Surface-enhanced laser desorption ionization protein chips with

The ProteinChip System from Ciphergen Biosystems uses patented SELDI (Surface-Enhanced Laser Desorption/Ionization) ProteinChip technology to rapidly perform the separation, detection, and analysis of proteins at the femtomole level directly from biological samples. ProteinChip Systems use ProteinChip Arrays which contain chemically (cationic, anionic, hydrophobic, hydrophilic, etc.) or biochemically (antibody, receptor, DNA, etc.) treated surfaces for specific interaction with proteins of interest. Selected washes create on-chip, high-resolution protein maps. This protein mass profile, or reten-tate map of the proteins bound to each of the ProteinChip Array surfaces, is quantitatively detected in minutes by the ProteinChip Reader. 

In a related approach, arrays with different types of surface chemistries such as hydrophobic, hydrophilic, anionic, and affinity are used to absorb certain protein groups from biological or patient samples. The chip-absorbed proteins are then directly detected by surface-enhanced laser desorption/ionization time-of-flight MS (SELDl-TOF MS) (Issaq et al. 2002). The resulting protein masses can be used in pattern analysis and thereby provide a useful diagnostic tool. 

Matrix-assisted laser desorption ionization (MALDI) and surface-enhanced laser desorption ionization (SELDI) have been used online with TOF-MS for protein differential profiles of intact or hydrolyzed biological matrices in proteomics. The potential use of affinity chips, grafted with specific Ab towards the drug compound for MALDI or SELDI, will bring sensitive and selective tools for macromolecules. Specific Ab towards either the intact protein or several signature peptides... 

The almost endless possibilities of mass spectrometry have been increased by yet another hopeful variant SELDI (surface-enhanced laser desorption ionization). SELDI combines protein chips with a UV-MALDl-TOF. The chips are solid aluminum strips coated with cationic or anionic ion exchangers, with hydrophile or hydrophobic molecules. Chips with activated surfaces are also available. These bind proteins covalently via their amino groups and enable you to coat chips with antibodies or receptors as you need them. Every chip has eight coated holes with a diameter of 1 mm. You apply the sample into the holes. Part of the pro-teins/peptides is adsorbed. The remainder is washed off. The adsorbed proteins/peptides are transferred into matrix and can then be analyzed in the mass spectrometer (Figure 7.8). What can SELDI do better than MALDI ... 

In 1993, Hutchens and co-workers described surface-enhanced laser desorption/ionization (SELDI) technique, an affinity technology, which has progressed over the last decade to become a powerful analytical, an on-plate approach (Hutchens and Yip 1993). SELDI is a distinctive form of laser desorption/ionization (LDI) mass spectrometry in which the EDI probe plays an active role in the homogenization, preconcentration, amplification, purification, extraction, enrichment digestion, derivatization, synthesis, separation, and detection with complementary techniques, prior to the desorption and ionization of the analytes by MALDI (Merchant and Weinberger 2000). The principle of this approach is very simple. Biomolecules are captured by adsorption, partition, electrostatic interaction, or affinity chromatography on a solid-phase protein chip surface. Although SELDI provides a unique sample preparation platform, it is similar to MALDI-MS in that a laser... 

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