A Water‐Soluble Cu Complex as Molecular Catalyst for Electrocatalytic CO2 Reduction on Graphene‐Based Electrodes

A structurally simple molecular 1,10‐phenanthroline‐Cu complex on a mesostructured graphene matrix that can be active and selective toward CO₂ reduction over H₂ evolution in an aqueous solution is reported. The active sites consist of Cu(I) center in a distorted trigonal bipyramidal geometry, which enables the adsorption of CO₂ with η¹‐COO‐like configuration to commence the catalysis, with a turnover frequency of ≈45 s^?1 at ?1 V versus reversible hydrogen electrode. Using in situ infrared spectroelectrochemical investigation, it is demonstrated that the Cu complex can be reversibly heterogenized near the graphene surface via potential control. An increase of electron density in the complex is observed as a result of the interaction from the electric field, which further tunes the electron distribution in the neighboring CO₂. It is also found that the mesostructure of graphene matrix favored CO₂ reduction on the Cu center over hydrogen evolution by limiting mass transport from the bulk solution to the electrode surface.     

Multi‐spectroscopic and molecular dynamics simulations investigation of the binding mechanism of polybrominated diphenyl ethers to hen egg white lysozyme

Three PBDEs (BDE25, BDE47, and BDE154) were selected to investigate the interactions between PBDEs and hen egg white lysozyme (HEWL) by molecular modeling, fluorescence spectroscopy, and FT‐IR spectra. The docking results showed that hydrogen bonds were formed between BDE25 and residue TRP63 and between BDE47 and TRP63 with bond lengths of 2.178 Å and 2.146 Å, respectively. The molecular dynamics simulations indicated that van der Waals forces played a predominant role in the binding of three PBDEs to HEWL. The observed fluorescence quenching can be attributed to the formation of complexes between HEWL and PBDEs, and the quenching mechanism is a static quenching. According to Förster's non‐radiative energy transfer theory, the binding distances r were < 7 nm, indicating a high probability of energy transfer from HEWL to the three PBDEs. The synchronous fluorescence showed that the emission maximum wavelength of tryptophan (TRP) residues emerged a red‐shift. FT‐IR spectra indicated that BDE25, BDE47 and BDE154 induced the α‐helix percentage of HEWL decreased from 32.70% ± 1.64% to 28.27% ± 1.41%, 27.50% ± 1.38% and 29.78% ± 1.49%, respectively, whereas the percentage of random coil increased from 26.67% ± 1.33% to 27.60% ± 1.38%, 29.18% ± 1.46% and 30.59% ± 1.53%, respectively.     

基于杂交链式(HCR)反应的甲型流感病毒检测技术研究

甲型流感病毒的现场快速检测对于流感的及时有效防控具有重要意义．本研究基于杂交链式(HCR)反应,利用GO对荧光基团的猝灭作用及共同实现了对甲型流感病毒的快速检测．当目标序列存在时,可引发HCR反应,使短链DNA形成长链,保护FAM荧光基团不被猝灭,从而实现目标物的检测．实验结果表明,该方法在10～40 nmol/L范围内荧光强度与目标检测物浓度表现出了良好的线性关系,检测范围为5～100 nmol/L．这种HCR等温扩增检测技术具有较好的样本检测能力,具有等温、无酶、反应体系简单、操作步骤简便等优点,表现出良好的现场检测应用前景．     

食用调和油中花生油含量的近红外光谱分析

采用偏最小二乘法(PLS)等方法建立了食用调和油中花生油含量定量分析的近红外光谱定标模型。采集食用调和油样品在4 000 cm-1~10 000 cm-1范围内的近红外漫反射光谱,光谱经一阶导数处理后,采用偏最小二乘法建立样品中花生油含量的定标模型,并用Leave-one-out内部交叉验证法对模型进行验证。模型相关系数为0.99961,校正均方根RMSEC为0.830%。比较不同光谱预处理方法对定标模型的影响,结果表明一阶导数Corr.coeff最好。采用不同的化学计量学方法建立的定标模型中以偏最小二乘回归法最理想。     

Detection and identification of ‘Candidatus Phytoplasma asteris’ in Brassica rapa subsp. pekinensis in Poland

