Dendrimer-activated surfaces for high density and high activity protein chip applications

Highly functional Si and glass surfaces for protein immobilization have been prepared by a facile activation of native surface silanol groups. Poly(propyleneimine) dendrimers of generations 1-5 were immobilized onto the surface using a facile room-temperature coupling procedure that involved activation of native silanol groups of glass using 1,1'-carbonyldiimidazole under anhydrous conditions. The dendrimer-coated surfaces were used to immobilize proteins and were characterized with respect to surface loading and activity. A number of different chemical, physical, and biochemical techniques including contact angle measurement, ellipsometry, and fluorescence microscopy were used to characterize the resulting surfaces. Increasing the dendrimer generation past G-3 led to increased surface amine content, immobilized protein concentration, and the activity of immobilized alkaline phosphatase (used as a test system). Very high activity of the immobilized proteins in the case of higher generation (G-4 and G-5) dendrimers led us to conclude that such an approach has true potential for creating highly functional surfaces for protein chip applications.     

Momentum-space properties from coordinate-space electron density

Electron density and electron momentum density, while independently tractable experimentally, bear no direct connection without going through the many-electron wave function. However, invoking a variant of the constrained-search formulation of density-functional theory, we develop a general scheme (valid for arbitrary external potentials) yielding decent momentum-space properties, starting exclusively from the coordinate-space electron density. A numerical illustration of the scheme is provided for the closed-shell atomic systems He, Be, and Ne in their ground state and for 1s(1) 2s(1) singlet electronic excited state for helium by calculating the Compton profiles and the expectation values derived from given coordinate-space electron densities.     

Enthalpies of mixing of di- n -butyl ether with isomeric butanols: Enthalpies of hydrogen-bonded complexes

The enthalpies of mixing of four isomeric butanols with di-n-butyl ether were determined at 30°C by a Calvet type microcalorimeter. All the four systems showed endothermic behaviour. The enthalpies of complex formation were calculated by the thermochemical cycle. The strength of H-bonding decreases in the order l-butanol, l-methyl-1-propanol, 2-methyl-2-propanol, 2-butanol. The results are explained on the basis of a steric effect on interaction. NCL Communication No. 4430.     

Suitability of ion pump for evacuation of a closed He cycled Mössbauer cryostat

For Mössbauer studies at very low temperatures, the target holder kept at 11°K with the help of a closed He cycle Mössbauer shroud, has to be insulated by evacuating the outside enclosure surrounding the shroud. The target is kept in thermal contact with the cryostat cold finger through He gas at atmospheric pressure. This provides a vibrationless thermal contact between the two. The evacuation of the outside chamber has to be vibration free which can be accomplished by means of a suitable ion pump which is totally vibration free. However, use of Vac-ion pump here could not be made successful because the pump did not work at all after little pumping. To find out the cause of pump's failure, RGA was employed which showed the presence of He gas in the outside chamber at the time of purging of He gas in the internal chamber. The pump, however, worked efficiently again when the dry N₂ gas purged in place of Helium. This points out that totally vibration free Vac-ion pumps cannot be used for evacuation of such cryostats. Here, diffusion pump was used subsequantly taking extra precautions to minimise the vibrations.     

Decay of126m Sb and the energy levels of126Te

The decay characteristics of 19 min^126m Sb have been studied using Ge(Li) and scintillation spectrometers. The sources of^126m Sb were obtained by the (n, p) reaction on enriched¹²⁶Te. The gamma rays of energies 414.4±0.3, 666.7±0.5 and 696.1±0.5 keV were found decaying with a half-life of 19 min. The study of beta spectra employing an anthracene crystal yielded two beta groups with end-point energies of 1.9±0.15 and 2.5±0.15 MeV. The results of singles and coincidence measurements have been incorporated into a decay scheme with excited states of¹²⁶Te at 666.7, 1,362.8 and 1,777.2 keV.     

Studies in fluorinated 1,3-diketones and related compounds Part X. Synthesis of some new polyfluorinated 1,3-diketones,their copper 1,3-diketonates and spectral studies

The reaction of tetrafluoro-1,2-diiodobenzene with tellurium yields an oil which, on treatment with bromine yields perfluorotelluranthrene- 9,9,10,10-tetrabromide. The latter is reduced by sodium sulfide to perfluorotelluranthrene. The crystal structure of perfluorotelluranthrene is reported.     

On some nonself mappings

Let X be a Banach space, let K be a non–empty closed subset of X and let T : K → X be a non–self mapping. The main result of this paper is that if T satisfies the contractive–type condition (1.1) below and maps ?K (?K the boundary of K) into K then T has a unique fixed point in K.     

The decay of Ho and Ho

The disintegration characteristics of ^164mHo and ^164gHo have been studied using a high-resolution Ge(Li) spectrometer. Radioactive samples of ^164mHo and ^164gHo were obtained through the (n, 2n) reaction on spectroscopically pure holmium oxide with 14 MeV neutrons. The isomeric cross-section ratio for the yields of the ground and metastable states has been estimated to be 1.0±0.25. Gamma rays of 37.7 and 56.1 keV energy have been assigned to the decay of ^164mHo and 73.4 and 91.5 keV γ-rays are attributed to the decay of ^164gHo by electron capture and negaton emission, respectively. The branching ratio for the electron capture decay of ^164gHo to the levels in ¹⁶⁴Dy has been estimated accurately from the analysis of X-ray intensities. The results have been incorporated into a decay scheme.