This is a working overview of freeze-thaw, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-04-15. 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.
Two forms circulate under the CJC-1295 name, and they differ by a single appended group. The version without a drug affinity complex carries four substitutions along the peptide chain, including a D-alanine near the amino terminus and replacements at three other positions. These changes block the enzyme dipeptidyl peptidase IV and remove a methionine residue that is prone to oxidation. The modified fragment is frequently labeled MOD GRF 1-29. Naming conventions are inconsistent across informal sources, which is a common source of confusion.
The second form adds a maleimide-bearing linker to the lysine at the carboxyl end. This group reacts with cysteine-34 on circulating serum albumin, forming a covalent bond that keeps the peptide in the bloodstream for far longer. ConjuChem developed the molecule as a way to extend the action of a peptide without frequent administration. The albumin attachment is the defining structural feature of the drug affinity complex version. Whether continuous exposure produces effects distinct from shorter pulses remains an unresolved research question.
| 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 |
The core sequence keeps the receptor-binding region of GHRH while replacing four positions that are vulnerable to dipeptidyl peptidase-4 and other proteases. Substitutions at positions 2, 8, 15, and 27 raise metabolic stability relative to the natural hormone. The N-terminal residues remain essential for activity, so changes there generally lower potency. Molecular weight sits near 3368 daltons for the tetrasubstituted analog without the linker, while the albumin-binding form is heavier because of the added maleimide group.
CJC-1295 is a synthetic peptide modeled on growth hormone-releasing hormone, the hypothalamic signal that prompts the pituitary to release growth hormone. Its sequence corresponds to the first twenty-nine residues of human GHRH, with four substitutions that slow enzymatic breakdown. Early descriptions placed the compound in research on growth hormone deficiency and related conditions, and later literature groups it with the long-acting GHRH analogs. The name appears in both laboratory and popular fitness writing, where it sometimes labels chemically different peptides.
Two related peptides circulate under the CJC-1295 label, and they differ mainly in how long they persist in circulation. The version carrying a drug affinity complex includes a maleimidopropionic acid linker that forms a covalent bond with serum albumin. The other version, usually written as modified GRF(1-29) or tetrasubstituted GRF(1-29), lacks that linker and is cleared quickly. Mixing the two produces inconsistent readings of published half-life values, because the linker rather than the receptor-facing sequence drives most of the difference.
Two related forms circulate in technical discussion under the same family name. The original version carries a drug affinity complex (DAC) that binds covalently to serum albumin after administration, and this linkage substantially extends circulation time. A second form, frequently written as modified GRF(1-29) or CJC-1295 without DAC, lacks that linker and clears much faster. The naming is a frequent source of confusion because the shorthand CJC-1295 can refer to either form depending on the source. Reports sometimes fail to specify which variant was studied.
The peptide backbone includes a D-alanine at position two, which resists cleavage by dipeptidyl peptidase IV, and several other substitutions that reduce degradation. Its molecular weight is roughly 3.4 kDa without the linker and about 3.6 kDa with it. The molecule is water soluble and is normally supplied as a lyophilized powder. Precise sequence and mass values depend on which variant is described, so technical documents usually state the exact form being referenced.
CJC-1295 is a synthetic peptide designed as a long-acting analogue of growth hormone-releasing hormone (GHRH). Its structure derives from the first 29 amino acids of native GHRH, a fragment often called GRF(1-29). Four substitutions were introduced to slow enzymatic breakdown and extend activity relative to the natural sequence. The compound was developed by ConjuChem as part of a broader effort to improve the pharmacokinetic profile of peptide hormones. It is studied in laboratory and clinical research settings rather than appearing as a naturally occurring substance.
Reconstitution is typically performed with sterile water or bacteriostatic water, added slowly against the vial wall. The resulting solution should be clear and colorless; cloudiness or visible particles suggest a problem with the material or the diluent. Once in solution, the peptide is less stable than the dry powder. Refrigerated storage at two to eight degrees Celsius is common for short-term holding, while freezing aliquots is described for longer periods.
Purity is most often assessed by reversed-phase high-performance liquid chromatography, reported as a percentage of total peak area. Identity is confirmed by mass spectrometry, which yields a molecular ion consistent with the expected sequence. Amino acid analysis and peptide mapping provide additional characterization. Reported purity values are method-dependent, so figures from different laboratories are not always directly comparable without details of column, gradient, and detection wavelength.
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.
