Biological effects of low-energy C ion implantation on sesame (Sesamum indicum L.)

Field cultivation experiments on white sesame (Sesamum indicum L.)seeds implanted with low-energy C ion showed that different dosages of C ion implantation produce different biological effects.Sesame plants in 6 different dosage groups with C ion density respectively at 1×1011,1×1012,1×1015,5×1015,1×1016,5×1016 ion/cm2 were superior to the control group in plant height,leaf number,stalk diameter and leaf size.Further,sesame plants in these groups flower and seed earlier than those in the control group,and single plant yield also increased.Of all the groups,the 5×1015 ion/cm2 dosage group yielded the best effect,whereas the 1×1017/cm2 dosage group showed an evident inhibitory effect of ion implantation on the germination and growth of the sesame seeds.     

Breeding and application of Jiafuzhan, a new elite early indica rice cultivar in China

After 20 years of dedicated research,Jiafuzhan has been successfully developed under the new technologies in breeding high-quality early indica rice cultivars.Its rice quality has almost reached the A-level Editable Rice of Agriculture Department of China,and its average production reaches 400-500 kg/(666.7 m2).This new cultivar also has other characteristics such as enhanced resistance of blast and fallen,steady productivity,and strong adaptability.Jiafuzhan has been put into production of over 11.4×104 hm2 in Fujian Province and has been introduced and extended in other Provinces like Jiangxi,Guangdong,and Guangxi,China.The successes of breeding Jiafuzhan is a solution to the existing perennial problems in the rice industry,such as poor grain quality of big-grain rice and early indica rice,low productivity,and poor blast resistance of elite rice.     

Aplysia temptin - the 'glue' in the water-borne attractin pheromone complex

Temptin, a component of the complex of water-borne protein pheromones that stimulate attraction and mating behavior in the marine mollusk Aplysia, has sequence homology to the epidermal growth factor (EGF)-like domains of higher organisms that mediate protein-cell surface contact during fertilization and blood coagulation. In this work, recombinant temptin for structural and functional studies was produced in Escherichia coli using a cold shock promoter and purified by RP-HPLC. CD spectra confirmed a predominantly beta-sheet structure. Two disulfide bonds were determined via limited proteolysis and MS. One internal disulfide (Cys57-Cys77) was predicted from initial alignments with class I EGF-like domains; the second, between Cys18 and Cys103, could protect temptin against proteolysis in seawater and stabilize its interacting surface. A three-dimensional model of temptin was prepared with our MPACK suite, based on the Ca(2+)-binding, EGF-like domain of the extracellular matrix protein fibrillin. Two temptin residues, Trp52 and Trp79, which align with cysteine residues conserved in fibrillins, lie adjacent to and could stabilize the disulfide bonds and a proposed metal-binding loop. The water-borne pheromone attractin in egg cordon eluates is complexed with other proteins. Docking results with our model and the NMR structure of attractin suggest that one face of temptin interacts with the pheromone, perhaps controlling its access to the cellular receptors. Gel shifts confirmed that temptin complexes with wild-type attractin. These results indicate that temptin, analogous to the role of fibrillin in controlling transforming growth factor-beta concentration, modulates pheromone signaling by direct binding to attractin.     

One-step isolation of adenosine triphosphate from crude fermentation broth of Saccharomyces cerevisiae by anion-exchange chromatography using supermacroporous cryogel

Adenosine triphosphate (ATP) is an important high-energy compound widely used in biological and therapeutic fields. It can be produced by phosphorylation of adenosine monophosphate (AMP) with microbial cells in industrial scale and the effective isolation of ATP from microbial fermentation broth is a challenging work. In this work, we develop a novel one-step method to directly separate ATP from fermentation broth of Saccharomyces cerevisiae by anion-exchange chromatography using supermacroporous cryogel. The cryogel bed with tertiary amine groups was prepared by grafting N,N-dimethylaminoethyl methacrylate (DMAEMA) monomer chains onto the matrix of a polyacrylamide-based cryogel in a glass column and its properties of liquid dispersion, water permeability, porosity as well as the ligand density were measured. Chromatographic separation of ATP from the fermentation broth by the cryogel was carried out using deionised water and 0.01 M HCl as running buffer, respectively. The breakthrough characteristics and elution performance in the cryogel bed were revealed and analyzed. The purities of the obtained ATP were analyzed quantitatively by high performance liquid chromatography (HPLC). The maximal purity of ATP by the one-step separation method was 95.5% using 0.01 M HCl as running buffer in this work. The corresponding chromatographic behaviors were investigated and analyzed.     

