Surface Enhanced Laser Desorption Ionization

Wright, G. L., Cazares, L. H., Leung, S.-M., Nasim, S., Adam, B.-L., Yip, T.-T., Schellhammer, P. F., Gong, L., and Vlahou, A. (2000). ProteinChip surface enhanced laser desorption/ionization (SELDI) mass spectrometry a novel protein biochip technology for detection of prostate cancer biomarkers in complex protein mixtures. Prostate Cancer and Prostatic Diseases 2, 264-276. 

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. 

Diamond DL, Zhang Y, Gaiger A, et al. Use of ProteinChip array surface enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS) to identify thymosin beta-4, a differentially secreted protein from lymphoblastoid cell lines. J. Am. Soc. Mass Spectrom. 2003 14 760-765. 

Also for MALDI, there is a special case worth mentioning. Surface-enhanced laser desorption/ionization (SELDI) is a technique that utilizes special sample plates [196, 197]. These have different modified surfaces, for example, hydrophobic, anionic, or antibody treated. Which type of surface to select depends on the application. After application of analyte the surface is washed according to a protocol leaving only the desired components on the target. Finally, a MALDI matrix is applied before analysis in the spectrometer. See Chapter 12 for an application example of SELDI. 

Surface enhanced laser desorption/ionization (SELDI) is a distinctive form of laser desorption ionization where the target plays an active role in the sample preparation procedure and ionization process [49]. Depending on the chemical or biochemical treatment, the SELDI surface acts as solid phase extraction or an affinity probe. Chromatographic surface is used for sample fractionation and purification of biological samples prior to direct analysis by laser desorption/ ionization. SELDI is mainly applied for protein profiling and in biomarker discovery by comparing protein profiles from control and patient groups. 

Boyle, M.D.P., Romer, T.G., Meeker, A.K., and Sledjeski, D.D., Use of surface-enhanced laser desorption ionization protein chip system to analyze streptococcal exotoxin B activity secreted by Streptococcus pyogenes, ]. Microbiol. Meth., 46, 87-89, 2001. 

Dare TO, Davies HA, Turton JA, et al. Apphcation of surface-enhanced laser desorption/ionization technology to the detection and identification of urinary parvalbumin-alpha a biomarker of compoimd-induced skeletal muscle toxicity in the rat. Electrophoresis 2002 23 3241-51. 

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. 

FT-ICR-Fourier transform-ion cyclotron resonance. MALDI-matrix-assisted laser desorption ionization. SELDI-surface-enhanced laser desorption/ionization. 

Mian S, Ball G, Hornbuckle J, et al. A prototype methodology combining surface-enhanced laser desorption/ionization protein chip technology and artificial neural network algorithms to predict the chemoresponsiveness of breast cancer cell lines exposed to Paclitaxel and Doxorubicin under in vitro conditions. Proteomics 2003 3(9) 1725-1737. 

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... 

FIGURE 7 Group B streptococcus infection-induced differential protein expression in nonhuman primate (A) and human (B) amniotic fluid samples by surface-enhanced laser desorption/ionization (SELDI-TOF MS) using normal-phase protein chip arrays. Spectrum from 2.5 to 15 kDa collected at 235 nm laser intensity. Detailed spectra show increased expression of the 3.5 and 10.8 kDa peaks between control and infected. Arrows indicate the unique peaks represented by polypeptides overexpressed in infection. 

Surface-Enhanced Laser Desorption-Ionization Protein Profiling... 

Banks RE, Stanley AJ, Cairns DA, Barrett JH, Clarke P, Thompson D, et al. Influences of blood sample processing on low-molecular-weight proteome identified by surface-enhanced laser desorption/ionization mass spectrometry. Clin Chem 2005 51(9) 1637 1649. 

Yu Y, Chen S, Wang LS, Chen WL, Guo WJ, Yan H, et al. Prediction of pancreatic cancer by serum biomarkers using surface-enhanced laser desorption/ionization-based decision tree classification. Oncology 2005 68(l) 79-86. Epub 2005 April 8. 

Guo J, Yang EC, Desouza L, Diehl G, Rodrigues MJ, Romaschin AD, et al. A strategy for high-resolution protein identification in surface-enhanced laser desorption/ionization mass spectrometry Calgranulin A and chaperonin 10 as protein markers for endometrial carcinoma. Proteomics 2005 5(7) 1953-1966. 

The Bik glycoprotein has an isoelectric point (p/) of 2.1 and is composed of a peptide and two glycoconjugate portions [30]. The predicted peptide sequence of Bik is helpful to understanding protein function. The peptide has Kunitz-binding domains I and II attached to the N-terminal peptide tail [31-33] (Fig. 2). Protein mass spectrometry by surface-enhanced laser desorption ionization (SELDI) in combination with detection by Bik antibodies has demonstrated that substantial variation exists in the Bik molecule [13,14]. 

The wide application of newly developed advanced Surface MALDI MS methods, such as laser desorption ionization (LDI), surface-enhanced laser desorption ionization (SELDI), direct ionization on silicon surface (DIOS), etc. have two shortcomings. First, problems with MALDI-TOF MS sample preparation for nano-sized systems have not been completely worked out. Second, the reliability and reproducibility of experimental data concerning similar bio-active systems is lacking. Sometimes molecular, associative and fragment ions cannot, be observed in the MALDI mass spectra. We are currently working on overcoming these difficulties with some encouraging results.13,14... 

RC-MS stems from the observation that mass spectra of peptides and proteins can be generated by laser activation of chromatographic surfaces placed on MALDI targets. The product application of RC-MS, called surface-enhanced laser desorption ionization-time of fiight (SELDI-TOF), refers to a mass spectrometry method for measuring native proteins adsorbed (retained) on various chemical or biochemical surfaces (Figure 4.11). Although the concept of laser desorption of intact proteins is well established, it has been commercially exploited only recently as a means... 

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