RP-HPLC comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Last reviewed on 2025-11-18. Where a claim depends on a specific study, the study is described rather than over-claimed.
Once dissolved, the peptide is considerably less stable than the solid. Aqueous solutions are usually prepared at neutral to slightly acidic pH, filtered, and divided into single-use aliquots before freezing. Repeated freeze-thaw cycles are a common cause of avoidable loss and are best prevented by never refreezing a thawed aliquot. Adsorption to plastic and glass surfaces can lower the measured concentration of dilute solutions, particularly below roughly 0.1 mg/mL. Buffer choice, salt content, and container material all influence how much peptide remains detectable after storage.
Identity and purity are established with standard peptide methods. Reversed-phase HPLC with ultraviolet detection near 214 nm resolves the parent peak from deletion and truncation byproducts, and reports typically quote a main-peak percentage. Mass spectrometry by electrospray or MALDI-TOF confirms the expected molecular mass, while amino acid analysis or peptide mapping can verify composition when the sequence itself is in question. A certificate of analysis that pairs a chromatogram with a mass spectrum is more informative than a purity figure alone. Counter-ion content and residual solvents are separate specifications and are frequently omitted.
Identity and purity of semax are established with reversed-phase high-performance liquid chromatography coupled to ultraviolet detection, usually at 214 nanometres. Mass spectrometry, most often electrospray ionisation in positive mode, confirms the molecular mass and reveals truncated sequences. Amino acid analysis and peptide mapping after enzymatic digestion provide additional structural confirmation. Laboratories typically report purity as the percentage area of the main peak, a figure that does not capture isomeric or oxidised variants unless the method resolves them.
The peptide is prone to several degradation pathways. Oxidation of the methionine residue produces a sulfoxide that elutes close to the parent peak in many chromatographic systems. Hydrolysis of peptide bonds and deamidation of susceptible residues in related sequences also reduce purity over time. Lyophilised material kept dry at minus twenty degrees Celsius and shielded from light is the most stable form commonly described in laboratory practice.
| Property | Value | Notes |
|---|---|---|
| Solid storage temperature | -20 °C or below | Desiccated and protected from light |
| Solution storage temperature | -80 °C as single-use aliquots | Avoid repeated freeze-thaw cycles |
| Purity assessment method | RP-HPLC, around 214 nm | Reported as main-peak area percent |
| Identity confirmation method | ESI-MS or MALDI-TOF | Measured mass compared with calculated mass |
| Common synonyms | ACTH(4-10) analog; Met-Glu-His-Phe-Pro-Gly-Pro | Also written as Semaxum in some sources |
=== Other drugs === Certain medications can decrease the absorption of orally consumed vitamin B12, including colchicine, extended-release potassium products, and antibiotics such as gentamicin, neomycin and tobramycin. Anti-seizure medications phenobarbital, pregabalin, primidone and topiramate are associated with lower than normal serum vitamin concentration. However, serum levels were higher in people prescribed valproate. In addition, certain drugs may interfere with laboratory tests for the vitamin, such as amoxicillin, erythromycin, methotrexate and pyrimethamine.
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In the first step of nixtamalization, kernels of dried maize are cooked in an alkaline solution at or near the mixture's boiling point. After cooking, the maize is steeped in the cooking liquid for a period. The length of time for which the maize is boiled and soaked varies according to local traditions and the type of food being prepared, with cooking times ranging from a few minutes to an hour, and soaking times from a few minutes to about a day. During cooking and soaking, a number of chemical changes take place in the grains of maize. Because plant cell wall components, including hemicellulose and pectin, are highly soluble in alkaline solutions, the kernels soften and their pericarps (hulls) loosen. The grain hydrates and absorbs calcium or potassium (depending on the alkali used) from the cooking solution. Starches swell and gelatinize, and some starches disperse into the liquid. Certain chemicals from the germ are released that allow the cooked grains to be ground more easily, yet make dough made from the grains less likely to tear and break down. Cooking changes the grain's protein matrix, which makes proteins and nutrients from the endosperm of the kernel more available to the human body.
