in ac research
In AC Research contains brief introductions to the research articles appearing in the December 1 issue plus a partial listing of articles tentatively scheduled for December 15. A free updated table of contents is available on the Web (http://pubs.acs.org/ac).
Reducing signal suppression effects. Paul Vouros and colleagues at Northeastern University and GlaxoSmithKline Pharmaceuticals construct a postcolumn concentric flow-splitting device to measure analyte signal and ionization suppression across a range of flow rates in flow-injection analysis MS, postcolumn addition LC/MS, and on-line LC/MS. Significant improvements in concentration and mass sensitivity, as well as reduced signal suppression, are obtained. (“Reduction of Signal Suppression Effects in ESI-MS Using a Nanosplitting Device”; 10.1021/ac010501i; p 5635)
A better MudPIT for shotgun proteomics. John Yates and colleagues at the Scripps Research Institute and the Torrey Mesa Research Institute describe an optimized version of their multidimensional protein identification technology (MudPIT) for shotgun proteomics. The LC/LC separation step is improved, and the low flow rate separation is interfaced directly to an electrospray ionization mass spectrometer. The enhanced MudPIT approach is reproducible within 0.5% between two analyses and is capable of a dynamic range of 10,000:1 between the most and least abundant peptides. (“An Automated Multidimensional Protein Identification Technology for Shotgun Proteomics”; 10.1021/ac010617e; p 5683) Improved parallel LC/MS. Polyacrylamide gel electrophoresis, protein assay, MALDI, and spectroscopy are time-consuming techniques that often lack the resolution to distinguish desirable proteins from impurities. Parallel highthroughput LC/MS systems can screen small molecules in biological matrixes, but little progress has been made with characterizing larger recombinant proteins, which are often specific drug targets. Bingbing Feng and colleagues at Glaxo-
SmithKline create a system with improved software that overcomes flow-split instability, irreproducibility, and labor-intensive data processing. As an example, the researchers optimize the production and purification of an acylated protein substrate. (“An Integrated Ten-Pump, Eight-Channel Parallel LC/MS System for Automated High-Throughput Analysis of Proteins”; 10.1021/ac0106187; p 5691)
Tandem MS to characterize spore biomarkers. Plamen A. Demirev and colleagues at the University of Maryland use high-resolution tandem MS FT-ion cyclotron resonance MS to analyze intact protein biomarkers from Bacillus cereus T spores. They believe that this approach combined with bioinformatics can drastically improve the specificity of individual microorganism identification, particularly in complex environments. (“Tandem Mass Spectrometry of Intact Proteins for Characterization of Biomarkers from Bacillus cereus T Spores”; 10.1021/ac010672n; p 5725)
Monitoring PDGF. Weihong Tan and colleagues at the University of Florida and TriLink BioTechnologies use a fluorophore-labeled molecular probe based on a high-affinity plateletderived growth factor (PDGF) aptamer for ultrasensitive detection of PDGF in homogenous solutions. Fluorescence anisotropy is used for the real-time monitoring of the binding between the aptamer and the protein. (“Molecular Aptamer for Real-Time Oncoprotein Platelet-Derived Growth Factor Monitoring by Fluorescence Anisotropy”; 10.1021/ac010703e; p 5752) CE for gene expression in single cells. Sheri Lillard and Jennifer Zabzdyr of the University of California–Riverside monitor gene expression in single cells using CE with laser-induced fluorescence detection. The -actin messenger RNA is amplified using the reverse-transcriptase polymerase chain reaction, and a detection limit corresponding to ~133 RNA molecules/nL before amplification is calculated. (“Measurement of Single-Cell Gene Expression Using Capillary Electrophoresis”; 10.1021/ac0155714; p 5771) Exo- and endocytosis studies using QCM dissipation. To monitor exo- and endocytosis in uniform populations of cells, Owe Orwar and colleagues at Chalmers University of Technology, Göteborg University, Karolinska Institute
Denotes articles tentatively scheduled for the December 15 issue D E C E M B E R 1 , 2 0 0 1 / A N A LY T I C A L C H E M I S T R Y
