O-phthalaldehyde based quantification of polysaccharide modification in conjugate vaccines

Polysaccharide-based vaccines cannot stimulate long-lasting immune response in infants due to their inability to elicit a T-cell-dependent immune response. This has been addressed using conjugation technology, where conjugates were produced by coupling a carrier protein to polysaccharides using different conjugation chemistries, such as cyanylation, reductive amination, ethylene diamine reaction, and others. Many glycoconjugate vaccines that are manufactured using different conjugation technologies are already in the market for neonates, infants and young children (e.g., Haemophilus influenzae type-b, Streptococcus pneumoniae and Neisseria meningitidis vaccines), and all of them elicit a T-cell dependent immune response. To manufacture glycoconjugate vaccines, the capsular polysaccharide is first activated by converting its hydroxyl groups to aldehyde-, cyanyl-, or cyanate ester groups, depending on the conjugation chemistry selected. The oxidized and reduced aldehyde functional groups of the polysaccharides are subsequently reacted with the amino groups of carrier protein by reductive amination to form a stable amide bond. In CDAP-based conjugation, the polysaccharide -OH groups are activated to form cyanyl-, or cyanate ester groups to react with the amino groups of carrier protein and forms an isourea bond. Understanding the extent of polysaccharide activation/modification is essential since it directly influences the molar mass of the conjugate, its stability, and the immunogenicity of the product. Reported methods are available to estimate the aldehyde groups of polysaccharides generated by reductive amination. However, no method is available to quantify the cyanyl or cyanate ester (-OCN) groups generated by cyanylation with 1-cyano-4-dimethylaminopyridinium tetrafluoroborate (CDAP). We report a novel strategy using an O-phthalaldehyde (OPA) derivatization process followed by size-exclusion chromatography (SEC) high-performance liquid chromatography (HPLC) separation and UV detection. The cyanate ester groups on the activated polysaccharide directly reveal the extent of polysaccharide activation/modification and the residual activated groups in the purified conjugates. This method would be useful for conjugate vaccine manufacturing using CDAP chemistry.

An improved method for determining free amino acids by RP-HPLC/DAD with o-phthalaldehyde derivatization: Method evaluation in beers and wines

Rapid methods for amino acid determination are desired to reduce running times, and the main factors involved in the rapid separation of these compounds in HPLC are the columns, solvents, and gradient. The present study refers to a method optimization to rapidly analyze 19 amino acids in RP-HPLC/DAD with pre-column derivatization using o-phthalaldehyde. To evaluate the method's robustness, Indian Pale Ale-IPA beers and wines from the San Francisco Valley-SFV and Chapada Diamantina-CHD, Brazil, were analyzed. The method showed acceptable linearity (R2 > 0.992), precision (CV < 3.96%), recovery (74.2-113%), detection limits (<0.56 mg/L), and quantification limits (<3.62 mg/L) and separation gradient in 18.5 min. IPA beers were discriminated from wines by arginine, asparagine, tryptophan, alanine, phenylalanine, and tyrosine contents. Furthermore, CHD wines were discriminated from SFV wines by asparagine, glutamine, arginine, cystine, tyrosine, and leucine. In conclusion, a rapid method for amino acid determination was optimized and validated for wines and beers.

Analysis of Gizzerosine in Foodstuffs by HPLC Involving Pre-column Derivatization with o-Phthaldialdehyde

Gizzerosine [2-amino-9-(4-imidazolyl)-7-azanonanoic acid] is a toxic amino acid formed from histamine and lysine at high temperatures, and may be present in foodstuffs (e.g., fishmeal and meat-bone meal) for animals including cats and dogs. Here we developed a simple, rapid, sensitive, specific, and automated method for the analysis of gizzerosine in foodstuffs by high-performance liquid chromatography (HPLC) involving pre-column derivatization with o-phthaldialdehyde (OPA) in the presence of N-acetylcysteine (instead of the usual 2-mercaptoethanol or ethanethiol reagent). OPA reacted immediately (within 1 min) with gizzerosine in an autosampler at room temperatures (e.g., 20-25 °C), and their derivative was directly injected into the HPLC column. The highly fluorescent gizzerosine-OPA derivative was well separated from the OPA derivatives of all natural amino acids known to be present in physiological fluids (e.g., plasma), proteins and foodstuffs, and was detected at an excitation wavelength of 340 nm and an emission wavelength of 450 nm. The total time for chromatographic separation (including column regeneration) was 20 min per sample rather than 40 min and longer in previous HPLC methods. The detection limit for gizzerosine was at least 6 pmol/ml in an assay solution (HPLC vial) or at least 0.09 pmol per injection into the HPLC column. The analysis of gizzerosine was linear between 1 and 100 pmol per injection. When gizzerosine was extracted from foodstuffs, its detection limit was at least 875 pmol/g foodstuff or at least 0.21 mg/kg foodstuff. Our routine HPLC technique does not require any cleanup of samples or the OPA derivatization products (including the OPA-gizzerosine adduct), and is applicable for the analysis of gizzerosine in both foodstuffs and animal tissues.

The Effectiveness of Ultraviolet Smart D60 in Reducing Contamination of Flexible Fiberoptic Laryngoscopes

OBJECTIVE

To compare the effectiveness of disinfection protocols utilizing a ultraviolet (UV) Smart D60 light system with Impelux™ technology with a standard Cidex ortho-phthalaldehyde (OPA) disinfection protocol for cleaning flexible fiberoptic laryngoscopes (FFLs).

METHODS

Two hundred FFLs were tested for bacterial contamination after routine use, and another 200 FFLs were tested after disinfection with one of four methods: enzymatic detergent plus Cidex OPA (standard), enzymatic detergent plus UV Smart D60, microfiber cloth plus UV Smart D60, and nonsterile wipe plus UV Smart D60. Pre- and post-disinfection microbial burden levels and positive culture rates were compared using Kruskal-Wallis ANOVA and Fisher's two-sided exact, respectively.

RESULTS

After routine use, approximately 56% (112/200) of FFLs were contaminated, with an average contamination level of 9,973.7 ± 70,136.3 CFU/mL. The standard reprocessing method showed no positive cultures. The enzymatic plus UV, microfiber plus UV, and nonsterile wipe plus UV methods yielded contamination rates of 4% (2/50), 6% (3/50), and 12% (6/50), respectively, with no significant differences among the treatment groups (p > 0.05). The pre-disinfection microbial burden levels decreased significantly after each disinfection technique (p < 0.001). The average microbial burden recovered after enzymatic plus UV, microfiber plus UV, and nonsterile wipe plus UV were 0.40 CFU/mL ± 2, 0.60 CFU/mL ± 2.4, and 12.2 CFU/mL ± 69.5, respectively, with no significant difference among the treatment groups (p > 0.05). Micrococcus species (53.8%) were most frequently isolated, and no high-concern organisms were recovered.

CONCLUSION

Disinfection protocols utilizing UV Smart D60 were as effective as the standard chemical disinfection protocol using Cidex OPA.

