If you have been reading about reverse-phase HPLC 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 2026-04-30. Where a claim depends on a specific study, the study is described rather than over-claimed.
Identity and purity are established with orthogonal methods rather than a single test. Reverse-phase high-performance liquid chromatography with ultraviolet detection gives a purity figure by area normalization, while mass spectrometry confirms the expected molecular ion. Amino acid analysis or peptide mapping can detect sequence errors that a mass value alone would miss, and residual counterion content is sometimes measured separately. Common impurities include truncated sequences, oxidized residues, and deamidated products; reporting them individually is more informative than a single composite purity number.
Lyophilized peptide arrives as a white to off-white cake or powder and is normally held at minus twenty degrees Celsius or colder for extended periods. Short-term bench work at ambient temperature is tolerable for minutes, not hours, because the solid is hygroscopic and picks up moisture that promotes hydrolysis. Vials should stay in a desiccator or a sealed bag with desiccant, protected from light, since aromatic residues in the sequence are susceptible to photo-oxidation. Inventory records that note arrival date and storage location reduce the chance of using degraded material.
Reconstitution is usually performed with sterile water or a dilute acetic acid solution, and the choice of solvent affects both dissolution speed and final pH. Complete dissolution should be confirmed by visual inspection before any aliquot is taken, since undissolved particles can concentrate in the sampling volume. Repeated freeze-thaw cycles are the most common cause of gradual loss of purity, so dividing a stock into single-use aliquots at the first opportunity is standard practice. Working solutions kept refrigerated are generally used within days rather than weeks.
Early clinical work used an intranasal formulation, and later programmes switched to subcutaneous delivery for more consistent absorption. A subcutaneous product received regulatory approval in the United States in 2019 for premenopausal women with acquired, generalised hypoactive sexual desire disorder. Approval followed phase 3 trials in which active treatment separated from placebo on desire and distress measures, though the average difference was modest. Labeling carries a caution about transient blood pressure elevation, so cardiovascular history is assessed before prescribing. Questions about durability of benefit beyond several months remain open.
Published discussion sits at the intersection of peptide chemistry, neuroendocrinology and sexual medicine. Trial reports emphasise change scores on validated instruments, while mechanistic papers focus on hypothalamic circuits and receptor selectivity. Because placebo response in this field is large, effect sizes are usually reported with confidence intervals rather than as isolated averages. Reviews note that female and male data sets are not interchangeable and should be read separately. Diagnostic terminology has been revised over time, which complicates comparison between older and newer studies.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Lyophilized form |
| Solubility class | Soluble in water and DMSO | Dissolves readily |
| Typical storage temperature | -20 °C or lower | Long-term, desiccated |
| Standard purity method | Reverse-phase HPLC | Area normalization |
| Freeze-thaw guidance | Limit to three cycles | Aliquot in advance |
PT-141 is the research code for bremelanotide, a cyclic heptapeptide derived from alpha-melanocyte-stimulating hormone. The molecule belongs to the melanocortin receptor agonist family and shows highest affinity for the MC4 receptor subtype, with weaker activity at MC1, MC3 and MC5. Its structure retains the core His-Phe-Arg-Trp sequence that defines melanocortin recognition, while cyclization and terminal modifications improve metabolic stability relative to the parent hormone. Early work classified the compound as a centrally acting agent rather than a peripherally acting vasodilator, which shaped subsequent development priorities.
Receptor activation in hypothalamic and limbic circuits is the mechanism most often cited for the observed effects on sexual desire. Signalling through MC4R couples to Gs proteins and raises intracellular cyclic AMP, which in turn modulates dopaminergic tone in reward-related pathways. Because the peptide reaches the central nervous system after subcutaneous administration, peripheral vascular changes are regarded as secondary rather than primary. The precise neural circuits that translate receptor occupancy into behavioural change remain incompletely mapped, and published accounts describe the pathway in general terms rather than as a fully resolved sequence.
Bremelanotide is a synthetic cyclic heptapeptide developed as an analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation and appetite signalling. Its structure contains seven amino acid residues joined by a lactam bridge that closes the ring between two side chains. The molecular formula is C50H68N14O10 and the nominal molecular mass is near 1025 daltons. Much of the early laboratory literature refers to the same molecule by the development code PT-141.
