Acids sinapinic

Sinapine acid sulphate, CjgH240jN. HSO4. SHjO, crystallises in leaflets, m.p. 127° (188°, dry). The thiocyanate, CigHj OjN. SCN. HjO, forms pale yellow needles, m.p. 178° iodide, m.p. 185-6°. When the thiocyanate is warmed with alkalis there is formed choline and sinapic acid, the acid was investigated by Remsen and Coale, and... 

MALDI shares many features with FAB in that it employs a matrix which transfers energy to an analyte molecule to facilitate the ionization of polar and thermally labile, high-molecular-weight molecules. In this case, however, the energy is provided by a pulsed laser at a wavelength which may be absorbed by a matrix material such as nicotinic or sinapinic acids. The ability to obtain mass... 

For PMMA/additive dissolutions, it was not possible to identify any additive characteristic mass peaks, either by direct laser desorption or with matrix-assistance (dithranol, DHBA or sinapinic acid, 4-hydroxy-3,5-dimethoxy-cinnamic acid). This has again been ascribed to very strong interaction between PMMA and additives, which suppresses desorption of additive molecules. Also, partial depolymerisation of pho-tolytically labile PMMA by laser irradiation may play a role, which leads to saturation of the detector by PMMA fragment-ions and disappearance of additive mass peaks below noise level. Meyer-Dulheuer [55] has also reported MALDI-TOFMS analysis of a coating/2-ethylhexyldiphenylphosphate sample. Quantitative determination of the additives by means of MALDI-ToFMS proved impossible. Possibly the development of reproducible (automated) sample handling procedures or thin films might overcome this problem. 

Despite the large number whole-cell MALDI protocols that have been tested a single approach has not yet been widely adopted. There remain different and sometimes conflicting reports in the literature regarding optimum methodologies.3 In addition to the ferulic acid matrix mentioned above sinapinic acid, a-yano-4-hydroxycinnamic acid, 2,4-hydroxyphenyl benzoic... 

A lot of features of MALDI are conveyed by its name it is a desorption ionization, produced by a laser beam, and assisted by a matrix (Figure 2.5). The analyte (1 pmol or less) is mixed with a suitable matrix in a 1 1000 or higher molar ratio. The matrix is composed of a compound with a strong absorption at the wavelength of the laser used. These two factors, matrix excess and its strong absorption, ensure that the energy from the laser pulse is absorbed by the matrix and not by the analyte, thus avoiding its decomposition. Nicotinic acid, sinapinic acid (SA), 2,5-dihydroxy benzoic acid (2,5-DHB) and 2-(4-hydroxyphenylazo)benzoic acid (HABA) are some of the most commonly used matrices for MALDI. 

Figure 2.9. Schematic of a matrix-assisted laser desorption/ionization (MALDI) event. The SEM micrograph depicts sinapinic acid-equine myoglobin crystal from a sample prepared according to the dried drop sample preparation method. In the desorption event neutral matrix molecules (M), positive matrix ions (M+), negative matrix ions (M-), neutral analyte molecules (N), positive analyte ions (+), and negative analyte ions (-) are created and/or transferred to the gas phase. Reprinted from A. Westman-Brinkmalm and G. Brinkmalm (2002). In Mass Spectrometry and Hyphenated Techniques in Neuropeptide Research, J. Silberring and R. Ekman (eds.) New York John Wiley Sons, 47-105. With permission of John Wiley Sons, Inc.

Fig. 10.3. Threshold fluence for positive ions of (O) cytochrome c and ( ) sinapinic acid as function of the molar matrix-to-protein ratio. Reproduced from Ref [42] by permission. John Wiley Sons, 1994.

Cinnamic acid OH derivatives H J> H Caffeic acid / -Coumaric acid o-Coumaric acid CH Ferulic acid Cinnamic acid Sinapinic acid COOH Flavonoids Flavones Apigenin q JT 11 Luteolin R2 Flavanonol 1 i IJ R3 V >r (+)-Taxifolin OH 0... 

Figure 14.6 Structures of some commonly used MALDI matrices (a) 2,5-dihydroxy benzoic acid (DHB), (b) a-cyano-4-hydroxy-cinnamic acid, and (c) sinapinic acid (SA). Combination of these acidic MALDI matrices with organic bases leads to the formation of ionic liquid matrices.

Most commonly used matrix systems are derivatives of benzoic acid (e.g., 2,5-dihydroxybenzoic acid (DHB), derivatives of cinnamic acid (e.g., a-cyano-4-hydroxycinnamic acid (CHCA) or sinapinic acid (SA) (Figure 14.6) as well as heteroaromatic compounds containing nitrogen but numberless other substances and substance classes have been applied as matrices [36]. 

Sinapinic acid see 3-(4-hydroxy-3,5-dimethoxyphenyl)acrylic acid. 

Purification of peptide-amphiphile 15 was achieved using a Vydac 214TP152022 C4 column (15-20 pm particle size, 300-A pore size, 250 x22 mm) at a flow rate of 5.0 ml-min1. The elution gradient was 30-100% B in 70 min where A was 0.05% TFA in H20 and B was 0.05% TFA in iPrOH with detection at 280 nm. MALDI-TOF-MS was performed using a sinapinic acid matrix. 

Sinapinic Acid (SPA) or a-Cyano-4-Hydroxy Cinaminic Acid (CHCA)... 

Nanoparticle-assisted laser desorption/ionization imaging mass spectrometry Nanostructure initiator mass spectrometry Oscillating capillary nebulizer Olanzapine Prostate cancers Sinapinic acid... 

MALDI-MS employs a matrix and the use of a matrix with the samples has several purposes extraction of analyte from the cocrystallization surface, formation of analyte-dropped crystals, and absorption of the laser energy for soft-ionization of analyte molecules into MS analyzer. The commonly used MALDI matrices include a-cyano-4-hydroxycinnamic acid (CHCA), 2,5-Dihydroxybenzoic acid (DHB), Sinapinic acid (SA), et al. [61], A typical matrix solution would comprise the matrix at a concentration of 10-20 mg/mL in a solvent that is compatible with the... 

The power of the method is greatly enhanced by using matrix assistance (matrix assisted laser desorption ionization, or MALDI). Two matrix materials, nicotinic acid and sinapinic acid, which have absorption bands coinciding with the laser employed, have found widespread use and sample molecular weights of up to two to three hundred thousand Da have been successfully analyzed. A few picomoles of sample are mixed with the matrix compound fol-... 

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