LEVEL OF EVIDENCE

NA Laryngoscope, 133:3512-3519, 2023.

Efficacy of high-level disinfection of endoscopes contaminated with Streptococcus equi subspecies equi with 2 different disinfectants

BACKGROUND

Prevention of spread of Streptococcus equi subspecies equi (S. equi) after an outbreak is best accomplished by endoscopic lavage of the guttural pouch, with samples tested by culture and real time, quantitative polymerase chain reaction (qPCR). Disinfection of endoscopes must eliminate bacteria and DNA to avoid false diagnosis of carrier horses of S. equi.

HYPOTHESIS/OBJECTIVES

Compare failure rates of disinfection of endoscopes contaminated with S. equi using 2 disinfectants (accelerated hydrogen peroxide [AHP] or ortho-phthalaldehyde [OPA]). The null hypothesis was that there would be no difference between the AHP and OPA products (based on culture and qPCR results) after disinfection.

METHODS

Endoscopes contaminated with S. equi were disinfected using AHP, OPA or water (control). Samples were collected before and after disinfection and submitted for detection of S. equi by culture and qPCR. Using a multivariable logistic regression model-adjusted probability, with endoscope and day as controlled variables, the probability of an endoscope being qPCR-positive was determined.

RESULTS

After disinfection, all endoscopes were culture-negative (0%). However, the raw unadjusted qPCR data were positive for 33% AHP, 73% OPA, and 71% control samples. The model-adjusted probability of being qPCR-positive after AHP disinfection was lower (0.31; 95% confidence interval [CI], -0.03-0.64) compared to OPA (0.81; 95% CI, 0.55-1.06), and control (0.72; 95% CI, 0.41-1.04).

CONCLUSION AND CLINICAL IMPORTANCE

Disinfection using the AHP product resulted in significantly lower probability of endoscopes being qPCR-positive compared to the OPA product and control.

A photoluminescence sensor for in-situ monitoring of the dopamine neurotransmitters released from PC12 cells

Constructing simple, stable, fast, and sensitive neurotransmitter-based sensors is a promising tool to diagnose neurological diseases. Dopamine (DA), "a catecholamine neurotransmitter" is important in transmitting nerve impulses. Therefore, great attention is taken to monitor DA concentrations received. The challenge in developing a DA-based sensor is to enhance its stability and sensitivity. Thus, we have used o-phthalaldehyde (OPA)/2-mercapto ethanol (2ME)/mesoporous silica instated of 2ME in solution. Here we have successfully developed a fluorescence DA neurotransmitters sensor. The sensor was used for detecting a wide range of concentrations of DA (5 nM to 5 µM). Effects of pH (4.3-11.4) and temperatures (25-70 °C) on the sensor efficiency were investigated. The detection limit was 1.35 × 10^-11 mol/dm³, which is lower than the normal DA level in the central nervous system. The results indicated that using OPA/2ME/MSNPs has long-time stability over a year of its preparation. Moreover, the developed sensor showed high specificity towards DA in the presence of different interferences such as ascorbic acid or another catecholamine neurotransmitter such as γ-aminobutyric acid. Finally, the fabricated biosensor was used to monitor the DA neurotransmitter released from PC12 cells. Hence, it was successfully developed a simple and stable probe for accurate photoluminescence detection of DA neurotransmitters.

O-phthalaldehyde assisted surface enhanced Raman spectroscopy selective determination of trace homocysteine in serum

High plasma homocysteine (Hcy) levels may indicate cardiovascular disease. However, sensitive and selective determination of Hcy remains a major challenge. Herein, we present a sensing strategy for Hcy by surface enhanced Raman scattering (SERS) method along with a specific reaction of o-phthalaldehyde (OPA) and Hcy. The obtained adduct 2-(1-carboxyl-3-thiopropyl)-1-isoindolinone (Hcy-OPA) can be directly detected by SERS using gold nanoparticles (Au NPs) as the substrate. The developed SERS method displays superior sensitivity (low detection limit of 2.50 × 10^-12 mol L^-1) with a broad linear range (5.00 × 10^-10 -5.00 × 10^-6 mol L^-1). As a proof of real application, it can be used to detect Hcy in bovine serum samples with a concentration as low as 5.00 × 10^-9 mol L^-1, which is free from the interference of the other amino acids and glutathione.

Screening of Oxygenated Aromatic Compounds for Potential Antifungal Activity against Geotrichum citri-aurantii through Structure-Activity Relationship Analysis

Sour rot caused by Geotrichum citri-aurantii (G. citri-aurantii) is responsible for huge economic losses during citrus fruit storage. However, the availability of chemical fungicides for controlling this disease is rather limited. In the present study, the antifungal activities of 25 oxygenated aromatic compounds against the mycelial growth of G. citri-aurantii were determined, and their corresponding structure-activity relationships were illustrated. Salicylaldehyde (pMIC = 2.689) possessed the strongest inhibitory effect on G. citri-aurantii growth, followed by thymol (pMIC = 2.478) and o-phthalaldehyde (pMIC = 2.429). Molecular electrostatic potential and molecular orbital analysis showed that the antifungal efficiency of test compounds was determined by the number and location of hydroxyl and aldehyde groups and the length of the ester chain. All compounds were selected for quantitative structure-antifungal activity relationship (QSAR) analysis. A three-dimensional-QSAR model of G. citri-aurantii inhibitors was established and demonstrated good predictive capability [comparative molecular field analysis, q² = 0.532, optimum number of components (ONC) =10, R² = 0.996, F = 560.325, standard error of estimation (SEE) = 0.034, and two descriptors; comparative similarity index analysis, q² = 0.675, ONC = 6, R² = 0.989, F = 263.354, SEE = 0.054, and five descriptors]. QSAR analysis showed that substitution at position 1 with hydrophilic and electron-withdrawing groups produced a hydrogen donor and thus improved the antifungal activity. In contrast, substitution at positions 4 or 5 with hydrophilic and electron-donating groups decreased its antifungal activity. These findings can provide theoretical guidance for preparing effective antifungal drugs for controlling sour rot in citrus.

A stable naked-eye colorimetric sensor for monitoring release of extracellular gamma-aminobutyric acid (GABA) neurotransmitter from SH-SY5Y cells

A novel optical γ-aminobutyric acid (GABA)-based sensor was developed on interacting thiol compounds and o-phthalaldehyde (OPA) to form thiacetal compounds. Then, the thiacetal interacts with the GABA molecule to form an isoindole compound. The effects of four thiol compounds on the stability of the resulting isoindole compound were assessed. The 2-mercaptoethanol, "one of the most used derivatizing agents," is unexpectedly the least stable; while, 16-mercaptohexadecanoic acid resulted in the most durable isoindole compound. The developed sensor showed the capability for detecting GABA within a wide concentration range spanning from 500 nmol L^-1 to 100 µmol L^-1. The detection limit was about 330 nmol L^-1, which indicated the high sensitivity of the developed sensor compared with those previously reported. The findings illustrated the ability to detect GABA at the physiological pH (pH = 7.4) without adjusting the pH value, opening the door for real applications. Furthermore, the sensor could detect various GABA concentrations in human serum with good recovery percentages (98% to 101.4%). In addition, this assay was applied to monitor GABA release from the SH-SY5Y cell line to convert glutamate into GABA. This result indicates the capability of the proposed assay for visually monitoring the release of GABA neurotransmitters.