Modification of Axial Fiber Contact Residues Impact Sickle Hemoglobin Polymerization by Perturbing a Network of Coupled Interactions

The identity of intermolecular contact residues in sickle hemoglobin (HbS) fiber is largely known. However, our knowledge about combinatorial effects of two or more contact sites or the mechanistic basis of such effects is rather limited. Lys16, His20, and Glu23 of the α-chain occur in intra-double strand axial contacts in the sickle hemoglobin (HbS) fiber. Here we have constructed two novel double mutants, HbS (K16Q/E23Q) and (H20Q/E23Q), with a view to delineate cumulative impact of interactions emanating from the above contact sites. Far-UV and visible region CD spectra of the double mutants were similar to the native HbS indicating the presence of native-like secondary and tertiary structure in the mutants. The quaternary structures in both the mutants were also preserved as judged by the derivative UV spectra of liganded (oxy) and unliganded (deoxy) forms of the double mutants. However, the double mutants displayed interesting polymerization behavior. The polymerization behaviour of the double mutants was found to be non-additive of the individual single mutants. While HbS (H20Q/E23Q) showed inhibitory effect similar to that of HbS (E23Q), the intrinsic inhibitory propensity of the associated single mutants was totally quelled in HbS (K16Q/E23Q) double mutant. Molecular dynamics (MD) simulations studies of the isolated α-chains as well as a module of the fiber containing the double and associated single mutants suggested that these contact sites at the axial interface of the fiber impact HbS polymerization through a coupled interaction network. The overall results demonstrate a subtle role of dynamics and electrostatics in the polymer formation and provide insights about interaction-linkage in HbS fiber assembly.     

The Legionella pneumophila IcmSW complex interacts with multiple Dot/Icm effectors to facilitate type IV translocation

Many gram-negative pathogens use a type IV secretion system (T4SS) to deliver effector proteins into eukaryotic host cells. The fidelity of protein translocation depends on the efficient recognition of effector proteins by the T4SS. Legionella pneumophila delivers a large number of effector proteins into eukaryotic cells using the Dot/Icm T4SS. How the Dot/Icm system is able to recognize and control the delivery of effectors is poorly understood. Recent studies suggest that the IcmS and IcmW proteins interact to form a stable complex that facilitates translocation of effector proteins by the Dot/Icm system by an unknown mechanism. Here we demonstrate that the IcmSW complex is necessary for the productive translocation of multiple Dot/Icm effector proteins. Effector proteins that were able to bind IcmSW in vitro required icmS and icmW for efficient translocation into eukaryotic cells during L. pneumophila infection. We identified regions in the effector protein SidG involved in icmSW-dependent translocation. Although the full-length SidG protein was translocated by an icmSW-dependent mechanism, deletion of amino terminal regions in the SidG protein resulted in icmSW-independent translocation, indicating that the IcmSW complex is not contributing directly to recognition of effector proteins by the Dot/Icm system. Biochemical and genetic studies showed that the IcmSW complex interacts with a central region of the SidG protein. The IcmSW interaction resulted in a conformational change in the SidG protein as determined by differences in protease sensitivity in vitro. These data suggest that IcmSW binding to effectors could enhance effector protein delivery by mediating a conformational change that facilitates T4SS recognition of a translocation domain located in the carboxyl region of the effector protein.     

p53 promotes the fidelity of DNA end-joining activity by, in part, enhancing the expression of heterogeneous nuclear ribonucleoprotein G

