Hormonal

ACTH 1-13

N-terminal thirteen of corticotropin

13 residues · 1624 Da · 115 atoms

The same thirteen residues as alpha-MSH but without the caps at either end. Putting the two next to each other shows exactly what an acetyl and an amide weigh.

Reference entry · not stocked

ACTH 1-24

Corticotropin residues 1 to 24

24 residues · 2933 Da · 208 atoms

Twenty-four residues, the shortest fragment of corticotropin that keeps full activity at the receptor. The first thirteen are alpha-MSH, which is also in this library, so the overlap is visible directly.

Reference entry · not stocked

Alarelin

GnRH analogue with D-alanine at six

9 residues · 1167 Da · 84 atoms

Nine residues opening with a pyroglutamate ring and closing with an ethylamide, both drawn. D-alanine at position six is the substitution that protects it from cleavage.

Reference entry · not stocked

Alpha-MSH

Melanocyte stimulating hormone

13 residues · 1665 Da · 118 atoms

Thirteen residues capped at both ends, an acetyl at one and an amide at the other, both drawn. The natural hormone that Melanotan I and II are analogues of, so it is worth comparing all three side by side.

Reference entry · not stocked

Angiotensin 1-7

7 residues · 899 Da · 126 atoms

Seven residues, angiotensin II minus its terminal phenylalanine. That single missing residue reverses much of what the parent does.

Reference entry · not stocked

Angiotensin I

10 residues · 1296 Da · 93 atoms

Ten residues. The enzyme that makes blood pressure medicine a category cuts the last two off this to make angiotensin II, which is also here. Seeing the two together shows exactly what that enzyme removes.

Reference entry · not stocked

Angiotensin II

Octapeptide of the renin-angiotensin system

8 residues · 1046 Da · 146 atoms

Eight residues carrying three aromatic side chains and a histidine imidazole. One of the most studied peptides in physiology.

Reference entry · not stocked

Angiotensin III

Angiotensin II minus its first residue

7 residues · 931 Da · 134 atoms

Seven residues. Angiotensin II with the aspartate at the front removed. Four members of this cascade are in the library and they differ only by what has been trimmed from the ends.

Reference entry · not stocked

Angiotensin IV

6 residues · 775 Da · 110 atoms

Six residues, two shorter than angiotensin II at the N-terminal end, and it acts at a different receptor entirely.

Reference entry · not stocked

ANP

Atrial natriuretic peptide

28 residues · 3080 Da · 214 atoms

Twenty-eight residues with a single disulfide closing a ring of seventeen, which is most of the molecule, leaving a short tail at each end. Every peptide in this family is built on that same seventeen-residue ring.

Reference entry · not stocked

Beta-MSH

22 residues · 2661 Da · 188 atoms

Twenty-two residues, the longest of the three melanocortin-stimulating peptides, with the same His-Phe-Arg-Trp core buried in the middle rather than sitting near an end.

Reference entry · not stocked

Big Endothelin-1

The uncleaved precursor of endothelin-1

38 residues · 4283 Da · 298 atoms

Thirty-eight residues carrying the same two nested disulfides as endothelin-1, with the tail that gets cut off still attached. Both are in the library, so the cleavage is visible directly.

Reference entry · not stocked

BNP-32

32 residues · 3464 Da · 239 atoms

Thirty-two residues. The ring between its two cysteines is the same size as the one in ANP and overlaps it heavily, but the tails on either side are longer and different. Both are here.

Reference entry · not stocked

Bombesin

14 residues · 1620 Da · 114 atoms

Fourteen residues capped at both ends in different ways: a pyroglutamate ring at the start and an amide at the finish. Originally isolated from frog skin.

Reference entry · not stocked

Bradykinin

Nine-residue kinin

9 residues · 1060 Da · 76 atoms

Nine residues with three prolines and arginine at both ends. Modelled in a polyproline-II conformation because the prolines leave the backbone little else to do.

Reference entry · not stocked

Bradykinin 1-5

Stable bradykinin fragment

5 residues · 573 Da · 82 atoms

Five residues from the front of bradykinin, which is also here. Two prolines in five keep it extended.

Reference entry · not stocked

Calcitonin (salmon)

32 residues · 3432 Da · 239 atoms

Thirty-two residues opening with a small ring: the cysteines at one and seven are joined by a disulfide, and the rest of the chain runs on from it as a helix. The salmon form is used in preference to the human one because it binds far more tightly.

