News
Parents do some cleaning up
Parent ion scans of immonium, oxonium, and phospho group ions (all of which are in the low m/z range) can be The usefulness of parent ion scans for used to selectively identify molecules analyzing small molecules and peptides from a complex mixture. For example, has already been demonstrated. Now, Matthias Mann and Gitte Neubauer at the through a parent ion scan of the oxonium ion of HexNac (m/z 204) of a mixture of European Molecular Biology Laboratory RNAse B (a glycoprotein) and carbonic in Heidelberg, Germany, have extended anhydrase (a nonglycosylated protein), the applicability of these scans to large the RNAse B was selectively identified. molecules such as proteins and oligonucleotides. These parent ion scans allow Similarly, a parent ion scan of the phospho group (m/z 79) allowed the detection the selective detection of molecules that might otherwise be lost in chemical noise. of a phosphorylated protein (B-casein) in the presence of 3. nonphosphorylated protein (carbonic anhydrase) Mann and Neubauer also determined the applicability of parent ion scans for phospho groups in the analysis of oligonucleotides. When a parent ion scan was done with a synthetic oligonucleotide that still had contaminants from the synthesis process, the chemical noise from the salt adducts was greatly reduced and Mass spectrum of a 1:1 carbonic anhydrase and RNAse B the mass spectrum mixture with the major glycoform of RNAse B marked (A). The much simplified (/. parent ion scan of the oxonium ion of HexNac (m/z 204) Mass Spectrom 1999 selectively detects only RNAse B (B). (Adapted with 32 94-98) permission from John Wiley & Sons.)
Making DNA more like a protein
molecule that is chemically more like a peptide and that, in turn, improves the detectability of small modified oligonucleotides by MALDI by a factor of > 110 over unmodified DNA The authors also evaluated different matrices for laser desorption of the chemically modified DNA (Rapid Commun. Mass spectrom. 1997,11,43-50)
MALDI has emerged as a major technique for peptide analysis, but the same technique works poorly for studying DNA Key obstacles include the instability of DNA under the acidic conditions of sample preparation and desorption, as well as the large number of negative charges on the sugar phosphate backbone. Ivo G. Gut and colleagues at the Imperial Cancer Research Fund (United Kingdom) tackled this problem by chemically modifying DNA They introduced a new procedure that quantitatively attaches quaternary ammonium fixed charge tags to the 5' or 3' NH2 ends of DNA In addition, they used a previously reported technique to alkylate the backbone of phosphoroTwo-step modification of DNA. (Adapted with thioate DNA The result is a permission from John Wiley & Sons.) 226 A
Analytical Chemistry News & Features, April 1, 1997
Detecting tuberculosis Infection by Mycobacterium tuberculosis (MTB), the agent responsible for the respiratory disease, remains a major health care problem. Clinical tests for MTB are typically culture dependent and, because of the slow growth of the organism, time consuming. A faster, precise test would aid in patient treatment and in protection of health care workers. Joseph Wang and colleagues at New Mexico State University introduced a new sequence-specific electrochemical biosensor for short fragments of MTB DNA The sensor is a carbon-paste transducer modified with 27- and 36-mer oligonucleotide probes that hybridize to complementary strands from the MTB DNA direct repeat region. These sequences are known to be highly specific to MTB complex organisms. Chronopotentiometry, in connection with a Co(phen)|+ indicator, is used to transduce the hybridization event. Hybridization takes place in 5 to 15 min, and the MTB DNA is quantified at ng/mL levels. (Anal. Chim. Acta 1997, 337, 7,-48)
Chronopotentiograms for increasing concentrations of27-mer (top) and 36-mer (bottom) MTB DNA. (Adapted with permission from Elsevier Science.)
Novel laser sampling Laser ablation is an attractive method for generating samples for ICP techniques. Unfortunately, the method suffers from a host of problems such as preferential vaporization, laser-induced plasma shielding of the laser beam, and variations in the amount and stoichiometry of material ablated from the surface. W. T. Chan and Kenneth K K. Lam from the University of Hong Kong introduced a new approach, back-surface ablation, that circumvents some of these problems.
