scholarly journals Studies on enzyme action. V.—Hydrolysis of isomeric glucosides and galactosides by acids and enzymes.

1905 ◽  
Vol 74 (497-506) ◽  
pp. 188-194 ◽  
Author(s):  
Edward Frankland Armstrong ◽  
Henry Edward Armstrong

In view of the use constantly made, in contrasting the action of sucroclastic enzymes, of the stereoisomeric α- and β-methyl glucosides and the corresponding galactosides as test materials, it was desirable to gain some idea of the relative stability of these four compounds in presence of acids and wherever possible towards enzymes, a know­ledge of their behaviour being of importance, both as throwing light on their intrinsic properties and for the purpose of correlating the activities of the various compounds amenable to hydrolysis.

The following account has reference to the pursuance of the inquiry into the nature of the process whereby the fats are hydrolysed under the influence of lipase; the experiments have been made in the hope of discovering an explanation of the selective power which the enzyme undoubtedly displays, as it promotes by preference the hydrolysis of ethereal salts of the higher fatty acids such as are present in the natural fats. The active material used, as a rule, has been the finely ground air-dried residue which is left on depriving crushed castor oil seed of oil by means of ether; although but slightly active towards ethereal salts other than fats, it is easily prepared of uniform quality and does not soon deteriorate when kept. In all cases, the effect produced in blank control experiments is allowed for. As a rule hydrolysis took place at the temperature of the laboratory.


Author(s):  
Zahir Abdul Haddi Hassan ◽  
Constantin Udriște

AbstractIn this paper we shall introduce two equivalent techniques in order to evaluate reliability analysis of electrical aircrafts systems (EAS): (i) graph theory technique, and (ii) simplifying diffeomorphism technique. Geometric modeling of reliability models is based on algebraic hypersurfaces, whose intrinsic properties are able to select those models which are relevant for applications. The basic idea is to cover the reliability hypersurfaces by exponentially decay curves. Most of the calculations made in this paper have used Maple and Matlab software.


1904 ◽  
Vol 73 (488-496) ◽  
pp. 526-537 ◽  
Author(s):  
Edward Frankland Armstrong ◽  
Robert John Caldwell ◽  
Henry Edward Armstrong

Not only are the various bioses hydrolysed at very different rates by enzymes but they are also known to differ in their behaviour towards acids: cane sugar being hydrolysed with the greatest facility, whilst maltose is acted upon but slowly. The experiments described in this communication were instituted primarily with the object of ascertaining the behaviour of milk sugar, of which nothing was known. The hydrolysis of cane sugar under the influence of acid was carefully investigated by Wilhelmy as far back as 1850, with the aid of the polariscope, then a new instrument.


2011 ◽  
Vol 146 ◽  
pp. 51-63 ◽  
Author(s):  
Khedoudja Laoubi ◽  
Nabila Belloul ◽  
Ali Ahmed Benyahia ◽  
Aîcha Sérier ◽  
Nourdine Ouali

The aim of this work is the study of the long term behaviour of a laminated composite made in glass/polyester and aged in seawater at various temperatures. The results obtained show that the immersion in seawater causes ageing of the composite material. This was reflected first by a change in color of the material depending on the temperature of the immersion and the gel-coat loses its brightness. The infrared spectroscopy has confirmed activation of chemical degradation (hydrolysis of the resin and of the fibre/matrix interface, fibre degradation). This chemical degradation could be the cause of decrease in strength and ductility detected by analysing the behaviour of immersed testing specimens. It could also be the cause of the increase of absorption rate recorded for immersions exceeding 22 days.


