Substrate Hydroxyl Groups Are Involved in the Ionization of Catalytic Carboxyl Groups of Aspergillus niger .ALPHA.-Glucosidase

In this study, oxidized chitosan grafted cashmere fibers (OCGCFs) were obtained by crosslinking the oxidized chitosan onto cashmere fibers by amide covalent modification. A novel method was developed for the selective oxidation of the C6 primary hydroxyls into carboxyl groups for chitosan. The effect of oxidization reaction parameters of HNO3/H3PO4–NaNO2 mediated oxidation system on the oxidation degree, structure, and properties of chitosan were investigated. The chemical structure of the oxidized chitosan was characterized by solid-state cross-polarization magic angle spinning carbon-13 Nuclear Magnetic Resonance (CP/MAS 13C-NMR), Fourier transform infrared spectroscopy (FT-IR), and its morphology was investigated by scanning electron microscopy (SEM). Subsequently, the effect of the oxidized chitosan grafting on OCGCF was examined, and the physical properties, moisture regain, and antibacterial activity of OCGCFs were also evaluated. The results showed that oxidation of chitosan mostly occurred at the C6 primary hydroxyl groups. Moreover, an oxidized chitosan with 43.5–56.8% carboxyl content was realized by ranging the oxidation time from 30 to 180 min. The resulting OCGCF had a C–N amido bond, formed as a result of the reaction between the primary amines in the cashmere fibers and the carboxyl groups in the oxidized chitosan through the amide reaction. The OCGCF exhibited good moisture regain and remarkable bacteriostasis against both Staphylococcus aureus and Escherichia coli bacteria with its durability.

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THE PROBLEM OF PLASTEIN FORMATION: II. THE CHEMICAL CHANGES INVOLVED IN PLASTEIN FORMATION BY PAPAIN AND BY PEPSIN

Canadian Journal of Research ◽

10.1139/cjr40b-034 ◽

1940 ◽

Vol 18b (9) ◽

pp. 272-280 ◽

Cited By ~ 3

Author(s):

H. B. Collier

Keyword(s):

Enzymatic Hydrolysis ◽

Free Amino ◽

Essential Role ◽

Phenolic Hydroxyl ◽

Carboxyl Groups ◽

Hydroxyl Groups ◽

Chemical Changes ◽

Phenolic Hydroxyl Groups ◽

Hydrolysis Of

It has been confirmed that free amino and carboxyl groups disappear during plastein formation from concentrated proteose by crystalline pepsin. Using papain, the changes are obscured by simultaneous hydrolysis. Enzymatic hydrolysis of the plasteins results in the liberation of free amino and carboxyl groups.Reactive "tyrosine" decreases during plastein formation by either enzyme. The same groups are liberated on enzymatic hydrolysis of the plasteins, in a manner analogous to that which takes place in the hydrolysis of typical proteins.It is concluded that in so far as the changes in amino, carboxyl, and "tyrosine" groups are concerned, the plasteins are similar to typical proteins. It is further suggested that the phenolic hydroxyl groups of tyrosine play an essential role in the structure of the protein molecule.Benzaldehyde was found to have no effect on the formation of plastein from proteose by crystalline pepsin.

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The dissociation constants of the carboxyl and hydroxyl groups in some insoluble and sol-forming polysaccharides

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1946.0029 ◽

1946 ◽

Vol 185 (1003) ◽

pp. 431-447 ◽

Cited By ~ 33

Keyword(s):

Potassium Chloride ◽

Chloride Ions ◽

Wheat Starch ◽

Carboxyl Groups ◽

Hydroxyl Groups ◽

Dissociation Curve ◽

Two Phase ◽

Pectic Acid ◽

Phase Systems ◽

Dissociation Curves

In order to establish the conditions under which the buffering of insoluble substance may most usefully be studied, suspensions of fibre cellulose, hemicellulose and xylan have been examined to determine the relationship between pH and the degree of dissociation of their carboxyl groups. The materials were suspended in normal potassium chloride solution, in order to confine local gradients of hydrion. concentration to the immediate vicinity of each charged buffer group. Under these conditions the dissociation curves are all of the simple Henderson type with a common constant pK = 2·95 (N /100 hydrochloric acid in normal potassium chloride being taken as pH 2 ). Sols of arabic and pectie acid follow the same dissociation curve, showing that the dissociation of the carboxyl groups is not necessarily influenced by the state of aggregation. Within the accuracy of these measurements, uronic and gluconic carboxyls have the same pK . The dissociation of pectic acid departs from the Henderson curve in the same general way as the dissociation curve of maleic acid differs from that of fumaric acid. It is suggested that some of the carboxyls in pectic acid are linked by hydrogen bridges. To a less extent such linkage may also occur in alginic acid below pH 3 when a gel is formed. The pK . for the first stage of acid dissociation of the hydroxyl groups in wheat starch is close to 13·3. The same value was obtained whether potassium hydroxide, calcium hydroxide or barium hydroxide was used. The alkalis were made up in normal solutions of the corresponding chlorides. The same constant holds for alginate within the limits of experimental error. The dissociation in cellulose up to pH 13·5 is much less than in starch. Using a new method based on a determination of the ratio of chloride ions to hydroxyl ions, the dissociations of starch and cellulose were measured in 5N alkali (approximately pH 14·7). The second pK of starch is estimated at roughly 15·0. The cellulose, largely mercerized at this pH, exhibited a dissociation not much less than that of starch, and agreeing closely with the prediction of Neale. An insoluble buffer substance suspended in an electrolyte solution is a two-phase system. The hydrion dissociation can be determined in two-phase systems over a greater pH range than is possible in one-phase systems.

