Synthesis and aggregational behavior of acidic proteinoid

Polypeptide-based acidic proteinoid containing L -glutamic acid and L -aspartic acid in excess and five other neutral and basic amino acids in minor proportions have been synthesized and found that it forms organized aggregates in an aqueous solution. The proteinoid aggregate has been characterized using ¹³C-NMR, IR, and fluorescence spectroscopic techniques. The c.m.c. of the proteinoid has been determined by conductometric and pH metric methods. The aggregation studies were carried out at different temperatures and varying ionic strengths of the medium. The phase transition of the proteinoid aggregate has been determined using the fluorescence absorbance method. The aggregation behavior is shown to be dependent on the pH of the solution. This was also supported by conductivity measurements. Using methylene blue as a model drug, the drug delivery property of the proteinoid micelles were studied in acidic (pH 4.5) and neutral (pH 7.4) mediums. Using biphasic model thermochemical parameters, ΔG, ΔH, ΔS, and ΔC_p have been evaluated. © 1996 John Wiley & Sons, Inc.     

P and Al NMR study of Al1−xGaxPO4

Mixed phosphates Al_1−xGa_xPO₄ (0.0≤x≤1.0), with orthorhombic structure, have been prepared by co-precipitation method followed by annealing at high temperature (T≈1350 °C) and investigated by using powder X-ray diffraction and NMR spectroscopy. A systematic decrease observed for the unit cell parameters with increasing Ga³⁺ contents, suggests the formation of a solid solution between AlPO₄ and GaPO₄. ³¹P MAS NMR spectra of both AlPO₄ and GaPO₄ show a single peak at δ=−24.6 and −8.5 ppm, respectively. For mixed phosphates, multi-component ³¹P NMR spectra characterized by varying values of chemical shifts, have been observed due to the existence of different types of ³¹P structural configurations formed by varying number of Al³⁺ and Ga³⁺ as its next nearest neighbours. The intensity analysis of these component peaks suggested a perfectly random distribution of Al³⁺ and Ga³⁺ cations in these mixed phosphates. Chemical shift anisotropy parameters for the different structural configurations of ³¹P have been evaluated from the intensity analysis of the spinning side bands corresponding to different isotropic peaks. ²⁷Al NMR spectra of mixed phosphate samples exhibited a slightly asymmetric broad peak at δ≈42.0 ppm, which is characteristic of the tetrahedral configuration of Al³⁺ ions with significant covalent bonding between the metal and oxygen ions.     

Void-fraction measurements in a steady-state mercury-nitrogen flow loop

 A steady-state vertical mercury-nitrogen flow system has been investigated using three tomographic algorithms. Void-fraction profiles have been reconstructed by the data collected by a 60 mCi gamma-ray source and a single Na(Tl) detector. The results indicate excellent agreement (within ±1%) between the least-squares-solution and the chord-segment-inversion algorithms. The data-collection time for each data-ray was varied so that in each case 3000 counts could be collected to reduce the detrimental effect of Poisson statistics in the reconstructed profiles. Eleven sets of data have been collected for nitrogen flow-rates between 0.00123 and 0.00884  kg/s. The mercury flow-rates were between 17.6 and 34.1 kg/s. The resulting cross-sectional average void varied between 0.10 and 0.38. Received: 13 March 1997/Accepted: 12 September 1997     

Rigidity of minimal surfaces inS 3

Isometric deformations of compact minimal surfaces in the standard three-sphere are studied. It is shown that a given surface admits only finitely many noncongruent minimal immersions intoS ³ with the same first fundamental form.     

