Electrospray ionization MALDI mass Matrix-assisted laser desorption

With the identities and amounts of amino acids known, the peptide is sequenced to find out in what order the amino acids are linked together. Much peptide sequencing is now done by mass spectrometry, using either electrospray ionization (ESI) or matrix-assisted laser desorption ionization (MALDI) linked to a time-of-flight (TOF) mass analyzer, as described in Section 12.4. Also in common use is a chemical method of peptide sequencing called the Edman degradation. 

Mass spectrometry is also used for nanoparticles investigations. Two ionization techniques often used with liquid and solid biological samples include electrospray ionization (ESI) and matrix-assisted laser desorption/ioiuzation (MALDI). Inductively coupled plasma (ICP) sources are mainly used for metal analysis. In general,... 

FAB and PD have been replaced by electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI) in the analytical mass spectrometry laboratory, because both of these newer techniques have a wider mass range of analysis and have lower detection limits. ESI and MALDI have become invaluable ionization techniques for nonvolatile components. This is particularly true for a wide range of biological molecules including proteins, peptides, nucleic acids, etc. Samples can be analyzed by ESI using either direct injection or introduction through liquid chromatography. 

The use and development of high-resolving separation techniques as well as highly accurate mass spectrometers is nowadays essential to solve the proteome complexity. Currently, more than a single electrophoretic or chromatographic step is used to separate the thousands of proteins found in a biological sample. This separation step is followed by analysis of the isolated proteins (or peptides) by mass spectrometry (MS) via the so-called soft ionization techniques, such as electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) combined with the everyday more powerful mass spectrometers. Two fundamental analytical strategies can be employed the bottom-up and the top-down approach. 

Purity control, molecular mass determination and molecular mass fingerprints can be performed either by electrospray ionization (ESI) or matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) MS. ESI is preferred for sequence determination by MSn and MALDI-TOF for molecular mass fingerprints. Both technologies are appropriate for molecular mass determination and purity control. We have edited a critical review on the use of MS strategies for discovery and peptide sequencing of bioactive peptide (25). 

Mass spectrometrie techniques that include continuous flow fast atom bombardment (FAB), electrospray ionization (ESI), and matrix assisted laser desorption (MALDI) have been applied successfully to protein structure investigations. (3) The hyphenation of electrospray ionization mass... 

The analysis of proteins by mass spectrometry has emerged as the techifique of choice for obtaining high performance results from small amounts of analyte. Interest in this analytical technique has increased primarily as the result of the introduction of the electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI) sources. These innovations permit nonvolatile molecules to be readily introduced into the gas phase. 

The past years have seen the development of two important ionization techniques electrospray ionization (ESI) and matrix-assisted laser desorption (MALDI), which have been used especially in conjunction with quadrupole, time of flight (TOF) and ion cyclotron (IC) analyzers. Both ionization techniques have revolutionized the essence of mass spectrometry itself, radically increasing the upper mass limit and thus the applicability of the mass spectrometric technique and indirectly affecting the endeavors for improved resolution and sensitivity. With these techniques, the analysis of peptides, proteins and oligonucleotides has become possible. The aim of this chapter is to demonstrate the capabilities of these techniques, especially electrospray mass spectrometry in conjunction with HPLC techniques, for the analysis of combinatorially generated compounds and libraries, and to exemplify and discuss both the potentials and limits of these analytical techniques. 

Mass spectrometry currently has assumed a central role in protein sequencing. This development has been possible with the introduction of two highly sensitive ionization techniques electrospray ionization (ESI) and matrix-assisted laser desorption and ionization (MALDI) and the advent of improved instrumentation capable of high-mass and high-sensitivity detection. Currently, biopolymers with a molecular mass over 100,000 Da are analyzed routinely. In the past, fast atom bombardment (FAB) [6,7] and Cf plasma desorption (PD) ionization [8] also played a limited role in protein sequencing. Mass spectrometry now has assumed... 

Mass spectrometry is an analytical technique that can determine precisely the atomic or the molecular weight of atoms or molecules once they have been ionized. There are four key elements in mass spectrometer the sample introduction, the source where ionization occurs, the mass analyzer, and the detector. Mass spectrometry can analyze many different types of samples that range from solid, liquid, or gases. First, the molecules have to be ionized either under vacuum or at atmospheric pressure. Depending on the ionization technique, either molecular ions (M ) with an odd electron number or protonated ions ([M + H] with an even electron number are formed in the positive mode and M , M or ([M - H] in the negative mode. Ionization techniques are often classified into soft ionization, where little or no fragmentation occurs, and hard ionization, where fragmentation is extensive. Electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI) are... 

The fast atom bombardment (FAB) ionization technique is of great historical importance in mass spectrometry, as it provided tbe first facile approach to applications to fragile biomolecules. When first introduced (Barber 1981), FAB created a sensation within the mass spectrometry community hut was supplanted after a few years by the newer techniques of electrospray ionization (ESI) and matrix assisted laser desorption ionization (MALDI). FAB is still used for some specialized applications. It was first developed as a means of overcoming an intrinsic limitation of... 

Three years earlier, in 2000, Scrivens and Jackson published a review paper with the same title [5], in which revolutionary technical advances in the field were described. In their words, before the so-called revolution, The majority of mass spectrometric studies of polymer systems required optional extraction of the additives from the polymer followed by a chemical or thermal degradation of the polymer itself. Due to partial degradation, the authors make a distinction between direct measurements and indirect measurements [5]. The mass spectra of many synthetic polymers are discussed, but they limit their review to spectra recorded using three ionization techniques, namely field desorption (FD), electrospray ionization (ESI), and matrix-assisted laser desorption/ionization (MALDI). For MS of synthetic polymers prior to the revolution, the authors refer the reader to other sources. 

Because of the advances in the gas-phase ionization of biomacromolecules, such as electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI), mass spectrometry (MS) has become a powerful tool for detection, identification, and structural analysis of proteins, peptides, and polynucleotides. The molecules ionized in a gas phase by these methods are subsequently analyzed by sector, quadrupole, ion-trap, or time-of-flight mass spectrometers. In particular, the MS systems consisting of ESI and triple-stage quadrupole (ESI/TSQ) or ion-trap (IT) mass spectrometry and MALDI time-of-flight (MALDl/TOF) mass spectrometry have been most widely applied to the field of protein chemistry for the accurate determination of molecular mass of proteins and peptides, determination of amino acid sequence, identification of proteins by peptide mass databases, and analysis of posttranslational modifications such as phosphorylation and glycosylation. In general, current techniques allow detenni-... 

IMS experiments may be performed using one of several MS ionization techniques secondary ion mass spectrometry (SIMS), laser desorption/ionization (LDI), desorption electrospray ionization (DESI), and matrix-assisted laser desorption/ionization (MALDI) (2). In general, these techniques offer complementary capabilities (3). SIMS imaging is favored for higher spatial resolution imaging over a low mass range (<1,000 Da), MALDI IMS covers a much wider mass range (up to and over 100,000 Da) but at somewhat lower spatial resolution, and DESI uses ambient pressure for analysis of small molecules but at lower spatial resolution. 

There are two principal components of mass spectrometers the ionization chamber, where ionization of the sample occurs, and the mass analyzer, where ion sorting and detection occur. Mass spectrometer instruments vary in design with regard to both of these components. Thus far we have mentioned only one ionization technique, electron impact (El). In Section 9.18A we discuss El ionization in more detail, as well as discuss two other important ionization methods electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI). 

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