# Hydroxyl GroupsRecently Published Documents

3461
(FIVE YEARS 924)

## H-INDEX

94
(FIVE YEARS 29)

2021 ◽
Vol 2021 ◽
pp. 1-9
Author(s):
Tongjun Zhang ◽
Shasha Yan ◽
Jianjun Hao ◽
Dehua Li
Keyword(s):

The high-resolution terahertz spectra of the two structural isomers, mannose and galactose, have been measured by terahertz time-domain spectroscopy (THz-TDS) in the range of 0.5–4.0 THz at room temperature. Significant differences between these similar molecules have been found in their THz characteristic spectra, implying that THz-TDS is a powerful tool for identifying isomers. Structural analyses and normal mode calculations of the two systems were performed using solid-state density functional theory (DFT) with the PBE and PW91 density functionals as well as using gas-state DFT with B3LYP hybrid functional. Among these calculations, the solid-state simulated results obtained from the PBE method exhibit a good agreement with the experimentally measured spectra. According to the calculated results of PBE, the observed spectral features were assigned as primarily external lattice translations, deformations, and rotations with lesser contributions due to intramolecular motion of pyranose ring, CH2OH group, and hydroxyl groups.

2021 ◽
Author(s):
Luyi Chen ◽
Yi Liu ◽
Yaoyao Zhou ◽
Linjiang Zhu ◽
Xiaolong Chen

Abstract The α-glucosidase (EC 3.2.1.20) Agl2 produced by Xanthomonas campestris shows high α-glucosyl transfer activity toward alcoholic and phenolic hydroxyl groups. Ethyl vanillin-α-glucoside, a precursor-aroma compound with improved water solubility and thermal stability, can be synthesized through the transglycosylation of ethyl vanillin by Agl2. However, its low ethyl vanillin-α-glucoside yield and ability to hydrolyze ethyl vanillin-α-glucoside limits for industrial applications. Rational design and site-directed mutagenesis were employed to generate three variants of X. campestris α-glucosidase: L145I, S272T and L145I/S272T, which displayed improved transglycosylation activity toward EV The ethyl vanillin-α-glucoside yield of L145I/S272T is the highest and is up to yield 52.41%. Besides, L145I/S272T also remarkably diminished the hydrolysis activity toward the transglycosylation product EVG compared to Agl2. Our rational design based the catalytic mechanism of the α-glucosidase reaction proved to be effective for producing mutants with improved the ratio of transglycosylation/hydrolysis of α-glucosidase, which provides an important theoretical basis for further research on the reaction mechanism of α-glucosidase.

2021 ◽
Author(s):
Fredrick Asogwa ◽
Hitler Louis ◽
Dollars I. Kenthurky ◽
Obieze C. Enudi
Keyword(s):

Abstract The presence of nitrogen atom either on the diene or the dienophile structure gives rise to aza or imino-Diels-Alder reactions (DARs). Among hetero-DARs, imino-dienophiles yields numerous functionalized compounds with numerous biological activities including but not limited to antifungal, antibacterial and enzymatic properties. Density functional theory (DFT) using the B3LYP functional at the 6-31+G (d, p) basis set along with topological studies (QTAIM) were used for the investigation of 10 different (SD1-SD10) DARs which differ in the nature of substituents groups attached to the diene molecule. The study indicates higher electron density and stronger interaction for substituted dienes with the cycloalkanes, furan, carbonyl, and -OH groups. It was observed in the HOMO-LUMO energy differences that the bulky groups; SD3, SD4, and SD6 had destabilization energy of -7.86 and 0.09, -7.88 and 0.10 and -7.50 and -0.014 eV respectively in their HOMO and LUMO levels while the halogen substituted dienes SD1, SD2, and SD5 had -8.20 and -0.32, -8.31 and -0.34 and -8.19 and -0.20 eV respectively. The study showed that synthesis of hetero-nuclear aza-cyclohexene is achieved faster with furan substituent of energy gap 7.534 eV and molecular hardness of 3.677 compared to 7.799 (SD7) -8.100 eV (SD8) and 3.899 (SD7) - 4.050 (SD8) respectively scored by other substituents noting that smaller energy gap leads to higher reactivity. HCOCH3 (SD8) retarded the rate of the reaction by about 58% (unspontaneous) following the calculated Gibb’s free energy of activation while SD6 in the ELF analysis showed complete covalent character against other cycloalkanes that showed dual characteristics of a double and single bond between N-C at their transition states.