Selective reaction of homocysteine with o-phthalaldehyde under flow conditions in highly alkaline medium: fluorimetric determination using zone fluidics

In the present study we report the reaction between homocysteine and o-phthalaldehyde under flow conditions. Homocysteine reacts on-line with the derivatization reagent in a strong alkaline medium and in the absence of nucleophilic reagents to yield a fluorescent derivative (λ_ex /λ_em = 370/480 nm). The reaction variables were investigated using the concept of zone fluidics. Selectivity factors against other compounds were calculated at 10-fold excess. The findings formed the basis of an automated proposed method that was found to be linear in the range 0.1-1.5 μmol L^-1 , with a limit of detection of 20 nmol L^-1 and relative standard deviation < 0.5% (within-day) and 3.2% (between-day). The method proved to be rapid, offering a practical sampling rate of 24 h^-1 and accurate following application to an artificial urine matrix with minimum dilution.

Capillary electrophoretic analysis of gamma-aminobutyric acid and alanine in tea with in-capillary derivatization and fluorescence detection

The aim of this study was to investigate an in-capillary derivatization capillary electrophoresis (CE) technique that was performed to determine the concentration of gamma-aminobutyric acid (GABA) and alanine (Ala) in tea after being derivatized with o-phthaldialdehyde/2-mercaptoethanol (OPA/2-ME) to form fluorescence-labeled products. The conditions of labeled derivatization and CE separation were optimized and then applied to real sample analysis. The labeled derivatization with 20 mM OPA and 26.67 mM 2-ME (mol ratio=0.75) at pH 10 offered the most sensitive detection, and the separation with 30 mM sodium tetraborate buffer (pH 10.0) under 21 kV achieved good selectivity within 14 min. The detections were linear in the range of 0.05-5 microM with correlation coefficients (R2) of 0.9995 and 0.9964 and with detection limits of 0.004 and 0.02 microM for GABA and Ala, respectively. The recoveries were 94.22% (3.58% RSD) and 93.54% (6.46% RSD) for five determinations of GABA and Ala, respectively. This method is a fast, convenient, sensitive, and eco-friendly way to determine the GABA and Ala in tea samples from different manufacturing processes.

[Clinical importance of guideline for decontamination of endoscopes in urological field: verification of 3 processes]

Clinical guideline for decontamination of endoscopes in urological field has not been provided, although endoscopic examination should be done in aseptic circumstance.

MATERIAL AND METHOD

From decontamination processes, following 3 points were selected for verification: 1) Volume of residual water in flexible scope after rinsing, estimated by weight change. 2) Concentration of eluted disinfectant from flexible scope after standard rinsing procedure for gastrointestinal endoscope. 3) Observation of possible damage of telescope, caused by repeat autoclaving.

RESULTS

Wet condition of flexible scope could be suspected in 60 hours in room temperature. Eluted disinfectants were detected, but in harmless level. Repeated autoclaving merely caused minor damage, which does not interfere clinical use.

CONCLUSION

We obtained a couple of evidences with cautions in decontamination processes for endoscopes. Urgent requirement of standardization in this field should be discussed widely.

Biogenic amines in natural ciders

Biogenic amines play an important physiological role in mammals, and high amounts of some exogenous amines in human diet may contribute to a wide variety of toxic effects. These amines are commonly found in many foodstuffs, particularly in fermented products such as cheese, meat products, beer, wine, and ciders. Here, the level of biogenic amines in some natural ciders was examined. Twenty-four samples of cider purchased from commercial sources were analyzed by reverse-phase high-performance liquid chromatography and fluorescence detection after precolumn derivatization with o-phthaldialdehyde. Amine levels were variable, ranging from not detected to 23 mg/liter. The average level of total biogenic amines in ciders was 5.94 +/- 8.42 mg/liter. Putrescine, histamine, and tyramine were the prevailing amines being present in 50.0, 37.5, and 33.3% of the ciders studied; very small amounts of ethylamine and phenylethylamine were observed in only one sample. Other cider parameters were analyzed to determine whether they affect the biogenic amine content in ciders, and the results were evaluated by applying cluster analysis and principal component analysis. Ciders that showed lower glycerol contents and higher amounts of 1,3-propanediol had much higher levels of histamine, tyramine, and putrescine, suggesting a high activity of lactic acid bacteria during cider making and thus the need for effective control of lactic acid bacteria.

Determination of theanine in commercial tea by liquid chromatography with fluorescence and diode array ultraviolet detection

Two liquid chromatographic methods that involve precolumn derivatization with o-phthaladehyde (OPA) and phenylisothiocyanate (PITC) with fluorescence and diode array UV detection for the determination of theanine have been developed. The chromatographic separations were achieved by reverse-phase high-performance liquid chromatography using octadecyl columns and gradient elution. The methods were applied to evaluate the theanine content of commercial tea leaves. The coefficient of variation of the peak area repeatability for within day (n = 8) and between day (n = 8 over 10 days) was lower than 3% for both of the methods. The estimated limit of detection (LOD) and limit of quantitation (LOQ) for the OPA method was 0.12 and 0.35 microg theanine, respectively. The PITC method was 500-fold more sensitive with LOD and LOQ values of 0.25 and 0.75 ng, respectively. The theanine content of the commercial tea samples varied from 2-5 mg/g leaf. The overall % recoveries for these methods ranged from 93-99.3. The sensitivity and simplicity of the method render them suitable for use in quality control laboratories.

Single-step enantioselective amino acid flux analysis by capillary electrophoresis using on-line sample preconcentration with chemical derivatization

Capillary electrophoresis (CE) represents a versatile platform for integrating sample pretreatment with chemical analysis because of its ability to tune analyte electromigration and band dispersion properties in discontinuous electrolyte systems. In this article, a single-step method that combines on-line sample preconcentration with in-capillary chemical derivatization is developed for rapid, sensitive, and enantioselective analysis of micromolar levels of amino acids that lack intrinsic chromophores by CE with UV detection. Time-resolved electrophoretic studies revealed two distinct stages of amino acid band narrowing within the original long sample injection plug occurring both prior to and after in-capillary labeling via zone passing by ortho-phthalaldehyde/N-acetyl l-cysteine (OPA/NAC). This technique enabled direct analysis of d-amino acids in a 95% enantiomeric excess mixture with sub-micromolar detection limits and minimal sample handling, where the capillary functions as a preconcentrator, microreactor, and chiral selector. On-line sample preconcentration with chemical derivatization CE (SPCD-CE) was applied to study the enantioselective amino acid flux in Escherichia coli bacteria cultures, which demonstrated a unique l-Ala efflux into the extracellular medium. New strategies for high-throughput analyses of low-abundance metabolites are important for understanding fundamental physiological processes in bacteria required for screening the efficacy of new classes of antibiotics as well as altered metabolism in genetically modified mutant strains.

