Synthesis, gene silencing, and molecular modeling studies of 4'-C-aminomethyl-2'-O-methyl modified small interfering RNAs

The linear syntheses of 4'-C-aminomethyl-2'-O-methyl uridine and cytidine nucleoside phosphoramidites were achieved using glucose as the starting material. The modified RNA building blocks were incorporated into small interfering RNAs (siRNAs) by employing solid phase RNA synthesis. Thermal melting studies showed that the modified siRNA duplexes exhibited slightly lower T(m) (～1 °C/modification) compared to the unmodified duplex. Molecular dynamics simulations revealed that the 4'-C-aminomethyl-2'-O-methyl modified nucleotides adopt South-type conformation in a siRNA duplex, thereby altering the stacking and hydrogen-bonding interactions. These modified siRNAs were also evaluated for their gene silencing efficiency in HeLa cells using a luciferase-based reporter assay. The results indicate that the modifications are well tolerated in various positions of the passenger strand and at the 3' end of the guide strand but are less tolerated in the seed region of the guide strand. The modified siRNAs exhibited prolonged stability in human serum compared to unmodified siRNA. This work has implications for the use of 4'-C-aminomethyl-2'-O-methyl modified nucleotides to overcome some of the challenges associated with the therapeutic utilities of siRNAs.     

Thermally reversing window in Ge15Te85 − xInx glasses: Nanoindentation and micro-Raman studies

Nanoindentation studies on Ge₁₅Te_85 ? xIn_x glasses indicate that the hardness and elastic modulus of these glasses increase with indium concentration. While a pronounced plateau is seen in the elastic modulus in the composition range 3 ≤ x ≤ 7, the hardness exhibits a change in slope at compositions x = 3 and x = 7. Also, the density exhibits a broad maximum in this composition range. The observed changes in the mechanical properties and density are clearly associated with the thermally reversing window in Ge₁₅Te_85 ? xIn_x glasses in the composition range 3 ≤ x ≤ 7. In addition, a local minimum is seen in density and hardness around x = 9, the chemical threshold of the system. Further, micro-Raman studies reveal that as-quenched Ge₁₅Te_85 ? xIn_x samples exhibit two prominent peaks, at 123 cm^? 1 and 155 cm^? 1. In thermally annealed samples, the peaks at 120 cm^? 1 and 140 cm^? 1, which are due to crystalline Te, emerge as the strongest peaks. The Raman spectra of polished samples are similar to those of annealed samples, with strong peaks at 123 cm^? 1 and 141 cm^? 1. The spectra of lightly polished samples outside the thermally reversing window resemble those of thermally annealed samples; however, the spectra of glasses with compositions in the thermally reversing window resemble those of as-quenched samples. This observation confirms the earlier idea that compositions in the thermally reversing window are non-aging and are more stable.     

B-Alkylation and Arylation of [(η5-C5Me5Mo)2B5H9]: Synthesis and Characterization of Isomeric [(η5-C5Me5Mo)2B5H9-nRn] (When R = n-Bu, n = 2, 1; R = Ph, n = 2, 1)

Abstract  Reaction of [(η⁵-C₅Me₅Mo)₂B₅H₉], 1 with 5-fold excess of n-BuLi at −70 °C followed by excess of RI (R = n-Bu or Ph) at room temperature yielded B-R inserted metallaboranes [(η⁵-C₅Me₅Mo)₂B₅H₈R] (2: R = n-Bu, 5: R = Ph), [(η⁵-C₅Me₅Mo)₂B₅H₇R₂] (3, 4: R = n-Bu; 6, 7: R = Ph). Isolated yields of mono-alkyl/arylated species are better than di-alkyl/arylated ones. All the new cluster compounds have been characterized by IR, ¹H, ¹¹B, ¹³C NMR and mass spectroscopy as simple substitution derivatives of [(η⁵-C₅Me₅Mo)₂B₅H₉] and the structural types of one of these species, 2 was established by X-ray crystallographic analysis. Graphical Abstract  Reaction of [(η⁵-C₅Me₅Mo)₂B₅H₉], with 5-fold excess of n-BuLi at −70 °C followed by excess of RI (R = n-Bu or Ph) at room temperature yielded B-R inserted metallaboranes [(η⁵-C₅Me₅Mo)₂B₅H_9-nR_n] (When R = n-Bu, n = 2, 1; R = Ph, n = 2, 1).      