Sources: en.wikipedia.org
==== Ribose aminooxazoline (RAO), a critical RNA precursor molecule ==== Ribose aminooxazoline (RAO) is a pentose aminooxazoline, first identified in 1970 as an important intermediate for ribonucleotide biosynthesis when it was shown to produce α-cytidine, a stereoisomer of the biologically-produced nucleoside β-cytidine. Over three decades later, the abiotic synthesis of RAO was achieved from the reaction of cyanamide and the simple 2- and 3-carbon compounds glycoaldehyde and glyceraldehyde, a demonstration of prebiotically feasible cyanosulfidic chemistry. Subsequent research additionally established an abiotic pathway from RAO to the pyrimidine ribonucleosides β-cytidine and β-uridine, revealing a plausible synthetic pathway to RNA monomers from simple chemical precursors that could have been available on the early Earth. Research into the synthesis of purine ribonucleosides is still underway, although a pathway from RAO to purine deoxyribonucleosides has been elucidated.
== Defects and disease == There is evidence to believe that certain defects of any components of the elastic matrix may impair and alter the structural appearance of elastic and collagen fibers. Cutis laxa and Williams syndrome have elastic matrix defects that have been directly associated with alterations in the elastin gene. Alpha-1 antitrypsin deficiency is a genetic disorder where elastin is excessively degraded by elastase, a degrading protein released by neutrophils during the inflammatory response. This leads most often to emphysema and liver disease in affected individuals. Buschke–Ollendorff syndrome, Menkes disease, pseudoxanthoma elasticum, and Marfan's syndrome have been associated with defects in copper metabolism and lysyl oxidase or defects in the microfibril (defects in fibrillin, or fibullin for example). Hurler disease, a lysosomal storage disease, is associated with an altered elastic matrix. Hypertension and some congenital heart defects are associated with alterations in the great arteries, arteries, and arterioles with alterations in the elastic matrix.
which is, like r, a measure of the principal orientation and disorder of the structure being imaged. Since it is often performed in long cylindrical filaments (like collagen), this anisotropy is often equal to
Chlorpromazine has been found to increase propranolol levels by 1.7-fold. The non-selective CYP450 inhibitor cimetidine has been found to increase peak propranolol levels by 1.4-fold and area-under-the-curve levels by 1.5-fold. Cigarette smoking, which induces CYP1A2, has been found to increase the clearance of propranolol by 77%, resulting in decreased propranolol concentrations. The lipid-lowering drugs cholestyramine and colestipol decreased propranolol levels by up to 50%. Aluminum hydroxide gel may decrease propranolol levels. Alcohol may increase propranolol levels.
Sources: en.wikipedia.org
The first death row prisoner to be hanged in Singapore during the COVID-19 pandemic was 68-year-old Singaporean drug offender Abdul Kahar Othman on 30 March 2022, who had not appealed against his sentence and later executed as scheduled, therefore resuming executions in Singapore. By the time Abdul Kahar was executed, there were 62 prisoners on death row, awaiting execution (reduced to 61 with Nagaenthran's execution). Nagaenthran K. Dharmalingam was the second to be hanged on 27 April 2022 after Abdul Kahar. Datchinamurthy Kataiah was originally the third in line to be executed on 29 April 2022 after Nagaenthran before his execution was postponed due to an appeal. On 7 July 2022, Kalwant Singh Jogindar Singh and Norasharee Gous became the third and fourth convicts to be hanged in Singapore in 2022. In the same month, Nazeri Lajim was executed 15 days after Kalwant and Norasharee. Three more hangings - one on 26 July and two (Malaysian Rahmat Karimon and his accomplice Zainal Hamad) on 2 August - were conducted after Nazeri's execution. On 5 August 2022, 45-year-old Singaporean Abdul Rahim Shapiee and his 49-year-old accomplice Ong Seow Ping were the ninth and tenth to be executed. A 55-year-old Singaporean, whose name is unknown, was the eleventh to be executed for a drug charge on 7 October 2022. In total, eleven executions, all for drug trafficking, took place in the year 2022. In 2023, the first execution was carried out on 26 April 2023, when a 46-year-old Singaporean Tangaraju Suppiah, who was convicted in 2018 of marijuana trafficking, was hanged at dawn.
