via hydrosilylation with an omega-ester 1-alkene. The electropherograms show a monodisperse Si core size with one or two carboxylate groups added to the surface. On-column detection of their laser-induced fluorescence demonstrates that the individual Si-np-COO(-) have narrow emissions (full width at half maximum = 30-40 nm) with a nearly symmetric lineshape. Preparative scale electrophoresis should be a viable route for purification of the Si-np-COO(-) for further study and future applications.

Alkenes↗
PubMed2006

Serotonin catabolism and the formation and fate of 5-hydroxyindole thiazolidine carboxylic acid.

Serotonin (5-HT) functions as a neurotransmitter and neuromodulator in both the central and enteric nervous systems of mammals. The dynamic degradation of 5-HT metabolites in 5-HT-containing nervous system tissues is monitored by capillary electrophoresis with wavelength-resolved laser-induced native fluorescence detection in an effort to investigate known and novel 5-HT catabolic pathways. Tissue samples from wild type mice, genetically altered mice, Long Evans rats, and cultured differentiated rat pheochromocytoma PC-12 cells, are analyzed before and after incubation with excess 5-HT. From these experiments, several new compounds are detected. One metabolite, identified as 5-hydroxyindole thiazoladine carboxylic acid (5-HITCA), has been selected for further study. In 5-HT-incubated central and enteric nervous system tissue samples and differentiated PC-12 cells, 5-HITCA forms at levels equivalent to 5-hydroxyindole acetic acid, via a condensation reaction between L-cysteine and 5-hydroxyindole acetaldehyde. In the enteric nervous system, 5-HITCA is detected without the addition of 5-HT. The levels of L-cysteine and homocysteine in rat brain mitochondria are measured between 80 and 140 microm and 1.9 and 3.4 microm, respectively, demonstrating that 5-HITCA can be formed using available, free L-cysteine in these tissues. The lack of significant accumulation of 5-HITCA in the central and enteric nervous systems, along with data showing the degradation of 5-HITCA into 5-hydroxyindole acetaldehyde, suggests that an equilibrium coupled to the enzyme, aldehyde dehydrogenase type 2, prevents the accumulation of 5-HITCA. Even so, the formation of 5-HITCA represents a catabolic pathway of 5-HT that can affect the levels of 5-HT-derived compounds in the body.

Animals↗
PubMed2004

Spurious serotonin dimer formation using electrokinetic injection in capillary electrophoresis from small volume biological samples.

One normally assumes that the analytical measurement process does not introduce spurious compounds. Capillary electrophoresis is a separation method frequently used for small-volume biological measurements. We demonstrate the potential for creating new peaks in a capillary electropherogram when using electrokinetic injections and illustrate the potential deleterious effects with biological samples involving serotonin and nitric oxide measurements. Specifically, when measuring the serotonin content from individual neurons using electrokinetic injections from 360 nL stainless steel vials, we detect a new peak that we identify as a serotonin dimer. We do not observe this peak when using hydrodynamic injections.

Animals↗
PubMed2004

Characterization of the physicochemical parameters of dense core atrial gland and lucent red hemiduct vesicles in Aplysia californica.

Characterizing femtoliter-volume cellular organelles requires innovative analytical techniques such as mass spectrometry, separations, and NMR. The capabilities of all three are demonstrated for characterizing the physicochemical properties of the electron-dense core atrial gland vesicles from Aplysia californica and comparing them with the same properties of the electron lucent red hemiduct vesicles. Single-vesicle mass spectrometric measurements show that the atrial gland vesicles contain an abundance of peptides while the red hemiduct vesicles contain no detectable peptide signals. Capillary electrophoresis with wavelength-resolved native fluorescence detection is used to characterize larger vesicle samples for tyrosine- and tryptophan-containing peptides. Using NMR spectroscopy, we show that the physiologically active peptides located in the core of the atrial gland vesicles are NMR inactive when the vesicles are intact. Resonances from these peptides appear after vesicle lysis by heating, suggesting that initially they are packed in a crystalline or semicrystalline core so that the NMR resonances are not detectable. In contrast, the red hemiduct vesicles appear to have their contents stored in a completely mobile form due to the fact that no new NMR resonances are detected after heating.

Animals↗
PubMed2004

Systemic serotonin sulfate in opisthobranch mollusks.

Serotonin (5-hydroxytryptamine, 5-HT) is a ubiquitous modulatory neurotransmitter with roles as a neurohormone and neurotransmitter. However, few studies have been performed characterizing this molecule and its related metabolites in circulating fluids. Here, we demonstrate native 5-HT sulfate, but much lower levels of 5-HT, in hemolymph of the marine mollusk Pleurobranchaea californica. The metabolite 5-HT sulfate forms from 5-HT uptake and metabolism in central ganglia of Aplysia californica and in the visceral nerve and eye of Pleurobranchaea, but not in hemolymph itself. In addition, 5-hydroxyindole acetic acid (5-HIAA), while not detected in hemolymph, forms in higher quantities than does 5-HT sulfate in the eye and visceral nerve, and gamma-glu-5-HT is also observed in this area but never in hemolymph. As systemic 5-HT sulfate appears not to originate from the optic region or from systemic 5-HT, 5-HT sulfate likely derives from the nervous system. Circulating 5-HT sulfate is at least 10-fold higher during the light portion of a 12 : 12-h light/dark cycle than during the dark portion (p < 0.0007), but there is no obvious trend for free systemic tryptophan (Trp) (p > 0.3) in Pleurobranchaea. 5-HT in mollusks is associated with general arousal state; thus, diurnal systemic changes in a 5-HT catabolite may reflect a regulatory role for indole catabolism in behavioral rhythms.

5-Hydroxytryptophan↗
PubMed2003

Serotonin catabolism depends upon location of release: characterization of sulfated and gamma-glutamylated serotonin metabolites in Aplysia californica.

Serotonin is a vital neurotransmitter for the functioning of the nervous system in species throughout the animal phyla. Despite its ubiquitous nature, the metabolism of this molecule has yet to be completely elucidated in even the most basic of organisms. Two novel serotonin catabolites, serotonin-O-sulfate and gamma-glu-serotonin-O-sulfate, are chemically characterized using capillary electrophoresis with wavelength-resolved fluorescence detection and electrospray mass spectrometry, and the formation of gamma-glu-serotonin in Aplysia californica is confirmed. These novel compounds appear to be synthesized enzymatically, and known mammalian enzymes exist for all serotonin transformations observed here. The pathway of serotonin inactivation depends upon the type of neuronal tissue subjected to neurotransmitter incubation, with assorted serotonin products observed in distinct locations. Initially demonstrated to be in the metacerebral cell (MCC) soma, the new serotonin metabolite serotonin-O-sulfate may contribute to important functions in the serotonergic system beyond simple serotonin inactivation.

Animals↗
PubMed2002

Capillary electrophoresis with wavelength-resolved laser-induced fluorescence detection.

Capillary electrophoresis (CE) enables rapid separations with high separation efficiency and compatibility with small sample volumes. Laser-induced fluorescence detection can result in extremely low limits of detection in CE. Single-channel fluorescence detection, however, furnishes little qualitative information about a species being detected, except for its CE migration time. Use of multidimensional information often enables unambiguous identification of analytes. Combination of CE with information-rich wavelength-resolved fluorescence detection is analogous with ultraviolet-visible diode-array detection and furnishes both qualitative and quantitative chemical information about target species. This review discusses recent advances in wavelength-resolved laser-induced fluorescence detection coupled with CE, with an emphasis on instrument design.

Animals↗