Purification and Characterization of Plantaricin JLA-9: A Novel Bacteriocin against Bacillus spp. Produced by Lactobacillus plantarum JLA-9 from Suan-Tsai, a Traditional Chinese Fermented Cabbage

Bacteriocins are ribosomally synthesized peptides with antimicrobial activity produced by numerous bacteria. A novel bacteriocin-producing strain, Lactobacillus plantarum JLA-9, isolated from Suan-Tsai, a traditional Chinese fermented cabbage, was screened and identified by its physiobiochemical characteristics and 16S rDNA sequence analysis. A new bacteriocin, designated plantaricin JLA-9, was purified using butanol extraction, gel filtration, and reverse-phase high-performance liquid chromatography. The molecular mass of plantaricin JLA-9 was shown to be 1044 Da by MALDI-TOF-MS analyses. The amino acid sequence of plantaricin JLA-9 was predicted to be FWQKMSFA by MALDI-TOF-MS/MS, which was confirmed by Edman degradation. This bacteriocin exhibited broad-spectrum antibacterial activity against Gram-positive and Gram-negative bacteria, especially Bacillus spp., high thermal stability (20 min, 121 °C), and narrow pH stability (pH 2.0-7.0). It was sensitive to α-chymotrypsin, pepsin, alkaline protease, and papain. The mode of action of this bacteriocin responsible for outgrowth inhibition of Bacillus cereus spores was studied. Plantaricin JLA-9 had no detectable effects on germination initiation over 1 h on monitoring the hydration, heat resistance, and 2,6-pyridinedicarboxylic acid (DPA) release of spores. Rather, germination initiation is a prerequisite for the action of plantaricin JLA-9. Plantaricin JLA-9 inhibited growth by preventing the establishment of oxidative metabolism and disrupting membrane integrity in germinating spores within 2 h. The results suggest that plantaricin JLA-9 has potential applications in the control of Bacillus spp. in the food industry.

Fluorescence and co-fluorescence of Tb(3+) and Eu(3+) in acetonitrile using 2,6-pyridine dicarboxylic acid as ligand

Fluorescence from Tb(3+) and Eu(3+) complexed with 2,6-pyridine dicarboxylic acid (PDA) has been studied using acetonitrile (MeCN) as solvent. The enhancement in fluorescence intensity because of non-aqueous environment provided by the MeCN is less significant, where as fluorescence enhancement of more than two orders of magnitude has been observed with the addition of La(3+); a process known as co-fluorescence in MeCN. The present study demonstrates for the first time co-fluorescence of Tb(3+) and Eu(3+) with excitation through the absorption of PDA. Intermolecular energy transfer is believed to be responsible for co-fluorescence enhancement and it becomes possible as the quenching due to water at the secondary coordination spheres of Tb(3+) and Eu(3+) is reduced when MeCN is used as solvent.

A low molecular weight zinc2+-dipicolylamine-based probe detects apoptosis during tumour treatment better than an annexin V-based probe

OBJECTIVES

Molecular imaging of apoptosis is frequently discussed for monitoring cancer therapies. Here, we compare the low molecular weight phosphatidylserine-targeting ligand zinc2+-dipicolylamine (Zn2+-DPA) with the established but reasonably larger protein annexin V.

METHODS

Molecular apoptosis imaging with the fluorescently labelled probes annexin V (750 nm, 36 kDa) and Zn2+-DPA (794 nm, 1.84 kDa) was performed in tumour-bearing mice (A431). Three animal groups were investigated: untreated controls and treated tumours after 1 or 4 days of anti-angiogenic therapy (SU11248). Additionally, μPET with 18 F-FDG was performed. Imaging data were displayed as tumour-to-muscle ratio (TMR) and validated by quantitative immunohistochemistry.

RESULTS

Compared with untreated control tumours, TUNEL staining indicated significant apoptosis after 1 day (P < 0.05) and 4 days (P < 0.01) of treatment. Concordantly, Zn2+-DPA uptake increased significantly after 1 day (P < 0.05) and 4 days (P < 0.01). Surprisingly, annexin V failed to detect significant differences between control and treated animals. Contrary to the increasing uptake of Zn2+-DPA, 18 F-FDG tumour uptake decreased significantly at days 1 (P < 0.05) and 4 (P < 0.01).

CONCLUSIONS

Increase in apoptosis during anti-angiogenic therapy was detected significantly better with the low molecular weight probe Zn2+-DPA than with the annexin V-based probe. Additionally, significant treatment effects were detectable as early using Zn2+-DPA as with measurements of the glucose metabolism using 18 F-FDG.

