chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions ...

, solid-phase synthesis is a method in which

molecule A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioch ...

s are covalently bound on a

solid Solid is one of the State of matter#Four fundamental states, four fundamental states of matter (the others being liquid, gas, and Plasma (physics), plasma). The molecules in a solid are closely packed together and contain the least amount o ...

support material and synthesised step-by-step in a single

reaction vessel A chemical reactor is an enclosed volume in which a chemical reaction takes place. In chemical engineering, it is generally understood to be a process vessel used to carry out a chemical reaction, which is one of the classic unit operations in chem ...

utilising selective

protecting group A protecting group or protective group is introduced into a molecule by chemical modification of a functional group to obtain chemoselectivity in a subsequent chemical reaction. It plays an important role in multistep organic synthesis. In many ...

chemistry. Benefits compared with normal

synthesis Synthesis or synthesize may refer to: Science Chemistry and biochemistry *Chemical synthesis, the execution of chemical reactions to form a more complex molecule from chemical precursors ** Organic synthesis, the chemical synthesis of organ ...

in a

liquid state A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, an ...

include: * High efficiency and throughput * Increased simplicity and speed The reaction can be driven to completion and high yields through the use of excess

reagent In chemistry, a reagent ( ) or analytical reagent is a substance or compound added to a system to cause a chemical reaction, or test if one occurs. The terms ''reactant'' and ''reagent'' are often used interchangeably, but reactant specifies a ...

. In this method, building blocks are protected at all reactive

functional group In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the rest ...

s. The order of functional group reactions can be controlled by the order of deprotection. This method is used for the synthesis of

peptides Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides. A p ...

, deoxyribonucleic acid ( DNA), ribonucleic acid (

RNA Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydra ...

), and other molecules that need to be synthesised in a certain alignment. More recently, this method has also been used in

combinatorial chemistry Combinatorial chemistry comprises chemical synthetic methods that make it possible to prepare a large number (tens to thousands or even millions) of compounds in a single process. These compound libraries can be made as mixtures, sets of individua ...

and other synthetic applications. The process was originally developed in the 1950s and 1960s by

Robert Bruce Merrifield Robert Bruce Merrifield (July 15, 1921 – May 14, 2006) was an American biochemist who won the Nobel Prize in Chemistry in 1984 for the invention of solid phase peptide synthesis. Early life He was born in Fort Worth, Texas, on 15 July 1921, t ...

in order to synthesise peptide chains, and which was the basis for his 1984

Nobel Prize in Chemistry ) , image = Nobel Prize.png , alt = A golden medallion with an embossed image of a bearded man facing left in profile. To the left of the man is the text "ALFR•" then "NOBEL", and on the right, the text (smaller) "NAT•" then "M ...

. In the basic method of solid-phase synthesis, building blocks that have two functional groups are used. One of the functional groups of the building block is usually protected by a protective group. The starting material is a bead which binds to the building block. At first, this bead is added into the solution of the protected building block and stirred. After the reaction between the bead and the protected building block is completed, the solution is removed and the bead is washed. Then the protecting group is removed and the above steps are repeated. After all steps are finished, the synthesised compound is chemically cleaved from the bead. If a compound containing more than two kinds of building blocks is synthesised, a step is added before the deprotection of the building block bound to the bead; a functional group which is on the bead and did not react with an added building block has to be protected by another protecting group which is not removed at the deprotective condition of the building block. Byproducts which lack the building block of this step only are prevented by this step. In addition, this step makes it easy to purify the synthesised compound after cleavage from the bead.

Solid-Phase Peptide Synthesis (SPPS)

Solid-phase synthesis is a common technique for

peptide synthesis In organic chemistry, peptide synthesis is the production of peptides, compounds where multiple amino acids are linked via amide bonds, also known as peptide bonds. Peptides are chemically synthesized by the condensation reaction of the carboxyl ...

. Usually, peptides are synthesised from the

carbonyl group In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups. A compound containing a ...

side (C-terminus) to

amino group In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituent such a ...

side (N-terminus) of the

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...

chain in the SPPS method, although peptides are biologically synthesised in the opposite direction in cells. In peptide synthesis, an amino-protected amino acid is bound to a solid phase material or resin (most commonly, low cross-linked

polystyrene Polystyrene (PS) is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per unit weight. It is a ...

beads), forming a

covalent bond A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atoms ...

between the carbonyl group and the resin, most often an

amido In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a compound with the general formula , where R, R', and R″ represent organic groups or hydrogen atoms. The amide group is called a peptide bond when it is ...

or an

ester In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ar ...

bond. Then the amino group is deprotected and reacted with the carbonyl group of the next, N-protected, amino acid. The solid phase now bears a dipeptide. This cycle is repeated to form the desired peptide chain. After all reactions are complete, the synthesised peptide is cleaved from the bead. The protecting groups for the amino groups mostly used in the peptide synthesis are 9-fluorenylmethyloxycarbonyl group ( Fmoc) and t-butyloxycarbonyl ( Boc). A number of amino acids bear functional groups in the side chain which must be protected specifically from reacting with the incoming N-protected amino acids. In contrast to Boc and Fmoc groups, these have to be stable over the course of peptide synthesis although they are also removed during the final deprotection of peptides.

Solid-phase synthesis of DNA and RNA

Relatively short fragments of DNA,

, and modified oligonucleotides are also synthesised by the solid-phase method. Although

oligonucleotides Oligonucleotides are short DNA or RNA molecules, oligomers, that have a wide range of applications in genetic testing, research, and forensics. Commonly made in the laboratory by solid-phase chemical synthesis, these small bits of nucleic acids c ...

can be synthesised in a flask, they are almost always synthesised on solid phase using a DNA/RNA synthesizer. For a more comprehensive review, see

oligonucleotide synthesis Oligonucleotide synthesis is the chemical synthesis of relatively short fragments of nucleic acids with defined chemical structure (sequence). The technique is extremely useful in current laboratory practice because it provides a rapid and inexpens ...

. The method of choice is generally phosphoramidite chemistry, developed in the 1980s.

Solid-Phase Peptide Synthesis (SPPS)

Solid-phase synthesis of DNA and RNA

See also

References

Further reading