Recent Advances in Structural Characterization of Natural Rubber

2009 ◽  
Vol 82 (3) ◽  
pp. 283-314 ◽  
Author(s):  
Yasuyuki Tanaka ◽  
Lucksanaporn Tarachiwin
Keyword(s):  
Structural Characterization ◽  
Micelle Formation ◽  
Solution Viscosity ◽  
Type I ◽  
Branch Points ◽  
Physical Treatment ◽  
Purification Method ◽  
Long Chain Branching ◽  
Recent Advances

Abstract Structural characterization of rubber from Hevea brasiliensis (NR) has been carried out to elucidate the biosynthesis mechanism of rubber molecule as well as to find the relationship between physical properties characteristic of NR and its structure. Recent advances of structural studies have provided a series of new information on the structure of long-chain branching based on the result of selective decomposition of branch-points by chemical and enzymatic treatments as well as physical treatment such as polar solvent treatments and washing of NR latex by centrifugation in the presence of a surfactant. The measurement of the resulting rubber with NMR, FTIR, SEC and dilute solution viscosity provided confirming evidence that the initiating terminal (ω-terminal) with an unidentified functional group and phosphate terminal (α-terminal) form branch-points by hydrogen bond, ionic bond or micelle formation of phospholipids linked to both terminal groups. Based on these results, the origin of green properties characteristic of NR has been explained and a new mechanism of storage hardening has been proposed. The purification method by saponification of NR latex developed for the structural characterization has been applied to produce purified NR latex free from Type I allergic reaction. Instantaneous coagulation of saponified latex by the use of a flocculant and formic acid has provided solid saponified NR having good green and cured rubber properties.

Structural Characterization of α-Terminal Group of Natural Rubber. 2. Decomposition of Branch-Points by Phospholipase and Chemical Treatments

2005 ◽  
Vol 6 (4) ◽  
pp. 1858-1863 ◽  
Author(s):  
Lucksanaporn Tarachiwin ◽  
Jitladda Sakdapipanich ◽  
Koichi Ute ◽  
Tatsuki Kitayama ◽  
Yasuyuki Tanaka
Keyword(s):  
Natural Rubber ◽  
Structural Characterization ◽  
Terminal Group ◽  
Branch Points ◽  
Chemical Treatments

Structural characterization of hexameric shell proteins from two types of choline-utilization bacterial microcompartments

2021 ◽  
Vol 77 (9) ◽  
Author(s):  
Jessica M. Ochoa ◽  
Oscar Mijares ◽  
Andrea A. Acosta ◽  
Xavier Escoto ◽  
Nancy Leon-Rivera ◽  
...  
Keyword(s):  
Structural Characterization ◽  
Building Blocks ◽  
Type I ◽  
Type Ii ◽  
Protein Subunits ◽  
Bacterial Microcompartments ◽  
Bacterial Microcompartment ◽  
Glycyl Radical ◽  
Shell Proteins

Bacterial microcompartments are large supramolecular structures comprising an outer proteinaceous shell that encapsulates various enzymes in order to optimize metabolic processes. The outer shells of bacterial microcompartments are made of several thousand protein subunits, generally forming hexameric building blocks based on the canonical bacterial microcompartment (BMC) domain. Among the diverse metabolic types of bacterial microcompartments, the structures of those that use glycyl radical enzymes to metabolize choline have not been adequately characterized. Here, six structures of hexameric shell proteins from type I and type II choline-utilization microcompartments are reported. Sequence and structure analysis reveals electrostatic surface properties that are shared between the four types of shell proteins described here.

Fractionation and structural characterization of six purified rhamnogalacturonans type I from flaxseed mucilage

2017 ◽  
Vol 62 ◽  
pp. 273-279 ◽  
Author(s):  
Redouan Elboutachfaiti ◽  
Cédric Delattre ◽  
Anthony Quéro ◽  
Romain Roulard ◽  
Julie Duchêne ◽  
...  
Keyword(s):  
Structural Characterization ◽  
Type I

Structural Characterization of Natural Polyisoprenes: Solve the Mystery of Natural Rubber Based on Structural Study

2001 ◽  
Vol 74 (3) ◽  
pp. 355-375 ◽  
Author(s):  
Yasuyuki Tanaka
Keyword(s):  
Fatty Acids ◽  
Natural Rubber ◽  
Structural Characterization ◽  
Unsaturated Fatty Acids ◽  
Saturated Fatty Acids ◽  
Terminal Group ◽  
Radical Scavenger ◽  
Branch Points

Abstract Structural characterization of naturally occurring polyisoprenes was carried out to solve the mystery of natural rubber (NR), such as the biosynthesis mechanism of rubber formation, the origin of outstanding properties of NR and the role of rubber in rubber trees. The NMR analysis, based on terpenes and polyprenols as models, disclosed the structure of both terminal groups of rubber chain. Structural evidence indicated that the biosynthesis of rubbers from Lactarius mushroom and leaves of high plants starts from trans, trans-farnesyl diphosphate or trans, trans, trans-geranylgeranyl diphosphate and terminates by dephosphorylation to form a hydroxyl terminal group. The biosynthesis of NR was presumed to start from unidentified initiating species containing two trans-isoprene units and peptide group and to terminate forming a phospholipid terminal group. The initiating group of NR associated with proteins formed branch points, which can be decomposed by enzymatic deproteinization. The branch points formed by phospholipid group were decomposed by transesterification with sodium methoxide. Rapid crystallization of NR was explained by the presence of mixed fatty acids synergistically with linked fatty acids, which were included in phospholipid. Saturated fatty acids linked to rubber chain induced crystallization, while mixed unsaturated fatty acids acted as plasticizer and accelerated the crystallization rate. This was confirmed by the preparation of model cis-polyisoprene grafted with stearic acid. The green strength of NR decreased to the same level as synthetic cis-polyisoprene after transesterification, indicating the effect of branching formed by the phospholipid terminal group and fatty acids in NR. The role of NR in Hevea trees was analyzed using NR from Hevea trees never tapped before. The formation of hard gel and oxidative degradation during the storage of NR in Hevea trees suggested that NR acted as a radical scavenger to remove hydroperoxide.

