If you have been reading about mass spectrometry 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 2025-11-14. Where a claim depends on a specific study, the study is described rather than over-claimed.
Lyophilised material kept dry at minus 20 degrees Celsius or colder is the most stable form, and suppliers commonly state a shelf life of two years or more under those conditions. Once dissolved, degradation accelerates through hydrolysis and deamidation, particularly at alkaline pH or elevated temperature. Working solutions are usually divided into single-use aliquots to avoid repeated freeze-thaw cycles. The choice of reconstitution solvent affects both stability and the ionic strength of the final preparation.
Reverse-phase high-performance liquid chromatography with ultraviolet detection near 214 nanometres is the standard purity method. Mass spectrometry, typically electrospray ionisation, confirms identity through the expected mass-to-charge pattern. Amino acid analysis can verify composition independently. Chiral purity requires separate techniques such as derivatisation followed by chromatographic separation, and such data are rarely reported for research-grade material.
Quantification in biological matrices relies on liquid chromatography coupled to tandem mass spectrometry with stable-isotope internal standards. Low plasma concentrations and adsorption to container surfaces both complicate measurement. Solid-phase extraction is often needed to reduce matrix interference before injection. Reported limits of quantification differ widely between laboratories, which makes direct comparison of pharmacokinetic results difficult and limits meta-analysis.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. Its four N-terminal residues reproduce tuftsin, a tetrapeptide fragment of the immunoglobulin heavy chain, while the C-terminal Pro-Gly-Pro extension is a synthetic addition. The peptide has a molecular mass near 752 daltons and carries a net positive charge at physiological pH because of the arginine and lysine side chains. Published indexes list it under the name Selank and the sequence abbreviation TKPRPGP. Solid-phase peptide synthesis is the standard production route for research quantities.
Development took place at the Institute of Molecular Genetics of the Russian Academy of Sciences, where a series of short peptides were designed in the 1980s and 1990s. Selank was selected from variants of tuftsin that showed resistance to plasma peptidases. Russian regulatory approval covers it as an anxiolytic agent given intranasally. Outside that market the compound is normally handled as a research chemical rather than a medicine, and no widely recognised international pharmacopoeial monograph exists. The name Selank is a coined trade designation rather than a systematic chemical name.
Enzymatic stability motivates the extra three residues at the carboxyl end. Native tuftsin is cleaved quickly by circulating aminopeptidases and carboxypeptidases, which limits its duration of action and its usefulness as a tool compound. Extending the chain with proline-rich segments is a common design tactic because proline constrains the backbone and slows proteolysis. The same Pro-Gly-Pro motif appears in other Russian-developed peptides of the era. Whether the full seven-residue chain is required for activity, or whether it acts mainly as a prodrug releasing tuftsin, remains unresolved.
| Property | Value | Notes |
|---|---|---|
| Dry storage temperature | -20 C or below | Sealed, desiccated, protected from light |
| Solution stability | Hours to days at 2-8 C | Depends on buffer and microbial load |
| Preferred pH range | Near neutral to slightly acidic | Alkaline pH accelerates hydrolysis |
| Main degradation routes | Hydrolysis and deamidation | No cysteine or methionine in sequence |
| Identity confirmation | Electrospray mass spectrometry | Observed mass compared with 751.9 Da |
Lyophilized selank is normally supplied as a dry powder and is considered stable for extended periods when kept cold and dry. Moisture uptake is the main practical threat, because absorbed water promotes both hydrolysis and aggregation in the solid state. Vials are usually warmed to room temperature before opening so that condensation does not form on the powder. Supplier documentation commonly specifies -20 °C for routine storage, with -80 °C used for material intended to be archived for years.
Once dissolved, the peptide is markedly less stable than the dry powder. Aqueous solutions are subject to backbone hydrolysis and to microbial growth when they are handled without sterile technique. Buffered solutions near neutral pH are common for short-term laboratory work, while acidic conditions are sometimes used to improve solubility. Analytical laboratories generally prepare working solutions fresh rather than storing them, and a residual water film left in a reopened vial can seed degradation even when the container appears dry.
Reversed-phase high-performance liquid chromatography is the standard technique for estimating peptide purity. The result is a peak-area percentage, which describes how much of the detected material elutes as the main peak in one run. Mass spectrometry confirms the molecular mass and can reveal truncated, adducted, or otherwise modified species. Amino acid analysis or tandem mass spectrometry can address sequence fidelity when identity is in doubt. None of these measurements, taken alone, establishes that a sample is fit for any specific purpose.
Selank is a synthetic heptapeptide developed in Russia as a structural analogue of tuftsin, a naturally occurring immunomodulatory tetrapeptide. Its sequence, Thr-Lys-Pro-Arg-Pro-Gly-Pro, keeps the tuftsin core at the N-terminus and appends a Pro-Gly-Pro tail. Researchers at the Institute of Molecular Genetics in Moscow synthesized the compound during the 1990s while searching for peptides with combined anxiolytic and immunomodulatory activity. The added tail was intended to resist enzymatic cleavage and prolong the molecule's presence in circulation.
