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The gene encoding the IgG‐binding protein G from Streptococcus G148 was isolated by molecular cloning. A subclone containing a 1.5‐kb insert gave a functional product in Escherichia coli. Protein analysis of affinity‐purified polypeptides revealed two gene products, both smaller than protein G spontaneously released from streptococci, but with identical IgG‐binding properties. The complete nucleotide sequence of the insert revealed a repeated structure probably evolved through duplications of fragments of different sizes. The deduced amino acid sequence revealed an open reading frame extending throughout the insert, terminating in a TAA stop codon. Analysis of the two gene products by N‐terminal amino acid determination suggests that two different TTG codons are recognized in E. coli for initiation of translation to yield the two products. Based on these results several truncated gene constructions were expressed and analysed. The results suggest that the C‐terminal part of streptococcal protein G consists of three IgG‐binding domains followed by a region which anchors the protein to the cell surface. Structural and functional comparisons with streptococcal M protein and staphylococcal protein A have been made.

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This paper presents a lumped-mass model especially developed for valveless diffuser pumps. It is implemented using MATLAB. The model is tested for different previously reported valveless diffuser pumps and shows good agreement with the experimental results. The model predicts the flow-pressure characteristics for different excitation levels. The model makes it possible to study flows and pressures inside the pump. The simulations show that the maximum excitation level for the valveless diffuser pump is probably limited by low chamber pressure. Modified designs are tested and it is shown that a pump with two serially connected pump chambers working in anti-phase is advantageous compared with a single chamber pump for both the maximum volume flow and maximum pump pressure. The simulations also indicate that scaling down the diffuser elements from an 80 × 80 µm 2 throat cross-sectional area to a 40 × 40 µm 2 throat cross-sectional area probably increases the attainable pressure head.

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The complete sequence of the structural gene encoding the immunoglobulin G binding protein from Streptococcus G148 has been determined, as well as its 5' and 3' flanking sequences. The sequence reveals an open reading frame encoding a putative preprotein with a relative molecular mass of 63294. N-Terminal sequencing of the mature protein, spontaneously released from streptococcal cells, demonstrates that the signal peptide consists of 33 amino acids. The DNA sequence reveals extensive internal homologies similar to other cell-wall-bound receptors from gram-positive bacteria. Comparisons with a related gene previously isolated from another strain of streptococci revealed large differences in size, due to variations in the number of internal repeats. The structure of the gene suggests an evolution through multiple duplications.Several gram-positive bacteria contain cell-surface proteins, probably involved in the pathogenicity of these bacteria in animals and man [l]. The best known receptor is the protein A from Staphylococcus aureus, which has found extensive use in quantitative and qualitative immunological techniques due to its binding to the Fc fragment of immunoglobulins [2]. Other receptors include the M protein from Streptococcus pyogenes [3], which is a virulence factor enabling the streptococci to resist clearance by phagocytic cells, and the fibronectin receptor from S. aureus which binds to fibronectin [4]. In addition, a number of immunoglobulin Fc receptors with differential binding to various IgG subclasses have been isolated from Streptococcus group A, C and G [5 -81.Recently, the genes encoding staphylococcal protein A [9] and streptococcal M protein [3] were cloned and sequenced. This revealed in both cases repetitive structures, suggesting an evolution of these genes through multiple duplications of internal fragments of different sizes. Both genes encode proteins consisting of a signal peptide followed by a repetitive receptor region, a proline-rich region and a hydrophobic C-terminus. Thus, although only low homology could be detected at the deduced primary sequence level, the overall structure of both genes suggests a common mechanism by which these receptors associate to the cell surface.We have earlier reported on the cloning of the IgG receptor from Streptococcus G148, called protein G, and the characterization of the part responsible for IgG binding [lo]. Here, we describe the cloning and sequencing of its 5'-end of the protein G gene from strain G148, as well as that of the 5' and 3' flanking regions. This has enabled structural comparisons to the related protein G gene from strain GX7809 [ll], showing large differences in size and number of internal repeats, despite high sequence homology. The results suggest a model for the evolution of this cell-wall-bound repector .

The first valve-less diffuser fluid pump in silicon is presented. It consists of a planar double-chamber arrangement fabricated in a silicon wafer anodically bonded to a glass wafer. The pump uses fluid-directing diffuser - nozzle elements which have a depth of and a neck width of . The pump chamber diameter is 6 mm. Pump cavities and diffuser - nozzle elements are etched with an isotropic HNA silicon etch. Pumps with three different diffuser lengths are compared reaching a maximum pump capacity of and a maximum pump pressure of 1.7 m at a resonance frequency of 1318 Hz for methanol.