If you have been reading about cyclic heptapeptide and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2026-02-01. Where a claim depends on a specific study, the study is described rather than over-claimed.
Melanotan-2 is handled in the laboratory as a lyophilised powder that dissolves readily in water, dimethyl sulfoxide and dimethylformamide, with limited solubility in ethanol. Stock solutions prepared in an organic solvent often precipitate when diluted into aqueous buffer, so gradual dilution with mixing is standard practice. The peptide carries a tryptophan residue and a histidine residue, both sensitive to oxidation and to alkaline conditions. Working solutions are therefore kept near neutral to slightly acidic pH, protected from light, and consumed within the same working session whenever that is practical.
Solid peptide kept dry at minus twenty degrees Celsius, shielded from light and moisture, is generally considered stable for extended periods. Solutions are divided into single-use aliquots and held at minus twenty or minus eighty degrees Celsius, because repeated freeze-thaw cycles promote aggregation and loss of material to container surfaces. Hydrolysis of the backbone and oxidation of tryptophan are the principal degradation routes in aqueous solution, and both accelerate at ambient temperature. Hygroscopic uptake after a vial is opened can also shift the actual mass weighed, which affects any concentration calculated from it.
Routine characterisation relies on reversed-phase high-performance liquid chromatography with ultraviolet detection near 214 nanometres, using a C18 column and a water-acetonitrile gradient containing trifluoroacetic acid. Electrospray ionisation mass spectrometry confirms the expected molecular mass and can reveal truncated or oxidised by-products that co-elute poorly. Sequence and stereochemistry require additional work, such as peptide mapping or amino acid analysis, because a chromatographic purity figure alone does not distinguish a diastereomer from the target peptide. Independent testing of research-grade material frequently shows measured content below the stated label, so a certificate of analysis is best read together with the method that produced it.
Melanocytes are the pigment-producing cells of the skin, and they carry melanocortin-1 receptors on their surface. When the receptor is activated, cyclic adenosine monophosphate rises inside the cell and raises the activity of enzymes such as tyrosinase, which increases melanin output. Melanotan-2 binds melanocortin-1 receptors in vitro and in animal models, and this binding is generally described as the basis for the tanning effect. Other receptors account for different effects: melanocortin-4 receptors contribute to appetite and erectile signalling, while melanocortin-3 and melanocortin-5 receptors contribute to energy balance and exocrine function.
Early published reports described melanotan-2 as a tanning agent without sun protection, which means darkening is not the same as protection against ultraviolet radiation. Later studies explored the peptide in erectile dysfunction, hemorrhagic shock, and some skin conditions. No regulator in the United States or Europe has approved it for clinical use. Many products labelled melanotan-2 are sold without approval and their identity and purity are unverified. Its long-term safety in humans remains an open question.
Melanotan-2, also written Melanotan II, is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone. Its sequence is Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, and the lactam bridge between the aspartate and lysine side chains constrains the peptide into a ring. This structural change increases receptor affinity and metabolic stability relative to the native hormone. The compound was created in the 1980s as a research tool for studying pigmentation biology.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Lyophilised material may be hygroscopic |
| Solubility class | Soluble in water, DMSO and DMF | Dilution into aqueous buffer can cause precipitation |
| Storage of solid | Minus 20 degrees C, desiccated, dark | Aliquot to limit repeated opening of the vial |
| Storage of solution | Minus 20 to minus 80 degrees C, aliquoted | Avoid repeated freeze-thaw cycles |
| Identity method | Reversed-phase HPLC with mass spectrometry | Retention time and mass are checked together |
The material is commonly handled as a lyophilized powder in sealed vials. The solid dissolves readily in water and in polar organic solvents, producing a clear solution after reconstitution. Light, heat and repeated freeze-thaw cycles are the concerns most often raised in handling guidance, because peptide bonds and the constrained ring can degrade. Working solutions are generally prepared fresh, and material left in solution is treated as less stable than the dry form. These properties shape how laboratories store and aliquot reference material.
