The short version of freeze-thaw fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-03-22. Anything still debated is marked as such rather than presented as settled.
Four amino acid substitutions separate the modified backbone from the parent GRF(1-29) sequence. These changes reduce recognition by dipeptidyl peptidase IV and related proteases, extending the interval before degradation. Development work in this area sought longer-acting GHRH analogs for endocrine investigation. Published descriptions treat the substitution set as a defining property of the core sequence, while the albumin-binding linker is described separately as an optional addition to that same backbone.
CJC-1295 is a synthetic peptide analog of growth hormone-releasing hormone, constructed on the 29-amino-acid fragment designated GRF(1-29). The name began as an internal development code during the 1990s and later spread through research supply catalogs and discussion forums. The molecule does not occur in nature; its sequence is engineered rather than isolated from tissue. Two related compounds are sold under this single label, and they differ by one appended chemical group that strongly influences how long the peptide remains in circulation.
The dividing feature between the two forms is a maleimide-based drug affinity complex, abbreviated DAC. In the DAC-bearing version, a linker attaches the peptide to serum albumin after administration, and that association slows removal from plasma. The version lacking DAC appears in catalogs as MOD GRF(1-29) or tetrasubstituted GRF(1-29). Because informal writing treats both as one item, comparisons drawn from such sources routinely blend measurements taken from two molecules with substantially different behavior.
Receptor level activity follows the canonical GHRH pathway. The peptide binds the GHRH receptor, a class B G protein coupled receptor on somatotroph cells of the anterior pituitary. Binding raises intracellular cyclic AMP, which promotes calcium entry and the release of growth hormone into the bloodstream. Because the molecule acts at the same receptor as the endogenous hormone, its effect is superimposed on the natural pulsatile rhythm rather than replacing it. Whether sustained receptor occupation leads to desensitization is not fully settled.
CJC-1295 belongs to a class of synthetic peptides modeled on growth hormone releasing hormone, a forty-four amino acid signal produced by the hypothalamus. The compound is built from the first twenty-nine residues of the natural sequence, with four substitutions introduced at positions 2, 8, 15 and 27. These changes were designed to slow enzymatic breakdown while preserving receptor activation. The result is a peptide that is shorter than native GHRH and considerably more resistant to ordinary clearance pathways in circulation.
Two related forms appear under the CJC-1295 name. The simpler analogue, commonly written as modified GRF(1-29), carries the four substitutions but no additional conjugation. The second form attaches a maleimidopropionic acid linker to a lysine residue, a modification frequently called the drug affinity complex. That linker reacts with the free thiol on serum albumin to form a covalent bond. Because albumin has a long residence time in blood, the conjugated peptide stays in circulation far longer than the unconjugated analogue.
| Property | Value | Notes |
|---|---|---|
| Molecular class | Synthetic peptide | Analog of growth hormone-releasing hormone |
| Chain length | 29 amino acids | Based on the GRF(1-29) fragment |
| Appearance | White to off-white lyophilized powder | Common research supply form |
| Solubility | Soluble in water and aqueous buffers | Powder requires reconstitution before use |
| Typical storage | −20 °C or below | Kept away from light and moisture |
Pharmacokinetic behaviour differs sharply between the two forms. The DAC-bearing peptide shows an extended circulation time measured in days, whereas the version without the complex is cleared within roughly half an hour. This gap shapes how researchers design dosing schedules in animal models. Whether the prolonged presence of the DAC form produces effects meaningfully different from the short-acting variant remains an open question, since comparative human data are scarce.
CJC-1295 is a synthetic peptide designed to mimic growth hormone-releasing hormone (GHRH), the endogenous signal that prompts the pituitary gland to release growth hormone. The compound is a modified fragment of the natural hormone, spanning the first twenty-nine amino acids of GHRH with several substitutions that slow enzymatic breakdown. Two variants circulate in research settings: one carrying a drug affinity complex (DAC) and one without it. The DAC-free form is frequently labelled Mod GRF(1-29) in catalogs and discussion forums.
