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Biomedical subjects

M G Finn

Publications and source records attributed to M G Finn.

At least 37 records · Page 2Linked to original sources
PubMed2004

High sensitivity and analyte capture with desorption/ionization mass spectrometry on silylated porous silicon.

Silylation chemistry on porous silicon provides for ultrahigh sensitivity and analyte specificity with desorption/ionization on silicon mass spectrometry (DIOS-MS) analysis. Here, we report that the silylation of oxidized porous silicon offers a DIOS platform that is resistant to air oxidation and acid/base hydrolysis. Furthermore, surface modification with appropriate hydrophobic silanes allows analytes to absorb to the surface via hydrophobic interactions for direct analyte extraction from complex matrixes containing salts and other nonvolatile interferences present in the sample matrix. This enables rapid cleanup by simply spotting the sample onto the modified DIOS target and removing the liquid phase containing the interferences. This approach is demonstrated in the analysis of protein digests and metabolites in biofluids, as well as for the characterizing of inhibitors from their enzyme complex. An unprecedented detection limit of 480 molecules (800 ymol) for des-Arg(9)-bradykinin is reported on a pentafluorophenyl-functionalized DIOS chip.

Amino Acids↗
PubMed2004

A mass spectrometry plate reader: monitoring enzyme activity and inhibition with a Desorption/Ionization on Silicon (DIOS) platform.

A surface-based laser desorption/ionization mass spectrometry assay that makes use of Desorption/Ionization on Silicon Mass Spectrometry (DIOS-MS) has been developed to monitor enzyme activity and enzyme inhibition. DIOS-MS has been used to characterize inhibitors from a library and then to monitor their activity against selected enzyme targets, including proteases, glycotransferase, and acetylcholinesterase. An automated DIOS-MS system was also used as a high-throughput screen for the activity of novel enzymes and enzyme inhibitors. On two different commercially available instruments, a sampling rate of up to 38 inhibitors per minute was accomplished, with thousands of inhibitors being monitored. The ease of applying mass spectrometry toward developing enzyme assays and the speed of surface-based assays such as DIOS for monitoring inhibitor effectiveness and enzyme activity makes it attractive for a broad range of screening applications.

Enzyme Inhibitors↗
PubMed2004

Expanded chemistry of formamidine ureas.

[reaction: see text] Formamidine ureas display a rich manifold of reactivity. Thiols induce substitution at the carbonyl carbon to give thiolcarbamates; base-mediated alkylation and acylation occurs at the terminal urea nitrogen, and a new fragmentation/acylation pathway has been uncovered with isocyanates.

Journal Article↗
PubMed2004

Formamidine ureas as tunable electrophiles.

Formamidine urea compounds exchange imine fragments with primary nitrogen nucleophiles, allowing the preparation of a variety of derivatives from a single precursor. The reactivities of these species are governed primarily by the electron-donating power of the substituents and are tunable over a range of >10(3) in first-order rates of hydrolysis.

Journal Article↗
PubMed2004

Crosslinking of and coupling to viral capsid proteins by tyrosine oxidation.

Cowpea mosaic virus is composed of 60 identical copies of a two-subunit protein organized in pentameric assemblies around the icosahedral 5-fold symmetry axis. Treatment of the virus with the Ni(II) complex of the tripeptide GGH and a peroxide oxidant, or irradiation in the presence of Ru(bpy)(3)(2+) and persulfate generates covalent crosslinks across the pentameric subunit boundaries, effectively stitching the subunits together. Intersubunit crosslinking was found to occur exclusively at adjacent tyrosine residues (Y52-Y103), as predicted from the X-ray crystal structure of the capsid, and to be more extensive with the photochemical ruthenium system. The Ni/GGH oxidative procedure was also used to make covalent attachments to the virion by trapping with a functionalized disulfide reagent.

Capsid Proteins↗
PubMed2003

First practical synthesis of formamidine ureas and derivatives.

Isonitriles and ureas undergo a condensation reaction in the presence of acid chlorides to give formamidine ureas, for which no general synthetic routes currently exist. A mechanism is proposed in which the key intermediate is an electrophilic adduct of isonitrile and acid chloride. The process is tolerant of moderate variability in the nature of the components, and access to formamidine ureas of varying substitution patterns is further enhanced by a facile exchange reaction with amines. [reaction: see text]

Amidines↗
PubMed2003

New catalysts for the asymmetric hydrosilylation of ketones discovered by mass spectrometry screening.

