The application of fluorescein isothiocyanate and high-performance liquid chromatography for the microsequencing of proteins and peptides

Contributions of Extracellular Vesicles to Fungal Biofilm Pathogenesis

Extracellular vesicles (EVs) are produced by all kingdoms of life and have been increasingly recognized as a key aspect of microbial pathogenicity. These membrane-bound compartments serve as secretory vehicles for the delivery of macromolecules to the extracellular environment. Studies over the past several decades have revealed that microbial EVs are highly suited to the biology and environmental context of the organism secreting them. Fungal EVs have been described in at least 12 species and have diverse functions. These functions include, but are not limited to, molecular transport across the cell wall, immunomodulation, cell-cell communication, export of virulence factors and nucleic acids, extracellular matrix (ECM) production, and induction of drug resistance. This chapter will explore the contributions of EVs to fungal pathogenesis and virulence, with a detailed focus on the role of C. albicans biofilm EVs in matrix biogenesis and antifungal resistance. Brief commentary on EV function in bacterial biofilms will also be provided for comparison, and suggestions for areas of future investigation in this field will be discussed.

Circularly polarized luminescence reveals interaction between commercial stains and protein matrices used in paintings

Here we show that circularly polarized luminescence (CPL) can give unique insight into interactions between fluorescent commercial stains and protein-based materials used in painting. CPL can complement information from ECD and fluorescence.

Analysis of amino acid composition in proteins of animal tissues and foods as pre-column o-phthaldialdehyde derivatives by HPLC with fluorescence detection

Studies of protein nutrition and biochemistry require reliable methods for analysis of amino acid (AA) composition in polypeptides of animal tissues and foods. Proteins are hydrolyzed by 6M HCl (110°C for 24h), 4.2M NaOH (105°C for 20 h), or proteases. Analytical techniques that require high-performance liquid chromatography (HPLC) include pre-column derivatization with 4-chloro-7-nitrobenzofurazan, 9-fluorenyl methylchloroformate, phenylisothiocyanate, naphthalene-2,3-dicarboxaldehyde, 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate, and o-phthaldialdehyde (OPA). OPA reacts with primary AA (except cysteine or cystine) in the presence of 2-mercaptoethanol or 3-mercaptopropionic acid to form a highly fluorescent adduct. OPA also reacts with 4-amino-1-butanol and 4-aminobutane-1,3-diol produced from oxidation of proline and 4-hydroxyproline, respectively, in the presence of chloramine-T plus sodium borohydride at 60°C, or with S-carboxymethyl-cysteine formed from cysteine and iodoacetic acid at 25°C. Fluorescence of OPA derivatives is monitored at excitation and emission wavelengths of 340 and 455 nm, respectively. Detection limits are 50 fmol for AA. This technique offers the following advantages: simple procedures for preparation of samples, reagents, and mobile-phase solutions; rapid pre-column formation of OPA-AA derivatives and their efficient separation at room temperature (e.g., 20-25°C); high sensitivity of detection; easy automation on the HPLC apparatus; few interfering side reactions; a stable chromatography baseline for accurate integration of peak areas; and rapid regeneration of guard and analytical columns. Thus, the OPA method provides a useful tool to determine AA composition in proteins of animal tissues (e.g., skeletal muscle, liver, intestine, placenta, brain, and body homogenates) and foods (e.g., milk, corn grain, meat, and soybean meal).

Different in vitro toxicity of ribosome-inactivating proteins (RIPs) on sensory neurons and Schwann cells

OBJECTIVE

To study the neurotoxicity induced by Ricinus communis agglutinin (RCA), ricin A chain (RTA), and trichosanthin (TCS) in vitro.

METHODS

Rat neurons and Schwann cells were cultured and real-time up-take of RIPs was traced. TUNEL, Annexin V and DAPI were employed to study the mechanism.

