Fast analysis of low molecular mass compounds present in snake venom: identification of ten new pyroglutamate-containing peptides

Characterization of the peptide content in snake venoms can be an important tool for the investigation of new pharmacological lead compounds. For this purpose, single-step analysis of crude venoms has recently been demonstrated using mass spectrometry (MS) techniques. Reproducible profiles of ions in MS and MS/MS spectra may also be used to compare venoms from different species. In this work matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) was used to obtain mass patterns of the major peptides (<8 kDa) found in pooled venoms from the genera Bothrops and Crotalus. Venoms from five different Bothrops species (B. jararaca, B. insularis, B. alternatus, B. jararacussu, and B. neuwiedi) and three Crotalus species (C. viridis, C. adamanteus and C. durissus terrificus) were analyzed. In agreement with other reports, venoms from Bothrops species contained a variety of peptides in the range m/z 1000-1500, and in some samples larger components (m/z 7000-8000) were detected. In the Crotalus species venoms were rich in peptides ranging from m/z 1000-1500 and 4000-5500. MS/MS experiments on the low molecular mass peptides (m/z 1000-1500) confirmed the presence of ten new bradykinin-potentiating peptides among venoms from genera Bothrops and Crotalus. In order to determine whether additional peptides could be identified after partial purification, B. jararaca venom was subjected to size-exclusion chromatography on Sephacryl S-200, and two distinct low molecular mass pools were analyzed further by MALDI-TOFMS. No additional peptides were detected from the pool with masses below 2000 Da but a substantial improvement with better resolution was observed for the pool with masses above 7000 Da, indicating that complex samples such as crude snake venoms can be analyzed for low molecular mass peptides using a single-step procedure.     

Nouvolle synthcse de la dihydro-5,6 methoxy-6 2H-pyrannone-5

The α,β-ethylenic ketone 5 was obtained in 35% yield in four steps from 1. The intermediate product was a brominated ketal obtained in the form of a mixture of two isomers 6 and 7 . The stereochemistry and conformation was established by a study of the 250 MHz nmr spectra. During the dehydrobromination of 6 and 7 , a relatively easy isomerization of the α,β-ethylenic ketal occured by displacement of the double bond giving theβ,γ-ethylenic ketal 10 .     

Vitamin B12: How the Problem of Its Biosynthesis Was Solved

Vitamin B₁₂ is an essential vitamin for human health, and lack of it leads to pernicious anemia. This biological activity has attracted intense interest for some time; in addition, the complex architecture of the B₁₂ molecule has fascinated chemists and biochemists since its discovery as the first natural organocobalt complex and the establishment of its structure by X-ray analysis. The organic ligand surrounding the cobalt displays many stereogenic centers along its periphery carrying reactive functional groups. This complexity led vitamin B₁₂ to be rightly regarded as an extreme challenge to the synthetic chemist. Yet microorganisms achieve this synthesis in vivo with complete control of regio- and stereochemistry. How do they do it? This review tells the full remarkable story. Success in unraveling this biosynthetic puzzle resulted from a collaborative effort by biologists and chemists using the full range of methods available from their disciplines–from genetics at one end of the spectrum to synthesis and NMR spectroscopy at the other. This work can act as a guide for future research on the biosynthesis of yet more complex natural substances.     

Senecipyrrolidine,an unusual pyrrolidine alkaloid isolated from Jacobaea gigantea (Desf.) Pelser (Asteraceae)

Alkaloids and phenolic compounds are among the most biologically active natural products from the Jacobaea/Senecio genera (Asteraceae). To isolate original natural products directly from Jacobaea gigantea crude polar extracts, centrifugal partition chromatography (CPC) was used. Previously, we reported the phytochemical study of J. gigantea (syn. Senecio giganteus) n-butanol extract using various classical chromatographical techniques combined with CPC. Herein major constituents from the J. gigantea crude ethyl acetate extract and further compounds from the n-butanol extract were purified in only one step using this technique. A new pyrrolidine alkaloid, named senecipyrrolidine was isolated along with thirteen known compounds – chiro-inositol, three phenolic acids, six flavonoids, two quinones and emiline, another pyrrolidine alkaloid – from crude n-butanol or ethyl acetate extracts. Pyrrolidine alkaloids were isolated for the first time in the Jacobaea/Senecio genera and were probably biogenetically related to the two isolated quinones derivatives jacaranone and 3a-hydroxy-3,3a,7,7a-tetrahydrobenzofuran-2,6-dione, isolated in this species.     

