Peptidebased Ligands

In the last few years, peptide libraries have been a major area of development for the selection of biologically active peptides. These libraries offer the opportunity to study interactions between proteins and their natural ligand and are being used as potential drugs, antimicrobials and enzyme inhibitors, as bioactive peptides and as ligands for protein purification. Peptide libraries can be generated either by phage display or synthetic solid- or solution-phase chemical approaches. One of the most widespread and commonly used peptide-based technologies, phage display was conceived in 1985 by Smith and has been revolutionary in the synthesis, diversity and application of random peptide libraries in the search for novel protein-binding ligands for purification, structural and functional studies.

Random peptides are displayed on the surface of a filamentous bacteriophage (M13 or related bacteriophages) by fusion of the desired DNA sequence with either the minor (gill) or major (gVIII) coat proteins of the bacteriophage. Multiple copies (five to thousands) of the peptide are then expressed on the bac-teriophage surface owing to the presence of several copies of the coat proteins. Preparation of a large number of random oligonucleotides helps generate a combinatorial library of several millions of pep-tides. Selection of the phage particles expressing the peptide sequence with the desired activity and selectivity is performed through a process termed 'bio-panning'. The desired receptor for the peptides is immobilized on a solid support and the peptide-phage particles are loaded. The peptide-phage assemblies that do not bind wash off and the ones bound are eluted and amplified in Escherchia coli. The entire process is repeated 2-3 times to wash away any nonspecifically or weakly bound assemblies. The sequence of the selected peptide is determined by sequencing the coding region of the viral DNA.

The criteria for evaluation of peptide libraries includes generation of all possible combinations (millions) and numbers of peptide sequences to give the maximum probability of finding success. This aspect highlights the importance of rapid and efficient high-throughput screening for analysis of thousands or hundreds of millions of peptide candidates. The length of the sequences should be such that they include equimolar amounts of the tetramers and hexamers and the library should incorporate natural L-amino acids, their D-counterparts and unnatural amino acids.

In comparison with synthetic peptide synthesis, phage display is less labour-intensive and does not involve the painstaking synthesis of limited numbers of peptides. The peptide libraries can help localize epitopes on the surfaces of antibodies (monoclonal or polyclonal), act as enzyme inhibitors, mimic cytokines, and DNA binding proteins may be used in the design of novel ligands for peptide receptors. The ability to identify regions in a protein that interact with certain peptides without dependence on structural data and other pre-existing data is remarkable. The opportunities in drug and ligand discovery are substantiated by a number of remarkable applications in the literature.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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