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S Parus

Publications and source records attributed to S Parus.

9 recordsLinked to original sources
PubMed2001

Gel-free experiments of reaction-diffusion front kinetics.

We present a gel-free experimental system to study the kinetics of the reaction front in the A+B-->C reaction-diffusion system with initially-separated reactants. The experimental setup consists of a CCD camera monitoring the kinetics of the front formed in the reaction-diffusion process Cu(2+) + tetra [disodium ethyl bis(5-tetrazolylazo) acetate trihydrate] -->1:1 complex, in aqueous, gel-free solution, taking place inside a 150 microm gap between two flat microscope slides. The experimental results agree with the theoretical predictions for the time dependence of the front's width, height, and location, as well as the global reaction rate.

Journal Article↗
PubMed2000

Isoelectric focusing nonporous RP HPLC: a two-dimensional liquid-phase separation method for mapping of cellular proteins with identification using MALDI-TOF mass spectrometry.

A novel two-dimensional liquid-phase separation method was developed that is capable of resolving large numbers of cellular proteins. The proteins are separated by pI using isoelectric focusing in the first dimension and by hydrophobicity using nonporous reversed-phase HPLC in the second dimension (IEF-NP RP HPLC). Proteins were mapped using original software in order to create a protein pattern analogous to that of the 2-D PAGE image. RP HPLC peaks are represented by bands of different intensity in the 2-D image, according to the intensity of the peaks eluting from the HPLC. Each peak was collected as the eluent of the HPLC separation in the liquid phase. The proteins collected were identified using proteolytic enzymes, MALDI-TOF MS and MSFit database searching. Using IEF-NP RP HPLC, approximately 700 bands were resolved in a pI range from 3.2 to 9.5 and 38 different proteins with molecular weights ranging from 12,000 to 75,000 were identified. In comparison to a 2-D gel separation of the same human erythroleukemia cell line lysate, the IEF-NP RP HPLC produced improved resolution of low mass and basic proteins. In addition, the proteins remained in the liquid phase throughout the separation, thus making the entire procedure highly amenable to automation and high throughput. It is demonstrated that IEF-NP RP HPLC provides a viable alternative to the 2-D gel separation method for the screening of protein profiles.

Chromatography, High Pressure Liquid↗
PubMed2000

On-line capillary liquid chromatography tandem mass spectrometry on an ion trap/reflectron time-of-flight mass spectrometer using the sequence tag database search approach for peptide sequencing and protein identification.

Capillary high-performance liquid chromatography has been coupled on-line with an ion trap storage/reflectron time-of-flight mass spectrometer to perform tandem mass spectrometry for tryptic peptides. Selection and fragmentation of the precursor ions were performed in a three-dimensional ion trap, and the resulting fragment ions were pulsed out of the trap into a reflectron time-of-flight mass spectrometer for mass analysis. The stored waveform inverse Fourier transform waveform was applied to perform ion selection and an improved tickle voltage optimization scheme was used to generate collision-induced dissociation. Tandem mass spectra of various doubly charged tryptic peptides were investigated where a conspicuous y ion series over a certain mass range defined a partial amino acid sequence. The partial sequence was used to determine the identity of the peptide or even the protein by database search using the sequence tag approach. Several peptides from tryptic digests of horse heart myoglobin and bovine cytochrome c were selected for tandem mass spectrometry (MS/MS) where it was demonstrated that the proteins could be identified based on sequence tags derived from MS/MS spectra. This approach was also utilized to identify protein spots from a two-dimensional gel separation of a human esophageal adenocarcinoma cell line.

Amino Acid Sequence↗
PubMed1999

On-line capillary electrophoresis/microelectrospray ionization-tandem mass spectrometry using an ion trap storage/time-of-flight mass spectrometer with SWIFT technology.

The development of a system capable of the speed required for on-line capillary electrophoresis-tandem mass spectrometry (CE-MS/MS) of tryptic digests is described. The ion trap storage/reflectron time-of-flight (IT/reTOF) mass spectrometer is used as a nonscanning detector for rapid CE separation, where the peptides are ionized on-line using electrospray ionization (ESI). The ESI produced ions are stored in the ion trap and dc pulse injected into the reTOF-MS at a rate sufficient to maintain the separation achieved by CE. Using methodology generated by software and hardware developed in our lab, we can produce SWIFT (Stored Waveform Inverse Fourier Transform) ion isolation and TICKLE activation/fragmentation voltage waveforms to generate MS/MS at a rate as high as 10 Hz so that the MS/MS spectra can be optimized on even a 1-2 s eluting peak. In CE separations performed on tryptic digests of dogfish myelin basic protein (MBP) where eluting peaks 4-8 s wide are observed, it is demonstrated that an acquisition rate of 4 Hz provides > 20 spectra/peak and is more than sufficient to provide optimized MS/MS spectra of each of the eluting peaks in the electropherogram. The detailed structural analysis of dogfish MBP including several posttranslational modifications using CE-MS and CE-MS/MS is demonstrated using this method with < 10 fmol of material consumed.

