Material-enhanced MALDI

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. 

Liang C, Yuan CY, Warmack RJ, Barnes CE, Dai S (2002) Ionic Uquids a new class of sensing materials for detection of oiganic vapors based on the use of a quartz crysteil microbalance. Anal Chem 74 2172-2176 MankM, Stahl B, Boehm G (2004) 2,5-Dihydroxybenzoic acid butylamine and other ionic liquid matrixes for enhanced MALDI-MS analysis of biomolecules. Anal Chem 76 2938-2950 Mantz AR, Trulove PC (2003) Physicochemical properties of ionic liquids. In Wasserscheid P, Welton T (eds) Ionic liquids in synthesis. Wiley, Berlin, pp 75-143... 

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-... 

Two variations of conventional SIMS have evolved. In one, known as matrix-enhanced SIMS, the MALDI sample preparation protocol is used to coat the sample surface with an organic acid (e.g., 2,5-dihydroxybenzoic acid) or other suitable matrix material to improve ionization efficiency [24,25], This approach has been used to image brain tissue samples from freshwater snails (Lymnaea stagnalis). Another variation employs a coating of a thin layer of gold or other metals to enhance analytical signals [26], This method, known as metal-assisted SIMS, provides images with improved spatial and chemical resolution. 

It should be noted that, upon irradiation with the laser, not all of the sample will be consumed consequently, when the initial measurements have been completed the material can be redissolved and treated chemically or enzymatically prior to further mass spectrometric measurements. In the case of glycans, the most common MALDI matrix to be used is 2,5-dihydroxybenzoic acid (DHB). The most recently used matrices have been reviewed [43], with mixtures of DHB and coumarin analogs having been reported to provide enhanced ionization conditions for dextran chains [44]. 

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