Imidazoline biradical spin labels with EPR spectral sensitivity to the local concentration of protons

EPR spectral sensitivity of the three biradicals of imidazoline and imidazolidine types to the local concentration of protons (pH) in aqueous solutions has been studied. Significant increase ing-factor (Δg ≈ 0.0002) and decrease in hyperfine interaction constant (Δa_N = 0.8?1.2 G) upon the protonation of atom N-3 of the radical heterocycle were observed. The pH dependence of a_N andg- factor is described by conventional titration curve with one or two pK values. The latter case was explained by nonindependent protonation of two monoradical fragments closely located in the biradical structure. EPR spectra of protonated and deprotonated forms of the biradicals have significantly different intensities of “biradical” components, I_b, reflecting changes in spin exchange interaction. It has been found that activation energy of spin exchange, E_a, estimated from temperature dependence of I_b in glycerol/water solution is lower for the biradical conformation with larger I_b. This is in agreement with main contribution of direct collisions of monoradical fragments in spin exchange interaction so larger value of I_b corresponds to the conformation with less spatial restrictions for the motion of monoradical fragments (lower E_a). The potential use of the pH-sensitive biradicals as spin labels is discussed.     

Quantum Secure Direct Communication and Quantum Sealed-Bid Auction with EPR Pairs

I present a new protocol for three-party quantum secure direct communication (QSDC) with a set of ordered M Einstein-Podolsky-Rosen (EPR) pairs. In the scheme, by performing two unitary operations and Bell state measurements, it is shown that the three legitimate parties can exchange their respectivesecret message simultaneously. Then I modify it for an experimentally feasible and secure quantum sealed-bid auction (QSBD) protocol. Furthermore, I also analyze the security of the protocol, and the scheme is proven to be secure against the intercept-and-resend attack, the disturbance attack and the entangled-and-measure attack.     

Quantum Secure Direct Communication and Quantum Sealed-Bid Auction with EPR Pairs

I present a new protocol for three-party quantum secure direct communication （QSDC） with a set of ordered M Einstein-Podolsky-Rosen （EPR） pairs. In the scheme, by performing two unitary operations and Bell state measurements, it is shown that the three legitimate parties can exchange their respective secret message simultaneously. Then I modify it for an experimentally feasible and secure quantum sealed-bid auction （QSBD） protocol. Furthermore, I also analyze th~ecurity of the protocol, and the scheme is proven to be secure against the intercept-and-resend attack, the disturbancb attack and the entangled-and-measure attack.     

Attacks and Improvement of Quantum Sealed-Bid Auction with EPR Pairs

Recently, an experimentally feasible three-party quantum sealed-bid auction protocol based on EPR pairs [Z.Y. Wang, Commun. Theor. Phys. 54 （2010） 997] was proposed. However, this study points out Wang＇s protocol cannot resist some internal bidders＇ attacks, such as the Twiee-CNOT attack, the collusion attack. A malicious bidder can launch the Twice-CNOT attack to obtain the other＇s bid, or the dishonest auctioneer may collude with one bidder and help him/her win the action by changing his/her bid. For preventing against these attacks, a simple solution by using the QKD-based message encryption and a post-confirmation mechanism by adopting the hash function are proposed.     

Scaled Quantum Chemical Studies of the Molecular Structure and Vibrational Spectra of Minoxidil

The Fourier transform Raman and Fourier transform infrared spectra for minoxidil have been recorded in the region 4000—100 cm^?1 and 4000—450 cm^?1, respectively. The structural and spectroscopy data of the molecule in the ground state were calculated by using density functional theory methods with 6-311G (d, p) basis set. A detailed vibrational analysis of the title compound has been done using normal coordinate analysis following the scaled quantum mechanical force field methodology. The calculated molecular geometry parameters and scaled vibrational wavenumbers are well compared with the experimental data. The electronic properties, such as excitation energies, absorption wavelength, highest occupied molecular orbital (HOMO), and lowest unoccupied molecular orbital (LUMO) energies were performed by time-dependent density functional theory approach, and the results are in good agreement with experimental absorption spectrum. The charge delocalizations of these molecules have been analyzed using natural bond orbital analysis. The molecule orbital contributions are studied by density of energy states. Fukui functions, local softness, and electrophilicity indices for selected atomic sites of the title compound are determined. Finally, the thermal behaviors of the compound have been calculated by different temperature.     

