Purification, Characterization, and Specificity Determination of a New Serine Protease Secreted by Penicillium waksmanii

The purpose of this work was to purify a protease from Penicillium waksmanii and to determine its biochemical characteristics and specificity. The extracellular protease isolated that was produced by P. waksmanii is a serine protease that is essential for the reproduction and growth of the fungus. The protease isolated showed 32 kDa, and has optimal activity at pH 8.0 and 35 °C towards the substrate Abz-KLRSSKQ-EDDnp. The protease is active in the presence of CaCl₂, KCl, and BaCl, and partially inhibited by CuCl₂, CoCl₂ and totally inhibited by AlCl₃ and LiCl. In the presence of 1 M urea, the protease remains 50 % active. The activity of the protease increases 60 % when it is exposed to 0.4 % nonionic surfactant-Triton X-100 and loses 10 % activity in the presence of 0.4 % Tween-80. Using fluorescence resonance energy transfer analysis, the protease showed the most specificity for the peptide Abz-KIRSSKQ-EDDnp with k _cat/K _m of 10,666 mM^?1?s^?1, followed by the peptide Abz-GLRSSKQ-EDDnp with a k _cat/K _m of 7,500 mM^?1?s^?1. Basic and acidic side chain-containing amino acids performed best at subsite S₁. Subsites S₂, S₃, S^′ ₂, and S^′ ₁, S^′ ₃ showed a preference for binding for amino acids with hydrophobic and basic amino acid side chain, respectively. High values of k _cat/K _m were observed for the subsites S₂, S₃, and S^′ _2. The sequence of the N-terminus (ANVVQSNVPSWGLARLSSKKTGTTDYTYD) showed high similarity to the fungi Penicillium citrinum and Penicillium chrysogenum, with 89 % of identity at the amino acid level.     

Natural Brazilian Raw Material to Develop O/W Emulsions Containing Lamellar Gel Phase (Development and Analysis of Emulsion with Vegetable Oils)

Oil-in-water emulsions were developed employing the HLB system and emulsion phase inversion (EPI) method. X-ray diffraction revealed that the anisotropic structures around the inner phase globules were lamellar gel network phases. The calculated distances between the lamellae made after preparation and 3 month latter showed that there was no swelling of the lamellar gel network indicating good stability and few changes during storage. The developed emulsions were stable and have potential to be employed for cosmetic and pharmaceutical purposes. The gel phase network and vegetal components seemed to be contributing factors.      

Phosphonium Diaza-Diylids and Aza-Yldiid as New and Efficient Reagents For Primary and Secondary Amines Synthesis

Abstract

Metallated aminophosphonium ylids, diaza-diylids and azayldiid, are investigated as reagents for primary and secondary amines synthesis.     

Umpolung of α-Allenic Ketones and Esters by Phosphorus Groups

Abstract

Change in the regioselectivity of the addition of nucleophilic compounds YH (ROH, RSH, RNH₂) on α -allenic ketones and esters can be achieved by using the triphenylphosphonio group as an umpolung agent¹⁾. In this way α, β-unsaturated ketones and esters 4 are obtained with heteroatomic substituents in the γ position. The Umpolung scheme of the activated allene 1 is charaterized by a functional vinylphosphonium salt 2 as a synthetic equivalent of the a⁴-synthon 3.     

Homologation of α,β-Ethylenic Ketones in Substituted β,γ-Ethylenic Ketones Using Phosphoniosilylation

Among the methods described (1–4) to prepare β,γ-unsaturated ketones 2, Warren (4) recommends the Wittig-Horner procedure involving β-acetalated diphenylphosphinoxides reagents |scheme 1 (i)|.     

1, 1, 1-Trichloropropanone: A Mild,Selective Acetylating Agent

The use of the title compound in the acetylation of primary and secondary amines i s described.     

Degradation of the insecticide parathion in methanol by gamma-irradiation

The gamma-radiation from⁶⁰Co was used to induce parathion degradation in methanol solution, and the resulting products were quantified by GC-NPD and identified by GC-MS. The insecticide was completely degraded (99%) in methanol after treatment with 30 kGy doses at a dose rate of 3.12 kGy h⁻¹. The metabolites detected after radiolysis were p-aminophenol, paraoxon and aminoparathion, but no p-nitrophenol. The parathion radiation yield (G-parathion) in methanol solution was also calculated.     

Water-in-Oil-in-Water Double Emulsions as Protective Carriers for Sambucus nigra L. Coloring Systems

The use of natural colorants is needed to overcome consumer concerns regarding synthetic food colorants′ safety. However, natural pigments have, in general, poor stability against environmental stresses such as temperature, ionic strength, moisture, light, and pH, among others. In this work, water-in-oil-in-water (W₁/O/W₂) emulsions were used as protective carriers to improve color stability of a hydrophilic Sambucus nigra L. extract against pH changes. The chemical system comprised water and corn oil as the aqueous and oil phases, respectively, and polyglycerol polyricinoleate (PGPR), Tween 80, and gum Arabic as stabilizers. The primary emulsion was prepared using a W₁/O ratio of 40/60 (v/v). For the secondary emulsion, W₁/O/W₂, different (W₁/O)/W₂ ratios were tested with the 50/50 (v/v) formulation presenting the best stability, being selected as the coloring system to test in food matrices of different pH: natural yogurt (pH 4.65), rice drink (pH 6.01), cow milk (pH 6.47), and soy drink (pH 7.92). Compared to the direct use of the extract, the double emulsion solution gave rise to higher color stability with pH change and storage time, as corroborated by visual and statistical analysis.     

Stereochemistry and some synthetic uses of the heteroarylation of phospholes

Further studies have been conducted on the condensation of electron-rich arenes or heteroarenes with the dienic system of phosphole P-complexes. According to the X-ray crystal structure analysis of one of the resulting 2-aryl-3-phospholene P-complexes, the condensation takes place on the side of the diene opposite to the complexing group. The decomplexation of the phospholene P–Mo(CO)₅ and P–W(CO)₅ complexes, respectively, by reaction with sulfur or halogens and tertiary amines yields the corresponding P-sulfides and oxides with full retention of the stereochemistry at phosphorus. Double condensation of the phosphole P-complexes onto the 2 and 5 positions of thiophene and furan ultimately leads to phosphole–thiophene–phosphole and phosphole–furan–phosphole chains. The first type has been characterized by X-ray crystal structure analysis of its P,P-disulfide. No electronic delocalization appears to take place along the chain.     

Kinetics of methylation of a solvatochromic vinylogous α‐pyridone in different solvents

The kinetics of the reaction with iodomethane of the solvatochromic dye 4‐[2‐(N‐methyl‐4,6‐diphenylpyridiniumyl)]phenoxide 2, generated in situ from the corresponding N‐methyl‐2,4‐diphenyl‐6‐(4‐hydroxyphenyl)pyridinium salt 4, was studied in various solvents and solvent mixtures, in search of a possible correlation between its reactivity and solvatochromism in solution. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 819–825, 1999