Selective one-pot synthesis of substituted pyrrole-3-phosphonates from α-cyanomethyl-β-ketoesters

A one-step synthesis of 5-alkoxypyrrole-3-phosphonates is presented starting from suitable α-cyanomethyl-β-ketophosphonates. The key step in the synthesis involves a one-pot addition and heteroannulation sequence. The zinc perchlorate-catalyzed addition of alcohols to the nitrile carbon of α-cyanomethyl-β-ketophosphonates followed by annulation furnished 5-alkoxypyrrole-3-phosphonates. The addition-annulation process is carried out in the presence of water and 4,5-dihydro-5-oxo-1H-pyrrole-3-phosphonates (pyrrolinones) are obtained in good yields.     

Repetition Pitch glide from the step pyramid at Chichen Itza

Standing at the foot of the Mayan step pyramid at Chichen Itza in Mexico, one can produce a pitchy "chirp" echo by handclapping. As exposed by Declercq et al. [J. Acoust. Soc. Am. 116, 3328-3335 (2004)], an acoustic model based on optical Bragg diffraction at a periodic structure cannot explain satisfactorily the chirp-echo sonogram. Alternatively, considering the echo as a sequence of reflections, and given the dimensions of the pyramid and source-receiver position, the chirp is predicted correctly as a Repetition Pitch glide of which the pitch height is continuously decreasing within 177 ms from 796 to 471 Hz-equivalent.     

Heparin coating of poly(ethylene terephthalate) decreases hydrophobicity, monocyte/leukocyte interaction and tissue interaction

Woven poly(ethylene terephthalate) (PET) is widely used in implantable medical devices. Upon implantation, fibrinogen interacts with the PET and changes conformation, such that the fibrinogen P2 epitope may become exposed. This allows inflammatory cells to interact with the material. In this study we have coated PET with heparin and show that this decreases PET hydrophobicity and the presence of the fibrinogen P2 epitope on the material surface. In addition, we show that heparin-induced reduction of PET hydrophobicity correlates with decreased exposure of the fibrinogen P2 epitope and reduced adhesion of monocytes. Reduction of PET hydrophobicity was furthermore associated with reduced PMN elastase production and decreased interaction between PET and embryonic chicken tissue. We conclude that the heparin coating-induced decrease in PET hydrophobicity is associated with decreased interaction between PET and inflammatory cells. Independent of this interaction, the hydrophobic nature of the heparin coating is related to tissue interaction as demonstrated by a reduction in adhesion, growth and spreading of tissue on PET. The combination of these properties makes heparin coating a candidate for improving biocompatibility of PET.     

Does bisphenol A bioaccumulate on zebrafish? Determination of tissue bisphenol A level

Bisphenol A (BPA) is a high-production-volume industrial chemical mainly used in the production of polycarbonates and epoxy resins utilized in the manufacture of containers, bottles, toys, and medical devices. It has systemic effects as an endocrine disruptor even at low doses. To analyze its quantity in biological materials, sensitive and reproducible methods have to be used. Different doses and duration (90 and 900 μg/L, 24 and 120 h, and 21 days) of BPA exposure to whole body zebrafish were analyzed after specific homogenization of tissue, and then a modified method HPLC was used. The mobile phase was acetonitrile and water using a gradient method of reversed-phase C18 column, and excitation = 227 nm/emission = 313 nm. The calibration curve for BPA using HPLC-fluorescence detection method was between a concentration range of 1 and 1000 ng/mL and linear, and r² = 0.999. The mean and standard error of mean values were 4.29 ± 1.05, 2.50 ± 0.92, and 2.53 ± 0.68 for control; 10.43 ± 2.61, 11.46 ± 3.24, and 8.55 ± 3.11 for BPA-90 μg/L; and 17.78 ± 4.39, 21.55 ± 4.37, and 25.32 ± 3.25 for BPA-900 μg/L (24 h, 120 h, and 21 days, respectively). Although some statistical significance among dose/time was observed between two different dose-treated groups, statistical significance was not found in dose/time results within the group. However, the positive result of BPA in the control group can be explained by low-dose, chronic exposure or prevalence of endocrine-disrupting chemicals.     

