Raman spectroscopic studies on the conformational changes of calf thymus DNA induced by Cd2+ ions

We used Raman spectroscopy to study the conformational changes of DNA induced by Cd2+ ions in different Cd2+ concentrations solution. The experimental results show that when the Cd2+/PO-2 ratio R increased from 0 to 3.0, the band 835.0 cm-1 shifted about 8 cm-1, and the overlapping spectra of 1446.0and 1461.0 cm-1 separated and moved to 1441.0 and 1458.0 cm-1, respectively. This indicates that the conformation of DNA has changed from a "normal" B-form to a "modified" B'-form. At the same time,changes of other bands demonstrate that parts of base stacking collapse and some hydrogen bonds between AT are disrupted, AT base pairs are damaged more larger than GC base pairs.     

Zn^2＋对DNA稳定性影响的喇曼光谱研究

利用喇曼光谱技术研究了不同摩尔浓度的Zn2+对DNA结构稳定性的影响.结果表明,当Zn2+/PO2- ≤2.0时,Zn2+与DNA磷酸基团上的氧原子结合,形成-PO2-…Zn2+…N7(G)螯合物,这种螯合作用增强了GC 碱基对之间的氢键能量,使得GC碱基对更加稳定;此外,在低浓度情况下,Zn2+还会与腺嘌呤A上的N3结合, 而与A上N3的结合只对AT碱基对有轻微的扰动.当Zn2+/PO2->2.0时,大量的Zn2+开始与胞嘧啶C上的 N3-O2螯合以及与DNA中A上的N1结合,Zn2+与C上的N3-O2的螯合,打断了GC碱基对之间的氢键;与A 上的N1结合时,AT碱基对之间的氢键也被打断.因此,低浓度的Zn2+对DNA的构像起着稳定性作用,但是高浓 度的Zn2+则破坏了DNA构象的稳定性.在高浓度的Zn2+ DNA溶液中,GC受损比AT更为严重,部分C甚至经 过脱氨基现象转化成了T,碱基配对被解开,DNA结构变得不稳定,其主链的几何形状和次级结构发生变化,不 再是一个典型的B型DNA,而是一个修饰过的B′型DNA.     

ICP-AES法研究六钛酸钾晶须对Cu(Ⅱ),Pb(Ⅱ),Cd(Ⅱ)的吸附性能

以电感耦合等离子体原子发射光谱法(ICP-AES)为检测手段,研究了新型吸附剂六钛酸钾晶须对环境样品中Cu(Ⅱ),Pb(Ⅱ),CA(Ⅱ)的分离/富集行为以及解脱的主要因素,并考察了共存离子的干扰影响.在pH值为5.0,振荡时间为5 min,静置时间为30 min时,吸附率可达到95%以上.以3 mol·L-1HNO3作为解脱剂,沸水浴加热40 min,振荡5 win.静置40 win,可将吸附在六钛酸钾晶须上的Cu(Ⅱ),Pb(Ⅱ),Cd(Ⅱ)定量洗脱.测定Cu(Ⅱ),Pb(Ⅱ),Cd(Ⅱ)的检出险分别为0.007 1,0.006 8,0.007 1 μg·mL-1,相对标准偏差(RSD)为0.63%,0.61%,0.50%.在优化的实验条件下,将其用于菊花和琵琶叶中Cu(Ⅱ),Pb(Ⅱ),Cd(Ⅱ)含量的测定,加标回收率在900A～102.9%之间.     

High-pressure Raman and infrared spectroscopic studies of ZrP2O7

High-pressure Raman and mid-infrared spectroscopic studies were carried out on ZrP₂O₇ to 23.2 and 13 GPa respectively. In the pressure range 0.7–4.3 GPa the lattice mode at 248 cm^?1 disappears, new modes appear around 380 and 1111 cm^?1 and the strong symmetric stretching mode at 476 cm^?1 softens, possibly indicating a subtle phase transition. Above 8 GPa all the modes broaden, and all of the Raman modes disappear beyond 18 GPa. On decompression from the highest pressure, 23.2, to 0 GPa all of the modes reappear but with larger full width at half maximum. Lattice dynamics of the high temperature phase of ZrP₂O₇ were studied using first principles method and compared with experimental values.     