KEY POINTS

• The detection of apoptosis by non-invasive imaging is important in oncology. • A new low molecular weight probe Zn2+-DPA shows promise in depicting anti-angiogenic effects. • The small Zn2+-DPA ligand appears well suited for monitoring therapy. • Treatment effects are detectable just as early with Zn2+-DPA as with 18F-FDG.

Alternative chelating agents: evaluation of the ready biodegradability and complexation properties

The ready biodegradability of four chelating agents, N,N'-(S,S)-bis[1-carboxy-2-(imidazol-4-yl)ethyl]ethylenediamine (BCIEE), N'-ethylenedi-L-cysteine (EC), N,N'-bis (4-imidazolymethyl)ethylenediamine (EMI) and 2,6-pyridine dicarboxylic acid (PDA), was tested according to the OECD guideline for testing of chemicals. PDA proved to be a readily biodegradable substance. However, none of the other three compounds were degraded during the 28 days of the test. Chemical simulations were performed for the four compounds in order to understand their ability to complex with some metal ions (Ca, Cd, Co, Cu, Fe, Mg, Mn, Ni, Pb, Zn) and discuss possible applications of these chelating agents. Two different conditions were simulated: (i) in the presence of the chelating agent and one metal ion, and (ii) in the simultaneous presence of the chelating agent and all metal ions with an excess of Ca. For those compounds that were revealed not to be readily biodegradable (BCIEE, EC and EMI), applications were evaluated where this property was not fundamental or even not required. Chemical simulations pointed out that possible applications for these chelating agents are: food fortification, food process, fertilizers, biocides, soil remediation and treatment of metal poisoning. Additionally, chemical simulations also predicted that PDA is an efficient chelating agent for Ca incrustations removal, detergents and for pulp metal ions removal process.

Absorption, translocation and metabolism of metamitron in Chenopodium album

BACKGROUND

In recent years, common lambsquarters (Chenopodium album L.) populations from sugar beet fields in different European countries have responded as resistant to the as-triazinone metamitron. The populations have been found to have the same D1 point mutation as known for atrazine-resistant biotypes (Ser264 to Gly). However, pot experiments revealed that metamitron resistance is not as clear-cut as observed with triazine resistance in the past. The objectives of this study were to clarify the absorption, translocation and metabolic fate of metamitron in C. album.

RESULTS

Root absorption and foliar absorption experiments showed minor differences in absorption, translocation and metabolism of metamitron between the susceptible and resistant C. album populations. A rapid metabolism in the C. album populations was observed when metamitron was absorbed by the roots. The primary products of metamitron metabolism were identified as deamino-metamitron and metamitron-N-glucoside. PABA, known to inhibit the deamination of metribuzin, did not alter the metabolism of metamitron, and nor did the cytochrome P450 inhibitor PBO. However, inhibition of metamitron metabolism in the presence of the cytochrome P450 inhibitor ABT was demonstrated.

CONCLUSION

Metamitron metabolism in C. album may act as a basic tolerance mechanism, which can be important in circumstances favouring this degradation pathway.

[Probing the mechanism and Ca-DPA concentration of individual Bacillus spores using trapping and Raman spectroscopy]

Measuring the levels of 2,6-pyridine dicarboxylic acid (DPA) in bacteria spores could provide the information about the DPA function, resistance mechanism and the mechanism of spore germination. The authors have measured levels of Ca-DPA of individual spores of different 19 kinds of Bacillus which from different sources, species, and strains by using laser tweezers Raman spectroscopy (LTRS). Also we have verified the reproducibility of the system simultaneously. To investigate the biochemical components and structure in single spore, a Raman tweezers setup was used to record the Raman spectrum of single spore. A NIR laser beam (30 mW, 785 nm) was introduced into an inverted microscope to form a tweezers for trapping the spore suspended in water, and the Raman scatter was excited by the same beam. Raman spectra of 30 spores of 19 bacillus strains which collected from different area in China were recorded, and 100 spores of B. subtilis ACCC10243 were measured. A spore of the same strain was probed 100 times for verifying the reproducibility of the LTRS system. A Matlab 7.0 edited program and Origin 8.0 were used to process the spectral data. Because Ca-DPA is the chelate of DPA and the calcium ion, and the strongest Raman bands at 1 017 cm(-1) was from Ca-DPA component of the spore, its intensity was linearly with the Ca-DPA concentration. Therefore, the 1017 cm(-1) bands of Ca-DPA could be used as the quantitative standard peak, and then calculated the concentration of Ca-DPA could be calculated according the intensity of 1017 cm(-1) peak. The results showed that Raman spectra of single spore can reflect the characteristics information of it. The diversity of Ca-DPA levels not only happened between different species and strains of bacillus, but also happened between different individual spores in the same strains of bacillus. Conclusion from these measurements is that there is heterogeneity in different individual spores. It is convenient to trapping and collecting its Raman spectrum in water directly, and then get the information of the level of DPA, without the complex preparation of separating, purifying spores and abstracting DPA, so we predict LTRS as a high sensitivity, high accuracy, rapid and effective method in the research of individual spores.