Generation of stable mixed-compact-toroid rings by inducing plasmacurrents in strong E rings

In the RECE-Christa device, hybrid-type compact toroid rings are generated by inducing large toroidal plasma currents I_p in strong electron rings using a thin induction coil positioned along the ring axis. Starting from field-reversal values δ_p =50-120% of the original pure fast-electron ring, the induced plasma current I_p raises δ to a maximum value of up to 240% with I_p contributing more than 50% of the total ring current. The generated hybrid compact toroid configurations appear gross-stable during the full I_p pulse length (half-amplitude width about 100 μs)     

Folate-receptor-mediated delivery of InP quantum dots for bioimaging using confocal and two-photon microscopy

A novel method for the synthesis of highly monodispersed hydrophillic InP-ZnS nanocrystals and their use as luminescence probes for live cell imaging is reported. Hydrophobic InP-ZnS nanocrystals are prepared by a new method that yields high-quality, luminescent core-shell nanocrystals within 6-8 h of total reaction time. Then by carefully manipulating the surface of these passivated nanocrystals, aqueous dispersions of folate-conjugated nanocrystals (folate-QDs) with high photostability are prepared. By use of confocal microscopy, we demonstrate the receptor-mediated delivery of folic acid conjugated quantum dots into folate-receptor-positive cell lines such as KB cells. These folate-QDs tend to accumulate in multi-vescicular bodies of KB cells after 6 h of incubation. Receptor-mediated delivery was confirmed by comparison with the uptake of these particles in folate-receptor-negative cell lines such as A549. Efficient two-photon excitation of these particles and two-photon imaging using these particles are also demonstrated. The use of these InP-ZnS nanoparticles and their efficient two-photon excitation can be potentially useful for deep tissue imaging for future in vivo studies.     

Simple and efficient methods of synthesis of 3,3-diarylcyclobutanone and 3,3-diarylcyclobutylamine derivatives using the TiCl4/R3N reagent system

[reaction: see text] The iminium ions generated in situ by the oxidation of N,N-diisopropyl-N-benzylamine using iodine react with diaryl ketones in the presence of TiCl4/R3N to give the corresponding 3,3-diarylcyclobutanones in moderate to good yields (49-86%). The 3,3-diarylcyclobutanone iminium ions formed in this transformation was reduced in situ with B2H6 to produce the corresponding 3,3-diarylcyclobutylamines (52-79% yields), a class of compounds with potential antidepressant activity. In addition, a series of N,N-dimethyl-3,3-diarylcyclobutylamines were synthesized by the reductive amination of the corresponding 3,3-diarylcyclobutanone derivatives.     

Dendrimers based on a three-dimensionally disposed AB4 monomer

[reaction: see text] Design and synthesis of a novel class of dendrons based on an AB(4) monomer are described. These dendrons have been evaluated by using dendritic encapsulation of a redox active core. The electrochemical properties of symmetric ferrocene-cored dendrimers show that significant alterations in redox potential and heterogeneous electron-transfer rate constants could be achieved even at lower generations.     

Neutron diffraction studies on Ca1−x Ba x Zr4P6O24 solid solutions

Herein we report the results of detailed crystallographic studies of Ca_1−x Ba _x Zr₄P₆O₂₄ compositions from combined Rietveld refinements of powder X-ray and neutron diffraction data. All the studied compositions crystallize in rhombohedral lattice (space group R-3 No. 148). A continuous solid solution is concluded from the systematic variation of unit cell parameters. The variation of unit cell parameters with the composition indicates decreasing trend in a parameter with increasing Ba2+ concentration contrast to an increasing trend in c parameter.      

The leaving group dependence in the rates of solvolysis of 1,2‐diphenylethyl system

1,2‐Diphenylethyl chloride undergoes solvolysis by S_N1 mechanism in aqueous organic solvents. The α‐phenyl group of 1,2‐diphenylethyl chloride enters into conjugation with the developing carbocationic centre. The β‐phenyl group on the other hand was unable to extend its conjugation via neighbouring group participation due to steric inhibition of resonance in the formation of non‐classical carbocation. 1,2‐Diphenylethyl chloride thus behaves similar to 1‐phenylethyl chloride in its solvolysis pattern. The solvolytic rate studies of chloride and methanesulphonate of 1,2‐diphenylethyl alcohol in various aqueous organic solvents show that the dispersion observed in the Winstein–Grunwald plot is not due to a change in leaving group but due to the difference in solvation requirements of aromatic and aliphatic groups. Copyright © 2010 John Wiley & Sons, Ltd.