Degree of Polymerization of Glucan Chains Shapes the Structure Fluctuations and Melting Thermodynamics of a Cellulose Microfibril

2012 ◽  
Vol 116 (28) ◽  
pp. 8074-8083 ◽  
Author(s):  
Rakwoo Chang ◽  
Adam S. Gross ◽  
Jhih-Wei Chu
Keyword(s):  
Cellulose Microfibril ◽  
Degree Of Polymerization ◽  
Melting Thermodynamics

The Pattern of Acetylation Defines the Priming Activity of Chitosan Tetramers

2019 ◽  
Author(s):  
Sven Basa ◽  
Malathi Nampally ◽  
Talita Honorato ◽  
Subha Narayan Das ◽  
Appa Rao Podile ◽  
...  
Keyword(s):  
Biological Activity ◽  
Degree Of Polymerization ◽  
Chitosan Oligosaccharides ◽  
Degree Of Acetylation ◽  
Bona Fide ◽  
First Time ◽  
Priming Activity

The biological activity of chitosans depends on their degree of polymerization (DP) and degree of acetylation (DA). However, information could also be carried by the pattern of acetylation (PA): the sequence of <i>β</i>-1,4-linked glucosamine (deacetylated/D) and <i>N</i>-acetylglucosamine (acetylated/A) units. To address this hypothesis, we prepared partially-acetylated chitosan oligosaccharides from a chitosan polymer (DA=35%, DP<sub>w</sub>=905) using recombinant chitosan hydrolases with distinct substrate and cleavage specificities. The mixtures were separated into fractions DP4–DP12, which were tested for elicitor and priming activities in rice cells. We confirmed that both activities were influenced by DP, <a>but also observed apparent DA-dependent priming activity, with the ADDD+DADD fraction proving remarkably effective</a>. We then compared all four mono-acetylated tetramers prepared using different chitin deacetylases and observed significant differences in priming activity. This demonstrates for the first time that PA influences the biological activity of chitosans, which can now be recognized as <i>bona fide</i> information-carrying molecules

The Pattern of Acetylation Defines the Priming Activity of Chitosan Tetramers

2019 ◽  
Author(s):  
Sven Basa ◽  
Malathi Nampally ◽  
Talita Honorato ◽  
Subha Narayan Das ◽  
Appa Rao Podile ◽  
...  
Keyword(s):  
Biological Activity ◽  
Degree Of Polymerization ◽  
Chitosan Oligosaccharides ◽  
Degree Of Acetylation ◽  
Bona Fide ◽  
First Time ◽  
Priming Activity

The biological activity of chitosans depends on their degree of polymerization (DP) and degree of acetylation (DA). However, information could also be carried by the pattern of acetylation (PA): the sequence of <i>β</i>-1,4-linked glucosamine (deacetylated/D) and <i>N</i>-acetylglucosamine (acetylated/A) units. To address this hypothesis, we prepared partially-acetylated chitosan oligosaccharides from a chitosan polymer (DA=35%, DP<sub>w</sub>=905) using recombinant chitosan hydrolases with distinct substrate and cleavage specificities. The mixtures were separated into fractions DP4–DP12, which were tested for elicitor and priming activities in rice cells. We confirmed that both activities were influenced by DP, <a>but also observed apparent DA-dependent priming activity, with the ADDD+DADD fraction proving remarkably effective</a>. We then compared all four mono-acetylated tetramers prepared using different chitin deacetylases and observed significant differences in priming activity. This demonstrates for the first time that PA influences the biological activity of chitosans, which can now be recognized as <i>bona fide</i> information-carrying molecules

Degree of Conversion of Light Cured Resin Cements Polymerized under Two Thicknesses of Different Lithium Silicate Ceramics

2020 ◽  
Author(s):  
Mohamed Abdel Rahman Maraghy
Keyword(s):  
Degree Of Polymerization ◽  
Resin Cement ◽  
Lithium Silicate ◽  
Resin Cements ◽  
Ceramic Disc ◽  
Ceramic Disk ◽  
The Difference ◽  
Light Cure Unit ◽  
Glass Slab ◽  
Finger Pressure

Objective: To show the consequence of two thicknesses of ceramic on the polymerization of resin cement light cured when three different lithium silicate ceramics were used. Materials and Methods: 42 ceramic slices were prepared from three types of ceramics, Emax CAD, Celtra Duo CAD and Vita suprinity CAD (n=14). They were further divided into two subgroups according to thicknesses into sub group thickness 0.5mm and sub group thickness 1mm (n=7). Teflon moulds were fabricated with specific dimensions, where the ceramic disc was placed followed by light cured resin cement Bisco choice 2 veneer and a glass slab with finger pressure applied. Curing with Ascent® PX LED light cure unit for 20 seconds took place, where the tip placed over the ceramic sample directly. Cement film was then separated from the ceramic disk and subjected to analysis by Fourier Transform Infrared Spectroscope. Uncured cement samples were also subjected to analysis. Results: Celtra DUO CAD ceramic showed higher degree of polymerization that of Emax and Vita suprinity while the difference between Emax and Suprinity on the degree of polymerization was not significant. Also, ceramic thicknesses had a significant effect on the degree of polymerization of the resin cement. Conclusion: Thickness of ceramics up to 1mm affects the polymerization of resin cement significantly.

