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Analysis of transient and reversible effects of poly-L-arginine on the in vivo nasal absorption of FITC-dextran in rats.

We have investigated whether poly-L-arginine, with a mean molecular weights of 8.9 and 45.5 kDa (poly-L-Arg (10) and poly-L-Arg (50)), can induce transient and reversible effects involving enhancement of the nasal absorption of fluorescein isothiocyanate-labeled dextran (MW 4.4 kDa, FD-4) and determined the main pathway for the increased transport of FD-4 in rats in vivo. Pre-administration and repeated administration studies were conducted involving the selection of different time intervals between intranasal administration of poly-L-Arg and administration of FD-4, with and without poly-L-Arg, to characterize these transient and reversible effects. The degradation of poly-L-Args in a diluted nasal drip was determined from the fluorescence of degraded poly-L-Arg-fluorescamine products. In the pre-administration study, poly-L-Arg exhibited a transient effect on the increased nasal FD-4 absorption depending on its molecular weight, associated with the degradation rate of poly-L-Arg in mucus. In the repeated administration study, additional poly-L-Arg produced similarly enhanced FD-4 absorption. Confocal laser scanning microscopy showed that fluorescence of FD-4 after co-administration of poly-L-Arg (50) was confined mainly to the paracellular spaces. In conclusion, poly-L-Arg exhibited molecular weight-dependent transient and reversible effects on the enhancement of nasal FD-4 absorption paracellularly in rats in vivo. The enzymatic degradation of poly-L-Arg is one of the key determinants of the transient effect on in vivo enhanced absorption of FD-4.

Absorption↗

Cellular localization of polyamines: cytochemical and ultrastructural methods providing new clues to polyamine function in ram spermatozoa.

Polyamine binding sites have been localized in ram spermatozoa using biochemical and cytochemical tools. Incubating the cells with 14C-spermine and determining its distribution after sonication and differential centrifugation, revealed that 60% of the radioactive spermine was localized in the head, 21.5% in the tail and about 9% in the plasma membrane. A polyamine specific cytochemical staining by the formaldehyde-fluorescamine method, revealed that most of the polyamines were localized in the midpiece, where the cell mitochondria are located, and in the acrosome region. Two additional studies used electron microscopy, employing polycationic colloidal gold and spermine-ferritin as cytochemical markers. The most sensitive and specific method was the staining of the cells with ferritin-spermine whose synthesis is described in this study. The outer membrane was the preferential site for spermine binding which was densely distributed in a highly orderly pattern. There was a sparse distribution of spermine binding sites on the plasma membrane surrounding the acrosome and none on the post acrosomal region. The role of spermine in the acrosome reaction and Ca2+ fluxes in sperm cells is discussed.

Animals↗

High-performance liquid chromatographic methods for determination of gentamicin in biological fluids.

A selective and sensitive methods for the determination of gentamicin in plasma and urine by high-performance liquid chromatography has been developed. Following deproteinization, the gentamicin is reacted with fluorescamine to produce a fluorescent derivative. This reaction mixture is directly chromatographed on a cation exchange column using as mobile phase acetonitrile-phosphoric acid (7:3). The gentamicin compounds elute as a single peak. Using 0.1 ml of plasma, quantitation of gentamicin concentration as low as 1 mg/l are possible. Possible interference from other aminoglycosides and antibiotics is discussed.

Animals↗

Liquid chromatographic determination of mexiletine and tocainide in human plasma with fluorescence detection after reaction with a modified o-phthalaldehyde reagent.

A liquid chromatographic procedure for the determination of mexiletine or tocainide in human plasma is described. Plasma, after the addition of a homologue of mexiletine or of tocainide, is extracted with dichloromethane. The extract is evaporated and reconstituted in a non-aqueous o-phthalaldehyde--mercaptoethanol reagent. An aliquot of the solution is chromatographed on a reversed-phase Ultrasphere-octyl column. The peaks are detected by fluorescence (lambda ex = 350 nm and lambda em = 445 nm). The fluorescent derivatives of the drugs and internal standards are stable at room temperature and give symmetrical single peaks. Use of fluorescamine as a reagent to prepare fluorescent derivatives of mexiletine and tocainide prior to chromatography is also evaluated.