Rapid Determination of Vitellogenin in Fish Plasma by Anion Exchange High Performance Liquid Chromatography Using Postcolumn Fluorescence Derivatization with o-Phthalaldehyde

An analytical method involving anion exchange high performance liquid chromatographic determination of vitellogenin (Vtg) in fish plasma after postcolumn fluorescence derivatization with o-phthalaldehyde (OPA) was developed. The retention time of Vtg was about 11 min. The reagent variables for derivatization were optimized. The fluorophore was excited at 335 nm and detected at 435 nm. A calibration curve was established ranging from 0.13 to 11.28 microg. The determination limit of Vtg was found to be as low as 0.13 microg. The spiked recovery was 93.6% and interassay variability was less than 4%. The method developed was used to determine Vtg in fish plasma obtained from red sea bream (Pagrosomus major), black porgy (Sparus macrocephalus) and skew band grunt (Hapalogenys nitens), without complicated sample pretreatment. The results confirmed that the method showed advantages of being simple, rapid, reproducible and sensitive.

On-line sample preconcentration with chemical derivatization of bacterial biomarkers by capillary electrophoresis: A dual strategy for integrating sample pretreatment with chemical analysis

Simple, selective yet sensitive methods to quantify low-abundance bacterial biomarkers derived from complex samples are required in clinical, biological, and environmental applications. In this report, a new strategy to integrate sample pretreatment with chemical analysis is investigated using on-line preconcentration with chemical derivatization by CE and UV detection. Single-step enantioselective analysis of muramic acid (MA) and diaminopimelic acid (DAP) was achieved by CE via sample enrichment by dynamic pH junction with ortho-phthalaldehyde/N-acetyl-L-cysteine labeling directly in-capillary. The optimized method resulted in up to a 100-fold enhancement in concentration sensitivity compared to conventional off-line derivatization procedures. The method was also applied toward the detection of micromolar levels of MA and DAP excreted in the extracellular medium of Escherichia coli bacterial cell cultures. On-line preconcentration with chemical derivatization by CE represents a unique approach for conducting rapid, sensitive, and high-throughput analyses of other classes of amino acid and amino sugar metabolites with reduced sample handling, where the capillary functions simultaneously as a concentrator, microreactor, and chiral selector.

Simultaneous high-performance liquid chromatographic analysis of pregabalin, gabapentin and vigabatrin in human serum by precolumn derivatization with o-phtaldialdehyde and fluorescence detection

A rapid, simple and robust method is presented for the simultaneous determination of the gamma-amino-n-butyric acid (GABA) derivatives pregabalin (PGB), gabapentin (GBP) and vigabatrin (VGB) in human serum by high-performance liquid chromatography (HPLC). Serum is deproteinized with trichloroacetic acid and aliquots of the supernatant are precolumn derivatized with o-phtaldialdehyde (OPA) and 3-mercaptopropionic acid. Separation is achieved on a Alltima 3C18 column using isocratic elution; the drugs are monitored using fluorescence detection. Norvaline is used as an internal standard. Within-day precision (COV; n = 10) is 1.2% for PGB (serum concentration 10.0 mg/l), 1.1% for GBP (serum concentration 15.8 mg/l) and 0.3% for VGB (serum concentration 15.5 mg/l). The method is linear up to at least 63 mg/l for PGB, 40 mg/l for GBP and 62 mg/l for VGB. Lower limits of quantitation (LOQ) are 0.13 mg/l for PGB, 0.53 mg/l for GBP and 0.06 mg/l for VGB. No interferences were found from commonly coadministered antiepileptic drugs (AEDs) and from endogenous amino acids. Experimental design in combination with statistical evaluation (ANOVA) was used to study the robustness of chromatography and sample preparation. The method is very suitable for routine therapeutic drug monitoring and for pharmacokinetic studies.

New protamine quantification method in microtiter plates using o-phthaldialdehyde/N-acetyl-l-cysteine reagent

Protamine is a well-known excipient in pharmaceutics. It represents a peptide consisting of exclusive aliphatic amino acids, hence it cannot be quantified by UV-spectroscopy (lambdamax 280 nm). A new and sensitive quantification method based on the derivatisation of protamine with ortho-phthaldialdehyde (OPA) in the presents of 2-mercaptoethanol (ME) or N-acetyl-L-cysteine (NAC) in basic aqueous solution using 96-well microtiter plates are introduced in this report. The resulting isoindol derivatives reveal a fluorescence excitation (maximum lambdaex 345 nm) and emission (maximum lambdaem 450 nm) spectra. Derivatives of OPA/NAC reagent were found to be useful for protamine quantification in pharmaceutical nanoparticle preparation containing DNA. A sufficient stability of the isoindol derivatives was shown. It was possible to determine protamine free base, protamine sulphate and protamine chloride with limits of detection less than 1.1 microg/ml.

Droplet-based chemistry on a programmable micro-chip

We describe the manipulation of aqueous droplets in an immiscible, low-permittivity suspending medium. Such droplets may serve as carriers for not only air- and water-borne samples, contaminants, chemical reagents, viral and gene products, and cells, but also the reagents to process and characterise these samples. We present proofs-of-concept for droplet manipulation through dielectrophoresis by: (1). moving droplets on a two-dimensional array of electrodes, (2). achieving dielectrically-activated droplet injection, (3). fusing and reacting droplets, and (4). conducting a basic biological assay through a combination of these steps. A long-term goal of this research is to provide a platform fluidic processor technology that can form the core of versatile, automated, micro-scale devices to perform chemical and biological assays at or near the point of care, which will increase the availability of modern medicine to people who do not have ready access to modern medical institutions, and decrease the cost and delays associated with that lack of access.

Simultaneous determination of inorganic nitrogen species by microcolumn ion chromatography

Inorganic nitrogen species (nitrate, nitrite and ammonium ions) were simultaneously determined by microcolumn ion chromatography. Nitrate and nitrite were determined by UV detection at 206 nm, whereas ammonium ion was determined by fluorescence detection at excitation 410 nm and emission 470 nm. The latter fluorescence detection is based on the postcolumn reaction of ammonium ion with o-phthalaldehyde in the presence of 2-mercaptoethanol. Effects of the reagent concentration, pH, and other reaction conditions on the signal intensity were examined, and the optimum condition was explored. The present method allowed simultaneous determination of nitrate, nitrite and ammonium ions in river water.