2021 ◽
Vol 174 ◽
pp. 107238
Author(s):
Bartłomiej A. Gaweł ◽
Anna Ulvensøen ◽
Katarzyna Łukaszuk ◽
Astrid Marie F. Muggerud ◽
Andreas Erbe
Keyword(s):

2021 ◽
Vol 11 (20) ◽
pp. 9684
Author(s):
Wei Luo ◽
Huiting Lin ◽
Zhihao Wu ◽
Jingteng Chen ◽
Ruiyang Chi ◽
...
Keyword(s):

Plant tannins have the ability to form stable complexes with metal ions, while microporous membranes have low pressure drop and high flux characteristics. Combining these two materials, a new type of tannin-immobilized membrane (M-TAN) adsorption material has been developed. The PA-BWT, PVDF-BWT, CELL -BWT, and PA-AA-BWT were prepared using different types of microporous membranes as substrates, which maintained the porous structure of the membranes and had the characteristics of high flux and fast filtration rate. The surface contact angle and pure water flux analysis showed that the introduction of tannin with multi-phenolic hydroxyl groups increased the hydrophilicity and water flux of the M-TANs. The adsorption performance shows that the adsorption capacity of four kinds of M-TANs for UO22+ is in the order of PA-BWT > PA-AA-BWT > PVDF-BWT > CELL-BWT, and PA-BWT has the largest adsorption capacity of 0.398 mmol g−1. In addition, the adsorption isothermal and kinetic data of PA-BWT were well fitted by the Langmuir equation and the Elovich model, respectively. The negative values of ΔG for UO22+ adsorption on PA-BWT indicated that adsorption is a spontaneous and favorable process. These facts indicate that PA-BWT can be used as a low-cost adsorbent for effective removal of UO22+ from aqueous solutions.

2021 ◽
Vol 4 (4) ◽
Author(s):
I Nyoman Wirata ◽
◽
A.A. Gede Agung ◽
Ni Wayan Arini ◽
Ni Ketut Nuratni
Keyword(s):

Various herbs are used as analgesic, anti-inflammatory, anti-bacterial, anti-fungal, expectorant, anti-plaque and odorant. Sentul is an edible fruit and is also used in traditional medicinal herbs which can treat diarrhea, relieve fever, and as an anthelmintic. Sentul bark methanol extract can inhibit the growth of fungus Candida albican by 39.65%. In addition, the ethyl acetate extract of the sentul leaves also has anti-bacterial activity. The aim of this study is to determine the effect of fractionation with different types of solvents on the phytochemical compounds of Sentul fruit peel in Bali province. This research is an experimental study in a laboratory with qualitative and quantitative analysis models of chemical compounds. This research was carried out from March to August 2021. The research location was carried out in the laboratory of the Faculty of Food Technology, Udayana University. Sample criteria was old Sentul peel, about 30 kilograms. Data was collected based on the results of examinations from the Laboratory of the Faculty of Food Technology, Udayana University which subsequently analyzed qualitatively and descriptively. From several phytochemical compounds, flavonoids, saponins and tannins are aromatic hydroxyl groups that act as antibacterial. Therefore, seen from the highest levels of flavonoids, saponins and tannins, aqua fraction of Sentul ethanol extract is the best treatment with flavanoid levels of 11476.16 mg/100g QE, tannins 88.605 mg/g and saponins 6.862 mg/g.

2021 ◽
Vol 4 (1) ◽
pp. 101-110
Author(s):
Furkan Celtik ◽
Enes Kilic ◽
Mustafa Ozgur Bora ◽
Ekrem Altuncu
Keyword(s):

Polymeric textile cords, steel cords and steel cables are mainly reinforcing materials that are used in tire production. Polymeric textile cords such as Polyester (PEs), Nylon, Aramid and Rayon are commonly treated with bi-functional resorcinol formaldehyde latex (RFL) to obtain desired adhesion to rubber matrix. PEs cords are known as their poor adhesion to both RFL and rubber compounds due to limited reactivity on the surface and poor reaction extent between methylol and hydroxyl groups of RFL. Increasing carboxyl content on PEs surface or in the rubber compound is one of the best strategies to overcome this adhesion problem. Liquid rubbers, which can co-vulcanize with solid rubbers, are also strong alternatives of process oils with their excellent plasticizing effect without deterioration in mechanical properties of the resulting material. Co-vulcanization also improves the stability of this additive and prevents possible bleeding and migration during service life of the tire. In this study, carboxylated grafted liquid isoprene rubber has been incorporated to rubber compound to improve adhesion in PEs-RFL-Rubber ternary system. Rheological and dynamic-mechanical properties of reactive liquid rubber containing tire rubber compounds have been evaluated extensively, as well as H-adhesion behaviour of PEs cord-rubber composite matrix.