Chromatography, Liquid↗

Automated determination of amoxycillin in biological fluids by column switching in ion-pair reversed-phase liquid chromatographic systems with post-column derivatization.

Amoxycillin, a polar aminopenicillin, is rather unstable in biological fluids. Degradation can be prevented by fast sample pretreatment and storage at -70 degrees C or below. After pH adjustment, it is stable in biological fluids for over 16 h. The samples were handled by automated chromatography overnight. The chromatographic system consisted of a small guard column, two analytical columns separated by a switching valve, a post-column reactor and a fluorescence detector. The chromatographic events and the calculation of results were handled by a computing integrator. The chromatography was based on ion-pairing principles. An efficient clean-up of the biological fluids was obtained by a heart cut from the first column, where the neutral mobile phase contained hexyl sulphate. In the second column the organic anion was exchanged for a large quaternary ammonium compound; amoxycillin was then retained as an ion pair. The composition of the mobile phases had to be designed carefully in order to avoid a disturbance of the chromatographic performance on the last column. An adequate selectivity and sensitivity was obtained by a post-column derivatization with fluorescamine. Detection limits were 10 and 25 ng/ml for plasma and urine, respectively, and the inter-assay precisions at low levels (350 and 2000 ng/ml for plasma and urine, respectively) were ca. 5% (R.S.D.).

Amoxicillin↗

Highly sensitive method for the determination of 1-methyl-1,2,3,4-tetrahydro-beta-carboline using combined capillary gas chromatography and negative-ion chemical ionization mass spectrometry.

A sensitive method was developed for the determination of deuterated and non-deuterated 1-methyl-1,2,3,4-tetrahydro-beta-carboline by combined capillary gas chromatography and negative-ion chemical ionization mass spectrometry. 1-Methyl-1,2,3,4-tetrahydro-beta-carboline was converted into a trifluoroacetyl derivative after pretreatment with fluorescamine and extraction with ethyl acetate. The derivative was separated by capillary gas chromatography and determined by selected-ion monitoring. In the determination, [3,3,4,4-2H4]-1-methyl-1,2,3,4-tetrahydro-beta-carboline was used as an internal standard. The method developed in this work was used for the determination of deuterated and non-deuterated 1-methyl-1,2,3,4-tetrahydro-beta-carboline in human urine samples collected before and after administration of [3,3-2H2]-L-tryptophan.

Adult↗

RP-HPLC tryptic mapping of IgG1 proteins with post-column fluorescence derivatization.

Peptide mapping is an important analytical technique widely used to study the primary structure of proteins. In quality control settings, it is employed as an identity test to probe for small changes in protein primary structure. A great challenge in peptide mapping is to minimize the detection limit for peptides due to the low detectability of smaller peptides based on their ultraviolet absorbance. The detection of peptide fragments can be enhanced by pre-or post-column derivatization with fluorescent tags. The use of post-column o-pthalaldehyde (OPA) and fluorescamine chemistries for on-line derivatization of peptide fragments from the RP-HPLC tryptic maps of several IgG1 monoclonal antibodies was explored. This paper describes the simple and sensitive peptide mapping technique for structural confirmation of proteins using picomoles of samples by post-column fluorescence derivatization. A comparison of UV and fluorescence detection of a peptide map is also presented. The method includes post column OPA derivatization of tryptic peptides from RP-HPLC tryptic maps with fluorescence detection. The conclusion reached that fluorescence detection gave relative detectability for tryptic peptides that range from 10- to 100-fold better than those observed with UV detection. The sensitivity of the peptide map increased by about 200-500 fold, i.e. peptide maps could be obtained using 2-5 pmol of digest instead of 1 nmol of digest. A roughly equal fluorescence response for all peptides (equal peak areas) was generally observed.

Antibodies, Monoclonal↗

Trace detection of hydroxyl radicals during the redox cycling of low concentrations of diaziquone: a new approach.

