Parallel synthesis of PNA-peptide conjugate libraries

An optimized semi-automatic protocol for parallel synthesis of up to 96 peptide nucleic acids (PNA) or PNA-peptide conjugates using Boc-protection strategy has been developed using a robotic system. The approach is illustrated by synthesizing PNA and PNA-peptide libraries varying between 15 and 27 amino acid units. The peptides (NLS (nuclear localization signal) or Tat-peptide) were attached to N-terminus of the PNA. The method was found to be far superior to that based on the SPOT/Fmoc protocol by which PNA oligomers are synthesized on a modified cellulose membrane. On a 0.5 micromole scale the method typically yielded 2 mg product of 90% purity by HPLC/MALDI-TOF analysis. This approach is suitable for screening of a large number of PNA and/or peptide sequences for biochemical and biological studies.     

Column preconcentration of trace manganese with the ion pair of 2-nitroso-1-naphthol-4-sulfonic acid tetradecyldimethylbenzyl-ammonium chloride supported on naphthalene and determination by derivative spectrophotometry

A column preconcentration method has been developed for the determination of trace amounts of manganese by preconcentration on 2-nitroso-1-naphthol-4-sulfonic acid (nitroso-S)-tetradecyldimethylbenzylammonium (TDBA) naphthalene as an adsorbent using a simple funnel tipped glass tube. Manganese reacts with nitroso-S to form a water soluble brown colored chelate anion. The chelate anion forms a water insoluble Mn-Nitroso-S-TDBA ion pair on naphthalene packed in a column in the pH range 9.6-10.5 at a flow rate of 1-2 ml/min. The solid mass consisting of manganese complex and naphthalene is dissolved in 5 ml of dimethylformamide (DMF) and the metal determined by second derivative spectrophotometry. The calibration curve is linear in the concentration range 0.25-35.0 micrograms of Mn in 5 ml of the final DMF solution. Eight replicate determinations of 25 micrograms of standard manganese solution give a mean peak height of 4.0 with a correlation coefficient of 0.9995 and relative standard deviation of +/- 1.1%. The sensitivity was calculated to be 0.502(d2 A/d lambda 2)/microgram ml-1 from the slope of the calibration curve. The detection limit was 0.020 microgram ml-1 for manganese at the minimum instrumental settings (signal to noise ratio = 2). Various parameters effecting the method such as the effect of pH, volume of aqueous phase and interference of a number of metal ions on the determination of manganese have been evaluated to optimize the conditions for its determination in standard alloys and biological samples.     

Ammonium tetraphenylborate-naphthalene adsorbent for the preconcentration and trace determination of iron in alloys and biological samples using 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol by third derivative spectrophotometry

A solid ion-pair material produced from ammonium tetraphenylborate on naphthalene (ATPB-naphthalene) provides a simple, rapid, economical and selective technique for preconcentrating iron from approximately 500 ml of aqueous solution of standard alloys and biological samples. Iron reacts with 2-(5-bromo-2-pryidlazo)-5-diethylaminophenol (5-Br-PADAP) to form a water-soluble cationic complex. When the aqueous solution of this cationic species in the pH range 3.2-8.5 is passed over the adsorbent ATPB-naphthalene at a flow rate of 1 ml min(-1), it is quantitatively retained on naphthalene as an uncharged ion-associated complex. The solid mass from the column was dissolved out with 5 ml of dimethylformamide (DMF) and iron is determined by third derivative spectrophotometry by measuring the signal d(3)A/ dlambda(3) between lambda(2)(773 nm) and lambda(3)(737 nm). The calibration curve is linear over the concentration range 0.10-25.0 mug of iron in 5 ml of DMF solution. Eight replicate determinations of 5 mug of iron gave a mean intensity (peak-to-peak signal between lambda(2) and lambda(3)) of 1.534 with a relative standard deviation of 0.90%. The sensitivity of the method is 0.307 (d(3)A/dnm(3) )/mug found from the slope of the calibration curve. The interference of a large number of anions and cations has been studied and the optimized conditions developed were utilized for the trace determination of iron in various standard alloys and biological samples.     