RESULTS

The purity of both primary neuronal and Schwann cell cultures attained 80-90%. In neuritis, transport of FITC-RCA was demonstrated, but RTA and TCS were not detected. RCA elicited the strongest TUNEL and annexin V signals in both cultures. RTA evoked a stronger apoptotic signal than TCS in neurons. In contrast, compared with TCS, RTA elicited an attenuated apoptotic reaction in Schwann cells. All internalized RIPs were concentrated in the cytoplasm of the cells and their nuclei were not stained by DAPI.

CONCLUSION

The toxicity of these RIPs on neurons is different from that on Schwann cells. Although they enter cells by different mechanisms they all induce apoptosis. These results may find application in in vivo neural lesioning studies and clinical therapy.

Highly sensitive and selective derivatization-LC method for biomolecules based on fluorescence interactions and fluorous separations

A fluorescence derivatization LC method is a powerful tool for the analysis with high sensitivity and selectivity of biological compounds. In this review, we introduce new types of fluorescence derivatization LC analysis methods. These are (1) detection-selective derivatization methods based on fluorescence interactions generated from fluorescently labeled analytes: excimer fluorescence derivatization and fluorescence resonance energy transfer (FRET) derivatization; (2) separation-selective derivatization methods using the fluorous separation technique: fluorous derivatization, F-trap fluorescence derivatization, and fluorous scavenging derivatization (FSD).

Mechanism of the specific neuronal toxicity of a type I ribosome-inactivating protein, trichosanthin

The aim was to study the mechanism of neuronal toxicity, the cellular pathway, and the glial cell reactions induced by trichosanthin (TCS), a type I ribosome-inactivating protein (RIP). Ricin A chain (RTA) was included for comparison. TCS, RTA, and fluorescein isothiocyanate (FITC)-labeled TCS and RTA were separately injected into rat eyes. Saline or pure FITC was used as the control. Electron microscopy, confocal microscopy, and lectin and immunohistochemical staining were used to study the neurotoxic mechanism. TCS mainly induced apoptosis by causing degeneration of the mitochondria. TCS was able to enter the Müller and pigment cells. It caused a change in cell number of the following types of glial cells: a decrease in Müller cells, an increase in astrocytes, and little change in microglia. In contrast, RTA mainly induced necrosis and entered vascular endothelial cells. Astrocyte and microglia reactions were stronger in the RTA-treated retinas than those in the TCS-treated retinas. In conclusion, TCS appears to selectively enter and destroy Müller and pigment epithelia cells, which subsequently induce the death of photoreceptors. Degeneration of mitochondria is involved in the pathways of apoptosis of the photoreceptors caused by TCS. In sharp contrast, RTA can enter vascular endothelial cells and damage the vascular endothelium, resulting in retinitis and necrosis.

Selective Determination of Tryptophan-containing Peptides through Precolumn Derivatization and Liquid Chromatography Using Intramolecular Fluorescence Resonance Energy Transfer Detection

A selective and sensitive fluorometric determination method for native fluorescent peptides has been developed. This method is based on intramolecular fluorescence resonance energy transfer (FRET) detection in a liquid chromatography (LC) system following precolumn derivatization of the amino groups of tryptophan (Trp)-containing peptides. In this detection process, we monitored the FRET from the native fluorescent Trp moieties (donor) to the derivatized fluorophore (acceptor). From a screening study involving 10 fluorescent reagents, we found that o-phthalaldehyde (OPA) generated FRET most effectively. The OPA derivatives of the native fluorescent peptides emitted OPA fluorescence (445 nm) through an intramolecular FRET process when they were excited at the excitation maximum wavelength of the Trp-containing peptides (280 nm). The generation of FRET was confirmed through comparison with the analysis of a non-fluorescent peptide (C-reactive protein fragment (77 - 82)) performed using LC and a three-dimensional fluorescence detection system. We were able to separate the OPA derivatives of the Trp-containing peptides when performing LC on a reversed-phase column. The detection limits (signal-to-noise ratio = 3) for the Trp-containing peptides, at a 20-microL injection volume, were 41 - 180 fmol. The sensitivity of the intramolecular FRET-forming derivatization method is higher than that of the system that takes advantage of the conventional detection of OPA derivatives. Moreover, native non-fluorescent amines and peptides in the sample monitored at FRET detection are weaker than those of conventional fluorescence detection.

