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"Peptides" redirects here. For the journal, see .
It has been suggested that
into this article. () Proposed since October 2014.
A tetrapeptide (example ---) with
green marked
blue marked
Peptides (from Gr. πεπτ??, "digested", derived from π?σσειν, "to digest") are naturally occurring biological molecules. They are short chains of
() bonds. The
are formed when the
group of one amino acid reacts with the
group of another. The shortest peptides are , consisting of 2 amino acids joined by a single peptide bond, followed by , , etc. A polypeptide is a long, continuous, and unbranched peptide chain. Hence, peptides fall under the broad chemical classes of biological
and , alongside , oligo- and , etc.
Peptides are distinguished from
on the basis of size, and as an arbitrary benchmark can be understood to contain approximately 50 or fewer amino acids. Proteins consist of one or more polypeptides arranged in a biologically functional way, often bound to
and , or to another protein or other
(, , etc.), or to complex . Finally, while aspects of the techniques that apply to peptides versus polypeptides and proteins differ (i.e., in the specifics of , , etc.), the size boundaries that distinguish peptides from polypeptides and proteins are not absolute: long peptides such as
have been referred to as proteins, and smaller proteins like
have been considered peptides.
Amino acids that have been incorporated into peptides are termed "residues" due to the release of either a hydrogen ion from the amine end or a hydroxyl ion from the carboxyl end, or both, as a water molecule is released during formation of each amide bond. All peptides except
residue at the end of the peptide (as shown for the tetrapeptide in the image).
Peptides are divided into several classes, depending on how they are produced:
Milk peptides 
Two naturally occurring
are formed from the milk protein
when digestive enz they can also arise from the
during the fermentation of milk.
Ribosomal peptides 
Ribosomal peptides are synthesized by
of . They are often subjected to
to generate the mature form. These function, typically in higher organisms, as
and signaling molecules. Some organisms produce peptides as , such as . Since they are translated, the
residues involved are restricted to those utilized by the ribosome.
However, these peptides frequently have , such as , , , , glycosylation and
formation. In general, they are linear, although
structures have been observed. More exotic manipulations do occur, such as racemization of L-amino acids to D-amino acids in .
Nonribosomal peptides 
are assembled by
that are specific to each peptide, rather than by the ribosome. The most common non-ribosomal peptide is , which is a component of the
defenses of most aerobic organisms. Other nonribosomal peptides are most common in , , and
and are synthesized by
enzyme complexes called nonribosomal peptide synthetases.
These complexes are often laid out in a similar fashion, and they can contain many different modules to perform a diverse set of chemical manipulations on the developing product. These peptides are often
and can have highly complex cyclic structures, although linear nonribosomal peptides are also common. Since the system is closely related to the machinery for building
and , hybrid compounds are often found. The presence of
often indicates that the compound was synthesized in this fashion.
Peptones are derived from animal milk or meat digested by . In addition to containing small peptides, the resulting spray-dried material [] includes fats, metals, salts, vitamins and many other biological compounds. Peptones are used in nutrient media for growing bacteria and fungi.
Peptide fragments 
Peptide fragments refer to fragments of proteins that are used to identify or quantify the source protein. Often these are the products of enzymatic degradation performed in the laboratory on a controlled sample, but can also be forensic or paleontological samples that have been degraded by natural effects.
Main article:
Solid-phase peptide synthesis on a rink amide
using -α--protected
Peptides received prominence in
for several reasons. The first is that peptides allow the creation of peptide antibodies in animals without the need to purify the
of interest. This involves synthesizing antigenic peptides of sections of the protein of interest. These will then be used to make antibodies in a rabbit or mouse against the protein.
Another reason is that peptides have become instrumental in , allowing the identification of proteins of interest based on peptide masses and sequence. In this case the peptides are most often generated by
separation of the proteins.
Peptides have recently been used in the study of
and function. For example, synthetic peptides can be used as probes to see where protein-peptide interactions occur- see the page on .
