This is a working overview of HPLC, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2025-12-18. Anything still debated is marked as such rather than presented as settled.
Temperature logs and cold-chain documentation help identify excursions that may compromise a batch. Automated freezers, desiccant packs, and sealed containers limit moisture and frost accumulation. Aliquoting small portions before freezing reduces the number of times the main stock changes temperature. Labels should include peptide name, lot, concentration if known, solvent, and date prepared. Periodic analytical verification by high-performance liquid chromatography or mass spectrometry can detect degradation, truncation, or sequence errors that visual inspection cannot reveal.
Practical handling begins with an inventory record that links each vial to a lot number, synthesis date, and purity certificate. Before opening a container, allow it to equilibrate to room temperature to prevent condensation on the powder. Weighing or transferring should occur in a low-humidity environment using tools that minimize static and adsorption. Hygroscopic peptides may gain water quickly, changing mass and concentration estimates. Recording the container's initial mass and any visible changes supports later reconciliation of material.
Reconstitution introduces additional variables: solvent choice, pH, ionic strength, and filtration. Many sequences dissolve readily in water, while hydrophobic ones may need acetonitrile, dimethyl sulfoxide, or a small amount of base. Adding solvent slowly and avoiding vigorous vortexing can reduce foaming and shear-induced aggregation. If the solution appears cloudy, filtration may remove particulates but can also remove aggregated peptide and alter concentration. A clear solution does not by itself confirm correct sequence or purity, so analytical checks remain necessary.
Reconstitution introduces new risks because the peptide contacts solvent, air, and container surfaces. The chosen solvent should match the peptide's solubility profile, and buffer salts, pH, and ionic strength can affect dissolution and subsequent stability. Gentle mixing is preferred over vigorous vortexing, which can create interfaces and shear. If the solution is not clear, the cause may be incomplete dissolution, aggregation, or insoluble counter-ions rather than a simple concentration problem. Filtration is sometimes used, but filters can adsorb peptides and alter measured concentration.
Cold-chain practice relies on documented temperature ranges, calibrated monitoring, and minimized excursions. Shipments may use insulated boxes, phase-change materials, or dry ice, with data loggers to record conditions. Upon receipt, the recipient should verify the logger trace and place items into long-term storage promptly. Repeated warming and cooling during transfers can be more harmful than a single controlled excursion. For solutions, dividing material into single-use aliquots reduces the number of thawing and refreezing events and limits repeated opening of the same container.
Handling begins before a peptide arrives at the bench. Containers should be inspected for cracks, loose caps, or visible moisture, and labels should record identity, lot, and receipt date. Lyophilized material is often allowed to equilibrate to room temperature before opening to prevent condensation on the powder. Gloves and a clean workspace reduce contamination and static-related loss. Once opened, the vial may be purged with inert gas and resealed if the peptide is sensitive to oxygen or humidity. These steps are procedural safeguards rather than guarantees of stability.
| Property | Value | Notes |
|---|---|---|
| Container material | Glass or polypropylene | Glass is relatively inert but can adsorb; polypropylene may leach. |
| Headspace gas | Argon or nitrogen | Inert gas displaces oxygen for oxidation-prone sequences. |
| Equilibration before opening | 20–30 minutes at room temperature | Sealed vial warms gradually to reduce condensation. |
| Typical aliquot size | Small working portions | Limits repeated temperature cycling of the main stock. |
| Documentation fields | Lot, date, solvent, concentration | Supports traceability and degradation monitoring. |
AS9100 Revision A (2001), Model for Quality Assurance in Design, Development, Production, Installation and Servicing During the rewrite of ISO 9001 for the 2000 release, the AS group worked closely with the ISO organization. As the year 2000 revision of ISO 9001 incorporated major organizational and philosophical changes, AS9000 underwent a rewrite as well. It was released as AS9100 to the international aerospace industry at the same time as the new version of ISO 9001. AS9100A was actually two standards referenced in one publication: Section 1 defines an updated QMS model aligned with the updated ISO 9001:2000 publication while Section 2 defines a legacy model aligned with ISO 9001:1994. Organizations that in the year 2001 were operating a QMS based on ISO 9001:1994 were permitted to conform to Section 2 with the expectation that they would then transition their QMS to Section 1.