Development of an HPLC-fluorescence determination method for carboxylic acids related to the tricarboxylic acid cycle as a metabolome tool

We report the simultaneous determination of the carboxylic acids related to the tricarboxylic acid (TCA) cycle, which plays an important role in producing adenosine triphosphate (ATP) and generating energy in mitochondria. Seven carboxylic acids from the TCA cycle, and pyruvic acid and 2-methylsuccinic acid, as an internal standard, were derivatized with a fluorescent reagent for carboxyl groups, 4-N,N-dimethylaminosulfonyl-7-piperazino-2,1,3-benzoxadiazole (DBD-PZ), in the presence of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and 4-N,N-dimethyaminopyridine as the coupling reagents, at 60 degrees C for 120 min. Subsequently, the excess DBD-PZ was removed efficiently using a cation-exchange cartridge, SDB-RPS (Empore). These fluorescent derivatives were separated well from each other on an octadecyl silica column (TSKgel ODS-80Ts, 250 x 4.6 mm, i.d.) with an eluent of acetonitrile-water containing 1% formic acid at a flow rate of 0.8 mL/min, and were detected fluorometrically at 560 nm, with excitation at 450 nm. The validation data were satisfactory in the range of 2.5-100 microm citric acid, isocitric acid, 2-oxoglutaric acid, succinic acid and fumaric acid. The detection limit (S/N = 3) for citric acid was 2 fmol on the column. The structures of these derivatives were confirmed by high-performance liquid chromatography-mass spectrometry, which proved that their carboxylic groups were completely labeled with DBD-PZ, except for oxaloacetic acid. This HPLC method was successfully applied to the analysis of TCA cycle metabolites in rat urine. The method will also be useful for metabolome research, such as for target analyses of metabolites with carboxyl groups, not only in urine but also in cells and organs.

Selective Determination of Native Fluorescent Bioamines through Precolumn Derivatization and Liquid Chromatography Using Intramolecular Fluorescence Resonance Energy Transfer Detection

In this paper, we introduce a novel approach for the highly selective and sensitive analysis of native fluorescent bioamines (indoleamines and catecholamines). This method is based on intramolecular fluorescence resonance energy transfer (FRET) detection in a liquid chromatography (LC) system following precolumn derivatization of the bioamines' amino groups. In this detection process, we monitored the FRET from the native fluorescent moieties (donor) to the derivatized fluorophore (acceptor). From a screening study involving 15 fluorescent reagents, we found that o-phthalaldehyde (OPA) generated the FRET most effectively. The OPA derivatives of the native fluorescent bioamines emitted OPA fluorescence (445 nm) through an intermolecular FRET process when they were excited at the excitation maximum wavelengths of the native fluorescent bioamines (280 nm). The generation of FRET was confirmed through comparison with the analysis of a nonfluorescent amine (isoleucine) performed using LC and a three-dimensional fluorescence detection system. We were able to separate the OPA derivatives of the indoleamines and catecholamines when performing LC on an ODS column. The detection limits (signal-to-noise ratio, 3) for the indoleamines and catecholamines, at a 20-muL injection volume, were 17-120 and 28-200 fmol, respectively. The sensitivity of the intramolecular FRET-forming derivatization method is higher than those of systems that take advantage of both native fluorescence detection (i.e., without derivatization) and the conventional detection of OPA derivatives. Furthermore, this method provides enough selectivity and sensitivity for the determination of the indoleamines present in the urine of healthy humans.

