A kinetic treatment of stopped-flow time courses for multiple chemiluminescence of the KIO4-luminol-Mn2+ system.

Stopped-flow time courses for chemiluminescence (CL) of the KIO4-luminol-Mn(2+) system showed an instantaneous jump in initial signal followed by two distinct bands. A kinetic model of the form [formula in text] with ten adjustable parameters was proposed to account for CL intensity (I) versus time (t) profiles. The three terms in the model represent the three CL bands.

A stopped-flow study of the dual chemiluminescence for the luminol-KIO4-Mn(2+) system in strong alkaline solutions.

A novel phenomenon of dual chemiluminescence (CL) was observed for the KIO4-luminol-Mn(2+) system in strong alkaline solutions using the stopped-flow technique. Scavenging study of the reactive oxygen species (ROS) suggested that the two CL peaks originated from different CL pathways precipated by distinct ROS (O2(-) and •OH for the first peak, mainly 1O2 for the second peak). Generation of these ROS at different time intervals from the reactions involving IO4(-), O2, and Mn(2+) and their subsequent reactions with luminol induced the intense CL emission.

Determination of enantiomerization barrier of thioridazine by dynamic capillary electrophoresis using sulfated cyclodextrins as chiral selectors.

The enantiomerization of thioridazine (THD) using sulfated beta-CDs (S-beta-CDs) as chiral selectors in a citrate buffer at pH 3.0 was investigated by dynamic CE. The enantiomers of THD were well separated with dual CD systems consisting of S-beta-CD and a neutral CD.

Enhancement of chemiluminescence of the KIO4-luminol system by gallic acid, acetaldehyde and Mn2+: application for the determination of catecholamines.

Chemiluminescence (CL) from the oxidation of luminol with potassium periodate in strong alkaline solutions was greatly enhanced by the combined effect of gallic acid, acetaldehyde and Mn(2+). The CL spectra exhibited only one emission band at 425 nm, indicating 3-aminophthalate as the emitting species. Various scavengers for superoxide anion, hydroxyl radical and singlet oxygen quenched the CL emission very efficiently (74-100%), suggesting the possible involvement of these reactive oxygen species (ROS) in the CL reactions.

Stopped-flow study of the enhanced chemiluminescence for the oxidation of luminol with hydrogen peroxide catalyzed by microperoxidase 8.

The presence of carbonate or Tris causes a dramatic enhancement in the chemiluminescence (CL) for the oxidation of luminol with hydrogen peroxide catalyzed by microperoxidase 8 (MP8). A nearly constant enhancement in CL was observed over a wide range of H(2)O(2) and luminol concentrations. The enhancement in CL is strongly pH-dependent, varying from 1.

Chiral separation of hydroxyflavanones in cyclodextrin-modified capillary zone electrophoresis using sulfated cyclodextrins as chiral selectors.

Chiral separations of three hydroxyflavanone aglycones, including 2'-, 3'-, and 4'-hydroxyflavanone, in capillary zone electrophoresis (CZE) using randomly sulfate-substituted beta-cyclodextrin (S-beta-CD) or dual cyclodextrin (CD) systems consisting of S-beta-CD and a neutral CD at low pH were investigated. The results indicate that S-beta-CD is an excellent chiral selector for enantioseparation of 2'-hydroxyflavanone and is a good chiral selector for 3'-hydroxyflavanone. Depending on the concentration of S-beta-CD ranging from 2.

Rapid protein identification using a disposable on-line clean-up/concentrating device and electrospray ionization mass spectrometry.

A simple, low-cost, expedient method has been developed for identification of proteins isolated from two-dimensional (2D) gels. The method described uses a disposable on-line clean-up device, a syringe infusion pump and electrospray ionization mass spectrometry (ESI-MS). The on-line clean-up and concentrating device is a tapered capillary column filled with 1.

Enantioselectivity of basic analytes in CZE enantioseparation under reversed-polarity mode using sulfated beta-cyclodextrins as chiral selectors: An unusual temperature effect.

Temperature effects on the enantioselectivity of basic analytes in CZE enantioseparation were studied under reversed-polarity mode using randomly sulfate-substituted beta-CDs (MI-S-beta-CD) as chiral seletors. Two catecholamines (epinephrine and isoproterenol) and two structurally related compounds (octopamine and norephedrine) were selected as test compounds in an electrophoretic system at low pH. The mobility differences between the (+)-enantiomers and the (-)-enantiomers of the two catecholamines and dopamine at 40 degrees C are greater than those at 25 degrees C with MI-S-beta-CD, even at a concentration as low as 0.

