The screening and characterization of human Fab fragments is a rapidly growing application within protein biotherapeutics. Human Fab Capture Kit provides the reagents necessary to make the process more rational and cost-effective. Fabs can be captured from a range of different sample types, including:
• Crude cell lysates
• Periplasmic extracts
• Purified Fab fragments

Technical performance:
The figure below illustrates the high surface stability obtained using Human Fab Capture Kit with both kappa and lambda light chain Fab fragments, providing a high degree of reproducibility throughout even long assays with many samples.

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Fab screening
The kit enables fast selection of stable binders by off-rate ranking, in which captured Fabs are analyzed using only a single concentration of antigen and a buffer injection for blank subtraction. This provides a good estimate of actual dissociation rate constants (k_d), providing kinetic information early in the screening phase. This rapid method enables a throughput rate of:
•   384 Fab samples/24 hours using Biacore A100
•   48 Fab samples/24 hours using Biacore T100

Alternatively, throughput can be doubled if report point-based screening is used, where Fabs are ranked by binding response level rather than by off-rate (blank cycles are omitted in this method).

Kinetic characterization
To obtain high resolution kinetic data, captured Fab fragments are analyzed using antigen injections over  a series of concentrations. Most types of analytes are suitable, and the kit has been verified for proteins and peptides from M_r 10 000 and above. Moreover, any of the kinetic analysis methods available with specific Biacore systems (Multicycle, Single Cycle, or 2-over-2 Kinetics) may be used.