Single-chain variable fragment

Single-chain variable fragment (scFv) is a type of antibody that is engineered for use in biotechnology. scFvs are derived from the variable regions of immunoglobulin molecules, and they are unique in that they are composed of a single polypeptide chain.

Structure

The structure of a scFv consists of the variable regions of the heavy (VH) and light (VL) chains of an antibody, linked together by a short peptide linker. This linker is usually flexible, allowing the VH and VL domains to move relative to each other. The linker is typically about 15 amino acids long, and it is designed to be too short to allow the VH and VL domains to fold together and form a traditional antigen binding site.

Production

scFvs are produced through recombinant DNA technology. The genes encoding the VH and VL domains are isolated from a hybridoma or B cell, and then they are linked together using a short DNA sequence that encodes the peptide linker. This construct is then inserted into a plasmid and expressed in a host organism, typically Escherichia coli or yeast.

Applications

scFvs have a wide range of applications in biotechnology and medicine. They can be used as research tools, for example in flow cytometry or immunohistochemistry. They can also be used in therapeutics, for example in cancer immunotherapy or as targeting agents in drug delivery systems. In addition, scFvs can be used in diagnostics, for example in ELISA tests or immunoassays.

Advantages and Disadvantages

One of the main advantages of scFvs is their small size, which allows them to penetrate tissues more effectively than full-size antibodies. They also have the advantage of being able to be produced in bacteria or yeast, which is cheaper and faster than producing full-size antibodies in mammalian cells.

However, scFvs also have some disadvantages. They have a shorter half-life in the body than full-size antibodies, and they may be less stable. In addition, because they are made up of a single polypeptide chain, they can only bind to one antigen at a time, whereas full-size antibodies can bind to two.

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  Animation of a single-chain variable fragment (scFv) rotation

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  Diagram of a single-chain variable fragment

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  Illustration of polyvalent single-chain variable fragments