scholarly journals Kefiran biopolymer: Evaluation of its physicochemical and biological properties

2018 ◽  
Vol 33 (5) ◽  
pp. 461-478 ◽  
Author(s):  
Hajer Radhouani ◽  
Cristiana Gonçalves ◽  
Fátima R Maia ◽  
Joaquim M Oliveira ◽  
Rui L Reis
Keyword(s):  
Molecular Weight ◽  
Photoelectron Spectroscopy ◽  
Average Molecular Weight ◽  
Structural Features ◽  
Biological Properties ◽  
Health Claims ◽  
Extrusion Force ◽  
Wide Range ◽  
Physicochemical And Biological Properties ◽  
Kefir Grains

Kefiran, an exopolysaccharide produced by lactic acid bacteria, has received a great interest due to a variety of health claims. In this study, we aim to investigate the physicochemical and biological properties of Kefiran polysaccharide extracted from Portuguese kefir grains. The kefir growth rate was about 56% (w/w) at room temperature and the kefir pH after 24 h was about 4.6. The obtained yield of Kefiran polysaccharide extracted from the kefir grains was about 4.26% (w/w). The Kefiran structural features were showed in the 1H nuclear magnetic resonance spectrum. The bands observed in the infrared spectrum confirmed that the Kefiran had a β-configuration; and the X-ray photoelectron spectroscopy analysis confirmed the structure and composition of Kefiran and revealed a C/O atomic ratio of 1.46. Moreover, Kefiran showed an average molecular weight (Mw) of 534 kDa and a number-average molecular weight (Mn) of 357 kDa. Regarding the rheological data obtained, Kefiran showed an interesting adhesive performance accompanied by a pseudoplastic behavior, and the extrusion force of Kefiran was 1 N. Furthermore, Kefiran exhibited a higher resistance to hyaluronidase degradation than hyaluronic acid. Finally, Kefiran showed a lack of cytotoxic response through its ability to support metabolic activity and proliferation of L929 cells, and had no effect on these cells’ morphology. Our research suggested that Kefiran polymer has attractive and interesting properties for a wide range of biomedical applications, such as tissue engineering and regenerative medicine.

scholarly journals Novel Trifluoromethyl Pyrimidinone Compounds With Activity Against Mycobacterium tuberculosis

2021 ◽  
Vol 9 ◽  
Author(s):  
Erik Hembre ◽  
Julie V. Early ◽  
Joshua Odingo ◽  
Catherine Shelton ◽  
Olena Anoshchenko ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Major Change ◽  
Structural Features ◽  
Research Area ◽  
Biological Properties ◽  
Pyridyl Ring ◽  
Pyridyl Group ◽  
Gram Positive Bacteria ◽  
Wide Range ◽  
Cytotoxic Molecules

The identification and development of new anti-tubercular agents are a priority research area. We identified the trifluoromethyl pyrimidinone series of compounds in a whole-cell screen against Mycobacterium tuberculosis. Fifteen primary hits had minimum inhibitory concentrations (MICs) with good potency IC90 is the concentration at which M. tuberculosis growth is inhibited by 90% (IC90 < 5 μM). We conducted a structure–activity relationship investigation for this series. We designed and synthesized an additional 44 molecules and tested all analogs for activity against M. tuberculosis and cytotoxicity against the HepG2 cell line. Substitution at the 5-position of the pyrimidinone with a wide range of groups, including branched and straight chain alkyl and benzyl groups, resulted in active molecules. Trifluoromethyl was the preferred group at the 6-position, but phenyl and benzyl groups were tolerated. The 2-pyridyl group was required for activity; substitution on the 5-position of the pyridyl ring was tolerated but not on the 6-position. Active molecules from the series demonstrated low selectivity, with cytotoxicity against eukaryotic cells being an issue. However, there were active and non-cytotoxic molecules; the most promising molecule had an MIC (IC90) of 4.9 μM with no cytotoxicity (IC50 > 100 μM). The series was inactive against Gram-negative bacteria but showed good activity against Gram-positive bacteria and yeast. A representative molecule from this series showed rapid concentration-dependent bactericidal activity against replicating M. tuberculosis bacilli with ~4 log kill in <7 days. Overall the biological properties were promising, if cytotoxicity could be reduced. There is scope for further medicinal chemistry optimization to improve the properties without major change in structural features.

scholarly journals Chitin, Chitosan, and Submicron-Sized Chitosan Particles Prepared from Scylla serrata Shells

2020 ◽  
Vol 2 (2) ◽  
pp. 139-149
Keyword(s):  
Molecular Weight ◽  
Sodium Tripolyphosphate ◽  
Average Molecular Weight ◽  
Value Added ◽  
Scylla Serrata ◽  
Mud Crab ◽  
Practical Applications ◽  
Degree Of Acetylation ◽  
Wide Range ◽  
Chitin And Chitosan