Properties and Applications of Modified Bacterial Cellulose-Based Materials

2020 ◽  
Vol 16 ◽  
Author(s):  
Munair Badshah ◽  
Hanif Ullah ◽  
Fazli Wahid ◽  
Taous Khan
Keyword(s):  
Surface Modification ◽  
Bacterial Cellulose ◽  
Degree Of Polymerization ◽  
Biomedical Science ◽  
Hydroxyl Groups ◽  
Market Demand ◽  
Ideal Candidate ◽  
Fibrous Network ◽  
Potential Applications ◽  
Surface Modification Techniques

Background: Bacterial cellulose (BC) is purest form of cellulose as it is free from pactin, lignin, hemicellulose and other active constituents associated with cellulose derived from plant sources. High biocompatibility and easy molding into desired shape make BC an ideal candidate for applications in biomedical field such as tissue engineering, wound healing and bone regeneration. In addition to this, BC has been widely studied for applications in the delivery of proteins and drugs in various forms via different routes. However, BC lacks therapeutic properties and resistance to free movement of small molecules i.e., gases and solvents. Therefore, modification of BC is required to meet the research ad market demand. Methods: We have searched the updated data relevant to as-synthesized and modified BC, properties and applications in various fields using Web of science, Science direct, Google and PubMed. Results: As-synthesized BC possesses properties such as high crystallinity, well organized fibrous network, higher degree of polymerization, and ability of being produced in swollen form. The large surface area with abundance of free accessible hydroxyl groups makes BC an ideal candidate for carrying out surface functionalization to enhance its features. The various reported surface modification techniques including, but not limited to, are amination, methylation and acetylation. Conclusion: In this review, we have highlighted various approaches made for BC surface modification. We have also reported enhancement in the properties of modified BC and potential applications in different fields ranging from biomedical science to drug delivery and paper-making to various electronic devices.

Polymerization of acrylonitrile initiated by peroxomonosulphate-thiols redox systems

1990 ◽  
Vol 55 (8) ◽  
pp. 2001-2007
Author(s):  
Gurusamy Manivannan ◽  
Pichai Maruthamuthu
Keyword(s):  
Ionic Strength ◽  
Thermodynamic Parameters ◽  
Thermal Polymerization ◽  
Reaction Scheme ◽  
Degree Of Polymerization ◽  
Reducing Agent ◽  
Redox Systems ◽  
Temperature Range ◽  
Rate Of Polymerization

Aqueous thermal polymerization of acrylonitrile (AN) initiated by peroxomonosulphate (HSO5-, PMS)-thiolactic acid (TLA) and PMS-thiomalic acid (TMA) redox systems has been carried out in the temperature range 30-50 °C. The effect of concentration of monomer, initiator, reducing agent, H+, and ionic strength on rate of polymerization, Rp, has been investigated under deaerated conditions. The Rp has been found to depend on, Rp ~ [AN]01.5 [PMS]0.5 [TLA]0.5 in PMS-TLA system and, Rp ~ [AN]02.0 [PMS]1.0 [TMA]0 in PMS-TMA system. The degree of polymerization (Xn) values and thermodynamic parameters have been evaluated. Suitable reaction scheme has been proposed and expressions for Rp and Xn have been obtained.

Influence of an exocyclic guanine adduct on the thermal stability, conformation, and melting thermodynamics of a DNA duplex

Biochemistry ◽  
1992 ◽  
Vol 31 (48) ◽  
pp. 12096-12102 ◽  
Author(s):  
G. Eric Plum ◽  
Arthur P. Grollman ◽  
Frances Johnson ◽  
Kenneth J. Breslauer
Keyword(s):  
Thermal Stability ◽  
Dna Duplex ◽  
Melting Thermodynamics

scholarly journals Brewers’ spent grain as substrate for dextran biosynthesis by Leuconostoc pseudomesenteroides DSM20193 and Weissella confusa A16

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Prabin Koirala ◽  
Ndegwa Henry Maina ◽  
Hanna Nihtilä ◽  
Kati Katina ◽  
Rossana Coda
Keyword(s):  
Lactic Acid ◽  
Lactic Acid Bacteria ◽  
Raw Materials ◽  
Degree Of Polymerization ◽  
Raw Material ◽  
Fermentation Time ◽  
Viscosity Increase ◽  
Spent Grain ◽  
Leuconostoc Pseudomesenteroides ◽  
Weissella Confusa

Abstract Background Lactic acid bacteria can synthesize dextran and oligosaccharides with different functionality, depending on the strain and fermentation conditions. As natural structure-forming agent, dextran has proven useful as food additive, improving the properties of several raw materials with poor technological quality, such as cereal by-products, fiber-and protein-rich matrices, enabling their use in food applications. In this study, we assessed dextran biosynthesis in situ during fermentation of brewers´ spent grain (BSG), the main by-product of beer brewing industry, with Leuconostoc pseudomesenteroides DSM20193 and Weissella confusa A16. The starters performance and the primary metabolites formed during 24 h of fermentation with and without 4% sucrose (w/w) were followed. Results The starters showed similar growth and acidification kinetics, but different sugar utilization, especially in presence of sucrose. Viscosity increase in fermented BSG containing sucrose occurred first after 10 h, and it kept increasing until 24 h concomitantly with dextran formation. Dextran content after 24 h was approximately 1% on the total weight of the BSG. Oligosaccharides with different degree of polymerization were formed together with dextran from 10 to 24 h. Three dextransucrase genes were identified in L. pseudomesenteroides DSM20193, one of which was significantly upregulated and remained active throughout the fermentation time. One dextransucrase gene was identified in W. confusa A16 also showing a typical induction profile, with highest upregulation at 10 h. Conclusions Selected lactic acid bacteria starters produced significant amount of dextran in brewers’ spent grain while forming oligosaccharides with different degree of polymerization. Putative dextransucrase genes identified in the starters showed a typical induction profile. Formation of dextran and oligosaccharides in BSG during lactic acid bacteria fermentation can be tailored to achieve specific technological properties of this raw material, contributing to its reintegration into the food chain.

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