2021 ◽
Author(s):
I Nyoman Wirata ◽
A.A. Gede Agung ◽
Ni Wayan Arini ◽
Ni Ketut Nuratni
Keyword(s):

Various herbs are used as analgesic, anti-inflammatory, anti-bacterial, anti-fungal, expectorant, anti-plaque and odorant. Sentul is an edible fruit and is also used in traditional medicinal herbs which can treat diarrhea, relieve fever, and as an anthelmintic. Sentul bark methanol extract can inhibit the growth of fungus Candida albican by 39.65%. In addition, the ethyl acetate extract of the sentul leaves also has anti-bacterial activity. The aim of this study is to determine the effect of fractionation with different types of solvents on the phytochemical compounds of Sentul fruit peel in Bali province. This research is an experimental study in a laboratory with qualitative and quantitative analysis models of chemical compounds. This research was carried out from March to August 2021. The research location was carried out in the laboratory of the Faculty of Food Technology, Udayana University. Sample criteria was old Sentul peel, about 30 kilograms. Data was collected based on the results of examinations from the Laboratory of the Faculty of Food Technology, Udayana University which subsequently analyzed qualitatively and descriptively. From several phytochemical compounds, flavonoids, saponins and tannins are aromatic hydroxyl groups that act as antibacterial. Therefore, seen from the highest levels of flavonoids, saponins and tannins, aqua fraction of Sentul ethanol extract is the best treatment with flavanoid levels of 11476.16 mg/100g QE, tannins 88.605 mg/g and saponins 6.862 mg/g.

2021 ◽
Vol 13 (20) ◽
pp. 3530
Author(s):
Yi Ding Chai ◽
Yean Ling Pang ◽
Steven Lim ◽
Woon Chan Chong ◽
Chin Wei Lai ◽
...
Keyword(s):

In this study, a novel cellulose/Ag/TiO2 nanocomposite was successfully synthesized via the hydrothermal method. The cellulose extracted from oil palm empty fruit bunch (OPEFB) could address the disposal issue created by OPEFB biomass. Characterization studies such as FESEM, EDX, HRTEM, XRD, FTIR, UV–Vis DRS, PL, XPS, and surface analysis were conducted. It was observed that the incorporation of cellulose could hinder the agglomeration, reduce the band gap energy to 3 eV, increase the specific surface area to 150.22 m3/g, and lower the recombination rate of the generated electron-hole pairs compared to Ag/TiO2 nanoparticles. The excellent properties enhance the sonocatalytic degradation efficiency of 10 mg/L Congo red (up to 81.3% after 10 min ultrasonic irradiation) in the presence of 0.5 g/L cellulose/Ag/TiO2 at 24 kHz and 280 W. The improvement of catalytic activity was due to the surface plasmon resonance effect of Ag and numerous hydroxyl groups on cellulose that capture the holes, which delay the recombination rate of the charge carriers in TiO2. This study demonstrated an alternative approach in the development of an efficient sonocatalyst for the sonocatalytic degradation of Congo red.

2021 ◽
Vol 11 (1) ◽
Author(s):
Mounir Benkoulouche ◽
Akli Ben Imeddourene ◽
Louis-Antoine Barel ◽
Dorian Lefebvre ◽
Mathieu Fanuel ◽
...
Keyword(s):

AbstractEnzyme engineering approaches have allowed to extend the collection of enzymatic tools available for synthetic purposes. However, controlling the regioselectivity of the reaction remains challenging, in particular when dealing with carbohydrates bearing numerous reactive hydroxyl groups as substrates. Here, we used a computer-aided design framework to engineer the active site of a sucrose-active $$\mathrm{\alpha }$$ α -transglucosylase for the 1,2-cis-glucosylation of a lightly protected chemically synthesized tetrasaccharide, a common precursor for the synthesis of serotype-specific S. flexneri O-antigen fragments. By targeting 27 amino acid positions of the acceptor binding subsites of a GH70 branching sucrase, we used a RosettaDesign-based approach to propose 49 mutants containing up to 15 mutations scattered over the active site. Upon experimental evaluation, these mutants were found to produce up to six distinct pentasaccharides, whereas only two were synthesized by the parental enzyme. Interestingly, we showed that by introducing specific mutations in the active site of a same enzyme scaffold, it is possible to control the regiospecificity of the 1,2-cis glucosylation of the tetrasaccharide acceptor and produce a unique diversity of pentasaccharide bricks. This work offers novel opportunities for the development of highly convergent chemo-enzymatic routes toward S. flexneri haptens.