scholarly journals Enhanced Mechanical Properties by Ionomeric Complexation in Interpenetrating Network Hydrogels of Hydrolyzed Poly (N-vinyl Formamide) and Polyacrylamide

Gels ◽  
2021 ◽  
Vol 7 (3) ◽  
pp. 80
Author(s):  
Joseph M. Scalet ◽  
Tiffany C. Suekama ◽  
Jeayoung Jeong ◽  
Stevin H. Gehrke
Keyword(s):  
Mechanical Performance ◽  
Interpenetrating Network ◽  
Chemical Structures ◽  
Ph Values ◽  
Similar Chemical ◽  
Ionic Complexation ◽  
Order Of Magnitude ◽  
Failure Properties ◽  
Hydrolysis Of ◽  
Minimal Phase

Tough hydrogels were made by hydrolysis of a neutral interpenetrating network (IPN) of poly (N-vinyl formamide) PNVF and polyacrylamide (PAAm) networks to form an IPN of polyvinylamine (PVAm) and poly (acrylic acid) (PAAc) capable of intermolecular ionic complexation. Single network (SN) PAAm and SN PNVF have similar chemical structures, parameters and physical properties. The hypothesis was that starting with neutral IPN networks of isomeric monomers that hydrolyze to comparable extents under similar conditions would lead to formation of networks with minimal phase separation and maximize potential for charge–charge interactions of the networks. Sequential IPNs of both PNVF/PAAm and PAAm/PNVF were synthesized and were optically transparent, an indication of homogeneity at submicron length scales. Both IPNs were hydrolyzed in base to form PVAm/PAAc and PAAc/PVAm IPNs. These underwent ~5-fold or greater decrease in swelling at intermediate pH values (3–6), consistent with the hypothesis of intermolecular charge complexation, and as hypothesized, the globally neutral, charge-complexed gel states showed substantial increases in failure properties upon compression, including an order of magnitude increases in toughness when compared to their unhydrolyzed states or the swollen states at high or low pH values. There was no loss of mechanical performance upon repeated compression over 95% strain.

scholarly journals Synthesis and Biological Activity of New Brassinosteroid Analogs of Type 24-Nor-5β-Cholane and 23-Benzoate Function in the Side Chain

2021 ◽  
Vol 22 (9) ◽  
pp. 4808
Author(s):  
Nitza Soto ◽  
Karoll Ferrer ◽  
Katy Díaz ◽  
César González ◽  
Lautaro Taborga ◽  
...  
Keyword(s):  
Good Alternative ◽  
Positive Control ◽  
Starting Material ◽  
Chemical Structures ◽  
High Reaction ◽  
Similar Chemical ◽  
Synthetic Procedure ◽  
Hyodeoxycholic Acid ◽  
External Stresses

Brassinosteroids are polyhydroxysteroids that are involved in different plants’ biological functions, such as growth, development and resistance to biotic and external stresses. Because of its low abundance in plants, much effort has been dedicated to the synthesis and characterization of brassinosteroids analogs. Herein, we report the synthesis of brassinosteroid 24-nor-5β-cholane type analogs with 23-benzoate function and 22,23-benzoate groups. The synthesis was accomplished with high reaction yields in a four-step synthesis route and using hyodeoxycholic acid as starting material. All synthesized analogs were tested using the rice lamina inclination test to assess their growth-promoting activity and compare it with those obtained for brassinolide, which was used as a positive control. The results indicate that the diasteroisomeric mixture of monobenzoylated derivatives exhibit the highest activity at the lowest tested concentrations (1 × 10−8 and 1 × 10−7 M), being even more active than brassinolide. Therefore, a simple synthetic procedure with high reaction yields that use a very accessible starting material provides brassinosteroid synthetic analogs with promising effects on plant growth. This exploratory study suggests that brassinosteroid analogs with similar chemical structures could be a good alternative to natural brassinosteroids.

scholarly journals β-Glucosidase Activity of Lactiplantibacillus plantarum UNQLp 11 in Different Malolactic Fermentations Conditions: Effect of pH and Ethanol Content

Fermentation ◽  
2021 ◽  
Vol 7 (1) ◽  
pp. 22
Author(s):  
Natalia S. Brizuela ◽  
Marina Arnez-Arancibia ◽  
Liliana Semorile ◽  
María Ángeles Pozo-Bayón ◽  
Bárbara M. Bravo-Ferrada ◽  
...  
Keyword(s):  
Pinot Noir ◽  
Gas Chromatography Mass Spectrometry ◽  
Red Wines ◽  
Ph Values ◽  
Glucosidase Activity ◽  
Sorptive Extraction ◽  
Ethanol Content ◽  
Volatile Precursors ◽  
Hydrolysis Of ◽  
High Ethanol

