Production of biosurfactant from a new and promising strain of Pseudomonas aeruginosa PA1

The Pseudomonas aeruginosa PA1 strain, isolated from the water of oil production in Sergipe, Northeast Brazil, wasevaluated as a potential rhamnolipid type of biosurfactant producer. The production of biosurfactants was investigated using different carbon sources (n-hexadecane, paraffin oil, glycerol, and babassu oil) and inoculum concentrations (0.0016–0.008 g/L) The best results were obtained with glycerol as the substrate and an initial cell concentration of 0.004 g/L. AC:N ratio of 22.8 led to the greatest production of rhamnolipids (1700 mg/L) and efficiency (1.18 g of rhamnolipid/g of dry wt).     

Enantiomeric separation and detection by high-performance liquid chromatography-mass spectrometry of 2-arylpropionic acids derivatized with benzofurazan fluorescent reagents

The enantiomneric separation and the detection of 2-arylpropionic acids after derivatization with the fluorescent reagents with a benzofurazan structure, ( S )-(+)-4-( N,N -dimethylaminosulphonyl)-7-(3-aminopyrrolidin-1-yl)-2,1,3-benzoxadiazole (( S )-DBD-Apy), (R)-(-)-4-nitro-7-(3-aminopyrrolidin-1-yl)-2,1,3-benzoxadiazole (( R )-NBD-Apy), 4- N,N -dimethylaminosulphonyl-7-piperazino-2,1,3-benzoxadiazole (DBD-PZ) and N -hydrazinoformylmethyl- N -methylamino-4,4- N,N -dimethylaminosulphonyl-2,1,3-benzoxadiazole (DBD-CO-Hz) by high-performance liquid chromatography (HPLC) and electrospray ionization mass spectrometry (ESI-MS) were examined. The diastereomeric derivatization with ( S )-DBD-Apy or ( R )-NBD-Apy and the separation on the reversed phase column afforded the high sensitivity. The separation on chiral stationary phase after non-chiral derivatization with DBD-PZ or DBD-CO-Hz provided less sensitivity. The signal-to-noise ratio of ( S )-DBD-Apy-( S )-ketoprofen of 200:1 was observed for 12.5 picomole (pmol) injection and selected ion monitoring (SIM) of the quasi-molecular ion after splitting 1:7 before entering into the electrospray ion sources. As a result, the usefulness of these reagents for MS detection has been demonstrated. © 1998 John Wiley & Sons, Ltd.     

Microhardness and surface free energy in linear polyethylene: The role of entanglements

The microhardness of a series of melt crystallized samples of linear polyehtylene was investigated in a wide range of molecular weights. The x-ray long period was analyzed to study the variation of the hardness-derived constantb as a function of molecular weight (M ). It is pointed out thatb offers a measure of the hardness depression due to the finite thickness of the lamellar crystals. The data obtained show that the increase and final leveling-off (forM 200 000) ofb withM parallels the concurrent increase of the surface free energy, as derived from DSC experiments. Results are discussed using the concept og chain folded lamellae as thermodynamically stable non-homogeneous microphases. Comparison of experimental and calculated data supports the view that the number of molecular entanglements, segregated onto the defective surface boundary of the heterogeneous crystals influence the shearing mechanism within the mesocrystals and thereby control the yield behavior of the material.     

Influence of a Pre-organized N-Donor Group on the Coordination of Trivalent Actinides and Lanthanides by an Aminopolycarboxylate Complexant

The thermodynamic influence of a pre-organized N-donor group on the coordination of trivalent actinides and lanthanides by an aqueous aminopolycarboxylate complexant has been investigated. The synthesized reagent, N-2-methylpicolinate-ethylenediamine-N,N′,N′-triacetic acid (EDTA-Mpic), resembles ethylenediamine-N,N,N′,N′-tetraacetic acid (EDTA) with a single acetate pendant arm replaced by a 6-carboxypyridin-2-ylmethyl group. The rigid N-donor picolinate functionality has a profound impact on ligand protonation and trivalent f element complexation equilibria, as demonstrated by potentiometric, spectroscopic, and liquid/liquid metal-partitioning studies as well as by molecular dynamics calculations. Relative to diethylenetriamine-N,N,N′,N′′,N′′-pentaacetic acid (DTPA), the ability to preferentially bind trivalent actinides over trivalent lanthanides was moderately lowered due to the presence of the N-(6-carboxypyridin-2-ylmethyl) substituent. The structural modification substantially amplifies the total ligand acidity of EDTA-Mpic. As a result the complexant sustains the metal complexation and efficient An³⁺/Ln³⁺ differentiation in aqueous mixtures of unprecedented acidity for this class of reagents.     

