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51.
To separate and identify the proteases, a substrate-specific, sensitive assay in sodium dodecyl sulfate (SDS)-polyacrylamide gels after two-dimensional (2-D) electrophoresis has been developed. This method allows simultaneous determination of protease cleavage specificity, molecular weight, isoelectric point, and if necessary, amino acid sequencing. After isoelectric focusing in immobilized pH gradient (IPG) strips (pH 6-11) (first dimension), trypsin was electrophoresed in 12% SDS polyacrylamide gels (second dimension) copolymerized with Boc-Gln-Ala-Arg-MCA (4-methyl-coumaryl-7-amide). The gels were washed in cold 2.5% Triton X-100 and water, and incubated in assay buffer (6.3 mM Bicine, 100 mM NaCl). Trypsin cleavage of the peptide-MCA generated fluorescent 7-amino-4-methyl-coumarin. In 1-D gels, as low as 500 pg trypsin could be detected and trypsin band volumes correlated linearly with the amounts of trypsin (R(2) = 0.999). In 2-D gels, the lowest amount of trypsin detected was 1 ng. The linear regression of spot volume and loading amount was still good (R(2) = 0.974). To optimize renaturation conditions, 5x5 min washes with 2.5% Triton X-100 and water, respectively, gave the strongest band volume. For fluorescence development, an assay buffer at pH 9 was the best; incubation at 37 degrees C for 30 min was sufficient. The method has application for identifying novel proteases as it does not rely on antibodies. 相似文献
52.
We have detected large deviations of the MJ = 0, J = 2 ← 1 Stark effect transition in the linear molecule HCN?HF from predictions of second-, and even fourth-, order perturbation theory. In order to account satisfactorily for the observed effect it has been necessary to set up and diagonalize the appropriate energy matrix. Smaller deviations in the case of MJ = 1, J = 2 ← 1 have likewise been treated. The values of the electric dipole moment for HCN?HF calculated from these transitions, which show large and small deviations from second-order theory, and from one (MJ = 3, J = 4 ← 3) which shows effectively zero deviation, are now consistent and are as follows:
μ/D | |||
2 ← 1 | 0 | 5.627 | |
1 | 5.601 | ||
4 ← 3 | 3 | 5.608 | |
Mean | 5.612 |