Methylene blue as a DNA probe for a comparative study of Cd, Pb and Cr ions binding to calf thymus DNA

Methylene blue (MB) was developed as a sensitive DNA probe for a comparative study of Cd²⁺, Pb²⁺ and Cr³⁺ ions binding with calf thymus DNA (ctDNA). The fluorescence intensity of the MB-ctDNA system increased dramatically when heavy metal ions (Cd²⁺, Pb²⁺ and Cr³⁺ ions) were added, which indicated that some of the bound MB molecules were released from the ctDNA base pairs. To compare the binding affinity of these three different heavy metal ions with ctDNA, the relationships between the fluorescence intensity of the MB-ctDNA-M (Metal ions) system and the concentration ratio of [M]/[DNA(p)] were investigated. The results showed that the order of the binding affinity of heavy metal ions with ctDNA had the following sequence: Cr³⁺> Cd²⁺>Pb²⁺. This order was further proved by the effects of heavy metal ions on the number of MB bound to ctDNA, the measurements of binding constants of these heavy metal ions to ctDNA, and the effects of heavy metal ions on the absorption of the MB-ctDNA system. In addition, the interaction mechanisms of Cd²⁺, Pb²⁺ and Cr³⁺ ions with ctDNA were also discussed in detail. These results indicated that their interaction mechanisms are related to the concentration ratios of heavy metal ions to DNA.     

Dependence of surface-enhanced Raman scattering from Calf thymus DNA on anions

Dependence of surface-enhanced Raman scattering (SERS) from Calf thymus DNA on anions is investigated.With the silver colloid,the bands at 732,960 and 1333 cm-1 for adenine (A),1466 cm-1 for deoxyribose,and 1652 cm-1 for the C=O group of thymine (T) are observably enhanced.With the presence of the Cl- or SO42- anions,the bands at 732 and 1326/1329 cm-1 for the symmetric stretching and skeletal vibrational modes of adenine (A) are dramatically enhanced,and the enhancement effect with the SO24- ion is more than that with the Cl- ion.The experimental results show that the DNA molecule can be adsorbed on the silver colloid particles through the C6N and N7 of adenine (A),the C=O of thymine (T) and deoxyribose.Moreover,the formed hydrogen bonding of the Cl- or S2O4- ions to the C6NH2 group of adenine (A) can induce larger C6N electronegativity,which is favor for the C6N/N7 cooperative adsorption on the (Ag) n colloid particles.     

Raman spectroscopic study of the phase transitions induced by hydrostatic pressure in a Rb2KScF6 crystal

The Raman spectra of Rb₂KScF₆ elpasolite crystals are studied in the pressure range up to 7 GPa. A phase transition is revealed at a pressure of approximately 1 GPa. Analysis of the changes in the spectral parameters shows that the phase transition is accompanied by a doubling of the volume of the primitive cell in the initial cubic phase. Judging from the character of the variations in the pressure dependences of the frequency of the observed vibrations, there can exist another transition to the phase with a lower symmetry at a pressure of approximately 2.1 GPa.     

Kcl：Pb^2＋和RbCl：Pb^2＋单晶中HD色心的喇曼研究

本文报道KCl:Pb~(2+)和RbCl:Pb~(2+)单晶在温度77K经大剂量X射线辐照后的喇曼测量结果。根据高精度的偏振喇曼数据和最近发展起来的所谓表现型分析方法,确认频移为284cm~(-1)和270cm~(-1)的信号分别为KCl:Pb~(2+)和RbCl:Pb(2+)单晶中H_D色心的C_(1h)(010):A′动力学模振动引起的非弹性散射。     

Rapid synthesis and Raman spectroscopic study of the negative thermal expansion material of A (WO4)2 (A = Zr2+, Hf2+)

The crystal structure of ZrW₂O₈ and HfW₂O₈ displays unusual property of isotropic negative thermal expansion in a wide temperature range, which brings about a number of important potential applications. In this work, densely packed A (WO₄)₂ (A = Zr²⁺, Hf²⁺) are rapid synthesized by CO₂ laser. The result of XRD and Raman spectra show that the ZrW₂O₈ is γ phase with space group P2₁2₁2₁ and HfW₂O₈ is α phase with space group P2₁3. Due to the influence of compressive stress, laser rapid solidification technique is more suitable for industrial production of HfW₂O₈.     

