Structure-based histidine substitution for optimizing pH-sensitive Staphylococcus protein A.

Optimizing antibody purification is crucial to overcoming a bottleneck in the costly manufacturing process for antibody therapy. To address this issue, we designed a pH-sensitive Staphylococcus aureus protein A variant that retained its innate stability and affinity toward antibody. On the basis of structural information and mutation analysis data, we identified candidate positions for accumulative histidine substitutions to cause electrostatic repulsion under acidic conditions.

Optimizing pH response of affinity between protein G and IgG Fc: how electrostatic modulations affect protein-protein interactions.

Protein-protein interaction in response to environmental conditions enables sophisticated biological and biotechnological processes. Aiming toward the rational design of a pH-sensitive protein-protein interaction, we engineered pH-sensitive mutants of streptococcal protein G B1, a binder to the IgG constant region. We systematically introduced histidine residues into the binding interface to cause electrostatic repulsion on the basis of a rigid body model.

Quantitative determination of urinary 8-hydroxy-2'-deoxyguanosine level in healthy Japanese volunteers.

8-hydroxy-2'-deoxyguanosine (8-OHdG), as a measure of oxidative stress, was measured in healthy Japanese volunteers using an ELISA (New 8-OHdG Check, JICA). Analysis of daytime spot urine of 83 healthy male subjects and smoking habit, exercise and age revealed significant correlation only between the urinary level of 8-OHdG and age. As the inter-individual variation of 8-OHdG of the daytime spot urine was relatively high, we next determined inter-and intra-individual variation of 5 healthy volunteers.