Mass spectrometric characterization of two novel inflammatory peptides from the venom of the social wasp Polybia paulista

The social wasp P. paulista is relatively common in southeast Brazil causing many medically important stinging incidents. The seriousness of these incidents is dependent on the amount of venom inoculated by the wasps into the victims, and the characteristic envenomation symptoms are strongly dependent on the types of peptides present in the venom. In order to identify some of these naturally occurring peptides available in very low amounts, an analytical protocol was developed that uses a combination of reversed-phase and normal-phase high-performance liquid chromatography (HPLC) of wasp venom for peptide purification, with matrix-assisted laser desorption/ionization time-of-flight post-source decay mass spectrometry (MALDI-Tof-PSD-MS) and low-energy collision-induced dissociation (CID) in a quadrupole time-of-flight tandem mass spectrometry (QTof-MS/MS) instrument for peptide sequencing at the sub-picomole level. The distinction between Leu and Ile was achieved both by observing d-type fragment ions obtained under CID conditions and by comparison of retention times of the natural peptides and their synthetic counterparts (with different combinations of I and/or L at N- and C-terminal positions). To distinguish the isobaric residues K and Q, acetylation of peptides was followed by Q-Tof-MS analysis. The primary sequences obtained were INWLKLGKMVIDAL-NH(2) (MW 1611.98 Da) and IDWLKLGKMVMDVL-NH(2) (MW 1658.98 Da). Micro-scale bioassay protocols characterized both peptides as presenting potent hemolytic action, mast cell degranulation, and chemotaxis of polymorphonucleated leukocyte (PMNL) cells. The primary sequences and the bioassay results suggest that these toxins constitute members of a new sub-class of mastoparan toxins, directly involved in the occurrence of inflammatory processes after wasp stinging.     

Calorimetric study on the temperature dependence of the formation of mixed ionic/nonionic micelles

The differential excess enthalpy of mixed micelle formation was measured at different temperatures by mixing nonionic hexa(ethylene glycol) mono n-dodecyl ether with anionic sodium dodecyl sulfate or cationic dodecylpyridinium chloride. The experimental data were obtained calorimetrically by titrating a concentrated surfactant solution into a micellar solution of nonionic surfactant. The composition and the size of the mixed nonionic/ionic micelles at different surfactant concentrations were also determined. Pronounced differences in both composition and excess enthalpy were found between the anionic and the cationic mixed system. For both systems, the excess enthalpies become more exothermic with increasing temperature, but for the anionic mixed system an additional exothermic contribution was found which was much less temperature dependent. Temperature dependence of the excess enthalpy was attributed to the effect of the ionic headgroup on the hydration of the ethylene oxide (EO) groups in the mixed corona. Ionic headgroups located in the ethylene oxide layer cause the dehydration of the EO chains resulting in an additional hydrophobic contribution to the enthalpy of mixing. A high affinity of sodium dodecyl sulfate for nonionic micelles and an extra exothermic and less temperature dependent contribution to the excess enthalpy found for the SDS-C(12)E(6) system might be attributed to specific interactions (hydrogen bonds) between the sulfate headgroup and the partly dehydrated EO chain.     

Nanotubes fabricated from Ni-naphthalocyanine by a template method

Novel naphthalocyanine (Nc) nanotubes with special wall structures were fabricated by a template method using Nc molecules as building blocks. Thermal stabilization of the ordered columnar structures of the tetrakis(tert-butyl)naphthalocyanine (Ni-BNc) molecules, induced from the pi-pi interactions in the nanoscale channels of an alumina template, resulted in Nc nanotubes with walls consisting of well-ordered Nc molecular disks. Further thermal treatment of Ni-BNc at 600 degrees C produced carbonized Nc nanotubes containing ordered columnar, graphitic wall structures with the graphene disks arranged perpendicular to the tube axis. These nanotubes may be useful for extending the application of Nc molecules for nanodevice fabrication.     

EFFECT OF METAL IONS ON THE LUMINESCENCE OF ACRIDINE DYES BOUND TO DNA

Abstract— The luminescence of acridine dyes intercalated in DNA was studied as a function of the concurrent binding of metal ions to DNA, in an effort to deduce specific site interactions of the dyes. Two dyes, proflavine (PF) and acridine orange (AO), and two metal ions, silver and mercuric, were used. Both ions quench the fluorescence of the dyes in aqueous solution at room temperature. The metal ions have a different effect on the fluorescence of these dyes when they are intercalated between the base pairs of DNA. The fluorescence of AO is decreased when silver is bound, while the fluorescence of PF is enhanced. Since Ag⁺ initially binds to GC sites in DNA, which quench the PF fluorescence, it ostensibly 'turns off' the quenching by DNA at these sites, and this effect is greater than the quenching effect of the silver ion itself. Hg²⁺ ion initially binds to AT sites in DNA. Since both dyes fluoresce from AT sites, Hg²⁺ is expected to quench their fluorescence. This behavior is observed at low r (metal ion/base). At higher r values, however, where Hg²⁺ is expected to begin binding to GC sites, the fluorescence of PF is enhanced. These quenching turn-off effects are tentatively interpreted in terms of a change in the structure of the dye/DNA complex which occurs when a metal ion binds at the intercalation site. At 77 K. no fluorescence enhancement is observed when metal ions bind; Ag⁺ quenches the fluorescence and enhances the phosphorescence of both dyes. Qualitatively similar results are obtained with Hg²⁺.     

