285 research outputs found
Genetic Diversity of Dahongjun, the Commercially Important âBig Red Mushroomâ from Southern China
BACKGROUND: In southern China, a wild ectomycorrhizal mushroom commonly called "Dahongjun" or "Big Red Mushroom" by the local residents, has been harvested, consumed, and/or exported as an exotic food for many years. Although ecologically and economically important, very little is known about this mushroom, including its diversity and population structure. METHODOLOGY AND PRINCIPAL FINDINGS: In this study, we analyzed 122 samples from five local populations representing the known distribution ranges of this mushroom in southern China. We investigated the genetic diversity and geographic structure of this mushroom using sequences from four DNA fragments. Our analyses identified that this mushroom contained at least three divergent lineages: one corresponds to a recently described species Russula griseocarnosa from southern China and the remaining two likely represent two novel species. While these lineages were prominently structured geographically based on ITS sequences, evidence for ancient and/or recent gene flow was also identified within individual lineages. In addition, a local population from Ailaoshan in central Yunnan Province where 85 of our 122 specimens came from showed clear evidence of recombination. CONCLUSION AND SIGNIFICANCE: The ectomycorrhizal mushroom "Dahongjun" from southern China is a species complex with at least three divergent lineages. These lineages are largely geographically structured and there is evidence for recombination in nature. Our results indicate mature Dahongjun mushrooms with abundant basidiospores are important for the reproduction of this mushroom in nature and that individual populations of this species should be managed separately
Substituent Effects in the Noncovalent Bonding of SO2 to Molecules containing a Carbonyl Group. The Dominating Role of the Chalcogen Bond
The SO2 molecule is paired with a number of carbonyl-containing molecules, and the properties of the resulting complexes are calculated by high-level ab initio theory. The global minimum of each pair is held together primarily by a S···O chalcogen bond wherein the lone pairs of the carbonyl O transfer charge to the Ï* antibonding SO orbital, supplemented by smaller contributions from weak CH···O H-bonds. The binding energies vary between 4.2 and 8.6 kcal/mol, competitive with even some of the stronger noncovalent forces such as H-bonds and halogen bonds. The geometrical arrangement places the carbonyl O atom above the plane of the SO2 molecule, consistent with the disposition of the molecular electrostatic potentials of the two monomers. This S···O bond differs from the more commonly observed chalcogen bond in both geometry and origin. Substituents exert their influence via inductive effects that change the availability of the carbonyl O lone pairs as well as the intensity of the negative electrostatic potential surrounding this atom
The addition of halogens and interhalogens on palladacyclopentadienyl complexes bearing quinolyl-thioether as spectator ligands. A kinetic and computational study
We have studied the oxidative addition of halogens (I2 and Br2) and interhalogens (ICl and IBr) on complexes of the type [Pd(thioquinoline)C4(COOMe)4], (thioquinoline = 8-(methylthio)quinoline, 8-(t-butylthioquinoline, 2-methyl-8 (methylthio)quinoline, 2-methyl-8-(t-butylthio)quinoline). The expected palladium(thioquinoline)-r-butadienyl derivatives have been obtained by the stoichiometric addition of I2 and Br2 to a solution of the starting palladacyclopentadienyl complexes. The bromine in excess induces the extrusion of the di-bromo-(E, E)-r-butadiene and the formation of the thioquinoline palladium(II) di-bromide species. The kinetics and mechanism of these reactions have been determined. Except for one case which was analyzed in detail by a computational study, the oxidative addition of the interhalogens ICl and IBr yields the species that is less predictable from the thermodynamic point of view. In general the computational approach justifies the reaction progress and allows an interpretative clue suggesting a kinetically governed path to the reaction products. Finally, the solid state structures of two reaction products were resolved and reporte
Addition of halogens and interhalogens on palladacyclopentadienyl complexes stabilized by pyridyl-thioether N-S spectator ligands
We have studied from the experimental and theoretical point of view the oxidative addition of halogens (I-2 and Br-2) and interhalogens (ICl and IBr) on palladiumcyclopentadienyl complexes bearing heteroditopic pyridyl-thioether spectator ligands.Addition of I-2 or of a stoichiometric amount of Br-2 to a CDCl3 solution of the starting palladacyclo-pentadienyl complexes yields the expected palladium-sigma-butadienyl derivatives. The bromide derivative in the presence of a further excess of Br-2 gives the wanted dibromo-(E, E)-sigma-butadienyl and the pyridylthioether palladium(II) dibromide species. The rates of these reactions have been determined.When the interhalogens are used as oxidizing agents the thermodynamically hampered species is formed at first. Only in the case of the reaction of IBr is the formation of the energetically hampered derivative followed by partial isomerization to the most stable complex. The rate of isomerization and the related equilibrium constant between isomers have been measured. On the basis of the experimental evidence and the computational approach we have proposed a plausible energetic path yielding the first formed unexpected species.Finally, the solid state structures of two reaction products were resolved and reported. (C) 2016 Elsevier B.V. All rights reserved
The shape of the halogen atomâanisotropy of electron distribution and its dependence on basis set and method used
Full-wave acoustic and thermal modeling of transcranial ultrasound propagation and investigation of skull-induced aberration correction techniques: a feasibility study
The production of endoglucanase and -xylanase by immobilized cells of Streptomyces
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Do transcipt levels of CRLR and RAMPs account for CGRP and AM binding in cultured cells?
Initiation of Eukaryotic Protein Synthesis: Native 40S Subunits Bind Initiator Transfer Ribonucleic Acid before Associating with Messenger Ribonucleic Acid
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