MD studies on conformational behavior of a DNA photolyase enzyme

In this work, molecular dynamics (MD) simulations were performed on a DNA photolyase protein with two cofactors, FAD (flavin adenine dinucleotide) and MTHF (methenyltetrahydrofolate), inside the enzyme pocket. A DNA photolyase is a highly efficient light-driven enzyme that repairs the UV-induced cyclobutane-pyrimidine dimer in damaged DNA. We were aimed to compare the conformational changes of the FAD cofactor and other constituent fragments of the molecular system under consideration. The conformational behavior of the FAD molecule is very important for understanding the functional and structural properties of the DNA repair protein photolyase. The photoactive FAD is an essential cofactor both for specificial binding to damaged DNA and for catalysis. The second chromophore (MTHF or 8-HDF) is not necessary for catalysis and has no effect on specific enzyme—substrate binding. The obtained results were discussed to gain insight into the light-driven mechanism of DNA repair by a DNA photolyase enzyme—based on the enzyme structure, the FAD mobility, and conformation shape.     

Cr~(3+)离子在Na_2MgAlF_7中的发光

实验考查了Cr~(3+)离子在Na_2MgAlF_7多晶粉末中的发光特性。~4T_2能级的发光复盖近红外的700nm至1050nm的宽阔谱域。77K时,荧光寿命为310μs,荧光衰减曲线稍偏离单指数式。在200K以上发生较严重的温度猝灭。荧光谱表现出一些结构,对此做了讨论。     

The influence of divalent metal ions on low pH induced LacDNA structural changes as probed with UV resonance Raman spectroscopy

UV (275 nm) resonance Raman spectra of LacDNA 22‐mer duplex [d(TAATGTGAGTTAGCTCACTCAT) · d(ATGAGTGAGCTAACTCACATTA)], which contain protein binding sites within the E. coli lac promoter, were measured at two pH values (6.4 and 3.45) in the absence and presence of Mn²⁺ and Ca²⁺ metal ions, respectively. Also, the UV (275 nm) resonance Raman markers of the corresponding oligonucleotide d(TAATGTGAGTTAGCTCACTCAT) and of its complementary anti‐sense strand d(ATGAGTGAGCTAACTCACATTA) were established and tentatively assigned. Large changes in the UV (275 nm) resonance Raman spectra of LacDNA duplex were observed at pH 3.45 as compared with the corresponding spectrum at pH 6.4, in the absence of divalent metal ions and at low concentrations of Ca²⁺ ions, respectively. Major changes comprise: adenine protonation, GC base pair protonation, DNA bases unstacking and changes in the hydrogen bonding strength between the strands of different LacDNA complexes, respectively. Divalent metal ions (Mn²⁺ and Ca²⁺) were found to inhibit LacDNA protonation even at low concentrations. Manganese(II) ions are much more effective in this regard, as compared with calcium(II) ions. Binding of Mn²⁺ ions to N7 of guanine and, possibly, in a lesser extent to adenine was observed as judging from the difference Raman bands at 1315, 1354 and 1493 cm⁻¹. Copyright © 2013 John Wiley & Sons, Ltd.     

Irradiation hardening behaviors of tungsten-potassium alloy studied by accelerated 3-MeV W~(2+) ions

Tungsten-potassium(WK)alloy with ultrafine/fine grains and nano-K bubbles is fabricated through spark plasma sintering(SPS)and rolling process.In this study,3-MeV W^2+ ion irradiation with a tandem accelerator is adopted to simulate the displacement damage caused by neutrons.As the depth of irradiation damage layer is limited to only 500 nm,the hardening behaviors of WK alloy and ITER(International Thermonuclear Experimental Reactor)-W under several damage levels are investigated through Bercovich tip nanoindentation test and other morphological characterizations.The indenter size effect(ISE),soft substrate effect(SSE),and damage gradient effect(DGE)are found to influence the measurement of nano-hardness.Few or no pop-ins in irradiated samples are observed while visible pop-in events take place in unirradiated metals.Extensive pile-up with different morphology features around the indentation exists in both WK and ITER-W.The WK shows a smaller hardness increment than ITER-W under the same condition of displacement damage.This study provides beneficial information for WK alloy serving as a promising plasma facing materials(PFMs)candidate.     