Amino acid analysis by micellar electrokinetic chromatography with laser-induced fluorescence detection: application to nanolitre-volume biological samples from Arabidopsis thaliana and Myzus persicae

Amino acids were derivatised with 4-fluoro-7-nitrobenzo-2,1,3-oxadiazol (NBD-F), separated by micellar electrokinetic chromatography (MEKC), and detected by argon-ion (488 nm) laser-induced fluorescence. The optimised MEKC background electrolyte conditions were: 40 mM sodium cholate, 5 mM beta-cyclodextrin in 20 mM aqueous borate buffer, pH 9.1, with 7% v/v acetonitrile. Using these conditions, 19 amino acids were separated within 17 min. The limits of detection were in the range of 7.6-42.2 pmol/mL and limits of quantitation from 0.05-0.14 nmol/mL. The method was systematically validated for injection volume error, migration time variation, calibration linearity, accuracy, precision, and recovery. Nanolitre volume samples of phloem sap of individual sieve element cells from the plant Arabidopsis thaliana and honeydew from the aphid Myzus persicae were directly analysed with this method. Quantitative amino acid concentrations in these two biological matrices were profiled for the first time. This method is particularly important because it allows the complete profile of the amino acids obtained from individual phloem elements, allowing cell to cell and plant to plant variation to be quantified, which to date has not been possible with Arabidopsis thaliana.

Determination of peptides and amino acids from wool and beer with sensitive fluorescent reagent 2-(9-carbazole)-ethyl chloroformate by reverse phase high-performance liquid chromotography and liquid chromotography mass spectrometry

A new method for the sensitive determination of amino acids and peptides using the tagging reagent 2-(9-carbazole)-ethyl chloroformate (CEOC) with fluorescence (FL) detection has been developed. Identification of derivatives was carried out by liquid chromotography mass spectrometry. The chromophore in the 2-(9-fluorenyl)-ethyl chloroformate (FMOC) reagent was replaced by carbazole, which resulted in a sensitive fluorescence lerivatizing agent CEOC. CEOC can easily and quickly label peptides and amino acids. Derivatives are stable enough to be efficiently analyzed by high-performance liquid chromatography. Studies on derivatization demonstrate excellent derivative yields over the pH range 8.8-10.0. Maximal yields close to 100% are observed with three- to fourfold molar reagent excess. Derivatives exhibit strong fluorescence and allow direct injection of the reaction mixture with no significant disturbance from the major fluorescent reagent degradation by-products, such as 2-(9-carbazole)-ethanol and bis-(2-(9-carbazole)-ethyl) carbonate. In addition, the detection responses for CEOC derivatives are compared to those obtained with FMOC. The ratios AC(CEOC)/AC(FMOC) = 1.00-1.82 for fluorescence (FL) response and AC'(CEOC)/AC'(FMOC) = 1.00-1.21 for ultraviolet (UV) response are observed (here, AC and AC' are, respectively, FL and UV response). Separation of the derivatized peptides and amino acids has been optimized on a Hypersil BDS C18 column. Excellent linear responses are observed. This method was used successfully to analyze protein hydrolysates from wool and from direct-derivatized beer.

Amino acid sequence and D/L-configuration determination methods for D-amino acid-containing peptides in living organisms

D-amino acid-containing peptides with biological activities have been isolated from invertebrates and amphibians, and partial racemization of amino acid residues in mammalian peptides associated with aging and diseases have been discussed. Here, we review the amino acid configuration determination methods in these peptides and recent progress of simultaneous determination method for sequence and configuration of amino acid residues. The applicability of C-terminus sequence analysis and mass spectrometry to configuration determination of amino acids is also discussed.

Development of an amino acid sequence and D/L-configuration determination method of peptide with a new fluorescence Edman reagent, 7-methylthio-4-(2,1,3-benzoxadiazolyl) isothiocyanate