Tweaking the affinity of aryl‐substituted diazosalicylato‐ and pyridine ligands towards Zn (II) and its neighbors in the periodic system of the elements,Cu (II) and Cd (II), and their antimicrobial activity

A series of six new Zn (II) compounds, viz., [Zn(HL^ASA)₂(Py)₂] ( 1 ), [Zn(HL^MASA)₂(Py)₂] ( 2 ), [Zn(HL^MASA)₂(4‐MePy)₂] ( 3 ), [Zn(HL^CASA)₂(4‐MePy)₂] ( 4 ), [Zn(HL^BASA)₂(Py)₂] ( 5 ), [Zn(HL^BASA)₂(4‐MePy)₂] ( 6 ) and representative Cu (II) and Cd (II) complexes, viz., [Cu(HL^ASA)₂(Py)₂(H₂O)] ( 7 ) and [Cd(HL^BASA)₂(Py)₃] ( 8 ) [(HL^XASA)^? = para‐substituted 5‐[(E)‐2‐(aryl)‐1‐diazenyl]‐2‐hydroxybenzoate with X = H (ASA), Me (MASA), Cl (CASA) or Br (BASA); Py = pyridine; 4‐MePy = 4‐methylpyridine] have been synthesized and characterized by spectroscopic techniques and single‐crystal X‐ray diffraction analysis. The structural characterization of the compounds revealed distorted tetrahedral ( 1 – 6 ), square‐pyramidal ( 7 ) and pentagonal‐bipyramidal ( 8 ) coordination geometries around the metal atom, in which the aryl‐substituted diazosalicylate ligands are coordinated only through the oxygen atoms of carboxylate groups, either in an anisobidentate or isobidentate mode; meanwhile, the 2‐hydroxy groups of the monoanionic ligand (HL^XASA)^? are involved only in intramolecular O‐H···O hydrogen bonds with the carboxylate function. In the crystal structures of 1 – 8 , the complex molecules are assembled by π‐stacking interactions giving mostly infinite 1D strands. The intermolecular binding in the solid state structures is accomplished by diverse additional non‐covalent contacts including C‐H···O, C‐H···N, C‐H···π, C‐H···Br, O···Br, Br···π and van der Waals contacts. Although the primary and secondary ligands in the Zn (II) complex series 1 – 6 carry different substituents at the periphery (X = H, Me, Cl, Br for (HL^XASA)^? and R = H, Me for 4‐Py‐R), five of the crystal structures were isostructural. Additionally, the antimicrobial activity of the pro‐ligands H₂L^XASA and their Zn (II), Cu (II) and Cd (II) compounds were studied in a comparative manner, showing high sensitivity (IZD ≥ 20) against Bacillus subtilis.     

Study on interactions of endocrine disruptors with estrogen receptor-beta using fluorescence polarization.

In this study, we developed a rapid, simple and homogeneous human recombinant estrogen receptor-beta (hrER-beta) binding assay method using fluorescence polarization (FP) by applying a fluorescent ligand, fluorescein-labeled estradiol (F-E2). A Scatchard plot and a Hill plot analysis of the saturation binding assay using F-E2 and hrER-beta were studied. F-E2 showed a high affinity for hrER-beta, the dissociation constant was 5.53 nM, indicating that F-E2 is applicable to the hrER-beta binding assay. Competitive binding assays using F-E2, in which the FP values decreased upon the addition of compounds (competitors) were carried out to evaluate the binding characteristics of compounds with and without biological activities to hrER-beta. Twenty-one compounds, such as hormones, pharmaceuticals, industrial chemicals and phytoestrogens, were examined. The obtained sigmoidal inhibition curves were transformed into pseudo-Hill plots and the concentrations at 50% inhibition (IC50) and Hill coefficients, the degree of cooperativity in ER-ligand binding, were obtained from the regression equations. Antagonists exhibited larger Hill coefficients than agonists, showing the correlation between the Hill coefficients and the estrogenic/antiestrogenic activities.     