1954 ◽  
Vol 44 (01) ◽  
pp. 7-44 ◽  
Author(s):  
W.E. Boyd

Summary1. A method is described for investigating the possible action of microdoses of mercuric chloride on the hydrolysis of soluble starch with malt diastase.2. The microdoses of the mercuric chloride used in the latest crucial series carried out in1946, 1948, and 1952, were what are termed “high potencies” made in accordance with the pharmaceutical method of preparation of drugs ordinarily used in the practice of homœotherapy.3. These microdoses were prepared by separate stages of dilution, the solution at each stage being subjected to mechanical shock. The solutions were, theoretically, “dilutions” of the order of 1 in 10−61 and on present physical theory would not contain any molecules of the original mercuric chloride.4. The difference in rate of hydrolysis between flasks containing starch, diastase, and distilledwater (controls) and flasks containing starch, diastase and microdoses of mercuric chloride (tests) were compared colorimetrically by the Spekker absorptiometer, and the frequencies of the differences statistically analysed, as the results obtained showed biological scatter. More than 500 such comparisons were carried out. The differences of means were examined by the Fisher “t” test, the variances tested and Cochrane and Cox's test applied where indicated. All the series gave a highly significant difference in the rate of hydrolysis between controls and tests, the microdoses stimulating the process. Statistically the significance is shown by the fact that a probability of <0·001 was obtained independently in each of the three years 1946, 1948 and 1952. The control results gave an approximately normal distribution.5. The distribution, control methods, and accessory control procedures were considered toexclude, as a cause of the effects, adsorption of the original drug and the presence of extraneous contaminants by chance solely in test flasks. The only difference between control and microdose flasks was the addition of microdose, the distilled water being common to both controls and tests.6. It was concluded that a factor, unidentified, derived from the mercuric chloride used, waspresent in solutions prepared by serial dilution with mechanical shock which could affect the distilled water diluent, that this change was transferable to subsequent “ultramolecular” stages of “dilution”, and that this factor was the source of the activity in the microdose solutions producing the acceleration of the rate of hydrolysis.7. In an addendum there is described recent biological work which is also providing evidence of the presence of an active selective factor in “high potencies” derived from Strophanthus sarmentosus by the same methods of dilution with mechanical shock.


1972 ◽  
Vol 25 (2) ◽  
pp. 421 ◽  
Author(s):  
EJ Halbert ◽  
MJ Rogerson

Few iron(111) complexes of amino acids have been isolated although attempts have been made to measure their stabilities in solution. Iron(111) in the presence of various amino acids showed no complex formation during pH titration in aqueous solution. Using oxidation-reduction and spectrophotometric techniques Perrin measured the stabilities of 1 : 1 complexes of iron(111) with different amino acids in solutions of low pH. Rapid hydrolysis of iron(111) occurred when the pH was increased even in the presence of a large excess of amino acids. Bielig and Bayer reported the isolation of a bis-complex of iron(111) and methionine prepared in aqueous solution. McAuliffe, Quagliano, and Vallarinoe reported a tris-complex made in ethanol, though their iron analysis was not consistent with the required structure. In both cases magnetic and infrared studies were used to characterize the products. Our attempts to repeat these preparations were unsuccessful. This paper describes the preparation of two 1 : 1 complexes of methionine and iron(111) and an investigation of their properties by analysis of infrared, magnetic, and N.M.R. measurements.


2021 ◽  
Vol 11 (3) ◽  
pp. 33
Author(s):  
Mahesh B. Manandhar ◽  
Mohammad A. Matin

The use of Aluminum Gallium Nitride (AlGaN) as a power switching device material has been a promising topic of research in recent years. Along with Silicon Carbide (SiC) and Gallium Nitride (GaN), AlGaN is categorized as a Wideband Gap (WBG) material with intrinsic properties best suited for high power switching applications. This paper simulates and compares the thermal and electrical performance of AlGaN and Silicon (Si) MOSFETs, modeled in COMSOL Multiphysics. Comparisons between similar AlGaN/GaN and Si power modules are made in terms of heatsink requirements. The temperatures for the same operating voltage are found to be significantly lower for the AlGaN MOSFETs structures, compared to Si. The heatsink size for the AlGaN/GaN is found to be smaller compared to Si for the power modules.


Author(s):  
Xia Sun ◽  
Xiangyou Wang ◽  
Zhe Liu

In this paper, two acetylcholinesterase (AChE) immobilization methods on the surface of a glassy carbon electrode (GCE) were compared. AChE-employed homogenate from chicken brain was home-made in the laboratory. The immobilization methods employed a cross-linking method with glutaraldehyde as a cross-linking agent, bovine serum albumin (BSA) as a protectant, and sol-gel method with tetraethoxysilane (TEOS). AChE was immobilized on chitosan membranes by these two immobilization methods. Then the enzyme membrane was fixed on the surface of GCE to prepare an AChE-GCE amperometric biosensor for the detection of organophosphorus pesticide. Measuring the activity of immobilization AChE by the oxidation current of thiocholine (TCh), produced by hydrolysis of the acetylthiocholine iodide (ATChI) substrate, the results showed that the activity of AChE-employed sol-gel method with TEOS was higher than the cross-linking method with glutaraldehyde. Biosensor sensitivity and reproducibility were statistically evaluated for the different immobilization methods and the most suitable immobilization procedure was selected.


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