Development of a pulsed radio frequency ignited multicusp-free negative hydrogen ion source.

A multicusp-free external antenna based radio frequency (RF) negative hydrogen (H-) ion source was developed to produce 16 mA of H- ion current at -50 kVDC accelerating voltage operated with a pulse width of 2 ms at 2 Hz repetition rate. A pulsed RF igniter system is devised for generating the initial electron and ion pairs required to generate the main plasma in the pulsed mode. This pulsed RF igniter reliably starts ignition with a hydrogen gas flow rate in the range of 18-50 standard cubic centimeter per minute (SCCM). This system eliminates the need of igniter in continuous operation although it is operated in low power mode. This source operating at a low average power and without any moving parts can be expected to have a superior lifetime. This paper describes the development and operational characteristics of the pulsed RF ignited H- ion source.

Immune response against subclinical haemonchosis in Himalayan hill goats.

Haemonchosis commonly occurs as chronic and subclinical infection in small ruminants, and understanding of immunological response against subclinical haemonchosis is of paramount importance for designing and implementing effective control strategies. The present study was designed to evaluate immunological response during subclinical haemonchosis, experimentally established in goats. Sixteen 5-6 month-old helminth naive kids were randomly allocated into one of two groups, infected and uninfected; the infected group being infected per os with 250 Haemonchus contortus larvae per kg body weight. Faecal, blood and serum samples were collected every third day up to 30 days post-infection (DPI), thereafter weekly up to 58 DPI to record changes in faecal egg count (FEC), haemoglobin (Hb), packed cell volume (PCV), peripheral eosinophil percentage and immunological parameters, such as macrophage cytokine interleukin-12 (IL-12), Th1 cytokine (IFN-γ), Th2 cytokines (IL-4, 13, 25, 33) and immunoglobulins (IgG and IgE). Pre-patent period of H. contortus in the present study was 18 days and eggs per gram (EPG) peaked on 30 DPI. The total reduction in body weight gain in the infected group was 26 g per day when compared with uninfected animals. Hb (7.35 ± 0.34 g/dL in infected animals compared with 9.76 ± 0.67 in control animals) and PCV levels (22 ± 1.54 g/dL in infected animals compared with 29.2 ± 1.27 in control animals) decreased significantly up to 44 DPI in infected group (P = 0.000). IL-4, IL-13, IL-33, IgG and IgE showed significant increase in infected animals at different periods. IFN-γ, IL-12 and IL-25 did not show any significant changes barring a steep rise of IFN-γ on 27 DPI. A positive correlation was observed between IgE and IL-4 in subclinical haemonchosis. Of particular note was that all the major cytokines, such as IFN-γ (P = 0.000), IL-4 (P = 0.000), IL-13 (P = 0.009), and both IgG (P = 0.000) and IgE (P = 0.003), were observed at the lowest concentration on 24 DPI. The effect of infection was found to be significant on cytokines with a strong interaction with time. Taken together, the data suggest that Th2 immune response is predominating in subclinical haemonchosis. The economic loss in term of body weight gain due to subclinical haemonchosis was considerable.

Synthesis and anticandidal properties of polyoxin L analogues containing alpha-amino fatty acids.

Analogues of polyoxin L containing amino acids with saturated fatty acid like side chains were synthesized from the benzyloxycarbonyl-protected alpha-amino fatty acid p-nitrophenyl ester and uracil polyoxin C. Transfer hydrogenolysis using palladium black and formic acid gave diastereomeric, dipeptidyl polyoxin L analogues containing alpha-aminooctanoic acid (3), alpha-aminododecanoic acid (4), or alpha-aminohexadecanoic acid (5) as the amine terminal residue in 40-60% yield. Diastereomers of 3 and 5 were resolved by using high-performance liquid chromatography on a reversed-phase column and designated as 3a, 3b and 5a, 5b. Analogues 3-5 were excellent inhibitors of chitin synthetase from Candida albicans; 4, the best inhibitor, had an ID50 of 0.5 microM. The L,L diastereomers of 3 and 5 were 1-2 orders of magnitude more potent chitin synthetase inhibitors than their D,L homologues. None of the synthetic polyoxin L analogues inhibited transport of trimethionine, but 3a, 4, and 5b caused decreases of 71%, 87%, and 83%, respectively, in the initial rate of uptake of dileucine. Compounds 3-5 were significantly more stable to peptidase degradation than polyoxin L analogues containing naturally occurring alpha-amino acids. Compound 4 inhibited growth of C. albicans in culture at 40-80 micrograms/mL. All other analogues were less potent antifungals. The results suggest that synthetic polyoxins can be designed to have increased affinity for a peptide transport system and to have increased stability against intracellular degradation in C. albicans.

Synthesis and fungicidal activity of some 5-(2-aminoalkanoyl)-8-aryl-4(5H)-oxo-1,2,4-triazolo[4,3-b]-1,4,2, 6-dithiadiazine 6,6-dioxide derivatives.

