A Zinc(II) Photocage Based on a Decarboxylation Metal Ion Release Mechanism for Investigating Homeostasis and Biological Signaling

Metal ion signaling in biology has been studied extensively with ortho‐nitrobenzyl photocages; however, the low quantum yields and other optical properties are not ideal for these applications. We describe the synthesis and characterization of NTAdeCage, the first member in a new class of Zn²⁺ photocages that utilizes a light‐driven decarboxylation reaction in the metal ion release mechanism. NTAdeCage binds Zn²⁺ with sub‐pM affinity using a modified nitrilotriacetate chelator and exhibits an almost 6 order of magnitude decrease in metal binding affinity upon uncaging. In contrast to other metal ion photocages, NTAdeCage and the corresponding Zn²⁺ complex undergo efficient photolysis with quantum yields approaching 30 %. The ability of NTAdeCage to mediate the uptake of ⁶⁵Zn²⁺ by Xenopus laevis oocytes expressing hZIP4 demonstrates the viability of this photocaging strategy to execute biological assays.     

Supercritical carbon dioxide extraction and gas chromatography–mass spectrometry analysis of Gymnema sylvestre R.Br. roots

Supercritical fluid extraction (SFE) achieves a wide range of applications since the past decade as a sustainable green technology. The present study investigates the process for producing high yield by supercritical carbon dioxide (Sc-CO₂) extraction form Gymnema sylvestre R.Br. roots. The effect of temperature and pressure on the percentage of accumulative yield is demonstrated. It is found that the highest yield is obtained at the temperature of 60°C and the pressure of 10?MPa. A proper review showed that there is a lack in the study of Sc-CO₂ extraction of this plant especially for optimization of SFE process which makes this study useful and valuable. For more benefit, the extract which achieves highest percentage is subjected to gas chromatography–mass spectrometry to study its chemical composition and detect the active principle compounds which present with high concentration and expected to be responsible of the pharmaceutical properties of the extract.     

Antibacterial cotton fabrics with in situ generated silver and copper bimetallic nanoparticles using red sanders powder extract as reducing agent

Using aqueous extraction of red sanders powder as a reducing agent, silver and copper bimetallic nanoparticles were in situ generated in cotton fabrics. Silver and copper nanoparticles were also generated separately for comparison. The resulted nanocomposite cotton fabrics (NCFs) were characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and antibacterial tests. SEM analysis indicated the generation of more number of nanoparticles when bimetallic source solutions were used. Further, the size range of the generated bimetallic nanoparticles was found to be lower than when individual metal nanoparticles were generated in NCFs. XRD analysis confirmed the in situ generation of silver and copper nanoparticles when equimolar bimetallic salt source solutions were utilized. The NCFs with bimetallic nanoparticles exhibited higher antibacterial activity against both Gram-negative and Gram-positive bacteria and hence can be considered for applications as antibacterial bed and dressing materials.     

Overtone spectroscopy of some benzaldehyde derivatives

Overtone spectrum of o, m and p-nitrobenzaldehydes and p-chlorobenzaldehyde has been studied in 2000–12000 cm⁻¹ region. Vibrational frequencies and anharmonicity constants for aryl as well as alkyl CH stretch vibrations have been determined. We have also determined the internuclear distances for the aryl CH bond in the different molecules. The small variation observed in these distances is an indication of the substitution effect. It is observed that in the case of p-disubstituted benzens, the shift in aryl CH bond is proportional to sum of the Hammet σ of the substituents. However in the case of o-disubstituted benzenes it is only 80% of the para-substituted shift.     

A solution of the DGLAP equation for gluon at low x

We obtain a solution of the DGLAP equation for the gluon at low x first by expanding the gluon in a Taylor series and then using the method of characteristics. We test its validity by comparing it with that of Glück, Reya and Vogt. The convergence criteria of the approximation used are also discussed. We also calculate εF ₂(x,Q)²/ε In Q ² using its approximate relations with the gluon distribution at low x. The predictions are then compared with the HERA data.     

X-ray photoelectron spectroscopy investigations of Si in non-stoichiometric SiNx LPCVD multilayered coatings

Si nanocrystals were formed in the non-stoichiometric Si-enriched SiN_x low-pressure chemical vapor deposited (LPCVD) coatings on Si wafers treated by various modes. The coating structure as a function of technological conditions was investigated by ellipsometry and X-ray photoelectron spectroscopy (XPS) depth profiling. It was found that nanocomposites on base of SiN_x films enriched by Si have a complex multilayered structure varying in dependence of deposition and annealing parameters. Analysis of the XPS spectra and Si 2s peaks shows the existence and quantity of four chemical structures corresponding to the Si–O, Si–N states, nanocrystalline and amorphous Si. The XPS results show evolution of the chemical structure of silicon nitride and formation of Si nanocrystals. It was found:

• The LPCVD technology of nanocrystals formation allows to get enough high concentration of Si nanocrystals on different depths from the sample surface.