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Irreversible thermoinactivation of glucoamylase from Aspergillus niger and thermostabilization by chemical modification of carboxyl groups

Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology ◽

10.1016/0167-4838(90)90052-h ◽

1990 ◽

Vol 1041 (2) ◽

pp. 111-116 ◽

Cited By ~ 30

Author(s):

Olivier Munch ◽

Denis Tritsch

Keyword(s):

Aspergillus Niger ◽

Chemical Modification ◽

Carboxyl Groups

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The effect of rubber on the mechanical properties of epoxy and carbon fiber (Review)

Kompleksnoe ispolʹzovanie mineralʹnogo syrʹâ/Complex Use of Mineral Resources/Mineraldik shikisattardy Keshendi Paidalanu ◽

10.31643/2020/6445.02 ◽

2020 ◽

Vol 1 (312) ◽

pp. 11-21

Author(s):

M. N. Meiirbekov ◽

◽

M. B. Ismailov ◽

Keyword(s):

Mechanical Properties ◽

Tensile Strength ◽

Compressive Strength ◽

Carbon Fiber ◽

Impact Strength ◽

Yield Strength ◽

Strength Properties ◽

Carboxyl Groups ◽

Published Data ◽

Hydroxyl Groups

The paper presents published data on the effect of rubber elastomers on the strength properties of epoxy resin (ES) and carbon fiber. The introduction of 10% rubbers into ES ED-20 leads to an increase in compressive strength by 50%, tensile strength by 51%, impact strength by 133% and elongation by 128%. The optimal content of rubber with carboxyl groups for the OLDEN mixture was 10-12.5%, while the increase in compressive strength was 48%, impact strength - 73% and elongation - 187%. For DER 331 resin, the study was conducted with two hardeners Piperidine and DETA. The best results for Piperidine hardener were obtained on rubber with hydroxyl groups, with its optimal content of 2.5%, impact strength increased by 170%. For the hardener DETA, the best results were obtained on rubber with carboxyl groups at its optimal content of 10%, the increase in impact strength was 66%. When modifying carbon fiber with rubbers, it leads to a significant increase in the yield strength in tension by 42%, the modulus of elasticity in bending by 63%, and with a slight loss of impact strength.

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One step introduction of the activated carboxyl groups with long aliphatic arm onto hydroxyl groups containing polymers

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19901321 ◽

1990 ◽

Vol 55 (5) ◽

pp. 1321-1325

Author(s):

Luboš Arnold ◽

Jiří Smrt

Keyword(s):

Carboxyl Groups ◽

Hydroxyl Groups ◽

Carboxyl Group ◽

One Step ◽

Nitrophenyl Ester

Bis-N-hydroxysuccinimide ester of 1,10-decanediol bis-succinate (Ia) reacts with hydroxyl groups bearing polymers (Spheron, cellulose, Sephacryl) affording activated carboxyl group containing derivatives IIa. Analogous 4-nitrophenyl group bearing Spheron derivative IIb was prepared starting from bis-4-nitrophenyl ester of 1,10-decanediol bis-succinate (Ib). 3'-O-(4,4'-Dimethoxytriphenylmethyl)-2'-deoxythymidine 5'-(6-amino-1-hexyl)-phosphate (V) was developed as reagent to determine the extent of activated carboxyl groups. Attachment ranging from 3.1-7.3 μmol/g was achieved.

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Substrate Specificity and Subsite Affinities of Crystalline .ALPHA.-Glucosidase from Aspergillus niger.

Agricultural and Biological Chemistry ◽

10.1271/bbb1961.55.2327 ◽

1991 ◽

Vol 55 (9) ◽

pp. 2327-2335 ◽

Cited By ~ 42

Author(s):

Akihiko KITA ◽

Hirokazu MATSUI ◽

Akishige SOMOTO ◽

Atsuo KIMURA ◽

Masuhiro TAKATA ◽

...

Keyword(s):

Aspergillus Niger ◽

Substrate Specificity ◽

Alpha Glucosidase

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TERPENOIDS: V. SENEGENIN: FUNCTIONAL GROUPS AND PART STRUCTURE

Canadian Journal of Chemistry ◽

10.1139/v64-073 ◽

1964 ◽

Vol 42 (3) ◽

pp. 491-501 ◽

Cited By ~ 18

Author(s):

J. J. Dugan ◽

P. De Mayo ◽

A. N. Starratt

Keyword(s):

Functional Groups ◽

Empirical Formula ◽

Carboxyl Groups ◽

Hydroxyl Groups ◽

Carboxyl Group ◽

Secondary Hydroxyl ◽

Part Structure ◽

Oxygen Atoms

Senegenin, the sapogenin from Polygalasenega has been shown to contain chlorine; it has the empirical formula C30OH45O6Cl. The oxygen atoms, contrary to earlier work, are contained in two carboxyl groups and two secondary hydroxyl groups. There is one isolated ethylenic linkage. The environment of the hydroxylic functions and one carboxyl group has been shown to be as in (XI).

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