Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:To assay human p60/GST-procon80 heterodimers, taxolstabilized, tetra-methyl rhodamine-labeled microtubules were immobilized on coverslips by first perfusing flow cells with a mutant kinesin that binds strongly to microtubules but is unable to hydrolyze ATP (McNally and Thomas, 1998).
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