The compound emerged from a research programme examining melanocortin analogues for effects on skin pigmentation. During early human studies, participants reported spontaneous erections as an unexpected side effect, which redirected development toward sexual function rather than tanning. An intranasal formulation was investigated in clinical trials but did not reach market approval. A subcutaneous injectable version later completed the regulatory process, and the nasal route does not appear in approved labelling.
Approved use is narrow and jurisdiction-specific. In the United States, the injectable product is authorised for premenopausal women with acquired, generalised hypoactive sexual desire disorder, a diagnosis that requires documented distress. It is not approved for men, for postmenopausal women, or for use alongside hormonal contraceptives under the approved labelling. Outside regulated markets, the same peptide is frequently sold as a research chemical, where identity, purity, and sterility are not independently verified.
An artificial organ is an engineered device that can be extra corporeal or implanted to support impaired or failing organ systems. Bioartificial organs are typically created with the intent to restore critical biological functions like in the replacement of diseased hearts and lungs, or provide drastic quality of life improvements like in the use of engineered skin on burn victims. While some examples of bioartificial organs are still in the research stage of development due to the limitations involved with creating functional organs, others are currently being used in clinical settings experimentally and commercially.
=== Laboratory applications === Other applications include phosphorothioate-based ligase-independent cloning, sequence saturation mutagenesis, no-SCAR genome editing, nucleotide analog interference mapping, and incremental truncation for the creation of hybrid enzymes, and antibody-oligonucleotide conjugates.
Calendula arvensis (Vaill.) L. – field marigold, wild marigold Calendula denticulata Schousb. ex Willd. Calendula eckerleinii Ohle Calendula incana Willd. Calendula incana subsp. algarbiensis (Boiss.) Ohle Calendula incana subsp. maderensis (DC.) Ohle – Madeiran marigold Calendula incana subsp. maritima (Guss.) Ohle – sea marigold Calendula incana subsp. microphylla (Lange) Ohle Calendula lanzae Maire Calendula maritima Guss. - sea marigold Calendula maroccana (Ball) Ball Calendula maroccana subsp. maroccana Calendula maroccana subsp. murbeckii (Lanza) Ohle Calendula meuselii Ohle Calendula officinalis L. – pot marigold, garden marigold, ruddles, Scottish marigold Calendula palaestina Boiss. Calendula stellata Cav. Calendula suffruticosa Vahl Calendula suffruticosa subsp. balansae (Boiss. & Reut.) Ohle Calendula suffruticosa subsp. boissieri Lanza Calendula suffruticosa subsp. fulgida (Raf.) Guadagno Calendula suffruticosa subsp. lusitanica (Boiss.) Ohle Calendula suffruticosa subsp. maritima (Guss.) Meikle Calendula suffruticosa subsp. monardii (Boiss. & Reut.) Ohle Calendula suffruticosa subsp. tomentosa Murb. Calendula tripterocarpa Rupr.
Grain and beans are stored in tall grain elevators, almost always at a railhead near the point of production. The grain is shipped to a final user in hopper cars. In the former Soviet Union grain was sometimes irradiated. In the U.S., threshing and drying are performed in the field, and transport is nearly sterile and in large containers that effectively suppress pest access, eliminating the need for irradiation. Fresh fruits and vegetables are sometimes packed in plastic packaging and cups for premium fresh markets, or placed in large plastic tubs for sauce and soup processors. Fruits and vegetables are usually refrigerated at the earliest possible moment, and even so have a shelf life of two weeks or less. In the United States, livestock is usually transported live, slaughtered at a major distribution point, hung, and transported for two days to a week in refrigerator cars before being butchered and sold locally. Before refrigerated rail cars, meat had to be transported live, which made it so expensive that only farmers and the wealthy could afford it every day. In Europe, much meat is transported live and slaughtered close to the point of sale. In much of Africa and Asia, most meat for local populations is raised, slaughtered, and eaten locally, which is believed to be less stressful for the animals involved and minimizes meat storage needs. In Australia and New Zealand, where a large proportion of meat production is for export, meat enters the cold chain early, being stored in large freezer plants before being shipped overseas in freezer ships.