Synthesis and characterization of transition metal 2,6-pyridinedicarboxylic acid derivatives, interactions of Cu(II) and Ni(II) complexes with DNA in vitro

Mononuclear complexes M(L)Cl(2) where M=Mn(II), Fe(II), Co(II), Ni(II) and Cu(II) and (L=N,N-diethylpiperazinyl,2,6-pyridinedicarboxylate), have been synthesized and characterized by elemental analysis, FT-IR, (1)H NMR spectroscopy, UV-vis, magnetic moment, TGA/DSC, cyclic voltammetry and conductivity measurement data. The spectral data suggests that the dipicolinic acid acts as a bidentate ligand and is coordinated to the metal ion through the carboxylate oxygen. The cyclic voltammogram for Cu(L)Cl(2) complex was found to display two reversible Cu(II)/Cu(I) and Cu(II)/Cu(III) redox couple. The ligand exhibits a two-step thermolytic pattern while the complexes decompose in three stages respectively. An octahedral geometry has been proposed for both the complexes. The investigation of the interaction of the complexes with calf thymus DNA has been performed with absorption spectroscopy and fluorescence quenching experiments, which showed that the complexes are avid binders of calf thymus DNA. Also the interaction of the Cu(II) and Ni(II) complexes with plasmid DNA (pUC 19) was studied using agarose gel electrophoresis. The results revealed that these complexes can act as effective DNA cleaving agents resulting in the nicked form of DNA (pUC 19) under physiological conditions. The gel was run both in the absence and presence of an oxidizing agent (H(2)O(2)). The ligand and its complexes have also been screened against microbes in order to study their antibacterial action. The results revealed that the Cu(II) complex has activity comparable with the reference drugs gentamycin and flucanzole.

Neutrophils with toxic granulation show high fluorescence with bis(Zn2+-dipicolylamine) complex

Although blood neutrophils with toxic granulation provide an excellent means of evaluating acute bacterial infections, the methods are labor-intensive and their reproducibilities depend on the staining technique and the observer's judgment. We measured the flavin adenine dinucleotide (FAD) content of normal neutrophils and neutrophils with toxic granulation by flow cytometry after incubating them with bis(Zn(2+)-dipicolylamine) complex. A total of 122 blood samples (78 with neutrophils with toxic granulation, 44 with normal neutrophils without toxic granulation) were analyzed. The mean autofluorescence levels of neutrophils in the toxic granulation (+) group and toxic granulation (-) group were both 1.9 x 10(3) MESF (mean equivalent soluble fluorochrome) values. However, after incubating neutrophils with bis(Zn(2+)-dipicolylamine) complex for 15 min, the mean fluorescence intensities of neutrophils in the toxic granulation (+) and toxic granulation (-) groups were significantly enhanced by 71- and 19-fold to 138+/-78 x 10(3) MESF and 37+/-37 x 10(3) MESF, respectively (p <0.001). An MESF cutoff value of 79 x 10(3) showed a sensitivity of 93.2% and a specificity of 81.8% for neutrophils with toxic granulation. Similarly, the MESF level ratio, defined as the ratio of the MESF value after incubation with bis(Zn(2+)-dipicolylamine) complex to the autofluorescence MESF value, at a cutoff value of 41, showed a sensitivity of 92.3% and a specificity of 81.8% for the detection of neutrophils with toxic granulation. The MESF values of neutrophils after incubation with bis(Zn(2+)-dipicolylamine) complex did not correlate with the leukocyte (p >0.05) or neutrophil counts (p >0.05). In conclusion, measurement of FAD fluorescence intensity in neutrophils by flow cytometry after incubation with bis(Zn(2+)-dipicolylamine) complex is an easy, objective, and reliable method of detecting neutrophils with toxic granulation.