Endoscope disinfection by ortho-phthalaldehyde in a clinical setting: an evaluation of reprocessing time and costs compared with glutaraldehyde

Ortho-phthalaldehyde provides high-level disinfection in 12 minutes at room temperature (20 degrees C). To determine whether the endoscopy unit at Massachusetts General Hospital could cost-effectively increase endoscope throughput and decrease delayed procedures while maintaining biocidal efficacy with heavy use, ortho-phthalaldehyde solution (0.55% w/v) was used for high-level disinfection in place of glutaraldehyde in the unit's five automatic endoscope reprocessors. During this 38-day study, 1,839 endoscopes were processed in 1,201 cycles. Each machine ran an average of 80 disinfection cycles in each of three consecutive periods. The shorter disinfection time of ortho-phthalaldehyde (12 minutes) resulted in an average savings of 53 hours in disinfection time per study period for the five processors when compared with glutaraldehyde's 20-minute disinfection time.Ortho-phthalaldehyde costs more per gallon than glutaraldehyde ($31.03 versus $13.20). This higher cost would be offset, however, by additional time savings resulting from the fact that compared with glutaraldehyde, ortho-phthalaldehyde is faster-acting and a mixing and activation step is not required. In addition, testing prior to each cycle verified that despite heavy use, ortho-phthalaldehyde solution remained efficacious, lasting through an average of 80 cycles, whereas glutaraldehyde only lasts for an average of 40 cycles. Test strips showed the concentration of ortho-phthalaldehyde in the reprocessors remained above the minimum effective concentration for the entire 14-day maximal reuse period. Additional microbiological efficacy testing of spent solution diluted to its minimum effective concentration demonstrated the solution remained tuberculocidal in tests with Mycobacterium bovis.

A Versatile Route to 3-Benzoheteroepines Containing Group 15 and 16 Heavier Elements Involving Several Novel Ring Systems, and Their Thermal Stabilities

The C-unsubstituted 3-benzoheteroepines (2a-g) containing group 15 (P, As, Sb, and Bi) and group 16 (S, Se, and Te) heavier elements were prepared by the reaction of the corresponding metal reagents with (Z,Z)-o-bis(beta-lithiovinyl)benzene (5) which was derived in two steps from a common o-phthalaldehyde (3). The heteroepines (2) thus obtained were thermally labile towards heteroatom extrusion, and their half-lives on heating estimated from (1)H-NMR spectral analysis showed that the 3-benzoheteroepines (2) were far less stable than the corresponding 1-benzoheteroepines (1). The 2,4-bis(trimethylsilyl)-3-benzoheteroepines (17) containing Sb, Bi, and Te were also prepared from o-diiodobenzene (9) in 6 steps and were found to be more stable than the corresponding C-unsubstituted heteroepines (2).

Determination of bone and tissue concentrations of teicoplanin mixed with hydroxyapatite cement to repair cortical defects

A highly specific and sensitive isocratic reversed-phase high performance liquid chromatography (HPLC) method for the determination of the major component of teicoplanin in tissue is reported. Comparing fluorescamine and o-phthalaldehyde (OPA) as derivatizing agents, the derivative formed with the latter exhibits superior fluorescence intensity allowing detection of femtomole quantities. Pretreatment for tissue samples is by solid-phase extraction which uses Bakerbond PolarP C(18) cartridges and gives effective clean up from endogenous by-products. Linearity was given from 0.6 to 100 ng per injection. The coefficient of variation did not exceed 5.8% for both interday and intraday assays. It was found that when bone defects are repaired with a hydroxyapatite-teicoplanin mixture, the antibiotic does not degrade, even when it is in the cement for several months. The stability of teicoplanin in bone cement was determined fluorodensitometrically.

Gentamicin sulphate release from a modified commercial acrylic surgical radiopaque bone cement. I. Influence of the gentamicin concentration on the release process mechanism

The purpose of the present work was the study of the gentamicin sulphate (GS) release from a commercial acrylic bone cement CMW-1 with the aims of establishing the influence of the slabs preparation as well as the release mechanism and kinetics. The effect of the amount of GS on the release kinetic parameters has been also investigated. In vitro release studies were performed in a buffered saline solution at pH 7.4 and 37 degrees C. The GS concentration was determined using an indirect spectrophotometric method with an o-phthaldialdehyde as a derivatizing reagent. A commercial and three modified samples were tested. The free and fractured surfaces of the GS cement slabs before and after the release studies were observed by means of scanning electron microscopy (SEM). For low GS concentration loading the release was very incomplete because most of the GS beads were encapsulated by the hydrophobic PMMA matrix. A higher amount of antibiotic was released from cement that has a higher amount incorporated. A model and therefore a mechanism of release based on this model have been proposed. It has allowed us to explain the changes in dissolution kinetics of an acrylic matrix type controlled release system up to 12% GS loading. The cumulative amount of GS released M(t)/M(i), was fitted as a function of time. For lower amounts of GS, the regression analysis (R(2)>0.99) revealed that the release is most adequately represented by M(t)/M(i)=b+kt(n), where b represents a burst effect. The goodness of fit decreases as the amount of GS increases. The influence of some other type of release mechanism for higher amounts of GS must be taken into account and a second model for the release, M(t)/M(i)=b+k x [1-exp(-kt)], is proposed.

Selective detection of biogenic amines using capillary electrochromatography with an on-column derivatization technique

A selective detection method for biogenic amines present in highly complex matrixes was devised by employing both electrokinetic injection and on-column-derivatization capillary electrochromatographic methods. The on-column derivatization capillary electrochromatography system was evaluated by use of a capillary column (total length of 45 cm, effective length of 25 cm) fabricated using a 100-mcirom (i.d.) fused-silica capillary tube packed with 5-microm (i.d.) ODS particles that were tolerant of an alkaline environment. The column was filled with a run buffer consisting of a derivatization reagent, o-phthalaldehyde/2-mercaptoethanol, in a mixture of borate buffer (pH 10). After electrokinetic injection of a mixture of five biogenic amines (histamine, serotonin, tyramine, putrescine, cadaverine) as a test sample, the free amines entered into the anodic site of the capillary column and started to travel along the column, during which time the analytes reacted with the derivatization reagent, separated out, and were detected with an absorbance at 340 nm when high voltage was applied to the column. When this system was applied to a mixture containing 5 biogenic amines and 17 amino acids, the 5 biogenic amines plus arginine selectively entered into the capillary with the electrokinetic injection and were observed on the electrochromatogram, but none of the amino acids lacking arginine were detected. The designated method was also tested for its ability to determine the presence of biogenic amines in the crude extracts obtained from two types of aged fish.

Proteolytic activity of Staphylococcus xylosus strains on pork myofibrillar and sarcoplasmic proteins and use of selected strains in the production of "Naples type" salami

AIMS

The aim of this study was to determine the proteolytic activities of Staphylococcus xylosus strains on sarcoplasmic and myofibrillar proteins in order to evaluate the suitability of selected strains as starter cultures in the processing of a dry fermented pork sausage.