Identity and purity are assessed mainly by reversed-phase high-performance liquid chromatography with ultraviolet detection, often paired with mass spectrometry. Retention time supports identity, while the mass spectrum confirms the molecular weight of the intact peptide. Purity is frequently reported as a percentage of total peak area, a figure that depends on the wavelength, column and gradient used. Impurity profiling may also look for truncated sequences, oxidised forms and residual counterions. Amino acid analysis and peptide mapping provide orthogonal confirmation when required.
Regulatory status varies by jurisdiction, and the substance is frequently described as unapproved for therapeutic use. Some authorities classify it alongside prescription-only medicines or controlled categories, while others address it through general consumer protection rules. Analytical surveys have reported mismatches between label claims and measured content in products sold online, although the scope of such testing is limited. Whether these discrepancies are widespread remains an open question. Discussion in the literature therefore tends to combine chemistry, supply-chain observation and policy analysis.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone. Its sequence incorporates a lactam bridge that constrains the peptide into a ring, which increases resistance to enzymatic breakdown relative to the natural hormone. Researchers at the University of Arizona synthesised the compound in the late 1980s and early 1990s while studying pigmentation pathways. It has never received marketing approval from any national medicines regulator. In the scientific literature it is usually described as a laboratory research reagent rather than a therapeutic product.
The peptide acts as a non-selective agonist at melanocortin receptors, showing affinity for MC1R, MC3R, MC4R and MC5R. Activation of MC1R on melanocytes drives the conversion of tyrosine into melanin and shifts production toward the darker eumelanin form. MC4R signalling in the central nervous system is linked to appetite and energy balance, which helps explain why reduced food intake appeared in early human studies. Effects on MC4R and on vascular tone also account for the erectile responses recorded as unexpected findings in those same trials.
Melanotan-2 is frequently confused with afamelanotide, a linear analogue authorised in the European Union for erythropoietic protoporphyria. The two compounds differ in chain length, ring structure and receptor selectivity, so findings for one cannot be transferred directly to the other. Published controlled human data on melanotan-2 remain sparse, and much of what circulates online derives from small studies or unpublished reports. Questions about effect size, dose-response behaviour and long-term safety therefore remain unresolved.
. This is consistent with a normal kinetic isotope effect in which the product is slightly depleted in a heavy isotope relative to the reactant. If the isotope effect is small, as is typical for C and N,
In chemical structure, ketamine is an arylcyclohexylamine derivative. Ketamine is a chiral compound. The more active enantiomer, esketamine (S-ketamine), is also available for medical use under the brand name Ketanest S, while the less active enantiomer, arketamine (R-ketamine), has never been marketed as an enantiopure drug for clinical use. While S-ketamine is more effective as an analgesic and anesthetic through NMDA receptor antagonism, R-ketamine produces longer-lasting effects as an antidepressant. The optical rotation of a given enantiomer of ketamine can vary between its salts and free base form. The free base form of (S)‑ketamine exhibits dextrorotation and is therefore labelled (S)‑(+)‑ketamine. However, its hydrochloride salt shows levorotation and is thus labelled (S)‑(−)‑ketamine hydrochloride.
Calcitriol exerts its effects primarily by binding to the vitamin D receptor (VDR), which leads to the upregulation of gene transcription. In the absence of calcitriol, the VDR is mainly located in the cytoplasm of cells. Calcitriol enters cells and binds to the VDR which forms a complex with its coreceptor RXR and the activated VDR/RXR complex is translocated into the nucleus. The VDR/RXR complex subsequently binds to vitamin D response elements (VDRE) which are specific DNA sequences adjacent to genes, numbers estimated as being in the thousands. The VDR/RXR/DNA complex recruits other proteins that transcribe the downstream gene into mRNA which in turn is translated into protein causing a change in cell function. In addition to calcitriol, other vitamin D metabolites may contribute to vitamin D's biological effects. For example, CYP11A1, an enzyme chiefly known for its role in steroidogenesis, has been found to hydroxylate vitamin D3 at several positions, including C-20, C-22, and C-23, without cleaving the side chain. The resulting metabolites, such as 20-hydroxyvitamin D3 and 20,23-dihydroxyvitamin D3, act as inverse agonists for RORα and RORγ2. This interaction leads to effects such as the downregulation of IL-17 signaling, which influences the immune system. Finally, some effects of vitamin D occur too rapidly to be explained by its influence on gene transcription. For example, calcitriol triggers rapid calcium uptake (within 1–10 minutes) in a variety of cells. These non-genomic actions may involve membrane-bound receptors like PDIA3.