Title compounds (5) were conveniently prepared from 5-aryl-3-mercapto-1,2,4-triazoles (1) and chloro-sulphonyl isocyanate (CSI) to give 8-aryl-4-(5H)-oxo-1,2,4-triazolo-[4,3-b]-1,4,2,6-dithiadiazine -6,6-dioxide (2). The Compound (2) and one suspension of 2-(benzyloxycarbonylamino) akanoic acid (3) in the presence of BOP reagent afforded Z-derivatives 8-aryl-5-(2-benzyloxycarbamoyl)alkanoyl-4(5H)-oxo- 1,2,4-triazolo[4,3-b]-1,4,2,6-dithiadiazine 6,6-dioxide (4). The Z-derivatives (4) gave aspected product (5) when treated with Pd-c 5% and formic acid in DMF. These compounds have been tested in vitro for their fungicidal activity against Aspergillus niger, Fusarium oxisporum and Cephalosporium saccharii and results were compared with their parent dithidiazines.

Chemochromatography: its use for the separation of nikkomycins X and Z.

A novel mode of reversed-phase high-performance liquid chromatography in which the mobile phase reacts chemically with the compounds to be separated was developed. Nikkomycin X and nikkomycin Z, two natural isomeric nucleoside peptide antibiotics, move as a single peak on a C18 reversed-phase column using an aqueous trifluoroacetic acid mobile phase. Addition of sodium bisulfite (1.0%) to the mobile phase results in the formation of a polar bisulfite addition product with nikkomycin X, but not with nikkomycin Z, inside the HPLC column. This type of reactive chromatography, or chemochromatography, led to the analytical and preparative separation of nikkomycins X and Z which are normally very intractable to separation by conventional chromatographic techniques.

Synthesis of alpha-factor analogues containing photoactivatable and labeling groups.

Analogues of alpha-factor, Saccharomyces cerevisiae tridecapeptide mating pheromone (H-Trp-His-Trp-Leu-Gln-Leu-Lys-Pro-Gly-Gln-Pro-Met-Tyr-OH), containing both p-benzoyl phenylalanine (Bpa), a photoactivatable group, and 3-(mono- or di-iodo-4-hydroxyphenyl)propanoic acid (iodinated HPP) or biotin as a tag, were synthesized using solid-phase methodologies on a [phenylacetamido]-methyl (PAM) resin. Bpa was introduced into the peptides using Bpa-hydroxybenzotriazole active ester during peptide chain assembly. Biotinylated alpha-factor analogues were prepared by assembling the desired peptide on the resin, and then reacting a specific amino group either with the symmetrical anhydride of biotin or with biotin using BOP as the activating agent prior to anhydrous hydrogen fluoride cleavage. Iodinated HPP was incorporated by acylating free peptides with Bolton-Hunter reagent (3-[diiodo-4-hydroxyphenyl]propanoic acid hydroxysuccinimide ester) in N,N-dimethylformamide and borate buffer (pH 8.0) solutions. Purification of all peptides to 98% or greater homogeneity was accomplished by high-performance liquid chromatography on a reversed-phase mu-Bondapak C18 column with acetonitrile/water/trifluoroacetic acid as the mobile phase. All products were characterized by amino acid analysis and fast atom bombardment mass spectrometry. Two analogues, alpha-(diiodotyrosine)-His-Bpa-Leu-Gln-Leu-Arg-Pro-Gly-Gln-Pro-Nle-Tyr-O H, and epsilon-(diiodo-HPP)-Lys-His-Bpa-Leu-Gln-Leu-Arg-Pro-Gly-Gln-Pro-Nle-Tyr -OH, were one twentieth to one-fortieth as active as a alpha-factor, and exhibited approximately one order of magnitude lower affinity to the alpha-factor receptor. The results suggest that these two analogues are alpha-factor agonists and that they can be used as probes of the alpha-factor receptor.

Histidine2 of the alpha-factor of Saccharomyces cerevisiae is not essential for binding to its receptor or for biological activity.

Seven His2 analogs of the Saccharomyces cerevisiae [Nle12]alpha-factor, WXWLQLKPGQP(Nle)Y, where X = beta-D-thienylalanine, beta-L-thienylalanine, 1-D-methylhistidine, 1-L-methylhistidine, 3-D-methylhistidine, 3-L-methylhistidine, and beta-3-L-pyridylalanine, were synthesized and purified to homogeneity. Assays were carried out on binding to the alpha-factor receptor and of biological activity determined by either growth arrest or morphological changes in target cells. In the L-isomer, replacement of the imidazole of histidine by thiophene or 3-pyridyl groups or derivatization of either nitrogen of the imidazole ring by methylation resulted in a 2-100-fold decrease in bioactivity. D-Isomers of the beta-thienylalanyl-, 1-methylhistidinyl-, or 3-methylhistidinyl-alpha-factors did not possess measurable bioactivity with the exception of comparatively low activity of the 3-D-methylhistidinyl and 1-D-methylhistidinyl-alpha-factors in the morphogenesis assay. In contrast, both active and inactive analogs demonstrated binding affinities 10-20-fold less than that of [Nle12]alpha-factor. These results indicate that the histidine residue of alpha-factor is not required for binding to the receptor or for biological activity and that bioactivity and binding can be dissociated through the use of pheromone analogs.