Objective To design and express a novel peptide based on ricin toxin antibody in E. coli, and to evaluate its biological activity. Methods Based on the crystal structure of ricin toxin A chain (RTA) and the RTA-rRNA interact in the complex model, the steric conformation of RTA was theoretical modeled and its functional domain was preliminarily determined. The humanized single-domain RTA antibody was designed rationally by computer-guidod molecular design method. Its coding sequence was ob- tained by overlapping extension PCR, and cloned into the pET-32a vector. The fusion protein was then ex-pressed in E. coli BL21 (DE3), identified by Western blot, and purified with Ni-NTA agarose. The binding and neutralizing activity of this novel peptide for riein was evaluated by competitive ELlSA assay and MTT assay. Results A recombinant human single-domain antibody expressing a polypeptide against RTA in the CDR3 loop was designed. The fusion protein was successfully expressed in E. coll. The purified protein can bind to ricin, and neutralize its activity in SP2/0 viability assay. Conclusion The success of the novel pep-tide based on riein toxin antibody provides a novel method to develop new generation of ricin antagonists.

Objective To analyze serum amyloid protein A (SAA) subtype and amino acid mutation sequence of the renal biopsy specimens from patients with renal amyloidosis secondary to ankylosing spondylitis (AS) by laser microdissection combined with mass spectometry.Methods Kidney biopsy formalin-preserved paraffin-embedded (FFPE) specimen slices were stained by Congo red,the positive areas of Congo red staining were selected by microdissection,after trypsin hydrolysis and filtration,peptide samples were subjected to liquid chromatography tandem mass spectrometry.Analysis softwares were used to evaluate the results,and the patient's amino acid sequence of SAA protein was compared to mutant amino acid sequence reported by literature or deduced from mutant SAA gene to determine whether there was a variation.Results SAA1 and SAA2 proteins with high abundance were identified by mass spectrometry,serum amyloid P and apolipoprotein E were also detected.No variation of SAA1 and SAA2 protein was detected.Conclusions The SAA1 and SAA2 proteins in AA amyloidosis secondary to ASwere identified for the first time,which enriched the pathogenesis of amyloidosis secondary to AS and provided a new method for the accurate classification of AA amyloidosis.