Lactiplantibacillus plantarum strain UNQLp 11 is a lactic acid bacterium with the potential to carry out malolactic fermentation (MLF) in red wines. Recently, the complete genome of UNQLp 11 was sequenced and this strain possesses four loci of the enzyme β-glucosidase. In order to demonstrate that these glucosidase enzymes could be functional under harsh wine conditions, we evaluated the hydrolysis of p-nitrophenyl-β-D-glucopyranoside (p-NPG) in synthetic wine with different ethanol contents (0%, 12%, and 14% v/v) and at different pH values (3.2, 3.5, and 3.8). Then, the hydrolysis of precursor n-octyl β-D-glucopyranoside was analyzed in sterile Pinot Noir wine (containing 14.5% v/v of ethanol, at different pH values) by headspace sorptive extraction gas chromatography-mass spectrometry (HSSE-GC/MS). The hydrolysis of p-NPG showed that β-glucosidase activity is very susceptible to low pH but induced in the presence of high ethanol content. Furthermore, UNQLp 11 was able to release the glycosilated precursor n-octyl, during MLF to a greater extent than a commercial enzyme. In conclusion, UNQLp 11 could improve the aromatic profile of the wine by the release of volatile precursors during MLF.

Preparation and structural analysis of (±)-threo-ritalinic acid

2013 ◽  
Vol 69 (11) ◽  
pp. 1225-1228 ◽  
Author(s):  
Sara Wyss ◽  
Irmgard A. Werner ◽  
W. Bernd Schweizer ◽  
Simon M. Ametamey ◽  
Selena Milicevic Sephton
Keyword(s):  
Methyl Ester ◽  
Free Acid ◽  
Nmr Analysis ◽  
Intermolecular Hydrogen Bonds ◽  
X Ray ◽  
X Ray Crystallography ◽  
Ph Values ◽  
Ritalinic Acid ◽  
Methyl Phenidate ◽  
Hydrolysis Of

Hydrolysis of the methyl ester (±)-threo-methyl phenidate afforded the free acid in 40% yield,viz.(±)-threo-ritalinic acid, C13H17NO2. Hydrolysis and subsequent crystallization were accomplished at pH values between 5 and 7 to yield colourless prisms which were analysed by X-ray crystallography. Crystals of (±)-threo-ritalinic acid belong to theP21/nspace group and form intermolecular hydrogen bonds. An antiperiplanar disposition of the H atoms of the (HOOC—)CH—CHpygroup (py is pyridine) was found in both the solid (diffraction analysis) and solution state (NMR analysis). It was also determined that (±)-threo-ritalinic acid conforms to the minimization of negativegauche+–gauche−interactions.

scholarly journals Phosphatase synthesis in Klebsiella (Aerobacter) aerogenes growing in continuous culture

1972 ◽  
Vol 127 (1) ◽  
pp. 87-96 ◽  
Author(s):  
P. G. Bolton ◽  
A. C. R. Dean
Keyword(s):  
Alkaline Phosphatase ◽  
Acid Phosphatase ◽  
Continuous Culture ◽  
Activity Profile ◽  
Glucose Effect ◽  
Ph Values ◽  
Nitrophenyl Phosphate ◽  
Wide Range ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of

1. Phosphatase synthesis was studied in Klebsiella aerogenes grown in a wide range of continuous-culture systems. 2. Maximum acid phosphatase synthesis was associated with nutrient-limited, particularly carbohydrate-limited, growth at a relatively low rate, glucose-limited cells exhibiting the highest activity. Compared with glucose as the carbon-limiting growth material, other sugars not only altered the activity but also changed the pH–activity profile of the enzyme(s). 3. The affinity of the acid phosphatase in glucose-limited cells towards p-nitrophenyl phosphate (Km 0.25–0.43mm) was similar to that of staphylococcal acid phosphatase but was ten times greater than that of the Escherichia coli enzyme. 4. PO43−-limitation derepressed alkaline phosphatase synthesis but the amounts of activity were largely independent of the carbon source used for growth. 5. The enzymes were further differentiated by the effect of adding inhibitors (F−, PO43−) and sugars to the reaction mixture during the assays. In particular, it was shown that adding glucose, but not other sugars, stimulated the rate of hydrolysis of p-nitrophenyl phosphate by the acid phosphatase in carbohydrate-limited cells at low pH values (<4.6) but inhibited it at high pH values (>4.6). Alkaline phosphatase activity was unaffected. 6. The function of phosphatases in general is discussed and possible mechanisms for the glucose effect are outlined.

