DNA conformation, dynamics, and interactions in solution

The conformation and dynamics of the d(CGCGAATTCGCG) duplex, its analogs containing mismatched base pairs and helix interruptions, and its complexes with actinomycin and Netropsin, bound separately and simultaneously, have been investigated by nuclear magnetic resonance spectroscopy in aqueous solution. Structural information has been deduced from chemical shift and nuclear Overhauser effect parameters, while the kinetics have been probed from line width and saturation recovery experiments on proton and phosphorus markers at the individual base pair level. These studies lead to an improved understanding of the role of nucleic acid sequence on the structure, flexibility, and conformational interconversions in the duplex state. The nuclear magnetic resonance measurements readily identify helix modification and antibiotic binding sites on the nucleic acid and estimate the extent to which the observed conformational and dynamic perturbations are transmitted to adjacent base pair regions.     

Reactive and nonreactive scattering of H2 from a metal surface is electronically adiabatic

The Born-Oppenheimer approximation of uncoupled electronic and nuclear motion is a standard tool of the computational chemist. However, its validity for molecule-metal surface reactions, which are important to heterogeneous catalysis, has been questioned because of the possibility of electron-hole pair excitations. We have performed experiments and calculations on the scattering of molecular hydrogen from a catalytically relevant metal surface, obtaining absolute probabilities for changes in the molecule's velocity parallel to the representative Pt(111) surface. The comparison for in-plane and out-of-plane scattering and results for dissociative chemisorption in the same system show that for hydrogen-metal systems, reaction and diffractive scattering can be accurately described using the Born-Oppenheimer approximation.     

NMR detection of structures in the HIV-1 5'-leader RNA that regulate genome packaging

The 5'-leader of the HIV-1 genome regulates multiple functions during viral replication via mechanisms that have yet to be established. We developed a nuclear magnetic resonance approach that enabled direct detection of structural elements within the intact leader (712-nucleotide dimer) that are critical for genome packaging. Residues spanning the gag start codon (AUG) form a hairpin in the monomeric leader and base pair with residues of the unique-5' region (U5) in the dimer. U5:AUG formation promotes dimerization by displacing and exposing a dimer-promoting hairpin and enhances binding by the nucleocapsid (NC) protein, which is the cognate domain of the viral Gag polyprotein that directs packaging. Our findings support a packaging mechanism in which translation, dimerization, NC binding, and packaging are regulated by a common RNA structural switch.     

水稻雄性败育初探

水稻雄性育性通常受一对可育基因和质、核间相应诱导物质(RNA)共同作用,质、核间育性诱导物质的协调与否,能影响基因性状的表达,目前三系中的“不育”系就多为这种类型。“光(温)敏核不育”则还受一对光(温)敏育性基因及相应的光(温)敏核诱导物质(RNA)共同作用,在特定光(温)条件下能表现可育,条件不具备时则表现为“不育”。因这两种“不育”均非不育基因作用,实质上应是败育。     

论油菜显性核不育材料基因的互作--兼与李树林先生商榷

依据李树林先生在甘蓝型油菜细胞核雄性不育系23AB的研究^[1-5],以及董振生^[6-9]在白菜型油菜显性细胞核雄性不育系896AB的研究结果,用全不育株与恢复株测交,F2代可能的育性比出现全可育,可育株与不育株3：1,13：3的育性分离资料分析,认为油菜显性核不育的遗传不宜用上位抑制来解释,而应用抑制作用解释较为妥当,即育性是由一对显性不育基因MSMS和一对显性恢复基因RfRf互作控制,且显性恢复基因能抑制不育基因不育性的表达,使育性恢复可育。     

The retina of the newborn human infant

We have examined a pair of eyes from a normal, full-term infant who died at 8 days as a result of accidental injury. Eyes were obtained immediately after death, fixed, and sectioned for light microscopy. Results from both eyes were substantially the same. The macular region was still drastically immature at 1 week. Even though a foveal depression existed, all cell layers were still present across it. Furthermore, the inner nuclear layer was divided into two separate layers. The receptor layer was reduced to one or two cells thick; receptors had both inner and outer segments, but they were very short and stumpy. The region of immaturity covered about 5 degrees of the retina. These findings suggest that the central region of a human infant's retina is probably not fully functional at birth.     