On the basis of the relationship between the fluorescence characteristics of the benzofurazan compounds and the Hammett constants (sigma p), a new fluorescence Edman reagent, 7-methylthio-4-(2,1,3-benzoxadiazolyl) isothiocyanate (MTBD-NCS) was designed and synthesized. MTBD-thiohydantoin (TH)-amino acid derivatives produced by the Edman sequencing method gave fluorescence, whereas other degradation byproducts such as MTBD-thiocarbamoyl (TC)- or carbamoyl (CA)-amino acids did not fluoresce. MTBD-NCS was applicable as an Edman sequencing reagent to the simultaneous determination of both the sequence and D/L-configuration of amino acids in peptides. Boron trifluoride (BF3) and HC1/methanol were adopted as the cyclization/cleavage and conversion reagents to suppress the amino acid residue racemization. The MTBD-TH-amino acids were separated on a reversed-phase column for amino acid sequencing, and their enantiomers were resolved on two types of polysaccharide-based chiral stationary phases for D/L-configuration determination. The method was successfully applied to the sequence and D/L-configuration determination of D-amino acid-containing peptide [D-Ala2]-deltorphin II.

Detection of DBD-carbamoyl amino acids in amino acid sequence and D/L configuration determination of peptides with fluorogenic Edman reagent 7-[(N,N-dimethylamino)sulfonyl]-2,1,3-benzoxadiazol-4-yl isothiocyanate

A method for amino acid sequence and D/L configuration identification of peptides by using fluorogenic Edman reagent 7-[(N, N-dimethylamino)sulfonyl]-2,1,3-benzoxadiazol-4-yl isothiocyanate (DBD-NCS) has been developed. This method was based on the Edman degradation principle with some modifications. A peptide or protein was coupled with DBD-NCS under basic conditions and then cyclized/cleaved to produce DBD-thiazolinone (TZ) derivative by BF3, a Lewis acid, which could significantly suppress the amino acid racemization. The liberated DBD-TZ amino acid was hydrolyzed to DBD-thiocarbamoyl (TC) amino acid under a weakly acidic condition and then oxidized by NaNO2/H+ to DBD-carbamoyl (CA) amino acid which was a stable and had a strong fluorescence intensity. The individual DBD-CA amino acids were separated on a reversed-phase high-performance liquid chromatography (RP-HPLC) for amino acid sequencing and their enantiomers were resolved on a chiral stationary-phase HPLC for identifying their D/L configurations. Combination of the two HPLC systems, the amino acid sequence and D/L configuration of peptides could be determined. This method will be useful for searching D-amino-acid-containing peptides in animals.

Determination of dimethylamine and other low-molecular-mass amines using capillary electrophoresis with laser-induced fluorescence detection

The potential of capillary electrophoresis (CE) with laser-induced fluorescence (LIF) detection for the separation and determination of dimethylamine (DMA) and other low-molecular-mass amines involving precolumn derivatization with fluorescein isothiocyanate isomer I (FITC) was investigated. Different variables that affect derivatization (pH, FITC concentration, reaction time and temperature) and separation (buffer concentration, addition of various organic modifiers, applied voltage and length of capillary) were studied. The linearity, reproducibility and reliability of the method were evaluated. The estimated instrumental detection limit for a 2-s pressure injection of the FITC-DMA derivative was 50 pg/ml (10(-9) M), using LIF detection with excitation and emission wavelengths of 488 nm and 520 nm, respectively. However, for practical reasons, a minimum of 5 ng/ml DMA should be subjected to the derivatization. The applicability of the described method to the extract of atmospheric aerosol samples was demonstrated.

A novel technique for visualizing the intracellular localization and distribution of transported polyamines in cultured pulmonary artery smooth muscle cells