The peptide binds GHRH receptors on somatotroph cells within the anterior pituitary, triggering a signalling cascade that increases growth hormone secretion. Its improved resistance to dipeptidyl peptidase IV degradation distinguishes it from the parent hormone. In the DAC-bearing version, a maleimide group reacts with a cysteine residue on serum albumin, forming a covalent bond that keeps the peptide in circulation far longer. That albumin attachment is the central design feature separating the two research variants.
Identity and purity are assessed mainly by reversed-phase high-performance liquid chromatography combined with mass spectrometry. The chromatographic separation resolves the target peptide from truncation products and from species carrying oxidised residues, while mass measurement confirms the expected molecular mass. Because the two common variants differ by roughly 280 daltons, a mass determination distinguishes them unambiguously. Purity is often quoted as a percentage of total peak area, although that figure depends on the detection wavelength and the integration method applied.
Reported half-lives differ widely between the two variants and between species. Values for the albumin-binding form are usually expressed in days, while the unconjugated form is measured in minutes to a few hours. Sampling schedules, assay sensitivity, and route of administration all influence the numbers, which limits direct comparison across studies. Whether sustained receptor occupancy produces different downstream effects from pulsatile stimulation remains an open question in the published work. Claims about relative potency should therefore be read alongside the specific study design that produced them.
Lyophilised powder is the usual supplied form. The material is hygroscopic, so vials are typically equilibrated to room temperature before opening in order to prevent condensation on the contents. Long-term storage is generally described at minus twenty degrees Celsius or colder, protected from light and moisture. Repeated freeze-thaw cycles are avoided because they promote aggregation and loss of soluble material. A reconstituted solution is considerably less stable than the dry powder and is normally kept refrigerated for short periods only.
Reaction between tin tetrachloride and sulfuric acid in a 1:2 molar mixture at near reflux (114 °C): SnCl4 + 2 H2SO4 → Sn(SO4)2 + 4 HCl Pyrolysis of anhydrous tin(IV) sulfate at 150 °C - 200 °C: Sn(SO4)2 → SnO2 + 2 SO3 To further reduce water contamination, Oleum and a slight excess of Tin(IV) Chloride should be used. The slight excess of SnCl4 can then be separated by carefully heating the solid Tin(IV) Sulfate under a vacuum to no more than 120 °C. The excess SO3 from the Oleum and the remaining SnCl4 will react during HCl formation and form Tin(IV) Oxide and Sulfuryl Chloride. If an excess of SO3 in the Oleum is present relative to SnCl4 , the Tin(IV) Oxide will absorb it and form more Tin(IV) Sulfate. The advantage of this method over the sodium bisulfate one is that it can produce the pure trimer of SO3 (since no water is present) while still using safe temperatures for normal borosilicate laboratory glassware. Other dry sulfate salt pyrolysis reactions require higher temperatures which increases the risk of shattering. A disadvantage is that it generates significant quantities of hydrogen chloride gas which needs to be captured as well. SO3 may also be prepared by dehydrating sulfuric acid with phosphorus pentoxide.
=== Microvascular effects (retinopathy) === Initial trials noted an increase in complications related to diabetic retinopathy. Subsequent analyses have clarified that this early worsening of pre-existing retinopathy is a secondary effect caused by the rapid and robust drop in blood glucose levels, rather than a direct toxic effect of semaglutide on the eyes.
=== Supervoltage cancer therapy === Working from an auto garage near Harvard Square, HVEC began building Trump's gas-insulated Van de Graaff generators for hospitals and manufacturers. In 1947, the first orders came from several British hospitals for HVEC's compact 2-megavolt machines. The company was among the first to make artificial radiation sources commercially available for cancer treatment. After three years, HVEC had delivered 17 particle accelerators, employed 140 people, and negotiated $2 million in sales (equivalent to $27.1 million in 2025), eclipsing its competitors' products and undercutting them on price. Nevertheless, the company faced severe financial difficulties in its early years. On several occasions, technical problems brought HVEC to within days of exhausting both money and credit. By the mid-1950s, successor technologies like cobalt-60 machines built by General Electric began dominating hospital orders, offering simpler operation and lower maintenance costs. Although HVEC remained in the medical market until 1969, the company increasingly focused on redesigning its generators for research and industrial applications.
