The Effect of Chemical Modification with Pyromellitic Anhydride on Structure, Function, and Thermal Stability of Horseradish Peroxidase

Abstract The cellulose and starch present in the avocado seed can be chemically modified to obtain biofillers with fire retarding characteristics. The resulting composites could be used as substitute of the corresponding halogenated composites. For this, the avocado seed was first washed, dehydrated and pulverized, and thereafter, chemically modified with phosphoric acid in the presence of urea. This was studied using infrared spectroscopy, nuclear magnetic resonance and X-Ray photoelectron spectroscopy, in order to determine the resulting chemical structure and confirm the presence of the proposed functional groups. In addition, scanning electron microscopy and elemental analysis were used, respectively, to establish the resulting morphological changes, as well as the elements present on the surface of the modified material. Thermogravimetric analysis was also carried out in order to establish the thermal stability of the material and predict the effect on the flame retardancy due to the mentioned chemical modification. Further tests established that the obtained modified structure and morphology of the avocado seed was highly dependent on the method used to dehydrate the pulverized avocado seed. It was also determined that chemical modification greatly increased the thermal stability of the avocado seed in air atmosphere. The flame-retardant effect of the modified avocado seed was assessed in polyethylene/ethylene-vinyl-acetate (PE/EVA) composites via cone calorimeter tests. These results showed that the modified avocado seed decreased the peak of the heat release rate (pHRR) by 50% and the total heat released (THR) by 15%. This phosphated avocado seed could be a good option as a renewable biofiller for polymer composites with enhanced flame-retardant properties.

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Improvement of the mechanical property and thermal stability of polypropylene/recycled rubber composite by chemical modification and physical blending

Scientific Reports ◽

10.1038/s41598-020-59191-0 ◽

2020 ◽

Vol 10 (1) ◽

Cited By ~ 1

Author(s):

Tai-Chin Chiang ◽

Huan-Li Liu ◽

Lung-Chang Tsai ◽

Tao Jiang ◽

Ning Ma ◽

...

Keyword(s):

Mechanical Property ◽

Thermal Stability ◽

Chemical Modification ◽

Rubber Composite ◽

Recycled Rubber ◽

Physical Blending ◽

Thermal Stability Of

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General Characteristics of the Changes in the Thermal Stability of Proteins and Enzymes After the Chemical Modification of Their Functional Groups

Russian Chemical Reviews ◽

10.1070/rc1984v053n11abeh003141 ◽

1984 ◽

Vol 53 (11) ◽

pp. 1078-1100 ◽

Cited By ~ 9

Author(s):

G D Kutuzova ◽

N N Ugarova ◽

Ilya V Berezin

Keyword(s):

Thermal Stability ◽

Chemical Modification ◽

Functional Groups ◽

Thermal Stability Of

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Consensus mutagenesis reveals that non-helical regions influence thermal stability of horseradish peroxidase

Biochimie ◽

10.1016/j.biochi.2008.04.009 ◽

2008 ◽

Vol 90 (9) ◽

pp. 1389-1396 ◽

Cited By ~ 6

Author(s):

Barry J. Ryan ◽

Mary J. O'Connell ◽

Ciarán Ó'Fágáin

Keyword(s):

Thermal Stability ◽

Horseradish Peroxidase ◽

Thermal Stability Of

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Chemical modification results in hyperactivation and thermostabilization ofFusarium solaniglucoamylase

Canadian Journal of Microbiology ◽

10.1139/w06-094 ◽

2007 ◽

Vol 53 (2) ◽

pp. 177-185 ◽

Cited By ~ 13

Author(s):

Haq Nawaz Bhatti ◽

M. Hamid Rashid ◽

Muhammad Asgher ◽

Rakhshanda Nawaz ◽

A.M. Khalid ◽

...

Keyword(s):

Thermal Stability ◽

Chemical Modification ◽

Soluble Starch ◽

Water Soluble ◽

Chemically Modified ◽

Free Energy Of Activation ◽

Enthalpy Of Activation ◽

Specificity Constant ◽

Modified Forms ◽

Thermal Stability Of

Chemical modification of carboxyl groups of glucoamylase from a mesophilic fungus, Fusarium solani , was carried out using ethylenediamine as nucleophile in the presence of water-soluble 1-ethyl-3(3-dimethylaminopropyl)carbodiimide. Modification brought about a dramatic enhancement of catalytic activity and thermal stability of glucoamylase. Temperature and pH optima of ethylenediamine-coupled glucoamylase (ECG) increased as compared with those of native enzyme. The specificity constant (kcat/Km) of native, ECG-2, ECG-11, and ECG-17 was 136, 173, 225, and 170, respectively, at 55 °C. The enthalpy of activation (ΔH*) and free energy of activation (ΔG*) for soluble starch hydrolysis were lower for the chemically modified forms. All of the modified forms werestable at higher temperatures and possessed high ΔG* against thermal unfolding. The effects of α-chymotrypsin and subtilisin on the modified forms were activating as compared with native. Moreover, denaturation of ECG-2, ECG-11, and ECG-17 in urea at 4 mol·L–1also showed an activation trend. A possible explanation for the thermal denaturation of native and increased thermal stability of ECG-2, ECG-11, and ECG-17 at higher temperatures is also discussed.

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