The use of a combination of monofluorescein adducts of spermidine (FL-SPD) and spermine (FL-SPM) with confocal laser scanning microscopy (CLSM) provides a useful means for monitoring the fate and time-dependent changes in the distribution of transported polyamines within living cells. Polyamine-fluorescein adducts were synthesized from fluorescein isothiocyanate and the appropriate polyamine. Monofluorescein polyamine adducts (ratio 1:1) were isolated using thin layer chromatography, and the structure and molecular weight of the monofluorescein polyamine adducts were confirmed using NMR and mass spectroscopy, respectively. The covalent linkage of the fluorescent adduct moiety to SPD and SPM did not influence their rate of uptake by bovine pulmonary artery smooth muscle cells (PASMC). Similar to 14C-SPD and 14C-SPM, the rate of uptake of 14C-FL-SPD and 14C-FL-SPM in PASMC was temperature-dependent. Treatment for 24 h with difluoromethylornithine (DFMO), a selective blocker of the enzyme ornithine decarboxylase and an inducer of the polyamine transport system, significantly increased the cellular uptake of 14C-FL-SPD and 14C-FL-SPM compared to that of control cells. When compared to control cells, treatment of PASMC with the pyrrolizidine alkaloid monocrotaline for 24 h also significantly increased the cellular uptake of 14C-FL-SPD and 14C-FL-SPM. On the other hand, 24 h treatment of PASMC with a polymer of SPM, a selective blocker of the polyamine transport system, or with free spermine, markedly reduced the cellular accumulation of 14C-FL-SPD and 14C-FL-SPM. After a 20-min treatment of PASMC with FL-SPD or FL-SPM, CLSM revealed that adduct fluorescence was localized in the cytoplasm of living cells. Treatment with DFMO increased the cytoplasmic accumulation of both FL-SPD and FL-SPM. In addition, the fluorescence observed in the cytoplasm of chinese hamster ovary cells (CHO) was significantly higher than that detected in the cytoplasm of their polyamine transport deficient variants (CHOMGBG). The results of this study provide the first evidence of the utility of a novel method for visualizing the uptake, distribution, and cellular localization of transported polyamines in viable cultured mammalian cells.

Sensitive determination of N-terminal prolyl peptides by high-performance liquid chromatography with laser-induced fluorescence detection

Short-chain peptides with an N-terminal proline (Pro-Gly, Pro-Ile, Pro-Gly-Gly, Pro-Leu-Gly-NH2, and Pro-Thr-Pro-Ser-NH2, etc.) were determined by HPLC with laser-induced fluorescence (LIF) detection. The peptides were quantitatively labelled with 4-(N,N-dimethylaminosulphonyl)-7-fluoro-2,1,3-benzoxadiazole (DBD-F) at 50 degrees C after 1 h in a 0.1 M borax (pH 9.3)-acetonitrile mixture. The rate of reaction decreases inversely with the molecular weight of the peptides. The mean value of fluorescent emission of the resulting DBD-peptides and DBD-peptide amides was 573 nm (excitation, 453 nm). The proline peptides, including bioactive peptides such as Pro-Leu-Gly-NH2 (release inhibitor of melanocyte-stimulating hormone), Pro-Thr-Pro-Ser-NH2 (IgA1 proteinase inhibitor) and Pro-Asp-Val-Asp-His-Val- Phe-Leu-Arg-Phe-NH2 [FMRF amide-like (Phe-Met-Arg-Phe-NH2) neuropeptide], were well separated by reversed-phase HPLC with water-acetonitrile containing 0.1% trifluoroacetic acid (TFA). The acetonitrile concentration in the mobile phase had a profound effect upon the retention times, and the capacity factors (k') were dependent on the hydrophobicity of the peptides. The structure of DBD-Pro-Leu-Gly-NH2 was identified by LC-atmospheric pressure chemical ionization MS. The chromatographic detection limits (S/N = 2) of the peptides with a 15-mW argon-ion laser at 488 nm were in the 6-28 fmol range. The detection limits were improved to 2-5 fmol with a microbore column. The detectability was two orders of magnitude higher than with a conventional fluorescence detector using xenon arc lamp.

The amino-acid sequence of a lectin from conger eel, Conger myriaster, skin mucus

The amino-acid sequence of a beta-galactoside-binding lectin isolated from the skin mucus of the conger eel Conger myriaster was determined. The lectin (30 kDa) was composed of two identical subunits of 135 amino acid residues with N-acetylserine at the N-terminus and no half-cystinyl residue. It was a 30-34% sequence identical to vertebrate beta-galactoside-binding lectin and proved to be a member of the S-type lectin family.

