AN IMPROVED COLORIMETRIC METHOD FOR THE DETERMINATION OF PROLINE IN THE PRESENCE OF OTHER NINHYDRIN-POSITIVE COMPOUNDS.
Ontology highlight
ABSTRACT:
SUBMITTER: WREN JJ
PROVIDER: S-EPMC1206430 | biostudies-other | 1965 Jan
REPOSITORIES: biostudies-other
Similar Datasets
Project description:1. A rapid colorimetric and apparently specific micromethod for the determination of total glutathione in small amounts of tissue is described. Generally, less than 30mg. of tissue is sufficient and this is homogenized in ice-cold 3% metaphosphoric acid. The product is filtered through sintered glass and neutralized or diluted before being added to a cuvette containing phosphate buffer, pH7.1, 5,5'-dithiobis-(2-nitrobenzoic acid), EDTA and glutathione reductase. Addition of NADPH(2) to the system initiates a progressive reduction of 5,5'-dithiobis-(2-nitrobenzoic acid) by catalytic amounts of GSH, and this causes a colour increase at 412mmu. The rate of this change, calculated over 5min., is proportional to the total amount of glutathione present, and consequently unknown concentrations may be determined by reference to standards. 2. A preparation (based on that of Racker, 1955) of a suitable sample of glutathione reductase from yeast is described. 3. A less specific and less sensitive determination of extracted thiol groups with 5,5'-dithiobis-(2-nitrobenzoic acid) at pH8.0, based on observations of Ellman (1959) and Jocelyn (1962), is also described. 4. Although the precise nature of the reaction is not known, evidence is put forward to support a process of cyclo-reduction. GSSG is reduced enzymically to GSH, which reacts with 5,5'-dithiobis-(2-nitrobenzoic acid) to produce a coloured ion: [Formula: see text] (E(max.) 412mmu) and a mixed disulphide. This disulphide reacts with further quantities of GSH to liberate another ion and GSSG, which then re-enters the cycle.
| S-EPMC1206606 | biostudies-other
Project description:The characteristic purple colour formed by N-formyl-N'-2,4-dinitrophenyl-hydrazine in the presence of piperidine and acetone was made the basis of a new quantitative method for the determination of formyl groups. Samples containing N-formyl groups (up to 0.4mumole) are hydrazinolysed at 97-98 degrees for 1hr. and are dinitrophenylated after the removal of excess of hydrazine. Interference from 2,4-dinitrophenylhydrazine is eliminated by subjecting the dinitrophenylated samples to chromatography on an alumina column. Interference arising from the formation of N-acetyl-N'-2,4-dinitrophenylhydrazine, when determining formyl groups in samples containing acetyl, can be avoided by a paper-chromatographic separation before analysis. A standard procedure is described. The method gives satisfactory results when applied to N-formyl-amino acids. Gramicidin, when analysed by this method, was found to contain 0.89 mole of formyl group/mole for a molecular weight of 1880. The method indicated the absence of formyl groups from lysozyme, a protein known not to contain such groups. Generally, the analytical values obtained by the method are within 100+/-4% of theory.
| S-EPMC1187558 | biostudies-other
Project description:The 50 % tissue culture infectious dose (TCID50) is still one of the most commonly used techniques for estimating virus titers. However, the traditional TCID50 assay is time consuming, susceptible to subjective errors and generates only quantal data. Here, we describe a colorimetric-based approach for the titration of Enterovirus 71 (EV71) using a modified method for making virus dilutions. In summary, the titration of EV71 using MTT or MTS staining with a modified virus dilution method decreased the time of the assay and eliminated the subjectivity of observational results, improving accuracy, reproducibility and reliability of virus titration, in comparison with the conventional TCID50 approach (p < 0.01). In addition, the results provided evidence that there was better correlation between a plaquing assay and our approach when compared to the traditional TCID50 approach. This increased accuracy also improved the ability to predict the number of virus plaque forming units present in a solution. These improvements could be of use for any virological experimentation, where a quick accurate titration of a virus capable of causing cell destruction is required or a sensible estimation of the number of viral plaques based on TCID50 of a virus is desired.
| S-EPMC3550799 | biostudies-literature
Project description:Hydrogen peroxide is commonly used as a sterilizing agent for medical devices and its use has recently been extended to N95 masks during PPE shortages as a result of the COVID-19 pandemic. The hydrogen peroxide remaining on the masks after sterilization could potentially pose a health hazard to the mask users. In the present study a colorimetric method was optimized for the determination of hydrogen peroxide on N95 masks following chemical sanitizations. The developed analytical method demonstrated an overall recovery of 98% ± 7%. The limit of detection ranged from 0.16 to 0.25 mg/mask, depending on the type of mask. The expanded measurement uncertainty was 13% (at a 95% confidence interval). The sanitization process itself introduced a significant variation in hydrogen peroxide load between masks. The ozone used in the sanitization process had no significant impact on analytical performance. Stamped and printed marks on the mask surfaces could induce biased readings. Hydrogen peroxide decomposes quickly on the mask surfaces so timing of analysis is an important factor in method standardization.•The validation data demonstrated that the in-house method is reliable and fit for the intended purpose, offering a sensitive, simple, rapid, and inexpensive method of residue monitoring.