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in ac research
Stockholm (all in Sweden), and Pennsylvania State University use quartz crystal microbalance dissipation. This approach allows comparisons among various cell types without the variations that can complicate the interpretations of single-cell studies. (“Measurement of the Dynamics of Exocytosis and Vesicle Retrieval at Cell Populations Using a Quartz Crystal Microbalance”; 10.1021/ac010777q)
Trienzyme sensor. Fumio Mizutani and co-workers at the National Institute of Advanced Industrial Science and Technology (Japan) present a trienzyme sensor for the amperometric determination of acetic acid. They prepare the biosensor by immobilizing acetate kinase, pyruvate kinase, and pyruvate oxidase on a poly(dimethylsiloxane)-coated electrode. The researchers use the biosensor, which can last for more than a month, to determine acetic acid in ethanol-containing foods. (“Amperometric Determination of Acetic Acid with a Trienzyme/Poly(dimethylsiloxane)-Bilayer-Based Sensor”; 10.1021/ac010622i; p 5738)
Quantifying the stench. Even a hint of hydrogen sulfide is hard to miss, but it can be extremely detrimental to the olfactory system, cauterize nerve endings, and actually deaden the sense of smell. Because hydrogen sulfide can be deadly, efficient detection is important for areas where the large-scale processing of sulfur-containing organic materials occurs. Purnendu Dasgupta and colleagues at Texas Tech University and the Agency for Toxic Substances and Disease Registry have developed a fully automated, portable, continuous fluorescence detection instrument with sensitivity to 5. (“Modeling of the Separation of the Enantiomers of 1-Phenyl-1-propanol on Cellulose Tribenzoate”; 10.1021/ac010751z; p 5704)
Poly(Amidoamine) Dendrimers”; 10.1021/ac0155355; p 5743)
Purifying molecularly bridged metal nanoparticle arrays. Stefan Franzen, Daniel L. Feldheim, and colleagues at North Carolina State University develop size exclusion chromatography and centrifugation protocols for isolating enriched fractions of phenylethynyl-bridged metal nanoparticle dimers and trimers from monomeric particle starting material. Neither method causes significant sample aggregation or bridge replacement. Both methods yield solutions containing 70% bridged gold dimers. (“Purification of Molecularly Bridged Metal Nanoparticle Arrays by Centrifugation and Size Exclusion Chromatography”; 10.1021/ac010812t; p 5758)
Clarity in the cold. Reducing sample temperatures almost always improves the vibronic resolution of fluorescence and excitation spectra. Andres Campiglia and colleagues at North Dakota State University and Dakota Technologies capitalize on these effects by developing a fiber-optic probe to freeze samples at 4.2 K in seconds. They demonstrate sample-to-sample reproducibility and the ability to collect accurate spectra for both single-site and multisite polyaromatic hydrocarbon and n-alkane systems. (“Laser-Induced Multidimensional Fluorescence Spectroscopy in
SPR for low molecular weight analytes. Surface plasmon resonance (SPR) cannot study small molecules that don’t have enough mass to measurably change the refractive index. However, the refractive index also can be affected by changes in receptor conformation. J. Bruce Pitner and colleagues at BD Technologies use ligand-induced conformational changes to monitor the binding of molecules as small as 40 Da. (“Using Receptor Conformational Change To Detect Low Molecular Weight Analytes by Surface Plasmon Resonance”; 10.1021/ac0105888; p 5732) The properties of PPI dendrimers. Sheryl A. Tucker and colleagues at the University of Missouri–Columbia use the solvatochromic probe phenol blue to investigate the interior of poly(propyleneimine) (PPI) dendrimers. Two discrete dye populations are observed under each generation. The PPI dendrimers form tight, nonpolar associations with most available dyes within the dendrimer interior near the core. (“Spectroscopic Investigations of Poly(Propyleneimine) Dendrimers Using the Solvatochromic Probe Phenol Blue and Comparisons to D E C E M B E R 1 , 2 0 0 1 / A N A LY T I C A L C H E M I S T R Y
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