No abstract

The lectin concanavalin A (Con A) binds methyl a-D-mannopyranoside (MeaMan) as well as a-Dmannosyl groups at the nonreducing terminus of oligosaccharides. Ligand peptides that mimic the binding of MeaMan to Con A were identified from screening an epitope library composed of rilamentous phage displaying random hexapeptides. A consensus sequence was identified among affinitypurified phage; Con A binds phage bearing this sequence and is inhibited from doing so by MeaMan. When tested for binding against a panel of lectins, phage bearing this sequence bind only weakly to a closely related D-mannose-binding lectin, indicating that binding to Con A is highly selective. A synthetic peptide bearing the consensus sequence blocks the precipitation of Con A by dextran with an inhibition strength equivalent to that of methyl a-D-glucopyranoside. These results demonstrate that the specificity of Con A is not limited to carbohydrates and that highly selective sugar-mimics for lectins of plant, animal, or bacterial origin may be identified from epitope libraries.The lectin Con A comprises a significant fraction of the protein in the jack bean (Canavalia ensiformis). It is a tetramer, consisting of four identical subunits that bind with moderate affinity M) to the a anomers of D-mannose and D-glucose (1). When oligosaccharides containing these sugars are displayed on a cell surface, Con A binds with high avidity as a result of multivalent interactions. Because of this high avidity and its specificity for particular sugars, the function of Con A is presumed to involve binding to D-mannosyl-containing oligosaccharides as part of a specific cell recognition process. In an effort toward developing specific target-ligands for lectins, we have discovered a set of related peptides that bind at or near the sugar-binding site of Con A with affinity equivalent to that of methyl a-Dglucopyranoside (MeaGlc). These peptides were obtained from screening a hexapeptide epitope library with Con A.The epitope library consists of 200 million filamentous phage clones that display about 70o of all possible hexapeptides (2). The use of epitope libraries in identifying ligand peptides has been demonstrated for protein-binding antibodies (2-4), as well as for the biotin-binding site of streptavidin (5). The latter result was the first demonstration that epitope libraries can be used to discover peptides that mimic the binding of nonpeptide ligands.Phage bearing Con A-binding sequences were affinityenriched from the library and identified by (i) exhibiting a consensus sequence that is shared among randomly chosen phage and by their ability (ii) to selectively bind to Con A in ELISA, (iii) to be significantly retained by immobilized Con A, and (iv) to be specifically inhibited from binding and enrichment on Con A by methyl a-D-mannopyranoside (Mea Man).Furthermore, hexapeptide bearing the consensus sequence was shown to bind directly to Con A and to inhibit the precipitation of Con A by dextran with a strength equivalent to that of MeaGlc, where...

Microfluidics has been the key component for many applications, including biomedical devices, chemical processors, microactuators, and even wearable devices. This technology relies on soft lithography fabrication which requires cleanroom facilities. Although popular, this method is expensive and labor-intensive. Furthermore, current conventional microfluidic chips precludes reconfiguration, making reiterations in design very time-consuming and costly. To address these intrinsic drawbacks of microfabrication, we present an alternative solution for the rapid prototyping of microfluidic elements such as microtubes, valves, and pumps. In addition, we demonstrate how microtubes with channels of various lengths and cross-sections can be attached modularly into 2D and 3D microfluidic systems for functional applications. We introduce a facile method of fabricating elastomeric microtubes as the basic building blocks for microfluidic devices. These microtubes are transparent, biocompatible, highly deformable, and customizable to various sizes and cross-sectional geometries. By configuring the microtubes into deterministic geometry, we enable rapid, low-cost formation of microfluidic assemblies without compromising their precision and functionality. We demonstrate configurable 2D and 3D microfluidic systems for applications in different domains. These include microparticle sorting, microdroplet generation, biocatalytic micromotor, triboelectric sensor, and even wearable sensing. Our approach, termed soft tubular microfluidics, provides a simple, cheaper, and faster solution for users lacking proficiency and access to cleanroom facilities to design and rapidly construct microfluidic devices for their various applications and needs.