Characterization of Hevea Brasiliensis Rubber from Virgin Trees: A Possible Role of Cis-Polyisoprene in Unexploited Tree

1999 ◽  
Vol 72 (2) ◽  
pp. 299-307 ◽  
Author(s):  
Jitladda Sakdapipanich ◽  
Yasuyuki Tanaka ◽  
Jean Louis Jacob ◽  
Jean d'Auzac
Keyword(s):  
Free Radicals ◽  
Hevea Brasiliensis ◽  
Mature Tree ◽  
Naturally Occurring ◽  
Aging Properties ◽  
High Ammonia ◽  
Regulation Mechanisms ◽  
Latex Biosynthesis

Abstract The role of rubber in Hevea brasiliensis was analyzed based on the structural analysis of rubber in rubber trees as latex. The rubber obtained from a mature-tree which has never tapped before, so-called “virgin mature-tree” (Vir-NR), contained the gel fraction higher than 80%, while that from a regularly tapped mature-tree (Reg-NR) was less than 3%. The gel showed almost the same structure as a crosslinked rubber prepared from fresh latex in the presence of peroxide, with the molecular weight between crosslinks (Mc) of 3×103. This value is extremely low comparing with that of 7×105 observed for the soft-gel in rubber from high-ammonia latex and Pale crepe. The sol fraction from Vir-NR was an oxidative degraded product containing aldehyde and epoxide groups. Aging properties of Vir-NR are much worse than those of Reg-NR. This indicates that rubber accepts free-radicals to form C-C crosslinking and partly oxidative scission of main-chains during storage in laticiferous tubes of Hevea trees. This suggests that a possible role of rubber is a scavenger of free-radicals in latex, due to lack of the naturally occurring antioxidants. The consecutive tappings of latex from the first opening mature-tree resulted in the formation of rubber similar to that obtained from Reg-NR, after six days. This modification indicates that the new regulation mechanisms in latex biosynthesis, which is induced by exploitation, can avoid the rubber chain crosslinkings and increase their elongations.

scholarly journals Thrombin A-Chain: Activation Remnant or Allosteric Effector?

Thrombosis ◽  
2010 ◽  
Vol 2010 ◽  
pp. 1-9 ◽  
Author(s):  
Isis S. R. Carter ◽  
Amanda L. Vanden Hoek ◽  
Edward L. G. Pryzdial ◽  
Ross T. A. MacGillivray
Keyword(s):  
Biochemical Characterization ◽  
Catalytic Domain ◽  
Current Data ◽  
Enzymatic Reactions ◽  
Allosteric Effector ◽  
Naturally Occurring ◽  
Physiologic Function ◽  
A Chain

Although prothrombin is one of the most widely studied enzymes in biology, the role of the thrombin A-chain has been neglected in comparison to the other domains. This paper summarizes the current data on the prothrombin catalytic domain A-chain region and the subsequent thrombin A-chain. Attention is given to biochemical characterization of naturally occurring prothrombin A-chain mutations and alanine scanning mutants in this region. While originally considered to be simply an activation remnant with little physiologic function, the thrombin A-chain is now thought to play a role as an allosteric effector in enzymatic reactions and may also be a structural scaffold to stabilize the protease domain.

scholarly journals Characterization of a Large Pericentric Inversion in Plateau Fence Lizards (Sceloporus tristichus): Evidence from Chromosome-scale Genomes

2020 ◽  
Author(s):  
Ana M. Bedoya ◽  
Adam D. Leaché
Keyword(s):  
Hybrid Zone ◽  
Pericentric Inversion ◽  
Chromosomal Evolution ◽  
Squamate Reptiles ◽  
Naturally Occurring ◽  
Karyotype Formula ◽  
Dynamic Hybrid ◽  
Genome Assemblies