The compound has a calculated molecular weight near 751.9 daltons and carries a net positive charge at physiological pH because of its arginine residue. It dissolves freely in water and in common aqueous buffers, and typically appears as a white or off-white lyophilized powder. The amide backbone makes the molecule susceptible to peptidases, which limits oral use and favors intranasal or parenteral routes. Nomenclature in the literature varies: the substance is also described by the sequence abbreviation TP-7 and by a Russian trade designation.
The compound was designed at the Institute of Molecular Genetics of the Russian Academy of Sciences during the 1980s and 1990s. The stated design goal was to retain the immunomodulatory and central nervous system activity attributed to tuftsin while improving resistance to enzymatic breakdown. Adding a proline-rich tail to the short parent peptide was a deliberate strategy, because proline residues restrict the conformations available to many peptidases. The same laboratory produced Semax, an ACTH fragment analog, and both compounds were developed in parallel as short, enzymatically stabilized peptides intended for intranasal use.
Selank is not a naturally occurring peptide and has no known endogenous counterpart in human physiology. Russian-language sources frequently call it TP-7, while English-language sources use the name Selank almost exclusively. Database indexing is uneven, partly because early reports appeared in regional journals that are not widely cataloged. Some summaries describe the material as a tuftsin analog and others as a synthetic heptapeptide; the labels overlap rather than conflict. Citing the primary sequence resolves ambiguity more reliably than the research or trade name alone.
Steps to prevent diabetic foot ulcers include frequent review by a foot specialist and multidisciplinary team, good foot hygiene, diabetic socks and shoes, as well as avoiding injury. Foot-care education combined with increased surveillance can reduce the incidence of serious foot lesions. There is no high-quality research that evaluate the complex intervention of combining two or more preventive strategies in preventing diabetic foot ulcer.
Rimonabant was originally approved as an anti-obesity drug. It confers a weight-lowering effect by inhibiting the appetite stimulating effect of cannabinoid receptor 1 (CBR1). Weight loss is achieved with continued treatment, but rebound upon stopping. Despite its efficacy, Rimonabant was withdrawn worldwide due to increased risks of depression, anxiety and suicide. Its withdrawal dispelled research interest on CBR1 modulators, with recent investigation on pharmacological strategies to avoid serious side effects.
=== August === 6 August – Tom O'Connor, journalist, author, senior citizens' advocate and local politician, president of Grey Power (2016–2018), Waimate District Councillor (since 2013) (born 1944). 8 August Judy Bailey, pianist, composer, jazz musician and educator (Sydney Conservatorium of Music), and television presenter (Play School) (born 1935). Peter Lester, sailor, sailing coach and commentator, OK dinghy world champion (1977), Admiral's Cup winner (1987, 1993) (born 1954). 10 August – Patrick Waddington, Russian linguist, literary critic and historian (Victoria University of Wellington) (born 1934). 13 August – Grant Tavinor, philosopher (Lincoln University) (born c. 1973). 15 August – John Rowan, lawyer, King's Counsel (since 1997) (born 1944). 16 August – Janet Grieve, biological oceanographer (New Zealand Oceanographic Institute, NIWA), New Zealand Association of Scientists president (1998–2000), World Association of Copepodologists president (2008–2011) (born 1940). 17 August – John Bartley, cinematographer (Lost, The X Files, The Chronicles of Riddick), Emmy Award (1996) (born 1947). 18 August Lloyd Ashby, rugby union player (Southland, national team) (born 1931). Lindsay Sparks, cricketer (Central Districts, Auckland) and rugby union player (Marlborough) (born 1944). 19 August – Tony Smith, legal scholar (University of Reading, University of Cambridge, Victoria University of Wellington) (born 1947). 21 August Evelyn Attwood, tennis player (born 1924). Keith Nelson, rugby union player (Otago, Auckland, national team) and dentist (born 1938).
Sources: en.wikipedia.org
== Typical technique == A sample is introduced, either manually or with an autosampler, into a sample loop of known volume. A buffered aqueous solution known as the mobile phase carries the sample from the loop onto a column that contains some form of stationary phase material. This is typically a resin or gel matrix consisting of agarose or cellulose beads with covalently bonded charged functional groups. Equilibration of the stationary phase is needed in order to obtain the desired charge of the column. If the column is not properly equilibrated the desired molecule may not bind strongly to the column. The target analytes (anions or cations) are retained on the stationary phase but can be eluted by increasing the concentration of a similarly charged species that displaces the analyte ions from the stationary phase. For example, in cation exchange chromatography, the positively charged analyte can be displaced by adding positively charged sodium ions. The analytes of interest must then be detected by some means, typically by conductivity or UV/visible light absorbance. Control an IC system usually requires a chromatography data system (CDS). In addition to IC systems, some of these CDSs can also control gas chromatography (GC) and HPLC.