Temperature-dependent Raman spectroscopic study of ferroelastic K_2Sr(MoO_4)

Raman scattering measurements of K_2 Sr(MoO_4)2 were performed in the temperature range of 25–750?C. The Raman spectrum of the low-temperature phase α-K_2 Sr(MoO_4)2 that was obtained by first-principle calculations indicated that the Raman bands in the wavenumber region of 250–500 cm-1 are related to Mo–O bending vibrations in MoO4 tetrahedra,while the Raman bands in the wavenumber region of 650–950 cm-1 are attributed to stretching vibrations of Mo–O bonds.The temperature-dependent Raman spectra reveal that K_2 Sr(MoO_4)2 exhibits two sets of modifications in the Raman spectra at ～ 150?C and ～ 475?C, attributed to structural phase transitions. The large change of the Raman spectra in the temperature range of 150?C to 475?C suggests structural instability of the medium-temperature phase β-K_2 Sr(MoO_4)2.     

双离子(40Ar+,C2H6+)辐照合成金刚石纳米晶颗粒

用双离子(40Ar+,C1H6+)辐照实验完成了从多壁碳纳米管向金刚石纳米晶颗粒的转变.对转变机理进行了初步探讨.这一探索有望能成为一种金刚石纳米晶合成的新途径.由此可知,多重荷能离子辐照用于其他材料纳米结构的制备也不是凭空设想.     

Monitoring of spectroscopic changes of a single trapped fission yeast cell by using a Raman tweezers set-up

We demonstrate an improvement of the sensitivity of a Raman tweezers set-up, which combines optical tweezers with Raman spectroscopy. The system was tested by taking the Raman spectrum of a 4.6 μm diameter polystyrene sphere trapped in an aqueous solution. The improvement of sensitivity of the set-up was achieved by adjusting the trap depth for maximum signal to noise ratio (SNR). The maximum SNR was obtained by investigating the Raman peak of a trapped polystyrene sphere at 1001 cm⁻¹ according to trap depth. With this system, a single trapped living Schizosaccharomyces Pombe yeast cell was sensitively monitored by taking the kinetic Raman spectra for more than 2 h. The relative intensity decrease in amide I and amide III bands, frequency increase in amide I band together with alterations in tyrosine marker band around 850 cm⁻¹ was observed, which indicates alterations in the hydration state of protein by time progressing.     

Raman spectra and XPS studies of phase changes in Ge2Sb2Te5 films

Ge_2Sb_2Te_5 film was deposited by RF magnetron sputtering on Si (100) substrate. The structure of amorphous and crystalline Ge_2Sb_2Te_5 thin films was investigated using XRD, Raman spectra and XPS. XRD measurements revealed the existence of two different crystalline phases, which has a FCC structure and a hexagonal structure, respectively. The broad peak in the Raman spectra of amorphous Ge_2Sb_2Te_5 film is due to the amorphous －Te－-Te－ stretching. As the annealing temperature increases, the broad peak separates into two peaks, which indicates that the heteropolar bond in GeTe_4 and the Sb－Sb bond are connected with four Te atoms, and other units such as (TeSb) Sb－Sb (Te_2) and (Sb_2) Sb－Sb (Te_2), where some of the four Te atoms in the above formula are replaced by Sb atoms, remain in crystalline Ge_2Sb_2Te_5 thin film. And from the results of Raman spectra and XPS, higher the annealing temperature, more Te atoms bond to Ge atoms and more Sb atoms substitute Te in (Te_2) Sb－Sb (Te_2).     

MgF2：V^2＋晶体能级和振动结构的DV—Xa研究

首次用DV-X_a方法计算了终端声子激光晶体MgF_2:V~(2+)的电子能级和振动结构,给出的晶场能级与实验值相当接近.使用晶格振动的“呼吸”模型,得到了基态~4B_(1g)和第一激发态~4B_(2g)的振动势能曲线.在简谐振动近似下,它们分别具有454cm~(-1)和460cm~(-1)的声子能量,与实验值399cm~(-1)符合很好.另外,还获得晶体振动的黄昆参数,激活能,和Franck—Condon交距等参数.计算了四种温度(0K,2K,77K和300K)下的振动线形,并与2K的实验吸收谱作了比较.     

含铒碲酸盐玻璃的上转换荧光性质研究

在室温下,用804nm波长的半导体激光器作激发源,在TeO_2-PbO基掺铒碲酸盐玻璃中实现了中心波长分别为525nm,550nm和660nm的上转换发射.荧光强度与激发功率呈非线性关系.估测了PbO含量对上转换荧光相对强度的影响.