AbstractSpiny lizards in the genus Sceloporus are a model system among squamate reptiles for studies of chromosomal evolution. While most pleurodont iguanians retain an ancestral karyotype formula of 2n=36 chromosomes, Sceloporus exhibits substantial karyotype variation ranging from 2n=22 to 2n=46 chromosomes. In this study, we present two annotated chromosome-scale genome assemblies for the Plateau Fence Lizard (Sceloporus tristichus) in order to facilitate research on the role of pericentric inversion polymorphisms on adaptation and speciation. Based on previous karyotype work using conventional staining, the S. tristichus genome is characterized as 2n=22 with 6 pairs of macrochromosomes and 5 pairs of microchromosomes with a large pericentric inversion polymorphism on chromosome seven that is geographically variable. We provide annotated, chromosome-scale genomes for two lizards located at opposite ends of a dynamic hybrid zone that are each fixed for different inversion polymorphisms. The assembled genomes are 1.84 to 1.87 Gb (1.72 Gb for scaffolds mapping to chromosomes) with a scaffold N50 of 267.5 Mb. Functional annotation of the genomes resulted in 65,417 annotated genes, 16,426 of which were deduced to have a function. We confirmed the presence of a 4.62 Mb pericentric inversion on chromosome seven, which contains 59 annotated coding genes with known functions. These new genomic resources provide opportunities to perform genomic scans and investigate the formation and spread of pericentric inversions in a naturally occurring hybrid zone.

scholarly journals ROLE OF PHYTOCHEMICALS IN ORAL POTENTIALLY MALIGNANT DISORDERS : A REVIEW

2014 ◽  
Vol 04 (04) ◽  
pp. 120-125
Author(s):  
Ananya Madiyal ◽  
Vidya Ajila ◽  
Subhas G Babu ◽  
Shruthi Hedge ◽  
Harini Keshavaiah ◽  
...  
Keyword(s):  
Free Radicals ◽  
Chemical Species ◽  
Healthcare Services ◽  
Health Concern ◽  
Oral Lesions ◽  
Oral Potentially Malignant Disorders ◽  
Naturally Occurring ◽  
Potentially Malignant Disorders ◽  
Potentially Malignant

AbstractOral cancer is a major global health concern and poses a challenge to diagnostic and therapeutic aspects of healthcare services. Various oral lesions like leukoplakia, erythroplakia, lichen planus and oral submucus fibrosis categorized as orally potential malignant disorders have shown increased incidence of malignant transformation. Free radicals are highly reactive chemical species with capacity to damage nucleic acids, proteins and lipids and bring about changes of clinical significance. Antioxidants help in scavenging these free radicals and prevent disease progression. Naturally occurring phytochemicals play an important role in preventing oxidative stress and protect the cells from damage by free radicals.

Role of lncRNAs in prostate cancer development and progression

2014 ◽  
Vol 395 (11) ◽  
pp. 1275-1290 ◽  
Author(s):  
Melanie Weiss ◽  
Christoph Plass ◽  
Clarissa Gerhauser
Keyword(s):  
Prostate Cancer ◽  
Target Genes ◽  
Current Knowledge ◽  
Prostate Carcinogenesis ◽  
Prostate Cancer Development ◽  
Chromatin Remodeling Complexes ◽  
Regulation Mechanisms ◽  
Functional Analyses

Abstract Prostate cancer (PCa) is the second most common cause of cancer-related deaths in men. Despite advances in the characterization of genomic and epigenetic aberrations contributing to PCa, the etiology of PCa is still far from being understood. Research over the past decade demonstrated the role of long non-coding RNAs (lncRNAs) in deregulation of target genes mainly through epigenetic mechanisms. In PCa, evidence accumulated that hundreds of lncRNAs are dysregulated. Functional analyses revealed their contribution to prostate carcinogenesis by targeting relevant pathways and gene regulation mechanisms including PTEN/AKT and androgen receptor signaling as well as chromatin remodeling complexes. Here we summarize our current knowledge on the roles of lncRNAs in PCa and their potential use as biomarkers for aggressive PCa and as novel therapeutic targets.