Quantifying oxygen radicals that arise during the redox cycling of quinone-containing anticancer agents such as diaziquone (AZQ) has been difficult, as has been their detection at low drug concentrations. This is due to the fact that EPR spin trapping, the method most often used for *OH detection, requires the use of high drug concentrations. Using a new highly sensitive technique that employs a fluorescamine-derivatized nitroxide, we show that low levels of NADPH-cytochrome P450 reductase (4.25 microg/ml) catalyze the production of hydroxyl radicals at very low, clinically relevant AZQ concentrations. Thus, at this enzyme concentration, we were able to detect a rate of 0.10 nM s(-1) hydroxyl radical production by 5 microM AZQ, a clinically relevant concentration. The Michaelis-Menten constants for AZQ-mediated hydroxyl radical production are: K(M) = 10.7 +/- 1.4 microM, and V(max) = 5.2 +/- 0.9 x 10(-8) M s(-1) (mg protein)(-1). Experiments employing catalase, superoxide dismutase, and NADPH-cytochrome P450 reductase, confirm the previously deduced conclusions from high drug concentrations, that is, that at low concentrations, AZQ acts to shuttle reducing equivalents from the enzyme to oxygen, thus generating the redox cycle. The data presented here suggest that the levels and locations of redox active metal ions may be the principal controlling factor in the pathway of AZQ activity that involves oxidative stress.

Animals↗

Light induces peroxidation in retina by activating prostaglandin G/H synthase.

Prostaglandin G/H synthase (PGHS) has been shown to generate peroxides to a significant extent in the retina and absorbs light at the lower end of the visible spectrum. We postulated that PGHS could be an important initial source of peroxidation in the retina exposed to light, which would in turn alter retinal function. Exposure of pig eyes (in vivo) to light (350 fc/3770 lx) caused after 3 h a 50% increase and by 5 h a 30% decrease in a- and b-wave amplitudes of the electroretinogram (ERG) which were comparable at 380-650 nm and 380-440 nm but were not observed at wavelengths > 450 nm. These effects of light were prevented by free radical scavengers (dimethylthiourea and high-dose allopurinol) and PGHS inhibitors (naproxen and diclofenac), but stable analogs of prostaglandins did not affect the ERG. Both increases and subsequent decreases in ERG wave amplitudes following light exposure in vivo were associated with increases in retinal prostaglandin and malondialdehyde (peroxidation product) levels, which were inhibited by the nonselective PGHS blockers, naproxen and diclofenac. Similar observations were made in vitro on isolated porcine eyecups as well as on retinal membranes exposed to light (250 fc/ 2700 lx) 380-650 nm and 380-440 nm but not at > 500 nm. Both PGHS-1 and PGHS-2 contributed equivalently to light-induced prostaglandin synthesis, as shown after selective PGHS-2 blockers, but mRNA expression of PGHS-1 and 2 was not affected by light. Finally, light stimulated activities of pure PGHS-1 and PGHS-2 isozymes, and these were also shown to produce superoxide radical (detected with fluorogenic spin trap, proxyl fluorescamine). Taken together, data suggest that PGHS- (1 and 2) is activated by short wavelength visible light, and in the retina is an important source of reactive oxygen species which in turn alter retinal electrophysiological function. PGHS thus seems a likely chromophore in setting forth photic-induced retinal injury. Findings provide an explanation for increased sensitivity of the retina to visible light predominantly at the far blue range of its spectrum.

Animals↗

Hand-held microanalytical instrument for chip-based electrophoretic separations of proteins.

The design, fabrication, and demonstration of a hand-held microchip-based analytical instrument for detection and identification of proteins and other biomolecules are reported. The overall system, referred to as muChemLab, has a modular design that provides for reliability and flexibility and that facilitates rapid assembly, fluid and microchip replacement, troubleshooting, and sample analysis. Components include two independent separation modules that incorporate interchangeable fluid cartridges, a 2-cm-square fused-silica microfluidic chip, and a miniature laser-induced fluorescence detection module. A custom O-ring sealed manifold plate connects chip access ports to a fluids cartridge and a syringe injection port and provides sample introduction and world-to-chip interface. Other novel microfluidic connectors include capillary needle fittings for fluidic connection between septum-sealed fluid reservoirs and the manifold housing the chip, enabling rapid chip priming and fluids replacement. Programmable high-voltage power supplies provide bidirectional currents up to 100 microAlpha at 5000 V, enabling real-time current and voltage monitoring and facilitating troubleshooting and methods development. Laser-induced fluorescence detection allows picomolar (10(-11) M) detection sensitivity of fluorescent dyes and nanomolar sensitivity (10(-9) M) for fluorescamine-labeled proteins. Migration time reproducibility was significantly improved when separations were performed under constant current control (0.5-1%) as compared to constant voltage control (2-8%).

