A practical reference on RP-HPLC: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2025-12-08. Anything still debated is marked as such rather than presented as settled.
Identity and purity are normally confirmed by reversed-phase high-performance liquid chromatography and mass spectrometry. The expected mass for the acetylated 28-residue peptide is close to 3108 daltons, and a mass shift indicates a modification or truncation. Peptide mapping after enzymatic digestion can resolve sequence-level questions. Counter-ion content, water content, and residual solvents are separate quality attributes that a certificate of analysis may or may not report. Aggregation is monitored by size-exclusion chromatography when relevant.
Thymosin alpha-1 is supplied as a lyophilized powder in most research settings. The solid dissolves readily in water and in common aqueous buffers, and it is typically reconstituted shortly before use. Solutions are clear and colourless at ordinary working concentrations. Because the peptide is hygroscopic, weighing and reconstitution are usually performed with minimal exposure to ambient air. Aliquots are prepared to avoid repeated freeze-thaw cycles, and working solutions are kept cold.
Long-term storage is generally at minus twenty degrees Celsius or colder, preferably desiccated and protected from light. Lyophilized material is more stable than reconstituted solution, which degrades faster at room temperature. Stability depends on pH, ionic strength, and the presence of oxidising agents. Published stability data for the peptide are limited, so storage claims in catalogues should be treated as general guidance rather than measured guarantees. Freeze-thaw cycles are kept to a minimum.
The molecule consists of 28 amino acid residues with an acetyl group attached to the N-terminal serine. Its sequence is acidic overall, with several glutamic and aspartic acid residues distributed along the chain and no cysteine, so disulfide bridges do not form. The peptide carries a net negative charge at physiological pH. Because the N-terminus is blocked, the intact molecule resists degradation by many aminopeptidases, which contributes to its stability in biological fluids.
The peptide is generated in cells by cleavage of prothymosin alpha, a larger acidic protein encoded by the PTMA gene. Prothymosin alpha is expressed in many tissues, not only in the thymus, and its functions include nuclear roles in chromatin-related processes. The 28-residue fragment corresponds to the N-terminal portion of that precursor. How the cleavage occurs and how the fragment's concentration is regulated remain open questions; circulating amounts are small and difficult to measure reliably with routine assays.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Lyophilized form |
| Solubility | Soluble in water | Also soluble in aqueous buffers |
| Storage temperature | -20 °C or below | Desiccated, protected from light |
| Typical analytical method | RP-HPLC with mass spectrometry | Purity and identity |
| Common synonyms | Thymalfasin, T alpha 1 | Sequence identical to natural fragment |
Lyophilized thymosin alpha 1 is typically stored refrigerated at 2 to 8 degrees Celsius and kept away from light. Reconstituted solutions are less stable and are usually used promptly after preparation. Repeated freeze-thaw cycles are avoided because they can promote aggregation and loss of activity. The peptide adsorbs to some plastic and glass surfaces, so a carrier protein is often added to dilute working solutions. Manufacturer instructions and published protocols both govern handling.
Identity and purity testing for thymosin alpha 1 relies mainly on reversed-phase high-performance liquid chromatography and mass spectrometry. Chromatography separates the parent peptide from truncated or modified variants, while mass spectrometry confirms the expected molecular mass. Amino acid analysis and peptide mapping provide additional sequence confirmation. Counterion content, water content, and residual solvents are measured separately as part of specification testing. No single method captures every attribute, so laboratories combine several techniques.