Preparation and characterization of surface modified γ-Fe2O3 (maghemite)-silica nanocomposites used for the purification of benzaldehyde lyase

γ-Fe₂O₃ (maghemite)-silica nanocomposite particles were synthesized using a sol-gel method. The condensation products of 3-glycidoxy propyltrimethoxy silane (GPTMS) and nitrilotriacetic acid (NTA) were introduced onto the surfaces of the γ-Fe₂O₃-silica nanocomposite particles and subsequently, these modified surfaces were complexed with cobalt (Co⁺²) metal ions. A possibility of using these surface modified γ-Fe₂O₃-silica particles for the purification of 6×histidine tagged recombinant benzaldehyde lyase (BAL, EC 4.1.2.38) based on magnetic separation was investigated. X-ray diffraction (XRD), thermal analysis, and vibrating sample magnetometry (VSM) methods were used to characterize the surface modified superparamagnetic γ-Fe₂O₃ (maghemite)-silica nanoparticles. XRD (Scherer's equation) results indicate that the primary particle size of maghemite was around 11 nm. Magnetic characterization results confirmed that the γ-Fe₂O₃ (maghemite)-silica nanoparticles were superparamagnetic. According to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) results, these superparamagnetic nanoparticles specifically capture 6×His-tagged BAL from crude extract of Escherichia coli (E. coli) BL21(DE3)pLysS/BAL_HIS. This study shows that the surface modified γ-Fe₂O₃ (maghemite)-silica nanoparticles are eligible for immobilized metal-ion affinity adsorption for histidine tagged recombinant proteins with its high capacity (3.16±0.4 mg/g) and selectivity.     

Size and sequence and the volume change of protein folding

The application of hydrostatic pressure generally leads to protein unfolding, implying, in accordance with Le Chatelier's principle, that the unfolded state has a smaller molar volume than the folded state. However, the origin of the volume change upon unfolding, ΔV(u), has yet to be determined. We have examined systematically the effects of protein size and sequence on the value of ΔV(u) using as a model system a series of deletion variants of the ankyrin repeat domain of the Notch receptor. The results provide strong evidence in support of the notion that the major contributing factor to pressure effects on proteins is their imperfect internal packing in the folded state. These packing defects appear to be specifically localized in the 3D structure, in contrast to the uniformly distributed effects of temperature and denaturants that depend upon hydration of exposed surface area upon unfolding. Given its local nature, the extent to which pressure globally affects protein structure can inform on the degree of cooperativity and long-range coupling intrinsic to the folded state. We also show that the energetics of the protein's conformations can significantly modulate their volumetric properties, providing further insight into protein stability.     

A central spectrum theory of binaural processing. The binaural edge pitch revisited

Recently, Klein and Hartmann [J. Acoust. Soc. Am. 70, 51-61 (1981)] investigated a new dichotic pitch, called the binaural edge pitch (BEP). They used computer-generated periodic noise signals to generate BEP. In the study presented here, the BEP is investigated in order to evaluate the predictions of the central spectrum theory with regard to this stimulus. Pitch-matching experiments using a nonperiodic BEP stimulus, produced by means of a modulation technique, led to the conclusion that the strongest pitch sensation in the BEP has the character of a weak fluctuating pure tones in noise, which corresponds to a frequency, equal or almost equal to the frequency of the phase transition. This result fits in with the predictions of the central spectrum theory, which, for instance, does not need the assumption of central lateral inhibition for explaining this pitch. Furthermore, it is shown that this theory can also predict the results obtained in lateralization measurements and BMLD measurements using BEP stimuli as well as related stimuli. The results are compared with the data obtained by Klein and Hartmann.     

Modeling the propagation of electromagnetic waves over the surface of the human body

The results of modeling and an experimental study of electromagnetic (EM) waves in microwave range propagating along the surface of the human body have been presented. The parameters of wave propagation, such as the attenuation and phase velocity, have also been investigated. The calculation of the propagation of EM waves by the numerical method FDTD (finite difference time domain), as well as the use of the analytical model of the propagation of the EM wave along flat and curved surfaces has been fulfilled. An experimental study on a human body has been conducted. It has been shown that creeping waves are slow and exhibit a noticeable dispersion, while the surface waves are dispersionless and propagate at the speed of light in free space. A comparison of the results of numerical simulation, analytical calculation, and experimental investigations at a frequency of 2.55 GHz has been carried out.