Proteins alkali metal salts

Calibrants are required to calibrate the mass scale of any mass spectrometer, and it is important to find reference compounds that are compatible with a particular ion source. Calibrants commonly used in electron ionization (El) and chemical ionization (Cl), such as perfluorocarbons, are not applicable in the ESI mode. The right calibrants for LC-ESI-MS should (1) not give memory effects (2) not cause source contamination through the introduction of nonvolatile material (3) be applicable in both positive- and negative-ion mode. The main calibrants used or still in use to calibrate ESI-MS can be divided into the following categories polymers, perfluoroalkyl triazines, proteins, alkali metal salt clusters, polyethers, water clusters, and acetate salts. 

Green, J. S. and Jorgenson, J. W., Minimizing adsorption of proteins on fused silica in capillary zone electrophoresis by the addition of alkali metal salts to the buffers, /. Chromatogr., 478, 63, 1989. 

Protactinium, 1131-1215 Proteins denaturation alkali metal salts, 6 Pseudometatungstates, 1034... 

A quite new type of antibiotic and one of the few naturally-occurring boron compounds is boromycin (86). Hydrolytic cleavage of D-valine with the M(7) hydroxides gave caesium and rubidium salts of this antibiotic, and crystal structure analysis established the formula as (XIIT). The rubidium ion is irregularly coordinated by eight oxygen atoms. Experiments with models showed that the cation site would be the natural place for the—NH3+ end of the D-valine residue, and the whole structure raises the possibility that transport of larger alkali metals is related to the N-ends of peptides and proteins. 

In caramelization under alkaline conditions also, three cases should be distinguished, namely, caramelization in the presence of (a) either alkali or carbonates of alkali metals (mainly sodium carbonate), (b) ammonia or ammonium salts, and (c) amino acids, peptides, and proteins. 

Gradient-forming materials which provide the densities required for the separation of subcellular particles include salts of alkali metals (e.g. caesium and rubidium chloride), small neutral hydrophilic organic molecules (e.g. sucrose), hydrophilic macromolecules (e.g. proteins and polysaccharides), and a number of miscellaneous compounds more recently introduced and not included in the above group, such as colloidal silica (e.g. Percoll) and non-ionic iodinated aromatic compounds (e.g. Metrizamide, Nycodenz and Renograffin). 

Phosphoproteins.—Proteins of this class when subjected to the action of pepsin and hydrochloric acid, undergo hydrolysis, and yield proteoses and an acid containing phosphorus, which is called paranucleic acid. This acid is sharply distinguished from the nucleic acids, as neither xanthine bases, pyrimidine derivatives, nor pentoses occur among its dissociation-products. Paranucleic acid has not been obtained in the pure condition, and its decomposition-products are not definitely known. The phosphoproteins are distinctly acid, are insoluble in water, and form soluble salts which contain the alkali metals and ammonium. 

Owing to its compatibility with solution samples, ESI is preferred over other ionization methods in many MS fields. Applications of metal ion adducts have been reported for ESI [55-57]. For example, ESI can be used to produce alkali-metal adducts of antibiotics that do not form abundant [M+H]+ ions. Informative adducts between alkali-metal ions and peptides have been observed under a variety of conditions of electrospray ionization mass spectrometry (ESI-MS). It should be noted, however, that the presence of salt ion adducts cause the signal suppression and interference with the interpretation of the mass spectra, particularly in analytical MS of proteins and other biological molecules. 

Mixtures of a protein (usually myoglobin) and some smaller peptides can be used polyethylene glycols and polypropylene glycols are also widely used for calibration. Anacleto et al. have summarized different options and have proposed protonated water clusters and salt clusters generated by pneumatically assisted electrospray. Water clusters provided a calibration range up to miz 1000 in the SCIEX API III mass spectrometer. Alkali metal halides (sodium iodide) allow calibration on cluster ions Na (Nal) or I (NaI) up to at least m/z 2000, the fiiU mass range of this instrument. 

Protein denaturation can be due to physical reasons, e.g. heat (Figure 8.42), cold, mechanical forces, radiation or influence of chemical factors (acids, alkali, salts, solvents, surfactants, oxidants, heavy metals, chelating agents). 

Humic adds. Chocolate brown, dust-like powder, poorly soluble in water with a large increase in volume, soluble in aqueous alkalis to give brown solutions, and in cone, nitric acid to give red solutions. H. forms a heteropolycondensate with Mr of 2000-500000 (mostly 20000-50000), mp. >300°C. They consist of a polycyclic core and loosely bound polysaccharides, proteins, simple phenols, and chelated metal ions which are linked to the core through carboxyl and carbonyl groups . The latter usually have aromatic character. The H. are strongly acidic (hydroxy- and polyhydroxycarboxylic acids) and mostly occur as salts. For analysis, see Lit.. ... 

By treating proteids with alkalis or adds, decomposition products are obtained that are closely related to the proteins. They are called alkali albuminates and add albimiins, or syntonins. Paal obtained his protalbinic and lysalbinic acids by treatment of proteids with alkalis. The former are closely allied to alkali albuminates and the latter to the albumoses. The alkali albuminates are excellent protective colloids so are protalbinic and lysalbinic acids. The gold number of the sodium salt of protalbinic acid is 0.03 to 0.08 while that of lysalbinic acid is 0.02 to 0.06. Concerning their use in the preparation of colloidal metals see Chapter V. 

In order to study the nucleic acids by physicochemical or enzymological methods, they must be isolated and purified from other cell constituents. As their name indicates, they are acidic in character (one negative charge per nucleotide residue) and are neutralized by basic proteins (protamines, histones), polyamines (spermine, spermidine, etc.), or metallic cations (alkalis, earth alkalis). Nucleic acids are irreversibly denatured, if all their basic components are removed. For this reason, extractions are usually carried out in salt solutions buffered at pH 7. 

The influence of added salts of the alkalies and magnesium upon the precipitation of proteins by heavy metals varies with the concentration of salt employed (Pauli). At low concentrations (0.005 M) the salts inhibit precipitation in the order ... 

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