A COLORIMETRIC METHOD FOR THE ESTIMATION OF REDUCING GROUPS IN MILK POWDERS

1945 ◽  
Vol 23b (3) ◽  
pp. 91-99 ◽  
Author(s):  
R. A. Chapman ◽  
W. D. McFarlane
Keyword(s):  
Amino Acids ◽  
Positive Reaction ◽  
Colorimetric Method ◽  
Protein Molecule ◽  
Potassium Ferricyanide ◽  
Potassium Iodate ◽  
Detection And Estimation ◽  
Reducing Activity ◽  
Colorimetric Estimation

A method has been developed for the detection and estimation of certain reducing groups in milk powders. The method is based on the reduction of potassium ferricyanide at 70 °C. and pH 5 and colorimetric estimation of ferric ferrocyanide. Titration with 2,6-dichlorophenolindophenol or potassium iodate failed to show any difference between fresh and stale milk powders. In contrast the ferricyanide test indicates much higher values in fresh powders than do the titration methods, and it also reveals a marked increase in samples that have developed stale, musty odours and flavours. Lactalbumin and casein show reducing activity that increases on heating. Of the amino acids tested, only tryptophane gives a positive reaction. It is concluded that the reducing groups are present in the protein molecule and become accessible on denaturation.

On the Nutrition and metabolism of zooplankton IV. The forms of nitrogen excreted By Calanus

1967 ◽  
Vol 47 (1) ◽  
pp. 113-120 ◽  
Author(s):  
E. D. S. Corner ◽  
B. S. Newell
Keyword(s):  
Amino Acids ◽  
Positive Reaction ◽  
Laboratory Experiments ◽  
Long Island Sound ◽  
Acartia Tonsa ◽  
Nitrogenous Compounds ◽  
Nitrogenous Substances ◽  
Experimental Density ◽  
Island Sound ◽  
Calanus Helgolandicus

A study has been made of the nitrogenous compounds excreted by Calanus helgolandicus (Claus) collected at Plymouth.Most of the excreted nitrogen is in the form of ammonia which accounts for 60–100% (average 74.3%) of the total, and some of the remainder may be lost as urea. There is no evidence for the excretion of measurable amounts of amino acids.Whether the animals are starved or fed they are primarily ammonotelic, and the quantity of ammonia produced at 10° C (3.33 μg/g. dry body wt/day) is not significantly changed when the animals are used at an abnormally high experimental density. This latter condition does, however, lead to the production of large quantities of additional nitrogenous substances that give a positive reaction with ninhydrin.IntroductionThe amounts of nitrogen excreted by zooplankton have been measured by several workers. Harris (1959) used the method of Riley (1953) to estimate the copious quantities of ammonia produced by animals (mainly Acartia tonsa and A. clausi) collected from Long Island Sound; Beers (1964), in laboratory experiments with the chaetognath Sagitta hispida, estimated the excreted ammonia by the procedure of Kruse & Mellon (1952); and Corner, Cowey & Marshall (1965) determined the ammonia excreted by Calanus helgolandicus and C. finmarchicus, using a ninhydrin technique described by Moore & Stein (1954). The methods employed by Harris and by Beers are specific for ammonia: that used by Corner et al. estimates nitrogenous substances (e.g. amino acids) in addition to ammonia, but certain tests were made which seemed to exclude the possibility that these substances contributed significantly to the nitrogen excreted by the animals.

