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[[File:Surface_enhanced_laser_desorption_ionization.png|Surface enhanced laser desorption ionization|thumb]] [[File:Protein_pattern_analyzer.jpg|Protein pattern analyzer|thumb|left]] '''Surface-enhanced laser desorption/ionization''' ('''SELDI''') is a variant of the [[mass spectrometry]] technique that is used for the analysis of protein mixtures. SELDI is particularly useful in the field of [[proteomics]], where it is employed to identify and quantify proteins in complex biological samples. This technique is an advancement over traditional [[laser desorption/ionization]] (LDI) methods, incorporating a surface-enhanced process that improves the efficiency and sensitivity of protein detection.

==Overview==
SELDI technology relies on the interaction between proteins and chemically treated surfaces under specific conditions. These surfaces, known as SELDI chips, are designed with various chemical functionalities to selectively bind proteins based on their physical and chemical properties, such as [[pH]], [[ionic strength]], and [[hydrophobicity]]. After binding, the non-retained components are washed away, and the retained proteins are analyzed directly on the chip by laser desorption/ionization mass spectrometry.

==Principle==
The principle behind SELDI is similar to that of [[Matrix-Assisted Laser Desorption/Ionization]] (MALDI), but with a crucial difference in the sample preparation and analysis phase. In SELDI, the sample is applied directly to a chip with a specific surface chemistry that selectively binds proteins or peptides of interest. This selective binding is achieved through various surface chemistries, including hydrophobic, metal affinity, and ion exchange surfaces. Once the sample is applied and non-bound components are washed away, a laser is used to desorb and ionize the retained molecules, which are then analyzed by a mass spectrometer.

==Applications==
SELDI has been widely used in the field of proteomics for disease biomarker discovery, drug discovery, and basic biological research. Its ability to analyze complex biological samples with minimal sample preparation makes it a valuable tool for identifying proteins that may be differentially expressed in diseases such as [[cancer]], [[diabetes]], and [[neurodegenerative diseases]]. SELDI has also been applied in the analysis of small molecules, peptides, and DNA.

==Advantages and Limitations==
The main advantage of SELDI is its high throughput capability, allowing for the analysis of a large number of samples in a relatively short time. Additionally, its ability to analyze small amounts of sample and its sensitivity to low-abundance proteins make it an attractive method for proteomic studies. However, SELDI faces limitations in terms of quantification accuracy and reproducibility. The technique's reliance on surface binding properties can also introduce variability, and the identification of proteins directly from SELDI spectra can be challenging without additional information from tandem mass spectrometry (MS/MS) analyses.

==Conclusion==
Surface-enhanced laser desorption/ionization represents a significant advancement in the field of mass spectrometry, offering a powerful tool for the analysis of complex protein mixtures. Despite its limitations, SELDI's unique combination of selective surface binding and mass spectrometric analysis continues to make it a valuable technique in proteomics and biomarker discovery.

[[Category:Mass spectrometry]]
[[Category:Proteomics]]
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Surface-enhanced laser desorption/ionization - Revision history

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