Reference entry · not stocked

CCK-8

Cholecystokinin octapeptide

8 residues · 1063 Da · 134 atoms

Eight residues ending in an amide, the smallest fragment of cholecystokinin that stays active. Two methionines and a tryptophan carry most of the mass.

Reference entry · not stocked

CGRP

Calcitonin gene-related peptide

37 residues · 3789 Da · 265 atoms

Thirty-seven residues with a small disulfide ring at the front and a long helical body. Cut from the same gene as calcitonin by splicing the message differently, and both are in the library.

Reference entry · not stocked

CNP-22

22 residues · 2198 Da · 151 atoms

Twenty-two residues, and the disulfide closes onto the very last one, so unlike its two relatives here this peptide has no tail behind the ring at all. Putting all three side by side shows the family reduced to its core.

Reference entry · not stocked

Corticotropin releasing hormone

41 residues · 4758 Da · 333 atoms

Forty-one residues in a long helix. The peptide the whole urocortin and sauvagine family is named after, and both of those are also in this library.

Reference entry · not stocked

Deslorelin

GnRH analogue with D-tryptophan at six

9 residues · 1282 Da · 93 atoms

The same nine-residue frame as alarelin with D-tryptophan at six instead of D-alanine. Five members of this family are in the library, and lining them up shows that almost all of the variation is at position six.

Reference entry · not stocked

Elcatonin

Calcitonin analogue

32 residues · 3434 Da · 239 atoms

Thirty-two residues. In the real molecule the disulfide that closes salmon calcitonin is replaced by a carbon bridge, which the engine cannot draw, so the two cysteines are shown free here. Everything else is exact, and salmon calcitonin is in the library for comparison.

Reference entry · not stocked

Eledoisin

Tachykinin from octopus

11 residues · 1188 Da · 83 atoms

Eleven residues opening with a pyroglutamate ring and closing with an amide, both drawn. Shares its final five residues with substance P and neurokinin A, which is what makes it a tachykinin.

Reference entry · not stocked

Endothelin-1

21 residues · 2492 Da · 171 atoms

Twenty-one residues held by two separate disulfide bridges, one inside the other, which is why the front half is folded so tightly. Both bonds are drawn, and the chain is folded until each reaches a real bonding distance rather than having the lines drawn across it.

Reference entry · not stocked

Endothelin-2

21 residues · 2547 Da · 177 atoms

Twenty-one residues differing from endothelin-1 at two positions only. Both are here, along with the third family member and the uncleaved precursor.

Reference entry · not stocked

Endothelin-3

The third endothelin

21 residues · 2643 Da · 184 atoms

Twenty-one residues, the most divergent of the three, though the cysteine positions and therefore the fold are unchanged.

Reference entry · not stocked

Felypressin

Phenylalanine lysine vasopressin

9 residues · 1040 Da · 72 atoms

Two substitutions from vasopressin: phenylalanine at two and lysine at eight. Four peptides in this family are in the library, differing at one or two positions each.

Reference entry · not stocked

Fertirelin

GnRH analogue with an ethylamide terminus

9 residues · 1153 Da · 83 atoms

Gonadorelin shortened by its terminal glycine and finished with an ethylamide, keeping the natural glycine at position six.

Reference entry · not stocked

Gamma-MSH

11 residues · 1513 Da · 108 atoms

Eleven residues carrying the His-Phe-Arg-Trp core that every melanocortin peptide is built around. Alpha-MSH and ACTH 1-24 are also here, and the shared four residues are easy to find in all three.

Reference entry · not stocked

Gastrin-14

14 residues · 1833 Da · 130 atoms

Fourteen residues, five of them consecutive glutamates, which makes this one of the most acidic chains in the library. It shares its last four residues with CCK-8, which is also here.

Reference entry · not stocked

Gastrin-17

17 residues · 2098 Da · 149 atoms

Seventeen residues opening with a pyroglutamate ring and carrying a run of five glutamates in the middle, which makes it one of the most acidic chains here. Gastrin-14 is also in the library.

Reference entry · not stocked

Gonadorelin

Gonadotropin releasing hormone

10 residues · 1182 Da · 85 atoms

Ten residues beginning with pyroglutamate, a glutamate whose side chain has closed back onto its own backbone nitrogen to make a five-membered ring. That ring is drawn here. It is the natural start of this whole family and it is what protects that end of the chain.

Reference entry · not stocked

Insulin A-chain

The shorter of insulin's two chains

21 residues · 2384 Da · 163 atoms

Twenty-one residues carrying four cysteines. In whole insulin two of them bridge to the B-chain and one pair closes an internal loop; shown alone here, so the sulphurs are drawn free.

