Identification of temperature-sensitive mutants of the human immunodeficiency virus type 1 protease through saturation mutagenesis. Amino acid side chain requirements for temperature sensitivity

Human immunodeficiency virus type 1 encodes a protease whose activity is required for the production of infectious virus. An Escherichia coli expression and processing assay system was used to screen 285 protease mutants for temperature-sensitive activity. Fourteen protease mutants had a temperature-sensitive phenotype, and approximately half resulted from conservative amino acid substitutions. Of the 14 substitutions that conferred a temperature-sensitive phenotype, 11 substitutions occurred at 6 positions that represent 3 pairs of residues in the protease that contact each other in the three-dimensional structure. These mutants assist in pinpointing regions of the protease that are important for enzyme activity and stability

Thermal conductivity of zirconia coatings with zig-zag pore microstructures

Highly porous zirconia based thermal barrier coatings have recently been synthesised with zig-zag morphology pores which appear to impede heat flow through the thickness of the coating. A combined analytical/numerical study of heat conduction across these microstructures is presented and compared with thermal conductivity measurements. The effects of pore volume fraction, pore type, pore orientation and pore spacing, together with the wave length and the amplitude of zig-zag pore microstructures on overall thermal performance are quantified. The results indicate that even a few volume percent of zig-zag inter-column pores oriented normal to the substrate surface reduce the overall thermal conductivity of the coatings by more than 50%. <br/