Airborne bacterial spore counts by terbium-enhanced luminescence detection: pitfalls and real values

Bacterial spore determination by terbium(III)-dipicolinate luminescence has been reported by several investigators. We collected spore samples with a cyclone and extracted dipicolinic acid (DPA) in-line with hot aqueous dodecylamine, added Tb(III) in a continuous-flow system and detected the Tb(III)-DPA with a gated liquid core waveguide fluorescence detector with a flashlamp excitation source. The absolute limit of detection (LOD) for the system was equivalent to 540 B. subtilis spores (for a 1.8 m3 sample volume (t = 2 h, Q = 15 L/min), concentration LOD is 0.3 spores/L air). Extant literature suggests that, from office to home settings, viable spore concentrations range from 0.1 to 10 spores/L; however, these data have never been validated. Previously reported semiautomated instrumentation had an LOD of 50 spores/L. The present system was tested at five different location settings in Lubbock, Texas. The apparent bacterial spore concentrations ranged from 9 to 700 spores/L and only occasionally exhibited the same trend as the simultaneously monitored total optical particle counts in the > or = 0.5 microm size fraction. However, because the apparent spore counts sometimes were very large relative to the 0.5+ microm size particle counts, we investigated potential positive interferences. We show that aromatic acids are very likely large interferents. This interference typically constitutes approximately 70% of the signal and can be as high as 95%. It can be completely removed by prewashing the particles.

Measurement of low-molecular-weight carboxylic acids in ambient air and vehicle emission by capillary electrophoresis

Within the last few years, capillary electrophoresis (CE), especially with indirect ultraviolet detection, has successfully been utilized for the analysis of low-molecular-weight (LMW) organic acids in a wide variety of matrices (e.g., food, pharmaceutical, environmental, industrial, clinical). The speed, resolution, and simplicity of CE, combined with low operating costs, make the technique an attractive option for the development of improved methods in this field. Hence, CE is becoming increasingly accepted for routine analytical work. In this chapter, the unique capability and applicability of the five selected CE methods used in the analysis of LMW carboxylic acids in ambient air and/or vehicle-emitted samples are described.

Design of a hairpin polyamide, ZT65B, for targeting the inverted CCAAT box (ICB) site in the multidrug resistant (MDR1) gene

A novel hairpin polyamide, ZT65B, containing a 3-methylpicolinate moiety was designed to target the inverted CCAAT box (ICB) of the human multidrug resistance 1 gene (MDR1) promoter. Binding of nuclear factor-Y (NF-Y) to the ICB site upregulates MDR1 gene expression and is, therefore, a good target for anticancer therapeutic agents. However, it is important to distinguish amongst different promoter ICB sites so that only specific genes will be affected. All ICB sites have the same sequence but they differ in the sequence of the flanking base pairs, which can be exploited in the design of sequence-specific polyamides. To test this hypothesis, ten ICB-containing DNA hairpins were designed with different flanking base pairs; the sequences ICBa and ICBb were similar to the 3'-ICB site of MDR1 (TGGCT). Thermal-denaturation studies showed that ZT65B effectively targeted ICBa and ICBb (DeltaTM=6.5 and 7.0 degrees C) in preference to the other DNA hairpins (<3.5 degrees C), with the exception of ICBc (5.0 degrees C). DNase I-footprinting assays were carried out with the topoisomerase IIalpha-promoter sequence, which contains five ICB sites; of these, ICB1 and ICB5 are similar to the ICB site of MDR1. ZT65B was found to selectively bind ICB1 and ICB5; footprints were not observed with ICB2, ICB3, or ICB4. A strong, positive induced ligand band at 325 nm in CD studies confirmed that ZT65B binds in the DNA minor groove. The selectivity of ZT65B binding to hairpins that contained the MDR1 ICB site compared to one that did not (ICBd) was confirmed by surface-plasmon studies, and equilibrium constants of 5x10(6)-1x10(7) and 4.6x10(5) M-1 were obtained with ICB1, ICB5,and ICB2 respectively. ZT65B and the previously published JH37 (J. A. Henry, et al. Biochemistry 2004, 43, 12 249-12 257) serve as prototypes for the design of novel polyamides. These can be used to specifically target the subset of ubiquitous gene elements known as ICBs, and thereby affect the expression of one or a few proteins.