胸腺素α1（thymosin alpha 1，Tα1）是一种由28个氨基酸组成的酸性肽，N端被乙酰化，分子量约为3108道尔顿。该肽最早从牛胸腺组织提取物中分离，属于胸腺素组分5的一个成分。其序列在不同哺乳动物中高度保守，提示其具有基本的生物学功能。名称中的“α1”指其在电泳中的迁移位置，并非表示亚型编号。它既存在于胸腺，也存在于脾脏和淋巴结等免疫组织。
20世纪70年代，研究者从胸腺提取物中纯化出多种小肽，Tα1是其中被较早表征的一种。最初的制备依赖组织匀浆和层析步骤，产量低且成分复杂。随着固相肽合成技术成熟，实验室和工业界能够生产与天然序列一致的合成版本。合成肽的纯度可达95%以上，并可通过反相高效液相色谱和质谱进行鉴定。这一转变使研究不再依赖动物胸腺来源。
市售的胸腺素α1通常以冻干粉形式提供，溶解后用于注射。其氨基酸组成包括多个酸性残基，因此在中性pH下带负电荷。该肽可溶于水和生理盐水，但在有机溶剂中溶解度有限。储存条件通常为冻干状态下负20摄氏度，溶解后需冷藏并避免反复冻融。常见的同义词包括胸腺肽α1、thymalfasin和Tα1。
== Applications == Bayesian Inference has extensively been used by molecular phylogeneticists for a wide number of applications. Some of these include: Inference of phylogenies. Inference and evaluation of uncertainty of phylogenies. Inference of ancestral character state evolution. Inference of ancestral areas. Molecular dating analysis. Model dynamics of species diversification and extinction Elucidate patterns in pathogens dispersal. Inference of phenotypic trait evolution.
Cartalax (Ala-Glu-Asp, T-31, AED) is a tripeptide derivative developed in Russia. It has anti-aging effects in vitro and in animal models, and has been sold in Russian-speaking countries as well as more broadly over the internet as a supposed treatment for conditions such as arthritis, though only limited studies in humans have been published.
== Secondary ion mass spectrometry == Secondary ion mass spectrometry (SIMS) is a method very similar to FAB in that a beam of particles is fired against the surface of a sample in order to cause sputtering, in which the molecules of the sample ionize and leave the surface, thus allowing for the ions or the sample to be analyzed. The primary difference is that in SIMS, an ion beam is fired against the surface, but in FAB, an atom beam is fired against the surface. The other primary difference, of more interest to this page, is that, unlike FAB, SIMS is typically performed on a solid sample with little sample preparation required. The main consideration with SIMS is ensuring that the sample is stable under ultra-high vacuum, or pressures less than 10−8 torr. The nature of the ultra-high vacuum is that it ensures the sample remains constant during analysis as well as ensuring the high energy ion beam strikes the sample. Ultra-high vacuum solves many of the problems that need to be considered during sample preparation. When preparing the sample for analysis, another thing that should be considered is the thickness of the film. Typically, if a thin monolayer can be deposited onto the surface of a noble metal, analysis should be successful. If the film thickness is too large, which is common in real world analysis, the problem can be solved by methods such as depositing a perforated silver foil over a nickel grid onto the film surface. This yields similar results to thin films deposited directly onto a noble metal.
== Conjugation == To be virulent, the bacterium contains a tumour-inducing plasmid (Ti plasmid or pTi) 200 kbp long, which contains the T-DNA and all the genes necessary to transfer it to the plant cell. Many strains of A. tumefaciens do not contain a pTi. Since the Ti plasmid is essential to cause disease, prepenetration events in the rhizosphere occur to promote bacterial conjugation - exchange of plasmids amongst bacteria. In the presence of opines, A. tumefaciens produces a diffusible conjugation signal called N-(3-oxo-octanoyl)-L-homoserine lactone (3OC8HSL) or the Agrobacterium autoinducer. This activates the transcription factor TraR, positively regulating the transcription of genes required for conjugation.
Sources: en.wikipedia.org
Specifically, it binds to microtubule-associated proteins and/or to tubulin and produces depolymerization of microtubules (Kd = 10–20 μM for estramustine), resulting in the arrest of cell division in the G2/M phase (specifically metaphase). EMP was originally thought to mediate its cytostatic effects as a prodrug of normustine, a nitrogen mustard, and hence was thought to be an alkylating antineoplastic agent. However, subsequent research has found that EMP is devoid of alkylating actions, and that the influence of EMP on microtubules is mediated by intact estramustine and estromustine, with normustine or estradiol alone having only minor or negligible effects. As such, the unique properties of the estramustine and estromustine structures, containing a carbamate-ester bond, appear to be responsible for the cytostatic effects of EMP. In addition to its antimitotic actions, EMP has also been found to produce other cytostatic effects, including induction of apoptosis, interference with DNA synthesis, nuclear matrix interaction, cell membrane alterations, induction of reactive oxygen species (free oxygen radicals), and possibly additional mechanisms. EMP has been found to have a radiosensitizing effect in prostate cancer and glioma cells, improving sensitivity to radiation therapy as well. The cytostatic metabolites of EMP are accumulated in tissues in a selective manner, for instance in prostate cancer cells.