Functional and structural characterization of two Bacillus megaterium nitroreductases biotransforming the herbicide mesotrione

2016 ◽  
Vol 473 (10) ◽  
pp. 1443-1453 ◽  
Author(s):  
Louis Carles ◽  
Pascale Besse-Hoggan ◽  
Muriel Joly ◽  
Armelle Vigouroux ◽  
Solange Moréra ◽  
...  
Keyword(s):  
Bacillus Megaterium ◽  
Structural Characterization ◽  
Agricultural Soil ◽  
Nitro Compounds ◽  
Type I ◽  
Parent Molecule ◽  
Nitrobenzoic Acid ◽  
Ping Pong ◽  
Optimal Ph

Mesotrione is a selective herbicide belonging to the triketone family, commonly used on maize cultures since 2003. A mesotrione-transforming Bacillus megaterium Mes11 strain isolated from an agricultural soil was used as a model to identify the key enzymes initiating the biotransformation of this herbicide. Two enzymes (called NfrA1 and NfrA2/YcnD) were identified, and functionally and structurally characterized. Both belong to the NfsA FRP family of the nitro-FMN reductase superfamily (type I oxygen-insensitive nitroreductase) and show optimal pH and temperature of 6–6.5 and 23–25°C, respectively. Both undergo a Ping Pong Bi Bi mechanism, with NADPH and NADPH/NADH as cofactors for NfrA1 and NfrA2/YcnD, respectively. It is interesting that both can also reduce various nitro compounds including pesticides, antibiotics, one prodrug and 4-methylsulfonyl-2-nitrobenzoic acid, one of the mesotrione metabolites retrieved from the environment. The present study constitutes the first identification of mesotrione-transforming enzymes. These enzymes (or their corresponding genes) could be used as biomarkers to predict the capacity of ecosystems to transform mesotrione and assess their contamination by both the parent molecule and/or the metabolites.

Synthesis and Structural Characterization of Organically-Modified Microporous Silicates

1998 ◽  
Vol 519 ◽  
Author(s):  
F. Babonneau ◽  
L. Leite ◽  
S. Fonlupt ◽  
F. Ribot ◽  
L. Bergogne ◽  
...  
Keyword(s):  
Structural Characterization ◽  
Nitrogen Adsorption ◽  
Type I ◽  
Silicate Phase ◽  
Organically Modified Silicates ◽  
Bet Method ◽  
Organically Modified ◽  
Acidic Conditions ◽  
Hexagonally Ordered

AbstractOrganically-modified silicates have been synthesized from RSi(OEt)3 (R = CH3, C2H5, C8H17, CH2=CH, C6H5) and TEOS under acidic conditions, in the presence of cethyltrimethylammonium (CTAB). The introduction of RSiO1.5 units with R/Si =0.2, affects the ordering of the expected hexagonal silicate phase, except when R = C6H5. The sample containing phenyl functions was thus submitted to surfactant extraction; calcination at 350°C appears to be more efficient, and less disruptive for the network ordering than a washing procedure in ethanol. Nitrogen adsorption measurements on the hexagonally ordered calcined sample that still contains phenyl groups, yields a type I isotherm, typical of a microporous solid. BET method leads to a surface area of 1000 m2/g and a pore volume of 0.32 cm3/g.

scholarly journals The X-ray structure of human P-cadherin EC1-EC2 in a closed conformation provides insight into the type I cadherin dimerization pathway

2015 ◽  
Vol 71 (4) ◽  
pp. 371-380 ◽  
Author(s):  
Andrea Dalle Vedove ◽  
Anna Paola Lucarelli ◽  
Valentina Nardone ◽  
Angelica Matino ◽  
Emilio Parisini
Keyword(s):  
Structural Characterization ◽  
Adherens Junction ◽  
Large Family ◽  
Type I ◽  
Calcium Dependent ◽  
Closed Conformation ◽  
Naturally Occurring ◽  
Packing Arrangement

Cadherins are a large family of calcium-dependent proteins that mediate cellular adherens junction formation and tissue morphogenesis. To date, the most studied cadherins are those classified as classical, which are further divided into type I or type II depending on selected sequence features. Unlike other members of the classical cadherin family, a detailed structural characterization of P-cadherin has not yet been fully obtained. Here, the high-resolution crystal structure determination of the closed form of human P-cadherin EC1-EC2 is reported. The structure shows a novel, monomeric packing arrangement that provides a further snapshot in the yet-to-be-achieved complete description of the highly dynamic cadherin dimerization pathway. Moreover, this is the first multidomain cadherin fragment to be crystallized and structurally characterized in its closed conformation that does not carry any extra N-terminal residues before the naturally occurring aspartic acid at position 1. Finally, two clear alternate conformations are observed for the critical Trp2 residue, suggestive of a transient, metastable state. The P-cadherin structure and packing arrangement shown here provide new and valuable information towards the complete structural characterization of the still largely elusive cadherin dimerization pathway.

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