Mise en évidence d'une activité uréasique chez Streptococcus thermophilus

1988 ◽  
Vol 34 (6) ◽  
pp. 818-822 ◽  
Author(s):  
V. Juillard ◽  
M. J. Desmazeaud ◽  
H. E. Spinnler
Keyword(s):  
Amino Acids ◽  
Urease Activity ◽  
Culture Medium ◽  
Colorimetric Method ◽  
Streptococcus Thermophilus ◽  
Stationary Growth Phase ◽  
Optimal Temperature ◽  
Ammonium Ions ◽  
Stationary Growth ◽  
Optimal Ph

In Streptococcus thermophilus CNRZ 404, the presence of urease activity was demonstrated by means of a specific colorimetric method for ammonium ions. The main physicochemical properties of the enzyme were determined. The Km with urea as substrate was 1.19 mM and the optimal pH was approximately 7.5. Because both thermolability and enzyme activity increased as the temperature was increased to 70 °C, the optimal temperature could not be determined with precision. Urease activity was maximal at the beginning of the stationary growth phase; it was stimulated by the presence of urea and of certain amino acids such as arginine and glutamic acid in the culture medium. This activity has been detected in several other strains of Streptococcus thermophilus. [Translated by the journal]

3 FACTORIAL DESIGN FOR OPTIMISATION OF COLORIMETRIC METHOD FOR QUANTIFICATION OF CAPTOPRIL

INDIAN DRUGS ◽  
2016 ◽  
Vol 53 (09) ◽  
pp. 47-52
Author(s):  
S. S Desai ◽  
◽  
K. A Dave ◽  
J. D. Naik ◽  
A. B. Yadav
Keyword(s):  
Factorial Design ◽  
Ferric Chloride ◽  
Regression Coefficient ◽  
Colorimetric Method ◽  
Chloride Concentration ◽  
Potassium Ferricyanide ◽  
Optimum Concentration ◽  
Design Expert ◽  
Method Effect ◽  
Ich Guidelines

Captopril was quantitatively determined by colorimetry using ferric chloride and potassium ferricyanide. 33 factorial design with help of design expert software (version 9.0.4) was used for optimisation of method. Effect of method variables such as concentration of ferric chloride, concentration of potassium ferricyanide and volume of both reagents was evaluated on method response absorbance. Optimum concentration of ferric chloride and potassium ferricyanide was found to be 0.3% and 0.2%, respectively and optimum volume of both reagents was found to be 1.5 mL. The developed method was validated as per ICH guidelines. The linearity of the proposed method was found in the concentration range of 1.0 – 6.0 μg/mL with regression coefficient (R2) of 0.9913. The % recovery was found between 98.23- 104.25 %. The method was found to be precise as the values of % RSD obtained were found to be

Collaborative Study of Betaine in Orange Juice

1970 ◽  
Vol 53 (3) ◽  
pp. 568-571
Author(s):  
Grayson R Rogers
Keyword(s):  
Amino Acids ◽  
Standard Deviation ◽  
Ion Exchange ◽  
Systematic Error ◽  
Orange Juice ◽  
Collaborative Study ◽  
Colorimetric Method ◽  
Actual Data ◽  
Random Errors ◽  
Water Solutions

Abstract An ion exchange-colorimetric method for determining betaine in orange juice was studied by 11 collaborators on 4 orange juice samples and 2 synthetic water solutions consisting of sucrose, dextrose, and various amino acids found in orange juice. Average recoveries in the collaborative study were 96.7 and 95.9%. Results show that the precision standard deviation among laboratories is generally acceptable. The distribution of the actual data is greater than normally expected, but random errors appear to be responsible since no significant systematic error can be detected in the data. The method is recommended for adoption as official first action.

Strahleninduzierte Aggregatbildung von Proteinen: Bindung von Aminosäuren an Myoglobin / Radiation-Induced Aggregation of Proteins: Binding of Amino Acids to Myoglobin

1978 ◽  
Vol 33 (3-4) ◽  
pp. 203-209 ◽  
Author(s):  
Vera Jakubick ◽  
Henry Delincée
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Protein Molecule ◽  
Reactive Species ◽  
Radiation Induced ◽  
Induced Aggregation ◽  
Sulfur Containing ◽  
Tryptic Hydrolysis ◽  
Radioactive Spot