Strategic command, control, communications, and intelligence

Command, control, communications, and intelligence (C(3)l) for nuclear forces are essential elements in the deterrence of nuclear war. The present C(3)l) system has vulnerabilities associated with its reliability, survivability, and endurance under attack, thereby weakening deterrence by increasing the ambiguity in our capabilities. Development of a reliable and enduring C(3)l) system would reduce this ambiguity. Its reliable, positive control of nuclear forces would give the national leadership more time to assess situations, ensure discriminate retaliation, and improve our ability to manage crises in general. These capabilities could help to stop a war rapidly should one start. A reliable and enduring C(3)1) system will be needed for a long time to come, even if a freeze on strategic nuclear forces is accomplished or other arms control successes achieved. Indeed, C(3)l) may be the best source today of confidence-building measures to reduce tensions and the threat of nuclear catastrophe.     

柞蚕核型多角体病毒sod基因核心序列的克隆与分析

根据多种鳞翅目昆虫NPV sod基因的保守区序列设计引物,克隆了柞蚕NPV的sod基因中300个核苷酸的核心区序列.通过同源性比较发现,柞蚕NPV的sod基因与云杉卷叶蛾(Choristioneure fumiferana)和黄杉毒蛾(Orgyia pseudotsugata)NPV的sod基因的同源性较高,分别为80.1%和76.6%,而与家蚕NPV和苜蓿尺蠖NPV的同源性相对较远.     

Dynamics of hydrogen bromide dissolution in the ground and excited states

The dissolution of acids is one of the most fundamental solvation processes, and an important issue is the nature of the hydration complex resulting in ion pair formation. We used femtosecond pump-probe spectroscopy to show that five water molecules are necessary for complete dissolution of a hydrogen bromide molecule to form the contact ion pair H+.Br-(H2O)n in the electronic ground state. In smaller mixed clusters (n < 5), the ion pair formation can be photoinduced by electronic excitation.     

银杏叶黄瓜与普通黄瓜性状比较研究

本试验结果表明银杏叶性状为一对核基因控制的隐性性状。与普通黄瓜相比，银杏叶黄瓜叶缘上卷、叶片较小且呈匙状，其叶片叶绿素含量及光合速率无明显差异，瓜条性状亦一致。与前人报道的银杏叶不同。     

滇—型和BT型杂交稻育性遗传和不育机理研究

 以花粉可育率为主要遗传指标,对滇一型和BT型“三系”以及杂种F₁、F₂、BC₁和AF₁(不×[保×恢])等世代的育性进行了观察分析。结果表明:滇一型和BT型不育系花粉败育以染败为主。二者不育系的不育基因和恢复系的恢复基因两两相互等位。供试材料有部分杂交组合表现为一对育性核基因与细胞质基因共同控制的遗传,而另一部分杂交组合表现为两对育性核基因与细胞质基因共同控制的遗传。恢复基因(R₁、R₂)的作用有强弱之分,并表现明显的加性效应。据此初步认为:粳型杂交水稻的育性基因型因组合不同而不尽相同,同一不育系或恢复系在不同的组合中可能表现不同的育性基因型。     

A point mutation in the c-myc locus of a Burkitt lymphoma abolishes binding of a nuclear protein

A 20-base pair region in the first intron of the human c-myc gene was identified as the binding site of a nuclear protein. This binding site is mutated in five out of seven Burkitt lymphomas sequenced to date. To investigate the protein-recognition region in greater detail, the abnormal c-myc allele from a Burkitt lymphoma line (PA682) that carries a t(8;22) chromosomal translocation was used. A point mutation in the binding region of the PA682 c-myc DNA abolished binding of this nuclear protein. This protein may be an important factor for control of c-myc expression, and mutations in its recognition sequence may be associated with c-myc activation in many cases of Burkitt lymphoma.     

