freeze-thaw raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2026-01-27 and is reviewed periodically as new material appears.
Reconstitution involves adding a solvent to dry peptide, often water or a buffered solution. The chosen liquid should match the peptide's solubility and intended assay, and it should be free of contaminants. Gentle mixing or inversion reduces foaming and shear, which can damage some peptides. If the peptide does not dissolve readily, adjusting pH or using a small amount of organic co-solvent may help. The final solution is typically clarified before use in analytical or laboratory procedures.
After reconstitution, solutions are usually divided into single-use aliquots to limit repeated handling. Each aliquot is stored at a temperature appropriate for the peptide, with -20 °C or -80 °C common for longer-term laboratory storage. Freeze-thaw cycles are minimized because they can cause aggregation, precipitation, or loss of activity. Temperature monitoring and documented storage conditions support reproducibility across experiments. When a peptide is removed from storage, it is typically allowed to equilibrate before opening to reduce condensation.
Receiving a peptide begins with recording its identity, lot number, quantity, and arrival condition. Dry material is often kept in sealed containers with desiccant and an inert headspace to limit moisture and oxygen. Containers should be compatible with the peptide and solvent; some peptides adsorb to certain plastics or glass. Labels should include date, concentration, solvent, and storage location. A centralized inventory with temperature logs helps prevent loss and mix-ups.
After reconstitution, solutions are divided into single-use aliquots and stored at -80°C. Labels include peptide name, concentration, buffer composition, date, and lot number. Freeze-thaw cycles are minimized by thawing only the needed aliquot on ice or at room temperature. Some peptides benefit from the addition of a carrier protein, such as bovine serum albumin, or a cryoprotectant like glycerol to reduce adsorption to plastic. Glass vials with low-binding surfaces are preferred for dilute solutions. Shipping of frozen aliquots uses dry ice and insulated containers to maintain the cold chain.
Receiving a peptide shipment requires immediate inspection of the packaging and temperature indicators. Any deviation from the specified cold chain should be documented and investigated. Upon arrival, solid peptides are generally kept at -20°C, whereas liquid formulations are stored at -80°C. Vials should be kept upright and protected from light. Repeated warming and cooling of the entire container is avoided by preparing smaller working aliquots. A log of lot numbers, receipt dates, and storage locations supports traceability and quality control.
Reconstitution is a critical handling step. The appropriate solvent—often sterile water, phosphate-buffered saline, or a water-acetonitrile mixture—is chosen based on peptide solubility. Adding solvent gently down the vial wall and swirling, rather than vortexing, reduces foaming and shear stress. The resulting solution should be clear; visible particles indicate incomplete dissolution or contamination. Concentration is recorded accurately because it affects subsequent use. If the peptide is not fully soluble, a small amount of organic solvent or a different buffer may be required, but this changes the final composition.
| Property | Value | Notes |
|---|---|---|
| Container material | Glass or inert plastic | Compatibility depends on peptide and solvent |
| Headspace gas | Nitrogen or argon | Used to limit oxygen exposure |
| Common reconstitution solvent | Water or buffered aqueous solution | Organic co-solvents may be needed for hydrophobic peptides |
| Freeze-thaw stability | Varies by peptide | Aliquoting reduces repeated cycles |
| Documentation | Lot, date, concentration, storage location | Supports traceability and reproducibility |
=== Etymology === The word tomato comes from the Spanish tomate, which in turn comes from the Nahuatl word tomatl [ˈtomat͡ɬ] . The specific name lycopersicum, meaning 'wolf peach', originated with Galen, who used it to denote a plant that has never been identified. Luigi Anguillara speculated in the 16th century that Galen's lycopersicum might be the tomato, and despite the impossibility of this identification, lycopersicum entered scientific use as a name for the fruit.