Amino Acid Sequence↗
PubMed1998

Development of a three-dimensional topographic map display for capillary electrophoresis/mass spectrometry with an ion trap/reflectron time-of-flight mass spectrometer detector: applications to tryptic digests of isoforms of myelin basic protein.

A three-dimensional (3-D) contour map format has been developed to display the large amount of data continuously collected throughout an on-line capillary separation using an ion trap storage/reflectron time-of-flight detector (IT/reTOF). The resulting data are displayed on a single computer screen with a mass-to-charge ratio value-elution time-intensity representation. The intensity of various components is represented by 16 different colors so that the mass-to-charge ratio value, the elution time, and the intensity can be conveniently determined for each component. In addition, the mass spectrum and total ion chromatogram or total ion electropherogram (TIE) are shown on the same screen as the 3-D map that enables the correlation of a single spot in the 3-D map to the peaks in the TIE and the corresponding mass spectrum. The 3-D map has been used to identify various posttranslational modification sites of bovine myelin basic protein charge isomers, where the datafiles of tryptic digests of proteins analyzed by capillary electrophoresis/mass spectrometry were processed by this software and a comparison could be performed among the isoforms. The feature of in-screen integration over both the separation domain and the mass domain makes the acquisition of the selected ion chromatogram very convenient and greatly improves the ability to detect modified components present in low amounts.

Amino Acid Sequence↗
PubMed1997

High-performance fiber-optic pH microsensors for practical physiological measurements using a dual-emission sensitive dye.

A fast and durable ratiometric pH microoptode that is highly accurate, precise, sensitive, reversible, and reproducible over the physiological ranges of pH, ionic strength, and temperature has been developed. The sensing site consists of 5 (and 6)-carboxynaphthofluorescein (CNF) entrapped in a polyacrylamide gel matrix via photopolymerization at the silanized end of an optical fiber with a diameter of 2 (pulled) or 125 microns (unpulled). The optode's precision for the pH 6.3-8.4 range in rat embryos, sera, or physiological (Earle's and Tyrode's) buffers was found to be better than +/- 0.03 pH unit. The pulled and unpulled optodes have respective upper limit response times of 1 and 400 ms for 1-pH-unit change. Over a 7-week period, they retain sensitivity for 600 and 10,000 measurements, respectively. Ratiometric measurements are made using a pH-sensitive emission peak on each side of an isosbestic point. The CNF microoptode is most suitable for biological applications because of its essentially linear response over the pH 7-8 range, its high sensitivity (slope about 2), and its almost perfect correlation with a pH macroelectrode. Furthermore, errors introduced by photobleaching, leaching, quenching, optode movement, and excitation source fluctuations are minimal.

Animals↗
PubMed1997

Development of a capillary high-performance liquid chromatography tandem mass spectrometry system using SWIFT technology in an ion trap/reflectron time-of-flight mass spectrometer.

In this work a capillary high-performance liquid chromatography/tandem mass spectrometry system has been developed in a quadrupole ion trap/reflectron time-of-flight mass spectrometer. The broadband excitation for isolating a precursor ion is achieved by generating the stored waveform inverse Fourier transform waveform in real time. Following the isolation and cooling periods, an auxiliary AC voltage (tickle) is applied to the entrance end cap of the ion trap to generate collision induced dissociation. The amplitude of the tickle voltage is optimized on-line using a feedback method which involves having two computers communicating with each other. This system has been tested with a 4-peptide mixture and tandem mass spectra were obtained for each peptide.

Chromatography, High Pressure Liquid↗
PubMed1996

The development of a data system for a combination of liquid chromatography or capillary electrophoresis with an ion trap storage/reflectron time-of-flight mass detector.

A data system based upon a 200 MHz transient recorder interface card in a Pentium PC computer is demonstrated for on-line analysis of microbore high-performance liquid chromatography (HPLC), capillary HPLC and capillary electrophoresis (CE) separations using a fast and sensitive ion-trap storage/reflectron time-of-flight mass spectrometric detector (IT-reTOFMS). Under the control of a user-written program, the system is capable of conducting the data acquisition and storage for a minimum of 30 min, at rates exceeding 10 Hz, of individual mass spectra containing 16,000 data points having 10 nsec resolution. The capability is mainly attributed to the use of a data reduction scheme in which only mass intensities higher than a preset threshold are saved as indexed flight-time/intensity pairs. This produces a typical reduction ratio of 30:1 in data set size, yielding faster storage with smaller file size, and permits the complete set of mass spectra to be held in the computer's memory. In addition, the data system is capable of displaying, for real-time evaluation of the analysis, each individual mass spectrum and the total-ion chromatogram. Further, the selected-ion chromatograms of given masses and a 3-dimensional topographic map describing a separation process can be rapidly generated from the collected data for the unambiguous and high fidelity identification of target analytes in a complex mixture.

Amino Acid Sequence↗