Electrophoresis, Microchip↗

Trace determination of hydroxyl radical in biological systems.

A simple and highly sensitive method to quantify the rates of production of OH in biological systems is described. This method employs the reaction between OH and dimethyl sulfoxide to generate quantitatively a methyl radical, which then reacts with a fluorescamine-derivatized nitroxide to produce the stable O-methylhydroxylamine. This O-methylhydroxylamine is separated by reversed-phase high-performance liquid chromatography and quantified fluorometrically. The estimated detection limit of the O-methylhydroxylamine is 3.5 nM for a 50 microL injection at a signal to noise ratio of 2. The method is applied to the determination of the rates of OH production in a biologically relevant model system and in a mouse epidermal cell line treated with a quinone anticancer compound.

Animals↗

Evidence for temperature-dependent conformational changes in the L-lactate dehydrogenase from Bacillus stearothermophilus.

L-Lactate dehydrogenase from Bacillus stearothermophilus (BSLDH) has been shown to change its conformation in a temperature-dependent manner in the temperature range between 25 and 70 degrees C. To provide a more detailed understanding of this reversible structural reorganization of the tetrameric form of BSLDH, we have determined in the presence of 5 mM fructose, 1,6-bisphosphate (FBP) the effect of temperature on far-UV and near-UV circular dichroism (CD), Nile red-binding to the enzyme surface, NADH binding, fluorescence polarization of fluorescamine-labeled protein, and hydrogen-deuterium exchange. In addition, we have analyzed the temperature dependence of the dimer-tetramer equilibrium of this protein by steady-state enzyme kinetics in the absence of FBP. The results obtained from these measurements at various temperatures can be summarized as follows. No changes in the secondary-structure distribution are detectable from far-UV CD measurements. On the other hand, near-UV CD data reveal that changes in the arrangements of aromatic side chains do occur. With increasing temperature, the asymmetry of the environment around aromatic residues decreases with a small change at 45 degrees C and a more pronounced change at 65 degrees C. Nile red-binding data suggest that the BSLDH surface hydrophobicity changes with temperature. It appears that decreasing the surface hydrophobicity may be a strategy to increase the protein stability of the active enzyme. We have noted significant alterations in the thermodynamic binding parameters of NADH above 45 degrees C, indicating a conformational change in the active site at 45 degrees C. The hydrodynamic volume of BSLDH is also temperature dependent.(ABSTRACT TRUNCATED AT 250 WORDS)

Chemical Phenomena↗

Model of fibronectin tertiary structure based on studies of interactions between fragments.

Human plasma fibronectin aggregates in solution and is thought to form fibrils on cell surfaces, perhaps by self-associating and by interacting with other components such as proteoglycans. We have localized the self-association domains by testing the ability of various fragments of fibronectin to interact with each other. Complexation between fluorescamine-labeled fragments and unlabeled fragments or whole molecules was assessed by gel filtration high-performance liquid chromatography. The fragments studied included nonoverlapping fragments that are situated on the fibronectin polypeptide chain in the following order, beginning from the amino terminus: the 29-, 50-, 120-, 35-, and 25-kDa fragments, as well as multiple-domain fragments of 72 kDa containing the 29- and 50-kDa segments, a fragment of 150 kDa containing the 120- and 35-kDa segment, a fragment of 190 kDa containing the 120- and 35-kDa segments, a fragment of 190 kDa containing the 50-, 150-, and 25-kDa segments, and a 45-kDa fragment containing the 35-kDa segment. The amino-terminal 29-kDa fragment bound to the carboxyl-terminal heparin-binding (Hep II) 35-kDa fragment as well as the 150- and 190-kDa fragments that contain the 35-kDa segment. On the other hand, carboxyl-terminal 35- and 45-kDa Hep II containing fragments bound to each other as well as to amino-terminal 29- and 72-kDa fragments and to the 190-kDa fragment. Further, the 25-kDa carboxyl-terminal fibrin-binding fragment bound the 190-kDa fragment, the only fragment containing the 25-kDa segment.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

Characterization of the cytochrome c oxidase in isolated and purified plasma membranes from the cyanobacterium Anacystis nidulans.