Determination of total fat in milk- and soy-based infant formula powder by supercritical fluid extraction

Commercially available simple benchtop systems using CO2 supercritical fluid extraction (SFE) eliminate expensive organic solvent disposal problems and offer potential to meet a demand for rapid, accurate high-volume gravimetric determinations of total fat content of infant formula powders. A Data Quality Objectives (DQOs) approach was used to evaluate the performance characteristics of instrumental SFE extraction for determination of total gravimetric fat in infant formula. The established DQOs included the following: ACCURACY: Correct values were obtained for a suitable reference material, SRM 1846 Infant Formula [National Institute of Standards and Technology (NIST), Gaithersburg, MD]. RUGGEDNESS: Variables were defined as (1) extraction time (35 min optimum); (2) ratio of sample size to diatomaceous earth support material (1 g sample/2 g support); (3) ratio of distilled water to alcohol (50% isopropanol optimum for both milk- and soy-based infant formula samples); (4) extraction flow rate was 3-3.5 mL/min optimum. PRECISION: Relative standard deviations of multiple determinations fell within the Horwitz limits of acceptability of < or = 2.8% at the level of analyte determined (0.34-2.5% obtained). SCOPE OF APPLICABILITY: Includes milk- and soy-based infant formula powders. Research data were obtained by use of a commercially available fat analyzer. Samples of the SRM, 2 commercial milk-based and 3 commercial soy-based infant formula products were distributed to 2 additional collaborating laboratories. Very good agreement was obtained among the submitting and collaborating laboratories for these samples. The use of clearly defined DQOs to establish method performance characteristics, along with the commercially available reference material, provided the mechanism for verification and validation of analytical methodology.     

Microporous Magnesium and Manganese Formates for Acetylene Storage and Separation

Acetylene sorption of microporous metal formates M(HCOO)₂ (M=Mg and Mn) was investigated. Measurements of acetylene sorption at 196, 275, and 298 K showed a Type I isotherm with quick saturation at low pressures, and 50–75 cm³ g^?1 uptake at 1.0 atm. The single‐crystal X‐ray structure analysis of the acetylene‐adsorbed metal formates revealed that acetylene molecules occupy two independent positions in the zigzag channels of the frameworks with a stoichiometry of M(HCOO)₂?1/3C₂H₂, which is consistent with the gas sorption experiments. No specific interaction except van der Waals interactions between the adsorbed acetylene molecules and the walls of the frameworks was found. Sorption properties of other gases, including CO₂, CH₄, N₂, O₂, and H₂, were also investigated. When the temperature was increased to 298 K, the amount of adsorbed acetylene was still above 60 cm³ g^?1 for Mg(HCOO)₂ and 50 cm³ g^?1 for Mn(HCOO)₂, whereas the uptake of other gases decreased substantially. The microporous metal formates may thus be useful not only for the storage of acetylene but also its separation from other gases at room or slightly higher temperatures.     

Multicopy suppressors for novel antibacterial compounds reveal targets and drug efflux susceptibility

Gene dosage has frequently been exploited to select for genetic interactions between a particular mutant and clones from a random genomic library at high copy. We report here the first use of multicopy suppression as a forward genetic method to determine cellular targets and potential resistance mechanisms for novel antibacterial compounds identified through high-throughput screening. A screen of 8640 small molecules for growth inhibition of a hyperpermeable strain of Escherichia coli led to the identification of 49 leads for suppressor selection from clones harboring an E. coli genomic library. The majority of suppressors were found to encode the multidrug efflux pump AcrB, indicating that those compounds were substrates for efflux. Two leads, which produced clones containing the gene folA, encoding dihydrofolate reductase (DHFR), proved to target DHFR in vivo and were competitive inhibitors in vitro.     

Structural and conformational properties of 1,2-propadienylphosphine (allenylphosphine) studied by microwave spectroscopy and quantum chemical calculations

1,2-Propadienylphosphine (allenylphosphine), H(2)C=C=CHPH(2), has been investigated by Stark and Fourier transform microwave spectroscopy. Two rotameric forms denoted syn and gauche have been assigned. The syn form has a symmetry plane (C(s)() symmetry) where the lone electron pair of phosphorus points toward the double bonds. The phosphino group is rotated roughly 120 degrees from this position in the gauche rotamer. The dipole moment of syn was determined to be mu(a) = 1.613(23), mu(b) = 2.347(24), mu(c) = 0 (for symmetry reasons), and mu(tot) = 2.848(28) x 10(-30) C m [0.854(8) D]. The energy difference between the two forms was found to be 2.1(4) kJ/mol from relative intensity measurements with syn as the more stable conformer. Extensive quantum chemical calculations have been carried out and accurate equilibrium structures have been determined for these two rotamers, as well as for the corresponding two conformers of vinylphosphine (H(2)C=CHPH(2)).