Reference entry · not stocked

Insulin B-chain

The longer of insulin's two chains

30 residues · 3430 Da · 242 atoms

Thirty residues. The two cysteines are the ones that bond across to the A-chain in the whole hormone. Both chains are in this library, so the pair can be compared.

Reference entry · not stocked

Kallidin

Lys-bradykinin

10 residues · 1188 Da · 85 atoms

Bradykinin with a lysine added to the front, which is how it is released from its precursor before that residue is trimmed off.

Reference entry · not stocked

Kassinin

12 residues · 1335 Da · 93 atoms

Twelve residues. Another member of the same family, ending in the shared five-residue motif.

Reference entry · not stocked

Kisspeptin-10

C-terminal decapeptide of kisspeptin

10 residues · 1302 Da · 94 atoms

Ten residues, the shortest fragment that retains activity at its receptor. The C-terminal amide is required; the free acid is inactive, which is why it is modelled with the amide cap.

In our catalogue

Leuprolide

9 residues · 1209 Da · 87 atoms

Gonadorelin shortened by one residue, with D-leucine at six and an ethylamide rather than the usual amide at the end. Both are drawn. The ethyl group is two carbons, and it is the whole difference between this and a plain amide.

Reference entry · not stocked

Lypressin

Lysine vasopressin

9 residues · 1056 Da · 73 atoms

Vasopressin with lysine at position eight in place of arginine. One residue, and the ring and tail architecture is otherwise identical, so it sits naturally beside vasopressin and oxytocin here.

Reference entry · not stocked

Melanotan I

Afamelanotide

13 residues · 1647 Da · 118 atoms

Alpha-MSH with two substitutions: the methionine at four becomes norleucine, which cannot oxidise, and the phenylalanine at seven becomes its D form, whose side chain is mirrored here. Two residues are the whole difference.

In our catalogue

Melanotan II

Cyclic melanocortin analogue

7 residues · 1024 Da · 145 atoms

Seven residues closed into a ring by a side-chain lactam: the aspartate at two and the lysine at seven are joined directly, so the ring hangs off the middle of the chain rather than closing it end to end. The N-terminus is acetylated and position one is norleucine.

In our catalogue

Motilin

22 residues · 2699 Da · 190 atoms

Twenty-two residues with a hydrophobic front end and a strongly charged tail.

Reference entry · not stocked

Neurokinin A

Tachykinin decapeptide

10 residues · 1133 Da · 79 atoms

Ten residues ending in the amide that defines this family. Shares its last five residues with substance P, which is also in this library.

Reference entry · not stocked

Neurokinin B

Tachykinin decapeptide

10 residues · 1210 Da · 84 atoms

Ten residues. The third of the three human tachykinins, all of which are now in this library alongside four from other animals.

Reference entry · not stocked

Neuromedin B

Bombesin-like decapeptide

10 residues · 1132 Da · 80 atoms

Ten residues ending in an amide, closely related to bombesin. The tryptophan and histidine in the middle are shared across the family.

Reference entry · not stocked

Neuromedin C

Gastrin releasing peptide 18-27

10 residues · 1120 Da · 79 atoms

Ten residues, the C-terminal fragment of gastrin releasing peptide. Almost identical to bombesin at the business end.

Reference entry · not stocked

Neuromedin N

6 residues · 746 Da · 117 atoms

Six residues sharing their last four with neurotensin, which is also here, and cut from the same precursor. The two are made by cutting one protein in two places.

Reference entry · not stocked

Neuromedin U-8

8 residues · 1111 Da · 160 atoms

Eight residues, the shortest active form. Two arginines and a proline in the back half, which is where the activity sits.

Reference entry · not stocked

Neuropeptide Y

36 residues · 4272 Da · 302 atoms

Thirty-six residues with a proline-rich front end and a long helical tail, which is the shape this whole family shares. Drawn without hydrogens to stay readable at this size.

Reference entry · not stocked

Ornipressin

Ornithine vasopressin

9 residues · 1042 Da · 72 atoms

Vasopressin with ornithine at eight, a lysine one carbon shorter. The disulfide ring is drawn closed, with the chain folded until the two sulphurs reach a real bonding distance.

Reference entry · not stocked

Oxytocin

9 residues · 1007 Da · 69 atoms

A nine-residue peptide whose first and sixth residues are cysteines joined by a disulfide bridge, closing six of the nine into a ring with a three-residue tail. The bridge is drawn as a real bond between the two sulphurs, and neither carries a thiol hydrogen because a cystine has none.