Determination of free amino compounds in betalainic fruits and vegetables by gas chromatography with flame ionization and mass spectrometric detection

Amino acids and amines are the precursors of betalains. Therefore, the profiles of free amino compounds in juices obtained from cactus pears [Opuntia ficus-indica (L.) Mill. cv. Bianca, cv. Gialla, and cv. Rossa], pitaya fruits [Selenicereus megalanthus (K. Schumann ex Vaupel) Moran, Hylocereus polyrhizus (Weber) Britton & Rose, and Hylocereus undatus (Haworth) Britton & Rose], and in extracts from differently colored Swiss chard [Beta vulgaris L. ssp. cicla (L.) Alef. cv. Bright Lights] petioles and red and yellow beets (B. vulgaris L. ssp. vulgaris var. conditiva Alef. cv. Burpee's Golden) were investigated for the first time. Amino compounds were derivatized with propyl chloroformate. While gas chromatography (GC) with mass spectrometry was used for peak assignment, GC flame ionization detection was applied for quantification of individual compounds. Whereas proline was the major free amino compound of cactus pear and pitaya fruit juices, glutamine dominated in Swiss chard stems and beets, respectively. Interestingly, extremely high concentrations of dopamine were detected in Swiss chard stems and beets. Furthermore, the cleavage of betaxanthins caused by derivatization in alkaline reaction solutions is demonstrated for the first time. Amino acids and amines thus released might increase the actual free amino compound contents of the respective sample. To evaluate the contribution of betaxanthin cleavage to total amino acid and amine concentration, isolated betaxanthins were derivatized according to the "EZ:faast" method prior to quantification of the respective amino compounds released. On a molar basis, betaxanthin contribution to overall amino compound contents was always below 6.4%.

The synthesis and characterisation of Sn(IV) complexes of 2,6-pyridine dicarboxylate--the molecular structure of divinyltin(IV) derivative

A series of organotin(IV) derivatives were obtained employing 2,6-pyridinedicarboxylate as ligand: [{SnBu3(OOC)2C5H3N}n] (1), [SnBuCl(OOC)2C5H3N] (2) and [Sn(CHCH2)2(OOC)2C5H3N] (3). They were fully characterised by multinuclear NMR [1H, 13C{1H}, and 119Sn{1H}], IR spectroscopies and elemental analysis. In addition suitable crystals of (3) have shown a dimmeric arrangement by X-ray crystallographic studies, held together by Sn-O intermolecular interactions which persists in solution. The crystal packing shows hydrogen bonds joining the dimmers, forming two infinite one-dimensional chain. Each monomer comprises a Sn(IV) centre bonded to a pyridinecarboxylate-containing ring, through both nitrogen and oxygen donor atoms. It is also co-ordinated by a water molecule and two vinyl groups.

Quantitative surface-enhanced Raman spectroscopy of dipicolinic acid—towards rapid anthrax endospore detection

Dipicolinic acid (DPA) is an excellent marker compound for bacterial spores, including those of Bacillus anthracis (anthrax). Surface-enhanced Raman spectroscopy (SERS) potentially has the sensitivity and discrimination needed for trace DPA analysis, but mixing DPA solutions with citrate-reduced silver colloid only yielded measurable SERS spectra at much higher (>80 ppm) concentrations than would be desirable for anthrax detection. Aggregation of the colloid with halide salts eliminated even these small DPA bands but aggregation with Na2SO4(aq) resulted in a remarkable increase in the DPA signals. With sulfate aggregation even 1 ppm solutions gave detectable signals with 10 s accumulation times, which is in the sensitivity range required. Addition of CNS- as an internal standard allowed quantitative DPA analysis, plotting the intensity of the strong DPA 1010 cm(-1) band (normalised to the ca. 2120 cm(-1) CNS- band) against DPA concentration gave a linear calibration (R2 = 0.986) over the range 0-50 ppm DPA. The inclusion of thiocyanate also allows false negatives due to accidental deactivation of the enhancing medium to be detected.

Analysis of the germination of spores ofBacillus subtiliswith temperature sensitivespomutations in thespoVAoperon

A Bacillus subtilis strain with a base substitution in the ribosome-binding site of spoVAC was temperature sensitive (ts) in sporulation and spores prepared at the permissive temperature were ts in L-alanine-triggered germination, but not in germination with Ca2+-dipicolinic acid (DPA) or dodecylamine. Spores of a ts spo mutant with a missense mutation in the spoVAC coding region were not ts for germination with l-alanine, dodecylamine or Ca2+-DPA. These findings are discussed in light of the proposal that SpoVA proteins are involved not only in DPA uptake during sporulation, but also in DPA release during nutrient-mediated spore germination.

