scholarly journals A quick method for the determination of inhibition constants

1982 ◽  
Vol 205 (3) ◽  
pp. 631-633 ◽  
Author(s):  
S G Waley
Keyword(s):  
Competitive Inhibition ◽  
Inhibition Constant ◽  
Quick Method ◽  
Mixed Inhibition ◽  
The Common ◽  
Inhibition Constants ◽  
The Difference ◽  
The Times ◽  
Substrate Concentrations

The inhibition constant Ki in the common case of competitive inhibition can be obtained by simple comparison of progress curves in the presence and in the absence of inhibitor. The difference between the times taken for the concentration of substrate to fall to the same value is used to obtain Ki. The procedure to use when the product inhibits is described. When there is mixed inhibition, reactions at different substrate concentrations are used to obtain both inhibition constants.

scholarly journals On the determination of the difference of longitude, by means of the magnetic telegraph. By Elias Loomie, Esq., in a letter to Lieut.-Col. Sabine, R. A., For. Sec. R. S. Communicated by Lieut.-Col. Sabine, R. A., For. Sec. R. S

1851 ◽  
Vol 5 ◽  
pp. 787-789
Keyword(s):  
New York ◽  
Usual Manner ◽  
Series Of Experiments ◽  
The Difference ◽  
The Times ◽  
The Right ◽  
Time Pieces ◽  
Right Ascension ◽  
Source Of Error

The writer first refers to a series of experiments made under the direction of Professor Bache, for the determination of the difference of longitude between New York, Philadelphia and Washington, by means of the magnetic telegraph. By this series of experiments he considers it established that, by means of Morse’s telegraph, two clocks distant from each other 200 miles, can be compared together with the same precision as if they were placed side by side; and that the difference of longitude of two places can be determined with the same precision as the relative error of the clocks. These results were so satisfactory that Professor Bache determined to pro­secute them more extensively, and during the past summer comparisons have been made between New York and Cambridge observatory near Boston. The plan of operation this season was more matured than during the former. The comparisons were all made between a solar chronometer at Cambridge and a sidereal clock at New York. At ten o’clock in the evening, the two observatories having been put in telegraphic communication, when the seconds hand of the solar chronometer came round to 60 s , a signal was given at Cambridge, by pressing the key of the telegraph-register; at the same instant a click was heard at New York, and the time was recorded according to the sidereal clock. At the end of 10 s a second signal was given, which was also recorded at New York; at the end of another 10 s a third signal was given, and so on for sixty seconds. The Cambridge astronomer then commenced beating seconds by striking the key of the telegraph-register in coincidence with the beats of his chronometer. The New York astronomer compared the signals received with the beats of his clock, and waited for a coincidence. When the beats were sensibly synchronous the time was recorded, and the astronomer waited six minutes for another coincidence of beats. The Cambridge astronomer continued beating seconds for fifteen minutes , during which time the New York observer was sure of two coincidences, and might obtain three. When these were concluded, the New York astronomer in the same manner gave signals for one minute at intervals of 10 s , and then beat seconds for fifteen minutes, during which time the Cambridge astronomer obtained four or five coincidences upon his chronometer. This mode of comparison was practised every night, and it is considered that the uncertainty in the comparison of the time-pieces cannot exceed two or three hundredths of a second on any night; and in a series of comparisons the error may be regarded as entirely eliminated. Another mode of comparison which was practised is that of telegraphing star transits. A list of stars which culminate near our zenith at intervals of five or six minutes was prepared, and the observers, both at New York and Cambridge, were furnished with a copy. They then proceeded as follows: Cambridge selected two stars from the list, which we wall call A and B, and struck the key of his register at the instant when the star A passed each of the seven wires of his transit. These signals were heard at New York, and the times recorded. Cambridge then observed the transit of star B in the ordinary manner without telegraphing. New York then observed the transit of star A on his meridian in the usual manner; and struck his key at the instant the star B passed each of the seven wires of his transit, which signals were heard and recorded at Cambridge. The difference of longitude between New York and Cambridge is nearly twelve minutes, affording ample time for all these observations. Thus New York obtained upon his own clock the times of transit of star A over the meridians of Cambridge and New York; and Cambridge obtained upon his chronometer the times of transit of star B over the same meridians. The difference of these times gives the difference of longitude independent of the right ascension of the stars. Both observers then reversed the axis of their transit instruments; Cambridge selected a second pair of stars from the list, and the same series of observations was repeated as with the first pair. The error of collimation was thus eliminated, and by confining the observations to stars within about five degrees of the zenith, the influence of azimuthal error was avoided. The level being read at every reversal, the correction for it was applied by computation. In this manner it is hoped to eliminate every possible source of error, except that which arises from the personal habits of the observers. In order to eliminate this error, a travelling observer worked for a time at Cambridge and compared with the Cambridge astronomer; then came to New York and compared with the New York astronomer; then returned to Cambridge again, and so on as often as was thought necessary. Finally, at the conclusion of the campaign all the observers were to meet at Cambridge and make a general comparison of their modes of observation.