平菇品种的筛选提纯与复壮

针对我区引进平菇品种多,产量不高,品质欠佳,转代次数不明,适应性差等问题,我们从引进品种中选出表现较好的三个平菇品种进行提纯复壮,通过三种处理方法的对比试验,结果表明：单孢子配对复壮得到的菌株,菌丝生长速度快,出菇早,抗性强,产量高,菇质好,但选育方法要求高,条件严格,操作技术就复杂;而上述组织分离去得到的菌株,产量虽比孢子选育稍低,但方法简便易行。结论：应定期对优良平菇品种进行提纯复壮,以保持原品种的优良生育特性。     

Endonucleolytic activity that cleaves immunoglobulin recombination sequences

An endonucleolytic activity has been identified in nuclear extracts of chick embryo bursa and mouse fetal liver cells. The activity introduces a double-strand cut in the vicinity of the recombination site of immunoglobulin joining gene segments. The cleavage occurs at the dinucleotide pair TG-AC. This activity is a good candidate for the putative endonuclease involved in recombination of the immunoglobulin variable, diversity, and joining regions. It is distinct from the endonuclease activities previously reported by others.     

日本囊对虾Ran基因的克隆表达与蛋白质GTP结合活性分析

在对虾抑制性差减杂交（suppression subtractive hybridization,SSH）研究过程中,首次发现一段经同源比较为Ran基因的部分序列,在抗病对虾中上调表达.为了进一步探索对虾Ran基因的功能,通过RACE-PCR的方法克隆得到了对虾Ran基因全长共1441个碱基,其中开放阅读框为645个碱基,共编码215个氨基酸,这是首次在海洋无脊椎动物体内克隆到该基因.本研究还将该基因克隆到原核表达载体PGEX-4T-2中并转化大肠杆菌BL21,37℃下诱导6h,超声裂解表达菌株,结果表明GST-Ran融合蛋白在大肠杆菌中为可溶性表达,蛋白大小约为50ku,经纯化得到了纯度大于90%的GST-Ran融合蛋白.随后的GTP结合试验验证了Ran蛋白具有GTP结合活性.     

AEC to Referee, Not Promote, Industry

A major turnabout in the attitude of the Atomic Energy Commission toward the nuclear power industry was signaled last week by the ntew AEC chairman James R. Schlesinger. With patrician froideur, Schlesinger informed a mass gathering of the nuclear power industry at Bal Harbour, Florida, that from henceforth the AEC woLuld act as the referee of nuclear power, not its promoter. Saying he would dispense with the "anecdotes and clumsy jests" customary on such occasions, Schlesinger served notice on the nuclear banqueters that their cozy relationship with the AEC was at an end. The industry should not expect the AEC to fight its battles: it should take its own case to the public-as the Sierra Club does. Nor did the AEC intend to bend the rules in industry's favor. "We have had a fair amount of advice on how to evade the clear mandate of the federal courts. It is advice we did not think proper to accept," Schlesinger said. Even on matters of engineering quality, the diners were told they knew full well they had "reason to blush." Roused out of any postprandial euphoria by this glacial disdain, the industry representatives heard the new chairman announce the following radical upheavals in official AEC philosophy.     

Electronic spin storage in an electrically readable nuclear spin memory with a lifetime >100 seconds

Electron spins are strong candidates with which to implement spintronics because they are both mobile and able to be manipulated. The relatively short lifetimes of electron spins, however, present a problem for the long-term storage of spin information. We demonstrated an ensemble nuclear spin memory in phosphorous-doped silicon, which can be read out electrically and has a lifetime exceeding 100 seconds. The electronic spin information can be mapped onto and stored in the nuclear spin of the phosphorus donors, and the nuclear spins can then be repetitively read out electrically for time periods that exceed the electron spin lifetime. We discuss how this memory can be used in conjunction with other silicon spintronic devices.     

Coupling and entangling of quantum states in quantum dot molecules

We demonstrate coupling and entangling of quantum states in a pair of vertically aligned, self-assembled quantum dots by studying the emission of an interacting electron-hole pair (exciton) in a single dot molecule as a function of the separation between the dots. An interaction-induced energy splitting of the exciton is observed that exceeds 30 millielectron volts for a dot layer separation of 4 nanometers. The results are interpreted by mapping the tunneling of a particle in a double dot to the problem of a single spin. The electron-hole complex is shown to be equivalent to entangled states of two interacting spins.