Chelators for radioimmunotherapy: I. NMR and ab initio calculation studies on 1,4,7,10-tetra(carboxyethyl)-1,4,7,10-tetraazacyclododecane (DO4Pr) and 1,4,7-tris(carboxymethyl)-10-(carboxyethyl)-1,4,7,10-tetraazacyclododecane (DO3A1Pr)

This work describes the modification of the chelating agent 1,4,7,10-tetraazacyclododecane-N,N',N' ',N' "-tetraacetic acid (DOTA) to improve the rate of metal loading for radioimmunotherapy applications. Previous ab initio calculations predicted that the compounds 1,4,7,10-tetra(carboxyethyl)-1,4,7,10-tetraazacyclododecane (DO4Pr) and 1,4,7-tris(carboxymethyl)-10-(carboxyethyl)-1,4,7,10-tetraazacyclododecane (DO3A1Pr) have a ca. 2000-fold improvement in yttrium metal loading rates compared to those of DOTA (Jang, Y. H.; Blanco, M.; Dasgupta, S.; Keire, D. A.; Shively, J. E.; Goddard, W. A., III. J. Am. Chem. Soc. 1999, 121, 6142-6151). In this study, we report the synthesis, purification, (1)H-NMR chemical shift assignments, pK(a) values, metal loading rate measurements, and additional ab initio calculations of these two compounds. The yttrium loading rates of DO3A1Pr are approximately twice those of DOTA, at pH 4.6 and 37 degrees C. The NMR data indicates that the DO4Pr analogue forms a stable type I complex but does not form a type II complex. The new ab initio calculations performed on DO4Pr and DO3A1Pr indicate that the rate-determining step is the deprotonation of the first macrocycle amine proton, not the second proton as assumed in the previous calculations. The new calculations predict an improvement in the rate of metal loading that more closely matches the experimentally observed change in the rate.     

Condensed cyclic and bridged-ring systems : part 12: A novel synthetic route to 4-p-methoxyphenyl-bicyclo[ 2.2.2 ]octan-2-ones and some bicyclo [ 3.2.1 ] octane derivatives by acid-catalyzed intramolecula

The efficacy of a new acid-catalyzed intramolecular C-alkylation has been demonstrated by the synthesis of 1-methyl-4-$\text{p}$-methoxyphenylbicyclo [2.2.2] octan-2-one ($\text{5}$) and 4-$\text{p}$-methoxyphenylbicyclo [2.2.2] octan-2-one ($\text{6}$) from easily accessible starting materials. The carbinol $\text{20}$, derived from $\text{5}$, undergoes facile rearrangement leading to 1-$\text{p}$-methoxyphenyl-4-methyl bicyclo [3.2.1] oct-3-ene ($\text{22}$), which has been transformed to $\text{endo}$-1-$\text{p}$-methoxyphenyl-4-methylbicyclo [3.2.1] octan-3-one ($\text{25}$).     

High performance optical absorbance detectors based on low noise switched integrators

Optical absorption detection is the most common analytical measurement principle in liquid phase analysis. The current state-of-the-art of commercially available detectors exhibit peak-to-peak (p-p) noise levels in the range of 1 x 10(-5)-2 x 10(-5) absorbance units (10-20 microAU). Using circuitry based on newly available switched integrator integrated circuit (IC) packages, it is possible to construct inexpensive absorbance detectors with p-p noise levels as low as 3 microAU under actual use conditions. The necessary electronics are described and performance data are reported with light emitting diodes (LEDs) as light sources. Even in the capillary format with a rectangular capillary (50 x 1000 microm cross section) with a slitwidth <50 microm and with the 1000 microm dimension as the nominal pathlength, p-p noise levels of 10 microAU are observed, from which a concentration limit of detection (LOD) of 10 nM for bromothymol blue (BTB) can be estimated with a 660 nm light source.     

Dislocation driven chromium precipitation in Fe-9Cr binary alloy: a positron lifetime study

The influence of initial heat treatment on anomalous Cr precipitation within high temperature solubility region of the Fe–9Cr alloy has been investigated using positron lifetime studies. Air-quenched samples with pre-existing dislocations exhibited a distinct annealing stage in positron lifetime between 800 and 1100?K corresponding to Cr-precipitation. During this stage, Transmission Electron Microscopy showed fine precipitates of average size 4 nm, dispersed throughout the sample and from Energy-dispersive X-ray spectroscopy (EDS) analysis they are found to be Cr-enriched. The presence of dislocations is found to be responsible for Cr precipitation.     

Interconnectivity between Surface Reactivity and Self-Assembly of Kemp Elimination Catalyzing Nanorods

Understanding the fundamental facts behind dynamicity of catalytic processes has been a longstanding quest across disciplines. Herein, we report self-assembly of catalytically active gold nanorods that can be regulated by tuning its reactivity towards a proton transfer reaction at different pH. Unlike substrate-induced templating and co-operativity, the enhanced aggregation rate is due to alteration of catalytic surface charge only during reactivity as negatively charged transition state of reactant (5-nitrobenzisoxazole) is formed on positively charged nanorod while undergoing a concerted E2-pathway. Herein, enhanced diffusivity during catalytic processes might also act as an additional contributing factor. Furthermore, we have also shown that nanosized hydrophobic cavities of clustered nanorods can also efficiently accelerate the rate of an aromatic nucleophilic substitution reaction, which also demonstrates a catalytic phenomenon that can lead to cascading of other reactions where substrates and products of the starting reactions are not directly involved.     

Preparation of Aryl‐Substituted E‐Homoallylic Bromides from Cyclopropylcarbinol and PBr3

An expeditious synthesis of aryl substituted E‐homoallylic bromides has been accomplished by the cleavage of cyclopropylcarbinols with phosphorus tribromide.     

Antioxidative and anticarcinogenic activities of methylpheophorbide a,isolated from wheat grass (Triticum aestivum Linn.)

Methylphophorbide a (MPa) has been isolated from the ethanol extract of the wheat grass plant. Its antioxidative efficacy is evaluated by hydroxyl radical scavenging activities and reducing capacity which are significantly up regulated in comparison with aqueous extract of the plant. The compound shows iron-binding capacity where the Fe²⁺ binds with MPa by two types of binding patterns with dissociation constants 157.17 and 27.89. It has antioxidative and cytotoxic effects on HeLa and Hep G2 cells. The cancerous cell survivability decreases with increasing concentration of MPa. These findings have provided evidence for the traditional use of the wheat grass plant in the treatment of cancers, oxidative stress and iron overloaded disorders.     

Formation of bamboo-shaped carbon nanotubes on carbon black in a fluidized bed

For the first time, bamboo-shaped multiwalled carbon nanotubes, having diameter of the order of 50 nm, have been grown on carbon black in a fluidized bed in bulk amount. The activation energy for the synthesis of the product was found out to be around 33 kJ/mol in the temperature range of 700−900 °C. The carbon nanotubes were separated from the carbon black by preferential oxidation of the later, the temperature of which was determined by thermogravimetry. The transmission electron microscopy revealed different features of the nanotubes such as “Y” junction, bend, and catalyst filling inside the nanotubes. Small angle neutron scattering was performed on the nanotubes synthesized at different temperatures. The data were fitted into a suitable model in order to find out the average diameter, which decreases with increase in synthesis temperature. The Monte Carlo simulation predicts the same behavior. Based on the above observations, a possible growth mechanism has been predicted. The oscillation in carbon saturation value inside the catalyst in the fluidized bed has been indicated as the responsible factor for the bamboo-shaped structure.