Material-enhanced laser desorption/ionization

Figure 3.10 Material-enhanced laser desorption/ionization (MELDI)-based biomarker discovery. (Courtesy of C. Huck and M. Rainer.)...

Another novel approach to utilizing affinity surfaces is referred to as the material-enhanced laser desorption/ionization (MELDI) technique [95] (Figure 3.10). This method was developed with the use of specially derivatized chromatographic materials (cellulose, silica, poly [glycidyl methacrylate/divinylbenzene] particles, and diamond powder) for fast and direct protein profiling to evaluate normal and pathological human serum samples. 

A new technique, known as material-enhanced laser desorption/ionization (MELDI), has become available for profiling proteins in complex mixtures [67], It uses derivatized carrier materials, such as cellulose, silica, poly(glycidyl methylacrylate/divinylbenzene), or diamond powder, to bind proteins from the sample. The carrier particles are derivatized with iminodiacetic acid (IDA) and loaded with ions to form [carrier-IDA-Cu +] complex, which is then added to the protein sample. The protein-bound carrier materials are spotted on the MALDI target, mixed with a MALDI matrix and analyzed by MALDI-TOF-MS. 

MELDI material-enhanced laser desorption/ionization... 

Qureshi, M.N., Stecher, G., Huck, C., and Bonn, G.K. 2010. Online coupling of thin layer chromatography with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry Synthesis and application of a new material for the identification of carbohydrates by thin layer chromatography/matrix free material enhanced laser desorption/ ionization mass spectrometry. Rapid Commun. Mass Spectrom., 24 2759-2764. 

Silica gel can be derivatized in multiple ways, e.g., by covalently binding ligands via Si-O bonds to its surface. Both surface-enhanced laser desorption/ionization (SELDI) and material-enhanced laser desorption/ionization (MELDI) make use of the presence of metal complexes on a silica gel surface to selectively adsorb target compounds via conplex formation ftom solution to a target surface [197]. Besides silica gel, also cellulose or glyddyl methacrylate particles, and even diamond powder have been enployed as carriers for the metal conplex-fiinctionalized groups [198,199]. 

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry has contributed remarkably to unravelling the termination and initiation steps of the styrene/CO copolymerisation catalysed by the highly active bis-chelated complex [Pd(bipy)2](Pp5)2 in TFE [40]. Chain-end group analysis of the material produced in the absence of BQ showed that the termination by P-H elimination is accompanied by three different initiators two palladium alkyls from Pd-H formed by reaction of the precursor with CO and water (a and b) and a palladium carboalkoxy species formed by reaction of the precursor with the fluorinated alcohol and CO (c) (Chart 7.4). The suppression of the chain-transfer by alcoholysis was proposed to be responsible for the enhanced stability of the palladium acyl intermediates and hence for the high molecular weight of the copolymers produced. 

MALDI MCM-41 MCR MD ME MEM MI MPM MRI MS MVA Matrix-assisted Laser Desorption/Ionization Mobile Crystalline Material-41 Multivariate Curve Resolution Molecular Dynamics Matrix-enhanced Magnetic Force Micrscopy Multivariate Image Multiphoton Microscopy Magnetic Resonance Imaging Mass Spectroscopy Multivariate Analysis... 

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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