尿素分子红外光谱与晶体红外吸收截止波长的量子化学研究

应用量子化学从头算方法准确计算了尿素分子的红外光谱,得到分子的振动频率和红外振动强度与实验值相符。在分子红外光谱计算的结果基础上估算了尿素晶体的红外吸收截止波长,其值为１．４０μｍ,与测量的符合得很好。对光学晶体红外透过窗口的研究具有重要意义。     

氯铝酸离子液体酸性的红外光谱探针和量子化学研究

文章采用吡啶探针红外光谱、吡啶递增吸附实验研究和量子化学理论计算相结合的方法深入研究了氯铝酸离子液体的酸性及氯铝酸离子液体Lewis酸位Al₂Cl-₇与吡啶吸附之间的相互作用机理。通过实验和理论计算研究发现,Al₂Cl-₇,AlCl-₄阴离子具有吸电性,能够吸引吡啶环上的孤对电子产生吸附作用,具有Lewis酸性,它们分别呈现吡啶探针红外光谱Lewis酸特征峰;通过红外光谱特征峰峰位、键长及电荷分布分析表明Al₂Cl-₇的酸性强于AlCl-₄;氯铝酸离子液体Lewis酸位Al₂Cl-₇与吡啶吸附的机理为：当吡啶含量小时,仅存在Py-Al₂Cl-₇吸附;当吡啶量增加到一定程度时,Py-Al₂Cl-₇配位络合物中的AlCl-₄容易与吡啶发生吸附解离为Py-AlCl-₄配位络合物和Py-AlCl₃配位络合物,导致离子液体吡啶递增吸附红外特征峰发生变化。     

New Quantum Key Distribution Scheme Based on Random Hybrid Quantum Channel with EPR Pairs and GHZ States

A theoretical quantum key distribution scheme based on random hybrid quantum channel with EPR pairs and GHZ states is devised. In this scheme, EPR pairs and tripartite GHZ states are exploited to set up random hybrid quantum channel. Only one photon in each entangled state is necessary to run forth and back in the channel. The security of the quantum key distribution scheme is guaranteed by more than one round of eavesdropping check procedures. It is of high capacity since one particle could carry more than two bits of information via quantum dense coding.     

EPR studies of15N- and2H-substituted pH-sensitive spin probes of imidazoline and imidazolidine types

The isotopically substituted analogs of pH-sensitive imidazoline and imidazolidine radicals have been synthesized and investigated with electron paramagnetic resonance (EPR) spectroscopy. The introduction of²H and¹⁵N into the structure of the radical is a useful approach to enhance the information obtained from spin-labeling experiments. The spectra of the radicals have been analyzed with 9.8 (X-band) and 130 GHz (D-band) EPR spectroscopy. The substitution of¹H for²H leads to significant narrowing of Gaussian line width, while the substitution of¹⁴N for¹⁵N in the nitroxyl fragment decreases both the number of spectral lines and Lorentzian line width. These effects result in a significant increase in the peak intensities up to 5–7 times for X-band EPR spectra of one of the imidazoline radicals (R4). The increase in spectral resolution allowed us to reveal the hyperfine interaction splitting with the attached proton (0.36 G) in the protonated form of the radical R4. The influence of proton exchange of the radicals with phosphate and acetate buffers on their EPR spectra has been studied in H₂O and D₂O. The corresponding rate constants of the proton exchange have been calculated from fitting of the simulated EPR spectra line shapes to experimental spectra. The data obtained demonstrated the advantages of the isotopically substituted spin pH probes in spectral resolution and sensitivity which can be an important factor particularly for applications in vivo where the fundamental sensitivity is much lower. The sensitivity of EPR spectra of these spin probes to the buffer capacity could be of practical importance taking into account the biological relevance of monitoring this parameter in some pathological states.     

基于EPR方法的天然产物抗氧化性能研究(英文)

自旋捕捉EPR、用于动物模型的低温EPR以及自旋标记EPR等多种EPR方法已经用于天然产物的抗氧化活性研究中.虽然对于抗氧化剂而言其必备条件之一就是具有体外清除自由基的能力,但是外源性抗氧化剂在生物体内抗氧化剂抗氧化能力评价的方法更有实际意义.通过对超过200种中药和一些传统中药处方的研究,已经建立并详细描述了用于评价天然产物抗氧化能力的EPR筛选方法.通过EPR方法可以获得天然产物在分子水平、细胞水平以及组织水平抗氧化能力的比较全面的评价.     

用PM3量化参数预测多氯代二苯并呋喃的logKow

从现有的PCDFs分子的正辛醇 /水分配系数 (logKow)实验数据出发 ,建立定量结构 性质关系方程(QSPR) .采用G98W程序包中的PM3方法对 13 5个多氯代二苯并呋喃 (PCDFs)分子和二苯并呋喃进行了优化计算 ,作业命令为 #pPM3optfreqscf(conver =9) ,以计算所得的分子轨道能量、碳原子电荷作为PCDFs分子结构描述符 ,运用多元线性回归技术建立了PCDFs的logKow与分子结构描述符的四元方程 ,最优相关系数为 0 .95 0 7,标准偏差为 0 .173 7,经检验该模型的稳健性好 ,并对未有实验数据的 85个PCDFs的logKow进行预测     

