John J. Lavigne

Tailoring Microporosity in Covalent Organic Frameworks

The microporosity of covalent organic frameworks (COFs) is tailored using a facile synthetic approach that introduces alkyl functionalities into the pore and generates networks with pore diameters between 1-2 nm. The added substituents significantly alter the host-guest properties of the resulting materials.

Teaching Old Indicators New Tricks: A Colorimetric Chemosensing Ensemble for Tartrate/Malate in Beverages

The competition between tartrate and a common indicator (1) for a synthetic host (2) has been used to quantitate tartrate in beverages derived from grapes. The approach demonstrates a general method for the development of colorimetric assays in highly competitive media.

Aufspüren eines Paradigmenwechsels auf dem Gebiet der molekularen Erkennung: von den selektiven Rezeptoren zu den differenziellen Rezeptoren

Die molekulare Erkennung hat sich von einer Wissenschaft zum Verstandnis und zur Nachahmung der Funktionsweise biologischer Systeme hin zu einem weit vielfaltigeren Forschungsgebiet entwickelt. Naturlich wird weiterhin viel daran gearbeitet, die „Tricks der Natur“ im Hinblick auf intramolekulare Wechselwirkungen zu durchschauen, aber auch die Aussicht auf neue Technologien, die die molekulare Erkennung durch Design eroffnet, erregt zunehmend grose Aufmerksamkeit. Die Anwendungen reichen von Methoden des Molekulnachweises bis hin zur Informationsspeicherung, sogar funktionsfahige molekulare Maschinen werden konzipiert. Im vorliegenden Aufsatz werden sowohl einige historische Meilensteine auf dem Gebiet der molekularen Erkennung, die die Grundlagen der intermolekularen Wechselwirkung erlautern, beschrieben als auch neuere Anwendungen in der molekularen Sensorik detaillierter dargestellt. Zielgerichtetes Design kann dazu genutzt werden, Rezeptoren zu entwickeln, die ein groses Mas an Vorhersagbarkeit und Selektivitat aufweisen, wozu viele bekannte Mechanismen zur Signalubertragung zur Verfugung stehen. Dies ist der erste Schwerpunkt, der diskutiert wird. Des Weiteren wird das Prinzip des differenziellen und generalisierten Nachweises vorgestellt, bei dem man Sensoren nutzt, die nicht notwendigerweise dem Schlussel-Schoss-Prinzip gehorchen. Dieses Konzept ist vom Geruchs- und Geschmackssinn der Saugetiere, auf den wir kurz eingehen werden, inspiriert. Bei diesem Konzept wird notwendigerweise die kombinatorische Synthese eingesetzt, ein Forschungsgebiet, das wahrend der vergangenen Jahre ein stetiges Wachstum erfahren hat. Wir fassen den aktuellen Stand der Forschung zu synthetischen, kombinatorischen Sensoren und Rezeptoren zusammen und werden dann eine Richtung vorherzusagen, die das Gebiet der molekularen Erkennung in Zukunft vermutlich einschlagen wird. Dieser Aufsatz stellt keine detaillierte Analyse der einzelnen Gebiete (synthetische Rezeptoren, Sensoren, Geruchs- und Geschmackssinn, kombinatorische Rezeptoren und Sensoren) dar. Vielmehr soll hier gezeigt werden, wie sich all diese einzelnen Gebiete erganzen und zusammenwirken, um Nachweismethoden zu erschaffen. Unsere Schlussfolgerung ist, dass der spezifische Analytnachweis, differenzielle Nachweismethoden und die kombinatorische Chemie vereint werden, um Sensorarrays zu kreieren. So wird dem Gebiet der molekularen Erkennung unter Verwendung von synthetischen Systemen eine viel versprechende Zukunft eroffnet.