Molecular Motion Analysis of 5CB in PDLCs Using Solid-State 13C NMR Relaxation Spectroscopy

1993 ◽  
Vol 47 (7) ◽  
pp. 933-941 ◽  
Author(s):  
Karen L. Buchert ◽  
Jack L. Koenig ◽  
Shi-Qing Wang ◽  
John L. West
Keyword(s):  
Liquid Crystal ◽  
Solid State ◽  
Polymer Matrix ◽  
Nmr Relaxation ◽  
Domain Size ◽  
Chemical Structures ◽  
Similar Chemical ◽  
Polymer Dispersed ◽  
Submicron Droplets ◽  
Significant Change

In samples of polymer-dispersed liquid crystals (PDLCs), submicron droplets of liquid crystal reside within a polymer matrix. By the use of the cross polarization technique for solid-state 13C NMR spectroscopy, the NMR spectrum of the liquid crystal can be obtained without interference from the polymer spectrum, even though the two materials have some similar chemical structures. Both 13C T1 and 13C T1 ρ relaxation experiments were performed on a PDLC system of 5CB in epoxy as a function of 5CB domain size. The 13C T1 relaxation constants and the localized motions they measure showed no significant change over the liquid crystal domain size studied. However, the 13C T1 ρ relaxation constants and the segmental motions of molecules they measure revealed a significant change over the liquid crystal domain size studied. Therefore, the 13C T1 ρ values can be used to determine the change in mobility of the molecular segments of the SCB molecules resulting from increased interaction between the liquid crystal and the polymer matrix and to further understand the importance of the molecular motions of the liquid crystal in the switching phenomenon for PDLC materials.

pH Effects in trypsin catalysis

1969 ◽  
Vol 47 (21) ◽  
pp. 4021-4029 ◽  
Author(s):  
H. P. Kasserra ◽  
K. J. Laidler
Keyword(s):  
Complex Formation ◽  
Ph Dependence ◽  
Specific Rotation ◽  
Ph Effects ◽  
Ph Values ◽  
A Value ◽  
Available Information ◽  
Hydrolysis Of ◽  
Substrate Concentrations ◽  
Covalent Complex

A kinetic study has been made of the trypsin-catalyzed hydrolysis of N-benzoyl-L-alanine methyl ester, at pH values ranging from 6 to 10. The substrate concentrations varied from 1.7 × 10−3 to 4.3 × 10−2 M. From the rates were calculated, at each pH, values of [Formula: see text] (corresponding to [Formula: see text]), [Formula: see text] (corresponding to [Formula: see text]) and [Formula: see text] The specific levorotation of trypsin was measured and found to vary with pH in the pH region 5–11, the change in specific rotation following the ionization of a single group with pK(app) of 9.4. At pH 11 the specific rotation of trypsin, its zymogen, and its phosphorylated derivative were approximately the same, suggesting similar conformations for all three forms of the protein.The kinetic results on the acid side were very similar to those obtained by other investigators for chymotrypsin; they imply that there is a group of [Formula: see text] in the free enzyme, presumably the imidazole function of a histidine residue, and that this group is involved in acylation and deacylation, which can only occur if it is unprotonated. The behavior on the basic side was found to be different from that with chymotrypsin revealing a decrease in [Formula: see text] at high pH corresponding to a value of [Formula: see text] whereas [Formula: see text] showed sigmoid pH-dependence. An interpretation of these results that is consistent with all available information is that a group of [Formula: see text] (presumably the —NH3+ function of the terminal isoleucine) controls the conformation and thereby the activity of the enzyme at different stages of complex formation. In contrast to chymotrypsin, the pK of this ionizing group appears to be generally lowered by covalent complex formation between trypsin and its substrates.

scholarly journals Competitive cocrystallization and its application in the separation of flavonoids

IUCrJ ◽  
2021 ◽  
Vol 8 (2) ◽  
pp. 195-207
Author(s):  
Yanming Xia ◽  
Yuanfeng Wei ◽  
Hui Chen ◽  
Shuai Qian ◽  
Jianjun Zhang ◽  
...  
Keyword(s):  
Free Energy ◽  
Formation Constant ◽  
Energy Gap ◽  
Hirshfeld Surface ◽  
Methanol Solution ◽  
Model Compounds ◽  
Electronic Density ◽  
Chemical Structures ◽  
Similar Chemical ◽  
Interaction Contribution

