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 2026-06-03. Where a claim depends on a specific study, the study is described rather than over-claimed.
Stability depends on pH, temperature, oxygen exposure, and trace metals. Aqueous solutions of reduced glutathione are susceptible to oxidation, especially when neutral or alkaline and exposed to air. Transition metal ions can catalyze thiol oxidation, so chelators and inert atmospheres are sometimes used in research settings. Standards are typically stored cold and desiccated, with limited freeze-thaw cycles. Questions remain about how closely in vitro stability data reflect the behavior of glutathione within intact cells and tissues.
Measuring glutathione requires attention to oxidation during sample handling, because GSH in biological samples can convert to GSSG or form mixed disulfides with proteins after collection. Acidic extraction, rapid cooling, and chelating agents are commonly used to limit such changes. Analytical methods usually distinguish free reduced glutathione, total glutathione, and protein-bound forms. Because these forms have different stability and reactivity, reported values depend heavily on the preparation protocol. No single preparation is universally suitable for every biological matrix or analytical goal.
Several techniques are used for quantification. Enzymatic recycling assays rely on glutathione reductase and a colorimetric or fluorescent readout, offering sensitivity for total glutathione. High-performance liquid chromatography can separate GSH from GSSG and other thiols, often with UV, fluorescence, or electrochemical detection. Mass spectrometry provides structural confirmation and can quantify low-abundance species when paired with separation. Each approach has trade-offs in specificity, throughput, and equipment requirements, so method selection depends on the research question and available instrumentation.
Storage recommendations for glutathione reagents usually specify a cool, dry, dark environment because the thiol oxidizes in air and light. Solid material is often kept desiccated at low temperature, while solutions are prepared fresh or stored frozen in aliquots. Repeated freeze-thaw cycles can accelerate degradation, and metal ions can catalyze oxidation. Quality control may include purity assays, water content, and identity confirmation. Stability limits are method-specific, so a stated shelf life applies only to defined conditions and packaging.
Laboratory measurement of glutathione requires attention to oxidation before analysis. Blood, tissue, or cell samples can lose reduced glutathione as it converts to GSSG or forms mixed disulfides with proteins. Acid extraction, rapid freezing, and thiol-blocking reagents are common strategies to preserve the original distribution. Reported concentrations therefore depend on collection protocol, extraction method, and the time between sampling and analysis. Comparisons across studies are most reliable when these pre-analytical variables are described.
Common analytical approaches include enzymatic recycling assays, high-performance liquid chromatography, and mass spectrometry. The enzymatic recycling assay uses glutathione reductase and a colorimetric or fluorometric reagent to amplify signal, which gives good sensitivity for total glutathione. Chromatographic methods can separate GSH from GSSG and related thiols, while mass spectrometry offers structural confirmation and multiplexing. Each approach has different requirements for calibration, internal standards, and validation. No single method captures every form of glutathione in every matrix.
| Property | Value | Notes |
|---|---|---|
| Reduced form | GSH | Main intracellular thiol |
| Oxidized form | GSSG | Disulfide dimer of two GSH molecules |
| Common separation method | Reversed-phase HPLC | Often with ion-pairing or derivatization |
| Typical detection | Fluorescence or mass spectrometry | UV detection is also used in some assays |
| Storage of standards | -20 °C or below, desiccated | Limit freeze-thaw and moisture exposure |
Commercial glutathione is available in research-grade, food-grade, and supplement-grade forms, and purity specifications differ accordingly. Certificates of analysis commonly report identity by nuclear magnetic resonance or mass spectrometry, purity by HPLC, residual solvents, and heavy metals. Reference standards with assigned purity support calibration, while isotopically labeled glutathione can serve as an internal standard for mass spectrometry. For supplements, label claims may not be independently verified, and regulatory oversight varies by country. Verification often involves third-party testing for identity, potency, and contaminants.
Quantifying glutathione requires distinguishing GSH from GSSG and preventing oxidation during sample preparation. Common approaches include the enzymatic recycling assay, often called the Tietze method, which measures total glutathione after converting GSSG to GSH. HPLC with ultraviolet or fluorescence detection and LC-MS/MS can separate and quantify both forms, sometimes after derivatization of the thiol group. Blood, plasma, and tissue samples differ in matrix and baseline concentrations, so method validation must account for recovery, linearity, and interference. No single assay is universally standard.
Glutathione is most stable as a dry powder stored cool and dry, but its thiol group is readily oxidized in solution. Aqueous preparations at neutral or alkaline pH lose GSH faster because the thiolate form reacts with dissolved oxygen and metal ions. Acidic conditions, chelating agents, and oxygen exclusion can slow oxidation, while repeated freeze-thaw cycles promote degradation. Light exposure and trace metals also contribute to loss. Laboratories typically validate stability for their own matrices because degradation rates depend on pH, temperature, concentration, and container materials.