Extraction of chitin from mud crab (Scylla serrata) shells, involving demineralization and deproteinization, and deacetylation of the extracted chitin to form chitosan were investigated. The mud crab chitin and chitosan were obtained with a good yield (16.8% and 84.7% based on dried weight basis). The physicochemical properties, functional groups, molecular weight, and degree of acetylation of the chitin and chitosan were characterized. The surface morphology, the orientation arrangement of polysaccharide strands, and crystallinity of the chitin and chitosan prepared from the mud crab shells were investigated. SEM, FTIR, and XRD analyses demonstrated that the chitin consists of micron-sized fibrils, belonging to α from with the crystallinity of 60.1%. The chitosan has a viscosity-average molecular weight of 6.83 kDa with the degree of acetylation being 9.6% and the crystallinity of 73.8%. The chitosan was successfully fabricated into submicron-sized particles using top-down ionotropic gelation, microwave, and microemulsion methods, employing sodium tripolyphosphate, potassium persulfate, and glutaraldehyde as reagents, respectively. Overall, the results indicated that the preparation of chitin, chitosan, and submicron-sized chitosan particles from mud crab shells could open the opportunity for the value-added seafood waste to be utilized in a wide range of practical applications.

Synthesis and Properties of a Novel Thermostable Polymer: Fluorinated Polycarbodiimide

1997 ◽  
Vol 9 (4) ◽  
pp. 385-395 ◽  
Author(s):  
Amane Mochizukiy ◽  
Michie Sakamotoy ◽  
Masahiro Yoshiokay ◽  
Yuji Hottay ◽  
Takahiro Fukuokay ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Thermal Decomposition ◽  
Dielectric Constant ◽  
Thermal Properties ◽  
Average Molecular Weight ◽  
Number Average Molecular Weight ◽  
Thermostable Polymer ◽  
Lower Dielectric Constant ◽  
Wide Range ◽  
Solution Polycondensation

A new fluorinated linear polycarbodiimide (F-PCD) was synthesized by solution polycondensation of a new fluorinated diisocyanate monomer, 4″, 4″′-(hexafluoroisopropylidene) bis(4-phenoxyphenyl isocyanate) (HPI) in the presence of 3-methyl-1-phenyl-2-phospholene-1-oxide (PMO). HPI was prepared from 4″, 4″′-(hexafluoroisopropylidene)bis(4-phenoxyaniline) (HPA) by three steps. The reaction of HPA with phenyl chloroformate gave the corresponding carbamate, which upon reaction with trimethylsilylchloride (TMS-Cl)-triethylamine (TEA), followed by thermal decomposition, provided HPI. The polymer having a number average molecular weight up to 8400 was obtained in quantitative yield. Thermal properties were investigated and we found that the polymer has a higher glass transition temperature ( Tg)upto 230 °C, and a lower dielectric constant at 2.98 at 1 MHz than the conventional polycarbodiimides (PCDs). The linear F-PCD was soluble in a wide range of common organic solvents such as toluene and dichloromethane.

scholarly journals A Systematic Study on the Degradation Products Generated from Artificially Aged Microplastics

Polymers ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 1997
Author(s):  
Greta Biale ◽  
Jacopo La Nasa ◽  
Marco Mattonai ◽  
Andrea Corti ◽  
Virginia Vinciguerra ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Molecular Weight ◽  
Degradation Products ◽  
Average Molecular Weight ◽  
Size Exclusion ◽  
Gas Chromatography Mass Spectrometry ◽  
Low Molecular Weight ◽  
Photo Degradation ◽  
Degradation Processes ◽  
Wide Range

Most of the analytical studies focused on microplastics (MPs) are based on the detection and identification of the polymers constituting the particles. On the other hand, plastic debris in the environment undergoes chemical and physical degradation processes leading not only to mechanical but also to molecular fragmentation quickly resulting in the formation of leachable, soluble and/or volatile degradation products that are released in the environment. We performed the analysis of reference MPs–polymer micropowders obtained by grinding a set of five polymer types down to final size in the 857–509 μm range, namely high- and low-density polyethylene, polystyrene (PS), polypropylene (PP), and polyethylene terephthalate (PET). The reference MPs were artificially aged in a solar-box to investigate their degradation processes by characterizing the aged (photo-oxidized) MPs and their low molecular weight and/or highly oxidized fraction. For this purpose, the artificially aged MPs were subjected to extraction in polar organic solvents, targeting selective recovery of the low molecular weight fractions generated during the artificial aging. Analysis of the extractable fractions and of the residues was carried out by a multi-technique approach combining evolved gas analysis–mass spectrometry (EGA–MS), pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS), and size exclusion chromatography (SEC). The results provided information on the degradation products formed during accelerated aging. Up to 18 wt% of extractable, low molecular weight fraction was recovered from the photo-aged MPs, depending on the polymer type. The photo-degradation products of polyolefins (PE and PP) included a wide range of long chain alcohols, aldehydes, ketones, carboxylic acids, and hydroxy acids, as detected in the soluble fractions of aged samples. SEC analyses also showed a marked decrease in the average molecular weight of PP polymer chains, whereas cross-linking was observed in the case of PS. The most abundant low molecular weight photo-degradation products of PS were benzoic acid and 1,4-benzenedicarboxylic acid, while PET had the highest stability towards aging, as indicated by the modest generation of low molecular weight species.