Recently, cocrystallization has been widely employed to tailor physicochemical properties of drugs in the pharmaceutical field. In this study, cocrystallization was applied to separate natural compounds with similar structures. Three flavonoids [baicalein (BAI), quercetin (QUE) and myricetin (MYR)] were used as model compounds. The coformer caffeine (CAF) could form cocrystals with all three flavonoids, namely BAI–CAF (cocrystal 1), QUE–CAF (cocrystal 2) and MYR–CAF (cocrystal 3). After adding CAF to methanol solution containing MYR and QUE (or QUE and BAI), cocrystal 3 (or cocrystal 2) preferentially formed rather than cocrystal 2 (or cocrystal 1), indicating that flavonoid separation could be achieved by competitive cocrystallization. After co-mixing the slurry of two flavonoids with CAF followed by centrifugation, the resolution ratio that could be achieved was 70–80% with purity >90%. Among the three cocrystals, cocrystal 3 showed the lowest formation constant with a negative Gibbs free energy of nucleation and the highest energy gap. Hirshfeld surface analysis and density of states analysis found that cocrystal 3 had the highest strong interaction contribution and the closest electronic density, respectively, followed by cocrystal 2 and cocrystal 1, suggesting CAF could competitively form a cocrystal with MYR much more easily than QUE and BAI. Cocrystallization is a promising approach for green and effective separation of natural products with similar chemical structures.

scholarly journals Dinucleoside polyphosphates act as 5’-RNA caps in Escherichia coli

2019 ◽  
Author(s):  
Oldřich Hudeček ◽  
Roberto Benoni ◽  
Martin Culka ◽  
Martin Hubálek ◽  
Lubomír Rulíšek ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Rna Stability ◽  
E Coli ◽  
Chemical Structures ◽  
Additional Layer ◽  
Similar Chemical ◽  
Decapping Enzyme ◽  
Almost All ◽  
Dinucleoside Polyphosphates ◽  
Rna Caps

Dinucleoside polyphosphates (NpnNs), discovered more than 50 years ago,1 are pleiotropic molecules present in almost all types of cells.2 It has been shown that their intracellular concentration can under stress conditions increase from the µM to mM range 2,3. However, the cellular roles and mechanisms of action of NpnNs are still speculative4,5. They have never been considered as part of the RNA, even though they have similar chemical structures as already known RNA caps, such as the nicotinamide adenine dinucleotide (NAD)6-8 and 7-methylguanylate cap9. Here, we show that both methylated and non-methylated Npn Ns serve as RNA caps in Escherichia coli (E. coli). NpnNs are excellent substrates for T7 and E. coli RNA polymerases (RNAP) and efficiently initiate transcription. Further, we demonstrate that the E. coli decapping enzyme RNA 5’ pyrophosphohydrolase (RppH) is able to remove the NpnNs-cap from the RNA. RppH was, however, not able to cleave the methylated forms of the NpnN-caps, suggesting that the methylation adds an additional layer to the RNA stability regulation. Our work introduces an original perspective on the chemical structure of RNA in prokaryotes and the function of RNA caps. This is the first evidence that small molecules like NpnNs can act in cells via their incorporation into RNA and influence the cellular metabolism.

scholarly journals Effects of Petroleum-Based Oils as Dispersing Aids on Physicochemical Characteristics of Magnetorheological Elastomers

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7026
Author(s):  
Norizatie Muhammad Zaki ◽  
Nurul Azhani Yunus ◽  
Muhamad Shakir Yusoff ◽  
Saiful Amri Mazlan ◽  
Siti Aishah Abdul Aziz ◽  
...  
Keyword(s):  
Magnetic Particles ◽  
Physicochemical Characteristics ◽  
Magnetorheological Elastomers ◽  
Weight Percentage ◽  
Chemical Structures ◽  
Microstructure Observation ◽  
Curing Characteristics ◽  
Similar Chemical ◽  
Low Performance ◽  
Light Mineral

This paper investigated the effects of petroleum-based oils (PBOs) as a dispersing aid on the physicochemical characteristics of natural rubber (NR)-based magnetorheological elastomers (MREs). The addition of PBOs was expected to overcome the low performance of magnetorheological (MR) elastomers due to their inhomogeneous dispersion and the mobility of magnetic particles within the elastomer matrix. The NR-based MREs were firstly fabricated by mixing the NR compounds homogeneously with different ratios of naphthenic oil (NO), light mineral oil (LMO), and paraffin oil (PO) to aromatic oil (AO), with weight percentage ratios of 100:0, 70:30, 50:50, and 30:70, respectively. From the obtained results, the ratios of NO mixed with low amounts of AO improved the material physicochemical characteristics, such as thermal properties. Meanwhile, LMO mixed the AO led to the best results for curing characteristics, microstructure observation, and magnetic properties of the MREs. We found that the LMO mixed with a high content of AO could provide good compatibility between the rubber molecular and magnetic particles due to similar chemical structures, which apparently enhance the physicochemical characteristics of MREs. In conclusion, the 30:70 ratio of LMO:AO is considered the preferable dispersing aid for MREs due to structural compounds present in the oil that enhance the physicochemical characteristics of the NR-based MREs.

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