Starch physicochemical properties and their associations with microsatellite alleles of starch-synthesizing genes in a rice RIL population

The physicochemical properties of starch, such as apparent amylose content, gelatinization temperature, and pasting viscosities, determine the eating, cooking, and processing qualities of various products of rice. A recombinant inbred line (RIL) population derived from the reciprocal cross of Lemont (a premium high-quality tropical japonica rice) and Jiayu 293 (a high-yield but low-quality indica rice) was used to test the association of microsatellite markers of starch-synthesizing genes with starch quality parameters. The results confirmed the association of Wx and starch synthase I (SSI) alleles with various starch properties measured in rice flour. However, the starch properties were not associated with the starch branching enzyme 1 (SBE 1) gene alleles.     

Differential inhibition of human platelet aggregation by selected Allium thiosulfinates

Thiosulfinates (TSs) have been implicated as a principle source of the antiplatelet property of raw onion and garlic juice. The in vitro responses of human platelets to dosages of four TSs were measured using whole blood aggregometry and compared by regression analysis. Of the compounds evaluated, methyl methane-TS (MMTS), propyl propane-TS (PPTS), and 2-propenyl 2-propene-TS (allicin) are present in freshly cut Allium vegetables, whereas ethyl ethane-TS (EETS) has not been detected. All TSs were synthesized using a model reaction system. PPTS and allicin had the strongest antiplatelet activity at 0.4 mM, inhibiting aggregation by 90 and 89%, respectively. At the same concentration, EETS and MMTS were significantly weaker, inhibiting 74 and 26%, respectively. Combinations of TSs were not additive in their inhibition of aggregation, indicating that the antiplatelet potential of Allium extracts cannot be easily predicted by quantifying organosulfur components. EETS, PPTS, and allicin were significantly more potent platelet inhibitors than aspirin at nearly equivalent concentrations.     

Antioxidative and hepatoprotective effects of Antrodia camphorata extract

Antrodia camphorata (A. camphorata) is well-known in Taiwan as a traditional Chinese medicine. The purpose of this study was to evaluate the ability of A. camphorata extracts to protect against oxidative stress in vitro and against carbon tetrachloride (CCl(4))-induced hepatic injury in vivo. An extract of A. camphorata inhibited nonenzymatic iron-induced lipid peroxidation in rat brain homogenates with an IC(50) value about 3.1 mg/mL. It also scavenged the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH). The dose of the A. camphorata extract resulting in a decrease of 0.20 in the absorbance of DPPH was about 31 +/- 0.7 microg/mL. Furthermore, an A. camphorata extract dose-dependently (250-1250 mg/kg) ameliorated the increase in plasma aspartate aminotransferase (GOT) and alanine aminotransferase (GPT) levels caused by chronic repeated CCl(4) intoxication in mice. Moreover, A. camphorata extract significantly improved the CCl(4)-induced increase in hepatic glutathione peroxidase, reductase, and CCl(4)-induced decrease in superoxide dismutase activities. It also restored the decrement in the glutathione content and catalase activity of hepatic tissues in CCl(4)-intoxicated mice. Furthermore, it also dose-dependently inhibited the formation of lipid peroxidative products during CCl(4) treatment. Histopathological changes of hepatic lesions induced by CCl(4) were significantly ameliorated by treatment with an A. camphorata extract in a dose-dependent manner. These results suggest that A. camphorata extract exerts effective protection against chronic chemical-induced hepatic injury in vivo, by mediating antioxidative and free radical scavenging activities.     

Crystal structure of the carboxyltransferase domain of acetyl-coenzyme A carboxylase

Acetyl-coenzyme A carboxylases (ACCs) are required for the biosynthesis and oxidation of long-chain fatty acids. They are targets for therapeutics against obesity and diabetes, and several herbicides function by inhibiting their carboxyltransferase (CT) domain. We determined the crystal structure of the free enzyme and the coenzyme A complex of yeast CT at 2.7 angstrom resolution and found that it comprises two domains, both belonging to the crotonase/ClpP superfamily. The active site is at the interface of a dimer. Mutagenesis and kinetic studies reveal the functional roles of conserved residues here. The herbicides target the active site of CT, providing a lead for inhibitor development against human ACCs.     