=== Nutrition === Appropriate nutrition may not always be provided to farmed insects. For instance, adult black soldier flies are generally not fed during rearing due to a common misconception that they cannot eat (which is true for some insects, such as adult silkworm moths). In reality, adult black soldier flies have functional mouthparts and a functional digestive system, can break down both carbohydrates and proteins, will gravitate towards and consume food when provided, have food preferences, and have a prolonged lifespan when fed. Insects may be fasted prior to slaughter (with unknown welfare impacts); this is generally to improve taste/quality of the resulting product or to reduce the likelihood of microbial contamination of the product due to the feed. More evidence is needed to know if fasting periods are necessary for product safety, as some research suggests they may not reduce microbial loads. Farmed insects may be provided with homogenous feeds that lack macronutrient profiles self-selected by the animals; this may play a role in promoting cannibalism in species like the yellow mealworm. Nutritional enrichments, such as dietary diversity, can support brain development in crickets but may not be provided depending on the farm's available feedstock. Poor hydration for some animals may result from an effort to control disease outbreaks/fungal growth in the feed.
Serine hydroxymethyltransferase can decompose serine into formaldehyde and glycine, according to the reaction HOCH2CH(NH2)CO2H → CH2O + H2C(NH2)CO2H. Methylotrophic microbes convert methanol into formaldehyde and energy via methanol dehydrogenase: `CH3OH → CH2O + 2e− + 2H+ Other routes to formaldehyde include oxidative demethylations, semicarbazide-sensitive amine oxidases, dimethylglycine dehydrogenases, lipid peroxidases, P450 oxidases, and N-methyl group demethylases. Formaldehyde is catabolized by alcohol dehydrogenase ADH5 and aldehyde dehydrogenase ALDH2.
In China, Japan, Vietnam and Korea, soybean and soybean products are a standard part of the diet. Tofu (豆腐 dòufu) is thought to have originated in China, along with soy sauce and several varieties of soybean paste used as seasonings. Japanese foods made from soya include miso (味噌), nattō (納豆), kinako (黄粉) and edamame (枝豆), as well as products made with tofu such as atsuage and aburaage. In China, whole dried soybeans are sold in supermarkets and used to cook various dishes, usually after rehydration by soaking in water; they find their use in soup or as a savory dish. In Korean cuisine, soybean sprouts (콩나물 kongnamul) are used in a variety of dishes, and soybeans are the base ingredient in doenjang, cheonggukjang and ganjang. In Vietnam, soybeans are used to make soybean paste (tương) in the North with the most popular products are tương Bần, tương Nam Đàn, tương Cự Đà as a garnish for phở and gỏi cuốn dishes, as well as tofu (đậu hũ or đậu phụ or tàu hũ), soy sauce (nước tương), soy milk (nước đậu in the North or sữa đậu nành in the South), and đậu hũ nước đường (tofu sweet soup).
=== Later years === Macleod returned to Scotland in 1928 to become Regius Professor of Physiology at the University of Aberdeen (in succession to his former teacher, John Alexander MacWilliam who retired in 1927) and later Dean of the University of Aberdeen Medical Faculty. Between 1929 and 1933 he was also a member of the Medical Research Council. Macleod did not continue to work on insulin, but he remained active as a researcher, lecturer and author. His last major contribution was a proof that the central nervous system does have an important role in maintaining carbohydrate metabolism balance, as was his original hypothesis. His theory about conversion of fats into carbohydrates remained unproven, despite his provision of several indirect proofs. He devoted his spare time to golf, motorcycling and painting. He married Mary Watson McWalter (1876–1940) in 1903, but they never had children. He died in 1935 in Aberdeen after several years of suffering from arthritis, despite which he remained active almost until his death. In 1933 he made a lecture tour of the US, and in 1934 he published the 7th edition of his book Physiology and Biochemistry in Modern Medicine.
=== Centrazbat '97 === In September 1997, the 82nd traveled to Kazakhstan and Uzbekistan for CENTRAZBAT '97. Paratroopers from Ft. Bragg, NC flew 8,000 miles on US Air Force C-17s and jumped into an airfield in Shimkent, Kazakhstan. Forty soldiers from the three republics joined 500 paratroopers on the exercise-opening jump. Marine Gen. John Sheehan, then-commander in chief of the Atlantic Command, was first out of the aircraft. The 82nd joined units from Kyrgyzstan, Turkey, and Russia in the two-week-long NATO training mission. Members of the international press and local reporters from WRAL-TV and the Fayetteville Observer were embedded with the 82nd Airborne.
