Formation of a DNA layer on Langmuir-Blodgett films and its enzymatic digestion

Here, we report a system we have developed where long double-stranded DNAs (dsDNAs) are immobilized on a monolayer of Zn-arachidate. We have applied the Langmuir-Blodgett technique to form the monolayer of Zn-arachidate where Zn(II) is bound to arachidic acid through charge neutralization. Because tetrahedral Zn(II) participates in DNA recognition through coordination, we have been able to layer DNA over the Zn-arachidate monolayer. The DNA layer shows a typical compression and expansion cycle in a concentration-dependent fashion. Interestingly, the DNA monolayer is available for enzymatic degradation by DNaseI. The detection of DNA and its accessibility towards biological reaction is demonstrated by imaging through fluorescence microscopy. The conformation of the DNA, immobilized on the monolayer, was studied with the help of atomic force microscopy (AFM). We observed that the dsDNAs were aligned in a stretched manner on the surface. To investigate further, we also demonstrate here that the small single-stranded DNA (ssDNA) immobilized on the air-water interface can act as a target molecule for the complementary ssDNA present in the subphase. The study of DNA hybridization done with the help of fluorescence spectroscopy clearly supports the AFM characterization.     

Constraints on the squark mass matrix from CP-violation and SUSY predictions for theB^0 - \bar B^0 systems

The parametersc andA of the squark mass matrix, which control flavour violation and left-right maxing respectively, are constrained by fitting ∈ and ∈′. The predictions for mixing and CP-violation in the \(B^0 - \bar B^0 \) system are calculated and then compared with both the predictions of the standard model and the available experimental data.     

Precise measurement of Γ(Λ0 → p + e− + ν)/Γ(Λ0 → p + π−)

Based on a sample of 10 000 events of the decay $\text{Λ}{}^0\text{→ p + e}{}^{\mathrm{?}}\text{+}\text{ν}\text{,}\text{the ratio}\text{Γ(Λ}{}^0\text{→ pe}\text{ν}\text{)/Γ(Λ}{}^0\text{→ pπ}{}^{\mathrm{?}}\text{)}$ is found to be (1.313 ± 0.024) × 10^?3. From this, the absolute rate for the process is calculated to be (3.204 ± 0.068) × 10⁶ s^?1 .     

Charged higgs contributions to rare weak processes in a supergravity model

Charged Higgs contributions to \(Z^0 \to b\bar s + \bar bs\) andb→sγ are examined in a no-scaleN=1 suppergravity model taking into account the constraints typical of the model. Even with these rather restrictive constraints, such contributions can very well dominate over the gluino-induced effects.     

Diastereoselective construction of syn-α-oxyamines via three-component α-oxyaldehyde-dibenzylamine-alkyne coupling reaction: application in the synthesis of (+)-β-conhydrine and its analogues

A Cu(i)-catalyzed α-oxyaldehyde-dibenzylamine-alkyne coupling reaction was delineated for the construction of α-oxyamines with excellent yields and diastereoselectivity. Crystal structure analysis and theoretical calculations were also supportive of the formation of syn-α-oxyamines as the major products. Application of the methodology addresses the synthesis of (+)-β-conhydrine along with analogs having two different diversity features. A ring size variation allows construction of piperidine and pyrrolidine rings while a variation of side arm functionality is achieved by complete regioselective opening of epoxide by different organocopper ylides (Gilman reagents). A lactam-Cu(i) complexation motif is proposed which allows an intramolecular attack of ylides at the terminal epoxy carbon via the six-membered cyclic transition state. The present work features the synthesis of (+)-β-conhydrine over eight steps in 26% yield and its seven analogs in 21-28% yields.     

XAFS investigation of the role of orientational disorder in the stabilization of the ferromagnetic metallic phase in nanoparticles of La(0.5)Ca(0.5)MnO3

The inclusion of the contribution of Jahn-Teller distortion of MnO(6) units, in addition to double-exchange, has been largely successful in explaining the magneto-transport behavior of manganites. However, our recent experiments on La(0.5)Ca(0.5)MnO(3) demonstrated the limitation of these factors in explaining the radical difference between the magneto-transport properties of bulk and nanocrystalline forms. While bulk La(0.5)Ca(0.5)MnO(3) exhibits insulator character (4-300 K) and an anti-ferromagnetic-ferromagnetic transition at 200 K, the nanocrystalline form stabilizes in a metallic ferromagnetic phase (4-300 K). This is counter-intuitive since large Jahn-Teller distortion, which promotes anti-ferromagnetism or insulator character, exists in the nanocrystals too (as indicated by x-ray diffraction results). In this work, we resolve this paradox by considering the role of structural disorder. Employing x-ray absorption spectroscopy, we establish that the disorder in inter-octahedral coupling is enhanced by 57% in the nanocrystals, as the octahedral units are randomly oriented with respect to each other. This orientational disorder promotes metallic ferromagnetism by destroying the stringent orbital ordering that is needed for anti-ferromagnetism and the co-operative nature of the orbital order.