• The volume fraction of nanocrystalline and amorphous Si is changed with depth; this relation depends from SiN_x composition and annealing parameters.

• XPS detects these two phase compositions of Si nanoparticles in SiN_x and SiO₂ layers. The ellipsometry, HR-TEM, and XPS results are in good agreement.

Crystallization of hydrogenated amorphous silicon carbon films with laser and thermal annealing

The crystallization of silicon rich hydrogenated amorphous silicon carbon films prepared by Plasma Enhanced Chemical Vapor Deposition technique has been induced by excimer laser annealing as well as thermal annealing. The excimer laser energy density (E_d) and the annealing temperature were varied from 123 to 242 mJ/cm² and from 250 to 1200 °C respectively. The effects of the two crystallization processes on the structural properties and bonding configurations of the films have been studied. The main results are that for the laser annealed samples, cubic SiC crystallites are formed for E_d ≥ 188 mJ/cm², while for the thermal annealed samples, micro-crystallites SiC and polycrystalline hexagonal SiC are observed for the annealing temperature of 800 and 1200 °C respectively. The crystallinity degree has been found to improve with the increase in the laser energy density as well as with the increase in the annealing temperature.     

Multiple ionization of argon in coincidence with projectile ions in 60–120 MeV Si q+-Ar collisions

A projectile ion-recoil ion coincidence technique has been employed to study the multiple ionization and the charge transfer processes in collisions of 60–120 MeV Si ^q+ (q = 4−14) ions with neutral argon atoms. The relative contribution of different ionization channels, namely; direct ionization, electron capture and electron loss leading to the production of slow moving multiply charged argon recoil ions have been investigated. The data reported on the present collision system result from a direct measurement in the considered impact energy for the first time. The total ionization cross-sections for the recoil ions are shown to scale as q ^1.7/E _p ^0.5 , where E _p is the energy in MeV of the projectile and q its charge state. The recoil fractions for the cases of total- and direct ionizations are found to decrease with increasing recoil charge state j. The total ionization fractions of the recoils are seen to depend on q and to show the presence of a ‘shell-effect’ of the target. Further, the fractions are found to vary as 1/j ² upto j = 8+. The average recoil charge state 〈j〉 increases slowly with q and with the number of lost or captured electrons from or into the projectile respectively. The projectile charge changing cross-sections σ _qq′ are found to decrease with increasing q for loss ionization and to increase with q for direct-and capture ionization processes respectively. The physics behind various scaling rules that are found to follow our data for different ionization processes is reviewed and discussed.     

Structural characterization by chromatographic profiling of the oligosaccharides of human immunodeficiency virus (HIV) recombinant envelope glycoprotein gp120 produced in Chinese hamster ovary cells

This report together with the paper by T. Mizuochi, M. W. Spellman, M. Larkin, J. Solomon, L. J. Basa and T. Feizi (1988) Biochem. J. 254, 599-603 describes the structural elucidation of the N-linked oligosaccharides of the HIV envelope glycoprotein, gp120 (cloned from the HTLV-III B isolate and expressed as a secreted fusion protein after transfection of Chinese hamster ovary cells), which is known to bind with high affinity to human T4 lymphocytes. Oligosaccharides were released from peptide by hydrazinolysis, fractionated by paper electrophoresis, high performance lectin affinity chromatography and Bio-Gel P-4 column chromatography, and their structures determined by sequential exoglycosidase digestions in conjunction with methylation analysis. The glycoprotein was found to be unique in its diversity of oligosaccharide structures. These include high-mannose type and hybrid type, as well as four categories of complex type chains: mono-, bi-, tri- and tetra-antennary, with or without N-acetyllactosamine repeats, and with or without a core region fucose residue. Among the sialidase-treated oligosaccharides no less than 29 structures were identified as follows: (formula; see text) where G = galactose; GN = N-acetylglucosamine; M = mannose; F = fucose; +/- = residues present in a proportion of chains. The actual number of oligosaccharide structures is much greater since before desialylation there was evidence that among the hybrid and complex type chains all but 6% contained sialic acid at the C-3 position of terminal galactose residues, and partially sialylated forms of the bi- and multiantennary chains were present.     

Zinc(II) mediated imine-enamine tautomerization

Reduction of imine-anthracenone compounds selectively produces secondary alcohols leaving the external imine group unreacted. Addition of the Zn(II) ion induces a metal-mediated imine-enamine tautomerization reaction that is selective for Zn(II), a new fluorescence detection method not previously observed for this important cation.