Peptide Borono Lectins (PBLs): A New Tool for Glycomics and Cancer Diagnostics

A growing body of evidence supports the idea that during tumorgenesis aberrant glycosylation events occur to cell surface and secreted glycoproteins as well as glycolipids, and as a result the glycans produced by cancer cells differ in both structure and level to those produced by normal cells. 2] These changes generally arise from the altered expression of glycosyl-transferases; typically leading to increased branching in core glycan structures as well as altering the terminal saccharide structures. The appearance of a variety of sialylated and fucosylated terminal glycan structures [for example, sialyl Lewis X (sLe), sialyl Lewis A (sLe), sialyl Tn (sTn), and Lewis Y (Le)] has been associated with malignancy. Whereas it is unclear whether these changes in glycan content are a cause or effect of oncogenesis, it is clear that specific cell surface glycans can contribute to the metastatic potential of particular tumor types. Regardless of their specific role in oncogenesis, the expression of these various glycan structures is dependent on both the tumor type and the stage of the disease; thus their ACHTUNGTRENNUNGappearance can be exploited for the development of novel cancer diagnostics. In fact, some tests based on aberrant glycosylation events have been developed for initial detection and for monitoring disease progression after beginning therapy. For example, an immunoassay for carcinoembryonic antigen (CEA), an aberrantly glycosylated glycoprotein, measures serum levels of CEA to monitor disease progression in colon cancer patients after surgery. Whereas these tests are of great value, they are often expensive and time consuming and cheaper more efficient analyses are needed. Boronic acids and other small molecules have shown great utility in sensing simple sugars and complex glycoproteins. It is therefore reasonable that the differential or random display of phenylboronic acid (PBA) moieties on a peptide backbone would result in a biocompatible, water soluble, cancer diagnostic (Figure 1A), overcoming the limitations of other boronic acid based sensors. Herein, we report proof of concept for: 1) the design and synthesis of a peptide borono lectin (PBL) ACHTUNGTRENNUNGlibrary; 2) that selective and cross-reactive PBLs can be identified using conventional microtiter plate screening techniques; and 3) that these compounds show utility for binding cancer related targets. A “low” diversity 12-mer PBL library was synthesized on aminomethyl PEG–PS resin (100 mm) using a biased split-and-pool combinatorial approach (Figure 1B). This resin was chosen because it is stable to acid hydrolysis, displays limited inherent fluorescence, and facilitates ligand-binding interactions comparable to that observed in solution. Standard Fmoc synthetic schemes were followed with Dde protected side chains. Ten amino acids were randomized between alanine endcaps producing a library with a general sequence of: Cbz-A-(X)10-A-resin where X is either 2,3-diaminopropanoic acid (DPR), 2,4-diaminobutanoic acid (DAB), ornithine (Orn), lysine (Lys), or alanine (Ala). The diamino acids chosen contain one, two, three, or four methylene units, respectively, spacing the side-chain amine from the peptide backbone. This “vertical” positioning alters the orientation between PBAs depending on the number of -CH2groups in the side chains whereas variation in the peptide sequence modifies the “horizontal” arrangement. Distinct positional variation was thereby generated between PBAs within a sequence, creating unique geometric constraints for binding. Introduction of PBAs was accomplished by removing the Dde protecting groups with hydrazine, coupling the side-chain amine with excess 2-formylphenylboronic acid, followed by reduction with NaBH4. This route to install the PBA benefits from intramolecular Lewis acid catalysis, provided by the boronic acid, to insure near quantitative incorporation of the desired functionality (see the Supporting Information for details). The theoretical diversity of the resulting PBL library (5) is in the order of 10 million distinct peptide sequences containing a statistical average of 4 PBA moieties per peptide. Because 1 g Figure 1. A) Schematic representation of a phenylboronic acid substituted peptide (PBL, sequence chosen at random) binding to a glycan or glycoprotein. B) Biased split-and-pool method used to generate the “low” diversity PBL library.

Neue Tricks für alte Indikatoren: ein colorimetrisches Chemosensor‐Ensemble für Tartrat/Malat in Getränken

Die Konkurrenz zwischen Tartrat und einem gangigen Indikator (1) um einen synthetischen Wirt (2) wurde genutzt, um Tartrat in Getranken aus Trauben quantitativ zu bestimmen. Der Ansatz demonstriert eine allgemeine Methode zur Entwicklung colorimetrischer Assays fur hochkompetitive Medien.

Multi-layered analyses using directed partitioning to identify and discriminate between biogenic amines.

