Showing papers on "Reagent published in 1970"

Ferrozine---a new spectrophotometric reagent for iron

Abstract: -N=C&N-, have been known to react as bidentate ligands with certain metal ions such as ferrous, cuprous, and cobaltous, to give colored complex species (1-6). This effect was first noticed with the ferrous ion ( I ) , and since this complex of a given compound is generally of a more intense color than are those with other ions (7), the atomic configuration in question was given the trivial name of the ferroin group. During the last century, hundreds of compounds containing the ferroin group have been synthesized (7), the majority of which demonstrate the ability to form complexes with the ferrous ion. Most of these complexes are only weakly colored, are unstable under normal physical conditions, or are formed over a very narrow pH range. A few of these compounds, however, form stable, intensely colored species with the ferrous ion and are, therefore, suitable for the quantitative determination of iron (8). Examples of compounds which have found acceptance for such use are 1,lOphenanthroline (9), 4,7-diphenyl-l,lO-phenanthroline (IO), 2,2‘-bipyridine (I]), 2,6-bis(2-pyridyl)-pyridine (11). 2,4,6tris(2-pyridyl)-1,3,5-triazine (12), and phenyl 2-pyridyl ketoxime (13, 14). Many of these reagents are the product of difficult and tedious organic syntheses and, hence, are high in cost (14). Although for even the most expensive of these reagents, the cost of a single manual analysis is fairly low, when one considers automated continuous instrumental analysis, a lowcost yet highly sensitive reagent would be desirable, since the cost of maintaining such an analytical instrument with I

A rapid and direct method for the quantitative determination of tryptophan in the intact protein

Abstract: 1. A method is given for the quantitative determination of free tryptophan or tryptophan in the intact protein by treating with ninhydrin in a mixture of formic acid and hydrochloric acid (reagent b), for 10min at 100°C. Glycyltryptophan was used as a standard for the determination of tryptophan in the intact protein. The extinction at 390nm was linear in the range 0.05–0.5μmol for free tryptophan (∈7120) and 0.05–0.30μmol for glycyltryptophan (∈15400). 2. Free tryptophan in the presence of protein may be determined by treating with ninhydrin in a mixture of acetic acid and 0.6m-phosphoric acid (reagent a) for 10min at 100°C, the extinction being linear for tryptophan in the range 0.05–0.9μmol. N-Terminal tryptophan peptides also give the typical yellow product on treatment with reagent a. 3. Tryptophan content of several pure intact proteins when treated with the above method gave values in good agreement with those reported by others. A mean tryptophan content of 11.25 (s.e.m. ±0.08) μmol/100mg of protein was found in rat brain during development from 1 to 82 days after birth.

Reductive stripping process for the recovery of uranium from wet-process phosphoric acid

Abstract: A reductive stripping flow sheet for recovery of uranium from wet-process phosphoric acid is described. Uranium is stripped from a uranium-loaded organic phase by a redox reaction converting the uranyl to uranous ion. The uranous ion is reoxidized to the uranyl oxidation state to form an aqueous feed solution highly concentrated in uranium. Processing of this feed through a second solvent extraction cycle requires far less stripping reagent as compared to a flow sheet which does not include the reductive stripping reaction.

Recent Developments in Chemical Modification and Sequential Degradation of Proteins

Abstract: Publisher Summary This chapter tabulates the reagents of current interest for the chemical modification of proteins according to the functional group modified, so that a biochemist who suspects that residue X is involved in the mechanism of action of his enzyme can quickly survey the major reactions of X. The principal reason for modifying an enzyme chemically is to identify those amino acid residues that function intimately in catalysis. If the effect of such a modification is to be interpreted unambiguously, the reaction should be specific and limited. As a general rule, the more unreactive a reagent is, the more specific it is likely to be because the transition states for slow reactions often resemble the products more than the reactants, and therefore the rates are influenced more by the properties of the products. In contrast, highly reactive reagents tend to be unspecific because the transition states resemble the reactants more than the products—that is, activation energies for many different kinds of reactions are likely to be low.