Severe growth abnormalities, including leaf yellowing, sprout proliferation and flower virescence and phyllody, were found on Brassica rapa subsp. pekinensis plants in Poland. The presence of phytoplasma in naturally infected plants was demonstrated by polymerase chain reaction assay employing phytoplasma universal P1/P7 followed by R16F2n/R16R2 primer pairs. The detected phytoplasma was identified using restriction fragment length polymorphism analysis (RFLP) of the 16S rRNA gene fragment with AluI, HhaI, MseI and RsaI endonucleases. After enzymatic digestion, all tested samples showed restriction pattern similar to that of ‘Candidatus phytoplasma asteris’. Nested PCR‐amplified products, obtained with primers R16F2n/R16R2, were sequenced. Sequences of the 16S rDNA gene fragment of analysed phytoplasma isolates were nearly identical. They revealed high nucleotide sequence identity (>98%) with corresponding sequences of other phytoplasma isolates from subgroup 16SrI‐B, and they were classified as members of ‘Candidatus phytoplasma asteris’. This is the first report of the natural occurrence of phytoplasma‐associated disease in plants of Chinese cabbage.     

Solution NMR Studies of Chlorella Virus DNA Ligase-adenylate

DNA ligases are essential guardians of genome integrity by virtue of their ability to recognize and seal 3′-OH/5′-phosphate nicks in duplex DNA. The substrate binding and three chemical steps of the ligation pathway are coupled to global and local changes in ligase structure, involving both massive protein domain movements and subtle remodeling of atomic contacts in the active site. Here we applied solution NMR spectroscopy to study the conformational dynamics of the Chlorella virus DNA ligase (ChVLig), a minimized eukaryal ATP-dependent ligase consisting of nucleotidyltransferase, OB, and latch domains. Our analysis of backbone ¹⁵N spin relaxation and ¹⁵N,¹H residual dipolar couplings of the covalent ChVLig-AMP intermediate revealed conformational sampling on fast (picosecond to nanosecond) and slow timescales (microsecond to millisecond), indicative of interdomain and intradomain flexibility. We identified local and global changes in ChVLig-AMP structure and dynamics induced by phosphate. In particular, the chemical shift perturbations elicited by phosphate were clustered in the peptide motifs that comprise the active site. We hypothesize that phosphate anion mimics some of the conformational transitions that occur when ligase-adenylate interacts with the nick 5′-phosphate.     

First Report of Northern Root-Knot Nematode,Meloidogyne hapla,Parasitic on Oaks,Quercus brantii and Q. infectoria in Iran

