Palladium-catalyzed selective C–C bond cleavage and stereoselective alkenylation between cyclopropanol and 1,3-diyne: one-step synthesis of diverse conjugated enynes

The stereoselective synthesis of 1,3-enynes from 1,3-diynes is demonstrated by palladium-catalyzed selective C–C bond cleavage of cyclopropanol. Exclusive formation of mono-alkenylated adducts was achieved by eliminating the possibility of di-functionalization with high stereoselectivity. Indeed, this protocol worked very well with electronically and sterically diverse substrates. Several studies, including deuterium labeling experiments and intermolecular competitive experiments, were carried out to understand the mechanistic details. The atomic-level mechanism followed in the catalytic process was also validated using DFT calculations, and the rate-controlling states in the catalytic cycle were identified. Furthermore, preliminary mechanistic investigations with radical scavengers revealed the non-involvement of the radical pathway in this transformation.

Palladium-catalyzed tandem activation and functionalization of readily accessible cyclopropanols have been demonstrated to access valuable conjugated enynes from 1,3-diynes with high stereo-selectivity.     

Urocanic acid photobiology. Photochemical binding to calf thymus DNA

Abstract— Urocanic acid (UA) has previously been shown to photochemically react with N, N-dimethylthymine and with phage G4 single-stranded DNA. In this study, E-[ring-2-¹⁴C]-U A and calf thymus DNA have been irradiated with UV light (Λ > 270 nm) in buffered, aqueous solutions. Rc-isolation of the DNA indicates covalent binding of UA at levels of up to 80 nmol UA/mg DNA. Binding is observed for both native and heat denatured DNA. Equilibrium dialysis studies give no evidence for complexation of UA to either form of DNA in the dark. Enzymatic cleavage of the UA bound DNA and analysis by HPLC shows peaks for ^l4C-labelled products with retention volumes identical to those of a marker mixture prepared by irradiating UA with [³H-methyl]thymidine. Photolysis of the DNA before irradiation with U A leads to the formation of a second product with a retention volume corresponding to that for a deoxyadenosine/UA marker.     

X-band e.p.r. spectra of mixed-ligand copper(II) complexes

E.p.r. spectra of [Cu(et2dtc)2], Na[Cu(asp/glut)(et2dtc)] and Na2[Cu(asp/glut)(et2dtc)2] in the polycrystalline state have been recorded and discussed. The complexes display an antiferromagnetic exchange interaction, increasing in the order: Na2[Cu(asp/glut)(et2dtc)2] < Na[Cu(asp/glut)(et2dtc)] < [Cu(et2dtc)2] This revised version was published online in June 2006 with corrections to the Cover Date.     

Correlation between Site ll-Specific Human Serum Albumin (HSA) Binding Affinity and Murine in vivo Photosensitizing Efficacy of Some Photofrin Components

Human serum albumin (HSA) is one of the key components in human blood that may influence drug distribution. As such, it is important to know the affinity of any drug for albumin. Previously, Photofrina mixture of monomeric, dimeric and oligomeric porphyrins, has been subjected to HSA binding studies. However, due to its complex nature, binding studies on Photofrin or other hematoporphyrin derivatives with HSA are inconclusive. In this report, the binding properties of some components (dimers and trimers) of Photofrin® and the relationship between murine photosensitizing efficacy and those binding properties were investigated. The interaction of these porphyrins with HSA was investigated by direct ultrafiltration and fluorescent titration techniques with fluorescent probes such as dansyl-L-proline (DP), which is known to interact selectively with site II on HSA. Porphyrins also were tested for antitumor activity in a mouse model following intravenous administration and exposure to laser light. Together, the results suggest that the photosensitizers that were preferentially bound to site II of HSA were most effective at controlling murine tumor regrowth     

UVB-induced photodamage to phycobilisomes of Synechococcus sp. PCC 7942

The effect of UVB irradiation on the phycobilisomes (PBSs) of Synechococcus sp. PCC 7942 cells was studied. The sucrose density-gradient-isolated PBSs from in vivo UVB-treated (280–320 nm) cells showed a strong decrease in β-phycocyanin (βPC) and -phycocyanin (PC) polypeptides. In addition to a decrease in the linker polypeptides LCM 75 (linker connecting the core to the thylakoid membranes), LR 33 (linker in the rod structure), LRC 31.5 (linker connecting the rod to the core) and LRC 29. In vitro UVB treatment of gradient-isolated intact PBSs for 1 h had no effect on any of the constituent polypeptides, and only after 2 h was a degradation of LCM 75 and LR 33 and a decrease in βPC evident. Further investigation of phycobiliproteins (4 h of UVB irradiation) using polyclonal antibody directed against purified whole PBSs revealed that, in vivo, there was a gradual decline in the levels of LCM 75, LR 33, LRC 31.5, LRC 29, βPC and PC.     