=== Myeloid cells === The effects of TGF-β1 on macrophages and monocytes are predominantly suppressive; this cytokine can inhibit the proliferation of these cells and prevent their production of reactive oxygen (e.g. superoxide (O2−)) and nitrogen (e.g. nitric oxide (NO)) intermediates. However, as with other cell types, TGF-β1 can also have the opposite effect on cells of myeloid origin. For example, TGF-β1 acts as a chemoattractant, directing an immune response to certain pathogens. Likewise, macrophages and monocytes respond to low levels of TGF-β1 in a chemotactic manner. Furthermore, the expression of monocytic cytokines (such as interleukin(IL)-1α, IL-1β, and TNF-α), and macrophage's phagocytic can be increased by the action of TGF-β1. TGF-β1 reduces the efficacy of the MHC II in astrocytes and dendritic cells, which in turn decreases the activation of appropriate helper T cell populations.
Sources: en.wikipedia.org
==== Other potential disadvantages ==== Processed foods may actually take less energy to digest than whole foods, according to a study published in "Food & Nutrition Research" in 2010, meaning more of their food energy content is retained within the body. Processed foods also tend to be more allergenic than whole foods, according to a June 2004 "Current Opinion in Allergy and Clinical Immunology" article. Although the preservatives and other food additives used in many processed foods are generally recognized as safe, a few may cause problems for some individuals, including sulfites, artificial sweeteners, artificial colors and flavors, sodium nitrate, BHA and BHT, olestra, caffeine and monosodium glutamate — a flavor enhancer.
===== MeSH D08.811.277.352 – esterases (EC 3.1) ===== MeSH D08.811.277.352.100 – carboxylic-ester hydrolases MeSH D08.811.277.352.100.050 – acetylesterase MeSH D08.811.277.352.100.100 – carboxylesterase MeSH D08.811.277.352.100.150 – cholesterol esterase MeSH D08.811.277.352.100.170 – cholinesterases MeSH D08.811.277.352.100.170.176 – acetylcholinesterase MeSH D08.811.277.352.100.170.250 – butyrylcholinesterase MeSH D08.811.277.352.100.170.710 – pseudocholinesterase MeSH D08.811.277.352.100.220 – dehydroascorbatase MeSH D08.811.277.352.100.400 – lipase MeSH D08.811.277.352.100.400.745 – pancrelipase MeSH D08.811.277.352.100.430 – lipoprotein lipase MeSH D08.811.277.352.100.500 – monoacylglycerol lipases MeSH D08.811.277.352.100.550 – naphthol as d esterase MeSH D08.811.277.352.100.680 – phospholipases MeSH D08.811.277.352.100.680.510 – lysophospholipase MeSH D08.811.277.352.100.680.750 – phospholipases a MeSH D08.811.277.352.100.680.750.500 – 1-alkyl-2-acetylglycerophosphocholine esterase MeSH D08.811.277.352.335 – deoxyribonucleases MeSH D08.811.277.352.335.350 – endodeoxyribonucleases MeSH D08.811.277.352.335.350.025 – aspergillus nuclease s1 MeSH D08.811.277.352.335.350.137 – deoxyribonuclease (pyrimidine dimer) MeSH D08.811.277.352.335.350.250 – deoxyribonuclease i MeSH D08.811.277.352.335.350.250.900 – streptodornase and streptokinase MeSH D08.811.277.352.335.350.275 – deoxyribonuclease iv (phage t4-induced) MeSH D08.811.277.352.335.350.300 – dna restriction enzymes MeSH D08.811.277.352.335.350.300.250 – deoxyribonucleases, type i site-specific MeSH D08.811.277.352.335.350.300.260 – deoxyribonucleases, type ii