In what some have called the First Cold War, from Britain's intervention in the Russian Civil War in 1918 to its uneasy alliance with the Soviet Union against the Axis powers in 1941, British distrust of the revolutionary and regicidal Bolsheviks resulted in domestic, foreign, and colonial policies aimed at resisting the spread of communism. This conflict after 1945 took on new battlefields, new weapons, new players, and a greater intensity, but it was still fundamentally a conflict against Soviet imperialism (real and imagined). The idea of long-term continuity is a minority scholarly view that has been challenged. Frank Ninkovich writes:
== History == Evidence that the small intestine controls the release of bile was uncovered as early as 1856, when French physiologist Claude Bernard showed that when dilute acetic acid was applied to the orifice of the bile duct, the duct released bile into the duodenum. In 1903, the French physiologist Émile Wertheimer showed that this reflex was not mediated by the nervous system. In 1904, the French physiologist Charles Fleig showed that the discharge of bile was mediated by a substance that was conveyed by the blood. There remained the possibility that the increased flow of bile in response to the presence of acid in the duodenum might be due to secretin, which had been discovered in 1902. The problem was finally resolved in 1928 by Andrew Conway Ivy and his colleague Eric Oldberg of the Northwestern University Medical School, who found a new hormone that caused contraction of the gall bladder and that they called "cholecystokinin". In 1943, Alan A. Harper and Henry S. Raper of the University of Manchester discovered a hormone that stimulated pancreatic enzyme secretion and that they named "pancreozymin"; however, pancreozymin was subsequently found to be cholecystokinin. Swedish biochemists Johannes Erik Jorpes and Viktor Mutt undertook the monumental task of isolating and purifying porcine cholecystokinin and then determining its amino acid sequence. They finally presented porcine cholecystokinin's amino acid sequence in 1968.
curves to cross over at different points, as illustrated. In this case, morph B crystals are energetically favored when small, but for a large enough crystal, morph A is energetically favored. This means that during crystallization, morph B tends to appear first, which then may grow without bound—that is, morph B is kinetically favored. However, it is a metastable crystal. If a seed crystal of morph A above the crossover radius
For elements that have one naturally occurring isotope (mononuclidic elements) or one dominant isotope, the difference between the atomic mass of the most common isotope, and the (standard) relative atomic mass or (standard) atomic weight will be nil, or small enough to not effect most calculations. For elements with more than one isotope in significant quantities, the mass of individual atoms will be different from an average across all the isotopes. For elements that have more than one common isotope, the numerical difference in relative atomic mass (atomic weight) from even the most common relative isotopic mass, can be half a mass unit or more (e.g. see the case of chlorine where atomic weight and standard atomic weight are about 35.45). The atomic mass (relative isotopic mass) of an uncommon isotope can differ from the relative atomic mass, atomic weight, or standard atomic weight, by several mass units. Relative isotopic masses are always close to whole-number values, but never (except in the case of carbon-12) exactly a whole number, for two reasons:
Sources: en.wikipedia.org
=== Topical application === Topically applied sodium hyaluronate can facilitate the absorption of biomacromolecules, i.e. pharmaceuticals, and function like a nanocarrier. Its effects on skin depend on the hyaluronate formulation and skin health: In barrier-deficient skin it restricted the delivery of biomacromolecules to the stratum corneum and viable epidermis. In normal skin, low-molecular weight hyaluronate (5 kDa) enhanced penetration into the epidermis. Transepidermal water loss increased by 55.5% with low-molecular weight, and was reduced by 28% with crosslinked resilient, and by 16% with HMW. Its efficacy against wrinkles has not been tested in clinical trials. Dry, scaly skin, such as that caused by atopic dermatitis, may be treated with lotion or another skin product containing sodium hyaluronate as its active ingredient. After instillation into the lung, higher molecular weight hyaluronate appears to persist longer in the lung but if > 215 kD there was poor lung penetration and mucociliary clearance. Hyaluronate could allow access to lymph nodes draining the pulmonary bed.
== Contraindications == Suvorexant is contraindicated in people with narcolepsy as it may worsen their symptoms. This is its only absolute contraindication. Suvorexant has not been studied in people with severe hepatic impairment and is not recommended in these individuals due to the likelihood of increased suvorexant exposure. On the other hand, suvorexant may be used in people with mild-to-moderate hepatic impairment as well as renal impairment of any severity and no dose adjustment is necessary in these situations. Concomitant use of suvorexant with strong CYP3A4 inhibitors is not recommended due to potential for increased suvorexant exposure while concomitant use of suvorexant with strong CYP3A4 inducers may result in loss of suvorexant exposure and effectiveness. Suvorexant should be used carefully in people with a history of drug misuse or alcoholism due to its drug-liking effects and possible misuse potential at doses higher than those approved for therapeutic use. Similarly, suvorexant should be used carefully in people with a history of depression or suicidality as it may rarely increase suicidal ideation. The medication is indicated for use in adults and the elderly but has not been studied in children and adolescents and hence is not recommended for these individuals. Suvorexant has shown teratogenic effects in animals such as decreased body weight at doses much higher than the equivalents of those approved for therapeutic use in humans.