| S-EPMC8374716 | biostudies-literature
Project description:A gold nanoparticle (AuNP)-based colorimetric method was developed for the molecular weight (MW) determination of polyethylene glycol (PEG), a commonly used hydrophilic polymer. Addition of a salt solution to PEG-coated AuNP solutions helps in screening the electrostatic repulsion between nanoparticles and generating a color change of the solutions from wine red to blue in 10 min in accordance with the MW of PEG, which illustrates the different stability degrees (SDs) of the AuNPs. The SDs are calculated by the absorbance ratios of the stable to the aggregated AuNPs in the solution. The root mean square end-to-end length (?h2?1/2) of PEG molecules shows a linear fit to the SDs of the PEG-coated AuNPs in a range of 1.938?±?0.156 to 10.151?±?0.176 nm. According to the Derjaguin-Landau-Verwey-Overbeek theory, the reason for this linear relationship is that the thickness of the PEG adlayer is roughly equivalent to the ?h2?1/2 of the PEG molecules in solution, which determines the SDs of the AuNPs. Subsequently, the MW of the PEG can be obtained from its ?h2?1/2 using a mathematical relationship between ?h2?1/2 and MW of PEG molecule. Applying this approach, we determined the ?h2?1/2 and the MW of four PEG samples according to their absorbance values from the ordinary ultraviolet-visible spectrophotometric measurements. Therefore, the MW of PEG can be distinguished straightforwardly by visual inspection and determined by spectrophotometry. This novel approach is simple, rapid, and sensitive.
| S-EPMC3878192 | biostudies-literature
Project description:Many reports have suggested that NRP-1 acts as a co-receptor for VEGF-A165 and boosts tumour growth and metastasis. This NRP-1, due to its important role in tumour progression, triggered interest in the design of new molecules able to significantly inhibit NRP-1/VEGF-A165 interaction to suppress pathological angiogenesis. Our previous SAR studies of compounds, showing affinity for NRP-1, led us to develop branched peptides with general formula Lys(hArg)-AA2-AA3-Arg. Here, three series of analogues were synthesized, in which the middle fragment (AA2 and/or AA3) of initial sequences was substituted with unnatural Pro analogues with different rigidities and ring sizes. The synthesized compounds were screened for VEGF-A165 inhibitory activity on an improved assay (ELISA), which was selected based on our comparative inhibition study of the parent compounds, indicating that the method with chemiluminescence detection gives more accurate data. The results of affinity for NRP-1 and enzymatic stability of newly obtained compounds enabled the selection of new structures, showing a 2 and 4-fold lower IC50 value compared to parent peptides.
| S-EPMC6390686 | biostudies-literature
Project description:There are a significant number of analytical methodologies employing different techniques to determine phenolic compounds in beverages. However, these methods employ long sample preparation processes and great time consumption. The aim of this paper was the development of a simple method for evaluating the phenolic compounds' presence in Brazilian craft beers without a previous extraction step. Catechin, caffeic acid, epicatechin, p-coumaric acid, hydrated rutin, trans-ferulic acid, quercetin, kaempferol, and formononetin were analyzed in fifteen different craft beers. The method showed good linearity (R2 ≥ 0.9966). The limit of detection ranged from 0.08 to 0.83 mg L-1, and limits of quantification were between 0.27 and 2.78 mg L-1. The method showed a satisfactory precision (RSD ≤ 16.2%). A good accuracy was obtained by the proposed method for all phenolic compounds in craft beer (68.6% ˂ accuracy ˂ 112%). Catechin showed higher concentrations (up to 124.8 mg L-1) in the samples, followed by epicatechin (up to 51.1 mg L-1) and caffeic acid (up to 8.13 mg L-1). Rutin and formononetin were observed in all analyzed samples (0.52 mg L-1 to 2.40 mg L-1), and kaempferol was less present in the samples. The presence of plant origin products was determinant for the occurrence of the highest concentrations of phenolic compounds in Brazilian craft beers.
| S-EPMC8399525 | biostudies-literature
Project description:The absolute stereochemistry of compounds with axial and planar chirality is successfully determined by the crystalline sponge method without crystallization or derivatization of the compounds. This method is applied to absolute structure determination in the asymmetric synthesis of unique compounds with axial and planar chirality.
| S-EPMC5496191 | biostudies-literature
Project description:Rapid and convenient biosensing platforms could be beneficial to timely diagnosis and treatment of diseases in virtually any care settings. Sandwich immunoassays, the most commonly used methods for protein detection, often rely on expensive tags such as enzyme and tedious wash and incubation procedures operated by skilled labor. In this report, we revolutionized traditional sandwich immunoassays by providing a wash-free homogeneous colorimetric immunoassay method without requirement of any separation steps. The proposed strategy was realized by controlling the growth of gold nanoparticles (AuNPs) to mediate the interparticle spacing in the protein-AuNP oligomers. We have demonstrated the successful in vitro detection of cancer biomarker in serum samples from patients with high clinical sensitivity and specificity.
| S-EPMC4679354 | biostudies-literature
Project description:This work facilitates detection of bivalent copper ion by a simple Schiff base probe QNH based on a quinoxaline-naphthaldehyde framework. The detailed study in absorption spectroscopy and theoretical aspects and crystal study of the probe and probe-copper complex has been discussed. The detection limit of the probe in the presence of Cu2+ is 0.45 µM in HEPES-buffer/acetonitrile (3/7, v/v) medium for absorption study. The reversibility of the probe-copper complex has been investigated by EDTA. The selective visual detection of copper has been established also in gel form.
| S-EPMC9105850 | biostudies-literature