A method for determining enantiomeric excess by mass spectrometry was employed to screen a family of chiral phosphite P,N-ligands for activity in the rhodium-catalyzed asymmetric hydrosilylation of ketones. The identification of an effective set of ligands was followed by preliminary studies of the reaction scope and mechanism. Asymmetric induction of 84-88% ee for larger-scale reactions was observed, which is close to the level of the best alternative catalysts previously discovered. The screening method was shown to be applicable to a variety of substrates without the need for special optimization.

Catalysis↗
PubMed2003

Bioconjugation by copper(I)-catalyzed azide-alkyne [3 + 2] cycloaddition.

The copper-catalyzed cycloaddition reaction between azides and alkynes functions efficiently in aqueous solution in the presence of a tris(triazolyl)amine ligand. The process has been employed to make rapid and reliable covalent connections to micromolar concentrations of protein decorated with either of the reactive moieties. The chelating ligand plays a crucial role in stabilizing the Cu(I) oxidation state and protecting the protein from Cu(triazole)-induced denaturation. Because the azide and alkyne groups themselves are unreactive with protein residues or other biomolecules, their ligation is of potential utility as a general bioconjugation method.

Alkynes↗
PubMed2002

Emerging methods for the rapid determination of enantiomeric excess.

Methods for enantiomeric excess determination using a variety of spectroscopic techniques are summarized. Particular attention is paid to techniques that have promise for application to problems of combinatorial catalyst discovery but have not yet been so employed.

Chemistry↗
PubMed2002

Natural supramolecular building blocks. Wild-type cowpea mosaic virus.

Cowpea mosaic virus (CPMV) can be isolated in gram quantities, possesses a structure that is known to atomic resolution, and is quite stable. It is therefore of potential use as a molecular entity in synthesis, particularly as a building block on the nanochemical scale. CPMV was found to possess a lysine residue with enhanced reactivity in each asymmetric unit, and thus 60 such lysines per virus particle. The identity of this residue was established by a combination of acylation, protein digestion, and mass spectrometry. Under forcing conditions, up to four lysine residues per asymmetric unit can be addressed. In combination with engineered cysteine reactivity described in the accompanying paper, this provides a powerful platform for the alteration of the chemical and physical properties of CPMV particles.

Avidin↗
PubMed2002

Natural supramolecular building blocks. Cysteine-added mutants of cowpea mosaic virus.

Wild-type Cowpea mosaic virus (CPMV) displays no cysteine side chains on the exterior capsid surface and is therefore relatively unreactive with thiol-selective reagents. Four CPMV mutants bearing cysteine residues in one of two exterior positions of the asymmetric unit were created. The mutants were shown to aggregate by virtue of disulfide bond formation in the absence of added reducing agent, bind to metallic gold, and undergo selective reactions at the introduced thiol residues. Controlled aggregation by virtue of biotin-avidin interactions was demonstrated, as was the independent derivatization of reactive lysine and cysteine positions. The ability to introduce such reactivity into a system that can be readily prepared and isolated in gram quantities should open new doors to applications in biochemistry, materials science, and catalysis.

Avidin↗
PubMed2001

2,6-Dichloro-9-thiabicyclo[3.3.1]nonane: a privileged, bivalent scaffold for the display of nucleophilic components.

The title compound, the condensation product of sulfur dichloride and 1,5-cyclooctadiene, is a reliable acceptor of a wide variety of heteroatom nucleophiles, sometimes in reversible fashion. Optical resolution of the core structure has been achieved and preserved in succeeding transformations. The high reactivity and reliable stereochemical control afforded by this system illustrates the power of neighboring-group participation by the sulfur center.

Alkanes↗
PubMed2001

Click Chemistry: Diverse Chemical Function from a Few Good Reactions.

Examination of nature's favorite molecules reveals a striking preference for making carbon-heteroatom bonds over carbon-carbon bonds-surely no surprise given that carbon dioxide is nature's starting material and that most reactions are performed in water. Nucleic acids, proteins, and polysaccharides are condensation polymers of small subunits stitched together by carbon-heteroatom bonds. Even the 35 or so building blocks from which these crucial molecules are made each contain, at most, six contiguous C-C bonds, except for the three aromatic amino acids. Taking our cue from nature's approach, we address here the development of a set of powerful, highly reliable, and selective reactions for the rapid synthesis of useful new compounds and combinatorial libraries through heteroatom links (C-X-C), an approach we call "click chemistry". Click chemistry is at once defined, enabled, and constrained by a handful of nearly perfect "spring-loaded" reactions. The stringent criteria for a process to earn click chemistry status are described along with examples of the molecular frameworks that are easily made using this spartan, but powerful, synthetic strategy.

Journal Article↗