Simultaneous determination of lead and cadmium in various environmental and biological samples by differential pulse polarography after adsorption of their morpholine-4-carbodithioates onto microcrystalline naphthalene or morpholine-4-dithiocarbamate-CTMAB-naphthalene adsorbent

A highly selective, sensitive and rapid differential pulse polarographic method (DPP) has been developed for the simultaneous estimation of trace amounts of lead and cadmium in standard alloys, biological and environmental samples. The morpholine-4-carbodithioates of the samples were absorbed on microcrystalline naphthalene in the pH range of 5-10 for lead and 3.4-11 for cadmium. The metal complexes were desorbed with 10 ml of 1M HCl and determined simultaneously with a differential pulse polarograph. These metals can alternatively be quantitatively adsorbed on morpholine-4-dithiocarbamate-cetyltrimethylammonium bromide-naphthalene adsorbent packed in a column and determined similarly. The detection limits are 0.14 ppm for Pb and 0.014 ppm for Cd at minimum instrumental settings (signal-to-noise ratio = 2). The linearity is maintained in the concentration ranges of Pb, 0.7-15 ppm and Cd, 0.07-10 ppm with a correlation factor of 0.9997 and relative standard deviations of 0.95 and 0.81%, respectively. Various parameters such as the effect of pH, volume of aqueous phase, and interference of a number of metal ions on the estimation of lead and cadmium have been studied in detail to optimize the conditions for their simultaneous estimation in various biological and environmental samples.     

Column chromatographic preconcentration of palladium with dimethyl glyoxime and acenaphthenequinone dioxime on naphthalene

A solid material consisting of dimethyl glyoxime (DMG), acenaphthenequinone dioxime (ANDO) or DMG-ANDO on naphthalene provides a very convenient, rapid and economical method for the preconcentration of palladium in synthetic samples. Pd-DMG, Pd-ANDO and Pd-DMG-ANDO are quantitatively retained on naphthalene in the column in the pH ranges 2.2–4.4, 1.8–5.6 and 1.7–6.8, respectively. The solid mixture consisting of the metal complex together with naphthalene is stripped from the column with 5 ml of dimethylformamide (DMF)-n-butylamine and the absorbance is measured at 247.6 nm with an atomic absorption spectrometer. Calibration graphs are linear over the palladium concentration range 5–25 μg per 5 ml of the final solution for all the three complexes. Ten replicate determinations of a sample solution containing 10 μg of palladium gave mean absorbances of 0.180, 0.225 and 0.230 with relative standard deviations of 1.8, 1.7 and 1.6% using the reagents DMg, ANDO and DMG-ANDO, respectively. The sensitivity of the method is better than the direct atomic absorption spectrometric determination of palladium. It is highest in case of the mixed ligands, i.e., DMG-ANDO (0.038 μg ml^?1 for 1% absorption). The method can be applied to the trace determination of palladium in complex materials.     

Synthesis and spectral studies of platinum complexes with amide-group containing ligands

Summary Complexes of platinum(II) with 2-(acetylamino)benzoic acid, 2-(benzoylamino)benzoic acid, maleanilic acid, malea-1-naphthanilic acid, 2-(phenylamino)benzoic acid, 2-[(2-aminophenylamino)carbonyl]benzoic acid, 2-(aminobenzoyl)benzoic acid, 2-[1-naphthalenylamino)-carbonyl]benzoic acid, 2-(2-aminobenzoylamino)-benzoic acid have been prepared and characterized by elemental analysis, molar conductivity measurements, thermal data and i.r., electronic and n.m.r. spectra.     

Spectrophotometric determination of bismuth,cobalt, and nickel after extraction of their xanthates with molten naphthalene

Summary A new method for the spectrophotometric determination of bismuth, cobalt and nickel after extraction of their xanthates into molten naphthalene is described. The optimum pH values are 2.4–4.5 for Bi, 7.5–9.0 for Co, 5.5–7.5 for Ni. The naphthalene containing the metal chelates is dissolved in chloroform, and the absorbance is measured against a reagent blank at 362, 350 and 420 nm for Bi, Co and Ni and respectively. Few ions interfere and the method has been applied successfully for the determination of these metal ions in various complex materials.

