DT Molecules Research Articles

Rovibrational matrix elements of polarizability of HD, HT and DT molecules

Fresh computations of rovibrational matrix elements of the polarizability α[=( α ||+2 α ⊥)/3] and the polarizability anisotropy γ(= α ||− α ⊥) of the heteronuclear isotopomers, HD, HT, and DT, of the hydrogen molecule are presented. The computations combine the most accurate polarizability functions α( R) and γ( R) ( R being the bond distance) on the one hand and the most accurate adiabatic potential on the other. The calculations are extended to the product operators xα and xγ where x is the centre of mass to centre of charge separation in the heteronuclear species. The latter matrix elements are needed, additionally, for elucidating the absorption intensities of some of the zero-phonon rovibrational transitions peculiar to the heteronuclear species in the crystalline phase.

Dynamic final-state effect on the Au4fcore-level photoemission of dodecanethiolate-passivated Au nanoparticles on graphite substrates

We have carried out a photoemission study using synchrotron radiation of dodecanethiolate- (DT-) passivated Au nanoparticles supported on the highly oriented pyrolytic graphite (HOPG) substrates. From the detailed line-shape analyses, it is found that Au $4f$ core-level photoemission spectra of DT-passivated Au nanoparticles on the HOPG substrates consist of the two components, which originate from the inner Au atoms of Au nanoparticles and surface Au atoms bonded to surface passivants of DT molecules. Furthermore, it is found that Au $4f$ core-level spectra shift to higher binding energy with decreasing the nanoparticle diameter. We attribute these energy shifts to the dynamic final-state effect on the Au $4f$ core-level photoemission due to the positive charge with a finite lifetime left behind in the nanoparticles in the photoemission final state.

Synthesis of long Poly(dA).Poly(dT) DNA without structural defects using enzymatic reaction; tailored ligated Poly(dA).Poly(dT).

Poly(dA).Poly(dT) molecules up to 1000 base pairs (bp) have been synthesized using enzymatic reaction, and characterization by STM observation shows that the DNA has no defects in the duplex structure.

Generalization of the exponential variational ansatz in relative coordinates for bound state calculations in four-body systems

A generalization of the exponential variational expansion in relative coordinates to four-body systems is presented. It is shown that all required matrix elements can be expressed as derivatives upon the nonlinear parameters of the so-called auxiliary or basic four-body (six-dimensional) integral. If such an integral can be computed analytically, then it is possible to use the proposed variational approach for highly accurate variational calculations for various four-body systems with arbitrary particle masses without adiabatic or similar approximations. For instance, this approach can be used for highly accurate, bound state, variational calculations of the positronium molecule Ps2, four-body muonic molecules, H2, D2, and DT molecules and many other systems. In fact, the present work opens a new avenue in the study of four-body systems.

Total and Dissociative Electron-impact Cross Sections for X1Σg+ → B1Σu+ and X1Σg+ → C1Πu Transitions of Vibrationally Excited Tritium and Deuterium-Tritium Molecules

Electron-impact total and dissociative cross sections, calculated by using the impact-parameter method, for the X1Σg+ → B1Σu+ and X1Σg+ → C1Πu transitions of vibrationally excited T2 and DT molecules, are presented. The mass and vibrational energy scalings of these cross sections are discussed.

Rovibrational matrix elements of multipole moments of the HD, HT and DT molecules

Rovibrational matrix elements of the multipole moments Q ℓ of HD, HT and DT for ranks 2 ≤ ℓ ≤ 11 have been computed. Since the present calculations have been performed with the nuclear centre of mass (rather than the geometric centre) as the origin, the computations had to include even as well as odd values of ℓ. The results are used to correlate the absorption intensities of the zero-phonon single transitions in solid HD to theory.

Dissociative electron attachment rates for H2 and its isotopes

Dissociative electron attachment to rovibrationally excited H2, HD, HT, D2, DT, and T2 molecules in their ground electronic states via the ∑u+2 shape resonance is studied within the framework of the nonlocal resonance theory. Rate constants for selected processes are presented in the electron energy range up to 5 eV. Maximum rate of 2.8×10−8 cm3 s−1 is found for attachment to all these molecules.

Investigation of the Parameters of Muon-Catalyzed Fusion in Double D/T Mixture at High Temperature and Density

Experiments on the study of the muon catalyzed fusion (μCF) process in a double D/T mixture of hydrogen isotopes in the temperature range 300–800 K at densities 0.3–0.5 LHD are performed at the JINR phasotron. The values of the effective μCF parameters (cycling rate λ c , neutron yield Y n , muon losses w) are obtained. Tentative dtμ-molecule formation rates on D2 and DT molecules (λ dtμ−d and λ dtμ−t ) are obtained for different mixture temperatures and densities. The results obtained show that λ dtμ−t increases with temperature, but its value is smaller than theoretical predictions.

Probing the energetics of oligo(dT).poly(dA) by laser cross-linking.