Reference entry · not stocked

PHM-27

27 residues · 2985 Da · 210 atoms

Twenty-seven residues named for the histidine it starts with and the methionine it ends with. Cut from the same precursor as VIP, which is also in the library, and built to the same helical plan.

Reference entry · not stocked

Physalaemin

Tachykinin from amphibian skin

11 residues · 1265 Da · 89 atoms

Eleven residues with the same pyroglutamate opening and the same Phe-Xaa-Gly-Leu-Met ending that defines this family.

Reference entry · not stocked

Prolactin-releasing peptide

31 residues · 3664 Da · 259 atoms

Thirty-one residues. Named for what it was first thought to do, which turned out not to be its main role, and the name stuck.

Reference entry · not stocked

PT-141

Bremelanotide

7 residues · 1025 Da · 144 atoms

The same ring as Melanotan II, differing only at the C-terminus, which is a free acid here rather than an amide. One atom of difference between two compounds, which is why they are worth seeing side by side.

In our catalogue

PTH (1-34)

The active fragment of parathyroid hormone

34 residues · 4118 Da · 289 atoms

Thirty-four residues, the shortest fragment of parathyroid hormone that retains full activity. The full hormone is 84 residues, so this is the part that matters, drawn as the helix it forms.

Reference entry · not stocked

Sauvagine

40 residues · 4599 Da · 322 atoms

Forty residues, strongly helical, opening with a pyroglutamate ring. Originally from frog skin and closely related to urocortin, which is also here.

Reference entry · not stocked

Secretin

27 residues · 3039 Da · 214 atoms

Twenty-seven residues. The founding member of the family that also contains glucagon, VIP and PACAP, all of which are here, and all of which open with histidine-serine-aspartate.

Reference entry · not stocked

Somatostatin-14

14 residues · 1638 Da · 115 atoms

Fourteen residues with cysteines at three and fourteen joined by a disulfide, closing almost the whole chain into a large ring. Three aromatic side chains sit inside it.

Reference entry · not stocked

Substance P

Undecapeptide tachykinin

11 residues · 1348 Da · 95 atoms

Eleven residues ending in the amide that every tachykinin shares. Two prolines near the N-terminus stiffen that end of the chain.

Reference entry · not stocked

Terlipressin

Triglycyl lysine vasopressin

12 residues · 1227 Da · 85 atoms

Lypressin with three glycines added to the front. Those glycines are cleaved off slowly in the body, so the molecule acts as its own slow release. The ring sits at the far end from them.

Reference entry · not stocked

Thyrotropin releasing hormone

3 residues · 362 Da · 48 atoms

Three residues, and the smallest peptide hormone known. It opens with a pyroglutamate ring and closes with an amide, both drawn, so almost none of this molecule is an ordinary chain. Cyclo-His-Pro, which is what is left when this breaks down, is also in the library.

Reference entry · not stocked

Triptorelin

Gonadorelin with D-tryptophan at six

10 residues · 1311 Da · 95 atoms

Gonadorelin with a single substitution: the glycine at position six becomes D-tryptophan, whose side chain is mirrored here. One residue is the entire difference, and it is why the analogue lasts far longer than the natural hormone.

Reference entry · not stocked

Urocortin

40 residues · 4696 Da · 331 atoms

Forty residues sharing sauvagine's architecture: a short structured front end followed by a long helix. The two are worth reading side by side.

Reference entry · not stocked

Urocortin III

38 residues · 4138 Da · 290 atoms

Thirty-eight residues sharing the family helix while overlapping the original urocortin at fewer than half its positions. Both are here.

Reference entry · not stocked

Urotensin II

11 residues · 1389 Da · 97 atoms

Eleven residues with cysteines at five and ten joined by a disulfide, closing a six-residue ring with short tails at either end.

Reference entry · not stocked

Vasopressin

9 residues · 1084 Da · 75 atoms

The same ring-and-tail architecture as oxytocin, differing at two positions: phenylalanine for isoleucine at three, and arginine for leucine at eight. Comparing the two side by side is the clearest illustration in this library of how little has to change.

Reference entry · not stocked

Xenopsin

8 residues · 980 Da · 145 atoms

Eight residues opening with a pyroglutamate ring. Structurally related to neurotensin, which is also here, sharing its hydrophobic tail.

Reference entry · not stocked