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Zusammenfassung Eine neue Methode für die spektrophotometrische Bestimmung von Wismuth, Kobalt und Nickel nach Extraktion ihrer Xanthate mit geschmolzenem Naphthalin wurde beschrieben. Das optimale pH für Wismut beträgt 2,4–4,5, für Kobalt 7,5–9,0 und für Nickel 5,5–7,5. Das die Metallchelate enthaltende Naphthalin wird in Chloroform gelöst und die Extinktion gegen eine Reagens-Leerlösung bei 362, 350 bzw. 420 nm für Bi, Co bzw. Ni gemessen. Nur wenige Ionen stören. Das Verfahren wurde mit Erfolg zur Bestimmung der genannten Ionen in verschiedenen komplexen Gemischen angewandt.

     

Spectrophotometric determination of copper after adsorption of its 1-phenyl-4,4,6-trimethyl(1H, 4H)-pyrimidine-2-thiol complex onto microcrystalline naphthalene

A selective Spectrophotometric method has been developed for the trace determination of copper after adsorption of its 1-phenyl-4,4,6-trimethyl(1H, 4H)-pyrimidine-2-thiol (PTPT) complex onto microcrystalline naphthalene. The complex is quantitatively adsorbed on naphthalene in the pH range 7.5–11.5, separated by filtration, dissolved in dimethylformamide (DMF) and determined spectrophotometrically at 400 nm. Beer's law is obeyed in the concentration range 2.5–37.5 g of copper in 10 ml of DMF. The molar absorptivity and Sandell's sensitivity are 1.30 × 10⁴1 · mol^–1 · cm^–1 and 0.0048g cm^–2, respectively. Ten replicate analyses of a solution containing 20.0 g of copper gave a mean absorbance of 0.410 with a relative standard deviation of 0.91 %. The interferences of various ions have been studied and the method has been validated by the determination of copper in various standard reference materials, beers, wines, human hair, goat liver and environmental samples.On leave from St. Stephen's College, Delhi 110 007, India     

N-Methylethylxanthocarbamate as an Analytical Reagent: Differential Pulse Polarographic Determination of Cadmium in Standard Alloys, Biological and Environmental Samples after Adsorption of its Complex on Microcrystalline Naphthalene

N-methylethylxanthocarbamate has been used as an analytical reagent for the determination of trace amounts of cadmium in standard alloys, biological, and environmental samples. The reagent has been found to form a water insoluble complex with cadmium. It is quantitatively adsorbed over microcrystalline naphthalene in the pH range 2.5 to 12.0. The metal complex is desorbed with HCl and cadmium determined with a differential pulse polarograph. The detection limit is 0.05 ppm (signal-to-noise ratio = 2) and the linearity is maintained in the concentration range 0.2–25 g/ml, with correlation coefficient of 0.9995 and a relative standard deviation of ±0.81%. Characterization of the electroactive process includes an examination of the degree of reversibility. Various parameters, such as the effect of pH, reagent concentration, amount of naphthalene, volume of aqueous phase, and the interference of a large number of metal ions on the determination of cadmium, have been studied in detail to optimize the conditions for its determination in various complex materials.     

Synthesis and utility of new amine/nucleobase addition products of allenylphosphonates

In the reaction of allenylphosphonates with amines/nucleobases, depending on the amine and the allenylphosphonate, either Z- or E-vinylphosphonate or allylphosphonate as a single isomer with a β-amino functionality was isolated. A simple route to phosphonates with a β-NH₂ group is developed by direct reaction with ammonia. In reactions with adenine, three different modes of reaction, with one of them involving an unusual cyclisation, are observed. The utility of (enamino)allyl phosphonate products thus obtained in the synthesis of (enamino)-1,3-butadienes via Horner-Wadsworth-Emmons (HWE) reaction is also demonstrated.