ICP emission intensiiy for Fe (II) for back- and front-surface ablation of a paint samplleas function of time. (Adapted with permission from the Royal Society of Chemistry..
Afilmof the sample measuring a few tens of micrometers in thickness is coated onto a transparent substrate. The laser beam is then shone through the substrate onto the sample surface. As the sample
SOCIETY
1997 EAS and Benedetti-Pichler award winners The 1997 winners of the Eastern Analytical Symposium awards are Barry Karger of Northeastern University, Paul Lauterbur of the University of Illinois at Urbana-Champaign, Tormod Naes of the Norwegian Food Research Institute, Svante Wold of the University of Umea, and Richard Zare of Stanford University. John G. Dorsey of Florida State University will receive the American Microchemical Society's Benedetti-Pichler Memorial Award. The awards will be presented at EAS '97, Nov. 16-21, in Somerset, NJ. Wold, professor of chemometrics at the University of Umea, will receive the Award for Achievements in Near-IR Spectroscopy, sponsored by Perstorp Analytical/NIR Systems. The award recognizes individuals who have made a significant contribution to the development and implementation of near-IR as a process analytical technique. ^Vold's current work focuses on multivariate modeling design and analysis; structure-proDerty and structure-activity relationshipsand multivariate dynamic modeling of chemical processes
vaporizes, the pressure builds until the sample at the laser spot vaporizes explosively. The irradiated area is completely removed, and thus preferential vaporization is minimized. The amount of sample removed is up to 100-fold greater than that removed by direct, or front-surface, ablation. However, the authors reported that sensitivity increases only threefold, probably because of poor transport efficiency of the laser-sampled material into the ICP detector. The authors applied their method to the analysis of household emulsion paints by ICP-AES, determining 10 elements at concentrations ranging from 10 to 1000 ppm. These results are compared with values determined by microwave digestion/solution nebulization combined with ICP-AES. (J. Anal, At. Spectrom. .997,12, ,712)
Karger, professor of chemistry and director of the Barnett Institute of Chemical Analysis and Materials Science at Northeastern University, will receive the Award for Achievements in Separation Science, sponsored by Waters. Karger's recent efforts have focused on the fundamental aspects of CE and its use in solving problems in the biological sciences, particularly the Human Genome Project. Naes, professor of statistics at the Norwegian Food Research Institute, will receive the Award for Achievements in Chemometrics. Naes's work focuses on the development and application of multivariate chemometric and statistical methods in food science. Lauterbur is director of the Biomedical Magnetic Resonance Laboratory and acting head of the Department of Medical Information Science at the University of Illinois at UrbanaChampaign. He will receive the Award for Achievements in Magnetic Resonance.
BUSINESS
PE acquires GenScope Perkin Elmer has acquired GenScope, a development-stage company that has worldwide exclusive rights to "AFLP" technology for selectively analyzing any portion of genetic material without prior sequence information. According to PE, AFLP generates a unique DNA fragment from each expressed gene in tissues in an amount that reflects the gene's expression level. By combining this technology with high-throughput PCR and automated fluorescence electrophoresis systems, AFLP provides quantitative analysis of all genes expressed in a tissue without prior knowledge of their existence or genetic sequence.
Lauterbur's research interests include the structure and properties of molecules, crystals, and biological systems, and medical and biological imaging. Zare, professor of chemistry at Stanford University, will receive the Award for Outstanding Achievements in the Fields of Analytical Chemistry. This award recognizes individuals who have made significant contributions to several distinctfieldsof analytical chemistry. Zare is known for his research in laser chemistry, chemical reactions at the molecular level and the use of laserinduced fluorescence for studying reaction dynamics Dorsey, professor of chemistry and chair of the chemistry department at Florida State University, is best known for his contributions to flow analysis and biological and environmental partitioning processes as well as the Foley-Dorsey equation for calculating theoretical plates. Dorsey's research interests include the areas of fundamental liquid chromatography CE analytical applications of micelles and organized media flow injection analysis and old Bordeaux wines
Analytical Chemistry News & Features, April 1, 1997 227 A
