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–363. [9] L.C.M. Ngoka, M.L. Gross and P.L. Toogood: “Sodium-directed selective cleavage of lactones: a method for structure determination of cyclodepsipeptides”, Int. J. Mass Spectrom., Vol. 182/183, (1999), pp. 289–298. [10] L.C.M. Ngoka and M.L. Gross: “Multistep collisionally activated decomposition in an ion trap for the determination of the amino-acid sequence and gas-phase ion chemistry of lithium-coordinated valinomycin”, Int. J. Mass Spectrom., Vol. 194, (2000), pp. 247

Notiz 245 Mechanism of Energy Transfer in Collisional Activation of Kiloelectron-Volt Macromolecular Ions Einar Uggerud Department of Chemistry, University of Oslo, Norway* Peter J. Derrick Department of Chemistry, University of Warwick, Coventry, England Z. Naturforsch. 44a, 245-246 (1989); received December 9, 1988 An impulsive collision theory explains why helium is an effective target gas for collisionally activated decomposition of large biological ions. Knowledge of mechanisms of collisional energy transfer is fundamental to many areas of chemistry

a SEC fraction can be identified by this tec&ique (SEC-MS-MS). Daughter ions ob- tained by collision activated decomposition (CAD) in the second MS step of protonated and deprotonated parent ion, (M, + I)+ or (M, - 1)+ will normally not interfere with other (M2+ I)+ or (M2 - I)+ ions of lower molecular mass fractions, since a size excluded fraction from the chromatographic step generally contains components of comparable molecular size even if the molecular size is not always equivalent to the molecular mass. This paper presents an example of how to

. Naturforsch. 55c, 146-152. Mohn G., Taraz K. and Budzikiewicz H. (1990), New pyoverdin-type siderophores from Pseudomonas fluo­ rescens. Z. Naturforsch. 45b, 1437-1450. Poppe K., Taraz K. and Budzikiewicz H. (1987), Pyover­ dine type siderophores from Pseudomonas fluo­ rescens. Tetrahedron 43, 2261-2272. Roboz J., Nieves E., Holland J. F., McCamish M. and Smith S. (1988), Collisional activation decomposition of actinomycins using tandem mass spectrometry. Bio- med. Environ. Mass Spectrom. 16, 67-70 . 164 W. Voßen et al. ■ Pyoverdin from Pseudomonas fluorescens PI 9

Pyoverdines from Two Pseudomonas Species m/z 886 * m/z 827-18 * f = H N . J m/z 799-18 **T O i HO-CH m/z 462 m/z 445 * m/z 417 c i CHr NHV m/z 131 m/z 218 0ii „ r .CHo NH CH2 2COOH Fig. 2. Characteristic ions in the ESI mass spectrum of la (mass numbers without marks: sequence ions observed only by skimmer collision activated decomposition (skimmer CA); with *: observed by skimmer CA and in the ior trap; with **: observed only in the ion trap). tion as shown by NM R and chemical degradation including the determ ination of the d - and L-config- urations. ESI

phenylalanine ion. For all the mass spectrometry (MS) and MSMS experi- ments, mass calibration and resolution adjustments (0.7 amu width at half peak-height) on both the resolving quadrupoles were automatically optimized using a polypropyleneglycol (PPG) 1x10–4 mol/l solution introduced via the system’s built-in infusion pump. Collisionally activated decomposition (CAD) MSMS was performed through the closed-design Q2 collision cell incor- porating the linear ion acceleration (LINAC) feature, operating with 8 mTorr pressure of nitrogen as the collision gas. Data were acquired

energy, using xenon as a bombarding gas (1 • 10~5 mbar). m-Nitrobenzyl alcohol (Aldrich Chemie, Steinheim, Germany) was used as a matrix. The products of collisionally activated decompositions in the first field- free region of the instrument were analyzed by daughter ion linked scan (B/E constant) using the manufacturer's software. Helium was used as a collision gas, applied amount of He attenuated the primary ion beam by 50% (collision cell floated at the ground potential). NMR spec- tra were measured on a Varian VXR-400 MHz instrument in CDC13 at 298 K (observing

activated decompositions, CAD). Analyser conditions can be chosen to scan the daughter ions of a chosen parent, the parents of a chosen daughter or the parent ions giving rise to the same neutral loss (constant neutral loss). With modern instrument control by data system, these experiments can be carried out with ease and flexibility. Such experiments are of great utility in delineating fragmentation routes and mechanisms, information that is often not obvious in standard spectra. The use of isotope data in interpreting CAD spectra has been discussed (ref. 58). In

). Mass Spectrometric Data Acquisition The solution of an analytical problem may require a) full mass spectra (for library search, structure information), b) raw data of a small mass range (e.g. for the determination of isotope patterns or just molecular weights) c) mass chromatograms of selected ions (for the quantitation of target compounds with lowest detection limits) MS/MS experiments with collisionally activated decompositions (CAD), 1916 COMMISSION ON MICROCHEMICAL TECHNIQUES AND TRACE ANALYSIS The principle of the technique is shown in Fig. 1: The

CY, Gaskell SJ. Influence of cysteine to cysteic acid oxidation on the collision-activated decomposition of protonated peptides: evidence of intraionic interactions. J Am Soc Mass Spectrom. 1992;3:337–344. [399] Cox KA, Gaskell SJ, Morris M, Whiting A. Role of the site protonation in the low-energy decomposition of gas-phase peptide ions. J Am Soc Mass Spectrom. 1996;7:522–531. [400] Dongré AR, Jones J, Somogyi A, Wysocki VH. Influence of Peptide Composition, Gas-Phase Basicity, and Chemical Modification on Fragmentation Efficiency: Evidence for the Mobile Proton