Spectrophotometric Studies of the Influence of Organic Solvents and Substituents on Some Schiff Bases

The effect of the substituents, solvent polarities and hydrogen ion concentration on the electronic structure and UV/VIS absorption spectra of some Schiff bases, derivatives of N-(R-benzylidene)benzidine (R = o-NO₂ and o-OH, p-OH) and N-(R-furfurylidene)benzidine (R = H and 5 - NO₂), have been studied. The spectral shifts obtained in various organic solvents were discussed on the basis of the specific solute - solvent interactions through the formation of hydrogen bonds between hydrogen-bond donor (HBD) solvents and the benzidine nitrogen atom of the Schiff bases. Some interpretations of the electronic aspects of this type of hydrogen bonding were discussed as well as the stabilization effects due to the solvation. Finally, the pK values of the compounds were determined.     

芳香基双咪唑配体的合成及量子化学计算

选用邻二氯甲基苯与咪唑为原料,合成[1,2-二（N-咪唑基甲基）苯]芳香基双咪唑配体,通过IR光谱和元素分析对配体进行表征.使用HF/6-31G（d）方法对该配体进行了量子化学计算,运用振动分析获得红外光谱,通过理论计算的IR光谱与实验获得的IR光谱特征峰位置较为吻合,并探讨配体的成键特征、前线分子轨道组成及原子净电荷布居规律,分析活性原子的特征.结果表明,配体的端基N原子具有较高的活性,易于同金属原子配位.     

双(2,2-二硝基丙基)甲缩醛的结构和爆轰性能的量子化学研究

利用B3LYP/6-311+G(2d,p)方法对一种新型含能增塑剂双(2,2-二硝基丙基)甲缩醛进行几何优化,计算了其红外光谱、生成焓和爆轰特性. 分析了最弱键的键离解能和键级并预测了目标化合物的热稳定性. 结果表明双(2,2-二硝基丙基)甲缩醛中的四个N-NO₂键的键离解能都为164.38 kJ/mol. 表明目标化合物是一个热力学性能稳定的化合物. 以凝聚相生成焓和分子密度为基础,采用Kamlet-Jacobs方法预测其爆速和爆压. 目标化合物的晶体结构属于P21空间群.     

Real-time monitoring of drug-induced changes in the stomach acidity of living rats using improved pH-sensitive nitroxides and low-field EPR techniques

New improved pH-sensitive nitroxides were applied for in vivo studies. An increased stability of the probes towards reduction was achieved by the introduction of the bulky ethyl groups in the vicinity of the paramagnetic NO fragment. In addition, the range of pH sensitivity of the approach was extended by the synthesis of probes with two ionizable groups, and, therefore, with two pKa values. Stability towards reduction and spectral characteristics of the three new probes were determined in vitro using 290 MHz radiofrequency (RF)- and X-band electron paramagnetic resonance (EPR), longitudinally detected EPR (LODEPR), and field-cycled dynamic nuclear polarization (FC-DNP) techniques. The newly synthesized probe, 4-[bis(2-hydroxyethyl)amino]-2-pyridine-4-yl-2,5,5-triethyl-2,5-dihydro-1H-imidazol-oxyl, was found to be the most appropriate for the application in the stomach due to both higher stability and convenient pH sensitivity range from pH 1.8 to 6. LODEPR, FC-DNP and proton-electron double resonance imaging (PEDRI) techniques were used to detect the nitroxide localization and acidity in the rat stomach. Improved probe characteristics allowed us to follow in vivo the drug-induced perturbation in the stomach acidity and its normalization afterwards during 1 h or longer period of time. The results show the applicability of the techniques for monitoring drug pharmacology and disease in the living animals.     

Unified Treatment of EPR and Bell Arguments in Algebraic Quantum Field Theory

A conjecture concerning vacuum correlations in axiomatic quantum field theory is proved. It is shown that this result can be applied both in the context of EPR-type experiments and Bell-type experiments.     

EPR and ENDOR Studies of Shallow Donors in SiC

Recent progress in the investigation of the electronic structure of the shallow nitrogen (N) and phosphorus (P) donors in 3C–, 4H– and 6H–SiC is reviewed with focus on the applications of magnetic resonance including electron paramagnetic resonance (EPR) and other pulsed methods such as electron spin echo, pulsed electron nuclear double resonance (ENDOR), electron spin-echo envelope modulation and two-dimensional EPR. EPR and ENDOR studies of the ²⁹Si and ¹³C hyperfine interactions of the shallow N donors and their spin localization in the lattice are discussed. The use of high-frequency EPR in combination with other pulsed magnetic resonance techniques for identification of low-temperature P-related centers in P-doped 3C–, 4H– and 6H–SiC and for determination of the valley–orbit splitting of the shallow N and P donors are presented and discussed.