site-specific MeSH D08.811.277.352.335.350.300.260.240 – deoxyribonuclease bamhi MeSH D08.811.277.352.335.350.300.260.250 – deoxyribonuclease ecori MeSH D08.811.277.352.335.350.300.260.260 – deoxyribonuclease hindiii MeSH D08.811.277.352.335.350.300.260.300 – deoxyribonuclease hpaii MeSH D08.811.277.352.335.350.300.270 – deoxyribonucleases, type iii site-specific MeSH D08.811.277.352.335.350.400 – holliday junction resolvases MeSH D08.811.277.352.335.350.500 – micrococcal nuclease MeSH D08.811.277.352.335.375 – exodeoxyribonucleases MeSH D08.811.277.352.335.375.750 – exodeoxyribonuclease V MeSH D08.811.277.352.355 – endonucleases MeSH D08.811.277.352.355.325 – endodeoxyribonucleases MeSH D08.811.277.352.355.325.025 – aspergillus nuclease s1 MeSH D08.811.277.352.355.325.300 – dna restriction enzymes MeSH D08.811.277.352.355.325.300.250 – deoxyribonucleases, type i site-specific MeSH D08.811.277.352.355.325.300.260 – deoxyribonucleases, type ii site-specific MeSH D08.811.277.352.355.325.300.260.240 – deoxyribonuclease bamhi MeSH D08.811.277.352.355.325.300.260.250 – deoxyribonuclease ecori MeSH D08.811.277.352.355.325.300.260.260 – deoxyribonuclease hindiii MeSH D08.811.277.352.355.325.300.260.300 – deoxyribonuclease hpaii MeSH D08.811.277.352.355.325.300.270 – deoxyribonucleases, type iii site-specific MeSH D08.811.277.352.355.325.350 – flap endonucleases MeSH D08.811.277.352.355.325.400 – holliday junction resolvases MeSH D08.811.277.352.355.325.500 – micrococcal nuclease MeSH D08.811.277.352.355.350 – endoribonucleases MeSH D08.811.277.352.355.350.025 – aspergillus nuclease s1 MeSH D08.811.277.352.355.350.500 – micrococcal nuclease MeSH D08.811.277.352.355.350.700 – ribonuclease h, calf thymus MeSH D08.811.277.352.355.350.715 – ribonuclease, pancreatic MeSH D08.811.277.352.355.350.725 – ribonuclease t1 MeSH D08.811.277.352.355.350.810 – RNA-induced silencing complex MeSH D08.811.277.352.365 – exonucleases MeSH D08.811.277.352.365.290 – exodeoxyribonucleases MeSH D08.811.277.352.365.300 – exoribonucleases MeSH D08.811.277.352.640 – phosphoric diester hydrolases MeSH D08.811.277.352.640.050 – annexin A3 MeSH D08.811.277.352.640.125 – 3',5'-cyclic-GMP phosphodiesterase MeSH D08.811.277.352.640.150 – 3',5'-cyclic-nucleotide phosphodiesterase MeSH D08.811.277.352.640.160 – 2',3'-cyclic-nucleotide phosphodiesterases MeSH D08.811.277.352.640.295 – glycerophosphoinositol inositolphosphodiesterase MeSH D08.811.277.352.640.430 – phosphodiesterase i MeSH D08.811.277.352.640.700 – phospholipases MeSH D08.811.277.352.640.700.700 – phospholipase c MeSH D08.811.277.352.640.700.700.500 – phosphatidylinositol diacylglycerol-lyase MeSH D08.811.277.352.640.700.700.750 – phospholipase c gamma MeSH D08.811.277.352.640.700.710 – phospholipase d MeSH D08.811.277.352.640.750 – sphingomyelin phosphodiesterase MeSH D08.811.277.352.650 – phosphoric monoester hydrolases MeSH D08.811.277.352.650.025 – acid phosphatase MeSH D08.811.277.352.650.035 – alkaline phosphatase MeSH D08.811.277.352.650.200 – fructose-bisphosphatase MeSH D08.811.277.352.650.225 – glucose-6-phosphatase MeSH D08.811.277.352.650.300 – histidinol-phosphatase MeSH D08.811.277.352.650.575 – 4-nitrophenylphosphatase MeSH D08.811.277.352.650.600 – nucleotidases MeSH D08.811.277.352.650.600.600 – 5'-nucleotidase MeSH