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Characterization of polystyrene-binding peptides (PS-tags) for site-specific immobilization of proteins

In this study, we characterized polystyrene-binding peptides (PS-tags) that possess a specific binding affinity for hydrophilic polystyrene (phi-PS) plates. Both the FITC-labeled PS19-1 (RAFIASRRIKRP) and PS19-6 (RIIIRRIRR) peptides showed strong binding affinity for commercially available hydrophilic, but not hydrophobic, PS plates in the presence of the non-ionic surfactant Tween 20. The dissociation constants (K_d) of the PS19-1 and PS19-6 peptides for the hydrophilic PS-A plate were 169 and 86 nM, respectively, and the K_d of both peptides increased with the concentration of NaCl or urea. Based on adsorption yield and residual activity of glutathione S-transferase (GST) after fusion with the PS19-6 peptide or its variants, it was found that the basic amino acid in the PS-tags, i.e., Arg was essential for the strong binding affinity of PS-tags in both the peptide and peptide-fused protein forms The aliphatic amino acids in PS19-6 and PS19-6L, such as Ile or Leu, were also effective. Thus, a series of PS-tags that possess this unusual feature, especially the peptides PS19-6 (RIIIRRIRR) and PS19-6L (RLLLRRLRR), are potential candidate affinity peptide tags for site-specific immobilization of proteins onto hydrophilic PS plates, which show potential as solid supports for protein-based biochips.     

Extension of thermophysical and thermodynamic property measurements by laser pulse heating up to 10,000 K. I. Under pressure

The necessity for increased high-temperature data reliability and extension of thermophysical property measurements up to 5000 K and above are discussed. A new transient-type laser-autoclave technique (LAT) has been developed to extend density and heat capacity measurements of high-temperature multicomponent systems far beyond their melting and boiling points. Pulsed multibeam laser heating is performed in an autoclave under high inert gas pressure to eliminate evaporation. The spherical samples are positioned by containment-free acoustic levitation regardless of their conductive or magnetic properties. Temperature, spectral and total emittances are determined by a new microsecond six-wavelength pyrometer coupled to a fast digital data acquisition system. The density is determined by high resolution microfocus X-ray shadow technique. The heat capacity is obtained from the cooling rate. Further applications are a combination of the laser-autoclave with splat cooling techniques for metastable structure synthesis and amorphous metals research and an extension of the LAT for the study of critical phenomena and the measurement of critical-point temperatures.Paper presented at the First Workshop on Subsecond Thermophysics, June 20–21, 1988, Gaithersburg, Maryland, U.S.A.     

Equation of state of uranium oxide

The total and partial pressures over liquid UO₂ have been measured and calculated up to 5000K. A review of previous work is given. The equation of state of UO₂ as the main constituent of the fast breeder oxide fuel is required up to at least 5000K in order to estimate the energy release in a loss of flow (LOF) driven hypothetical core disruptive accident (HCDA) of the liquid metal fast breeder reactor (LMFBR).Two models, a macroscopic “mixture” model and a microscopic “defect” model have been developed to determine the oxygen potential of UO₂₀₀ up to 5000 K.A combination of mass spectrometric, Langmuir probe and high tension diode studies, applied for the first time to the laser vaporization process, revealed large quantities of ions emitted directly from the surface, and resolved previous discrepancies between measured and calculated vapour pressures by an enhanced rate of evaporation due to ion emission. As shown theoretically intrinsic ion emission can contribute to the net evaporation rate only if the resulting positive space charge can be neutralised. It is proposed that this can be accomplished by the presence of “hot” electrons in the plasma.The recommended equilibrium total pressure over liquid UO_2.00, valid between the melting point and 5000K, is $\text{log p (MPa) = ? 2.717 ? 20131/T + 1.925}\text{log T}$.     

Extension of vapour pressure measurements of nuclear fuels (U,Pu)O2 and UO2 to 7000 K for fast reactor safety analysis

A new high-energy laser technique, including fast temperature recording in the microsecond range, was developed for measuring the vapour pressure of fast breeder uranium-plutonium oxide fuels up to 7000 K. In the ternary system, the pressure of uranium-plutonium oxide above its melting point was determined to be $\text{log p (atm) = 7.966 ? (28137/T)}$, yielding a high-temperature heat of evaporation of $\text{ΔH}{}_{\mathrm{evap}}\text{= 128.7 kcal/mol}$. Measurement of the UO₂ partial pressure over the solid gave $\text{log p (atm) = 9.365 ? (32436/T)}$, resulting in a heat of sublimation of $\text{ΔH}{}_{\mathrm{sub}}\text{= 148.4 kcal/mol}$. The difference of these heats yields the heat of fusion $\text{ΔH}{}_{\mathrm{f}}\text{= 19.7 kcal/mol}$, which is in good agreement with the literature value of 19.4 kcal/mol. In the binary UO₂ system, the pressure above the melting point was determined to be $\text{log p (atm) = 7.7 ? (27900/T)}$,giving a heat of evaporation of $\text{ΔH}{}_{\mathrm{evap}}\text{= 127.6 kcal/mol}$. An assessment of literature data for below the melting point yielded $\text{log p (atm) = 8.846 ? (31506/T)}$, and a heat of sublimation of $\text{ΔH}{}_{\mathrm{sub}}\text{= 144.1 kcal/mol}$. The resulting heat of fusion, $\text{ΔH}{}_{\mathrm{f}}\text{= 16.5 kcal/mol}$, is only slightly below the published value of $\text{ΔH}{}_{\mathrm{f}}\text{= 17.7 kcal/mol}$.     

Darstellung von schwer entflammbaren polymeren unter verwendung von β-trichlormethyl-β-lactonen und deren derivate

By using β-trichloromethyl-β-lactones it is possible to incorporate the CCl₃-group into various classes of polymers. This can be achieved either via ringopening copolymerization or by using the adducts of these lactones with amines, alcohols or phenols in polycondensation or polyaddition reactions. Under suitable reaction conditions block- or graft-copolymers can be obtained. Finally, derivatives of β-trichloro-β-propiolactones can be used for the incorporation into polymers after or during polymerization. Polymers containing CCl₃-groups are flame resistant or selfextinguishing. Often, these effects are observed at lower chlorine contents than normally necessary with other chlorinated flame retardants.