=== Territorial disputes, internal conflicts, and armed conflicts === A 2017 study found that autocratic leaders whose states were involved in international rivalries over disputed territory were more likely to be overthrown in a coup. The authors of the study provide the following logic for why this is:Autocratic incumbents invested in spatial rivalries need to strengthen the military in order to compete with a foreign adversary. The imperative of developing a strong army puts dictators in a paradoxical situation: to compete with a rival state, they must empower the very agency—the military—that is most likely to threaten their own survival in office.However, two 2016 studies found that leaders who were involved in militarized confrontations and conflicts were less likely to face a coup. A 2019 study found that states that had recently signed civil war peace agreements were much more likely to experience coups, in particular when those agreements contained provisions that jeopardized the interests of the military.
=== Phase 2 === 18F PI-2620 ([18F]PI-2620; PI-2620) – positron-emission tomography (PET) enhancer – diagnosis [16] AB-1005 (AAV2-GDNF; AMT-140; adeno-associated-virus-GDNF therapy) – gene transference and glial cell line-derived neurotrophic factor (GDNF) expression stimulant [17] Affitope PD01 (ACI-7104; ACI-7104.056; Affitope-PD01A; PD-01; PD-01A) – peptide vaccine against α-synuclein [18] Altropane 123I (dopamine transporter (DAT) imaging radiopharmaceutical) – dopamine reuptake inhibitor (DRI) and single-photon emission-computed tomography (SPECT) enhancer – diagnosis [19] Apomorphine inhalation (AZ-009; Staccato® Apomorphine) – non-selective dopamine receptor agonist and other actions [20] Apomorphine intranasal (AL-101) – non-selective dopamine receptor agonist and other actions [21] Aprepitant/pramipexole (ALTO-208; CTC-413) – combination of aprepitant (neurokinin NK1 receptor antagonist) and pramipexole (dopamine D2-like receptor agonist) [22] Bezisterim (17α-ethynyl-5-androstene-3β,7β,17β-triol; HE-3286; NE-3107; Triolex) – undefined mechanism of action (synthetic androstenetriol analogue and anti-inflammatory) [23] Blarcamesine (AE-37; ANA001; ANAVEX 2-73) – sigma σ1 receptor agonist, muscarinic acetylcholine M1 receptor agonist, and ionotropic glutamate NMDA receptor agonist [24] Buspirone/zolmitriptan (AV-2860; JM-010) – combination of buspirone (serotonin 5-HT1A receptor agonist and other actions) and zolmitriptan (serotonin 5-HT1B and 5-HT1D receptor agonist) – drug-induced dyskinesia in Parkinson's disease [25] Carbidopa/levodopa (DopaFuse; levodopa/carbidopa continuous release) – combination of carbidopa (aromatic L-amino acid decarboxylase (AAAD) inhibitor) and levodopa (dopamine precursor) [26] Carbidopa/levodopa intranasal (INP-107; POD™ carbidopa/levodopa) – combination of carbidopa (aromatic L-amino acid decarboxylase (AAAD) inhibitor) and levodopa (dopamine precursor) [27] DA-9805 – antioxidant and mitochondrial protein modulator [28] Deferiprone (CGP-37391; CMX-001; CP-020; CP-20; CRMD-001; Ferriprox; Kelfer; L1; Upkanz) – chelating agent [29] EPI-589 ((R)-troloxamide quinone; kinoquinone) – NAD(P)H dehydrogenase (quinone) modulator and antioxidant [30] FNP-150 – undefined mechanism of action [31] Gemfibrozil (FHL-301) – peroxisome proliferator-activated receptor alpha (PPARα) agonist [32] Glovadalen (UCB-0022) – dopamine D1 receptor positive allosteric modulator [33] GRF-6021 (AKST-6021) – plasma protein fraction and neurogenesis stimulant [34] ION-859 (BIIB-094; ION859; IONIS-BIIB7Rx) – leucine-rich repeat kinase 2 (LRRK2) inhibitor [35] Lazucirnon (AKST-4290; ALK-429; ALK-4290) – chemokine