METHODS AND RESULTS

The proteolytic activity of 27 strains of Staphylococcus xylosus on sarcoplasmic and myofibrillar proteins was determined by agar plate method, o-phtaldialdehyde (OPA) spectrophotometric assay and sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Four strains were selected for the formulation of six starter cultures to use in the production of "Naples type" salami. The proteolytic contribution of starters was determined by SDS-PAGE, comparing the protein profile of inoculated sausages with that of uninoculated sausages after 0, 15 and 33 days of ripening. The results showed that the proteolytic activity of some strains, determined by the agar plate method, were not confirmed by electrophoretic and spectrophotometric assays. In fact, of 24 strains of Staphylococcus xylosus able to hydrolyse muscle protein extracts on agar plate, only 12 strains were shown to change SDS-PAGE profile of pork proteins. The SDS-PAGE profile of sarcoplasmic proteins extracted from all sausages showed that the major changes were produced with starters S3, S4 and S5 after 15 days of ripening. Also myofibrillar proteins undergo major changes after 15 days of ripening and the protein profiles showed the same pattern in all samples, except for the sausages produced with starter S4.

CONCLUSIONS

The results of this work showed that the muscle protein extracts hydrolysis test is suitable for preliminary screening of Staphylococcus xylosus strains on the basis of their proteolytic activity. However, evaluation of muscle protein hydrolysis in a food model system could then be more appropriate for selecting micro-organisms for use as starter cultures for fermented sausages.

SIGNIFICANCE AND IMPACT OF THE STUDY

The potential of the findings is discussed with reference to the formulation of starter cultures for the dry fermented sausages production.

Slow-tight binding inhibition of xylanase by an aspartic protease inhibitor: kinetic parameters and conformational changes that determine the affinity and selectivity of the bifunctional nature of the inhibitor

The first report of slow-tight inhibition of xylanase by a bifunctional inhibitor alkalo-thermophilic Bacillus inhibitor (ATBI), from an extremophilic Bacillus sp. is described. ATBI inhibits aspartic protease (Dash, C., and Rao, M. (2001) J. Biol. Chem., 276, 2487-2493) and xylanase (Xyl I) from a Thermomonospora sp. The steady-state kinetics revealed time-dependent competitive inhibition of Xyl I by ATBI, consistent with two-step inhibition mechanism. The inhibition followed a rapid equilibrium step to form a reversible enzyme-inhibitor complex (EI), which isomerizes to the second enzyme-inhibitor complex (EI*), which dissociated at a very slow rate. The rate constants determined for the isomerization of EI to EI*, and the dissociation of EI* were 13 +/- 1 x 10(-6) s(-1) and 5 +/- 0.5 x 10(-8) s(-1), respectively. The K(i) value for the formation of EI complex was 2.5 +/- 0.5 microm, whereas the overall inhibition constant K(i)* was 7 +/- 1 nm. The conformational changes induced in Xyl I by ATBI were monitored by fluorescence spectroscopy and the rate constants derived were in agreement with the kinetic data. Thus, the conformational alterations were correlated to the isomerization of EI to EI*. ATBI binds to the active site of the enzyme and disturbs the native interaction between the histidine and lysine, as demonstrated by the abolished isoindole fluorescence of o-phthalaldehyde (OPTA)-labeled Xyl I. Our results revealed that the inactivation of Xyl I is due to the disruption of the hydrogen-bonding network between the essential histidine and other residues involved in catalysis and a model depicting the probable interaction between ATBI or OPTA with Xyl I has been proposed.

Chemical marker for ALS-inhibitor herbicides: 2-aminobutyric acid proportional in sub-lethal applications

A chemical profiling technique for sub-lethal acetolactate synthase (ALS)-inhibitor herbicides (e.g., sulfonylureas, imidazolines, triazolopyrimidine sulfonanilides, and pyrimidyloxy salicylic) was developed using 2-aminobutyric acid, and was found to be directly proportional to application rates in field studies on two varieties of potato plants. An uncomplicated, benign-by-design analytical method for the determination of 2-aminobutyric acid in plant tissue was developed. The method is simple, fast, and automated, entailing a water-trichloroacetic acid extraction followed by precolumn on-line derivatization using o-phthalaldehyde (OPA) solution and liquid chromatographic analyses. Use of reagents and chlorinated organic solvents, and generation of waste, are minimized as compared to other ALS-inhibitor herbicide analytical techniques. Recoveries for a series of fortified plant tissues ranged from 82 to 103%. Two 20-day field trials on two potato varieties, Russet Burbank and Shepody, were conducted during the 2000 and 2001 growing seasons. The study demonstrated that the 2-aminobutyric acid method is an excellent, selective chemical marker technique for ALS-inhibitor herbicides for real world plant matrixes.

Chemical modification of specific active site amino acid residues of Enterobacter aerogenes glycerol dehydrogenase

Enterobacter aerogenes glycerol dehydrogenase (G1DH EC 1.1.1.6), a tetrameric NAD+ specific enzyme catalysing the interconversion of glycerol and dihydroxyacetone, was inactivated on reaction with pyridoxal 5-phosphate (PLP) and o-phthalaldehyde (OPA). Fluorescence spectra of PLP-modified, sodium borohydride-reduced G1DH indicated the specific modification of epsilon-amino groups of lysine residues. The extent of inhibition was concentration and time dependent. NAD+ and NADH provided complete protection against enzyme inactivation by PLP, indicating the reactive lysine is at or near the coenzyme binding site. Modification of G1DH by the bifunctional reagent OPA, which reacts specifically with proximal epsilon-NH2 group of lysines and -SH group of cysteines to form thioisoindole derivatives, inactivated the enzyme. Molecular weight determinations of the modified enzyme indicated the formation of intramolecular thioisoindole formation. Glycerol partially protected the enzyme against OPA inactivation, whereas NAD+ was ineffective. These results show that the lysine involved in the OPA reaction is different from the PLP-reactive lysine, which is at or near the coenzyme binding site. DTNB titration showed the presence of only a single cysteine residue per monomer of G1DH. This could be participating with a proximal lysine residue to form a thioisoindole derivative observed as a result of OPA modification.

Comparison of automated pre-column and post-column analysis of amino acid oligomers

It has been shown that various amino acids will polymerize under plausible prebiotic conditions on mineral surfaces, such as clays and soluble salts, to form varying amounts of oligomers (n = 2-6). The investigations of these surface reactions required a quantitative method for the separation and detection of these amino acid oligomers at the picomole level in the presence of nanomole levels of the parent amino acid. In initial high-performance liquid chromatography (HPLC) studies using a classical postcolumn o-phthalaldehyde (OPA) derivatization ion-exchange HPLC procedure with fluorescence detection, problems encountered included lengthy analysis time, inadequate separation and large relative differences in sensitivity for the separated species, expressed as a variable fluorescent yield, which contributed to poor quantitation. We have compared a simple, automated, pre-column OPA derivatization and reversed-phase HPLC method with the classical post-column OPA derivatization and ion-exchange HPLC procedure. A comparison of UV and fluorescent detection of the amino acid oligomers is also presented. The conclusion reached is that the pre-column OPA derivatization, reversed-phase HPLC and UV detection produces enhanced separation, improved sensitivity and faster analysis than post-column OPA derivatization, ion-exchange HPLC and fluorescence detection.