Glutathione reference materials are sensitive to oxygen, light, and elevated temperature. Solid material is typically stored desiccated at -20 °C or below, while solutions require tighter control because thiol oxidation proceeds faster in liquid form. Aqueous solutions are often prepared fresh, kept cold, and protected from air; some protocols add acid or chelating agents to slow metal-catalyzed oxidation. Repeated freeze-thaw cycles can accelerate degradation and should be avoided. Stability data vary by matrix, so laboratories usually verify performance with their own storage conditions.
Quality control for glutathione measurements includes calibration with authenticated standards, internal standards where available, blank correction, and spike recovery checks. Because glutathione can form during sample processing or degrade before analysis, pre-analytical handling is a major source of variability. Interlaboratory comparisons often show differences in reported values due to method-specific calibration and detection principles. Interpretive thresholds are context-dependent, and no single reference range applies across all tissues or matrices. Researchers generally report both reduced and oxidized forms, along with the method and sample handling details.
Quantification of glutathione in biological or food samples commonly uses liquid chromatography coupled to ultraviolet, fluorescence, electrochemical, or mass spectrometric detection. Because the thiol group oxidizes readily, samples are often acidified or derivatized immediately after collection to stabilize reduced glutathione. Enzymatic recycling assays and colorimetric kits offer higher throughput but generally lower specificity than chromatographic methods. Mass spectrometry can distinguish glutathione from related thiols and allow simultaneous measurement of oxidized forms. Reported concentrations depend strongly on sample type, extraction procedure, and analytical platform.
Commercial glutathione is produced by microbial fermentation or chemical synthesis, then purified. Reduced and oxidized grades are offered separately, with purity specifications often exceeding 98 percent. The compound appears in foods such as fresh fruits, vegetables, and meats, although cooking and processing can lower amounts. Oral, topical, and inhaled forms are discussed in research and consumer contexts, but absorption and tissue delivery remain active areas of study. Regulatory status varies by country and intended use.
Glutathione is a small sulfur-containing peptide built from glutamic acid, cysteine, and glycine. Its distinctive feature is a gamma-glutamyl bond between glutamate's side-chain carboxyl group and cysteine's amino group. This linkage resists ordinary peptidases and helps the molecule remain stable inside cells. The reduced thiol form, often abbreviated GSH, is the dominant intracellular species. The oxidized disulfide dimer, GSSG, forms when two reduced molecules link through their cysteine sulfur atoms. The balance between these forms is a common redox indicator.
Samples for glutathione analysis require careful handling because the compound oxidizes readily and can be consumed by enzymes after collection. Blood is often treated with acid or thiol-blocking agents soon after draw, and plasma should be separated quickly from red blood cells. Tissues are usually snap-frozen or extracted immediately. Aqueous solutions of glutathione are less stable than dry powder and degrade faster at neutral or alkaline pH, in light, or with dissolved oxygen. Repeated freeze-thaw cycles also reduce reliability.
Quality control for glutathione materials checks identity, assay, purity, water content, and disulfide content. Commercial products vary from research-grade powder to dietary supplements, and labels may not distinguish reduced from oxidized forms. In the United States, oral glutathione is commonly sold as a dietary supplement rather than an approved drug, while injectable forms fall under different rules and may require a prescription. Regulatory status differs by country. Analytical certificates, when available, help verify what a material contains, but independent testing remains important for interpretation.
=== Long-overlap-based assembly === There have been a variety of long-overlap-based assembly methods developed in recent years. One of the most commonly used methods, the Gibson assembly method, was developed in 2009, and provides a one-pot DNA assembly method that does not require the use of restriction enzymes or integrases. Other similar overlap-based assembly methods include Circular Polymerase Extension Cloning (CPEC), Sequence and Ligase Independent Cloning (SLIC) and Seamless Ligation Cloning Extract (SLiCE). Despite the presence of many overlap assembly methods, the Gibson assembly method is still the most popular. Besides the methods listed above, other researchers have built on the concepts used in Gibson assembly and other assembly methods to develop new assembly strategies like the Modular Overlap-Directed Assembly with Linkers (MODAL) strategy, or the Biopart Assembly Standard for Idempotent Cloning (BASIC) method.
=== Size === The smallest bat, and one of the smallest mammals, is Kitti's hog-nosed bat (Craseonycteris thonglongyai), which is 29–33 mm (1+1⁄8–1+1⁄4 in) long with a 150-millimetre (6 in) forearm and weighs 2 oz (56+11⁄16 g). The largest species is the giant golden-crowned flying fox (Acerodon jubatus), which can weigh 1.5 kg (3+1⁄4 lb) with a wingspan of 1.6 m (5 ft 3 in). Larger bats tend to use lower frequencies and smaller bats higher for echolocation; high-frequency echolocation is better at detecting smaller prey. Small prey may be absent in the diets of large bats as they are unable to detect them.