On the use of tetranitromethane as a nitration reagent. The reaction of phenol side-chains in bovine and porcine trypsinogens and trypsins.

Abstract: Tetranitromethane, a reagent described by Riordan et al. in 1966 has been used for the nitration of tyrosines in bovine and porcine trypsinogen and trypsin. The reagent induces a great number of inter- and intra-molecular side-reactions. In particular, considerable polymerization due to crosslinking can be observed, especially with high concentrations of proteins. Monomers, dimers and polymers of higher degree can be easily separated by Sephadex G-100 chromatography. The existence of polymeric species has also been observed with ribonuclease, lysozyme and the Kunitz pancreatic inhibitor. 5 of the 10 tyrosines are sufficiently exposed at the surface of the trypsinogen molecule to be nitrated easily. The second-order kinetics of the chemical modification have been studied under different conditions and compared to the kinetics of nitration of N-acetyl-l-tyrosine ethyl ester. Nitration increases the bulk of the tyrosine side-chain and decreases the pK- of the phenol function from 10.2–10.3 to 6.9 in trypsinogen. This important modification of the properties of this residue has no effect on the catalytic activity of trypsin toward small synthetic ester or amide substrates but it decreases considerably the tryptic activity toward macromolecular substrates. For example, nitration of trypsin decreases by a factor of 15 the maximal rate of activation of chymotrypsinogen A; no change on Km has been observed.

Device and method for testing potency of biological control reagents

Abstract: Device for testing the potency of a biological control reagent, as in antibiotic susceptibility testing, especially the determination of minimum inhibitory concentration, comprising a strip of a plurality of interconnected plastic cups having a capacity of about 0.3 ml. each. All but two of the cups contain a range of amounts of the control reagent in an essentially dry state which will provide a predetermined range of concentrations when the reagent is redispersed. Contamination of the dry reagent in the cups is prevented by an adherent plastic film or aluminum foil across the openings of the cups. In use, the adherent film or foil is removed, the dry reagent is redispersed to form the required range of concentrations, and all of the cups except one are inoculated with the biological material against which the potency of the control reagent is to be tested. The last cup contains the dispersion medium but not the control reagent nor inoculum, and provides a sterility control. The second last cup contains the dispersion medium and the inoculum, and serves as a growth control. The strip of cups is then resealed, incubated, and the test results are read.

Five-membered rings. II. Inter and intramolecular reactions of simple amines with N-substituted phthalimides. Methylamine as a reagent for removal of a phthaloyl group from nitrogen

Abstract: A reexamination of the literature on inter and intramolecular reactions of amines with N-substituted phthalimides has led to the demonstration that methylamine is a convenient reagent for removal o...

2,3-Diaminonaphthalene as a Spectrophotometric and Fluorometric Reagent for the Determination of Nitrite Ion

Abstract: Spectrophotometric and fluorometric procedures have been developed for the analysis of nitrite ion based upon 2,3-naphthotriazole formation with the reagent 2,3-diaminonaphthalene. Reaction conditions, interferences, solvent extraction, and sensitivity of the procedures are discussed.

Surface modification of glass capillaries for gas chromatography by silylation

Abstract: The coating with silicone oil SF-96 and dinonyl phthalate of capillaries first treated with silylation reagents containing different functional groups yields columns whose efficiencies and film, thicknesses depend on the polarity of the group. Some improvement in dinonyl phthalate column properties was observed if the glass was previously, treated with allyl-or phenyltrichlorosilane, but best results were obtained for this phase when the allyltrichlorosilanized glass capillaries were further treated with oxygen at high temperature.

Selective reduction of 2-ene-1,4-diones and 2-en-1-ones with di-i-butylaluminium hydride

Abstract: Reduction of 2-ene-1,4-diones and 2-enones with di-i-butylaluminium hydride provides the corresponding unsaturated alcohols in excellent yields and this reagent appears to be superior to other metal hydrides including aluminium hydride.