Barometrical observations, showing the effect of the direction of the wind on the difference between distant barometers

1843 ◽  
Vol 4 ◽  
pp. 386-387
Keyword(s):  
Atmospheric Pressure ◽  
The North ◽  
Heating And Cooling ◽  
Westerly Winds ◽  
Different Seasons ◽  
The Subject ◽  
The Difference ◽  
The Times ◽  
The One

The author institutes a comparison between the barometric heights as observed at the Apartments of the Royal Society, and at his house in Herefordshire, in the neighbourhood of Ross, with a view to ascertain the influence of prevailing winds on the atmospheric pressure. The barometers thus compared together were of the same construction, and by the same maker; and the times of observation, namely nine o’clock a. m. and three o’clock p. m., were the same at both places, the distance between which is 110 miles in longitude, and about 20 in latitude. The degree of accordance in the march of the two barometers is exhibited by that of curves traced on three sheets accompanying the paper. The results are given in eight tables. The author agrees with Schubler in ascribing the currents prevailing in the atmosphere to the variable relations of heating and cooling which obtains between the Atlantic Ocean and the continent of Europe at different seasons; the facts ascertained by the series of observations here presented being in accordance with that hypothesis. If the northerly and westerly winds in England be partly the effect of the expansion of the air on the continent, then the barometer which is nearest to the continent, or in this instance that at London, ought to be relatively more depressed than the one more distant; or if the southerly and easterly winds be regarded as proceeding to the ocean, then, for a similar reason, the barometer nearest to the ocean ought to be relatively depressed; and that both these effects are produced, is shown by the tables. This view of the subject also, the author remarks, is corroborated by Raymond’s observations, detailed in his memoir on the determination of the height of Clermont Ferrand, from which it appears that with the north winds, the southern barometer was most depressed; while the reverse occurred with the southerly winds.

scholarly journals Determination of Kinetic Parameters and The Effect of Ion Mg2+ Inhibition Into Pectinase Activities.

2020 ◽  
Vol 4 (2) ◽  
pp. 112
Author(s):  
Dian Puspita Anggraini ◽  
Devita Sulistiana ◽  
Dwi Kameluh Agustina ◽  
Almira Ulimaz
Keyword(s):  
Kinetic Parameters ◽  
Acid Content ◽  
Galacturonic Acid ◽  
Competitive Inhibition ◽  
Inhibitory Effect ◽  
Inhibition Constant ◽  
Activity Test ◽  
Pectinase Activity ◽  
Substrate Hydrolysis