Fluoxetine has been shown to inhibit acid sphingomyelinase, a key regulator of ceramide levels which derives ceramide from sphingomyelin. Fluoxetine has a direct interaction with Tropomyosin receptor kinase B (TrkB), in which fluoxetine binds to the cholesterol site on TrkB, which "facilitates" Brain-derived neurotrophic factor signalling and reduces the amount of TrkB in a inactive state. This action also raises the surface expression of TrkB receptors.
University-based ophthalmologists in the US and Canada further refined the use of botulinum toxin as a therapeutic agent. By 1985, a scientific protocol of injection sites and dosage had been empirically determined for treatment of blepharospasm and strabismus. Side effects in treatment of this condition were deemed to be rare, mild and treatable. The beneficial effects of the injection lasted only four to six months. Thus, blepharospasm patients required re-injection two or three times a year. In 1986, Scott's micromanufacturer and distributor of Botox was no longer able to supply the drug because of an inability to obtain product liability insurance. People became desperate, as supplies of Botox were gradually consumed, forcing him to abandon people who would have been due for their next injection. For a period of four months, American blepharospasm patients had to arrange to have their injections performed by participating doctors at Canadian eye centers until the liability issues could be resolved. In December 1989, Botox was approved by the US FDA for the treatment of strabismus, blepharospasm, and hemifacial spasm in people over 12 years old. In the case of treatment of infantile esotropia in people younger than 12 years of age, several studies have yielded differing results.
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.
Sources: en.wikipedia.org
α granules (alpha granules) — containing P-selectin, platelet factor 4, transforming growth factor-β1, platelet-derived growth factor, fibronectin, B-thromboglobulin, vWF, fibrinogen, and coagulation factors V and XIII δ granules (delta or dense granules) — containing ADP or ATP, calcium, and serotonin γ granules (gamma granules) — similar to lysosomes and contain several hydrolytic enzymes λ granules (lambda granules) — contents involved in resorption during later stages of vessel repair
The steam ejector is a popular form of pump for vacuum distillation and freeze-drying. A jet of steam entrains the vapour that must be removed from the vacuum chamber. Steam ejectors can have single or multiple stages, with and without condensers in between the stages. While both steam ejectors and diffusion pumps use jets of vapor to entrain gas, they work on fundamentally different principles - steam ejectors rely on viscous flow and mixing to pump gas, whereas diffusion pumps use molecular diffusion. This has several consequences. In diffusion pumps, the inlet pressure can be much lower than the static pressure of jet, whereas in steam ejectors the two pressures are about the same. Also, diffusion pumps are capable of much higher compression ratios, and cannot discharge directly to atmosphere.
=== Ontogeny and life history === Neanderthal brain size at birth was similar to modern humans and constrained by the same obstetric factors; mothers giving birth to infants with heads too large to pass through the birth canal would be selected against. Growth in brain volume occurred at a faster pace in Neanderthal infants than in modern human infants, but growth of the brain did not reach completion earlier in Neanderthals than in modern humans owing to the larger brain size of the former. The rate of incisor crown formation in Neanderthals is also indicative of an accelerated pattern of life history relative to modern humans. Estimates of the age at weaning of Neanderthals vary. Barium levels in the enamel of a Belgian Neanderthal tooth from Scladina suggest a weaning age of 1.2 years. Trace element analysis of a Neanderthal tooth from Payre suggests that weaning occurred at about 2.5 years of age.
Ginkgo has long been cultivated in China. It is common in the southern third of the country. Some planted trees at temples are believed to be over 1,500 years old. The first record of Europeans encountering it is in 1690 in Japanese temple gardens, where the tree was seen by the German botanist Engelbert Kaempfer. Because of its status in Buddhism and Confucianism, the ginkgo has also been widely planted in Korea and in Japan since the 14th century; in both areas, some naturalization has occurred, with ginkgos seeding into natural forests. Ginkgo has been commonly cultivated in North America for over 200 years and in Europe for close to 300, but during that time, it has never become significantly naturalized. G. biloba is also commonly manually planted in cities across the United States and Europe. This species is highly tolerant to pollution and serves as a visually appealing, shade-providing tree in many cities and gardens. Many intentionally planted ginkgos are male cultivars grafted onto plants propagated from seed, because the male trees will not produce the malodorous seeds. The popular cultivar 'Autumn Gold' is a clone of a male plant. The disadvantage of male Ginkgo biloba trees is that their pollen is highly allergenic. They have an OPALS (Ogren Plant Allergy Scale) rating of 7 (out of 10), whereas female trees, which can produce no pollen, have an OPALS allergy scale rating of 2.