Sources: en.wikipedia.org
=== Legal status in the United States === The US government imposed tougher prescribing rules for hydrocodone in 2014, changing the drug from Schedule III to Schedule II. In 2011, hydrocodone products were involved in around 100,000 abuse-related emergency department visits in the United States, more than double the number in 2004.
In rational protein design, proteins can be redesigned from the sequence and structure of a known protein, or completely from scratch in de novo protein design. In protein redesign, most of the residues in the sequence are maintained as their wild-type amino-acid while a few are allowed to mutate. In de novo design, the entire sequence is designed anew, based on no prior sequence. Both de novo designs and protein redesigns can establish rules on the sequence space: the specific amino acids that are allowed at each mutable residue position. For example, the composition of the surface of the RSC3 probe to select HIV-broadly neutralizing antibodies was restricted based on evolutionary data and charge balancing. Many of the earliest attempts on protein design were heavily based on empiric rules on the sequence space. Moreover, the design of fibrous proteins usually follows strict rules on the sequence space. Collagen-based designed proteins, for example, are often composed of Gly-Pro-X repeating patterns. The advent of computational techniques allows designing proteins with no human intervention in sequence selection.
=== Generic names === Clomipramine is the English and French generic name of the drug and its INNTooltip International Nonproprietary Name, BANTooltip British Approved Name, and DCFTooltip Dénomination Commune Française, while clomipramine hydrochloride is its USANTooltip United States Adopted Name, USPTooltip United States Pharmacopeia, BANMTooltip British Approved Name, and JANTooltip Japanese Accepted Name. Clomipramina is its generic name in Spanish, Portuguese and Italian and its DCITTooltip Denominazione Comune Italiana, while clomipramin is its generic name in German and clomipraminum is its generic name in Latin.
Sources: en.wikipedia.org
== External links == Ciliary+neurotrophic+factor at the U.S. National Library of Medicine Medical Subject Headings (MeSH) Overview of all the structural information available in the PDB for UniProt: P26441 (Ciliary neurotrophic factor) at the PDBe-KB.
== Regulation == SHBG has both enhancing and inhibiting hormonal influences and thus can be viewed as a hepatokine. It decreases with high levels of insulin, growth hormone, insulin-like growth factor 1 (IGF-1), androgens, prolactin and transcortin. High estrogen and thyroxine levels cause it to increase. In an effort to explain obesity-related reductions in SHBG, recent evidence suggests sugar or monosaccharide-induced hepatic lipogenesis, hepatic lipids in general, and cytokines like TNF-alpha and interleukins reduce SHBG, whereas insulin does not. For example, anti-psoriatic drugs that inhibit TNF-alpha cause an increase in SHBG. The common downstream mechanism for all of these, including the effect of thyroid hormones, was downregulation of hepatocyte nuclear factor 4 (HNF4).
The full-length human protein comprises 2,843 amino acids with a (predicted) molecular mass of 311646 Da. Several N-terminal domains have been structurally elucidated in unique atomistic high-resolution complex structures. Most of the protein is predicted to be intrinsically disordered. It is not known if this large predicted unstructured region from amino acid 800 to 2843 persists in vivo or would form stabilised complexes – possibly with yet unidentified interacting proteins. Recently, it has been experimentally confirmed that the mutation cluster region around the center of APC is intrinsically disordered in vitro.
Sources: en.wikipedia.org
Cold storage at minus twenty degrees Celsius or below is typical, with desiccant and protection from light. The solid form is far more stable than any solution.
Repeated freeze-thaw cycles, alkaline pH, and exposure to light or oxygen are the main drivers. Moisture uptake by the solid also matters.
Mass spectrometry provides the strongest single identity check by matching the observed molecular ion to the expected value. Chromatographic retention time alone is not sufficient.
It is a synthetic cyclic peptide that activates melanocortin receptors. It is given by injection and was approved in the United States in 2019 for a specific low-desire diagnosis in premenopausal women. It is not a hormonal therapy.