Toroidal网格C(d1,d2)的(d,4)-控制数

本文讨论二维Toroidal网格的(d,4)-控制数,得到如下结果:(1)如果,m≥2,G＝C(2m+1)或G＝C(2m+2,3),当d＝diam(G)+1时,Rd,4(G)＝2;(2)如果G＝C(d1,4)(d1≥3)或G＝C(d15)(d1≥9),当d＝diam(G)时,Rd,4(G)＝2.     

NMR study of parallel-stranded tetraplex formation by the hexadeoxynucleotide d(TG4T).

Multistranded DNA structures based upon guanine association have been proposed to be important in the structure of chromosome telomeres and in immunoglobulin class switching. Nucleic acids containing runs of guanine bases form a number of structures in vitro, including fold-back structures (Fig. 1a) and parallel-stranded quadruplex structures in DNA and RNA. The features of fold-back structures have now been determined at high-resolution. The different structures are probably based on a tetrad of hydrogen-bonded guanine bases (Fig. 1b), with buffer conditions and sequence effects mediating isomerization between the different forms. Here we use NMR spectroscopy to investigate the solution structure of the complex formed by the hexadeoxynucleotide d(TG4T) in the presence of sodium ions. We have observed the formation of a parallel-stranded quadruplex containing hydrogen-bonded tetrads of guanine. The parallel-stranded form differs significantly from the fold-back form, with individual nucleotide conformations being closer to those of B-form DNA.     

Role of poly(ADP-ribose) formation in DNA repair.

The abundant nuclear enzyme poly(ADP-ribose) polymerase catalyses the synthesis of poly(ADP-ribose) from nicotinamide adenine dinucleotide (NAD+). This protein has an N-terminal DNA-binding domain containing two zinc-fingers, which is linked to the C-terminal NAD(+)-binding domain by a short region containing several glutamic acid residues that are sites of auto-poly(ADP-ribosyl)ation. The intracellular production of poly(ADP-ribose) is induced by agents that generate strand interruptions in DNA. The branched homopolymer chains may attain a size of 200-300 residues but are rapidly degraded after synthesis. The function of poly(ADP-ribose) synthesis is not clear, although it seems to be required for DNA repair. Here we describe a human cell-free system that enables the role of poly(ADP-ribose) synthesis in DNA repair to be characterized. The results indicate that unmodified polymerase molecules bind tightly to DNA strand breaks; auto-poly(ADP-ribosyl)ation of the protein then effects its release and allows access to lesions for DNA repair enzymes.     

(4d+1)-正则图中的2d-因子

设d是一个正整数，G是一个（4d 1）-正则图，证明了若图G不含d 4条割边，则G有2d-因子，进而说明上述结果是最好的。     

一个包含算术函数S(d)和SL(d)的方程

目的研究一类包含算术函数S(n)及SL(n)方程的可解性。方法利用初等及组合方法。结果证明了所给方程有无穷多个正整数解,并给出了该方程所有解数的渐近公式。结论该方程的所有解为1,所有无平方因子数以及2乘所有无平方因子数。     

Molecular structure of r(GCG)d(TATACGC): a DNA--RNA hybrid helix joined to double helical DNA

The molecule r(GCG)d(TATACGC) is self-complementary and forms two DNA--RNA hybrid segments surrounding a central region of double helical DNA; its molecular structure has been solved by X-ray analysis. All three parts of the molecule adopt a conformation which is close to that seen in the 11-fold RNA double helix. The conformation of the ribonucleotides is partly determined by water molecules bridging between the ribose O2' hydroxyl group and cytosine O2. The hybrid-DNA duplex junction contains no structural discontinuities. However, the central DNA TATA sequence has some structural irregularities.     

4-氯-萘酰亚胺-丁基高亚精胺与DNA作用的光谱学研究

在人体的生理条件下(p H=7.4),采用紫外光谱法、荧光光谱法研究了4-氯-萘酰亚胺-丁基高亚精胺(1)与鲱鱼精DNA的作用.研究发现化合物1能够嵌入DNA.紫外光谱研究表明化合物(1)能引起DNA构象改变,且化合物1为DNA嵌入剂.采用变温荧光光谱法研究发现荧光淬灭机制为静态淬灭.根据荧光数据计算出不同温度下的结合常数和热力学参数,发现化合物与DNA作用力类型主要是氢键和范德华引力,且作用过程为氢键和范德华引力驱动过程.     