=== Guided mode manipulations === Metamaterials can be integrated with optical waveguides to tailor guided electromagnetic waves (meta-waveguide). Subwavelength structures like metamaterials can be integrated with for instance silicon waveguides to develop and polarization beam splitters and optical couplers, adding new degrees of freedom of controlling light propagation at nanoscale for integrated photonic devices. Other applications such as integrated mode converters, polarization (de)multiplexers, structured light generation, and on-chip bio-sensors can be developed.
Sources: en.wikipedia.org
=== 28 January === The SAF claimed to have seized the RSF's Medical Directorate located in the former SAF Paratroopers base in Shambat, as well as the Blue and Bashir Towers in Khartoum Bahri. The RSF announced the death in action of one of its senior commanders, Rahmtalla al-Mahdi, also known as "Jalha", along with his brother. The two were reportedly killed in an airstrike east of Khartoum.
Among other things, this leads to the mature voice being better suited to the rigors of opera. The extracellular matrix of the vocal cord LP is composed of fibrous proteins such as collagen and elastin, and interstitial molecules such as HA, a non-sulfated glycosaminoglycan. While the SLP is rather poor in elastic and collagenous fibers, the ILP and DLP are mostly composed of it, with the concentration of elastic fibers decreasing and the concentration of collagenous fibers increasing as the vocalis muscle is approached. Fibrous proteins and interstitial molecules play different roles within the extracellular matrix. While collagen (mostly type I) provides strength and structural support to the tissue, which are useful to withstanding stress and resisting deformation when subjected to a force, elastin fibers bring elasticity to the tissue, allowing it to return to its original shape after deformation. Interstitial proteins, such as HA, plays important biological and mechanical roles in the vocal cord tissue. In the vocal cord tissue, hyaluronic acid plays a role of shear-thinner, affecting the tissue viscosity, space-filler, shock absorber, as well as wound healing and cell migration promoter. The distribution of those proteins and interstitial molecules has been proven to be affected by both age and gender, and is maintained by the fibroblasts.
== Books == Autobiography Not Bad for a Human – The Life and Films of Lance Henriksen – Lance Henriksen with co-author Joseph Maddrey, published in 2011 by Bloody Pulp Books, featuring art by Bill Sienkiewicz, Mike Mignola, Tom Mandrake, Tim Bradstreet, Eric Powell and Ashley Wood. Comic books To Hell You Ride (five-issue comic book from Dark Horse Comics) (2012) – Lance Henriksen and Joseph Maddrey (co-authors) with Tom Mandrake (artist); a motion-comic video was also made by Dark Horse Comics) (2012) – Lance Henriksen and Joseph Maddrey (co-authors), Tom Mandrake (artist), Lance Henriksen (narrator), TKU: Tecamachalco Underground (Cesar Gallegos/Mateo Latosa) (musical score)
Only six years later, Hurricane Hattie struck the central coastal area of the country, with winds in excess of 300 km/h (185 mph) and 4 m (13 ft) storm tides. The devastation of Belize City for the second time in thirty years prompted the relocation of the capital some 80 kilometres (50 mi) inland to the planned city of Belmopan. In 1978, Hurricane Greta caused more than US$25 million in damage along the southern coast. In 2000, Hurricane Keith, the wettest tropical cyclone in the nation's record, stalled, and hit the nation as a Category 4 storm on 1 October, causing 19 deaths and at least $280 million in damage. Soon after, on 9 October 2001, Hurricane Iris made landfall at Monkey River Town as a 235 km/h (145 mph) Category 4 storm. The storm demolished most of the homes in the village, and destroyed the banana crop. In 2007, Hurricane Dean made landfall as a Category 5 storm only 40 km (25 mi) north of the Belize–Mexico border. Dean caused extensive damage in northern Belize. In 2010, Belize was directly affected by the Category 2 Hurricane Richard, which made landfall approximately 32 kilometres (20 mi) south-southeast of Belize City at around 00:45 UTC on 25 October 2010. The storm moved inland towards Belmopan, causing estimated damage of BZ$33.8 million ($17.4 million 2010 USD), primarily from damage to crops and housing. The most recent hurricane to make landfall in Belize was Hurricane Lisa in 2022. Extreme weather events, such as hurricanes and floods, have become more frequent and intense due to climate change.
Sources: en.wikipedia.org
Common methods include enzymatic recycling assays, liquid chromatography, and mass spectrometry. Many protocols separate reduced glutathione from its oxidized disulfide form before detection.
The ratio compares reduced glutathione with its oxidized dimer. It is used as an indicator of redox status, although the value depends strongly on sample handling and analytical method.
Glutathione can oxidize quickly after a sample is collected. Acidification, cooling, and chelators are often used to reduce artifactual changes before analysis.
Pre-analytical handling, extraction chemistry, and detection method all influence reported glutathione values. Oxidation during sample processing can shift the measured GSH/GSSG ratio. Standardized protocols and reference materials help reduce, but do not eliminate, these differences.