A fluorometric microassay for histamine release from human gingival mast cells

Mast cells are important effector cells of the immune system. We describe a rapid and inexpensive microassay to determine histamine release from human gingival mast cells. The assay is based on the coupling of histamine with o-phthalaldehyde (OPT) at a highly alkaline pH to form a fluorescent product. Using this assay with a sample volume of 10 microl/well in a 384 black well microplate, the histamine detection limit was 0.031 microg/ml. The human mast cell line (HMC-1) and fresh mast cells isolated from human gingival tissue (n = 10) were stimulated with substance P, anti-IgE or calcium ionophore A23187. Calcium ionophore significantly increased histamine release from HMC-1 cells and gingival mast cells (p < 0.05). This microassay will facilitate the study of mast cell histamine release in diseased oral mucosa.

Fluorescence quenching properties and chemiluminescence responses of alpha-ketothiols derivatized with o-phthalaldehyde and primary amino compounds

Fluorescence and chemiluminescence responses of thiols derivatized with o-phthalaldehyde (OPA) and primary amines have been studied. Among thiols tested, those having an alpha-ketothiol structure [R-CH(SH)-CO-] were found to give extremely low fluorescence intensities when derivatized with OPA and L-valine. The relative fluorescence intensities of alpha-ketothiols, such as mercaptoacetic acid (MAA), 2-mercaptopropionic acid (2-MPA), mercaptosuccinic acid (MSA) and N-(2-mercaptopropionyl)glycine (MPG), were only below 3% of that of N-acetyl-L-cysteine (NAC), having no alpha-ketothiol structure. The addition of detergents such as sodium dodecylsulphate had no effect on the fluorescence and an aprotic solvent (dimethylsulphoxide) showed little effect, whereas these thiols chemiluminesced intensely when derivatized with OPA and N-(4-aminobutyl)-N-ethylisoluminol as a primary amine and successively detected by high-performance liquid chromatography (HPLC) with postcolumn chemiluminescence reactions using hydrogen peroxide and haematin. The relative chemiluminescence intensities of MSA, 2-MPA and MPG to NAC were 41.0%, 27.8% and 117%, respectively. MPG was estimated to be detectable at a concentration level of at least 10 fmol per injection. In conclusion, the weak fluorescence of the alpha-ketothiols derivatized with OPA and primary amines is probably due to the low fluorescence quantum yields of the derivatives, and HPLC with a chemiluminescence detection system is useful for the sensitive detection of thiols.

New disinfection and sterilization methods

New disinfection methods include a persistent antimicrobial coating that can be applied to inanimate and animate objects (Surfacine), a high-level disinfectant with reduced exposure time (ortho-phthalaldehyde), and an antimicrobial agent that can be applied to animate and inanimate objects (superoxidized water). New sterilization methods include a chemical sterilization process for endoscopes that integrates cleaning (Endoclens), a rapid (4-hour) readout biological indicator for ethylene oxide sterilization (Attest), and a hydrogen peroxide plasma sterilizer that has a shorter cycle time and improved efficacy (Sterrad 50).

Guideline for the use of high-level disinfectants and sterilants for reprocessing of flexible gastrointestinal endoscopes

Glutaraldehyde, 0.2% peracetic acid, 7.5% hydrogen peroxide, 0.08% peracetic acid/1% hydrogen peroxide, and 0.55% ortho-phthalaldehyde are cleared by the FDA for reprocessing flexible gastrointestinal endoscopes. Each product has advantages and disadvantages. All require adherence to published reprocessing protocols in order to maintain the integrity of equipment while providing the public with endoscopic instruments that are safe and effective. All chemicals must be handled with respect. Selection of a product must be weighed against the needs of a particular setting, taking into consideration factors such as compatibility, toxicity, environmental controls and cost.

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.

On-line derivatization for continuous and automatic monitoring of brain extracellular glutamate levels in anesthetized rats: a microdialysis study

Glutamate is an important excitatory amino acid in central nervous system. We developed a method for in vivo, continuous and automatic monitoring of brain extracellular glutamate, as well as other amino acids in anesthetized rat. This method involves the use of microdialysis perfusion technique and a high-performance liquid chromatography system equipped with a fluorescence detector. The microdialysate (perfused at a flow-rate of 1 microl/min) was on-line derivatized with o-phthaldehyde (perfused at 2 microl/min) through a mixing tee prior to the injection onto the HPLC column. The efficiency of this on-line derivatization was equivalent to that performed with an off-line manner. The effect of cerebral ischemia (2 h) and reperfusion (2 h) in brain cortex of anesthetized rats was monitored using this method. In addition to glutamate, extracellular concentrations of other amino acids, such as aspartate, glutamine, glycine, taurine and gamma-aminobutyric acid, were also simultaneously monitored with this on-line method. Since monitoring of extracellular amino acids by microdialysis perfusion is intensively used in neuroscience investigations, this simple and convenient method would be useful in the future applications.

Analysis of glutathione and glutathione disulfide in whole cells and mitochondria by postcolumn derivatization high-performance liquid chromatography with ortho-phthalaldehyde

A method is described for the detection of glutathione (GSH) and glutathione disulfide (GSSG) based on a HPLC postcolumn reaction with ortho-phthalaldehyde (OPT) at pH 12 followed by fluorescence detection. Although similar methods have been reported, the high pH of the postcolumn reaction adds considerable selectivity and sensitivity to the measurement of GSH and glutathione disulfide. The limit of detection approaches 100 fmol, which is sufficient to detect whole-cell glutathione disulfide in 10,000 cells or mitochondrial glutathione disulfide in 20 million cells. Using this method, glutathione and glutathione disulfide were measured in human lymphocytes, granulocytes, and cultured Jurkat T cells, as well as in the corresponding samples of mitochondria. The percentage of glutathione disulfide to total glutathione in whole-cell extracts was approximately 1%. In contrast, the percentage was relatively high in mitochondria, with the mitochondria of granulocytes having the highest (25%) followed by those of lymphocytes (15%) and finally by cultured Jurkat T cells (9%). This method extends the analysis of glutathione and glutathione disulfide to mitochondria obtained from a relatively small number of cells.

Determination of S-nitrosoglutathione in human and rat plasma by high-performance liquid chromatography with fluorescence and ultraviolet absorbance detection after precolumn derivatization with o-phthalaldehyde

An analytical method is described for the quantification of S-nitrosoglutathione (GSNO), a potent physiological vasodilator and inhibitor of platelet aggregation, in the presence of a high excess of reduced glutathione (GSH). The method is based on the quantitative elimination of GSH by N-ethylmaleimide, the conversion of GSNO by 2-mercaptoethanol to GSH, its reaction with o-phthalaldehyde (OPA) to form a highly fluorescent and UV-absorbing tricyclic isoindole derivative, and subsequent high-performance liquid chromatographic (HPLC) separation with fluorescence and/or UV absorbance detection. The OPA derivatives of GSH and GSNO obtained by this method were found to be identical by mass spectrometry. GSH (up to 50 microM) did not interfere with the analysis of GSNO (up to 1000 nM). The limits of detection of the method for buffered aqueous solutions of GSNO were determined as 3 nM using fluorescence and 70 nM using UV absorbance detection. Isolation of GSNO by HPLC analysis (pH 7.0) of plasma ultrafiltrate samples (200 microl) prior to derivatization allows specific and artifact-free quantification of GSNO in human and rat plasma. Reduced and oxidized glutathione, nitrite, and cysteine did not interfere with the measurement of GSNO in human and rat plasma. The limit of quantitation (LOQ) of the combined method was determined as 100 nM of GSNO in human plasma ultrafiltrate using fluorescence detection. No endogenous GSNO could be detected in ultrafiltrate samples of plasma of 10 healthy humans at concentrations exceeding the LOQ of the method. After iv infusion of GSNO (125 micromol/kg body wt) in a rat for 20 min GSNO and GSH were detected in rat plasma at 60 and 130 microM, respectively. The method should be useful to investigate formation, metabolism, and reactions of GSNO in vitro and in vivo at physiologically relevant concentrations.

