An Application of Classical Molecular Dynamics Simulation and AB Initio Density-Functional Calculation in Surface Physics

Abstract

Classical molecular dynamics simulation and ab initio mixed basis Car-Parrinello methods are discussed and applied to the investigation of the results of a recently performed STM-based experiment involving the adsorption of C₆₀ molecules on the dimerized Si surface. We show that these methods are capable of providing the theoretical basis for this experiment and test the validity of the associated conjectures.

A mixed-basis all-electron formalism for the Car-Parrinello method is proposed to obtain the detailed understanding of the electronic states and dynamics of surface structure. A band structure calculation using this formalism is performed for the c(4 × 3) structure of C₆₀ adsorbed on Si (100) surface and is compared with the experimental results.     

The Increase of Indophenol Reducing Value of Boiled Potato (3)

The contribution of the system of DOPA, tyrosine and polyphenol oxidase to the remarkable increase of indophenol reducing value during the boiling procedure of the aqueous extract of potato was investigated and discussed. When the red solution of resulting DOPA-chrome by the action of polyphenol oxidase on DOPA and tyrosine at the level of potato juice was heated, the solution turned from red to colorless and simultaneously the indophenol reducing value increased remarkably. And it seems that the resulting indophenol reducing substance is a sort of reductone, 5,6-dihydroxyindole. The system of other polyphenols gave little increase of indophenol reducing value. Therefore the system of DOPA, tryosine and polyphenol oxidase is specific to the above increase.     

Isolation and Characterization of a Novel Antitumor Substance,Renastacarcin

A new antitumor substance designated renastacarcin has been isolated from the cultured broth of Streptomyces violascens by means of DEAE-cellulose and Sephadex G-100 column chromatography. The homogeneity of renastacarcin was confirmed by electrophoreses on a polyacrylamide gel and a cellulose acetate membrane as well as by ultracentrifugal analysis. A sedimentation coefficient at 55,430 rpm was found to be 2.12S and the molecular weight was calculated to be 34,500.     

Directing p53 to induce autophagy

Comment on: Naidu SR, et al. Cell Cycle 2012; 11:2717-28.     

SYCP3-like X-linked 2 is expressed in meiotic germ cells and interacts with synaptonemal complex central element protein 2 and histone acetyltransferase TIP60

Meiosis is the process by which diploid germ cells produce haploid gametes. A key event is the formation of the synaptonemal complex. In the pachytene stage, the unpaired regions of X and Y chromosomes form a specialized structure, the XY body, within which gene expression is mostly silenced. In the present study, we showed that SYCP3-like X-linked 2 (SLX2, 1700013H16Rik), a novel member of XLR (X-linked Lymphocyte-Regulated) family, was specifically expressed in meiotic germ cells. In the spermatocyte SLX2 was distributed in the nucleus of germ cells at the preleptotene, leptotene and zygotene stages and is then restricted to the XY body at the pachytene stage. This localization change is coincident with that of phosphorylated histone H2AX (γH2AX), a well-known component of the sex body. Through yeast two-hybrid screening and coimmunoprecipitation assays, we demonstrated that SLX2 interacts with synaptonemal complex central element protein 2 (SYCE2), an important component of synaptonemal complex, and histone acetyltransferase TIP60, which has been implicated in remodeling phospho-H2AX-containing nucleosomes at sites of DNA damage. These results suggest that SLX2 might be involved in DNA recombination, synaptonemal complex formation as well as sex body maintenance during meiosis.     

Cytotoxic Activity of New Phenolic Compounds from Vietnamese Caesalpinia sappan

Two new phenolic compounds, caesalpiniaphenols G–H (1 and 2), were isolated from Vietnamese Caesalpinia sappan heartwood. The chemical structures were established mainly by extensive spectroscopic studies and chemical evidence. Compounds 1 and 2 showed potent inhibitory activity against HL-60 cancer cell lines with respective IC₅₀ values of 16.7 and 22.5 µg/mL. Treating HL-60 cells with various concentrations of 1 resulted in growth inhibition and the induction of apoptosis.     

猕猴桃60Co-γ射线辐射诱变育种适宜剂量的研究

以果肉红色的‘红阳’猕猴桃、果肉黄色‘桂海4号’猕猴桃和果肉绿色的‘长果’猕猴桃的枝条为试材,用4种剂量的60Co-γ射线辐射处理,以未照射枝条为对照,采用随机区组设计进行田间嫁接。对嫁接成活率、植株生长量的调查分析。结果显示:在25～150Gy辐射剂量范围内,随辐射剂量的加大,对嫁接成活率及生长的抑制作用逐渐增强。不同品种的猕猴桃对辐射的敏感性差异较大。3个品种猕猴桃辐射半致死剂量分别为50.6Gy(红阳)、64.4Gy(桂海4号)、71.7Gy(长果猕猴桃)。试验结果可以为猕猴桃辐射育种适宜剂量的确定提供依据。     

No effect of extremely low-frequency magnetic field observed on cell growth or initial response of cell proliferation in human cancer cell lines

An effect on the tumor promotion process, as represented by accelerated cell growth, has been indicated as one example of areas that demonstrate the possibility of biological effects of extremely-low frequency magnetic fields. We, therefore, exposed the five cell lines (HL-60, K-562, MCF-7, A-375, and H4) derived from human tumors to a magnetic field for 3 days to investigate the effects on cell growth. Prior to exposure or sham exposure, the cells were precultured for 2 days in low serum conditions. The number of growing cells was counted in a blind manner. To investigate the effect on the initial response of cell proliferation, two cell lines were synchronized in G1 phase by serum starvation and then exposed to a magnetic field for 18 h (H4 cells) or 24 h (MCF-7 cells), both with and without serum stimulation. The rate of DNA synthesis, taken as a measure of the cell proliferation, was determined by following the incorporation of [(3)H]-thymidine into the DNA. Three different magnetic field polarizations at both 50 and 60 Hz were used: linearly polarized (vertical); circularly polarized; and an elliptically polarized field. Magnetic field flux densities were set at 500, 100, 20 and 2 microT (rms) for the vertical field and at 500 microT (rms) for the rotating fields. No effect of magnetic field exposure was observed on either cell growth or the initial response of cell proliferation.     

Cryptosporidium GP60 genotypes from humans and domesticated animals in Australia, North America and Europe

To investigate the molecular epidemiology of Cryptosporidium species in children in Australia, fecal specimens from 50 Australian children with gastrointestinal symptoms and seven isolates from Australian neonatal dairy calves were genotyped and sub-genotyped at the 18S rDNA and GP60 loci, respectively, and compared with human and animal isolates collected from Europe, the US and Canada (n=35). Results revealed that the majority of the Australian human isolates were infected with C. hominis (41/50), while the remainder were infected with C. parvum. All the Australian cattle as well as cattle from US, Canada, UK and Switzerland were infected with C. parvum. Subtyping of 92 Cryptosporidium isolates at the GP60 locus identified seven subtype families of which six were identified in Australian isolates; four C. hominis subtypes and two C. parvum subtypes. Results suggest that although transmission is largely anthroponotic in Australia, cattle may be a source of sporadic human infections.