Metal ion binding by a bicyclic diamide: deep UV Raman spectroscopic characterization

Deep UV resonance Raman spectroscopy was used for characterizing ligand-metal ion complexes. The obtained results demonstrated a strong intrinsic sensitivity and selectivity of a Raman spectroscopic signature of a bicyclic diamide, a novel chelating agent for lanthanides and actinides (Lumetta, G. J.; Rapko, B. M.; Garza, P. A.; Hay, B. P.; Gilbertson, R. D.; Weakley, T. J. R.; Hutchison, J. E. J. Am. Chem. Soc. 2002, 124, 5644). Molecular modeling, which included structure optimization and calculation of Raman frequencies and resonance intensities, allowed for assigning all strong Raman bands of the bicyclic diamide as well as predicting the band shifts observed because of complex formation with metal ions. A comparative analysis of Raman spectra and the results of the molecular modeling could be used for elucidating the structure of complexes in solution.     

Syntheses, structures, and ion-exchange properties of the three-dimensional framework uranyl gallium phosphates, Cs4[(UO2)2(GaOH)2(PO4)4].H2O and Cs[UO2Ga(PO4)2

The reaction of UO(2)(NO(3))(2).6H(2)O with Cs(2)CO(3) or CsCl, H(3)PO(4), and Ga(2)O(3) under mild hydrothermal conditions results in the formation of Cs(4)[(UO(2))(2)(GaOH)(2)(PO(4))(4)].H(2)O (UGaP-1) or Cs[UO(2)Ga(PO(4))(2)] (UGaP-2). The structure of UGaP-1 was solved from a twinned crystal revealing a three-dimensional framework structure consisting of one-dimensional (1)(infinity)[Ga(OH)(PO(4))(2)](4-) chains composed of corner-sharing GaO(6) octahedra and bridging PO(4) tetrahedra that extend along the c axis. The phosphate anions bind the UO(2)(2+) cations to form UO(7) pentagonal bipyramids. The UO(7) moieties edge-share to create dimers that link the gallium phosphate substructure into a three-dimensional (3)(infinity)[(UO(2))(2)(GaOH)(2)(PO(4))(4)](4-) anionic lattice that has intersecting channels running down the b and c axes. Cs(+) cations and water molecules occupy these channels. The structure of UGaP-2 is also three-dimensional and contains one-dimensional (1)(infinity)[Ga(PO(4))(2)](3-) gallium phosphate chains that extend down the a axis. These chains are formed from fused eight-membered rings of corner-sharing GaO(4) and PO(4) tetrahedra. The chains are in turn linked together into a three-dimensional (3)(infinity)[UO(2)Ga(PO(4))(2)](1-) framework by edge-sharing UO(7) dimers as occurs in UGaP-1. There are channels that run down the a and b axes through the framework. These channels contain the Cs(+) cations. Ion-exchange studies indicate that the Cs(+) cations in UGaP-1 and UGaP-2 can be exchanged for Ca(2+) and Ba(2+). Crystallographic data: UGaP-1, monoclinic, space group P2(1)/c, a = 18.872(1), b = 9.5105(7), c = 14.007(1) A, beta = 109.65(3)(o) , Z = 4 (T = 295 K); UGaP-2, triclinic, space group P, a = 7.7765(6), b = 8.5043(7), c = 8.9115(7) A, alpha = 66.642(1)(o), beta = 70.563(1)(o), gamma = 84.003(2)(o), Z = 2 (T = 193 K).     

Cation-cation interactions between uranyl cations in a polar open-framework uranyl periodate

Novel open-framework alkali metal uranyl periodates, having the formula A[(UO2)3(HIO6)(OH)(O)(H2O)].1.5H2O (A = Li, Na, K, Rb, Cs), have been prepared through mild hydrothermal synthesis. These isostructural compounds contain distorted UO7 pentagonal bipyramids that are linked through a uranyl (UO22+) to uranyl cation-cation interaction. This interaction arises from a single axial uranyl oxygen coordinating at an equatorial site of an adjacent uranyl unit. These uranium oxide polyhedra are further bound by IO6 distorted octahedra creating an open-framework structure whose channels contain the alkali metal cations.     

A new steroidal saponin from Agave attenuata

A new steroidal saponin was isolated from the leaves of Agave attenuata. Its structure was established as (3beta,beta,25S)-spirostan-3-yl O-beta-D-glucopyranosyl-(1 --> 2)-beta-D-glucopyranosyl-(1 --> 2)-O-[beta-D-glucopyranosyl-(1 --> 3)]-beta-D-glucopyranosyl-(1 --> 4)-beta-D-galactopyranoside. The structural identification was performed using detailed analyses of 1H- and 13C-NMR spectra including 2D NMR spectroscopic techniques (COSY, HETCOR, and COLOC) and chemical conversions. The hemolytic activity of the steroidal saponin was evaluated using an in vitro assay.     

Influence of lanthanum exchange on the catalytic properties of HY zeolite in cyclohexene transformation

Cyclohexene transformation was used as test reaction to study the effect of lanthanum exchange on the catalytic behavior of HY zeolite cracking catalysts. Lanthanum has an overall positive effect increasing both acitivity and stability of HY zeolite and maximum selectivity towards isomerization products is obtained at higher conversion.

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Demonstrating Linear Regression and Error Using an Experiment with a Microwave Oven

To provide an application for the method of linear least squares to data collected in a laboratory, a beaker with water is heated in a microwave oven, and the water temperature is measured as a function of heating variables (time and oven setting). This procedure enables a student to obtain a regression line for each oven setting, and to evaluate the intercept and slope of this line and compare them with the initial temperature of the water and the heating versus oven setting relationship described in the microwaves manufacturers manual. They also are asked to identify any sources of errors observed in this experiment.