The terminal half-life of elagolix is typically about 4 to 6 hours. A study found that its half-life was 2.4 to 6.3 hours with a single dose and was 2.2 to 10.8 hours with continuous administration. The oral clearance of elagolix is 123 L/hour at 150 mg once per day and 144 L/hour at 200 mg twice per day. The major pathway of elimination of elagolix is hepatic metabolism. Elagolix is taken up from the circulation into the liver by the hepatic OATP1B1 carrier. In people with two reduced function alleles of the gene that encodes OATP1B1 (SLCO1B1 521T>C; SLCO1B1 521 C/C genotype), plasma levels of elagolix have been found to be increased by 78% relative to in people with normal OATP1B1 function (SLCO1B1 521T/T genotype). The frequency of this reduced function OATP1B1 genotype is generally less than 5% in most racial and ethnic groups. Elagolix is excreted less than 3% in urine and 90% in feces. Exposure to elagolix is not affected by renal impairment or mild hepatic impairment, but is increased by approximately 3-fold in women with moderate hepatic impairment and by approximately 7-fold in women with severe hepatic impairment. There were no differences in the pharmacokinetics of elagolix between individuals of different racial and ethnic groups. Similarly, the pharmacokinetics of elagolix were unaffected by body weight and body mass index. Peak and area-under-the-curve levels of elagolix have been shown to be altered by CYP3A4 inhibitors like ketoconazole and CYP3A4 inducers like rifampin.
=== Combination ESG and pharmacologic therapy === ESG can safely be combined with weight loss medications to improve weight loss or prevent weight regain after the procedure. The daily injectable medication liraglutide showed greater total body weight loss when combined with ESG compared to ESG alone at 7 months (approximately 25% vs 20% respectively). Similar results are anticipated with other incretin agents, such as semaglutide and tirzepatide, though no studies have directly assessed these combinations.
Sources: en.wikipedia.org
=== Denaturing-condition electrophoresis === Gel electrophoresis is a common laboratory technique that can be used both as a preparative and analytical method. The principle of electrophoresis relies on the movement of a charged ion in an electric field. In practice, the proteins are denatured in a solution containing a detergent (SDS). In these conditions, the proteins are unfolded and coated with negatively charged detergent molecules. The proteins in SDS-PAGE are separated on the sole basis of their size. In analytical methods, the protein migrate as bands based on size. Each band can be detected using stains such as Coomassie blue dye or silver stain. Preparative methods to purify large amounts of protein, require the extraction of the protein from the electrophoretic gel. This extraction may involve excision of the gel containing a band, or eluting the band directly off the gel as it runs off the end of the gel. In the context of a purification strategy, denaturing condition electrophoresis provides an improved resolution over size exclusion chromatography, but does not scale to large quantity of proteins in a sample as well as the late chromatography columns.
== Structure == In humans, granzyme B is encoded by GZMB on chromosome 14q11.2, which is 3.2kb long and consists of 5 exons. It is one of the most abundant granzymes of which there are 5 in humans and 10 in mice. Granzyme B is thought to have evolved from a granzyme H related precursor and is more effective at lower concentrations than the other granzymes. The enzyme is initially in an inactive precursor zymogen form, with an additional amino terminal peptide sequence. This sequence can be cleaved by cathepsin C, removing 2 amino acids. Cathepsin H has also been reported to activate granzyme B. Granzyme B's structure consists of two six-stranded β sheets with three trans domain segments. In the granules of cytotoxic lymphocytes the enzyme can exist in two glycosylated forms. The high mannose form weighs 32kDa and the complex form, 35kDa. Granzyme B contains the catalytic triad histidine-aspartic acid-serine in its active site and preferentially cleaves after an aspartic acid residue situated in the P1 position. The aspartic acid residue to be cleaved associates with an arginine residue in the enzyme's binding pocket. Granzyme B is active at a neutral pH and is therefore inactive in the acidic CTL granules. The enzyme is also rendered inactive when bound by serglycin in the granules to avoid apoptosis triggering inside the cytotoxic T cells themselves.