Functionally intact plasma membranes were isolated from the cyanobacterium (blue-green alga) Anacystis nidulans through French pressure cell extrusion of lysozyme/EDTA-treated cells, separated from thylakoid membranes by discontinuous sucrose density gradient centrifugation, and purified by repeated recentrifugation. Origin and identity of the chlorophyll-free plasma membrane fraction were confirmed by labeling of intact cells with impermeant protein markers, [35S]diazobenzenesulfonate and fluorescamine, prior to membrane isolation. Rates of oxidation of reduced horse heart cytochrome c by purified plasma and thylakoid membranes were 90 and 2 nmol min-1 (mg of protein)-1, respectively. The cytochrome oxidase in isolated plasma membranes was identified as a copper-containing aa3-type enzyme from the properties of its redox-active and EDTA-resistant Cu2+ ESR signal, the characteristic inhibition profile, reduced minus oxidized difference spectra, carbon monoxide difference spectra, photoaction and photodissociation spectra of the CO-inhibited enzyme, and immunological cross-reaction of two subunits of the enzyme with antibodies against subunits I and II, and the holoenzyme, of Paracoccus denitrificans aa3-type cytochrome oxidase. The data presented are the first comprehensive evidence for the occurrence of aa3-type cytochrome oxidase in the plasma membrane of a cyanobacterium similar to the corresponding mitochondrial enzyme (EC 1.9.3.1).

Cell Fractionation↗

Synthesis, purification, and chemical characterization of the amino-terminal 1-34 fragment of bovine parathyroid hormone synthesized by the solid-phase procedure.

Peptides prepared by solid-phase synthesis during a systematic study of structure-activity relations in parathyroid hormone have been subjected, after sequential purifications, to rigorous analysis of purity by a variety of analytical techniques including sequence analysis by the Edman procedure. The present paper undertakes a critical appraisal of the utility of different tests of peptide purity and the use of the procedures in guiding and monitoring optimal synthesis strategies. Sequence analysis of a peptide representing the amino-terminal 34 residues of bovine parathyroid hormone (bPTH-(1-34)) revealed the presence of at least 30% of contaminating error peptides which were undetected by other analytical procedures. The major contaminant was identified as a peptid in which glutamine at position 29 was deleted. A repeat synthesis using fluorescamine rather than ninhydrin to monitor the coupling reaction resulted in a preparation that lacked the contaminant resulting from deletion. These findings demonstrate the particular value of sequence analysis in the evaluation of purity of peptides synthesized by the solid-phase technique.

Adenylyl Cyclases↗

Kinetics of the action of papain on fluorescent peptide substrates.

Kinetic measurements have been performed on the action of papain on mansyl-Gly-Val-Glu-Leu-Gly and on mansyl-Gly-Gly-Val-Glu-Leu-Gly, both of which are cleaved solely at the Glu-Leu bond under the conditions of our experiments. Stopped-flow experiments have shown that, under conditions of enzyme excess, the enhancement of the fluorescence of the mansyl group upon association of each of the oligopeptide substrates with papain is a biphasic process. A very rapid initial increase in fluorescence is followed by a slower first-order fluorescence enhancement. The observed rate constant for the latter process is greater with the mansyl pentapeptide than with the mansyl hexapeptide. A similar biphasic fluorescence change is seen upon the interaction of the mansyl peptides with mercuripapain, but the second step is much slower than in the case of the active enzyme. The rate of the second step in the association of active papain with the mansyl paptides shows saturation with increasing enzyme concentration, supporting the view that an initial enzyme-substrate complex (ES) is converted in a first-order process to the complex (ES) that undergoes cleavage to form products. The hydrolysis of the Glu-Leu bond is associated with a first-order decrease in fluorescence, as a consequence of the formation of the mansyl peptide product, which is bound less strongly than the substrate. The rate constant for this process is about 140 times greater with the mansyl hexapeptide than with the mansyl pentapeptide, thus giving further indication of the importance of secondary enzyme-substrate interactions in the efficiency of papain catalysis. For each of the two mansyl peptides, the values of the rate constants and the apparent Michaelis constants associated with the cleavage of the Glu-Leu bond, as determined by stopped-flow measurements under conditions of enzyme excess, were the same, within the precision of the data, as those estimated from experiments under conditions of substrate excess, where the formation of Leu-Gly was determined by means of the fluorescamine reaction. This indicates that, with these substrates, the rate-limiting step in the overall catalytic process is associated with the breakdown of ES. Estimates are given of the dissociation constant of ES and of the rate constants in the interconversion of ES and ES.