scholarly journals The Role of Ribosomal Protein S6 Kinases in Plant Homeostasis

2021 ◽  
Vol 8 ◽  
Author(s):  
Irabonosi Obomighie ◽  
Kestutis Lapenas ◽  
Billy E. Murphy ◽  
Alexander M. C. Bowles ◽  
Ulrike Bechtold ◽  
...  
Keyword(s):  
Sequence Similarity ◽  
Tor Pathway ◽  
The Past ◽  
Ribosomal Protein S6 ◽  
Downstream Effectors ◽  
Regulation Mechanisms ◽  
Ribosomal S6 Kinase ◽  
High Level

The p70 ribosomal S6 kinase (S6K) family is a group of highly conserved kinases in eukaryotes that regulates cell growth, cell proliferation, and stress response via modulating protein synthesis and ribosomal biogenesis. S6Ks are downstream effectors of the Target of Rapamycin (TOR) pathway, which connects nutrient and energy signaling to growth and homeostasis, under normal and stress conditions. The plant S6K family includes two isoforms, S6K1 and S6K2, which, despite their high level of sequence similarity, have distinct functions and regulation mechanisms. Significant advances on the characterization of human S6Ks have occurred in the past few years, while studies on plant S6Ks are scarce. In this article, we review expression and activation of the two S6K isoforms in plants and we discuss their roles in mediating responses to stresses and developmental cues.

scholarly journals Novel Naturally Occurring Bean pod mottle virus Reassortants with Mixed Heterologous RNA1 Genomes

2007 ◽  
Vol 97 (1) ◽  
pp. 79-86 ◽  
Author(s):  
Hongcang Gu ◽  
Chunquan Zhang ◽  
Said A. Ghabrial
Keyword(s):  
Symptom Severity ◽  
Potential Role ◽  
The United States ◽  
Mottle Virus ◽  
Bean Pod Mottle Virus ◽  
Naturally Occurring ◽  
Bipartite Genome ◽  
Distinct Strain

The comovirus Bean pod mottle virus (BPMV) is widespread in the soybean-growing regions in the United States. It has a bipartite genome consisting of RNA1 and RNA2, which are encapsidated separately. We previously have reported the occurrence in nature of two distinct subgroups of BPMV strains (subgroups I and II), as well as reassortants between the two subgroups. Here, we report the isolation and molecular characterization of naturally occurring partial diploid reassortant strains, which are diploid for RNA1 and haploid for RNA2. Whereas the RNA1s of the partial diploids are derived from two distinct strain subgroups (I and II), the RNA2 is derived from either subgroup I or II. The partial diploid strains induced strikingly severe symptoms on soybean, which could be explained based on the presence of two distinct RNA1s in the same plant. This conclusion was supported by the finding that pseudo-recombinants constructed with two diverse RNA1s induced very severe symptoms on soybean that mimicked those produced by the naturally occurring partial diploids. No enhancement of symptom severity was observed with pseudorecombinants constructed with closely related RNA1s. Likewise, no enhancement of symptom severity was noted with pseudo-recombinants that are diploid for RNA2 and haploid for RNA1. The potential role of genetic reassortment in the epidemiology and pathogenesis of BPMV is discussed.

Genome-wide identification of lncRNAs, miRNAs, mRNAs, and their regulatory networks involved in tapping panel dryness in rubber tree (Hevea brasiliensis)

2021 ◽  
Author(s):  
Hui Liu ◽  
Yiyu Hu ◽  
Kun Yuan ◽  
Chengtian Feng ◽  
Qiguang He ◽  
...  
Keyword(s):  
Hevea Brasiliensis ◽  
Regulatory Networks ◽  
Functional Characterization ◽  
Rubber Tree ◽  
Healthy Tree ◽  
Rubber Biosynthesis ◽  
Genome Wide ◽  
Tapping Panel Dryness