D08.811.277.352.650.620 – phosphatidate phosphatase MeSH D08.811.277.352.650.622 – phosphofructokinase-2 MeSH D08.811.277.352.650.625 – phosphoprotein phosphatase MeSH D08.811.277.352.650.625.150 – calcineurin MeSH D08.811.277.352.650.625.300 – glycogen-synthase-d phosphatase MeSH D08.811.277.352.650.625.475 – myosin light-chain phosphatase MeSH D08.811.277.352.650.625.650 – phosphorylase phosphatase MeSH D08.811.277.352.650.625.700 – protein-tyrosine-phosphatase MeSH D08.811.277.352.650.625.700.150 – antigens, cd45 MeSH D08.811.277.352.650.625.700.200 – cdc25 phosphatase MeSH D08.811.277.352.650.625.725 – pyruvate dehydrogenase (lipoamide)-phosphatase MeSH D08.811.277.352.650.700 – 6-phytase MeSH D08.811.277.352.650.850 – pten phosphohydrolase MeSH D08.811.277.352.660 – phosphoric triester hydrolases MeSH D08.811.277.352.660.500 – aryldialkylphosphatase MeSH D08.811.277.352.700 – ribonucleases MeSH D08.811.277.352.700.350 – endoribonucleases MeSH D08.811.277.352.700.350.025 – aspergillus nuclease s1 MeSH D08.811.277.352.700.350.262 – eosinophil cationic protein MeSH D08.811.277.352.700.350.381 – eosinophil-derived neurotoxin MeSH D08.811.277.352.700.350.500 – micrococcal nuclease MeSH D08.811.277.352.700.350.700 – ribonuclease h, calf thymus MeSH D08.811.277.352.700.350.707 – ribonuclease iii MeSH D08.811.277.352.700.350.711 – ribonuclease p MeSH D08.811.277.352.700.350.715 – ribonuclease, pancreatic MeSH D08.811.277.352.700.350.725 – ribonuclease t1 MeSH D08.811.277.352.700.350.810 – RNA-induced silencing complex MeSH D08.811.277.352.700.375 – exoribonucleases MeSH D08.811.277.352.827 – sulfatases MeSH D08.811.277.352.827.070 – arylsulfatases MeSH D08.811.277.352.827.070.060 – n-acetylgalactosamine-4-sulfatase MeSH D08.811.277.352.827.070.250 – cerebroside-sulfatase MeSH D08.811.277.352.827.070.625 – steryl-sulfatase MeSH D08.811.277.352.827.180 – chondroitinases and chondroitin lyases MeSH D08.811.277.352.827.180.175 – chondroitinsulfatases MeSH D08.811.277.352.827.180.175.060 – n-acetylgalactosamine-4-sulfatase MeSH D08.811.277.352.827.180.175.275 – chondro-4-sulfatase MeSH D08.811.277.352.827.500 – iduronate sulfatase MeSH D08.811.277.352.897 – thiolester hydrolases MeSH D08.811.277.352.897.075 – acetyl-CoA hydrolase MeSH D08.811.277.352.897.700 – palmitoyl-coa hydrolase MeSH D08.811.277.352.897.850 – ubiquitin thiolesterase
== Function == The protein encoded by this gene is the predominant constituent of the crystalline core of the eosinophil granule. High levels of the proform of this protein are also present in placenta and pregnancy serum, where it exists as a complex with several other proteins including pregnancy-associated plasma protein A (PAPPA), angiotensinogen (AGT), and C3dg. This protein may be involved in antiparasitic defense mechanisms as a cytotoxin and helmintho-toxin, and in immune hypersensitivity reactions. It is directly implicated in epithelial cell damage, exfoliation, and bronchospasm in allergic diseases. PRG2 is a 117-residue protein that predominates in eosinophil granules. It is a potent enzyme against helminths and is toxic towards bacteria and mammalian cells in vitro. The eosinophil major basic protein also causes the release of histamine from mast cells and basophils, and activates neutrophils and alveolar macrophages.
