Sentence:  We also explored using a vector (pNIC-Bio2) appending a <WSD>decahistidine</WSD> tag because, in theory, this tag would offer higher affinity immobilization to an NTA chip in surface plasmon resonance (SPR), which could facilitate acquiring more accurate kinetic binding data for the Fabs. 
Meaning of the word marked with <WSD> tags:  A section of ten histidine amino acids added to a protein (such a section does not exist in nature)