=== Dilution to threshold === A dilution series of a sample or extract is prepared and assessed for presence of odour. The result can be described as the odour potency of a compound. One kind of analysis is to measure the maximum dilution in the series in which odour is still perceived. The resulting value is called the flavour dilution (FD) factor in the aroma extraction dilution analysis (AEDA) developed in 1987 by Schieberle and Grosch. On the other hand, another kind of analysis is to also measure the duration of the perceived odour to compute peak areas. The peak areas are known as Charm values in the CharmAnalysis developed in 1984 by Acree and co-workers. The former can then be interpreted as the peak height of the latter. Because the odour threshold of a compound is intended to be measured from a prepared series of dilution (commonly by a factor of 2–3 with 8–10 dilutions), the precision and variation in data can be determined from the dilution factors used. Due to time demand requirements from this method and the general requirement for multiple assessors to minimise errors, having the column split into multiple odour ports would be beneficial for the method.
==== PINK1, PARK7, PRKN ==== PINK1 (PARK6), PARK7 (DJ-1), and PRKN (PARK2, PARKIN) are all involved in mitochondrial activity. Mutations in these genes may cause mitochondrial dysfunction, an element of both idiopathic and familial PD. In addition, the PRKN gene encodes E3 ubiquitin ligase, which is involved in degradation of damaged proteins by ubiquitin. Many different PRKN-related mutations occur, leading to loss of protein or to protein-related loss of function. PRKN is the most common cause of autosomal-recessive PD, accounting for nearly 50% of typical early-onset parkinsonism. PRKN mutations account for 77% of juvenile PD cases. PINK1 encodes PTEN-induced putative kinase 1, and is the second-most common cause of autosomal-recessive PD. The PARK7 gene is located on chromosome 1p36 and encodes the DJ-1 protein. The DJ-1 protein is involved in cellular sensing of oxidative stress. DJ-1 related PD is rare, occurring in 0.4% - 1% of patients with early-onset PD.
==== 1980s–early 1990s ==== The modern use of the term designer drug was coined in the 1980s to refer to various synthetic opioid drugs, based mostly on the fentanyl molecule (such as α-methylfentanyl). The term gained widespread popularity when MDMA (ecstasy) experienced a popularity boom in the mid-1980s. When the term was coined in the 1980s, a wide range of narcotics were being sold as heroin on the black market. Many were based on fentanyl or meperidine. One, MPPP, was found in some cases to contain an impurity called MPTP, which caused brain damage that could result in a syndrome identical to late stage Parkinson's disease, from only a single dose. Other problems were highly potent fentanyl analogues that caused many accidental overdoses. Because the government was powerless to prosecute people for these drugs until after they had been marketed successfully, laws were passed to give the DEA power to emergency schedule chemicals for a year, with an optional 6-month extension, while gathering evidence to justify permanent scheduling, as well as the analogue laws mentioned previously. Emergency-scheduling power was used for the first time for MDMA. In this case, the DEA scheduled MDMA as a Schedule I drug and retained this classification after review, even though their own judge ruled that MDMA should be classified Schedule III on the basis of its demonstrated uses in medicine. The emergency scheduling power has subsequently been used for a variety of other drugs including 2C-B, AMT, and BZP.
Sources: en.wikipedia.org
== Causes == While the mechanism of the disease has yet to be fully elucidated, the leading hypothesis is that AAV (ANCA Associated Vasculitis) develops in patients with a genetic predisposition when an unknown cause triggers the production of p-ANCA. These antibodies will circulate at low levels until an environmental trigger—such as infection, malignancy, or drug therapy, causes the upregulation of neutrophils. The neutrophils bind to p-ANCAs and subsequently release inflammatory cytokines, reactive oxygen species and lytic enzymes that cause endothelial injury resulting to inflammation and necrosis of the small vessels. The damage that is caused in the kidneys is specifically called necrotizing and crescentic glomerulonephritis.