From a single-band metal to a high-temperature superconductor via two thermal phase transitions

The nature of the pseudogap phase of cuprate high-temperature superconductors is a major unsolved problem in condensed matter physics. We studied the commencement of the pseudogap state at temperature T* using three different techniques (angle-resolved photoemission spectroscopy, polar Kerr effect, and time-resolved reflectivity) on the same optimally doped Bi2201 crystals. We observed the coincident, abrupt onset at T* of a particle-hole asymmetric antinodal gap in the electronic spectrum, a Kerr rotation in the reflected light polarization, and a change in the ultrafast relaxational dynamics, consistent with a phase transition. Upon further cooling, spectroscopic signatures of superconductivity begin to grow close to the superconducting transition temperature (T(c)), entangled in an energy-momentum-dependent manner with the preexisting pseudogap features, ushering in a ground state with coexisting orders.     

Ultrafast vibrational dynamics at water interfaces

Time-resolved sum-frequency vibrational spectroscopy permits the study of hitherto neglected ultrafast vibrational dynamics of neat water interfaces. Measurements on interfacial bonded OH stretch modes revealed relaxation behavior on sub-picosecond time scales in close resemblance to that of bulk water. Vibrational excitation is followed by spectral diffusion, vibrational relaxation, and thermalization in the hydrogen-bonding network. Dephasing of the excitation occurs in 相似文献   

云南油杉叶锈病及其病原菌的研究

本文报道了对云南油杉叶锈病(the needle rust of Keteleeria evelyniana)及其病原多年系统研究的结果。经生物学特性研究,己知油杉金锈 Chrysomyxa keteleeriae(Tai)Wang etPeterson 冬孢子萌发的最适条件为:温度20℃左右,相对湿度100%或100%加水滴;持续光照则有强烈的抑制萌发作用。担孢子萌发的最适条件是:温度24℃左右,相对湿度75%。湿度过高,萌发率反而下降;萌发也受持续光照的抑制。系统观察和以担孢子悬浮液为接种体的室内外人工接种实验,确认油杉金锈具有单主寄生短循环型(automicrocyclic)生活史,它以菌丝体在针叶病斑组织中越冬,次年春末夏初产生冬孢子柱,冬孢子不经休眠即可萌发,以担孢子为初侵染源,侵染当年抽生的幼嫩针叶,当年发病,且不再产生新的接种体,故云南油杉叶锈病为单循环病害(singlecycle disease)。     

Biosynthesis of the enediyne antitumor antibiotic C-1027

C-1027 is a potent antitumor agent with a previously undescribed molecular architecture and mode of action. Cloning and characterization of the 85-kilobase C-1027 biosynthesis gene cluster from Streptomyces globisporus revealed (i) an iterative type I polyketide synthase that is distinct from any bacterial polyketide synthases known to date, (ii) a general polyketide pathway for the biosynthesis of both the 9- and 10-membered enediyne antibiotics, and (iii) a convergent biosynthetic strategy for the C-1027 chromophore from four building blocks. Manipulation of genes governing C-1027 biosynthesis allowed us to produce an enediyne compound in a predicted manner.     

Gate-variable optical transitions in graphene

Two-dimensional graphene monolayers and bilayers exhibit fascinating electrical transport behaviors. Using infrared spectroscopy, we find that they also have strong interband transitions and that their optical transitions can be substantially modified through electrical gating, much like electrical transport in field-effect transistors. This gate dependence of interband transitions adds a valuable dimension for optically probing graphene band structure. For a graphene monolayer, it yields directly the linear band dispersion of Dirac fermions, whereas in a bilayer, it reveals a dominating van Hove singularity arising from interlayer coupling. The strong and layer-dependent optical transitions of graphene and the tunability by simple electrical gating hold promise for new applications in infrared optics and optoelectronics.     

A thermally re-mendable cross-linked polymeric material

We have developed a transparent organic polymeric material that can repeatedly mend or "re-mend" itself under mild conditions. The material is a tough solid at room temperature and below with mechanical properties equaling those of commercial epoxy resins. At temperatures above 120 degrees C, approximately 30% (as determined by solid-state nuclear magnetic resonance spectroscopy) of "intermonomer" linkages disconnect but then reconnect upon cooling, This process is fully reversible and can be used to restore a fractured part of the polymer multiple times, and it does not require additional ingredients such as a catalyst, additional monomer, or special surface treatment of the fractured interface.