A new class of sulfur‐linked bis‐1,2,3‐selenadiazoles, 1,2,3‐thiadiazoles,and 2H‐diazaphospholes

Novel sulfur‐linked bis‐heterocycles, bis‐1,2,3‐selenadiazoles 4 , 1,2,3‐thiadiazoles 5 , and 2H‐diazaphospholes 7 , were synthesized from bis(2‐oxo‐2‐phenylethanone)sulfide 2 by adopting a simple and well‐versed methodology. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:261–265, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20425     

Studies on the constituents of bocconia cordata. III Structure elucidation of bocconine by means of nuclear magnetic resonance spectroscopic studies

The nmr spectroscopic studies on methoxybocconine are described. The spectral data indicate bocconine to be 2,3,7,8-bis(methylenedioxy)-10-methoxy-5-methylbenzo[c]phenanthridine.     

Structural studies of La \mathsf{_{1-x}}Sr\mathsf{_{x}}MnO \mathsf {_{3 + \delta}} (x = 0.1-1.0)

We report here for the first time (particularly for $x \ge 0.5$ ) a systematic structural study using Rietveld Profile Refinement of powder X-ray diffraction data on the series of polycrystalline compounds La_1-x Sr _x MnO $_{3 + \delta}$ (0.1 ≤ x ≤ 1.0). The iodometric redox titration results show that the compounds $0.1\le x\le 0.4$ and the end compound are oxygen excess and deficient respectively and the compounds in the compositional range 0.5 ≤ x ≤ 0.9 are oxygen stoichiometric within the experimental error. It is found that the structure remains hexagonal until x = 0.4 composition. On further doping, at x = 0.5 composition, a structural transition to orthorhombic phase is observed. Around this composition, very small variations in the Mn-O(2)-Mn and average Mn-Mn bond distances are observed. For above x = 0.5, until x = 0.8 composition, the structure remains orthorhombic with reduced orthorhombic distortion. For the next compound, x = 0.9, a mixed hexagonal and orthorhombic phase is observed where the hexagonal phase is 6 layered with stacking sequence of ABCACB type and the orthorhombic phase is more distorted than that of x = 0.8 composition. The end compound is a four layered hexagonal structure with stacking sequence ABAC type which is more distorted than ABCACB type. As one goes down the series, a decrease in the volume per formula unit and average Mn-O bond distance are observed except at x = 0.9 composition. The observed structural transitions from hexagonal to orthorhombic to layered hexagonal phase can be explained under the electrostatic limit.     

On a Raychaudhuri equation for hot gravitating fluids

We generalise the Raychaudhuri equation for the evolution of a self gravitating fluid to include an Abelian and non-Abelian hybrid magneto fluid at a finite temperature. The aim is to utilise this equation for investigating the dynamics of astrophysical high temperature Abelian and non-Abelian plasmas.      

Phenacylsulfonylacetic acid methyl ester‐synthon for 1,2,3‐selena/thiadiazoles and 2H‐diazaphospholes

A new class of 1,2,3‐selena/thiadiazoles and 2H‐diazaphospholes were synthesized by exploiting α‐ketomethylene group in phenacylsulfonylacetic acid methyl ester.     

Design and characterization of two-dye and three-dye binary fluorescent probes for mRNA detection

We report the design, synthesis, and characterization of binary oligonucleotide probes for mRNA detection. The probes were designed to avoid common problems found in standard binary probes such as direct excitation of the acceptor fluorophore and overlap between the donor and acceptor emission spectra. Two different probes were constructed that contained an array of either two or three dyes and were characterized using steady-state fluorescence spectroscopy, time-resolved fluorescence spectroscopy, and fluorescence depolarization measurements. The three-dye binary probe (BP-3d) consists of a Fam fluorophore which acts as a donor, collecting light and transferring it as energy to Tamra, which subsequently transfers energy to Cy5 when the two probes are hybridized to mRNA. This design allows the use of 488 nm excitation, which avoids the direct excitation of Cy5 and at the same time provides a good fluorescence resonance energy transfer (FRET) efficiency. The two-dye binary probe system (BP-2d) was constructed with Alexa488 and Cy5 fluorophores. Although the overlap between the fluorescence of Alexa488 and the absorption of Cy5 is relatively low, FRET still occurs due to their close physical proximity when the probes are hybridized to mRNA. This framework also decreases the direct excitation of Cy5 and reduces the fluorescence overlap between the donor and the acceptor. Picosecond time-resolved spectroscopy showed a reduction in the fluorescence lifetime of donor fluorophores after the formation of the hybrid between the probes and target mRNA. Interestingly, BP-2d in the presence of mRNA shows a slow rise in the fluorescence decay of Cy5 due to a relatively slow FRET rate, which together with the reduction in the Alexa488 lifetime provides a way to improve the signal to background ratio using time-resolved fluorescence spectra (TRES). In addition, fluorescence depolarization measurements showed complete depolarization of the acceptor dyes (Cy5) for both BP-3d (due to sequential FRET steps) and BP-2d (due to the relatively low FRET rate) in the presence of the mRNA target.     

Utilization of achiral alkenyl amines for the preparation of high affinity Grb2 SH2 domain-binding macrocycles by ring-closing metathesis

A family of previously reported ring-closing metathesis (RCM)-derived macrocycles that exhibit potent Grb2 SH2 domain-binding affinity is characterized by stereoselectively-introduced upper ring junctions that bear bicyclic aryl substituents. However, the synthetic complexity of these macrocycles presents a potential limit to their therapeutic application. Therefore, the current study was undertaken to simplify these macrocycles through the use of achiral 4-pentenylamides as ring-forming components. A series of macrocycles (5a-f) was prepared bearing both open and cyclic constructs at the upper ring junction. The Grb2 SH2 domain-binding affinities of these macrocycles varied, with higher affinities being obtained with cyclo-substituents. The most potent analogue (5d) contained a cyclohexyl group and exhibited Grb2 SH2 domain-binding affinity (K(D) = 1.3 nM) that was nearly equal to the parent macrocycle (2), which bore a stereoselectively-introduced naphthylmethyl substituent at the upper ring junction (K(D) = 0.9 nM). The results of this study advance design considerations that should facilitate the development of Grb2 SH2 domain-binding antagonists.     

Incomplete fusion reactions in 16O+165Ho

Excitation functions for evaporation residues of the system ¹⁶O + ¹⁶⁵Ho have been measured up to 100 MeV. Recoil range distribution of long lived reaction products were measured at ¹⁶O beam energy of 100 MeV. Detailed Monte Carlo simulation of recoil range distributions of products were performed with the help of PACE2 code, in order to extract the contributions of incomplete fusion in the individual channels. The results clearly show the incomplete fusion contributions in the tantalum and thulium products. This is confirmed by the predictions of breakup fusion model of the incomplete fusion.