Sources: en.wikipedia.org
==== Deep vein thrombosis ==== DVT usually occurs in the veins of the legs, although it can also occur in the deep veins of the arms. Immobility, active cancer, obesity, traumatic damage and congenital disorders that make clots more likely are all risk factors for deep vein thrombosis. It can cause the affected limb to swell, and cause pain and an overlying skin rash. In the worst case, a deep vein thrombosis can extend, or a part of a clot can break off as an embolus and lodge in a pulmonary artery in the lungs, known as a pulmonary embolism. The decision to treat deep vein thrombosis depends on its size, symptoms, and their risk factors. It generally involves anticoagulation to prevents clots or to reduce the size of the clot. Intermittent pneumatic compression is a method used to improve venous circulation in cases of edema or in those at risk from a deep vein thrombosis.
Overtraining occurs when a bodybuilder has trained to the point where their workload exceeds their recovery capacity. There are many reasons why overtraining occurs, including lack of adequate nutrition, lack of recovery time between workouts, insufficient sleep, and training at a high intensity for too long (a lack of splitting apart workouts). Training at a high intensity too frequently also stimulates the central nervous system (CNS) and can result in a hyperadrenergic state that interferes with sleep patterns. To avoid overtraining, intense frequent training must be met with at least an equal amount of purposeful recovery. Timely provision of carbohydrates, proteins, and various micronutrients such as vitamins, minerals, phytochemicals, even nutritional supplements are critical. A mental disorder, informally called bigorexia (by analogy with anorexia), may account for overtraining in some individuals. Sufferers feel as if they are never big enough or muscular enough, which forces them to overtrain to try to reach their goal physique. An article by Muscle & Fitness magazine, "Overtrain for Big Gains", claimed that overtraining for a brief period can be beneficial. Overtraining can be used advantageously, as when a bodybuilder is purposely overtrained for a brief period of time to super compensate during a regeneration phase. These are known as "shock micro-cycles" and were a key training technique used by Soviet athletes.
Although they lacked the managerial acumen and cultural cachet of the Grateful Dead and elected to remain in East Palo Alto, California, unlike the former group, which soon relocated to the Haight-Ashbury district of San Francisco, the New Delhi River Band were considered by late 1966 to be the house band of The Barn (one of the region's few viable concert venues outside of San Francisco) in Scotts Valley, California. The group continued to enjoy a cult following in Santa Clara and Santa Cruz Counties through the Summer of Love until their dissolution in early 1968. After a period of inactivity Nelson contributed to the Grateful Dead's Aoxomoxoa (1969) sessions and served as the caretaker of Big Brother and the Holding Company's rehearsal space while guitarist Peter Albin and drummer David Getz undertook a European tour with Country Joe & the Fish following the schismatic departure of Janis Joplin and Sam Andrew from the former band in December 1968. During this period Nelson and Garcia played intermittently in an early iteration of High Country, a traditional bluegrass ensemble formed by the remnants of the Peninsula folk scene. Nelson was set to serve as lead guitarist in the reconstituted lineup of Big Brother that coalesced later in 1969 and thus may have contributed to some of the recordings on Be a Brother (1970) during this transitional period.
Sources: en.wikipedia.org
Purity is normally stated as an area percentage from high-performance liquid chromatography, for example ninety-five or ninety-eight percent. That figure describes the proportion of ultraviolet-absorbing material eluting as the main peak. It says nothing about water content, counterions, residual solvents or mass fraction of the peptide itself.
Peptides are commonly isolated as acetate or trifluoroacetate salts, and the counterion contributes to total mass. Two vials with identical peptide content can therefore differ in weight and in measured response. Residual trifluoroacetate is also relevant in cell-based work because it can influence membrane behaviour.
Degradation products are often closely related to the parent molecule, making them hard to resolve with a single method. Counterion variability adds a further source of scatter between laboratories. Because no pharmacopoeial monograph exists for melanotan-2, groups rely on method-specific validation rather than a shared reference standard.
No. It is a laboratory-made peptide, while the natural hormone is alpha-melanocyte-stimulating hormone, a longer peptide produced by the pituitary gland and by skin cells. Melanotan-2 mimics only a short active region of that hormone and contains non-natural residues such as D-phenylalanine.