CCL11 inhibitor [36] Levetiracetam low-dose (AGB-101) – synaptic vesicle glycoprotein 2A (SV2A) modulator [37] Levodopa (TR-012001) – dopamine precursor and indirect non-selective dopamine receptor agonist [38] Levodopa intranasal (INP103; POD™ levodopa) – dopamine precursor and indirect non-selective dopamine receptor agonist [39] Matsupexole (AM006; KDT-3594) – dopamine receptor agonist [40] Minzasolmin (DLX-313; UCB-0599) – α-synuclein misfolding inhibitor [41] Nilotinib (KFRX-01) – Bcr-Abl tyrosine kinase inhibitor and discoidin domain receptor antagonist [42] Pariceract (BIA 28-6156; LTI-291) – β-glucocerebrosidase (GCase) activator [43] Pegsebrenatide (NLY-01; Olaedin; pegylated exenatide; TLY-001) – glucagon-like peptide-1 receptor (GLP1R) agonist [44] Pirepemat (IRL-752) – various actions [45] Pramipexole – dopamine D2, D3, and D4 receptor agonist [46] Prasinezumab (NEOD-002; PRX-002; RG-7935; RO-7046015) – monoclonal antibody against α-synuclein [47] Pridopidine (ACR-16; ASP-2314; FR-310826; Huntexil; Nurzigma; TV-7820) – sigma σ1 receptor agonist and other actions [48] Radotinib (IY-5511; Supect) – Bcr-Abl tyrosine kinase inhibitor and other actions [49] Risvodetinib (Ikt-148009; IkT148009; risvo) – Bcr-Abl tyrosine kinase inhibitor [50] Squalamine (ENT-01; Enterin-01; kenterin) – various actions [51] Tributyrin (glyceryl tributyrate) – butyric acid (butyrate) prodrug and various actions [52] [53] Usnoflast (ZYIL-1) – NLR family pyrin domain containing 3 (NLRP3) inhibitor [54] Vatiquinone (α-tocotrienol quinone; vincerenone; EPI-743 and PTC-743) – coenzyme Q10 analogue, antioxidant, oxidoreductase inhibitor, 15-lipoxygenase (15-LOX/ALOX15) inhibitor [55] Vodobatinib (K-0706; SCO-088; SUN-K706; SUN-K0706) – Bcr-Abl tyrosine kinase inhibitor [56] VTX-3232 – NLR family pyrin domain containing 3 (NLRP3) inhibitor [57] Vutiglabridin (HSG-4112) – paraoxonase 2 (PON2) agonist and glabridin analogue [58] WID-2101 – undefined mechanism of action [59] XJN-010 – undefined mechanism of action [60]
== Anopheles gambiae in the strict sense == An. gambiae sensu stricto (s.s.) has been discovered to be currently in a state of diverging into two different species—the Mopti (M) and Savannah (S) strains—though as of 2007, the two strains are still considered to be a single species. A mechanism of species recognition using the sound emitted by the wings and identified by Johnston's organ was proposed in 2010, however this mechanism has never been confirmed since, and the overall mechanism theory through "harmonic convergence" has been challenged.
Sources: en.wikipedia.org
Dry peptides are generally kept in sealed, desiccated containers at low temperature, often -20 °C or colder. Protection from light, moisture, and oxygen helps slow degradation. The exact condition depends on the peptide sequence and supplier guidance.
Aliquoting divides a solution into smaller portions so that each portion is handled once. This reduces repeated freeze-thaw cycles and limits contamination risk. It also makes it easier to track usage and maintain consistent test conditions.
Refreezing is possible for some peptides but can promote aggregation or precipitation. The effect depends on the peptide, solvent, concentration, and freezing rate. Many laboratory protocols therefore recommend single-use aliquots instead of repeated refreezing.
Common solvents include sterile water, phosphate-buffered saline, and water-acetonitrile mixtures. The choice depends on the peptide's solubility profile and the buffer compatibility for the intended application. Manufacturers often provide a recommended solvent on the product information sheet.