Inhibitory peptides are also used in clinical research to examine the effects of peptides on the inhibition of cancer proteins and other diseases. For example, one of the most promising application is through peptides that target . These particular peptides act as an , meaning that they bind to a cell in a way that regulates LHRH receptors. The process of inhibiting the cell receptors suggests that peptides could be beneficial in treating . However, additional investigations and experiments are required before the cancer-fighting attributes, exhibited by peptides, can be considered definitive.
The peptide families in this section are ribosomal peptides, usually with hormonal activity. All of these peptides are synthesized by cells as longer "propeptides" or "proproteins" and truncated prior to exiting the cell. They are released into the bloodstream where they perform their signaling functions.
Main article:
Main article:
(Vasoactive Intestinal Peptide; PHM27)
Pituitary Adenylate Cyclase Activating Peptide
27 (Peptide Histidine Isoleucine 27)
1-24 (Growth Hormone Releasing Hormone 1-24)
(NeuroPeptide Y)
(Peptide YY)
(Avian Pancreatic Polypeptide)
Pancreatic PolYpeptide
Main article:
() peptides
pentapeptides
- produced in myocardium & useful in medical diagnosis
- Lactotripeptides might reduce , although the evidence is mixed.
A polypeptide is a single linear chain of many amino acids, held together by .
is one or more polypeptide (more than about 50 amino acids long).
consists of only a few amino acids (between two and twenty).
Number of amino acids:
A monopeptide has one amino acid.
has two amino acids.
has three amino acids.
has four amino acids.
A pentapeptide has five amino acids.
A hexapeptide has six amino acids.
A heptapeptide has seven amino acids.
An octapeptide has eight amino acids (e.g., ).
A nonapeptide has nine amino acids (e.g., ).
A decapeptide has ten amino acids (e.g.,
An undecapeptide (or monodecapeptide) has eleven amino acids, a dodecapeptide (or didecapeptide) has twelve amino acids, a tridecapeptide has thirteen amino acids, and so forth.
An icosapeptide has twenty amino acids, a tricontapeptide has thirty amino acids, a tetracontapeptide has forty amino acids, and so forth.
is a peptide that is active in association with neural tissue.
is a peptide that has a
connected to it, and
are lipopeptides that interact with GPCRs.
is a peptide that acts as a .
is a mixture of peptides produced by the hydrolysis of proteins. The term is somewhat archaic.
The term peptide has been incorrectly or unclearly used to mean illegal
and peptide hormones in sports doping matters: illegal secretagogue peptides are classified as Schedule 2 (S2) prohibited substances on the
(WADA) Prohibited List, and are therefore prohibited for use by professional athletes both in and out of competition. Such peptide secretagogues have been on the WADA prohibited substances list since at least 2008. The Australian Crime Commission (incorrectly using the term peptides) cited the alleged misuse of the following illegal peptide secretagogues used in Australian sport - and specifically by Jobe Watson from the Essendon Football Club: growth hormone releasing hormones , ,
hexarelin. There is ongoing controversy on the legality of using peptide secretagogues in sports.
and ) to peptides, but with different properties.
, describing addition of peptide sequences to enable protein isolation or detection
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: Hidden categories:Small molecule polypeptide
小分子多肽
Small molecule polypeptide的用法和样例：
ConclusionThe active component of anti-HBV Specific TF was a small molecule that consisted of nucleotide and polypeptide.
结论抗乙肝转移因子活性组分是低分子核苷酸与多肽组成的复合物。
The small molecule causing the conformational change is an allosteric effector.
引起结构变化的小分子叫做变构效应
Small molecule atomic particles, atoms extranuclear electron transfer.
分子原子小粒子，原子核外电子转。
OBJECTIVE To obtain small molecule compounds possessing analgesic activity.
摘要目的获得具有镇痛活性的小分子化合物。
Small molecule polypeptide的海词问答与网友补充：
Small molecule polypeptide的相关资料：
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