Capillary zone electrophoresis separation and laser-based detection of both fluorescein thiohydantoin and dimethylaminoazobenzene thiohydantoin derivatives of amino acids

Capillary zone electrophoresis is employed for the separation and analysis of both fluorescein thiohydantoin and dimethylaminoazobenzene thiohydantoin derivatives of amino acids. Detection of minute amounts of these amino acid derivatives is an important milestone in the development of a high sensitivity protein sequencer. Current detection limits for the fluorescein derivative is on the order of 10(-21) moles whereas detection limits for the dimethylaminoazobenzene derivative is on the order of 10(-16) moles.

The amino-acid sequence of multiple lectins of the acorn barnacle Megabalanus rosa and its homology with animal lectins

The amino-acid sequence of a lectin isolated from the coelomic fluid of the acorn barnacle Megabalanus rosa has been determined. The lectin (Mr 140,000) is a multimeric protein whose subunit consists of 173 amino acids and one carbohydrate chain attached to Asn-39. The amino-acid sequence was determined by the manual sequencing of peptides derived from the protein by digestion with Staphylococcus aureus V8 proteinase, lysine endopeptidase and chymotrypsin, as well as fragments produced by cleavage with cyanogen bromide. The amino-acid sequence of the lectin was compared with the sequence of one (Mr 64,000) of the multiple lectins of M. rosa. They are distinct molecules in spite of a significant homology in their amino-acid sequences. The amino-acid sequence includes some regions homologous to those in other invertebrate lectins, such as sea urchin and flesh fly lectins, and vertebrate lectins. This is the first report to show the amino-acid sequence of multiple lectins isolated from an invertebrate.

High-sensitivity fluorescence detector fluorescein isothiocyanate derivatives of amino acids separated by capillary zone electrophoresis

A fluorescence detector has been developed for capillary zone electrophoresis that produces a ten-fold improvement in precision compared with the previous state-of-the-art in fluorescence detection. This instrument, which is based on a sheath-flow cuvette flow chamber and a 0.05-W argon ion laser beam, combines a high numerical aperture collection optic, N.A = 0.65, with a high quantum yield photomultiplier tube, phi approximately = 0.15 at the wavelength of maximum emission. Detection limits (3 sigma) range from the injection of 1.7 . 10(-21) mol (1.3 . 10(-12) M) of fluorescein isothiocyanate (FITC)-labeled arginine, the best case, to 6 . 10(-21) mol (5.6 . 10(-12) M) of FITC-cysteine, the worse case. Signal linearity extends for at least five orders of magnitude from the detection limit to greater than 10(-16) mol (10(-7) M) injected.

Subattomole amino acid analysis by capillary zone electrophoresis and laser-induced fluorescence

Subattomole analysis of fluorescein isothiocyanate (FITC) derivatives of amino acids is accomplished by combining capillary zone electrophoresis for high-efficiency separation with laser-induced fluorescence for high-sensitivity detection. Concentration detection limits range from 5 x 10(-12) molar for alanine to 9 x 10(-11) molar for lysine, injected in the column; 9 x 10(-21) mole of alanine is contained within the approximately 1-nanoliter injection volume at the detection limit. The alanine detection limit corresponds to fewer than 6000 molecules injected onto the column and represents an improvement of four orders of magnitude in the state of the art for fluorescent detection of amino acids and an improvement of six orders of magnitude in the state of the art for the detection limit for isothiocyanate derivatives of amino acids.