Multiple layers of statistical analyses were used to decipher the response from a single, cross-reactive conjugated polymer (1) providing enhanced classification accuracies over traditional multivariate statistical approaches. This analysis was demonstrated by classifying a series of seven biologically relevant, nonvolatile amines (i.e. biogenic amines). If only a single layer of analysis was employed (linear discriminant analysis), 89% classification accuracy was achieved lacking any concentration information. However, using this multi-layered, group-ungroup method, the analytes were first categorized based on general class of molecule (directed partitioning), i.e. aromatic, aliphatic, polyamines, with 98% accuracy. In a second analysis layer, these sub-groups were broken down into the individual molecular components, with the aliphatic and aromatic amines classifying near 99%, while the polyamine identification accuracy approached 90%. In the third layer of analysis, the concentration of the analytes in question was determined in the biologically relevant range within approximately 10% accuracy by following trends in the principle component analysis output.

Boronic acid functionalized peptidyl synthetic lectins: combinatorial library design, peptide sequencing, and selective glycoprotein recognition

Aberrant glycosylation of cell membrane and secreted glycoproteins is a hallmark of various disease states, including cancer. The natural lectins currently used in the recognition of these glycoproteins are costly, difficult to produce, and unstable toward rigorous use. Herein we describe the design and synthesis of several boronic acid functionalized peptide-based synthetic lectin (SL) libraries, as well as the optimized methodology for obtaining peptide sequences of these SLs. SL libraries were subsequently used to identify SLs with as high as 5-fold selectivity for various glycoproteins. SLs will inevitably find a role in cancer diagnostics, given that they do not suffer from the drawbacks of natural lectins and that the combinatorial nature of these libraries allows for the identification of an SL for nearly any glycosylated biomolecule.

Self-repairing polymers: poly(dioxaborolane)s containing trigonal planar boron

The molecular weight of poly(dioxaborolane)s can be controlled during the polymerization reaction or through post-polymerization processing in such a manner that hydrolytic damage to these materials may be repaired, thereby regenerating the polymer.

Synthetic lectin arrays for the detection and discrimination of cancer associated glycans and cell lines

Aberrant glycosylation is a hallmark of various disease states, including cancer, and effective detection and discrimination between healthy and diseased cells is an important challenge for the diagnosis and treatment of many diseases. Here, we describe the use of boronic acid functionalized synthetic lectins (SLs) in an array format for the differentiation of structurally similar cancer associated glycans and cancer cell lines; discrimination is based on subtle variations in glycosylation patterns. We further demonstrate the utility of our SLs in recognizing glycoproteins with up to 50-fold selectivity, even in 95% human serum. Given their robust and selective nature, these SLs were able to effectively distinguish (a) five structurally similar glycans with 94% accuracy; (b) seven normal, cancerous and metastatic colon cancer cell lines, including three isogenic cell lines, with 92% accuracy; and (c) these same seven cell lines using a guided statistical analysis to improve our analysis to 97% accuracy. In total, these data suggest that an SL-based array will be useful for the diagnosis of cancer.

Metal triggered fluorescence sensing of citrate using a synthetic receptor

A metal containing fluorescent chemosensor was designed, synthesized, and studied for the quantification of citrate in common beverages. The sensor consists of Cu(II) bound by a 1,10-phenanthroline ligand which is attached to a bis(aminoimidazolium) receptor (5). Receptor 5 was designed such that binding of the metal creates an additional binding site for citrate. This additional binding interaction was found to increase the metal and citrate binding constants in a cooperative manner, yielding a minimum 2.0 fold increase in the citrate binding constant and a minimum 2.0 fold increase in the Cu(II) binding constant. Further, 5 was designed so that binding of Cu(II) quenches a photo-excited state of the 1,10-phenanthroline fluorophore. Thus, addition of citrate to 5–Cu(II) resulted in an increase of the fluorescence of the system. The nature of the fluorescence modulation upon citrate binding was probed using a model compound (6–Cu(II)). The data support an increase of electron density on the metal due to the donating ability of a carboxylate anion of citrate. In a sensing assay, the receptor is effective for measuring citrate concentrations in the micromolar range in highly competitive media. We believe this is the first demonstration of anion sensing in which the fluorescence emission is modulated due to a perturbation in the metal quenching effect upon analyte binding.