Abstract Noncoding RNAs (ncRNAs) play pivotal roles in various biological processes in plants. However, the role of ncRNAs in tapping panel dryness (TPD) of rubber tree (Hevea brasiliensis) is largely unknown. Here, the whole transcriptomes of bark tissues from healthy and TPD trees were performed to identify differentially expressed long ncRNAs (DELs), microRNAs/miRNA (DEMs), genes (DEGs), and their regulatory networks involved in TPD. A total of 263 DELs, 174 DEMs, and 1,574 DEGs were identified in the bark of TPD tree compared with that of healthy tree. KEGG analysis revealed that most of the DEGs and targets of DELs and DEMs were mainly enriched in metabolic pathways, biosynthesis of secondary metabolites, and plant hormone signal transduction. Additionally, the majority of DEGs and DELs related to rubber biosynthesis were down-regulated in TPD trees. Furthermore, 98 DEGs and 44 DELs were targeted by 54 DEMs, 190 DEGs were identified as putative targets of 56 DELs, and two and 44 DELs were predicted as precursors and endogenous target mimics (eTMs) of two and six DEMs, respectively. Based on these, the DEL-DEM-DEG regulatory network involved in TPD was constructed, and 13 hub DELs, three hub DEMs and two hub DEGs were identified. The results provide novel insights into the regulatory roles of ncRNAs underlying TPD and lay a foundation for future functional characterization of lncRNAs, miRNAs, and genes involved in TPD in rubber tree.

High Resolution Replication of Organoclay Surfaces

1982 ◽  
Vol 40 ◽  
pp. 576-577
Author(s):  
W. W. Barker ◽  
W. E. Rigsby ◽  
V. J. Hurst ◽  
W. J. Humphreys
Keyword(s):  
Clay Mineral ◽  
Organic Molecule ◽  
Organic Molecules ◽  
X Ray Diffraction ◽  
Xrd Pattern ◽  
X Ray ◽  
Naturally Occurring ◽  
Silicate Layers ◽  
Mineral Identification

Experimental clay mineral-organic molecule complexes long have been known and some of them have been extensively studied by X-ray diffraction methods. The organic molecules are adsorbed onto the surfaces of the clay minerals, or intercalated between the silicate layers. Natural organo-clays also are widely recognized but generally have not been well characterized. Widely used techniques for clay mineral identification involve treatment of the sample with H2 O2 or other oxidant to destroy any associated organics. This generally simplifies and intensifies the XRD pattern of the clay residue, but helps little with the characterization of the original organoclay. Adequate techniques for the direct observation of synthetic and naturally occurring organoclays are yet to be developed.

Digital x-ray mapping of nanometer-size supported bimetallic catalysts

1988 ◽  
Vol 46 ◽  
pp. 530-531
Author(s):  
L. T. Germinario
Keyword(s):  
Background Radiation ◽  
Metal Cluster ◽  
Single Element ◽  
Beam Diameter ◽  
X Rays ◽  
X Ray ◽  
Major Interest ◽  
Induced Changes

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.

Fine structure and properties of defects in naturally occurring silicates and oxides

1990 ◽  
Vol 48 (4) ◽  
pp. 460-461
Author(s):  
David R. Veblen
Keyword(s):  
Chemical Reactions ◽  
High Resolution Electron Microscopy ◽  
Extended Defects ◽  
Single Chain ◽  
Naturally Occurring ◽  
Resolution Electron ◽  
Fine Structures ◽  
Image Simulations ◽  
Similar Crystal Structure

Extended defects and interfaces control many processes in rock-forming minerals, from chemical reactions to rock deformation. In many cases, it is not the average structure of a defect or interface that is most important, but rather the structure of defect terminations or offsets in an interface. One of the major thrusts of high-resolution electron microscopy in the earth sciences has been to identify the role of defect fine structures in reactions and to determine the structures of such features. This paper will review studies using HREM and image simulations to determine the structures of defects in silicate and oxide minerals and present several examples of the role of defects in mineral chemical reactions. In some cases, the geological occurrence can be used to constrain the diffusional properties of defects.The simplest reactions in minerals involve exsolution (precipitation) of one mineral from another with a similar crystal structure, and pyroxenes (single-chain silicates) provide a good example. Although conventional TEM studies have led to a basic understanding of this sort of phase separation in pyroxenes via spinodal decomposition or nucleation and growth, HREM has provided a much more detailed appreciation of the processes involved.

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