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.     

Raman spectroscopic study of calf thymus DNA: an effect of proton‐ and γ‐irradiation

Raman spectroscopy was applied to analyse structural changes in calf thymus double‐stranded deoxyribonucleic acid (dsDNA) after proton‐ and γ‐irradiation (0.5, 5 and 50 Gy). Characteristic Raman bands of phosphodiester linkages, nucleic bases and deoxyribose moieties were sensitive to irradiation. A significant damage of the macromolecules was observed only at the highest dose (50 Gy) of both types of radiations. Spectral changes confirmed a radiation‐induced alteration of the native structure of dsDNA. Nucleic bases, especially pyrimidines, were the most sensitive to radiation, while some alterations in the sugar–phosphate backbone were also detected. The differences in the dose‐dependent effects of proton vs γ‐irradiation on studied biomolecule are discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

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.     

ATR-FTIR spectroscopic studies on density changes of fused silica induced by localized CO2 laser treatment

The surface density changes of the central region of the sites treated by using the CO_2 laser-based non-evaporative damage mitigation for fused silica are investigated by attenuated total reflectance-Fourier transform infrared spectroscopy(ATR-FTIR).The ATR-FTIR peak shifts of the treated sites of fused silica are monitored to determine the changes of the corresponding density.For the quenching treated sites,the surface density is increased by(0.24±0.01)%compared with the initial density but the laser annealing by the exposure of a power ramp down after damage mitigation effectively suppresses the structural changes of treated sites,which could reduce the increase of the corresponding density to(0.08±0.01)%.The results provide sufficient evidence that the laser annealing by a power ramp down after damage mitigation has a positive effect on the control of the structural change induced by CO_2 laser-based damage mitigation.     

Raman spectroscopic studies of pulsed laser‐induced defect evolution in graphene

Raman spectra were obtained for graphene after irradiating the samples by pulsed laser (λ = 248 nm). Changes in the spectra were observed as the pulse laser energy density (PLED) was varied from 0.1 to 0.25 J/cm². Changes in bilayer graphene were accompanied by the appearance of the D peak and the broadening of the G peak. Changes in multilayer graphene are more profound as the Raman spectra changes from a multilayer to bilayer and subsequently to monolayer graphene in response to a slow increase in the PLED. The threshold PLED was found to be dependent on the number of graphene layers. We also irradiate graphene with very high PLED (much above the threshold), and the Raman spectra were found to be significantly changed. The G‐band became broader, and red shifted, while the intensity of the 2D‐band was drastically reduced and an intense defect‐related D peak appeared at about 1350 cm⁻¹. The laser ablation of graphene, both with low‐ and high‐energy intensity, is consistent with the reported theoretical predictions. Copyright © 2013 John Wiley & Sons, Ltd.     

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.     

Phase transitions of Decylammonium chloride by Raman and infrared spectroscopic studies

Raman scattering and infrared absorption were used to study phase transition between a non intercalated structure and an intercalated one in Decylammonium chloride C₁₀H₂₁NH₃Cl, in the temperature range from 79 to 370 K and to determine the transition temperature. The melting of the chains seems to be the cause of the transition. Unusual splitting of some vibration modes help us to characterize the intercalated structure. The entering of air into the structure seems to be at the origin of the discrepancy that appears in the experimental results.     

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.     

Monitoring by Raman spectroscopy of the damage induced in the wake of energetic ions

This article reports micro‐Raman experiments performed on cross sections of 6H‐SiC crystals irradiated with heavy ions of different energies. The results demonstrate that this technique is very powerful to quantify the damage created in the wake of energetic ions from the surface of samples down to the ion resting position. For slow ions (900‐keV I), ballistic collisions lead to the amorphization of the surface region of samples. For swift ions (36‐MeV W), the surface region remains crystalline and amorphization occurs around the end of the ion path. Moreover, synergistic effects between electronic and nuclear slowing down processes are put forward. The methodology used in this work may be adapted to other materials where radiation effects need to be investigated, provided that the damage created by irradiation is detectable by Raman spectroscopy. Copyright © 2014 John Wiley & Sons, Ltd.     

Raman and surface‐enhanced Raman spectroscopic studies of the 15‐mer DNA thrombin‐binding aptamer

Aptamers are single‐stranded oligonucleotides that selectively bind to their target molecules owing to their ability to form secondary structures and shapes. The 15‐mer (5′‐GGTTGGTGTGGTTGG‐3′) DNA thrombin‐binding aptamer (TBA) binds to thrombin following the formation of a quadruplex structure via the Hoogsten‐type G–G interactions. In the present study, Raman and SERS spectra of TBA and thiolated TBA (used to facilitate covalent bonding to metal nanoparticle) in different conditions are investigated. The spectra of the two analogs exhibit vibrations, such as the C8N7 H2 deformation band at ∼1480 cm⁻¹ of the guanine tetrad, that are characteristic of the quadruplex structure in the presence of K⁺ ions or at low temperature. Interestingly, SERS spectra of the two analogs differ markedly from their respective normal Raman spectra, possibly due to changes in the conformation of the aptamer upon binding, as well as to the specific interaction of individual vibrational modes with the metal surface. In addition, the SERS spectra of the thiolated aptamer show significant changes with different concentrations, which may be due to different orientation of the molecule with respect to the metal surface. This study provides useful information for the development of label‐free aptamer‐based SERS sensors and assays. Copyright © 2009 John Wiley & Sons, Ltd.     

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.     

Ion beam induced luminescence studies of LiAlO2 using negative ions

Lithium aluminate (LiAlO₂) is the candidate material for solid tritium breeder applied in the developing fusion reactors. The research of its defect behavior under ion irradiation was proceeded in the negative ions induced luminescence setup of the GIC4117 Tandem accelerator in Beijing Normal University. The ion beam induced luminescence (IBIL) measurement was performed by 20 keV H⁻ ions at room temperature. The luminescence spectra showed seven emission bands: the 4.55 eV may due to a self-trapped exciton (STE), the 4.06 eV and the 1.72 eV may due to impurity or intrinsic defect, the 3.54 eV due to F center, the 3.20 eV due to F⁺ center, the 2.93 eV due to F₂ center, the 2.30 eV due to F-center aggregates (F_n center), respectively. The intensity evolutions of each band with fluence were presented and the corresponding mechanisms were discussed.     

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。     

Raman spectroscopic study of the uranyl tellurite mineral moctezumite PbUO2(TeO3)2

The uranyl tellurite mineral moctezumite, Pb(UO₂)(TeO₃)₂, was studied by Raman spectroscopy and complemented with infrared spectroscopy. The presence of the stretching and bending vibrations of uranyl (UO₂)²⁺ and tellurite (TeO₃)²⁻ ions was inferred, and the observed bands were assigned to uranyl and tellurite units vibrations. U O bond lengths calculated from the spectra with two empirical relations are close to those inferred from the X‐ray single‐crystal structure of moctezumite. Copyright © 2008 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.