Signal Corresponding (signal + corresponding)

Distribution by Scientific Domains

Selected Abstracts

Using Capsaicin Modified Multiwalled Carbon Nanotube Based Electrodes and p -Chloranil Modified Carbon Paste Electrodes for the Determination of Amines: Application to Benzocaine and Lidocaine

Abstract The utilization of the capsaicin modified carbon nanotube modified basal-plane pyrolytic graphite electrode or p -chloranil modified carbon paste electrodes are presented for the determination of pharmaceutical compounds containing amine functionality, such as benzocaine and lidocaine. In detection of benzocaine at a capsaicin modified electrode, the guaiacol functional group is irreversibly electrochemically oxidized to form the o -quinone derivative which then undergoes nucleophilic attack by the aromatic amine group in benzocaine via a 1,4-Michael addition mechanism forming a catechol-amine adduct. The electrochemically initiated formation of the capsaicin-benzocaine adduct causes a linear decrease in the voltammetric signal corresponding to capsaicin which correlates to the added concentration of benzocaine. [source]

Effective detection of peptides containing cysteine sulfonic acid using matrix-assisted laser desorption/ionization and laser desorption/ionization on porous silicon mass spectrometry

Tomoya Kinumi
Abstract Cysteine sulfonic acid-containing peptides, being typical acidic peptides, exhibit low response in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. In this study, matrix conditions and the effect of diammonium hydrogencitrate (DAHC) as additive were investigated for ionization of cysteine sulfonic acid-containing peptides in MALDI. A matrix-free ionization method, desorption/ionization on porous silicon (DIOS), was also utilized to evaluate the effect of DAHC. When equimolar three-component mixtures of peptides carrying free cysteine, cysteine sulfonic acid, and carbamidomethyl cysteine were measured by MALDI using a common matrix, ,-cyano-4-hydroxycinnamic acid (CHCA), no signal corresponding to cysteine sulfonic acid-containing peptide could be observed in the mass spectrum. However, by addition of DAHC to CHCA, the peaks of cysteine sulfonic acid-containing peptides were successfully observed, as well as when using 2,4,6-trihydroxyacetophenone (THAP) and 2,6-dihydroxyacetophenone with DAHC. In the DIOS mass spectra of these analytes, the use of DAHC also enhanced the peak intensity of the cysteine sulfonic acid-containing peptides. On the basis of studies with these model peptides, tryptic digests of oxidized peroxiredoxin 6 were examined as a complex peptide mixture by MALDI and DIOS. In MALDI, the peaks of cysteine sulfonic acid-containing peptides were observed when using THAP/DAHC as the matrix, but this was not so with CHCA. In DIOS, the signal from cysteine sulfonic acid-containing peptides was suppressed; however, the use of DAHC significantly enhanced the signal intensity with an increase in the number of observed peptides and increased signal-to-noise ratio in the DIOS spectra. The results show that DAHC in the matrix or on the DIOS chip decreases discrimination and suppression effects in addition to suppressing alkali-adduct ions, which leads to a beneficial effect on protonation of peptides containing cysteine sulfonic acid. Copyright 2005 John Wiley & Sons, Ltd. [source]

Optimized detection of lactate at high fields using inner volume saturation

Richard A.E. Edden
Abstract In localized proton MR spectroscopy (1H-MRS) in vivo, the detection of lactate (Lac) is affected by modulation of its resonances due to homonuclear scalar couplings (J). A simple and convenient way to distinguish Lac from lipids is to set the TE to 1/J so that the Lac signal is inverted while other resonances (such as lipid) remain in-phase. However, at high field strengths, such as 3 Tesla or above, the modulation of the Lac signal is complicated by chemical shift effects that cause modulation patterns to vary within different subregions of the localized volume. Under some conditions the Lac signal may even disappear completely. In this note we introduce the concept of inner volume saturation (IVS), which makes use of high bandwidth spatial pulses to remove the signal corresponding to the regions of the localized volume that contribute unwanted modulation patterns. The method is described theoretically and demonstrated experimentally at 3 Tesla in a phantom and a patient with acute stroke. The phantom measurements indicate that virtually 100% of the Lac signal can be recovered using this method. The method should be feasible at magnetic fields above 3 Tesla, and may also be applied to other coupled spin systems in which modulation effects are important. Magn Reson Med, 2006. 2006 Wiley-Liss, Inc. [source]

A Stacking Interaction between a Bridging Hydrogen Atom and Aromatic , Density in the n -B18H22,Benzene System

Ewan J. M. Hamilton Prof.
Abstract The structures of n -B18H22 and of n -B18H22,C6H6 were determined by single-crystal X-ray analysis at ,60,C. The geometry of the boron cluster itself does not seem to be appreciably affected by solvation. There does, however, appear to be an unusual interaction of a polyborane bridging hydrogen atom with the benzene , system, giving rise to an extended stacked structure. The 1H{11B} spectrum of n -B18H22 in [D6]benzene differs from that in [D12]cyclohexane most noticeably in the bridging proton region. Upon moving from the aliphatic to the aromatic solvent, the greatest increase in shielding was for the signal corresponding to the bridge hydrogen atom that interacts with the , system of benzene; the signal was shifted upfield by 0.49 ppm. Density functional theory calculations were performed on 1:1 and 2:1 complexes of the n -B18H22 unit with benzene. [source]

Power Doppler assessment of overall disease activity in patients with rheumatoid arthritis

Adem Kiris MD
Abstract Purpose. To examine synovial vascularity and flow patterns in hand and wrist joints,metacarpophalangeal (MCP) joints and ulnar stiloid (USTL) regions,of patients with rheumatoid arthritis (RA) using power Doppler sonography (PDUS) and spectral Doppler analysis and to assess the accuracy of PDUS in detecting overall disease activity in RA patients. Methods Two hundred forty MCP joints and 48 USTL regions in 24 RA patients were examined. Patients were categorized into 2 groups,active and inactive,according to the American College of Rheumatology remission criteria. Resistance indexes (RIs) were measured. Results Flow signals were detected in 50 MCP joints (in 13 patients) and 24 USTL regions (in 16 patients) and spectral analysis was performed in 46 MCP joints (12 patients) and 23 USTL regions (16 patients). The sensitivity and specificity of PDUS in detecting disease activity in RA were 92% and 40%, respectively. There was a negative correlation between flow signal number and RI, with higher scores of flow signals corresponding to lower RIs. Conclusion PDUS appears to be a reliable method for assessing inflammatory activity in rheumatoid synovium. 2006 Wiley Periodicals, Inc. J Clin Ultrasound34:5,11, 2006 [source]