Fluorescence↗

Fluorescence energy transfer between ligand binding sites on aspartate transcarbamylase.

The method of fluorescence energy transfer is used to measure the distances between several sites on aspartate transcarbamylase. Both fluorescence steady-state and lifetime techniques are used. When the tryptophans on the catalytic subunit are the fluorescent donor groups, either pyridoxamine phosphate, covalently bound to an amino group at the active site, or 8-anilino-1-naphthalenesulfonate, noncovalently bound at the active site, is the acceptor group. The distance between tryptophan and the active site is calculated to be 2e A assuming that the fluorescence of only one tryptophan per catalytic polypeptide chain is quenched by the acceptor or 27 A assuming that both tryptophans on a catalytic chain are equally quenched. The pyridoxamine phosphate label is also used as the fluorescent donor with mercurinitrophenol bound to the sulfhydryl group of the catalytic subunit as the energy acceptor. For this pair of labels the active site is determined to be very close to the sulfhydryl group on the same catalytic chain and 26 A from the sulfhydryl groups on the other chains of the catalytic trimer. In experiments with pyridoxamine phosphate at the active site as the donor and 8-anilino-1-naphthalenesulfonate at the active site as the acceptor, a distance of 26 A between active sites of a catalytic trimer is found. No energy transfer is observed from pyridoxamine phosphate at the active site to a fluorescamine derivative of cytidine 5'-triphosphate at the regulatory site. This implies that these groups are separated by at least 42 A in the native enzyme. All of the distances are calculated using the assumption of rapid rotation of donor and acceptor dipole moments relative to the donor fluorescence lifetime. Fluorescence polarization measurements suggest this assumption does not produce a significant error in the calculated distances. The distances between the various sites are related to the subunit structure of aspartate transcarbamylase.

Anilino Naphthalenesulfonates↗

Random versus selective membrane phospholipid oxidation in apoptosis: role of phosphatidylserine.

The formation of reactive oxygen species has been associated with apoptosis. To assess the role of lipid peroxidation in apoptosis, we used 2,2'-azobis(2,4-dimethylisovaleronitrile) (AMVN) to generate peroxyl radicals within cellular membranes of HL-60 cells. cis-Parinaric acid (cis-PnA) metabolically integrated into phospholipids of HL-60 cells was used as a probe to assess the extent of lipid peroxidation within specific phospholipid classes. Within 2 h, AMVN (500 microM) randomly oxidized more than 85% of cis-PnA contained in all major classes of phospholipids. AMVN-induced lipid peroxidation was followed by apoptosis as determined by nuclear condensation, DNA fragmentation, and annexin V binding to externalized phosphatidylserine (PS). Fluorescamine derivatization of external aminophospholipids revealed that PS, but not phosphatidylethanolamine, was externalized. The vitamin E analogue, 6-hydroxy-2,2,5,7,8-pentamethylchromane (PMC), inhibited overall oxidation of cis-PnA in phospholipids by more than 85%. Not all phospholipids, however, were equally protected. Phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, and sphingomyelin were nearly completely protected by PMC, while oxidation of PS was unaffected in whole living cells. The insensitivity of PS to PMC was not an intrinsic property because PMC protected all lipids equally during AMVN oxidation of liposomes prepared from cis-PnA-labeled cells. The potential role for PS oxidation in apoptosis was further suggested by the faithful execution of apoptosis following coexposure of cells to AMVN and PMC.

Antioxidants↗