=== Pharmacokinetics === Loxapine is metabolized to amoxapine, as well as its 8-hydroxy metabolite (8-hydroxyloxapine). Amoxapine is further metabolized to its 8-hydroxy metabolite (8-hydroxyamoxapine), which is also found in the blood of people taking loxapine. At steady-state after taking loxapine by mouth, the relative amounts of loxapine and its metabolites in the blood is as follows: 8-hydroxyloxapine > 8-hydroxyamoxapine > loxapine. The pharmacokinetics of loxapine change depending on how it is given. Intramuscular injections of loxapine lead to higher blood levels and area under the curve of loxapine than when it is taken by mouth.
Re-lactation is the process of restarting breastfeeding. In developing countries, mothers may restart breastfeeding after a weaning as part of an oral rehydration treatment for diarrhea. In developed countries, re-lactation is common after early medical problems are resolved, or because a mother changes her mind about breastfeeding. Re-lactation is most easily accomplished with a newborn or with a baby that was previously breastfeeding; if the baby was initially bottle-fed, the baby may refuse to suckle. If the mother has recently stopped breastfeeding, chances are higher that the milk supply will return and be adequate. Although some mothers successfully re-lactate after months-long interruptions, success is higher for shorter interruptions. Techniques to promote lactation include frequent attempts to breastfeed, extensive skin-to-skin contact with the baby, and frequent, long pumping sessions. Suckling may be encouraged with a tube filled with infant formula, so that the baby associates suckling at the breast with food. A dropper or syringe without the needle may be used to place milk onto the breast while the baby suckles. The mother should allow the infant to suckle at least ten times during 24 hours, and more times if the baby is interested. These times can include every two hours, whenever the baby seems interested, longer at each breast, and when the baby is sleepy, when they might suckle more readily. In keeping with increasing contact between mother and child, including increasing skin-to-skin contact, grandmothers should pull back and help in other ways.
Perfluorooctanoic acid (PFOA; conjugate base perfluorooctanoate; also known colloquially as C8, from its chemical formula C8HF15O2) is a perfluorinated carboxylic acid produced and used worldwide as an industrial surfactant in chemical processes and as a chemical precursor. PFOA is considered a surfactant, or fluorosurfactant, due to its chemical structure, which consists of a perfluorinated, n-heptyl "tail group" and a carboxylic acid "head group". The head group can be described as hydrophilic while the fluorocarbon tail is both hydrophobic and lipophobic. The International Agency for Research on Cancer (IARC) has classified PFOA as carcinogenic to humans. PFOA is one of many synthetic organofluorine compounds collectively known as per- and polyfluoroalkyl substances (PFASs). Many PFAS such as PFOS, PFOA are a concern because they do not break down via natural processes and are commonly described as persistent organic pollutants or "forever chemicals". They can also move through soils and contaminate drinking water sources and can build up (bioaccumulate) in fish and wildlife. Residues have been detected in humans and wildlife. PFOA is used in several industrial applications, including carpeting, upholstery, apparel, floor wax, textiles, fire fighting foam and sealants. PFOA serves as a surfactant in the emulsion polymerization of fluoropolymers and as a chemical precursor for the synthesis of perfluoroalkyl-substituted compounds, polymers, and polymeric materials. PFOA has been manufactured since the 1940s in industrial quantities.
Sources: en.wikipedia.org
No. It is a laboratory-synthesized analog built on a fragment of the natural hormone. The natural peptide is shorter-lived and lacks the stabilizing substitutions found in the synthetic version.
DAC stands for drug affinity complex, a chemical group that binds the peptide to serum albumin. The binding slows clearance and lengthens the time the molecule stays in plasma compared with the unmodified analog.
Because two distinct molecules are discussed under one informal label. The albumin-binding version clears over several days, while the form without that group clears within roughly half an hour. Mixing results from both creates inconsistent figures.
The names are often used interchangeably in casual writing, but they are not strictly identical. Modified GRF(1-29) refers to the unconjugated analogue carrying only the four substitutions. The version sold as CJC-1295 with DAC includes the albumin binding linker and clears much more slowly.