PROTEIN MICROARRAYNAVEED UP MUSHTAQ

Protein microarrayA protein microarray (protein chip)is a high throughput method used to track the interactions & activities of proteins,& to determine their functions,& determining function on a large scale.Protein microarrays,are miniaturised and parallel assay systems that contain small amounts of purified proteins in a high density format.They allow simultaneous determination of a great variety of analytes from small amounts of samples within a single experiment.

This technology can complement other techniques,such as mass spectrometry & yeast two-hybrid assays,to identify thousands of protein-protein interactions.Protein arrays can be screened for their ability to bind other proteins in a complex,receptors,antibodies;lipids;enzymes;pepyides;harmones;specific DNA sequence.

Preparation of protein microarray Protein microarrays are typically prepared by immobilizing proteins onto a microscope slide using a standard contact spotter or non contact microarray.Different methods of arraying the proteins:-

Robotic method Ink jetting method

Piezoelectric spotting Photoliyhography.

In these methods,robotic is contact microarray method while the other three are non contact microarray methods.

A variety of slide surfaces can be used.popular types include aldehyde & epoxy-derivatized glass surfaces for random attachment through amines,nitrocellulose or gel coated slides and nickel coated slides for affinity attachment of HIS 6-tagged proteins.After proteins are immobilised on the slides,they can be probed for a variety of functions/activities.Typically the probe molecules are labelled with fluoresent dye,so that when the probe binds to the protein it results in a fluoresent signal.Finally the resulting signals are usually measured by detecting these labels.

TYPES OS PROTEIN MICROARRAYS There are three types of protein microarrays

that are currently used to study the biochemical activities of proteins.

Analytical protein microarraysFunctional protein microarrays

Reverse phase protein microarrays.

1. Analytical microarrays:-Analytical microarrays(or antibody microarrays) have antibodies arrays on solid surface,and are used to detect proteins in biological samples.Often a second is used to detect a protein that is captured by the antibody attached to the solid phase,in a principle similar to that of sand wich immunoassay, in which the first antibody is spotted on the array and then a captured antigen on the chip is detected with a second antibody that recognises a different part of antigen.

2.FUNCTIONAL PROTEIN MICROARRAYS:-Also known as target protein array.With functional protein microarrays purified recombinant protein are immobilised onto the solid phase.Functional protein microarrays have recently been applied to many aspects of discovery based biology,including protein-protein,protein-lipid,protein-DNA,protein-drug,&protein –peptide iinteractions.These can be used to identify enzyme substrates.These can also be used to detect antibodies in a biological specimen to profile an immune response.

3.REVERSE PHASE PROTEIN MICROARRAY:-Involves complex samples, such as tissue lysates.cells are isolated from various tissues of interest and lysed.The lysate is arranged onto the microarray & probed with antibodies against the target protein of interest.These antibodies are typically detected with chemiluminescent,fluoresent or colorimetric assays.RPAs allow for the determination of the presence of altered proteins or other agents that may be the result of disease.Specifically,post translationl modifications,which are typically altered as a result of disease can be detected using RPAs.

APPLICATIONS:-There are five major areas where protein arrays are being applied:diagnostics,proteomics,protein functional analysis,antibody characterisation & treatment.Diagnostics involves the detection of antigens & antibodies in blood samples;to discover new disease biomarkers;the monitoring of disease states & responses to therapy in personalised medicine;the monitoring of environment & food.Proteomics pertains to protein expression profilling i.e;which proteins are expressed in the lysate of a part of cell.

Protein functional analysis is the identification of protein-protein interactions,protein-phospholipid interactions,small molecule targets,enzymatic substrates & receptor ligands.Antibody characterization is characterizing cross reactivity,specificity & mapping epitopes.Treatment development involves the development of antigen-specific therapies for autoimunity,cancer & allergies;the identification of small molecule targets that could potentially be used as new drugs.

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