Beta structures of alternating polypeptides and their possible prebiotic significance.

A survey of the commonest amino acids formed in prebiotic conditions suggests that the earliest form of genetic coding may have specified polypeptides with a strong tendency to form stable Beta-sheet structure. Poly(Val-Lys), like other polypeptides in which hydrophobic and hydrophilic residues alternate, tends to form Beta structures. We show that bilayers with a hydrophobic interior and a hydrophilic exterior may be present in aqueous solution.     

Molecular structure and biological function of proliferating cell nuclear antigen

Proliferating cell nuclear antigen (PCNA) is the core component of replication complex in eukaryote. As a processive factor of DNA polymerase delta, PCNA coordinates the replication process by interacting with various replication proteins. PCNA appears to play an essential role in many cell events, such as DNA damage repair, cell cycle regulation, and apoptosis, through the coordination or organization of different partners. PCNA is an essential factor in cell proliferation, and has clinical significance in tumor research. In this article we review the functional structure of PCNA, which acts as a function switch in different cell events.     

Molecular structure and biological function of proliferating cell nuclear antigen

Proliferating cell nuclear antigen (PCNA) is the core component of replication complex in eukaryote. As a processive factor of DNA polymerase delta, PCNA coordinates the replication process by interacting with various replication proteins. PCNA appears to play an essential role in many cell events, such as DNA damage repair, cell cycle regulation, and apoptosis, through the coordination or organization of different partners. PCNA is an essential factor in cell proliferation, and has clinical significance in tumor research. In this article we review the functional structure of PCNA, which acts as a function switch in different cell events.     

分子生物学技术及其在环境样品微生物分析中的应用

综述了荧光原位杂交(FISH)、多聚酶链式反应(PCR)、DNA克隆及DNA测序等分子生物学技术,并将这些分子生物学技术应用到淡水水体底泥厌氧氨氧化茵(anammox菌)和好氧氨氧化菌的原位检测中,从底泥样品中鉴别出这两种细菌,其中好氧氨氧化菌属于亚硝酸单胞菌属,厌氧氨氧化菌属于anammox菌的Brocadia分支,为进一步研究淡水环境中氮的微生物循环过程提供了一定的依据．     

Effect of protein packing structure on side-chain methyl rotor conformations

Protein molecules undergo a series of conformational fluctuations ranging in degree from atomic vibrations to transient denaturation, even in physiological conditions. The rotational motions of amino acid side chains form an important subset of the types of fluctuation a protein can undergo. NMR and molecular dynamics have shown that methyl groups in proteins are not held in fixed positions, but spin rapidly around their rotor axes. The question then arises as to whether methyl groups in proteins predominantly adopt the 'staggered' conformation, favoured by the intrinsic barrier to rotation of these groups, or whether cooperative packing effects in the folded protein perturb the average configurations to higher torsional energy. We report here an investigation of the rotational conformations of the methyl groups of aliphatic side chains in the protein crambin by neutron diffraction. We find that in the time-averaged structure of this protein, the majority of methyl rotors adopt the staggered conformation. This is consistent with rotation being a quantized event consisting of rapid reorientations of approximately 120 degrees steps to positions of highest stability. The fact that the local environment does not dictate the low energy state of methyl groups suggests that within the seemingly close-packed interior structure of a protein, mutual packing accommodation occurs as a consequence of the inherent flexibility and small packing defects in protein structures.     

太阳中微子问题及其可能的解释

介绍了2个太阳中微子问题和解决太阳中微子问题的几种可能解释,并详细讨论了太阳中微子振荡方案.如果采用小混合角(SMA)方案,那么,这2种味的中微子的质量之差不超过2.323 78×10-3 eV;如果用真空振荡(VAC)方案,那么,这2种味的中微子的质量之差不超过8.944 2×10-6 eV.认为如果中微子是暗物质的候选者,且中微子的静止质量要大于1 eV,那么2种中微子质量之差至多为2.7×10-6 eV.     

Stratification features of Tamarix cone and its possible age significance

Establishing age series of stratum is one of the most important ways to rebuild the paleo-geographical environment. The dating methods from lacustrine laminated clay to ^210Pb, ^137Cs, and ^14C have also been used to estimate the age of different geological materials. But different methods require different testing materials and are     

甲烷其它相态及其意义

对水溶和水合这两种不为人熟知的甲烷相态进行了介绍，分析了水溶甲烷量估算方法和影响因素、以及对矿井安全生产可能构成的潜在威胁。根据水合状态的瓦斯分解需要吸收大量的热而难以在短时间内大量集中涌出的物理化学特性，结合初步试验结果论述了利用水合机理防治矿井瓦斯事故的可行性。理论研究与初步实验表明，利用水合技术防治矿井事故的技术路线是可行的。另外，随着采深的增加，水溶甲烷将对煤矿安全生产构成威胁。     

Molecular determinants and guided evolution of species-specific RNA editing

Most RNA editing systems are mechanistically diverse, informationally restorative, and scattershot in eukaryotic lineages. In contrast, genetic recoding by adenosine-to-inosine RNA editing seems common in animals; usually, altering highly conserved or invariant coding positions in proteins. Here I report striking variation between species in the recoding of synaptotagmin I (sytI). Fruitflies, mosquitoes and butterflies possess shared and species-specific sytI editing sites, all within a single exon. Honeybees, beetles and roaches do not edit sytI. The editing machinery is usually directed to modify particular adenosines by information stored in intron-mediated RNA structures. Combining comparative genomics of 34 species with mutational analysis reveals that complex, multi-domain, pre-mRNA structures solely determine species-appropriate RNA editing. One of these is a previously unreported long-range pseudoknot. I show that small changes to intronic sequences, far removed from an editing site, can transfer the species specificity of editing between RNA substrates. Taken together, these data support a phylogeny of sytI gene editing spanning more than 250 million years of hexapod evolution. The results also provide models for the genesis of RNA editing sites through the stepwise addition of structural domains, or by short walks through sequence space from ancestral structures.     

Primary structure and expression from complementary DNA of skeletal muscle ryanodine receptor

The sequence of 5,037 amino acids composing the ryanodine receptor from rabbit skeletal muscle sarcoplasmic reticulum has been deduced by cloning and sequencing the complementary DNA. The predicted structure suggests that the calcium release channel activity resides in the C-terminal region of the receptor molecule, whereas the remaining portion constitutes the 'foot' structure spanning the junctional gap between the sarcoplasmic reticulum and the transverse tubule.