On-column complexation capillary electrophoretic separation of Fe2+ and Fe3+ using 2,6-pyridinedicarboxylic acid coupled with large-volume sample stacking

On-column complexation of Fe2+ and Fe3+ with 2,6-pyridinedicarboxylic acid (2,6-PDCA) formed anionic complexes, which were then separated by capillary zone electrophoresis with direct UV detection at 214 nm. To achieve reasonable separation selectivity and on-column complexation, the conditions such as pH, the concentration of 2,6-PCDA and the EOF modifiers in the electrolyte were examined. The electrolyte contained 5.0 mM 2,6-PDCA, 0.25 mM tetradecyltrimethlammonium bromide (TTAB) and 5% (v/v) acetonitrile at pH 4.0 was optimised for on-column complexation and the separation of Fe[PCDA]2(2-) and Fe[PCDA]2(-). To enhance the detection sensitivity, large-volume sample stacking (LVSS) was used for the on-line preconcentration of Fe[PCDA]2(2-) and Fe[PCDA]2(-). Under the optimised conditions, satisfactory working ranges (0.5-50 microM), lower detection limits (less than 0.1 microM) and good repeatability of the peak areas (R.S.D.: 5.2-7.8%, n = 5) was achieved using LVSS (300 s). With LVSS, the detection sensitivity was enhanced more than 50-fold compared to conventional hydrodynamic injection. The proposed method was used successfully for the determination of Fe2+ and Fe3+ in water samples.

A mixed matrix of 3-hydroxypicolinic acid and pyrazinecarboxylic acid for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry of oligodeoxynucleotides

A mixed matrix of 3-hydroxypicolinic acid (3-HPA) and pyrazinecarboxylic acid (PCA) was used for analysis of a variety of synthetic oligodeoxynucleotides ranging in length from 8-108-mers by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The experimental results showed that DNA segments with masses in the range from 5000 to 10,500 Da can be analyzed with high resolution (isotopic peaks resolved) when 3-HPA/PCA was prepared by mixing saturated 3-HPA solution and saturated PCA solution (in 50% of a 0.5 mol/L solution of diammonium hydrogen citrate plus 50% acetonitrile) at the volume ratio of 4:1. Each component of a mixture of d(A)1-10 gave a well-resolved peak. Moreover, when 3-HPA/PCA was used to analyze two mixtures, one containing two 23-mer DNA segments with a 9 Da difference (A and T) and the other with a 7 Da difference (AA and TG), the two 23-mer ion peaks were well separated from each other and an isotopically resolved spectrum of each component was recorded. Under the identical experimental conditions, the sample-to-sample reproducibility, resolution, signal-to-noise ratio and the tolerance to metal salts, with 3-HPA/PCA, were superior to those observed using 3-HPA alone for analysis of DNA segments.

Amperometric Hydrogen Peroxide Biosensor Based on Horseradish Peroxidase-labeled Nano-Au Colloids Immobilized on Poly(2,6-pyridinedicarboxylic acid) Layer by Cysteamine

A sensitive hydrogen peroxidase (H2O2) amperometric sensor based on horseradish peroxidase (HRP)-labeled nano-Au colloids has been proposed. Nano-Au colloids were immobilized by the thiol group of cysteamine, which was associated with the carboxyl groups of poly(2,6-pyridinedicarboxylic acid) (PPDA). With the aid of the hydroquinone, the sensor displayed excellent electrocatalytical response to the reduction of H2O2. Compared with the non-Au-colloid modified electrode, i.e., PPDA/HRP, the Au-colloid modified electrode exhibited better performance characteristics, including stability, reproducibility, sensitivity and accuracy. The biosensor shows a linear response to H2O2 in the range of 3.0 x 10(-7) - 2 x 10(-3) M. The detection limit was 1.0 x 10(-7) M.

The preparation of (S)-aspartate semi-aldehyde appropriate for use in biochemical studies

We report two three-step syntheses of (S)-aspartate semi-aldehyde, an important synthetic and biosynthetic precursor, from diprotected aspartic acid. The first synthesis proceeds via a thioester, the second via a Weinreb amide. Each route yields pure (S)-aspartate semi-aldehyde in excellent yield. (S)-Aspartate semi-aldehyde prepared in this manner has proved appropriate as a substrate for detailed enzyme studies.