Strategies for enantioseparations of catecholamines and structurally related compounds by capillary zone electrophoresis using sulfated beta-cyclodextrins as chiral selectors.

Strategies for simultaneous enantioseparations of three catecholamines (DL-norepinephrine, DL-epinephrine, and DL-isoproterenol) and three structurally related compounds (DL-octopamine, DL-synephrine, and DL-norephedrine) by CZE using sulfated beta-CDs as chiral selectors were investigated. Four different separation modes were attempted: (I) using randomly sulfate-substituted beta-CD (MI-S-beta-CD) at relatively low concentrations in a high-concentration phosphate buffer at low pH in the normal polarity mode, (II) using MI-S-beta-CD at high concentrations at low pH in the reversed polarity mode, (III) using MI-S-beta-CD at moderately high concentrations in a phosphate buffer at neutral pH in the normal polarity mode, and (IV) using the single isomer heptakis(2,3-dihydroxy-6-O-sulfo)-beta-CD (SI-S-beta-CD) at low to moderately high concentrations in a high-concentration BGE at low pH in the normal polarity mode. Among them, enantioseparation of these cationic solutes was best achieved under the conditions of mode (II).

Electrophoretic behavior and pKa determination of quinolones with a piperazinyl substituent by capillary zone electrophoresis.

Electrophoretic behavior and pKa determination of six quinolones with a piperazinyl substituent, together with two quinolones without a piperazinyl substituent and 1-phenylpiperazine, were investigated by capillary zone electrophoresis. The results indicate that quinolones with a piperazinyl substituent involve three protonation/deprotonation equilibria. The results also suggest that the contribution of the zwitterionic species of these quinolones to the effective mobility may not be neglected.

Influence of pH on electrophoretic behavior of phenothiazines and determination of pKa values by capillary zone electrophoresis.

The influence of buffer pH on the electrophoretic behavior of 13 structurally related phenothiazines and determination of pK(a) values by capillary zone electrophoresis (CZE) were investigated. The results indicate that phenothiazines with a piperazine substituent behave quite differently from those with substituents having an aliphatic side chain or a piperidine moiety over the pH range studied. To separate these phenothiazines, it is preferable to select buffer pH in the range of 2.

Structurally homologous all beta-barrel proteins adopt different mechanisms of folding.

Acidic fibroblast growth factors from human (hFGF-1) and newt (nFGF-1) (Notopthalamus viridescens) are 16-kDa, all beta-sheet proteins with nearly identical three-dimensional structures. Guanidine hydrochloride (GdnHCl)-induced unfolding of hFGF-1 and nFGF-1 monitored by fluorescence and far-UV circular dichroism (CD) shows that the FGF-1 isoforms differ significantly in their thermodynamic stabilities. GdnHCl-induced unfolding of nFGF-1 follows a two-state (Native state to Denatured state(s)) mechanism without detectable intermediate(s).

Separation and migration behavior of structurally related phenothiazines in cyclodextrin-modified capillary zone electrophoresis.

The influences of buffer pH and the concentration of beta-cyclodextrins (beta-CDs) on the separation and migration behavior of 13 structurally related phenothiazines in CD-modified capillary zone electrophoresis (CD-CZE) using a phosphate background electrolyte at low pH were investigated. We focused on the separation of these phenothiazines, including the enantiomers of chiral analytes, with the use of beta-CD and hydroxypropyl-beta-CD (HP-beta-CD) as electrolyte modifiers or chiral selectors at concentrations less than 8 mM. The results indicate that the interactions of phenothiazines with beta-CDs are very strong and that effective separations of 13 analytes can be achieved with addition of 0.

Enhanced chemiluminescence for the oxidation of luminol with m-chloroperoxybenzoic acid catalyzed by microperoxidase 8.

The use of m-chloroperoxybenzoic acid (mCPBA) in stead of hydrogen peroxide causes an increase in chemiluminescence (CL) of luminol oxidation catalyzed by microperoxidase 8 (MP8) by an order of magnitude. The accelerated formation of an intermediate plays a major role in the CL enhancement, which also leads to a significant reduction in CL duration. The presence of guanidine hydrochloride, sodium carbonate, or sodium chloride further increases the CL emission drastically.

Stopped-flow kinetic study of the peroxidase reactions of mangano-microperoxidase-8.

We have investigated the kinetics for the peroxidase-type reaction of mangano microperoxidase 8 (Mn(III)-MP8) by the time-resolved and single-wavelength stopped-flow technique. The formation of intermediate and its subsequent reaction with substrates were studied separately. Oxidation of Mn(III)-MP8 by H2O2 at pH 10.