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Streptokinase is one of the best known thrombolytic agents with widespread clinical use. However, its use is not risk-free due to its immunogenicity, hemorrhagic complications and relatively short half-life in circulation. Specific PEGylation of cysteine residue is a useful technique for reducing most of these complications. The aim of this study was designing and producing a cysteine containing mutant of streptokinase, to be used for specific PEGylation. Glut-amic acid 263, which is a surface amino acid in the structure of streptokinase protein, was selected for replacement with cysteine amino acid by site directed mutagenesis. The Glu263 codon was changed to cysteine codon by SOEing PCR technique. Then, the intact and mutated streptokinase genes were inserted into expression vector pET-26b (+). The co-nstructs were transformed to Escherichia.coli Rosetta (DE3) strain and the proteins were expressed by IPTG induction. The proteins were confirmed by SDS-PAGE and western blot analysis, purified by Ni-NTA agarose affinity chroma-tography under denaturing condition with urea and Sephadex G-25 column was applied to remove urea to refold the pr-oteins. This study indicated that by using aforesaid vector and host, cysteine containing mutant gene is expressed well and it will be appropriate for specific PEGylation.

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In this study, the effects of seaweed extract (Ascophyllum nodosum) on seed germination stimulation and growth indices in chickpea were studied. A factorial experiment was performed on the basis of a completely randomized design with 3 replications. Treatments consisted of seaweed extract at four levels (0, 1.5, 2.5 and 3.5%) and drought stress at four levels (0, -0.3, -0.6 and -0.9 MP). Drought stress was induced by PEG 6000. Results showed that drought stress at -0.6 and -0.9 MP reduced the germination traits significantly compared with the controls. Seaweed extract at 2.5 and 3.5% resulted in a significant increase in the germination percentage (+18%, +24%), germination rate (+15%, +20%), seedling length (+13.3%, +15.7%), radicle area (+10.4%, +12.8%), radicle diameter (+14.2%, +25%), plumule length (+14%, +16.6%) and plumule dry weight (+10.3%, +12.6%). Under non-stress and -0.3 MP, seaweed extract levels at 2.5 and 3.5% could significantly increase the germination vigor, seed vigor index, consumed endosperm, radicle length and radicle dry weight. The application of seaweed extract at 3.5% improved the germination vigor, seed vigor index and radicle dry weight under -0.6 MP conditions. It also improved the consumed endosperm, length and radicle dry weight in samples affected by -0.9 MP conditions. According to the results, the use of seaweed extract (Ascophyllum nodosum) in the seed germination of beans is recommended for the reduction of the negative effects of drought stress.