The specificity of commercial conjugates to human immunoglobulins: results of performance tests on monoclonal and polyclonal plasma cells and lymphocytes.

The activity and the specificity of 29 fluorochrome conjugated antisera against human immunoglobulin heavy and light chains were evaluated by performance testing with the direct technique of immunofluorescence using plasma cells and lymphocytes as biological substrates. Fifteen conjugates gave satisfactory results in the detection and classification of cytoplasmic and surface bound immunoglobulins and were therefore considered specific. Fourteen conjugates did not meet the required standards. The usefulness of the biological substrates for quality control tests is discussed.

Two peptides released in the complex formation of alpha 1-antitrypsin with beta-trypsin; evidence for two structurally identical, inhibitory sites in alpha 1-antitrypsin.

The exact mechanism of action of alpha 1-antitrypsin, the major protease inhibitor in human serum, is still unknown. Several investigators report the release of a small peptide during complex formation of alpha 1-antitrypsin with various proteases. In this study the release of two peptides each from the NH2- and the COOH-terminal regions of alpha 1-antitrypsin is demonstrated, indicating the presence of two inhibitory sites in alpha 1-antitrypsin. The amino acid sequence near the NH2-terminal inhibitory site is determined to be X-Ser-Ile-Pro-Pro- and near the COOH-terminal inhibitory site Y-Ala-Ile-Pro-Met-Ser-Ile-Pro. The combined results of the present report and several other reports indicate the presence of two structurally identical inhibitory sites in alpha 1-antitrypsin located at both terminal regions in the molecule.

Correlation between the presence of membrane-bound auxin binding and root regeneration in cultured tobacco cells.

When cell-suspension cultures and callus tissue from Nicotiana tabacum are grown on medium containing α-naphthaleneacetic acid (NAA) and kinetin, three classes of auxin-binding proteins can be detected. When the herbicide 2,4-dichlorophenoxyacetic acid is used instead of both NAA and kinetin, one of these sites, which is membranebound, disappears. After retransferring cells to medium containing NAA and kinetin, this membrane-bound site reappears after four to eight weeks. This reappearance is correlated with the ability of the cells to regenerate roots.

A soluble auxin-binding protein from cultured tobacco tissues stimulates RNA synthesis in vitro.

When the soluble auxin receptor from tobacco callus was isolated according to H. Oostrom et al. (1975, FEBS Lett. 59, 194-197; 1980, Planta 149, 44-47) a high polyphenol contamination in the receptor preparation was observed. We developed a new isolation procedure, which drastically reduced this contamination. The receptor, which was partially purified on Sephadex G-200, exhibited the same time- and temperature-dependent binding kinetics as described before (Oostrom et al. 1975, 1980). The Ka for indole-3-acetic acid (IAA) at 25°C was about 1.6·10(8) M(-1) and the number of binding sites varied from 0 to 2·10(-13) M mg(-1) protein. Addition of partially purified receptor preparations to isolated tobaccocallus nuclei resulted in an IAA-dependent stimulation of transcription, which was not observed with similar preparations that did not contain detectable amounts of specific IAA-binding sites. The average stimulation in the presence of 1 µM IAA was 42%; it was achieved by an increase in RNA-polymerase-II activity. The stimulation was not dependent upon the presence of 1 µM IAA during the isolation of the nuclei.