Many studies have suggested the involvement of wild-type (wt) p53 in the repair of DNA double-strand breaks (DSBs) via DNA end-joining (EJ) process. To investigate this possibility, we compared the capacity and fidelity of DNA EJ in RKO cells containing wt p53 and RKO cells containing no p53 (RKO cells with p53 knockdown). The p53 knockdown cells showed lower fidelity of DNA EJ compared to the control RKO cells. The DNA end-protection assay revealed the association of a protein complex including heterogeneous nuclear ribonucleoprotein G (hnRNP G) with the DNA ends in RKO cells containing wt p53, but not with the DNA ends in RKO cells with p53 knockdown. Depletion of endogenous hnRNP G notably diminished the fidelity of EJ in RKO cells expressing wt p53. Moreover, an ectopic expression of hnRNP G significantly enhanced the fidelity of DNA EJ and the protection of DNA ends in human cancer cells lacking hnRNP G protein or containing mutant hnRNP G. Finally, using recombinant hnRNP G proteins, we demonstrated the hnRNP G protein is able to bind to and protect DNA ends from degradation of nucleases. Our results suggest that wt p53 modulates DNA DSB repair by, in part, inducing hnRNP G, and the ability of hnRNP G to bind and protect DNA ends may contribute its ability to promote the fidelity of DNA EJ.     

Cyclin-dependent kinase inhibitors sensitize tumor cells to nutlin-induced apoptosis: a potent drug combination

Current chemotherapy focuses on the use of genotoxic drugs that may induce general DNA damage in cancer cells but also high levels of toxicity in normal tissues. Nongenotoxic activation of p53 by targeting specific molecular pathways therefore provides an attractive therapeutic strategy in cancers with wild-type p53. Here, we explored the antitumor potential of cyclin-dependent kinase (CDK) inhibitors in combination with a small molecule inhibitor of p53-murine double minute 2 (MDM2) interaction. We show that low doses of CDK inhibitors roscovitine and DRB synergize with the MDM2 antagonist nutlin-3a in the induction of p53 activity and promote p53-dependent apoptosis in a dose- and time-dependent manner. Statistical measurement of the combination effects shows that the drug combination is additive on the reduction of cell viability and synergistic on inducing apoptosis, a critical end point of cytotoxic drugs. The degree of apoptosis observed 24 to 48 h after drug treatment correlated with the accumulation of p53 protein and concomitant induction of proapoptotic proteins Puma and PIG3. The antiproliferative and cytotoxic effects of this drug combination are validated in a range of tumor-derived cells including melanoma, colon carcinoma, breast adenocarcinoma, and hepatocarcinoma cells. Furthermore, this drug combination does not induce phosphorylation of Ser(15) on p53 and does not induce genotoxic stress in the cell. Given that many cytotoxic drugs rely on their ability to induce apoptosis via DNA damage-mediated activation of p53, the data presented here may provide a new therapeutic approach for the use of CDK inhibitors and MDM2 antagonists in combinatorial drug therapy.     

Human variants of O6-alkylguanine-DNA alkyltransferase

This article summarizes the current understanding of known variant forms of the MGMT gene that encode an altered protein. Epidemiological studies have been carried out to test whether these alterations are associated with altered cancer risk. Laboratory studies using recombinant proteins and cells expressing the known variants have investigated the possible effects of these sequence alterations on the ability of the encoded O(6)-alkylguanine-DNA alkyltransferase protein to protect cells from alkylation damage and to respond to therapeutic inactivators currently undergoing trials for cancer chemotherapy.     

Density functional study of closed-shell attraction on X(ML)<Subscript>3</Subscript><Superscript>+</Superscript>(<Emphasis Type="Italic">X</Emphasis> = O,S, Se; <Emphasis Type="Italic">M</Emphasis> = Au,Ag, Cu) systems

With the help of quantum mechanical calculations, we have examined the series of central system X(ML)₃ ⁺(X = O, S, Se; M = Au, Ag, Cu). Using a scalar–relativistic density functional approach, we studied the geometry structures, Mulliken populations and charges of the systems. Structure parameters of the experimental systems are reproduced well with Xα method. The metallophilic interaction energy is analyzed and decomposed. For the systems with different central atoms and different metal atoms, the nature of the metallophilic attraction interaction is analyzed.