Sources: en.wikipedia.org
Eumelanin (lit. 'true melanin') has two forms linked to 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA). DHI-derived eumelanin is dark brown or black and insoluble, and DHICA -derived eumelanin is lighter and soluble in alkali. Both eumelanins arise from the oxidation of tyrosine in specialized organelles called melanosomes. This reaction is catalyzed by the enzyme tyrosinase. The initial product, dopaquinone can transform into either 5,6-dihydroxyindole (DHI) or 5,6-dihydroxyindole-2-carboxylic acid (DHICA). DHI and DHICA are oxidized and then polymerize to form the two eumelanins. In natural conditions, DHI and DHICA often co-polymerize, resulting in a range of eumelanin polymers. These polymers contribute to the variety of melanin components in human skin and hair, ranging from light yellow/red pheomelanin to light brown DHICA-enriched eumelanin and dark brown or black DHI-enriched eumelanin. These final polymers differ in solubility and color. Analysis of highly pigmented (Fitzpatrick type V and VI) skin finds that DHI-eumelanin comprises the largest portion, approximately 60–70%, followed by DHICA-eumelanin at 25–35%, and pheomelanin only 2–8%. Notably, while an enrichment of DHI-eumelanin occurs in during sun tanning, it is accompanied by a decrease in DHICA-eumelanin and pheomelanin. A small amount of black eumelanin in the absence of other pigments causes grey hair. A small amount of eumelanin in the absence of other pigments causes blond hair. Eumelanin is present in the skin and hair, etc.
The Byzantine Empire distinctively blended Roman political traditions, Greek literary heritage, and Christianity, creating the civilisational framework that laid the foundation for medieval Europe. The Empire preserved European civilisation by acting as a shield against forces from Eurasian Steppe people such as the Avars, Bulgars, Cumans, Huns, Pechenegs, and Turks. The empire's legal codes significantly influenced the civil law traditions of continental Europe, Russia, Latin America, Ethiopia, and even the English-speaking common law countries; and possibly influenced Islamic legal traditions as well. It also preserved and transmitted classical learning and manuscripts, making important contributions to the intellectual revival which fuelled Italian humanism. The Byzantine Empire played a pivotal role in shaping Christianity by supporting early Church fathers and the decisions of Church councils; developing the institution of monasticism; and fostering the Orthodox tradition which continues to define much of Eastern European identity. It was also instrumental in preserving the Greek language and is credited with developing the Glagolitic alphabet, which later evolved into the Cyrillic script and Old Church Slavonic. These innovations provided the first literary language for the Slavs and formed the educational foundation for all Slavic nations.
Thyroid Stimulating Hormone (TSH) (University of Washington Medical Center). September 2011. Method: Access 2 (Beckman Coulter). Thyroid Stimulating Hormone (TSH) (Collaborative Laboratory Services). September 2011. Method: Access 2 (Beckman Coulter). Thyroid Stimulating Hormone (TSH). September 2009. Method: Access 2 (Beckman Coulter). Lab 18 Thyroid Stimulating Hormone. 2001-2002. Method: Microparticle Enzyme Immunoassay. Lab 18 TSH - Thyroid Stimulating Hormone. 1999-2000. Method: Microparticle Enzyme Immunoassay.
==== Chronic pain ==== It is also used in the management of chronic pain. Often, transdermal patches are used. The patches work by slowly releasing fentanyl through the skin into the bloodstream over 48 to 72 hours, allowing for long-lasting pain management. Dosage is based on the size of the patch, since, in general, the transdermal absorption rate is constant at a constant skin temperature. Each patch should be changed every 72 hours. Rate of absorption is dependent on a number of factors. Body temperature, skin type, amount of body fat, and placement of the patch can have major effects. The different delivery systems used by different makers will also affect individual rates of absorption, and route of administration. Under normal circumstances, the patch will reach its full effect within 12 to 24 hours; thus, fentanyl patches are often prescribed with a fast-acting opioid (such as morphine or oxycodone) to handle breakthrough pain. It is unclear if fentanyl gives long-term pain relief to people with neuropathic pain.
Site-directed mutagenesis of O-GlcNAc-modified serine or threonine residues to alanine may be used to evaluate the function of O-GlcNAc at specific residues. As alanine's side chain is a methyl group and is thus not able to act as an O-GlcNAc site, this mutation effectively permanently removes O-GlcNAc at a specific residue. While serine/threonine phosphorylation may be modeled by mutagenesis to aspartate or glutamate, which have negatively charged carboxylate side chains, none of the 20 canonical amino acids sufficiently recapitulate the properties of O-GlcNAc. Mutagenesis to tryptophan has been used to mimic the steric bulk of O-GlcNAc, though tryptophan is much more hydrophobic than O-GlcNAc. Mutagenesis may also perturb other post-translational modifications, e.g., if a serine is alternatively phosphorylated or O-GlcNAcylated, alanine mutagenesis permanently eliminates the possibilities of both phosphorylation and O-GlcNAcylation.
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.
Natural GHRH is degraded quickly by dipeptidyl peptidase-4 and related enzymes, giving it a half-life measured in minutes. CJC-1295 carries substitutions that slow that breakdown, so it stays intact longer. Both act at the same pituitary receptor and produce the same class of signal.