The Human Genetics Society of Australasia (HGSA) is a membership organization for individuals in the field of human genetics who primarily practise in the Oceania region. Members typically hold both a qualification in human genetics and work in the field. Membership is drawn from clinical, laboratory and academic specialties. Members include clinical geneticists; genetic counsellors; laboratory scientists (molecular, cytogenetic and biochemical genetics); and academics (lecturers and researchers).
== Single-cell isolation == Many single-cell analysis techniques require the isolation of individual cells. Methods currently used for single-cell isolation include: dielectrophoretic digital sorting, enzymatic digestion, fluorescence-activated cell sorter, hydrodynamic traps, laser capture microdissection, manual picking, microfluidics, inkjet printing, micromanipulation, serial dilution, and Raman tweezers. Manual single-cell picking is a method where cells in suspension are viewed under a microscope and individually picked using a micropipette. The Raman tweezers technique combines Raman spectroscopy with optical tweezers, using a laser beam to trap and manipulate cells. The dielectrophoretic digital sorting method utilizes a semiconductor-controlled array of electrodes in a microfluidic chip to trap single cells in dielectrophoretic (DEP) cages. Cell identification is ensured by the combination of fluorescent markers with image observation. Precision delivery is ensured by the semiconductor-controlled motion of DEP cages in the flow cell. Inkjet printing combines microfluidics with MEMS on a CMOS chip to provide individual control over a large number of print nozzles, using the same technology as home Inkjet printing. Inkjet printing allows for the adjustment of shear force to the sample ejection, greatly improving cell survivability.
== Arts and entertainment == CoLD SToRAGE, an alias of the musician Tim Wright (born 1967) Cold Storage (1951 film), an animated short starring Disney's Pluto The Walking Dead: Cold Storage, a 2012 four-part webisode series for The Walking Dead TV series Cold Storage (novel), a 2019 science fiction novel by David Koepp Cold Storage (film), a 2026 film adaptation of Koepp's novel
Their first son Prince Aegon was born in 120 AC, while their second son was born in 122 AC and named after Viserys. In 126 AC, Rhaenyra requested that Luke be recognized as the heir to Driftmark, which several members of House Velaryon protested under the accusation that he was not Laenor's son. As Viserys angrily ordered their tongues to be cut out, he slipped and cut his hand on the Iron Throne, a severe injury that gave him a fever from infection. Some maesters feared that he would die, but Viserys lived after two of his fingers were removed by Maester Gerardys, and he would never sit on the Iron Throne again. Gerardys was recommended by Rhaenyra as a replacement for the dead Grand Maester Mellos, while Alicent recommended Maester Alfador, her family's maester. Viserys decided to appoint neither man as Grand Maester and deferred to the Citadel to fill the office, who chose Maester Orwyle. As Viserys' health gradually weakened, Otto filled the small council with members loyal to the greens, including Lord Larys Strong, Ser Tyland Lannister, and Ser Jasper Wylde. Lord Commander of the Kingsguard Criston Cole was also an ardent supporter of Alicent, with Orwyle being politically neutral and Lord Lyman Beesbury opposing the greens. Viserys passed away in his sleep in 129 AC, having been discovered by a servant who informed Alicent of his status. In the interim, Alicent did not disclose Viserys' death to the public and summoned the small council to a secret meeting.
Sources: en.wikipedia.org
Each freeze-thaw cycle can degrade a fraction of the peptide and promote aggregation. Dividing a stock solution into single-use volumes removes repeated cycling as a variable. It also limits the time a thawed solution spends at room temperature.
A high main-peak percentage says little about identity, counter-ion content, or residual solvents. It also does not distinguish an isomer or a closely eluting analog. Mass confirmation and the accompanying documentation cover those gaps.
Salt form changes mass, solubility, and hygroscopicity, and acetate and trifluoroacetate salts behave differently in solution. Storage guidance still centers on -20 °C for powder and lower temperatures for solutions. The certificate should state which salt is present.
Reversed-phase high-performance liquid chromatography is the standard method, with detection in the ultraviolet range. Peak area percentage yields a purity figure for the main component. Mass spectrometry is normally run alongside to confirm molecular identity.