Overview of Enzyme Engineering Towards the Production of Hyaluronic Acid with Tailored Molecular Weight

2021 ◽  
Vol 23 ◽  
Author(s):  
Tahereh Ebrahimi ◽  
Kamran Hosseini ◽  
Hossein Ahangari ◽  
Pourya Gholizadeh ◽  
Vahideh Tarhriz
Keyword(s):  
Molecular Weight ◽  
Hyaluronic Acid ◽  
Critical Role ◽  
Biological Properties ◽  
Research Field ◽  
Enzyme Engineering ◽  
The Body ◽  
Synthesis Process ◽  
Hyaluronan Synthase ◽  
Wide Range

: Hyaluronic acid or hyaluronan (HA) is a natural biopolymer composed of D-glucuronic acid and N-acetylglucosamine units, distributed as a non-sulfated and anionic glycosaminoglycan in important tissues of the body, and is commercially and biologically important. Its biological properties are determined by the molecular weight and dispersity which are suitable for particular medical and cosmetic applications. The synthesis of well-defined and monodisperse HA is still a significant obstacle and an impressive research field for advanced medical applications. High polydispersity by bacterial fermentation, the lack of knowledge of the mechanism required to start and continue the synthesis process, increased cost of raw materials to produce HA, clarification and explanation of factors limiting synthesis in bacterial systems are among the important challenges of hyaluronic acid synthesis. Hyaluronan synthase plays a critical role in HA molecular mass by producing a wide range of HA involved in various biological processes. Hyaluronan biosynthesis has been considered extensively; however, the control of its size and weight during the synthesis process is poorly investigated. This review focuses on these uncharted biochemical details to obtain the uniform chain lengths of Hyaluronan by protein engineering and regulating the function of Hyaluronan synthase.

scholarly journals Self-assembled high molecular weight inulin nanoparticles: Enzymatic synthesis, physicochemical and biological properties

2019 ◽  
Vol 215 ◽  
pp. 160-169 ◽  
Author(s):  
Maira Jiménez-Sánchez ◽  
Rebeca Pérez-Morales ◽  
Francisco M. Goycoolea ◽  
Monika Mueller ◽  
Werner Praznik ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Enzymatic Synthesis ◽  
Biological Properties ◽  
Physicochemical And Biological Properties ◽  
Self Assembled

Can Ultrafiltration Occur with a Hypo-Osmolar Solution in Peritoneal Dialysis?: The Role for ‘Colloid’ Osmosis

1993 ◽  
Vol 85 (4) ◽  
pp. 495-500 ◽  
Author(s):  
Chandra D. Mistry ◽  
Ram Gokal
Keyword(s):  
Molecular Weight ◽  
Peritoneal Dialysis ◽  
Polymer Solution ◽  
Corn Starch ◽  
Average Molecular Weight ◽  
Dialysis Solution ◽  
Wide Range ◽  
Glucose Polymer ◽  
Metabolic Correction

1. In peritoneal dialysis the removal of excess body water (ultrafiltration) is traditionally achieved by means of dialysis solution made hypertonic to plasma by the addition of an osmotic agent. In vitro, the osmotic flow may be directed against the osmolality gradient by using a hypo-osmolar solution, but this phenomenon has not previously been applied to clinical peritoneal dialysis. 2. The ultrafiltration performances of hypo-osmolar dialysis solutions containing a high-molecular-weight glucose polymer (weight average molecular weight 22 000), isolated by fractionation of hydrolysed corn starch, were compared with those of hypertonic glucose solutions over a 12 h exchange in 11 patients well established on continuous ambulatory peritoneal dialysis. 3. Five per cent (272 +1.1 mosmol/kg) and 7.5% (277 + 2.0 mosmol/kg) glucose polymer solutions produced net ultrafiltration of 243 +53 and 526 +59 ml that were significantly greater than the ultrafiltration of −48 +96 and 223 +84 ml associated with 1.36% (339 +1.9 mosmol/kg) and 2.27% (393 +3.2 mosmol/kg) glucose solutions, respectively. The net ultrafiltration with 10% glucose polymer (284 +2.0 mosmol/kg) and 3.86% glucose (482 + 1.6 mosmol/kg) solutions were similar (699 +48 versus 708 +82 ml). 4. The transperitoneal absorption of glucose polymer was substantially lower than that of glucose solutions as was the potential calorie load per millilitre of ultrafiltrate. 5. The addition of 0.35% glucose (molecular weight 180) to 7.5% glucose polymer solution raised the dialysate osmolality to an iso-osmolar level (299 +0.8 mosmol/kg) and produced ultrafiltration which was 29% greater than with 7.5% glucose polymer solution alone. 6. The demonstration of ultrafiltration with hypo-osmolar dialysate represents an important advance towards the formulation of a physiological iso-osmolar dialysis solution, which may have long-term benefits over the conventional hypertonic solutions. The iso-osmolar combination of ‘colloid’ and ‘crystalloid’ osmotic agents looks promising with a potential for a wide range of ultrafiltration capabilities as well as metabolic correction.

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