== Applications == Immunoliposome applications use its ability to act as a drug delivery system and release specific drug components to target cells. This mechanism can be specifically highlighted in cancer cell targeting and through nutrient delivery systems.
The atomic structure models obtained by X-ray crystallography and biomolecular NMR spectroscopy can be docked into the much larger structures of biomolecular complexes obtained by lower resolution techniques like electron microscopy, electron tomography, and small-angle X-ray scattering.
Sources: en.wikipedia.org
Hirschey, Matthew D.; Shimazu, Tadahiro; Goetzman, Eric; Jing, Enxuan; Schwer, Bjoern; Lombard, David B.; Grueter, Carrie A.; Harris, Charles; Biddinger, Sudha (2010-03-04). "SIRT3 regulates mitochondrial fatty-acid oxidation by reversible enzyme deacetylation". Nature. 464 (7285): 121–125. Bibcode:2010Natur.464..121H. doi:10.1038/nature08778. ISSN 1476-4687. PMC 2841477. PMID 20203611.
=== Golgi tendon organs === Houk and Simon provided one of the first mathematical models of a Golgi tendon organ receptor, modeling the firing rate of the receptor as a function of the muscle tension force. Just as for muscle spindles, they find that, as the receptors respond linearly to sine waves of different frequencies and has little variance in response over time to the same stimulus, Golgi tendon organ receptors may be modeled as linear time-invariant systems. Specifically, they find that the firing rate of a Golgi tendon organ receptor may be modeled as a sum of 3 decaying exponentials:
A large number of enzymes cleave SAM reductively to produce radicals: 5′-deoxyadenosyl 5′-radical, methyl radical, and others. These enzymes are called radical SAMs. They all feature iron-sulfur cluster at their active sites. Most enzymes with this capability share a region of sequence homology that includes the motif CxxxCxxC or a close variant. This sequence provides three cysteinyl thiolate ligands that bind to three of the four metals in the 4Fe-4S cluster. The fourth Fe binds the SAM. The radical intermediates generated by these enzymes perform a wide variety of unusual chemical reactions. Examples of radical SAM enzymes include spore photoproduct lyase, activates of pyruvate formate lyase and anaerobic sulfatases, lysine 2,3-aminomutase, and various enzymes of cofactor biosynthesis, peptide modification, metalloprotein cluster formation, tRNA modification, lipid metabolism, etc. Some radical SAM enzymes use a second SAM as a methyl donor. Radical SAM enzymes are much more abundant in anaerobic bacteria than in aerobic organisms. They can be found in all domains of life and are largely unexplored. A recent bioinformatics study concluded that this family of enzymes includes at least 114,000 sequences including 65 unique reactions. Deficiencies in radical SAM enzymes have been associated with a variety of diseases including congenital heart disease, amyotrophic lateral sclerosis, and increased viral susceptibility.
Sources: en.wikipedia.org
Lyophilized powder is normally kept at minus twenty degrees Celsius or below, in a sealed container, desiccated and away from light. Reconstituted solutions are less stable and are usually refrigerated and used quickly. Repeated temperature cycling should be avoided.
Mass spectrometry gives the molecular mass, which is compared with the calculated value. Reversed-phase liquid chromatography shows purity and the presence of related impurities. Peptide mapping can verify the amino acid sequence when a higher level of detail is needed.
It reports the tests the supplier performed, which may vary between laboratories and lots. Methods and acceptance criteria are not standardised across suppliers. Buyers often request the actual chromatograms and spectra rather than a summary statement.
Thymosin fraction 5 is a mixture of many peptides obtained from thymus tissue, while thymosin alpha 1 is a single defined 28-residue molecule. The two names appear together in older literature because the purified peptide was first obtained from that mixture.