The first automated insulin delivery system was known as the Biostator. Currently available AID systems fall into three broad classes based on their capabilities. The first systems released can only halt insulin delivery (predictive low glucose suspend) in response to already low or predicted low glucose. Hybrid Closed Loop systems can modulate delivery both up and down, although users still initiate insulin doses (boluses) for meals and typically "announce" or enter meal information. Fully Closed Loops require no manual insulin delivery actions or announcement for meals. A step forward from threshold suspend systems, predictive low glucose suspend (PLGS) systems use a mathematical model to extrapolate predicted future blood sugar levels based on recent past readings from a CGM. This allows the system to reduce or halt insulin delivery prior to a predicted hypoglycemic event.
After dendritic cells have phagocytosed pathogens, they usually migrate to the vast network of lymph vessels and are carried by lymph flow to the draining lymph nodes. Each lymph node is a collection point where APCs can interact with T cells. During the migration, DCs undergo a process of maturation: they lose most of their ability to further engulf pathogens and they mature by changing surface expression of MHC and co-stimulatory molecules, as well as increased production of cytokines. The internalized antigen is digested into smaller peptides containing epitopes, which are then presented to T cells by the MHC. B cells reside in the lymph node. Once their B cell receptor binds to an antigen, they can interact with activated helper T cells, as described above. A dendritic cell that interacts with an already-activated helper T cell can become licensed. This occurs through the interaction of co-stimulatory molecules including B7 and CD40 on the dendritic cell, with CD28 and CD40 ligand on the T cell. Only licensed dendritic cells are able to activate cytotoxic T cells. T cell licensing of dendritic cells is key for activation of cytotoxic T cells for many pathogens, although the extent to which T cell help is needed may vary. In MHC class I and class II molecules, only certain epitopes of an internalized peptide can be presented. These epitopes are termed immunodominant.
Originally, seven such proteins were discovered. Of these, six (BMP2 through BMP7) belong to the Transforming growth factor beta superfamily of proteins. BMP1 is a metalloprotease. Since then, thirteen more BMPs, all of which are in the TGF-beta family, have been discovered, bringing the total to twenty. The current nomenclature only recognizes 13, as many others are put under the growth differentiation factor naming instead.
Sources: en.wikipedia.org
The intense research for development of efficient chiral selectors has resulted in the synthesis of over 1400 CSPs and over 200 CSPs have been commercialized and available in the market. The most commonly employed chiral selectors are categorized and presented in the table. It is surprising to note that In 1980, there was no single chiral stationary phase available in the market for performing chiral chromatography. However, In late 1980s the subject of enantioselective chromatography attracted growing interest, particularly under the drive of the institution of Okamoto in Japan, the teams of Pirkle, and Armstrong in the US, Schurig and König in Germany, Lindner in Austria, and Francotte in Switzerland . The Polysaccharides, amylose and cellulose, form the most abundant chiral polymers on earth. These naturally occurring polysaccharides form basis for an important class of chiral selectors.
In plants, ATP synthase is also present in chloroplasts (CF1FO-ATP synthase). The enzyme is integrated into thylakoid membrane; the CF1-part sticks into stroma, where dark reactions of photosynthesis (also called the light-independent reactions or the Calvin cycle) and ATP synthesis take place. The overall structure and the catalytic mechanism of the chloroplast ATP synthase are almost the same as those of the bacterial enzyme. However, in chloroplasts, the proton motive force is generated not by respiratory electron transport chain but by primary photosynthetic proteins. The synthase has a 40-aa insert in the gamma-subunit to inhibit wasteful activity when dark. CF1FO-ATP synthase is less efficient to its mitochondrial counterpart and exchanges 4—4.67 protons per ATP.
Viscous mucus secreted by glands in the cervix presents a unique environment for drug delivery. Due to its ability to retain substances and slowly release them, it holds potential to be used as a natural, noninvasive drug delivery system. The mucus can act as a reservoir for compounds that destroy pathogens. However, the cervical mucus also presents a barrier to drug delivery as it can be really thick, making it difficult to permeate the mucus barrier. The mechanisms for penetration and bioactivity of the cervical mucus must be understood to utilize the mucus’s potential as a drug delivery system. Due to the changes in viscosity and water content of the mucus during the stages of the menstrual cycle, this poses a particularly complex consideration. For example, the cervical mucus will be thicker when a woman is not ovulating in order to prevent sperm from being able to penetrate the mucus barrier, which also in turn makes in more difficult for penetration of drug delivery systems.