Computational Design of Novel Allosteric Inhibitors for Plasmodium falciparum DegP

The serine protease, DegP exhibits proteolytic and chaperone activities, essential for cellular protein quality control and normal cell development in eukaryotes. The P. falciparum DegP is essential for the parasite survival and required to combat the oscillating thermal stress conditions during the infection, protein quality checks and protein homeostasis in the extra-cytoplasmic compartments, thereby establishing it as a potential target for drug development against malaria. Previous studies have shown that diisopropyl fluorophosphate (DFP) and the peptide SPMFKGV inhibit E. coli DegP protease activity. To identify novel potential inhibitors specific to PfDegP allosteric and the catalytic binding sites, we performed a high throughput in silico screening using Malaria Box, Pathogen Box, Maybridge library, ChEMBL library and the library of FDA approved compounds. The screening helped identify five best binders that showed high affinity to PfDegP allosteric (T0873, T2823, T2801, {"type":"entrez-protein","attrs":{"text":"RJC02337","term_id":"1480409465","term_text":"RJC02337"}}RJC02337, CD00811) and the catalytic binding site (T0078L, T1524, T2328, BTB11534 and 552691). Further, molecular dynamics simulation analysis revealed {"type":"entrez-protein","attrs":{"text":"RJC02337","term_id":"1480409465","term_text":"RJC02337"}}RJC02337, BTB11534 as the best hits forming a stable complex. WaterMap and electrostatic complementarity were used to evaluate the novel bio-isosteric chemotypes of {"type":"entrez-protein","attrs":{"text":"RJC02337","term_id":"1480409465","term_text":"RJC02337"}}RJC02337, that led to the identification of 231 chemotypes that exhibited better binding affinity. Further analysis of the top 5 chemotypes, based on better binding affinity, revealed that the addition of electron donors like nitrogen and sulphur to the side chains of butanoate group are more favoured than the backbone of butanoate group. In a nutshell, the present study helps identify novel, potent and Plasmodium specific inhibitors, using high throughput in silico screening and bio-isosteric replacement, which may be experimentally validated.     

Solid-state fermentation for production of phytase by Rhizopus oligosporus

Solid-state fermentation of coconut oil cake has been carried out with Rhizopus oligosporus for the production of phytase. Phytase is used commercially in the animal feed industry to improve animal performance because there is a substantial and growing interest among swine and poultry producers in the application of phytase to improve the nutritional quality in animal feeds. Demonstrated benefits include improved feed yield ratios and reduction in the environmental costs associated with the disposal of animal wastes. We report the production of extracellular phytase by R. oligosporus under solid-state fermentation using coconut oil cake as substrate. Maximal enzyme production (14.29 U/g of dry substrate) occurred at pH 5.3, 30°C, and 54.5% moisture content after 96 h of incubation. The addition of extra nutrients to the substrate resulted in inhibition of product formation. The results indicate the scope for production of phytase using coconut oil cake as solid substrate without additional nutrients.     

Vibrational spectra of 2 (3H) benzofuranone studied by Raman,IR spectroscopy and AM1 semiempirical molecular orbital calculations

Raman spectra of 2 (3H) benzofuranone have been recorded in the region 400-3200 cm(-1) and the IR spectra have been recorded in the region 200-4000 cm(-1). Vibrational frequencies for the fundamental modes of this bicyclic heteroatomic molecule have also been calculated using Austin method 1 (AM1) semiempirical molecular orbital method. Vibrational assignments have been made for the fundamental modes and the observed combination and overtone bands are also assigned. A splitting in the carbonyl group (C=O stretching) frequency observed at 1640-1660 cm(-1) in both Raman and IR spectra, is explained as Fermi-resonance. Net atomic charges for each atom of this molecule along with its heat of formation were also calculated. It is evident from the calculations that the 2 (3H) benzofuranone is more stable than the 3 (2H) benzofuranone in contrast to earlier estimates.     

Unique role of hydrophilic ionic liquid in modifying properties of aqueous Triton X-100

Modification of important physicochemical properties of aqueous surfactant solutions can be achieved by addition of environmentally benign room temperature ionic liquids (ILs). While low aqueous solubility of "hydrophobic" ILs limits the amount of IL that may be added to achieve desired changes in the physicochemical properties, hydrophilic ILs do not have such restrictions associated to them. Alterations in the key physicochemical properties of aqueous solutions of a common nonionic surfactant Triton X-100 (TX100) on addition of up to 30 wt % hydrophilic IL 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) are reported. The presence of micellar aggregates in as high as 30 wt % [bmim][BF4]-added aqueous TX100 solutions is established by dynamic light scattering and fluorescence probe behavior. Increasing the concentration of [bmim][BF4] results in decrease in average micellar size and aggregation number and increase in critical micelle concentration, indicating an overall unfavorable aggregation process. Increase in the dipolarity and the microfluidity of the probe cybotactic region within the palisade layer of the micellar phase upon [bmim][BF4] addition implies increased water penetration and the possibility of TX100-[bmim][BF4] interactions. While the changes in some of the physicochemical properties indicate the role of [bmim][BF4] to be similar to a cosurfactant, the IL acts like a cosolvent as far as changes in other properties are concerned. Effectiveness of IL [bmim][BF4] in modifying physicochemical properties of aqueous TX100 is demonstrated.