The purpose of study was to determine kinetic parameters and inhibitory effect of Mg2+ ions on pectinase. Activity test performed at pH 4,5 temperature 55oC for 50' with 10 mm concentrations of each ion 0-10mm. Galacturonic acid content, as product of pectin substrate hydrolysis, was used as basis for determining activity and analyzed by visible spectrophotometry. At concentrations 2 and 4 mm Mg2+ act as an activator, but at concentrations 6, 8, and 10 mM as inhibitors. The value of KM with and without inhibitors is almost same, that is 0.3145% and 0.3105% but value of Vm from both are different, that is 80,645 μg.ml-1.minute-1 and 62,112 μg.ml-1.minute-1. The conclusion that type of inhibitory pectinase with Mg2+ is a non-competitive inhibition. The inhibition constant value (Ki) is 26,84.

scholarly journals Oscillography of adsorption phenomena III. Rates of deposition of oxygen upon tungsten

1938 ◽  
Vol 165 (920) ◽  
pp. 148-160 ◽  
Author(s):  
M. C. Johnson ◽  
A. F. Henson ◽  
Marcus Laurence Elwin Oliphant
Keyword(s):  
Temperature Coefficient ◽  
High Speed ◽  
Thermionic Emission ◽  
Atomic Layer ◽  
The Common ◽  
The Difference ◽  
Initial Deposition ◽  
Heat Of Dissociation ◽  
Adsorption Phenomena

The only temperature coefficient hitherto measured for the atomic layer of oxygen on tungsten is that which demonstrates the 150,000 cal. /mol. expended in its desorption. If, however, some energy is required before the difference between this heat of adsorption and the heat of dissociation can be liberated, a further temperature coefficient will exist, giving variability to the “condensation coefficient” or fraction of impinging molecules which become enabled to contribute to this layer. Any such variability extends the notion of “activated adsorption” from the slow processes with which it has become associated to the almost instantaneous reaction of “chemisorption”. Since filling of the atomic layer is generally supposed to precede oxidation, and oxidation itself has already been studied through the subsequent volatilization of oxide (Langmuir 1915; Rideal and Wans-brough-Jones 1929), an experimental determination of whether the initial deposition also needs activating would be highly desirable. This would, however, be inaccessible to most technique because of the high speed of recording needed. The oscillographic study of reaction velocity, developed by one of us in collaboration with Dr F. A. Vick, and hitherto applied only to evaporation (Johnson and Vick 1935), offers the opportunity by suitable modifications. It fulfills the following requirements. (1) Reaction time may be kept below 1 sec., avoiding the usual slow contaminations due to gases which strike the walls. (2) The surface may be proved to be clean, within a second of gas being admitted, by observation of its thermionic emission, thus escaping the common ascription of activations to impurity. (3) The gas-covered fraction may be kept small enough to avoid interaction between surface particles. (4) No other substance beside oxygen and tungsten is introduced as reagent or as indicator.

scholarly journals The Use of the Generalized Linear Model to Assess the Speed and Uniformity of Germination of Corn and Soybean Seeds

Agronomy ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 588
Author(s):  
Deoclecio Jardim Amorim ◽  
Amanda Rithieli Pereira dos Santos ◽  
Gabriela Nunes da Piedade ◽  
Rute Quelvia de Faria ◽  
Edvaldo Aparecido Amaral da Silva ◽  
...  
Keyword(s):  
Generalized Linear Model ◽  
Linear Models ◽  
Soybean Seeds ◽  
Link Function ◽  
Physiological Quality ◽  
The Difference ◽  
The Times ◽  
Binomial Response

The use of seeds with high physiological quality allows rapid growth and establishment of seedlings in the field to be obtained. Therefore, the accuracy of the information obtained during the determination of the physiological quality of seeds is of great importance. The objective was to use generalized linear models, investigating which link function (Probit, Logit and Complementary log-log) is suitable to predict T50 and uniformity during germination of soybean and corn seeds. To perform the experiments, we used seeds from five commercial hybrids and/or cultivars of corn and soybean. The germination speed was calculated by counting the germinated seeds and the results were expressed in the form of proportions. Germination uniformity was calculated by the difference in the times required for germination. The best model was selected according to the criteria of the test of Deviance, AIC and BIC. The Logit model showed accurate results for most cultivars. The evaluation of germination in the form of proportions considering the assumption of binomial response is satisfactory, and the choice of the link function is dependent on the characteristics of each lot and/or species evaluated. The use of this methodology makes it possible to estimate any germination time and uniformity.