Sources: en.wikipedia.org
In addition to killing bacteria directly they have been demonstrated to have a number of immunomodulatory functions that may be involved in the clearance of infection, including the ability to alter host gene expression, act as chemokines and/or induce chemokine production, inhibiting lipopolysaccharide induced pro-inflammatory cytokine production, promoting wound healing, and modulating the responses of dendritic cells and cells of the adaptive immune response. Animal models indicate that host defense peptides are crucial for both prevention and clearance of infection. It appears as though many peptides initially isolated as and termed "antimicrobial peptides" have been shown to have more significant alternative functions in vivo (e.g. hepcidin). Dusquetide for example is an immunomodulator that acts through p62, a protein involved in toll like receptor based signalling of infection. The peptide is being examined in a Phase III clinical trial by Soligenix (SGNX) to ascertain if it can assist in repair of radiation-induced damage to oral mucosa arising during cancer radiotherapy of the head and neck.
The most common peptide aptamer selection system is the yeast two-hybrid system. Peptide aptamers can also be selected from combinatorial peptide libraries constructed by phage display and other surface display technologies such as mRNA display, ribosome display, bacterial display and yeast display. These experimental procedures are also known as biopanning. All the peptides panned from combinatorial peptide libraries have been stored in the MimoDB database.
Adrenocorticotropic hormone (ACTH; also adrenocorticotropin, corticotropin) is a polypeptide tropic hormone produced by and secreted by the anterior pituitary gland. It is also used as a medication and diagnostic agent. ACTH is an important component of the hypothalamic-pituitary-adrenal axis and is often produced in response to biological stress (along with its precursor corticotropin-releasing hormone from the hypothalamus). Its principal effects are increased production and release of cortisol and androgens by the zona fasciculata and zona reticularis, respectively. ACTH is also related to the circadian rhythm in many organisms. Deficiency of ACTH is an indicator of secondary adrenal insufficiency (suppressed production of ACTH due to an impairment of the pituitary gland or hypothalamus, cf. hypopituitarism) or tertiary adrenal insufficiency (disease of the hypothalamus, with a decrease in the release of corticotropin releasing hormone (CRH)). Conversely, chronically elevated ACTH levels occur in primary adrenal insufficiency (e.g. Addison's disease) when adrenal gland production of cortisol is chronically deficient. In Cushing's disease, a pituitary tumor leads to excessive production of ACTH, which stimulates the adrenal cortex to produce high levels of cortisol.
Christopher A. Lipinski is a medicinal chemist who is working at Pfizer, Inc. He is known for his "rule of five", an algorithm that predicts drug compounds that are likely to have oral activity. By the number of citations, he is the most cited author of some pharmacology journals: Journal of Pharmacological and Toxicological Methods, Advanced Drug Delivery Reviews, Drug Discovery Today: Technologies. Lipinski received his PhD from the University of California, Berkeley in 1968 in physical organic chemistry. The Advanced Drug Delivery Reviews article reporting his "rule of five" is one of the most cited publications in the journal's history. In 2006, he received an honorary law degree from the University of Dundee and he has won various awards, including being the Society for Biomolecular Sciences' winner of the 2006 SBS Achievement Award for Innovation in HTS.
Sources: en.wikipedia.org
Work quickly in a dry environment and keep the container closed when not in use. Equilibrate sealed vials to room temperature before opening to reduce condensation. Record mass changes, as absorbed water can affect concentration calculations.
Liquid storage is generally shorter than dry storage because water enables hydrolysis, oxidation, and microbial growth. If solution storage is necessary, use sterile technique, appropriate pH, and cold temperatures. Aliquot to avoid repeated temperature changes.
Reversed-phase high-performance liquid chromatography is common for purity assessment, while mass spectrometry confirms molecular mass and can reveal modifications. Amino acid analysis or sequencing may be used when sequence information is critical. These methods complement visual inspection and storage records.
Allow the sealed vial to reach room temperature before opening to reduce condensation. Use a suitable solvent and gentle mixing rather than vigorous agitation. Follow the supplier's solubility information when available.