Purification, amino terminal analysis, and peptide mapping of proteins after in situ postelectrophoretic fluorescent labeling

Proteins fractionated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis were stained in situ with either 5-(dimethylamino)-1-naphthalene sulfonyl chloride (dansyl chloride) or fluorescein isothiocyanate. This staining procedure can be carried out in less than 30 min without previous fixation of the proteins. It is not dependent on such factors as charge or molecular weight of the proteins and can detect 50 ng of protein in a 10-mm-wide gel slot. Fluorescent staining with dansyl chloride was used to localize proteins after electrophoresis for subsequent electroelution, amino terminal analysis, and peptide mapping. The electroelution can be carried out in less than 3 h with yields approaching 100%. The staining of only one strip of a preparative gel allowed the electroelution of proteins without covalent modification. For amino terminal analysis, identical results were obtained when the hydrolysis step was carried out after electroelution or directly in the gel pieces. The peptide mapping can be carried out with the proteins in solution (after electroelution) or directly in the gel pieces. The amino terminal and peptide mapping analysis of each protein in a mixture can be completed within 30 h from the beginning of the electrophoretic fractionation. The method appears to be applicable to a wide range of proteins showing very different biochemical properties.

Analysis of reducing sugars as their chromophoric hydrazones by high-performance liquid chromatography

A chromophoric hydrazide, 4'-N,N-dimethylamino-4-azobenzene sulfonyl hydrazide (DABS-hydrazide), was prepared from 4'-N,N-dimethylamino-4-azobenzene sulfonyl chloride by reaction with hydrazine. Reducing sugars were derivatized with DABS-hydrazide at 50 degrees C for 120 min. The chromophoric hydrazones were separated by reversed-phase HPLC isocratically using a short column (4.6 X 50 mm) and 0.08 M acetic acid-acetone as an eluant with no sample pretreatment and were quantitated at the picomole level. This method was applied to the sugar analysis of 5 micrograms of glycoproteins. Dansyl hydrazide derivatives of sugars were also separated by this HPLC system.

Amino acid sequence of two sea anemone toxins from Anthopleura fuscoviridis

The amino acid sequences of two toxins, AFT-I and AFT-II, from the sea anemone Anthopleura fuscoviridis were determined. AFT-I and -II consist of 47 and 48 amino acid residues, respectively, and are cross-linked with three disulfide bridges. The sequences have high homology to those of toxins I and II from Anemonia sulcata and anthopleurin-A and -B from Anthopleura xanthogrammica.

Micro-scale sequence analysis from the N-terminus of peptides using the fluorogenic Edman reagent 4-N,N-dimethylamino-1-naphthyl isothiocyanate

The fluorogenic Edman reagent 4-N,N-dimethylamino-1-naphthyl isothiocyanate (DNTC) was reacted with amino acids and peptides, cyclized by acid and the liberated 4-N,N-dimethylamino-1-naphthyl thiohydantoin (DNTH) amino acids were then separated and detected by HPLC. The fluorescence intensities of DNTH-amino acids except DNTH-proline and -serine were dramatically increased in the alkaline solution and organic solvent. Thus, the postcolumn reaction with alkaline acetonitrile solution was adopted in HPLC. The polar and aromatic amino acids afforded two DNTH-amino acids on derivatization with DNTC and cyclization with acids. These were suggested to be stereoisomers of DNTH-amino acids. The sequence analysis of 0.5 nmol Leu-enkephalin was achieved by the double coupling method with DNTC and phenyl isothiocyanate followed by the proposed HPLC system.

A new sensitive Edman-type reagent: 4-(N-1-dimethylaminonaphthalene-5-sulfonylamino)phenyl isothiocyanate. Its synthesis and application for micro-sequencing of polypeptides

A new fluorescent PITC homologue Edman-type reagent, 4-(N-1-dimethylaminonaphthalene-5-sulfonylamino)phenyl isothiocyanate (DNSAPITC), was synthesized following a simple three-step synthetic route. The reagent was crystallized and characterized by thin-layer chromatography, IR and electron impact mass spectrometry. Reference DNSAPTH-amino acid derivatives were prepared and a two-dimensional chromatography system on micro-polyamide sheets was developed for separating this mixture. On these sheets the sensitivity was 1-5 pmol, by exposure at 366 nm. Model peptides and proteins were subjected to Edman degradations with this new reagent. A similar coupling efficiency and repetitive degradation yield to those of PITC were found with this reagent. The advantages and limitations of this reagent for sensitive microsequencing are discussed.