scholarly journals The Kinetic and Analytical Aspects of Enzyme Competitive Inhibition: Sensing of Tyrosinase Inhibitors

Biosensors ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 322
Author(s):  
Raouia Attaallah ◽  
Aziz Amine
Keyword(s):  
Competitive Inhibition ◽  
Kojic Acid ◽  
Amperometric Response ◽  
Competitive Inhibitors ◽  
Tyrosinase Inhibitors ◽  
Carbon Black Paste ◽  
Optimized Conditions ◽  
Paste Electrode ◽  
Substrate Concentrations

An amperometric biosensor based on tyrosinase, immobilized onto a carbon black paste electrode using glutaraldehyde and BSA was constructed to detect competitive inhibitors. Three inhibitors were used in this study: benzoic acid, sodium azide, and kojic acid, and the obtained values for fifty percent of inhibition (IC50) were 119 µM, 1480 µM, and 30 µM, respectively. The type of inhibition can also be determined from the curve of the degree of inhibition by considering the shift of the inhibition curves. Amperometric experiments were performed with a biosensor polarized at the potential −0.15 V vs. Ag/AgCl and using 0.1 M phosphate buffer (pH 6.8) as an electrolyte. Under optimized conditions, the proposed biosensor showed a linear amperometric response toward catechol detection from 0.5 µM to 38 µM with a detection limit of 0.35 µM (S/N = 3), and its sensitivity was 66.5 mA M−1 cm−2. Moreover, the biosensor exhibited a good storage stability. Conversely, a novel graphical plot for the determination of reversible competitive inhibition was represented for free tyrosinase. The graph consisted of plotting the half-time reaction (t1/2) as a function of the inhibitor concentration at various substrate concentrations. This innovative method relevance was demonstrated in the case of kojic acid using a colorimetric bioassay relying on tyrosinase inhibition. The results showed that the t1/2 provides an extended linear range of tyrosinase inhibitors.

scholarly journals Screening attenuation of coaxial cables determined in GTEM-cells

2005 ◽  
Vol 2 ◽  
pp. 33-38
Author(s):  
A. Knobloch ◽  
H. Garbe
Keyword(s):  
Radiation Resistance ◽  
Standard Methods ◽  
Cell Method ◽  
Radiated Power ◽  
Antenna Characteristic ◽  
The Common ◽  
The Difference ◽  
Gtem Cell ◽  
Good Agreement

Abstract. This paper describes the determination of the screening attenuation with a GTEM cell. An analytical part gives the link between the voltage at the cell port and the total radiated power. The next section investigates the optimal cable setup in the cell. With a measurement of the common mode current on the cable and a simulation of the radiation resistance the loop antenna characteristic of the cable setup could be verified. It is shown that the use of ferrit cores decrease the difference between the maximum and the minimum screening attenuation. The determination of great screening attenuation could be improved with the use of N-type measurement cables. A comparison between this GTEM cell method and the standard methods shows a good agreement.

Synthesis of 6-Aryloxy- and 6-Arylalkoxy-2-chloropurines and Their Interactions with Purine Nucleoside Phosphorylase from Escherichia coli

1999 ◽  
Vol 54 (12) ◽  
pp. 1055-1067 ◽  
Author(s):  
Agnieszka Bzowska ◽  
Lucyna Magnowska ◽  
Zygmunt Kazimierczuk
Keyword(s):  
Mixed Type ◽  
Purine Nucleoside Phosphorylase ◽  
Phase Transfer ◽  
Competitive Inhibition ◽  
Purine Nucleoside ◽  
Inhibition Constant ◽  
Purine Base ◽  
Nucleoside Phosphorylase ◽  
E Coli ◽  
Inhibition Constants

