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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.