Root-knot nematodes (RKN) are the most serious plant parasitic nematodes having a broad host range exceeding 2,000 plant species. Quercus brantii Lindl. and Q. infectoria Oliv are the most important woody species of Zagros forests in west of Iran where favors sub-Mediterranean climate. National Botanical Garden of Iran (NBGI) is scheduled to be the basic center for research and education of botany in Iran. This garden, located in west of Tehran, was established in 1968 with an area of about 150 ha at altitude of 1,320 m. The Zagros collection has about 3-ha area and it has been designed for showing a small pattern of natural Zagros forests in west of Iran. Brant’s oak (Q. brantii) and oak manna tree (Q. infectoria) are the main woody species in Zagros collection, which have been planted in 1989. A nematological survey on Zagros forest collection in NBGI revealed heavily infection of 24-yr-old Q. brantii and Q. infectoria to RKN, Meloidogyne hapla. The roots contained prominent galls along with egg sac on the surface of each gall. The galls were relatively small and in some parts of root several galls were conjugated, and all galls contained large transparent egg masses. The identification of M. hapla was confirmed by morphological and morphometric characters and amplification of D2-D3 expansion segments of 28S rRNA gene. The obtained sequences of large-subunit rRNA gene from M. hapla was submitted to the GenBank database under the accession number {"type":"entrez-nucleotide","attrs":{"text":"KP319025","term_id":"852381377","term_text":"KP319025"}}KP319025. The sequence was compared with those of M. hapla deposited in GenBank using the BLAST homology search program and showed 99% similarity with those {"type":"entrez-nucleotide","attrs":{"text":"KJ755183","term_id":"667714404","term_text":"KJ755183"}}KJ755183, {"type":"entrez-nucleotide","attrs":{"text":"GQ130139","term_id":"239819330","term_text":"GQ130139"}}GQ130139, {"type":"entrez-nucleotide","attrs":{"text":"DQ328685","term_id":"84794916","term_text":"DQ328685"}}DQ328685, and {"type":"entrez-nucleotide","attrs":{"text":"KJ645428","term_id":"657709843","term_text":"KJ645428"}}KJ645428. The second stage juveniles of M. hapla isolated from Brant’s oak (Q. Brantii) showed the following morphometric characters: (n = 12), L = 394 ± 39.3 (348 to 450) µm; a = 30.9 ± 4 (24.4 to 37.6); b = 4.6 ± 0.44 (4 to 5.1); b΄ = 3.3 ± 0.3 (2.7 to 3.7), c = 8.0 ± 1 (6.2 to 10.3), ć = 5.3 ± 0.8 (3.5 to 6.3); Stylet = 12.1 ± 0.8 (11 to 13) µm; Tail = 50 ± 5.6 (42 to 57) µm; Hyaline 15 ± 1.8 (12 to 18) µm. Oak manna, Q. infectoria population of second stage juveniles clearly possessed short body length and consequently other morphometric features were less than those determined for Q. brantii population, and these features were: (n = 12), L = 359.0 ± 17.3 (319 to 372) µm; a = 28.6 ± 3 (22.8 to 31); b = 5.0 ± 0.3 (4.8 to 5.2); b΄ = 3.3 ± 0.2 (3 to 3.6), c = 8.1 ± 0.5 (7.4 to 8.8), ć = 4.7 ± 0.5 (3.9 to 5.2); Stylet = 11.4 ± 0.7 (10 to 12) µm; Tail = 44 ± 1.8 (42 to 47) µm; Hyaline 12 ± 1.7 (10 to 15) µm. To date two species of Meloidogyne, M. querciana Golden, 1979 and M. christiei Golden and Kaplan, 1986 have been reported to parasitize oaks (Quercus spp.) from the United States of America. M. querciana was found on pin oak Quercus palustris in Virginia. The oak RKN infected pine oak, red oak, and American chestnut heavily in greenhouse tests (Golden, 1979). The other species M. christiei was described from turkey oak and Q. laevis in Florida, which has monospecific host range (Golden and Kaplan, 1986). Both of these RKN species seem to be restricted to the United States of America and have not been reported from other place. According to our knowledge this is the first report of occurrence of M. hapla on Q. brantii and Q. infectoria in the world. This study includes these two oak species to the host range of RKN, M. hapla for the world and expands the information of RKN, M. hapla host ranges on oaks.     

Conformational Dynamics and Structural Plasticity Play Critical Roles in the Ubiquitin Recognition of a UIM Domain

Ubiquitin-interacting motifs (UIMs) are an important class of protein domains that interact with ubiquitin or ubiquitin-like proteins. These approximately 20-residue-long domains are found in a variety of ubiquitin receptor proteins and serve as recognition modules towards intracellular targets, which may be individual ubiquitin subunits or polyubiquitin chains attached to a variety of proteins. Previous structural studies of interactions between UIMs and ubiquitin have shown that UIMs adopt an extended structure of a single α-helix, containing a hydrophobic surface with a conserved sequence pattern that interacts with key hydrophobic residues on ubiquitin. In light of this large body of structural studies, details regarding the presence and the roles of structural dynamics and plasticity are surprisingly lacking. In order to better understand the structural basis of ubiquitin-UIM recognition, we have characterized changes in the structure and dynamics of ubiquitin upon binding of a UIM domain from the yeast Vps27 protein. The solution structure of a ubiquitin-UIM fusion protein designed to study these interactions is reported here and found to consist of a well-defined ubiquitin core and a bipartite UIM helix. Moreover, we have studied the plasticity of the docking interface, as well as global changes in ubiquitin due to UIM binding at the picoseconds-to-nanoseconds and microseconds-to-milliseconds protein motions by nuclear magnetic resonance relaxation. Changes in generalized-order parameters of amide groups show a distinct trend towards increased structural rigidity at the UIM-ubiquitin interface relative to values determined in unbound ubiquitin. Analysis of ¹⁵N Carr-Purcell-Meiboom-Gill relaxation dispersion measurements suggests the presence of two types of motions: one directly related to the UIM-binding interface and the other induced to distal parts of the protein. This study demonstrates a case where localized interactions among protein domains have global effects on protein motions at timescales ranging from picoseconds to milliseconds.