毛乌素沙地草地种植管理咨询系统的开发

 本研究初步开发了一个用于毛乌素沙地草地种植管理咨询的专家系统ASSG。这个系统将当地生态系统管理专家们的经验知识和对土壤水分动态的理论研究成果结合起来以产生对于土地利用和种植的作物种类及品种的最优管理策略和最适的植被覆盖率。本系统利用3个层次的推理过程和结构化的知识库,通过咨询过程—步步地引导用户得到最优种植管理策略。在每—层次的推理中,本系统提供给用户多重选择,根据用户的意愿进行下一步的推理。这一推理的交互作用机制为用户获得适宜的咨询结果提供了最大的便利性。本系统的主体部分山Turbo Prolog语言完成,该语言是一种用于开发专家系统的描述性语言。基于土壤水分平衡原理的最优植被覆盖率模型由C语言实现,并应用多语言编程技术将之嵌入程序主体中。系统的样本运行结果表明本系统运行便利,并能产生合理的种植管理策略。     

Regulation of cellulase synthesis in mycelial fungi: Participation of ATP and cyclic AMP

Summary ATP and cAMP in 4 strains of mycelial fungi were determined by luciferin-luciferase system and HPLC respectively. Cellulase synthesis was subject to the dual control of ATP and cAMP. No matter what carbon sourse was used, cellulase synthesis was repressed if intracellular ATP concentration was over 10^-7mg/ml. Exogenous cAMP could increase cellulase synthesis under depression conditions.     

Kinetics and mechanism of CO substitution of [η-CpFe(CO)3]PF6 with PPh3 in the presence of substituted pyridine N-oxide

The kinetics of substitution reactions of [η-CpFe(CO)₃]PF₆ with PPh₃ in the presence of R-PyOs have been studied. For all the R-PyOs (R = 4-OMe, 4-Me, 3,4-(CH)₄, 4-Ph, 3-Me, 2,3-(CH)₄, 2,6-Me₂, 2-Me), the reactions yeild the same product [η⁵-CpFe(CO)₂PPh₃]PF₆, according to a second-order rate law that is first order in concentrations of [η⁵-CpFe(CO)₃]PF₆ and of R-PyO but zero order in PPh₃ concentration. These results, along with the dependence of the reaction rate on the nature of R-PyO, are consistent with an associative mechanism. Activation parameters further support the bimmolecular nature of the reactions: ΔH^≠ = 13.4 ± 0.4 kcal mol⁻¹, ΔS^≠ = −19.1 ± 1.3 cal k⁻¹ mol⁻¹ for 4-PhPyO; ΔH^≠ = 12.3 ± 0.3 kcal mol⁻¹, ΔS^≠ = 24.7 ±1.0 cal K⁻¹ mol⁻¹ for 2-MePyO. For the various substituted pyridine N-oxides studied in this paper, the rates of reaction increase with the increasing electron-donating abilities of the substituents on the pyridine ring or N-oxide basicities, but decrease with increasing ¹⁷O chemical shifts of the N-oxides. Electronic and steric factors contributing to the reactivity of pyridine N-oxides have been quantitatively assessed.     

Melatonin and the pea aphid,Acyrthosiphon pisum

Pea aphids, Acyrthosiphon pisum, were fed on artificial diet containing various concentrations of melatonin. Under long-day conditions (16h light:8h dark) their progeny included males and virginoparous/oviparous (asexual/sexual) intermediate females, which normally occur only in short days or around critical night-length. Endogenous melatonin in pea aphids was measured by radioimmunoassay and verified by parallelism with a melatonin standard curve and by thin layer chromatography. However, melatonin titres showed large variations and although they tended to be higher during the scotophase than during the photophase they were not significantly different. The possibility of melatonin being involved in photoperiodism is discussed.     

Identification of Influenza C Virus Phosphoproteins

The HMV-II cells infected with influenza C virus were labeled with inorganic [³²P]phosphate to identify phosphorylated proteins. Analysis by radioimmunoprecipitation with antiviral serum or monoclonal antibodies revealed that three major structural proteins of the virus, hemagglutinin-esterase (HE), nucleoprotein (NP), and matrix protein (M1) are all phosphorylated in both infected cells and virions. It was also observed that, in the presence of trypsin (10 μg/ml), the unphosphorylated form of the HE glycoprotein was cleaved efficiently whereas the phosphorylated form was not, raising the possibility that phosphorylation of HE may influence its susceptibility to degradation by proteolytic enzymes.     

Stabilization of double-stranded oligonucleotides using backbone-linked disulfide bridges.

A convenient, practical route to the synthesis of disulfide-bridged oligonucleotides has been developed. Aliphatic linkers with terminal thiol groups have been attached to the phosphodiester backbones of partially or fully complementary oligonucleotide sequences and oxidized to yield covalently closed oligonucleotides with disulfide bridges. This procedure has been used to prepare a duplex with disulfide bridges at both ends and stem-loop sequences with single disulfide bridges. Oxidation of a self-complementary duplex possessing terminal thiol groups produced both hairpin and duplex structures with disulfide bridges, the relative proportions of each being dependent upon the reaction conditions. These bridged hairpin and duplex structures were shown to be interconvertible by reduction and re-oxidation. The melting profiles of disulfide-bridged oligonucleotides were compared with the same sequences without bridges and with sequences possessing triethylene glycol bridges, and in all cases the introduction of disulfide bridges resulted in a considerable increase in thermal stability. EcoRI endonuclease was capable of cleaving a disulfide-bridged duplex possessing a recognition site for this enzyme, thus supporting a lack of distortion of the recognition site. The disulfide bridges could be cleaved using a large excess of DTT to regenerate the corresponding sulfhydryl compounds. A study of the serum stabilities of disulfide-bridged oligonucleotides showed that the bridged duplexes were much more stable than their unmodified counterparts, whereas the rate of degradation of the stem-loop structures was more dependent upon the size of the loop than the presence or absence of the disulfide bridge. In summary, we have described a novel methodology, employing commercially available reagents, for the stabilization of oligonucleotide duplexes or stem-loop structures by disulfide bridge formation.