When myoglobin is irradiated in the presence of amino acids, the most radiation-reactive species, like the aromatic and sulfur-containing amino acids, will bind preferentially to the protein. The radiation-induced binding is strongly dependent on the concentration of protein and amino acid. Subsequent to irradiation of myoglobin in the presence of radioactively labelled tryptophan followed by tryptic hydrolysis, only a single radioactive spot was detected on the fingerprint. The binding of amino acids is thus not randomly distributed over the protein molecule but occurs at specific reactive sites.

scholarly journals A novel sensitive colorimetric determination of catecholamine drug in dosage form via oxidative coupling reaction with MBTH and potassium ferricyanide

2021 ◽  
Vol 5 (1) ◽  
pp. 51-58
Author(s):  
Safwan Ashour
Keyword(s):  
Oxidative Coupling ◽  
Colorimetric Method ◽  
Standard Free Energy ◽  
Coupling Reaction ◽  
Pharmaceutical Formulations ◽  
Molar Absorptivity ◽  
Potassium Ferricyanide ◽  
Colorimetric Determination ◽  
Oxidative Coupling Reaction

A new and direct colorimetric method has been established for the determination of catecholamine (methyldopa, MD) in both pure form and in pharmaceutical formulations. The method is based on the oxidative coupling reaction of MD with 3-methyl-2-benzothiazolinone hydrazone hydrochloride monohydrate (MBTH) and potassium ferricyanide at pH 10.4 in aqueous medium to form an orange product that has a maximum absorption at 460 nm. Beer's law plot showed good correlation in the concentration range of 1.0−56.0 µg mL-1, with detection limit of 0.31 µg mL-1. Molar absorptivity for the above method was found to be 6.56×103 L mol-1 cm-1. All the measurements were carried out at 25 ± 1.0 °C, the formation constant (logKf) value of colored species is 9.48 and the standard free energy (DG‡) is − 54.09 KJ mol-1. This method was applied successfully to determination of MD in tablets and the results were compared with the USP method. Common excipients used as additives in tablets do not interfere in the proposed method. The method is accurate, precise and highly reproducible, while being simple, cheap and less time consuming and hence can be suitably applied for routine analysis of MD in bulk and dosage forms.

scholarly journals Evaluation of two Plasmodium vivax sexual stage antigens as transmission-blocking vaccine candidates

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Yongzhe Zhang ◽  
Fei Liu ◽  
Yan Zhao ◽  
Fan Yang ◽  
Jie Bai ◽  
...  
Keyword(s):  
Amino Acids ◽  
Plasmodium Vivax ◽  
Recombinant Proteins ◽  
Expression System ◽  
Anopheles Dirus ◽  
Transmission Blocking ◽  
Yeast Expression System ◽  
Membrane Feeding ◽  
Reducing Activity ◽  
Membrane Feeding Assay

Abstract Background Plasmodium vivax transmission-blocking vaccines (TBVs) are receiving increasing attention. Based on excellent transmission-blocking activities of the PbPH (PBANKA_0417200) and PbSOP26 (PBANKA_1457700) antigens in Plasmodium berghei, their orthologs in P. vivax, PVX_098655 (PvPH) and PVX_101120 (PvSOP26), were selected for the evaluation of their potential as TBVs. Methods Fragments of PvPH (amino acids 22–304) and PvSOP26 (amino acids 30–272) were expressed in the yeast expression system. The recombinant proteins were used to immunize mice to obtain antisera. The transmission-reducing activities of these antisera were evaluated using the direct membrane feeding assay (DMFA) using Anopheles dirus mosquitoes and P. vivax clinical isolates. Results The recombinant proteins PvPH and PvSOP26 induced robust antibody responses in mice. The DMFA showed that the anti-PvSOP26 sera significantly reduced oocyst densities by 92.0 and 84.1% in two parasite isolates, respectively, whereas the anti-PvPH sera did not show evident transmission-reducing activity. The variation in the DMFA results was unlikely due to the genetic polymorphisms of the two genes since their respective sequences were identical in the clinical P. vivax isolates. Conclusion PvSOP26 could be a promising TBV candidate for P. vivax, which warrants further evaluation. Graphical Abstract

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