== Diagnosis == The diagnosis of a migraine is based on signs and symptoms. A headache calendar is a useful diagnostic tool for tracking the date, duration, and symptoms of headaches. Migraines can be classified by whether the patient experiences an aura (MA) or not (MO) and headache frequency (episodic or chronic). According to the International Classification of Headache Disorders (ICHD-3), migraine diagnosis is primarily clinical and based on identifying characteristic patterns of headache features and associated symptoms rather than laboratory or imaging findings. Neuroimaging tests are not necessary to diagnose migraine, but may be used to find other causes of headaches in those whose examination and history do not confirm a migraine diagnosis. The American Headache Society's guideline recommends neuroimaging only when "red-flag" symptoms or abnormal neurological findings are present, noting that routine imaging is unnecessary for patients who already meet clinical criteria for migraine. The diagnosis of migraine without aura, according to the International Headache Society, can be made according to the "5, 4, 3, 2, 1 criteria", which is as follows:
The capillary wall performs an important function by allowing nutrients and waste substances to pass across it. Molecules larger than 3 nm such as albumin and other large proteins pass through transcellular transport carried inside vesicles, a process which requires them to go through the cells that form the wall. Molecules smaller than 3 nm such as water and gases cross the capillary wall through the space between cells in a process known as paracellular transport. These transport mechanisms allow bidirectional exchange of substances depending on osmotic gradients. Capillaries that form part of the blood–brain barrier only allow for transcellular transport as tight junctions between endothelial cells seal the paracellular space. Capillary beds may control their blood flow via autoregulation. This allows an organ to maintain constant flow despite a change in central blood pressure. This is achieved by myogenic response, and in the kidney by tubuloglomerular feedback. When blood pressure increases, arterioles are stretched and subsequently constrict (a phenomenon known as the Bayliss effect) to counteract the increased tendency for high pressure to increase blood flow. In the lungs, special mechanisms have been adapted to meet the needs of increased necessity of blood flow during exercise. When the heart rate increases and more blood must flow through the lungs, capillaries are recruited and are also distended to make room for increased blood flow. This allows blood flow to increase while resistance decreases.
Sources: en.wikipedia.org
Reflecting different national usages, cunt is described as "an unpleasant or stupid person" in the Compact Oxford English Dictionary, whereas the Merriam-Webster has a usage of the term as "usually disparaging and obscene: woman", noting that it is used in the United States as "an offensive way to refer to a woman". Random House defines it as "a despicable, contemptible or foolish man". Some feminists of the 1970s sought to eliminate disparaging terms such as cunt. Twat is widely used as a derogatory epithet, especially in British English, referring to a person considered obnoxious or stupid. Pussy can indicate "cowardice or weakness", and "the human vulva or vagina" or by extension "sexual intercourse with a woman". In English, the use of the word pussy to refer to women is considered derogatory or demeaning, treating people as sexual objects.
=== Synthetic scaffolds === The use of natural materials in scaffolds has its disadvantages. Usually, they are expensive, not available in large quantities and they have the risk of disease transmission. This has led to the development of synthetic scaffolds. When producing synthetic scaffolds there is full control over their properties. For example, they can be made to have good mechanical properties and the right biodegradability. When it comes to synthetic scaffolds thickness, porosity and pore size are important factors for controlling connective tissue formation. Examples of synthetic scaffolds are:
=== Achondrogenesis type 2 === Several kinds of mutations in the COL2A1 gene are responsible for achondrogenesis type 2. These include missing pieces of the gene, substitution of the amino acid glycine with another amino acid, or changes that result in truncated proteins. All these mutations disrupt the production of mature type II collagen, affecting tissues rich in this collagen.
Sources: en.wikipedia.org
Dry powder is best kept sealed, protected from light, and held at minus 20 degrees Celsius or below. Desiccant packaging helps limit moisture uptake because the material is hygroscopic. A sealed vial should be allowed to equilibrate to room temperature before opening to reduce condensation.
Hydrolysis of peptide bonds and deamidation of arginine and proline residues are the main degradation routes. Alkaline pH and higher temperatures accelerate both processes. Buffered, near-neutral solutions stored cold generally degrade more slowly than unbuffered ones.
Reverse-phase chromatography gives the clearest single view of related impurities and truncated sequences. Mass spectrometry then confirms that the main peak carries the expected mass. Neither test detects enantiomeric impurities, which require a separate chiral assay.
Selank is a seven-amino-acid peptide built from the tuftsin sequence plus a Pro-Gly-Pro tail. It is produced by chemical synthesis rather than extracted from a natural source. The free peptide is usually supplied as a lyophilised powder or in an aqueous formulation.