Fluorescent oxidation products derived from DBD-thiocarbamoyl amino acid in the modified Edman sequencing analysis

The fluorescent product obtained by the oxidation of 7-N, N-dimethylaminosulfonyl-4-(2,1,3-benzoxadiazolyl) (DBD)-thiocarbamoyl (TC)-proline with NaNO(2)/H(+) in the modified Edman sequencing procedure was identified as the corresponding thiazolyl compound, N-[(8-dimethylaminosulfonyl)thiazolo[5,4, e]benzo[2,1,3]oxadiazol-5-yl]-L-proline, formed by the attack of the sulfur atom of the thiocarbamoyl group on the benzofurazan skeleton. The reaction mechanism for the formation of the fluorescent compound from DBD-TC primary and secondary amines is also discussed.     

Preparation and evaluation of new Pirkle type chiral stationary phases with long alkyl chains for the separation of amino acid enantiomers derivatized with NBD-F.

In order to improve the high-performance liquid chromatographic separation of alpha-amino acids derivatized with the fluorogenic reagent 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) on commercially available chiral stationary phases (CSPs) such as SUMICHIRAL OA-2500(S) (CSP 1) and OA-4700 (CSP 3), the preparation of two new CSPs (CSP 2 and CSP 4) having 11-aminoundecanoic acid between the aminopropyl silica gel support and the chiral moiety in CSP 1 and CSP 3 is described. CSP 2 and CSP 4 improved both the mutual and enantiomeric separation of NBD-amino acids compared with CSP 1 and CSP 3. Thus, 17 pairs of NBD-amino acid enantiomers and NBD-glycine were separated on CSP 2 except for six NBD-amino acids (D-Asn, D-Ser, D-Gln, L-Pro, L-Ser and Gly). CSP 2 and CSP 4 also showed better enantiomeric separation of NBD-amino acid esters and amides than CSP 1 and CSP 3. It was considered that the achiral long alkyl chains in the CSPs might form a hydrophobic space which assisted the stereoselective interaction of analytes with the chiral moiety by changing the environment around the chiral moiety. On CSP 1 and CSP 2, NBD-beta-amino acid was also enantiomerically separated.     

Development of 7-(N,N-dimethylaminosulfonyl)-5-N-(4-N-aminoethyl)piperazino-2,1,3-benzoxadiazole as a water-soluble fluorogenic reagent for the sensitive liquid chromatographic determination of saturated carboxylic acids

A reversed-phase high-performance liquid chromatographic (HPLC) method for the femtomole determination of nine saturated carboxylic acids, n-butyric (C4), n-hexanoic (C6), n-caprylic (C8), n-decanoic (C10), lauric (C12), n-tetradecanoic (C14), palmitic (C16), stearic (C18) and arachidic (C20), based on the condensation reaction of these acids with a newly synthesized water-soluble benzofurazan fluorescent reagent, 7-(N,N-dimethylaminosulfonyl)-4-N-(4-N-aminoethyl)piperazino-2,1,3-benzoxadiazole (DBD-PZ-NH2), was developed. The derivatization reaction proceeds with 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide (EDC) in the presence of the catalyst 4-(dimethylamino)pyridine (DMAP). A model derivative of the reagent with n-caprylic acid (C8) was synthesized for fluorescence excitation/emission characterization. Depending on the solvents, including water, methanol, acetonitrile, 1,4-dioxane or N.N-dimethyformamide (DMF), the C8 derivative has a fluorescence emission with a fluorescence quantum yield (phi) ranging from 0.01 to 0.20 in the region from 545 to 580 nm. An exponential increase in phi was observed with increasing acetonitrile content. The calculated detection limits (signal-to-noise ratio = 3:1) of the proposed method for the above nine carboxylic acids were 9.1, 4.0, 2.5, 2.2, 2.0, 1.8, 1.2, 1.0 and 1.3 fmol, respectively. Biological samples including Intralipos 20% and rat plasma were analysed satisfactorily.