Structural features of a polypeptide carrier promoting secretion of a β-lactamase fusion protein in yeast

Escherichia coli β-lactamase was secreted into the culture medium of Saccharomyces cerevisiae in biologically active form, when fused to the C-terminus of the hsp150δ-carrier. The hsp150δ-carrier is an N-terminal fragment of the yeast hsp150 protein, having a signal peptide and consisting mostly of a 19 amino acid peptide repeated 11 times in tandem. Here we expressed the hsp150δ-carrier fragment alone in S. cerevisiae. Apparently due to a positional effect of the gene insertion, large amounts of the hsp150δ-carrier were synthesized. About half of the de novo synthesized carrier molecules were secreted into the culture medium, the rest remaining mostly in the pre-Golgi compartment. The extensively O-glycosylated carrier fragment was purified from the culture medium under non-denaturing conditions. Circular dichroism spectroscopy showed that it had no regular secondary structure. Nuclear magnetic resonance spectroscopy showed that a non-glycosylated synthetic peptide, the consensus sequence of the repetitive 19 amino acid peptide, also lacked secondary structure. The unstructured carrier polypeptide may facilitate proper folding and secretion of heterologous proteins attached to it.     

On the ferrite-austenite equilibrium in the Fe-Cu system

The thermodynamics of ferrite containing dissolved copper is analyzed theoretically, taking into account the effect of copper on the Curie temperature. By combination with experimental information on the solubility of copper in austenite, this model is used to predict the solubility of copper in ferrite. The result shows good agreement with experimental data but indicates that the data should be extrapolated in a manner different from that which has been previously suggested. The effects of copper and cobalt on the relative stability of the α and γ phases in iron-rich alloys are compared. It is concluded that their difference is mainly caused by the difference in their effects on the Curie temperature of α-iron.     

Measurement and calculation of the phase diagram of the NaClCaCl2SrCl2 system

In this paper the system NaClCaCl₂SrCl₂ and its binary systems were studied. Using a previously calculated phase diagram of the NaClCaCl₂SrCl₂ system as a basis, accurate measurements were carried out by MDTA with high sensitivity. It is a simple eutectic system with a eutectic point at 41.9 mol % NaCl, 40.C mol % CaCl₂, 18.1 mol % SrCl₂, 744 K. In the liquidus surface for saturation with the CaCl₂SrCl₂ solid solution a univariant line starts from a point 24.8 mol % NaCl, 50.1 % CaCl₂, 25.1 mol % SrCl₂ at 823 K. The uncertainty in the liquidus temperatures is estimates to be less than ±5K, for the reason that the errors due to Supercooling and change of sample compositions were reduced by our experimental method.A new calculation of the phase diagram of the NaClCaCl₂SrCl₂ system has been performed with a new asymmetric method. It is based upon a critical assessment of the thermodynamic properties and phase diagrams of the binary systems.The agreement between our present measured and calculated phase diagrams is within ±2.5 mol %. Their good agreement indicates that the phase diagram calculated from the binary data is relatively sensitive to the se1f-consistency between thermodynamic properties and phase diagrams of binary systems.     

Predictions of the slopes of phase boundaries

Two general equations for the slopes of phase boundaries are given for the purpose of promoting numerical calculations of phase diagrams. The entropy enters into the basic equation and it is shown when it can be substituted by the corresponding enthalpy. The equations are used to demonstrate some features of phase diagrams, which are generalizations of features discussed in a recent paper by D. Goodman, J.W. Cahn, and L. Bennett.     

The effect of false ceiling on the cooling capacity of passive chilled beams

Passive chilled beams are often used to provide cooling or additional cooling when the ventilation system cannot cope with the whole cooling load. The advantage of passive cooling is that it is a silent cooling. Often the chilled beams are installed above a false ceiling and thereby the room is subdivided into two compartments. From the chilled beam a plume is generated. Make-up air (return air) needs to flow into the upper compartment to substitute the airflow generated by the chilled beam. Therefore openings for this purpose are installed in the false ceiling. Small openings constitute a resistance to the flow and the locations of the openings affect the flow pattern. The overall performance was studied in a mock-up of a real office by changing both the size and position of the openings for the make-up air. A uniform heating source was arranged by covering the floor with a heating foil. The best location and size of the openings were explored by both recording the heat absorbed by the beam and the temperature in the room. Minimum temperature attained in the room is the signature of the most efficient cooling. To achieve efficient cooling with a uniform floor-based heating source, two conditions must be fulfilled: a) the return opening area must be at least equal to the horizontal area of the chilled beam; b) the return air openings must be located at the perimeter of the room.