A general method for co-crystallization of concanavalin A with carbohydrates

Development of a Click-Chemistry Reagent Compatible with Mass Cytometry

The recent development of mass cytometry has allowed simultaneous detection of 40 or more unique parameters from individual single cells. While similar to flow cytometry, which is based on detection of fluorophores, one key distinguishing feature of mass cytometry is the detection of atomic masses of lanthanides by mass spectrometry in a mass cytometer. Its superior mass resolution results in lack of signal overlap, thereby allowing multiparametric detection of molecular features in each single cell greater than that of flow cytometry, which is limited to 20 parameters. Unfortunately, most detection in mass cytometry relies on lanthanide-tagged antibodies, which is ideal to detect proteins, but not other types of molecular features. To further expand the repertoire of molecular features that are detectable by mass cytometry, we developed a lanthanide-chelated, azide-containing probe that allows click-chemistry mediated labeling of target molecules. Following incorporation of the thymidine analog 5-ethynyl-2'-deoxyuridine (EdU) during DNA synthesis in S-phase of the cell cycle, we demonstrate that the probe introduced here, tagged with Terbium-159 (¹⁵⁹Tb), reacts via copper-catalyzed azide-alkyne Huisgen cycloaddition (click-chemistry) with Edu. Thus, detection of ¹⁵⁹Tb makes it possible to measure DNA synthesis in single cells using mass cytometry. The approach introduced here shows similar sensitivity (true positive rate) to other methods used to measure DNA synthesis in single cells by mass cytometry and is compatible with the parallel antibody-based detection of other parameters in single cells. Due to its universal nature, the use of click-chemistry in mass cytometry expands the types of molecular targets that can be monitored by mass cytometry.

Glycomics: revealing the dynamic ecology and evolution of sugar molecules

Sugars are the most functionally and structurally diverse molecules in the biological world. Glycan structures range from tiny single monosaccharide units to giant chains thousands of units long. Some glycans are branched, their monosaccharides linked together in many different combinations and orientations. Some exist as solitary molecules; others are conjugated to proteins and lipids and alter their collective functional properties. In addition to structural and storage roles, glycan molecules participate in and actively regulate physiological and developmental processes. Glycans also mediate cellular interactions within and between individuals. Their roles in ecology and evolution are pivotal, but not well studied because glycan biochemistry requires different methods than standard molecular biology practice. The properties of glycans are in some ways convenient, and in others challenging. Glycans vary on organismal timescales, and in direct response to physiological and ecological conditions. Their mature structures are physical records of both genetic and environmental influences during maturation. We describe the scope of natural glycan variation and discuss how studying glycans will allow researchers to further integrate the fields of ecology and evolution.

Community-based network study of protein-carbohydrate interactions in plant lectins using glycan array data

Lectins play major roles in biological processes such as immune recognition and regulation, inflammatory responses, cytokine signaling, and cell adhesion. Recently, glycan microarrays have shown to play key roles in understanding glycobiology, allowing us to study the relationship between the specificities of glycan binding proteins and their natural ligands at the omics scale. However, one of the drawbacks in utilizing glycan microarray data is the lack of systematic analysis tools to extract information. In this work, we attempt to group various lectins and their interacting carbohydrates by using community-based analysis of a lectin-carbohydrate network. The network consists of 1119 nodes and 16769 edges and we have identified 3 lectins having large degrees of connectivity playing the roles of hubs. The community based network analysis provides an easy way to obtain a general picture of the lectin-glycan interaction and many statistically significant functional groups.

Progress report on microstructured surfaces based on chemical vapor deposition

This book chapter discusses recent advances in the fabrication of microscale surface patterns using chemical vapor deposition polymerization. Reactive poly(p-xylylene) (PPX) coatings are useful for their ability to immobilize specific biomolecules, as determined by the PPX functional group. PPXs can either be modified postdeposition, or they can be patterned onto a substrate in situ. Specific methods discussed in this progress report include microcontact printing, vapor-assisted micropatterning in replica structures, projection lithography-based patterning, and selective polymer deposition.

Man alpha1-2 Man alpha-OMe-concanavalin A complex reveals a balance of forces involved in carbohydrate recognition

We have determined the crystal structure of the methyl glycoside of Man alpha1-2 Man in complex with the carbohydrate binding legume lectin concanavalin A (Con A). Man alpha1-2 Man alpha-OMe binds more tightly to concanavalin A than do its alpha1-3 and alpha1-6 linked counterparts. There has been much speculation as to why this is so, including a suggestion of the presence of multiple binding sites for the alpha1-2 linked disaccharide. Crystals of the Man alpha1-2 Man alpha-OMe-Con A complex form in the space group P2(1)2(1)2(1) with cell dimensions a = 119.7 A, b = 119.7 A, c = 68.9 A and diffract to 2. 75A. The final model has good geometry and an R factor of 19.6% (Rfree= 22.8%). One tetramer is present in the asymmetric unit. In three of the four subunits, electron density for the disaccharide is visible. In the fourth only a monosaccharide is seen. In one subunit the reducing terminal sugar is recognized by the monosaccharide site; the nonreducing terminal sugar occupies a new site and the major solution conformation of the inter-sugar glycosidic linkage conformation is adopted. In contrast, in another subunit the non reducing terminal sugar sits in the so called monosaccharide binding site; the reducing terminal sugar adopts a different conformation about its inter-sugar glycosidic linkage in order for the methyl group to access a hydrophobic pocket. In the third subunit, electron density for both binding modes is observed. We demonstrate that an extended carbohydrate binding site is capable of binding the disaccharide in two distinct ways. These results provide an insight in to the balance of forces controlling protein carbohydrate interactions.