Structure and Dynamics of Oligonucleotides in the Gas Phase

By combining ion‐mobility mass spectrometry experiments with sub‐millisecond classical and ab initio molecular dynamics we fully characterized, for the first time, the dynamic ensemble of a model nucleic acid in the gas phase under electrospray ionization conditions. The studied oligonucleotide unfolds upon vaporization, loses memory of the solution structure, and explores true gas‐phase conformational space. Contrary to our original expectations, the oligonucleotide shows very rich dynamics in three different timescales (multi‐picosecond, nanosecond, and sub‐millisecond). The shorter timescale dynamics has a quantum mechanical nature and leads to changes in the covalent structure, whereas the other two are of classical origin. Overall, this study suggests that a re‐evaluation on our view of the physics of nucleic acids upon vaporization is needed.     

Synthesis and Structure Elucidation of New Regioisomeric 2‐Alkylamino‐6‐aryl‐8,9‐dihydropyrimido[4,5‐b][1,4]diazepin‐4(7H)‐ones

Novel 2‐Alkylamino‐6‐aryl‐8,9‐dihydropyrimido[4,5‐b][1,4]diazepin‐4(7H)‐ones 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h , 5i , 5j , 5k , 5l , 5m , 5n , 5o were prepared regioselectively by the reaction of 2‐alkylamino‐5,6‐diaminopyrimidin‐4(3H)‐ones 3a , 3b , 3c and dimethylamino propiophenones (Mannich bases) 4a , 4b , 4c , 4d , 4e , 4f . The combination of conventional heating and microwave irradiation approaches provided the possibility of working with both stable and sensitive diaminopyrimidines by controlling parameters such as reaction rates, temperature, and power of irradiation. All products were fully characterized by detailed NMR measurements.     

Steric repulsion as a way to achieve the required stability for the preparation of ionic liquid-based ferrofluids

With this work we would like to emphasize the necessity of steric repulsion to stabilize novel ionic liquid-based ferrofluids. For this purpose, we prepared a suspension of magnetite nanoparticles coated with a double layer of oleic acid, dispersed in 1-ethyl-3-methylimidazolium ethylsulphate ([EMIM][EtSO(4)]). For comparison, a suspension of bare magnetite nanoparticles in [EMIM][EtSO(4)] was also prepared. The stability of these suspensions was checked by magnetic sedimentation and centrifugation processes. Furthermore, their yield stress was measured as a function of the applied magnetic field, which gave additional information on their stability. The results of these experiments showed that the suspension of bare nanoparticles was rather unstable, whereas the suspension of double layer coated nanoparticles gave rise to a true (stable) ferrofluid.     

Effects of local electric fields on the redox free energy of single stranded DNA

Influence of external electric field as well as base substitution effects on the reduction/oxidation free energies of single stranded DNA suggest that base sequencing via measuring redox properties might be feasible under the conditions that (i) a difference of ～ 230 kJ mol(-1) in the oxidation potentials is enough to discriminate between nucleobases conductance signals and (ii) the strand is long enough to reduce end effects.     

Prediction of bond failure and deflection of carbon fiber-reinforced plastic reinforced concrete beams

Carbon fiber-reinforced plastic (CFRP) reinforced concrete beams can fail due to interface debonding, due to the high tensile strength of such rebars. A set of 16 concrete beams reinforced with different amounts of CFRP reinforcement was subject to static three-point bending. The beam dimensions and CFRP reinforcements used were selected to demonstrate a transition from compression failure to bond failure with decreasing reinforcement ratio. It is shown that accurate bond strength data to predict such failures can be obtained from a “hinged-beam” test configuration, rather than the conventional direct “pull-out” tests. Deflection under service loads can also be predicted more accurately using a proposed equation that includes the reinforcement ratio and the elastic modulus of the reinforcement.     

The lattice of subfields of a radical extension

Let x^m ? a be irreducible over F with char $\text{F?m}$ and let α be a root of x^m ? a. The purpose of this paper is to study the lattice of subfields of $\text{F(α)}\text{F}$ and to this end $\text{C(}\text{F(α)}\text{F}\text{, k)}$ is defined to be the number of subfields of F(α) of degree k over $\text{F. C(}\text{F(α)}\text{F}\text{, p}{}^{\mathrm{n}}\text{)}$ is explicitly determined for p a prime and the following structure theorem for the lattice of subfields is proved. Let N be the maximal normal subfield of F(α) over F and set n = |N : F|, then $\text{C(}\text{F(α)}\text{F}\text{, k) = C(}\text{F(α)}\text{F}\text{, (k, n)) = C(}\text{N}\text{F}\text{, (k, n))}$. The irreducible binomials x^s ? b, x^s ? c are said to be equivalent if there exist roots β^s = b, γ^s = a such that F(β) = F(γ). All the mutually inequivalent binomials which have roots in F(α) are determined. Finally these results are applied to the study of normal binomials and those irreducible binomials x^2e ? a which are normal over F (char F ≠ 2) together with their Galois groups are characterized.     

A novel high-spin heterometallic Ni12K4 cluster incorporating large Ni-azide circles and an in situ cyanomethylated di-2-pyridyl ketone

Reaction of di-2-pyridyl ketone (dpk) with nickel acetate and azide in the presence of potassium tert-butylate as a catalytic base generates the title compound, which contains the largest [Ni(mu(1,1)-N3)]6 circles in the discrete ferromagnetically-coupled M(II)-azide cluster family, and shows an unprecedented in situ cyanomethylation of ketone.