(n,d)-phantom与(n,d)-Ext-phantom态射

设n,d是非负整数且n≥1,引入了(n,d)-phantom态射与(n,d)-Ext-phantom态射的概念,研究了它们的一些性质。作为应用,得到了模的FPn-平坦维数与FPn-内射维数的一些新刻画。     

共面不对称几何条件下Xe 4d(e,2e)反应的理论研究

采用标准的扭曲波玻恩近似理论和修正后的扭曲波玻恩近似理论,计算了共面不对称几何条件下Xe 4d轨道(e,2e)反应的三重微分截面.散射电子能量为1 000 eV,敲出电子能量为100 eV,散射电子角度分别固定在2°和8°.理论计算与Avaldi等人的实验结果和理论计算进行了比较,发现两出射电子之间的后碰撞相互作用很弱,考虑极化效应会造成理论计算与实验结果产生很大差别,同时,散射电子和束缚电子之间的交换作用在反应过程中起着重要作用.     

关于d（n）的一个均值

利用解析的方法研究了除数函数d（n）在square—free数中的均值问题，并得到了关于这个函数的一个完美的渐近公式。     

Meso-四(4-N-乙基吡啶基)卟啉与DNA的相互作用研究

正电性卟啉化合物及其衍生物是核酸结构研究和核酸动力学研究的非常有用的探针.作为一种新的DNA键合试剂,在医药方面被应用于光动力学治疗癌症和抑制病毒等[1,2].卟啉化合物与核酸相互作用的研究已引起广泛的关注,其中报道较多的是meso-四(4-N-甲基吡啶基)卟啉(TMPyP)及其衍生物.     

T(d,n)~4He反应的中子能谱的测量和模拟计算

本文描述用飞行时间谱仪对T(d,n)~4He反应的α关联中子能谱和角分布的测量,以及介绍对这些中子能谱的蒙特卡罗模拟。在计算中考虑了氘在氚-钛靶的多次散射。对发射中子谱自寺和关联中子平均能量的计算结果分别与Pavlik等人的计算结果和我们的实验结果很好地符合。     

(n,d)-内射模与Morita对偶

证明了在Morita对偶之下,自反模是(n,d)-内射的((n,d)-投射的)当且仅当它的Morita偶是(n,d)-投射的((n,d)-内射的),以及右(n,d)-环与左余(n,d)-环,(弱)n-遗传模与(弱)n-余遗传模都是互为对偶的.特别地,自反模是内射的(余遗传的)当且仅当它的偶是(0,0)-投射的(0-遗传的).     

Ca_9Fe(PO_4)_6(OH)_2的电子结构与形成能的第一性原理计算

基于第一性原理和热力学统计原理计算了单个Fe~(2+)替代羟基磷灰石晶胞中Ca~(2+)后晶体(Ca_9Fe(PO_4)_6(OH)_2)的电子结构和能够说明替代后结构稳定性的替位缺陷形成能.电子结构计算得出(Ca_9Fe(PO4)_6(OH)_2)的带隙值是1.85eV,而没有掺杂的是4.93e V,两者态密度特征相似,只是前者峰值变小了.理论形成能和溶液环境中的形成能的计算结果都表明Ca(B)更易被取代,但是两种形成能的值都大于0eV,具体是理论缺陷形成能的值都在7e V到8e V之间,溶液环境中的缺陷形成能主要和替代的位置、溶液的pH值以及Fe~(2+)在溶液中的浓度有关,且其值大于0eV,说明它们需要吸热才能发生替代,所以在羟基磷灰石中Fe~(2+)替代Ca~(2+)不容易发生.     

关于图的(d,1)-全标号

给出了星图、树图和均衡完全三部图的(d,1)-全数。