Biomedical Engineering Reference
In-Depth Information
6
Application
to Protein Crystallization
Protein crystallization is a commonly used technique for protein analysis
and subsequent drug design. It predicts the three-dimensional arrangement
of the constituent amino acids, which in turn indicates the specific biological
function of a protein. As discussed in Chapter 1 (Section 1.3), protein crys-
tallization experiments are typically carried out manually in well plates in
the laboratory. As a result, these experiments are slow, expensive, and error
prone due to the need for repeated human intervention.
In this chapter, we present the design of a multiwell-plate microfluidic biochip
for protein crystallization; this biochip can transfer protein samples, prepare
candidate solutions, and carry out crystallization automatically [69]. To reduce
the manufacturing cost of such devices, we adopt the “Connect-5” algorithm
from Chapter 3 (Section 3.1) to generate a pin-assignment plan for the proposed
design. The resulting biochip enables control of a large number of on-chip elec-
trodes using only a small number of pins. Based on the pin-constrained chip
design, we present an efficient shuttle-passenger-like droplet manipulation
method to achieve high-throughput and defect-tolerant well loading. A test-
ing and diagnosis technique for locating defects is also presented. To facili-
tate the preparation of crystallizing reagent solutions required by the assay,
we also present an efficient algorithm to generate a preparation plan that
lists the types of stock solutions and the intermediate mixing steps needed
to generate target solutions with the required concentrations [70].
6.1 Chip Design and Optimization
In this section, we present a multiwell-plate design prototype for protein crys-
tallization. As discussed in Section 1.3, to “hit” on the correct parameters for
the crystallization of proteins, typically a very large number of experiments
(10
3
-10
4
) are required. To achieve high efficiency, we use a multiwell-plate
design for parallel processing, as in microbatch crystallization. The sche-
matic for the design is shown in Figure 6.1. The overall chip size is the same
as that of a standard Society for Biomolecular Screening (SBS) multiwell
plate. The chip has 96 wells, and there are electrode pathways to connect
these wells to reagent-loading and protein-loading loading ports.
Figure 6.2 shows the specific configuration of the wells. Note that, unlike
microbatch crystallization where reagents and proteins are preloaded either
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