Experimentally determined changes in free energy (delta G(o)) for thymine-thymine interactions occurring in oligo(dT).poly(dA) are dependent on the method used for preparation of the double-stranded template. A rapid laser cross-linking technique was used to examine the equilibrium between oligomers of (dT) bound to either poly(dA) or poly(rA). The single-pulse (4-6 nsec) ultraviolet laser excitation of these polynucleotides causes pyrimidine dimer formation between contiguous oligo(dT) molecules, resulting in a "ligation" of the oligomers. Analysis of the resulting data using standard binding isotherms allowed determination of the degree of cooperativity existing between oligomers. Using the cooperativity, delta G(o), delta H(o), and delta S(o) are calculated, thereby providing thermodynamic parameters for this interaction. The measured cooperativity of oligo(dT) molecule interactions allows direct calculation of the number of 3' ends available as nicked structures or the number of 3' ends associated with gaps for oligo(dT).poly(dA) when used as a substrate for DNA synthesis.

A high capacity, reusable oligodeoxythymidine affinity column

A high capacity, reusable oligodeoxythymidine (oligo(dT)) affinity column suitable for purification of polyadenylated mRNA is described. Oligo(dT) molecules, 30 nucleotides in length, were chemically synthesized on an Applied Biosystems DNA synthesizer. Deprotection of the oligo(dT) molecules was achieved by thiophenol/dioxane/triethylamine treatment. Since no hot ammonia treatment was required, the oligo(dT) molecules remained covalently attached to the support matrix. The resulting column has very high oligo(dT) density and can be used directly for purifying polyadenylated mRNA. Column-purified mRNAs were shown to be intact and functional in Northern blot analysis, in vitro translation, and reverse transcription assays.

Different substrate specificities of the two DNA ligases of mammalian cells.

Mammalian cells contain the DNA ligases I and II. These enzymes show different molecular weights and heat labilities, and antibodies against ligase I do not inhibit ligase II. Here, the nonidentical substrate specificities of the enzymes are described. Under standard reaction conditions DNA ligase I, but not ligase II, catalyzes blunt-end joining of DNA, while ligase II is the only activity that joins oligo(dT) molecules hydrogen-bonded to poly(rA). These differences facilitate the distinction between the two enzymes and should permit further analysis of their functions.

Reaction of liquid and solid D2-T2

Collision-induced infrared spectroscopy has been used to measure the initial rate of the chemical exchange of equimolar D2 and T2 in liquid and solid forms from 9 to 23K over 23 to 45 h. If first-order kinetics are assumed, the time constant is 100-140 h for thermal equilibrium and 160-180 h for a hot-atom equilibrium. The latter is favoured, but cannot be confirmed. Approximately three DT molecules are formed per ion pair (using the gas-phase value of 36.6 eV/ion pair). A likely mechanism is reaction of the T2+ to the T3+ ion, followed by exchange. The slowness of the exchange suggests that molecular DT can be isolated and handled for fusion applications.

Detection, sizing, and quantitation of polyadenylated ribonucleic acid in the nanogram-picogram range.

A method is described for using very high specific activity [3H]poly(deoxythymidylate) [[3H]poly(dT)] to detect, size, and quantiate subnanogram amounts of nonradioactive polyadenylated RNA. Short (approximately 100 nucleotides long) [3H]poly(dT) is hybridized to the poly(adenylate) [poly(A)] tracts in polyadenylated RNAs. The RNA may then be sized and quantitated by sucrose gradient analysis. The addition of the small [3H]poly(dT) molecules does not significantly alter the s values of RNAs. The amount of [3H]poly(dT) hybridized to polyadenylated RNA increases linearly with the amount of RNA. A room temperature hydroxylapatite (HA) method has also been developed to detect and quantitate poly(A)-containing RNA after hybridization to radioactive poly(dT). S-1 nuclease (S-1) analysis can also be used to measure the poly(A) content of polyadenylated RNA to less than nanogram RNA amounts. For both the S-1 and HA approaches, the amount of [3H]poly(dT) hybridized increases with the amount of RNA and the methods can detect to as little as 10(-12) g of polyadenylated RNA with [3H]poly(dT). Greater sensitivity is possible with higher specific activity poly(dT). The approaches presented here significantly extend the uses of radioactive homopolymers to detect, quantitate, and characterize RNAs containing complementary homopolymer tracts.

A poly(dT)-stimulated ATPase activity associated with simian virus 40 large T antigen.

Highly purified SV40 large T antigen exhibits an ATPase activity which can be stimulated approximately 7-fold by the DNA homopolymer poly(dT). The poly(dT)-stimulated enzyme can hydrolyze various ribonucleotide and deoxyribonucleotide triphosphates, with ATP and dATP serving as the best substrates. Purified large T antigen hydrolyzes ATP to ADP and Pi, with a maximum specific activity of 13.5 mumol of inorganic phosphate released per h per mg of protein. Of the various natural and synthetic polynucleotides tested, poly(dT) was by far the best activator. Long chain poly(dT) molecules are much more effective activators than are short chain length oligo(dT) molecules. The highly purified large T antigen contains no detectable protein kinase activity.

A new method of assay for polynucleotide ligase

A new method for the assay of polynucleotide ligase is described. It consists of two parallel DNA polymerase reactions with poly(dA) · oligo(dT) as template-primer and d[ 3H] TTP as precursor; ligase is added to both, but one is supplemented with NMN and the other with NAD. In the presence of NAD, ligase joins several oligo(dT) molecules, thus reducing the number of primer sites available to the polymerase, while the NMN-supplemented reaction serves as a control. The difference in dTMP incorporation between the two assays provides a measure of the activity of the ligase. The method is simple, rapid, and sensitive and can be used for the comparison of ligase levels in crude cell extracts or for monitoring ligase activity in the course of the purification of the enzyme.