Rapid determination of aspartate enantiomers in tissue samples by microdialysis coupled on-line with capillary electrophoresis

Microdialysis was coupled on-line with derivatization by o-phthalaldehyde and beta-mercaptoethanol and optically gated capillary electrophoresis to determine D- and L-aspartate in tissue samples obtained from rats. The microdialysis probe was inserted into a homogenized tissue sample which allowed generation of a continuous sample stream that was filtered and deproteinated. With 7.5 mM beta-cyclodextrin (CD) in the electrophoresis buffer, the enantiomers of interest could be resolved in 3 s with an electric field of 2500 V/cm over a separation length of 15 mm. Values of D- and L-aspartate in different tissues agreed well with those obtained by an HPLC procedure that required protein precipitation, centrifugation, and extraction. The speed and compatibility with automation of the microdialysis/CE method may make it a general approach for a variety of applications involving high-throughput analysis or sensorlike operation.

Extracellular perfusion of rat brain nuclei using microdialysis: a method for studying differential neurotransmitter release in response to neurotoxins

Microdialysis probes, stereotactically placed in rat brain nuclei, allow detailed kinetic comparisons of neurotransmitter release from in situ chemical lesioning over a continuum from acute early changes (minutes) to chronic late changes (days). This technique insures a localized mechanism of action independent of systemic effects apparent with other routes of administration and independent of mechanical damage patterns encountered in conventional chemical lesioning. The example provided compares changes in extracellular gamma-aminobutyric acid (GABA) concentrations in the striatum in response to quinolinic acid (QA, 0.24 M) and 3-nitropropionic acid (3-NPA, 0.25 M). These examples of chemical lesioning represent two theoretical mechanisms of neurodeterioration in Huntington's disease, QA representing the excitotoxic component, and 3-NPA representing the impaired mitochondrial energy component [M.F. Beal, N.W. Kowall, D.W. Ellison, M.F. Mazurek, K.J. Swartz, J.M. Martin, Replication of the neurochemical characteristics of Huntington's disease by quinolinic acid, Nature 321 (1986) 168-171; M.F. Beal, E. Brouillet, B.G. Jenkins, R.J. Ferrante, N.W. Kowall, J.M. Miller, E. Storey, R. Srivastava, B.R. Rosen, B.T. Hyman, Neurochemical and histologic characterization of striatal excitotoxic lesions produced by the mitochondrial toxin 3-nitropropionic acid. J. Neurosci. 13 (1993) 4181-4192; N.C. Reynolds, W. Lin, C.M. Cameron, D.L. Roerig, Differential responses of extracellular GABA to intrastriatal perfusions of 3-nitropropionic acid and quinolinic acid in the rat, Brain Res. 778 (1997) 140-149]. An auxillary microdialysis probe implanted in the ipsilateral nucleus accumbens is used to define the physiologic extent of the cytotoxic lesion. Pre-column derivatization of perfusate fractions with o-phthalaldehyde/t-butylthiol (OPA) provides electroactivity to the OPA-GABA conjugate and facilitates electrochemical detection following high performance liquid chromatography [J.M. Peinado, K.T. McManus, R.B. Myers, Rapid method for microanalysis of endogenous amino acid neurotransmitters in brain perfusates in the rat by isocratic HPLC-EC, J. Neurosci. Methods 18 (1986) 269-276].

An experimental design approach to the optimisation of a flow injection analysis method for glycine

A flow injection analysis method for the determination of glycine, based on the reaction with ortho-phtalaldehyde and N-acetylcysteine in a basic buffer, was optimised. In the first step screening of the variables, to select the most important ones, was performed using: (i) a half-fraction factorial design and (ii) a quarter-fraction factorial design, for five factors at two levels. The effects of the factors on the peak height were calculated from both screening designs and compared. For the half-fraction factorial design (resolution IV), the significance of the factor effects on the peak height was checked by: (i) comparing them with a critical effect, calculated from two-factor interactions and based on a t-test, (ii) using a non parametric approach and (iii) drawing a normal probability plot. For the quarter-fraction factorial design (resolution III) the significance of the effects of the factors on the peak height was checked using: (i) a randomization test method, (ii) the non parametric method and (iii) a normal probability plot. In the second step, the factor found to be of importance was optimised using the uniplex method.

Simultaneous measurement of foliar glutathione, gamma-glutamylcysteine, and amino acids by high-performance liquid chromatography: comparison with two other assay methods for glutathione

The recent production of transformed plants with enhanced capacity for glutathione synthesis has highlighted the interactions between foliar glutathione and turnover of free amino acid pools. The development of a convenient method for simultaneous measurement of glutathione, gamma-glutamylcysteine, and 16 amino acids is reported. This method utilizes derivatization of compounds with o-phthalaldehyde in the presence of 2-mercaptoethanol followed by separation using reversed-phase high-performance liquid chromatography. Eluted compounds are detected fluorimetrically. The method was tested using untransformed poplars and poplars in which foliar thiol contents have been enhanced by overexpression of gamma-glutamylcysteine synthetase. Foliar contents of glutathione determined by this method were comparable to those measured in common extracts by two other techniques.

The subcellular distribution of histamine, slow-reacting substance and 5-hydroxytryptamine in the brain of the rat

Various extracts of brain were prepared with dilute and concentrated acid, acetone and n-butanol. When the extracts were applied to the guinea-pig isolated ileum, they produced a slow contraction which was not prevented by an antihistamine; in addition, the acid and acetone extracts inhibited the action of histamine. Histamine in extracts of brain was separated from other pharmacologically active substances by chromatography on a carboxylic-acid resin and estimated biologically. The bulk of this histamine was found in small particulate material, whereas slow-reacting substance was found in particulate material of greater density. 5-Hydroxytryptamine was in both the small and large particles. There was no relationship between the distribution of these substances and that of succinic dehydrogenase activity. The measurement of histamine in brain both by biological assay on the guinea-pig ileum and by chemical assay using a fluorimetric procedure gave mean values of 53 and 246 ng/g of wet tissue, respectively. The high values obtained by the chemical assay are attributable in part to substances other than histamine which become fluorescent after reaction with o-phthalaldehyde in this procedure.