The phase transfer method was applied to perform the nucleophilic substitution of 2,6- dichloropurines by modified arylalkyl alcohol or phenols. Since under these conditions only the 6-halogen is exchanged, this method gives 2-chloro-6-aryloxy- and 2-chloro-6-arylalkoxypurines. 2-Chloro-6-benzylthiopurine was synthesized by alkylation of 2-chloro-6-thiopurine with benzyl bromide. The stereoisomers of 2-chloro-6-(1-phenyl-1-ethoxy)purine were obtained from R- and S-enantiomers of sec.-phenylethylalcohol and 2,6-dichloropurine. All derivatives were tested for inhibition with purified hexameric E. coli purine nucleoside phosphorylase (PNP). For analogues showing IC50 < 10 μm, the type of inhibition and inhibition constants were determined. In all cases the experimental data were best described by the mixed-type inhibition model and the uncompetitive inhibition constant, Kiu, was found to be several-fold lower than the competitive inhibition constant, Kic. This effect seems to be due to the 6-aryloxy- or 6-arylalkoxy substituent, because a natural PNP substrate adenine, as well as 2-chloroadenine, show mixed type inhibition with almost the same inhibition constants Kiu and KiC. The most potent inhibition was observed for 6-benzylthio-2-chloro-, 6-benzyloxy-2-chloro-, 2-chloro-6-(2-phenyl-l-ethoxy), 2-chloro-6-(3-phenyl-l-propoxy)- and 2-chloro-6-ethoxypurines (Kiu = 0.4, 0.6, 1.4, 1.4 and 2.2 μm, respectively). The R-stereoisomer of 2-chloro-6-(1pheny-1-ethoxy)purine has Kiu = 2.0 μm, whereas inhibition of its S counterpart is rather weak (IC50> 12 μm). More rigid (e.g. phenoxy-), non-planar (cyclohexyloxy-), or more bulky (2,4,6-trimethylphenoxy-) substituents at position 6 of the purine base gave less potent inhibitors (IC50 = 26, 56 and >100 μm, respectively). The derivatives are selective inhibitors of hexameric “high-molecular mass” PNPs because no inhibitory activity vs. trimeric Cellulomonas sp. PNP was detected. By establishing the ligand-dependent stabilization pattern of the E. coli PNP it was shown that the new derivatives, similarly as the natural purine bases, are able to form a dead-end ternary complex with the enzyme and orthophosphate. It was also shown that the derivatives are substrates in the reverse synthetic direction catalyzed by E. coli PNP

FRACTIONAL DETERMINATIONS OF URINARY 17-KETOSTEROIDS IN HYPEREMESIS GRAVIDARUM

1962 ◽  
Vol 41 (1) ◽  
pp. 123-128 ◽  
Author(s):  
Pentti A. Järvinen ◽  
Sykkö Pesonen ◽  
Pirkko Väänänen
Keyword(s):  
Hyperemesis Gravidarum ◽  
First Trimester ◽  
Control Group ◽  
Before And After ◽  
Daily Urine ◽  
First Trimester Of Pregnancy ◽  
The Difference

ABSTRACT The fractional determination of 17-ketosteroids in the daily urine was performed in nine cases of hyperemesis gravidarum and in four control cases, in the first trimester of pregnancy both before and after corticotrophin administration. The excretion of total 17-KS is similar in the two groups. Only in the hyperemesis group does the excretion of total 17-KS increase significantly after corticotrophin administration. The fractional determination reveals no difference between the two groups of patients with regard to the values of the fractions U (unidentified 17-KS), A (androsterone) and Rest (11-oxygenated 17-KS). The excretion of dehydroepiandrosterone is significantly higher in the hyperemesis group than in the control group. The excretion of androstanolone seems to be lower in the hyperemesis group than in the control group, but the difference is not statistically significant. The differences in the correlation between dehydroepiandrosterone and androstanolone in the two groups is significant. The high excretion of dehydroepiandrosterone and low excretion of androstanolone in cases of hyperemesis gravidarum is a sign of adrenal dysfunction.

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