Comprehensive Lichenometabolomic Exploration of Ramalina conduplicans Vain Using UPLC-Q-ToF-MS/MS: An Identification of Free Radical Scavenging and Anti-Hyperglycemic Constituents

In this study, we propose ultra-performance liquid chromatography coupled with quadrupole/time-of-flight mass spectrometry (UPLC-QToF-MS/MS)-guided metabolite isolation as a choice analytical approach to the ongoing structure–activity investigations of chemical isolates from the edible lichen, Ramalina conduplicans Vain. This strategy led to the isolation and identification of a new depside (5) along with 13 known compounds (1–4, 6–14), most of which being newly described in this lichen species. The structures of the isolates were established by detailed analysis of their spectral data (IR, NMR, and Mass). The acetone extract was further analyzed by UPLC-Q-ToF-MS/MS in a negative ionization mode, which facilitated the identification and confirmation of 18 compounds based on their fragmentation patterns. The antioxidant capacities of the lichen acetone extract (AE) and isolates were measured by tracking DPPH and ABTS free radical scavenging activities. Most isolates displayed marked radical scavenging activities against ABTS while moderate activities were observed against DPPH radical scavenging. Except for atranol (14), oxidative DNA damage was limited by all the tested compounds, with a marked protection for the novel isolated compound (5), as previously noted for the acetone extract (p < 0.001). Furthermore, compound (4) and acetone extract (AE) have inhibited intestinal α-glucosidase enzyme significantly (p < 0.01). Although some phytochemical studies were already performed on this lichen, this study provided new insights into the isolation and identification of bioactive compounds, illustrating interest in future novel analytical techniques.     

Correction to: Effect of heating rate on structure,morphology and photocatalytic properties of TiO2 particles: thermal kinetic and thermodynamic studies

Journal of Sol-Gel Science and Technology -     

Seasonal variation of uranium and physico-chemical parameters in spring water sources of Pithoragarh city,Uttarakhand, India

Journal of Radioanalytical and Nuclear Chemistry - The paper deals with the seasonal variation of physico-chemical parameters in natural spring water sources collected from Pithoragarh city,...     

Solution Processing of Topochemically Converted Layered WO3 for Multifunctional Applications

Solution processing of nanomaterials is a promising technique for use in various applications owing to its simplicity and scalability. However, the studies on liquid-phase exfoliation (LPE) of tungsten oxide (WO₃) are limited, unlike others, by a lack of commercial availability of bulk WO₃ with layered structures. Herein, a one-step topochemical synthesis approach to obtain bulk layered WO₃ from commercially available layered tungsten disulfide (WS₂) by optimizing various parameters like reaction time and temperature is reported. Detailed microscopic and spectroscopic techniques confirmed the conversion process. Further, LPE was carried out on topochemically converted bulk layered WO₃ in 22 different solvents; among the solvents studied, the propan-2-ol/water (1 : 1) co-solvent system appeared to be the best. This indicates that the possible values of surface tension and Hansen solubility parameters for bulk WO₃ could be close to that of the co-solvent system. The obtained WO₃ dispersions in a low-boiling-point solvent enable thin films of various thickness to be fabricated by using spray coating. The obtained thin films were used as active materials in supercapacitors without any conductive additives/binders and exhibited an areal capacitance of 31.7 mF cm⁻² at 5 mV s⁻¹. Photo-electrochemical measurements revealed that these thin films can also be used as photoanodes for photo-electrochemical water oxidation.